Keywords: indigenous peoples, UNDRIP, education, natural resources, globalisation

The UN Declaration on the Rights of Indigenous Peoples (2007) marks a significant shift in the relations whereby indigenous peoples define themselves and their claims. They are now faced with the challenge of implementing international standards within national spaces. By adopting a global comparative perspective, our article aims to explore how this movement unfolds in a variety of local issues and strategies, building transnational links and differences. We first examine the acceptance of indigenous peoples' status across the globe before exploring the transformative effects of recognition around two major themes, indigenous rights to education and to land and natural resources. We argue that the recognition of indigenous peoples as subjects of international law has far-ranging implications for the global system as a whole, implicating other global or transnational agents, and potentially affecting the balance between economic and political powers.

"Emerging issues in indigenous rights: transformative effects of the recognition of indigenous peoples" (1)

The adoption of the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) by the General Assembly in 2007 has been the culmination of 25 years of negotiation within the UN system between states and indigenous peoples' representatives (2). It empowers indigenous peoples' representatives with new arguments to oppose detrimental state and corporate policies. Now the onus is on both parties to bring back the minimum standards set in the Declaration to implement effective change to the dire social, economic and political conditions of indigenous peoples in national spaces. This situation brings about new issues as international law needs to be translated into domestic law and policy to be of any efficiency beyond symbolic assertions. This article examines how the recognition of indigenous peoples under international law transforms the relational field in which their claims are asserted and negotiated, focusing on the construction of rights as a means to sustain self-determined indigenous futures. Doing so, we seek to contribute to our understanding of issues surrounding indigenous rights, their implementation, and the underlying political, economic and anthropological dynamics at work. We address the transformative power of the emergence of a new subject under international law, indigenous peoples, and how this feeds into localised struggles for autonomy, self-determination and the overcoming of poverty. First, we examine how the recognition of indigenous peoples status is accepted across the globe in order to outline different dynamics of indigenous human rights across states and continents. We then focus first on indigenous rights to education, then on indigenous rights to land and natural resources. We seek to bring forth the major tensions and issues that have become critical in a context where the implementation of indigenous human rights is not solely constrained by state policy and national constructs but also by the very global forces and dynamics that indigenous peoples have sought to harness, which participate in redefining the contours of state sovereignty.

Throughout the paper we mostly use Latin American and Australian examples because they represent qualitatively distinctive configurations and because the distance and similarities between these rarely compared regions highlight tensions, conflicts and issues that cut across indigenous situations worldwide. It is in this dynamic of juxtaposition and comparison that we find means to confront a global issue and think of its localised manifestations, thus offering an analysis of the relational situation engaged by UNDRIP.

Indigenous rights in a global perspective

The right of peoples The recognition of indigenous peoples, whose autonomy is contested in most parts of the world, is pursued by the international adoption of UNDRIP (2007) which acknowledges their human individual and collective rights. The Declaration does not specify a definition of these peoples. States retain their sovereignty and territorial integrity, which legitimates them as political actors internationally. But a new category of political actors, having emerged during the last quarter of the twentieth century, now has the capacity to influence governance processes and structures in matters that affect them. A new relational and political dynamic is engaged with the second paragraph of the UNDRIP Preamble: 'Affirming that indigenous peoples are equal to all other peoples, while recognizing the right of all peoples to be different, to consider themselves different, and to be respected as such. ' The negotiation of the UNDRIP was based on the principle that indigenous peoples are peoples, collectively pursuing to live according to their own institutions, rather than a second-class category of citizens or a series of distinct populations. Indigenous leaders and lawyers repeatedly pointed out the differences that had to be addressed by the international community, between individual human rights, which apply to everyone, and collective human rights, which apply to situations indigenous peoples claim as characterising them. As a people and a group of indigenous peoples, they express at global levels their perception that their cultures, languages, forms of governance, systems of law and justice, etc., constitute an integral part of their identification and the source of their differentiation, not as ethnic groups seeking the implementation of minority policies, but as subjects of law capable of articulating alternative modes of relationship to the rest of world as well as alternative modes of development. The adoption of UNDRIP has a symbolic, yet powerful, effect as indigenous peoples acquire, with this instrument, the legal personality they need to be respected by states and within states. However, the exercise of indigenous peoples' foundational right to self-determination (UNDRIP art. 3) remains to be precisely addressed through the evolution of domestic policies and in the larger context of globalisation.

A global overview

With 15 states having ratified the International Labour Organisation (ILO) Convention 169 (1989)(3), active involvement in the UNDRIP process, and other institutional arrangements such as the Organization of American States (where a similar exercise as the UNDRIP is progressing) and the Inter-American Court of Justice (which hears indigenous cases), Central and South America potentially have an impact on indigenous issues developments worldwide (4). Indeed, three cycles of constitutional changes (between 1985 and 2009) led to important steps for the inclusion of indigenous peoples (5): first, the emergence of multiculturalism and the right to cultural diversity (1982-1988 -Guatemala, Nicaragua, Brazil); secondly, the emergence of the concept of a pluricultural nation-state and the recognition of legal pluralism (1989-2005 -Argentina, Columbia, Ecuador, Mexico, Panama, Paraguay, Peru, Venezuela); lastly, the formation of a plurinational state, including in its formation and apparatus indigenous nations and nationalities (since 2006) whose best expression is now given by Bolivia and Ecuador [START_REF] Yrigoyen | Pueblos Indı´genas. Constitutiones y reformas politicas en Ame´rica Latina[END_REF]. Constitutional changes allowed for a fruitful germination of ideas and new practices, including: addressing land conflicts (with policies of territorial demarcation), opening the education system through bilingual education, adjusting systems of justice through decentralisation and the territorial recognition of indigenous sovereignties, with various forms of autonomies. Other countries -Chile, Honduras, Guyana, El Salvador, Costa Rica, Surinam, Belize -have passed indigenous laws, most of which are concerned with linguistic and cultural heritage protection. Although southern American states do not oppose the notion of collective human rights and recognise indigenous groups as peoples or nations, the implementation of UNDRIP locally remains highly controversial.

African and Asian states offer a very contrasted picture, as indigeneity there confronts conceptions of autochthony to the point that, during the 25 years of the UNDRIP negotiation, they were quite absent. In their views, there were no indigenous issues since all African and Asian nationals were to be considered autochthonous to the place they live in. In Africa, indigenous peoples' organisations joined the international movement in the late 1990s. They have been supported by United Nations (UN) agencies and benefited from a series of changes at international levels with the formulation of indigenous policies within the UN system (UN Development Programme and Environment Programme, UN Educational, Scientific and Cultural Organisation, the World Bank, and so on). At the turn of the century, the African Commission of the Peoples and Human Rights set up a working group to identify which people were to be considered relevant for the UN approach of indigenous peoples' rights. They identified such groups with regard to processes of nomination, racial discrimination, living conditions, and sources of economic subsistence, rather than anteriority of territorial occupation [START_REF]African Commission on Human and People's Rights, Advisory Opinion of the African Commission on Human and People's Rights on the United Nations Declaration on the Rights of Indigenous Peoples (Banjul: ACHPR[END_REF]. In 2006-2007, indigenous peoples and human rights organisations developed an active lobby to override the blockage of the African group at the General Assembly, explaining that UNDRIP does not create new rights but incorporates in a single document a set of international human rights provisions that they had already adopted (such as the 1966 International Covenants or the Convention on the Elimination of all forms of Racial Discrimination). This strategy allowed for the final adoption of UNDRIP in 2007 and, recently, for the ratification of ILO Convention 169 by the Republic of Central Africa (the first and unique African country to do so) [START_REF]Some states abstained from voting the UNDRIP (Kenya and Nigeria), others being absentees (Chad, Ivory Coast, Equatorial Guinea, Eritrea, Ethiopia, Gambia, Guinea-Bissau, Mauritania, Morocco[END_REF]. Limited constitutional and legal changes have occurred: in Burundi, the 2005 constitutional reform established three reserved seats for the Batwa in both parliament chambers; in the Congo Republic, a law on the promotion and protection of indigenous peoples' rights was adopted in February 2011.

In Asia, there is no international Human Rights Commission that could have created a particular working group for steering a political reflection on indigenous issues. However, no state of that region opposed the UNDRIP -even China, India and Indonesia voted yesmostly on the basis that they already have active policies towards 'their' indigenous minorities, defined according to official State discourses as 'national minorities' (China and Viet Nam), 'racial minorities' or 'national races' (Burma), or 'scheduled tribes' (India). Evolutions are happening in two countries as a result of indigenous peoples' mobilisations and the lobbying of the state (Philippines) or of revolutionary changes (Nepal). The former adopted an indigenous law very close to UNDRIP, while the latter has recently ratified ILO Convention 169 (the first and unique Asian country to do so). The adoption of an indigenous law did not prevent the Philippines, however, from adopting a contradictory mining law.

In the Pacific region, the situation is quite complex as four states, that have actively opposed UN indigenous developments, have a leading influence on the region: Australia, New Zealand, the US (Hawai'i), and France (New Caledonia and Polynesia). The recent shift of the CANZUS group which announced support for the Declaration in the past two years reflects their 'over-compliant' position whereby they promote linguistic and cultural rights while resisting more politically challenging ones (e.g. self-determination and land rights) [START_REF] Lightfoot | Emerging International Indigenous Rights Norms and "Over-Compliance" in New Zealand and Canada[END_REF].

France does not support the concept of indigenous peoples (except for the Kanak people who are engaged through the Noumea Agreement in a process of decolonisation enabled by the concept of 'shared sovereignty'). It supports the UNDRIP with an understanding that the Republic has overseas 'domestic' policies which address Indigenous Peoples situations. Regionally, a wider European paradigm of recognition dominates, which mostly relies on the Framework Convention for the Protection of National Minorities, with no provisions for collective political and human rights to address indigenous issues [START_REF] Grote | On the Fringes of Europe: Europe's Largely Forgotten Indigenous Peoples[END_REF]. The sole exception are the Saami people who enjoy political rights (with the recognition of Saami Parliaments in three countries) but still look forward to the adoption of the Nordic Saami Convention by Norway, Finland and Sweden. The adoption of the European Initiative for Democracy and Human Rights by the European Union -an instrument which includes some provisions for indigenous peoples' human rights in third countries -signals however some interest in indigenous issues as understood within the UN system.

In sum, many gaps can be observed between national and legal contexts regarding indigenous lives, across and within countries. The 'indigenous experience today' is well differentiated, particularly if one contrasts local and global sites, places of residence and places of political action [START_REF]Indigenous Experience Today[END_REF]. Nonetheless, significant shifts can be observed: at global levels with the internationalisation of indigenous movements and the mainstreaming of indigenous issues in the fabric of international norms; in the academic world through the work of indigenous studies departments in Anglo-Saxon and Latin American universities (including indigenous universities in South America) and, more recently, in Northern Europe (Norway), which re-examine the meanings of indigeneity and of ethnic/ethic politics; and in the world of politics where indigenous peoples can now be considered, in some places, as subjects of rights rather than subjugated by laws. However, indigenous people, who in some states participated actively to the writing of new constitutions, remain under pressure, especially for their models of relationship to their land and territories: the condition of urban indigenous peoples and the situation of indigenous migrants emerge as issues of particular concern and, even more critically, the capacity to secure access and title to a land held as a collective resource, for the wellbeing of all those attached to it.

In the remainder of this article we examine two key areas of indigenous peoples' rights struggles -education and control of resources -, examining how the UNDRIP and other international instruments and developments come to bear on these issues. Indigenous rights to education, language and culture: the future of diversity

Tensions within recognition

Education and associated issues of language and culture are core interests of nationstates and indigenous peoples as both seek to protect their collective specificities as societies. While culturally adapted education is central for sustaining autonomous and selfdetermining indigenous groups, education has historically been for states the privileged means to shape national communities. This is why specific collective rights were to be recognised: to ensure the survival of indigenous peoples as human groups. These present indigenous rights to education as a necessary although insufficient condition for both selfdetermination and sustainable development. Article 13 of the UNDRIP [START_REF]protected and also to ensure that indigenous peoples can understand and be understood in political[END_REF] provides with a general recognition and protection of indigenous rights to their lore and culture, while article 14 [START_REF]Indigenous peoples have the right to establish their educational systems and institutions providing education in their own language, in a manner appropriate to their cultural methods of teaching and learning; 2. Indigenous individuals, particularly children, have the right to all levels of education of the State without discrimination[END_REF] affirms the right for Indigenous Peoples to control their educational systems and institutions, and article 15.1 [START_REF]Indigenous peoples have the right to the dignity and diversity of their cultures, traditions, histories and aspirations which shall be appropriately reflected in education and public information[END_REF] proposes to articulate indigenous peoples' cultures and knowledge with mainstream education. Other provisions in the Declaration, in the Preamble and article 8 for instance, explicitly link indigenous rights to education, language and culture to their rights over their lands and resources and sustainable development (that is, to ecological and economic dimensions). Indeed, indigenous education cannot be considered separately from what makes indigenous lives possible, that is a holistic societal perspective integrated through networks of relationships -to land, kin, ancestors and spiritual beingsthat have to be maintained.

Education for indigenous peoples cannot simply be addressed as education in a particular language but engages a particular work in didactic and pedagogy, done in association with well trained people, to use education as a tool for the development of the child in relation to those systems of relationships. This dimension creates a particular tension for those indigenous people who live outside of their territory which explains why indigenous rights to education, as they appear in the UNDRIP, maintain a fundamental tension, touching at the core of indigenous peoples' relationships to the state. Namely, indigenous peoples' rights to education are at odds with the general human right to education as the latter does not strictly equate with indigenous peoples' understanding of education in their language and culture and according to their specific values and practices. The very article in the Declaration that purports to protect indigenous peoples' right to their educational institutions (art. 14) actually entrenches this tension that is played out across political, cultural and socio-economic fields within national spaces. At stake here is the nature, content and purpose of an indigenous education.

Conflicting purposes

The indigenous experience of colonial and, later, state education, has overwhelmingly been one of assimilation at the hands of religious or state representatives, sometimes through massive displacement as in Australia and Canada [START_REF]Human Rights and Equal Opportunity Commission, Bringing Them Home: Report of the National Inquiry into the Separation of Aboriginal and Torres Strait Islander Children from Their Families[END_REF]. The indigenous critique of such policies is reflected in the Amerindian saying that the purpose of the white school is 'to educate the man and leave the Indian out'. Contemporary policies, which focus on 'closing the gap' in educational achievements, seek to bring indigenous people to the same standard as the rest of the national population. They remain assimilationist in purpose and nature as opposed to policies that would develop from indigenous knowledge, experiences and perspectives [START_REF]The State of Aboriginal Learning in Canada: A Holistic Approach to Measuring Success[END_REF]. The historical processes of dispossession and exclusion of indigenous peoples resulting from colonisation and nation-state formation have for the most part installed them in situations of entrenched poverty and sociopolitical exclusion. Today, this very situation forms the ground on which states, as well as international organisations and institutions, argue for the necessity for indigenous peoples to wholly integrate the mainstream economy and, hence, participate in the mainstream education system. In Australia, for instance, the contestation and reduction of bilingual programmes within indigenous communities by governments was justified on the grounds that education in indigenous language in remote communities prevented economic integration -despite numerous studies showing that indigenous children benefiting from two-way models of education did perform better, including in English proficiency [START_REF]Northern Territory, Indigenous Languages and Culture in Northern Territory Schools; Report 2004-2005[END_REF].

Two interrelated issues are at stake here that are transversal to the indigenous world. First, there is a continuing problem with the lack of access to the general education system for indigenous people, particularly for those who chose to live in communities away from the main job markets and where, furthermore, the training and recruitment of cross-culturally trained teachers is highly difficult. Generally speaking, if indigenous people want to achieve high education levels they have no choice but to move away from their communities, kin networks and country, a highly problematic situation since the breakdown of social cohesion lies at the heart of many social and economic problems faced by indigenous people. Secondly, indigenous knowledge is rarely seen as an asset, either for the children, or for the development of sustainable or 'hybrid' economies where the traditional, market and state sectors are articulated at parity [START_REF] Altman | Sustainable Development Options on Aboriginal Land: The Hybrid Economy in the Twenty-first Century[END_REF]. This generally results in poor integration of indigenous concerns within education systems, a situation reflected in multiple ways, including: the segmentation of holistic knowledge requiring ongoing relationships with land and kin; the problematic displacement of 'traditional practices' to the school room; and the difficult accommodation of indigenous linguistic and cultural diversity, even in pluricultural situations, multicultural education being often merely a gloss for a dual education system where indigenous children are taught the mainstream language and culture.

In the light of UNDRIP, indigenous rights to education imply political processes of decentralisation and increased local control in order to encompass the diversity of indigenous peoples' languages and cultures and accommodate their teaching ways. Achieving indigenous peoples' control over their education not only requires a transformation of their relationship to the state but also of educational institutions themselves.

Decentralising indigenous education

To a large extent, indigenous peoples' capacity to sustain their specific educative institutions, systems of knowledge and languages has depended on the reach and orientation of (colonial and post-colonial) states, and now also of globalised economic actors. When considering indigenous rights to education, it appears that the institutional conditions for implementing these rights are linked to indigenous relationships to the state according to different variables. These include: the nature of the relationship to the state (formal/informal); the degree and nature of political integration to the nation-state (national, multicultural, plurinational); the indigenous proportion of the national population; and the state's capacity of governance (weight of international cooperation and transnational companies).

In Bolivia, where the UNDRIP has been integrated to the Constitution and ILO 169 has been ratified, indigenous people benefit from a range of educative possibilities integrating their languages and cultures up to the university level whereas in Australia -where no formal relationship links the diverse indigenous polity to the federal state (whether in a treaty or in the constitution) and where indigenous rights have limited legal recognition -while indigenous educational achievements have risen over the last decades and specific departments established in universities, the participation of indigenous people to the design and orientation of education remains marginal at best. The constitutions of 11 Latin American countries (Argentina, Bolivia, Brazil, Colombia, Ecuador, Guatemala, Mexico, Nicaragua, Paraguay, Peru and Venezuela) acknowledge multicultural or multinational characteristics of the state, while a few others (such as Chile, El Salvador, Honduras and Panama´), with legal yet no constitutional provisions for indigenous peoples, accept the right to differential education. Multiple experiences of indigenous education have been developed since the 1980s -from local autonomy to indigenous universities and, in the wake of postcolonial and decolonisation studies, proposals for a 'pluriversity' [START_REF] Rhoads | The University, State and Market, the Political Economy of Globalization in the America[END_REF] -which highlight the difficulties of implementing an agenda of decentralised education institutions.

Several problems pave the process of decentralisation and the creation of 'third sector' indigenous entities in charge of providing education as well as health services to their affiliated members. Some case studies demonstrate the crucial importance of the definition of the territorial frame of reference as well as the financial issue: what kind of budget is allocated to education and who is going to pay for indigenous children? In that domain, a top-down approach of decentralisation towards indigenous peoples without the corresponding financial transfer proves to be highly problematic, notwithstanding the problems raised by the difficulty for training the professors and establishing some kind of standards [START_REF] Baronnet | Los pueblos indı´genas de Colombia frente a los servicios pu´blicos de salud y educacion: Las experiencias de gestion propia de la politica social[END_REF]. Moreover, the use of neo-liberal forms of contractualisation may induce dramatic errors, such as for the Awa people in Colombia, a group of hunter-gatherers living in the Amazon forest. The Awa sent their proposal (a day after the deadline because the road was flooded) and the British Musical College won the call for tender explaining that English and music were two universal languages, that would well equip indigenous students for the job market. The Awa teachers being fired, a source of jobs was also lost, and Awa parents went on strike for a year before a solution was found. In many parts of the world, indigenous peoples have often little choice but to go to the independent or private sector if they want some degree of control over their educational institutions, contents and practices. Generally this is done with assistance from philanthropic and religious groups, which raises another significant set of issues regarding self-determination.

As under neo-liberal reforms education ceases to be institutionally treated as a public good the position of indigenous peoples seeking to maintain their singularities becomes strategic. Our discussion of indigenous rights to education in the wake of the UNDRIP has highlighted two significant factors bearing on the implementation of these rights: not only the relationship to the state -the traditional framework of analysis for Indigenous situationsbut also the growing importance of an autonomous economic base as a condition for the realisation of self-determination in the globalised economy. We take these issues further in discussing indigenous peoples' rights over their land and natural resources.

Negotiating sovereignties: indigenous rights over land and natural resources

Indigenous permanent sovereignty over land and natural resources Relationships to land are foundational of indigenous polities and also of their modern political struggles as colonial and state powers have been built, politically and economically, on the dispossession of indigenous peoples' territorial sovereignty and the exploitation of their natural resources. Extracting activities, particularly those that concern underground resources -and the violence that they entail for local communities and their environment (21) -, have historically been one of the factors for the emergence of indigenous political movements on the national and international scene insofar as these conflicts highlight indigenous peoples' marginalisation and exclusion from citizenship and political processes, and their unique situation in terms of human rights.

International law recognises what special rapporteur Daes has defined as indigenous permanent sovereignty over their lands and natural resources [START_REF] Daes | Indigenous Peoples' Permanent Sovereignty Over Natural Resources[END_REF], and rights that are entrenched in the UNDRIP at articles 25 and 26 [START_REF]or otherwise occupied and used lands, territories, waters and coastal seas and other resources and to uphold their responsibilities to future generations in this regard[END_REF]. Importantly, indigenous peoples' rights to land and resources are described as 'permanent sovereignty' and as a set of inherent and inalienable collective rights arising from indigenous polities themselves irrespective of colonial and contemporary state processes. They are wide ranging and include, among others, the right to own and to control their lands, the right to not be forcibly displaced from their lands, to oversee development and/or conservation processes, to maintain traditional ecological knowledge and practices, and to be consulted in projects affecting their territories according to the principle of free, prior and informed consent.

In practice, however, the recognition, protection and implementation of these rights remain dependent on state law and policy, most particularly in the case of mineral and underground resources which are construed, in a discriminatory manner, as strategic resources belonging to the state by virtue of its sovereignty, irrespective of its historical acquisition thereof [START_REF] Daes | Indigenous Peoples' Permanent Sovereignty Over Natural Resources[END_REF]. Generally some form of recognition is accorded by states to indigenous peoples -when they accept the existence of such entities -through the recognition in domestic law of traditional occupancy (which in the Anglosphere is the legal basis of native title at common law), historical attachment to particular tracts of country, or formal agreements made in the colonial and contemporary period.

Legal provisions for the recognition of indigenous peoples' land rights confront us with different problems. One is that, as many Latin American situations show, the titles obtained through legal action by indigenous groups are often inferior to any other type of property titles within domestic law and are subject to legal insecurity as they can be overridden by other rights or by acts of states. Hence, although land demarcation has been done in several countries since the 1970s, a wide range of conflicting situations remain and are in fact taking a new importance: from cases which oppose indigenous communities to family land owners to cases that oppose indigenous individuals, families or communities to multinational companies which use territories for developing extractive activities without consultation or consent (logging, mines, etc.), especially in Amazonia [START_REF] Fontaine | Gaz et pétrole en Amazonie. Conflits en territoires autochtones[END_REF]. The application of legal norms is therefore in question as well as the meaning of 'free prior and informed consent', particularly after the subtle shift produced by the World Bank in the second Manual of Operation regarding indigenous peoples, from 'consent' to 'consultation'. Similarly, in Australia, the jurisprudence of the Native Title Act 1993 (Cwth) has replaced a doctrine of terra nullius, which denied any legal and political legitimacy for indigenous peoples, by a doctrine of extinguishment through which Parliament and courts can legitimately put an end to indigenous' rights and interests to specific areas of land, a logic that is also pursued by Canadian policies that aims at extinguishing First Nations' Treaty rights. The length of procedures and a burden of proof mainly resting on the indigenous part without appropriate financial support are also common hindrances to indigenous claims. This difficulty of obtaining state recognition of indigenous rights and interests to land and resources deriving from their own polities and histories through peaceful or legal action constitutes, as Special Rapporteur Daes emphasises, 'the overwhelming majority of human rights problems affecting indigenous peoples' as land is the basis of the social, cultural and economic integrity of indigenous polities' [START_REF] Daes | Indigenous Peoples' Permanent Sovereignty Over Natural Resources[END_REF]. Her conclusion is that judicial mechanisms to resolve indigenous land rights issues are, at best, 'risky' (27) -not the least because of the difficult articulation of different regimes of rights and competing interests -while exhibiting what anthropologist D.B. Rose has defined as 'deep colonizing' for Australia: 'conquest embedded within institutions and practices which are aimed toward reversing the effects of colonization' [START_REF] Bird | Land Rights and Deep Colonizing: the Erasure of Women[END_REF]. The same difficulty also explains why in different parts of the world, questions of access, control and occupation of land take a conflicting nature, rooted in the inapplicability or inadequacy of legal and political processes. In extreme cases, such as the Mapuche situation in southern Chile, state can react by criminalising indigenous forms of resistance to land spoliation or discrimination, in this case by the application of 'anti-terrorist law', which delegitimises the indigenous character and criminalises their mobilisation as attacks against private properties. However, as the recent campaign of the Dongria-Khond against the Vedanta company in India, and many other cases throughout the Indigenous world, illustrate, the question of Indigenous land rights and permanent sovereignty over natural resources is not constrained anymore by the sole operation of the indigenous peoples/state relationship but, as states undergo neo-liberal economic reforms, increasingly involves transnational companies as prominent actors in the debate. Given their ambiguous status under international law, to say the least, and their increasing economic and political power as the resource boom feeds international competition, they need to be considered in any discussion of indigenous land rights.

Contested sovereignties

While the UNDRIP and even the concept of 'permanent sovereignty' do not call into question the supremacy of state sovereignty as the cornerstone of the international order, the various phenomena gathered under the term of 'globalisation' -massive migrations and displacements, transnationalisation of capital and communities, social fragmentation and market homogenisation, land purchases by states and private sector agents (trust funds, companies, etc.) -impose a reconsideration of the Westphalian system of sovereignty and of how we think about the articulation of territory, authority and rights [START_REF] Sassen | Territory, Authority and Rights: From Medieval to Global Assemblages[END_REF]. The Special Rapporteur on Human Rights and Transnational Companies regularly highlights in his reports the fundamental 'misalignement between the scope and impact of economic forces and actors, on the one hand, and the capacity of societies to manage their adverse consequences, on the other' [START_REF] Ruggie | Business and Human Rights: Mapping International Standards of Responsibility and Accountability for Corporate Acts[END_REF].

Under international law, transnational companies have a responsibility to 'protect, respect and repair' human rights in the countries they operate. However, nothing in international treaties and conventions directly addresses their status while, on the other hand the International Centre for Settlement of Investment Disputes (ICSID, an institution created by the World Bank) has consistently worked towards the protection of investors rather than states or their population. The issue is all the more reinforced for indigenous peoples since states are often dependent on the exploitation of their natural resources for their economic development, particularly in the context of the globalised resource boom.

While transnational companies challenge state sovereignty at their level by the sheer power of their economic weight, indigenous peoples (and other social movements, including transnational minorities, refugees and illegalised migrants) challenge it from within, through the disjunction they create between the state and the national communities. However, while indigenous peoples have been recognised as subjects of rights (and responsibilities) under international law, elaborating effective similar standards for private sector agents has proven much more difficult, possibly because they do not need so much protection as constraints on their operations. Here again, the capacity of indigenous peoples to implement their rights is also related to the state's capacity of governance: where states are dependent on international cooperation and monitoring, indigenous peoples and minorities are, paradoxically, in a somewhat better position to see their rights protected and respected than those living in the first world (such as in CANZUS states) where their capacity for development and their control of land and resources is almost entirely determined by state action.

Transnational companies are the subject of growing international attention, which is unfolding into a range of non-constraining instruments that inform their action with regard to indigenous peoples' rights [START_REF]Principles Concerning Multinational Enterprises and Social Policy, OECD Guidelines, or the World Bank Manual of Procedures regarding Indigenous Lands and Consultation; standards of performance and other instruments of procedures for increased transparency and accountability such as the International Finance Corporation's performance standards; and multi-stakeholder agreements such as the UN Voluntary Principles on Security and Human Rights[END_REF]. These instruments have severe limitations, not only in terms of their softness but also in terms of their accountability, transparency and assessment procedures by independent parties, but they point towards a growing practice of tripartite agreement-making between indigenous peoples, transnational companies and states which do result in the formal acknowledgement of indigenous rights and interests over their land and natural resources. These agreements not only include royalties (benefit sharing) but also employment, training, cross-cultural awareness programmes, investment in local businesses and organisations and even the provision of basic services such as housing or transport in replacement of the state. Although sustainability and positive long-term impacts have yet to be proven as far as local communities are concerned, they are nonetheless an important vehicle for the recognition of indigenous peoples' status and implementation of their right to self-determination [START_REF] Whiteman | Examining Justice and Conflict between Mining Companies and Indigenous Peoples: Cerro Colorado and the Nga¨be-Bugle´[END_REF]. Increasingly, also, non-government and civil society organisations play a part in these negotiations, both at the level of national space and international institutions. If national jurisdictions, their attitudes towards international instruments and their capacity of governance largely determine indigenous peoples' capacity to mobilise different regimes to implement their rights, the implication of international support organisations has also, for instance, contributed to re-encode the struggle for indigenous land rights into a more general environmental issue, thus garnering wider support across the local or international civil society. These organisations constitute a fourth meaningful agent (with indigenous peoples, states and companies) taking part in negotiations and standard setting but also in the development of local programmes and policies. While indigenous peoples were firstly determined by their relation to the state, this is no longer the case, mainly because of their reaching for a 'higher authority' in global institutions where they have developed a range of new alliances and networks [START_REF] Da | A Higher Authority: Indigenous Transnationalism and Australia[END_REF]. As the relational field in which indigenous peoples define themselves, their objectives and strategies, has changed so has the field of their action.

Indigenous development

It becomes increasingly evident that indigenous peoples are not opposed to development but rather seek to exert their right to self-determination within development initiatives, especially through defining their own criteria of what constitutes sustainable development, generally integrating social and cultural objectives alongside economic equality and environmental sustainability. This raises questions about the exact meaning and pragmatic conditions for the realisation of the principle of 'free, prior and informed consent', not the least because of the current lack of consensus over the meaning of 'consent' in international instruments and according to the different agents involved (although indigenous peoples themselves do have quite a clear idea of what they mean by consent and demand the right to say NO). While consultation has long been a feature of governance instruments, indigenous peoples seek to exercise a right to negotiation, although their political and economic fragility often complicates and constrains their capacity to oppose major development projects. Nonetheless there has been growing attention to these issues by mining companies in the last decade -although it could also be seen as a willingness on the part of major companies to buy off the social peace through their affirmed 'social responsibility', all the more so since long-term social and cultural impacts are difficult to evaluate.

Further, indigenous peoples' attitudes towards land rights and development are far from homogenous, building on differing conceptions of self-determination and autonomy. In Latin America, some scholars subordinate self-determination to political and economic emancipation while others consider that cultural autonomy primarily provides the right conditions for self-determination [START_REF] Stavenhagen | The Ethnic Question. Conflicts, Development and Human Rights[END_REF]. Regarding the rights to use natural resources, the former have been influenced by the fight for agrarian reforms in the sixties, the latter by demands for cultural recognition in relation to ancestral land [START_REF] Fontaine | El Precio del petro´leo. Conflictos socio-ambientales y gobernabilidad en la region amazonica[END_REF]. These two approaches differentiate highlands and lowlands movements, and correspond to a historic differentiation of struggles. But this differentiation is also found across other indigenous fields, for instance in Australia where the same opposition appears between those groups who argue primarily for economic development as a means out of poverty or 'welfare dependency' as opposed to those that pursue a rights-based approach to self-determination through demands for formal recognition of Indigenous sovereignty, land rights and cultural autonomy. No simple cultural or historical dichotomy, for example between urban and traditional elites, can account for the strategies chosen by these different agents. In Latin America as in Australia, however, both strategies for self-determination are related to the right for a free-determined development, in correspondence with the re-articulation at international levels of the concept of development with identity, or with culture and identity, and the formulation of the concept of a human rights-based approach to development [START_REF]Towards an Alternative Development Paradigm, Indigenous People's Self Determined Development (Baguio: Tebtebba, 2010); see also Ire`ne Bellier[END_REF]. In Australia this is manifested through a general strategy, adopted by indigenous groups who have secured some rights and interests to traditional lands, to develop 'caring for country' programmes and activities and invest in natural and cultural resources management. These programmes seek to develop what has been described as a 'hybrid economy' combining traditional subsistence activities with the market economy, or what Mashall Sahlins described as 'develop-man', where the product of economic activity is reinvested into local social and cultural institutions and values [START_REF] Altman | The Economics of Develop-man in the Pacific[END_REF]. Such programmes, however, particularly where the focus is on economic empowerment through environmental services and the exploitation of resources can also contradict strategies of conservation promoted by ecological groups and lobbies, with breakdowns in former alliances resulting as contradictory perceptions of what constitutes good natural and cultural resources management practices collide.

Conclusion

In the Preamble of the UNDRIP, the General Assembly affirms that the recognition, respect and protection of indigenous peoples' human rights -rights to self-determination; rights to language and culture; sovereignty over their land and resources and of their right to development -is a condition for sustainable development, perhaps all the more so since indigenous peoples tend to live in areas of high biodiversity. However, this vision is constrained by a number of factors -political relationships, economic imbalance -over which indigenous peoples, in national contexts and through global institutions, have limited influence.

Nevertheless, with the adoption of the UNDRIP by 149 member states of the UN (38), the paradigm has significantly shifted from a struggle for the recognition of indigenous peoples' human rights -a global movement which goes back to the early 1920s with Haudenosaunee leader Deskaheh going to the League of Nations in Geneva -to one for the concrete exercise and implementation of those rights entrenched in international law.

In our review of current and emergent issues, one sees that it is in those states that are transforming their own internal fabric through constitutional reforms, and, significantly, those countries that have ratified the only constraining convention on these issues (ILO 169), that indigenous peoples have been in a position to enter self-determining reforms to their political environment, albeit confronting strong resistances from conservative politicians and magistrates. Some significant changes in law and policy have also emerged from countries which entertain formal relationships with their indigenous peoples, such as New Zealand through the work of the Waitangi tribunal, thanks to the nomination of a (maybe unique) Maori magistrate at the High Court.

Through their engagement in domestic and international movements, indigenous representatives have acquired significant skills and expertise and established important networks both with domestic and international institutions. However, their sole existence cannot guarantee the kind of national transformations that the principle of selfdetermination calls for: strong support from civil society organisations and international non-governmental organisations, as well as domestic majorities and elites oriented towards the achievement of substantial equality are needed -in this area, the concepts, practices and institutions flowing from the notions of pluriversalism and plurinationalism in Latin America seem all the more interesting that they are articulated to other changes in the world system at large where the contours of governance and sovereignty are being redefined.

Indeed, another important emergent trend concerning the implementation of indigenous human rights is the growing implication of transnational actors within the indigenous field and, more generally, the accrued importance of third parties in the relationship between states and indigenous peoples. The associated issue with this change is the absence of a clear status both in international and domestic law for these emergent agents, whether transnational companies or migrants, although for different reasons. The international recognition of the global indigenous movements is thus simultaneously a manifestation of globalisation processes as well as a development that may impact significantly on its orientation. It signals a shift in the relational field of governance and human rights, indigenous peoples being the only rights bearer to have negotiated themselves the minimum standards by which state actions should be appreciated. The implementation of indigenous human rights implies effective actions and international cooperation on global issues such as climate change, biodiversity loss, resource predation and water management. In this sense, indigenous peoples' struggle for the implementation of their human rights has a global impact not only on their own situation but also on the global society as it is emerging and as a whole.


Arnaud Réveillère
email: a.reveillere@brgm.fr.

Jérémy Rohmer

Managing the risk of CO 2 leakage from deep saline aquifer reservoirs through the creation of a hydraulic barrier

Keywords: CO2 geological storage, hydraulic barrier, leakage, risk management, corrective measure

A prerequisite to the wide deployment of CO 2 geological storage at an industrial scale is demonstrating that potential risks can be efficiently managed, which includes deploying an adequate monitoring during the injection phase and having intervention plans ready in case of major irregularity. This paper considers the injection of CO 2 into a saline formation linked to a shallower aquifer through a leaky pathway. Brine, possibly followed by CO 2 , may start migrating up through the leak if sufficient pressure buildsup in the storage reservoir. For some man-made leakages (e.g. abandoned well), and more importantly for most of the natural ones (e.g. faults, fractured zone), acting on the transfer itself (i.e. on the leaky pathway) is hardly feasible. Consequently, the corrective measure hereby investigated aims at countering the main driving force of the CO 2 upwards migration which is the pressure build-up under the leak by injecting brine into the shallower aquifer, thus creating a hydraulic barrier. Results show that this can be an efficient way to stop a leakage in less than a year instead of letting it continue for hundreds of years, even with a low and decreasing flow rate. It may also be implemented as a preventive measure, while continuing storing CO 2 .

Introduction

CO 2 capture and geological storage (CCS) is under serious consideration by governments and industry in order to achieve large reduction in atmospheric anthropogenic greenhouse gases emissions. Depleted oil and gas fields or saline aquifers are seen as possible storage reservoirs, the latter offering more opportunities for further industrial development [1]. But a prerequisite to CCS large scale industrial developments is the demonstration by the operators that the containment is effective and the storage is safe [2]. In this view, an integrated safety strategy should both rely on site-specific risk assessment and on appropriate monitoring plans during and after the CO 2 injection period. Nevertheless, any industrial activity is confronted with residual risk and the need to know -what can be done‖ [3] in case of abnormal behavior of the CO 2 in the reservoir as outlined by the recently issued directive of the European Commission on CO 2 storage operations [4]. It states that the storage permit shall contain the approved corrective measures plan, a corrective measure being -any measures taken to correct significant irregularities or to close leakages in order to prevent or stop the release of CO 2 from the storage complex‖. Therefore, a proper risk management scheme should also be completed with a site specific risk based interventions plan in order to demonstrate that any undesired consequence can be mitigated.

In case of leakage, different remediation strategies can be deployed, either (1) acting on the root causes of the leakage, such as controlling the pressure build-up [3] or relying on dissolution and residual trapping ([5], [6]) or (2) acting on the transfer itself relying for instance on intervention strategies for leaky wells based on the long experience of the oil and gas industry [7]. Nevertheless, for most of the natural leakages (e.g. faults, fractured zone) directly acting on the transfer (i.e. on the leakage pathway) is hardly practicable, as discussed in section 3.

In this regard, the corrective measure investigated in the present paper is based on the -hydraulic barrier‖ technique aiming at decreasing (or reversing), the pressure gradient in the leak through fluid injection into the top aquifer, thus countering the main driving force of the CO 2 upwards migration for the case of a CO 2 storage aquifer formation connected to an overlying aquifer (possibly used for monitoring) through a leaky pathway that would not have been detected during the site characterization stage (see Figure 1).

The intervention plan is investigated using a three dimensional large scale multiphase fluid flow transport model described in section 2. The leakage and the possible detection techniques and corrective measures are discussed in section 3. The hydraulic barrier itself is discussed in section 4, in a corrective and in a preventive approach.

Model set-up and parameters

The proposed intervention plan is investigated considering the following scenario: the operator plans to inject 100 kg/s (about 3 million tones of CO 2 per year) during 10000 days (about 27 years) through one injection well in a saline aquifer. The storage formation is connected to an overlying monitoring aquifer through a porous column, representing a leakage pathway. This leak may represent a poorly plugged well or a localized faulty area. Note that in case of a fully unplugged well, a pipe-flow model should be used [8]. This leaky pathway might lead to a -major fluid leakage‖. By -major leakage‖ we mean that the leak generates a significant pressure build-up in the shallower aquifer, possibly leading to its detection and localization by the monitoring system and that natural flows through the caprock [9] as well as other leakages are assumed to be negligible. This model is close to the problem 1.1 of a recent benchmark assessing code performance for CCS modeling [10]. The main differences are that we presently use an 11 times bigger CO 2 injection rate and a 120 times larger lateral extension. This conceptual scenario is modeled using a three dimensional grid made of two horizontal and homogeneous 78 by 78 km aquifer layers connected by a pathway conduit (Figure 1). The multiphase flow transport simulator TOUGH2 [11] is used and the properties of the brine -CO 2 mixture is accounted for using the TOUGH2 module ECO2n [12]. The grid mesh is composed of a central 1 km 2 area of 25 m x 25 m grid bocks. Additional refinements using local grid refinement technique [13] are carried out around the wells and around the leak following a logarithmic progression so that the minimum area reaches 1.6 m1.6m. The leakage pathway has a 6.3 m6.3m section. Outside of the central area, the grid cells dimensions follow a logarithmic progression so that grid cell radius are doubled every three elements up to a distance of 80 km and no grid block has more than two connections per face.

Gravity effects are assumed to be negligible in the storage aquifer, which is consequently represented by one 100 m thick layer, but are taken into account into the leakage pathway and in top aquifer which are made of three 10m thick layers. No-flow Neumann boundary conditions are imposed below and above the aquifers as we consider that the fluid flow though the leakage pathway dominates other possible migration outside of the aquifers. The vertical surface defined by the CO 2 injection well and the leak is a symmetry plane for the flow.

Properties and initial conditions of the bottom layer (storage aquifer) are typical of what may be encountered in saline aquifers at a depth on the order of 1.2 km (table 1). Characteristic curves use the same parameters as those used in the -Problem No.2‖ exposed in [12] (table 2).

Intervention strategy

Leakage analysis

Assuming that the leakage pathway has not been detected, the CO 2 injected in the reservoir formation will migrate to the monitoring aquifer through the leakage pathway leading to a secondary accumulation of 32 000 tons of after 27 years (at the end of the CO 2 injection) and 222 000 tons (which is 0.0005% of the total amount of injected CO 2 ) after a thousand years. This clearly shows that the end of the CO 2 injection is clearly not enough if the goal is to stop the leakage in the long term. In this example, at 1000 years, 87% of the leakage would have occur after the end of the CO 2 injection period (at 27 years) as the leakage continues with a limited decline due to the slow pressure decrease in the storage aquifer [3]. In order to have some order of magnitude of the size of the leakage we consider in this study, we may notice that its maximum (over 10 tons per day) corresponds to one percent of the estimated atmospheric CO 2 emissions on the natural site of Mammoth Mountain (which is estimated around 1200 tons per day [14]).

This CO 2 leakage rate admits no maximum before the end of the 10000 days of CO 2 injection, contrarily to what is observed in the benchmark on the modeling of a leakage through a well [10]. This is coherent with semi-analytical solutions [15] for the infinite and finite boundary cases: the maximum is a consequence of the constant pressure imposed as a boundary condition. In this model, the pressure pulse barely reaches the lateral extent, the aquifer can therefore be considered as infinite.

Leak detection

In the present situation of a storage aquifer overlaid by a shallower one, seismic and pressure monitoring methods are considered as the best developed [16]. Detection through pressure monitoring may occur prior to any CO 2 leakage, as the brine, pushed by the injected CO 2 , will flow through the leak first (cf. figure 2) and create a potentially detectable overpressure in the monitoring aquifer before the gaseous plume reaches the leak. We consider the detection of the leak to be -likely‖ at an overpressure threshold of 0.1 bar [8]. Seismic monitoring, can detect supercritical CO 2 that has migrated out of the reservoir and become trapped as a secondary accumulation under the overlying layer. Under conditions similar as those observed at Sleipner or Weyburn, accumulations of 1000 to 10000 tons of gaseous CO 2 could be detected at a depth of 1 km [16].

Seismic monitoring would directly locate the gas accumulation, and thus the top of leakage whereas it requires at least several pressure gauges signals and the use of new methodologies based on the comparison of monitored signals with analytical expressions that depend on the relevant distances among other parameters [17]. In the following, we suppose that the leak has been detected and localized. Two situations are considered: (1) it happens after 300 days, which is necessarily made by pressure monitoring as no gas has leaked so far. At that point the overpressure exceeds the 0.1 bar detection threshold in a radius of 2.2 km around the leak.

(2) The detection happens after 10 years, as 5300 tons of gaseous CO 2 are trapped in the shallower aquifer and the overpressure exceeds 0.1 bar up to 8.5 km away from the leak.

Corrective actions

Leakage pathways may be classified as either man-made or natural, leading to very different corrective actions. The first case corresponds to wells in operation or abandoned ones, hence to a complex engineered structure, from which CO 2 might leak through various flaws [18]: via altered material (through the steel casing as a result of corrosion, through the cement sheath or the cement plug due to either degradation or fracturing) or along interfaces (rock formation/cement fill, cement fill/steel casing, cement well plug/steel casing). Various intervention strategies are already available and have been tested, usually by the hydrocarbons industry ([19], [20], [7]). In case of detected flaws, standard techniques exist to repair (e.g. wellhead repair, squeeze cementing, patching casing) or replace defective well elements, or to abandon the well. In case of uncontrolled well (-blow-out‖), protocols exist in order to -kill‖ the well by injecting weighed fluids [21]. Major research efforts currently focus on the loss of mechanical integrity of wellbore system in the long term [22].

The second case, the natural pathways, includes potential flaws within the caprock formation, natural faults or fractured zones. In contrast to engineered man-made pathways, intervening at depth levels considered for CO 2 storage on such natural systems lacks of past experiences. The main strategy is to create chemically or microbiallyinduced barriers by changing the hydraulic properties either directly within or above the pathway. It can take advantage of experiences gained in oil and gas activities in applying polymer-gel treatments to reduce channelling in high-pressure gas floods and to reduce water production from gas wells ([23], [24]). Initially such techniques were mainly used for controlling the flow into matrix-rock porous media and recently, studies have reported successful results application to fractured rock [25]. Another recent concept is based on engineered microbial biofilms which are able of precipitating crystalline calcium carbonate using the process of ureolysis, hence sealing the targeted pathway [26]. But such approaches still represent an area of ongoing research works.

However, in some the cases of man-made leakage, and more importantly in most cases of natural leakage pathways, acting on the transfer is hardly feasible. In this article, we propose an alternative corrective option aiming at countering the driving forces of the leakage based on the creation of a hydraulic barrier (also named -pressure ridge‖) in order to counter the hydraulic gradient that drives the flow up in the leak. It is created by increasing the pressure over the leak through water or brine injection in the monitoring aquifer. Hydraulic barriers are a commonly-used preventive or corrective measure in pollution engineering. For instance, production or injection wells can be used to locally modify the hydrogeology in order to protect the drinking water against salt water intrusion, which is one of the most widespread forms of groundwater pollution in the coastal areas [26,27]).

The injection of water or brine in the top aquifer may be created either by drilling a new well at the location of the leak, or by turning an existing monitoring wells nearby into a brine injection well. The latter case is expected to have lower costs and delays, but its applicability has to be evaluated for each particular leakage situation. The distance from the leak is a major parameter to consider, as it governs the required injection pressure and the consequent mechanic risks (fracturing). The internal diameter of the wells (which may range from 2.5 inches -6 cm -or even less to 9 5/8 inches -24 cm -in Ketzin) should not be a major issue, as it would only require higher power surface compressors to compensate the higher pressure drop in the well. But a monitoring well that has not been designed for bearing high injection pressures may not be usable as there is a risk of collapse of the casing (e.g. by breaking pipes threads, or bursts in the corroded areas). Moreover, if the quality of the bottom primary cementation is not good enough, there is a risk of upwards flow through the annulus and even of lifting up the whole casing (personal communication of JY Hervé). We consider here that a well located 1 km away from the leak can be used and that the brine can be produced from the same aquifer or that injecting surface water is temporarily authorized.

The time delay in case of an additional drilling, from the decision to the operational well, varies depending on several parameters including the depth, the availability of suitable drilling rigs and the delay for ordering and receiving the tubing. For instance, in the Paris basin, the delay for drilling a new classical geothermal energy well (1700 m deep; 9 5/8 inches production casing) is at least 6 months, as the delay before having a rig able to reach a depth of one kilometer (there are only 4 in France) and passing the order for the tubing may take at least 4 to 6 months. In case of emergency workover operations on such wells, which do not require new tubing, the typical delay is one or two months (personal communication of E. Lasne). This does not prejudge of what can be done in case of extreme emergency, and delays might be significantly shorter in regions experiencing an important oil & gas production activity (due to the local presence of numerous rigs and suppliers). We consequently assume that the delay from the stopping of the CO 2 injection range from an immediate brine injection (brine is available, the surface piping and a brine injection well are ready to be used) to one year, a six month delay being the reference case.

Hydraulic barrier

In a corrective approach

In our corrective action case, we consider that the CO 2 injection is stopped when the leak is detected. In the first situation as defined in section 3.2., when injection is stopped at 300 days, the CO 2 never reaches the leak and no CO 2 migrates to the upper aquifer. Consequently, this paragraph will be focused on the 10 years detection situation.

At that point there are 6342 tons of CO 2 (gaseous or dissolved) in the shallower aquifer. The pressure barrier is achieved by injecting brine from a well located at a lateral distance of 1 km from the leak (figure 1). The injection operations are carried out until the leakage stops. As depicted in the figure 3, the leakage rate decreases to zero in less than one year. Several scenarios for brine injection flow rate and time delay for setting up the intervention are considered (Table 2). This parametric study shows that both parameters have little influence on the final long term results (1000 years), in all cases the total leakage has been greatly reduced compared to the natural recovery. The secondary accumulation of CO 2 represents a potential threat as it might give rise to a high-energy discharge to the surface, a so-called « pneumatic eruption » through pre-existing faulted zones connected to the shallow subsurface or to the surface [9]. A solution is to continue injecting brine in order to displace the plume of gaseous CO 2 and thus to enhance its dissolution and its residual trapping. This is similar to a recently proposed remediation strategy consisting in brine injection through the former CO 2 well for trapping the plume in the storage aquifer [6], excepted that we only target the CO 2 that has leaked in the shallower aquifer and that our model does not account for hysteretic effects. We show in the figure 4 the shape of the plume in a vertical cross-section that includes the brine injection well and the leak, showing the sweep of the plume by the injected brine.

In a preventive approach

Let us consider the case in which there are hints of a possible leakage, but investigations can not reduce the uncertainty on its presence (e.g. doubts on the origin of a pressure build-up observed in the shallower aquifer). In that situation, preventive actions may be deployed by setting up a hydraulic barrier while continuing the CO 2 injection as initially planned. The investment made for the whole capture and storage chain can therefore continue being used and the business plan of the operator for valorizing the operation remains almost unchanged.

For designing that preventive barrier, the brine injection has to be chosen in order to create a slightly higher pressure build-up above the leak (obtained by applying standard single phase well functions) than the one created by the CO 2 injection under the leak (estimated based on the numerical simulations of the reservoir carried out before obtaining the injection permit).

In the first situation, the leak is detected at 300 days and a 30 m 3 /h (9.1 kg/s) brine injection immediately starts and lasts until the end of the CO 2 injection. As depicted in figure 5, this strategy ensures that the overpressure over the leakage pathway is slightly higher than the overpressure under the leak. Numerical simulations confirm that no CO 2 migrate into the shallower aquifer in that case. The higher overpressure in the top aquifer creates a small brine flow downwards and we observe a low saturation zone under the leak. This prevents the CO 2 upwards migration driven by the buoyancy force after the injection period.

In the second situation, the leakage is detected at 10 years and a 50 m 3 /h brine injection starts at that point for 4 years, the injection flow rate being then reduced to 30 m 3 /h until the end of the CO 2 injection. In this case, the CO 2 leakage quickly decreases before stopping.

Figure 5: simulated over-pressure under the leak created by the CO2 injection and analytical pressure build-ups above the leak created by the designed hydraulic barriers. Situation 1: a 30 m 3 /h brine injection starts at 300 days. Situation 2: brine is injected at 50 m 3 /h from 10 to 14 years, and at 30 m 3 /h after.

Concluding remarks and further works

In this study we have investigated the applicability of the hydraulic barrier technique for stopping the CO 2 upwards migration through a leak from a storage reservoir to an overlying aquifer, in both corrective and preventive (CO 2 injection continues) approaches. Once the upwards CO 2 migration has began, the simplest corrective action is to stop the CO 2 injection, but it does not stop the leakage which continues for centuries. Compared to that natural recovery case, setting-up a hydraulic barrier stops the leakage in about a year for the simulated generic cases (for various intervention delays and flow rates) and prevents from any posterior leakage. Furthermore, the brine injection displaces the gaseous CO 2 plume accumulated in the shallower aquifer, thus enhancing its trapping through dissolution and capillary processes. These results are valid for the considered case; further parametric studies should be carried out for assessing the influence of site-and leak-specific parameters on the hydraulic barrier design. However, results will have the same order of magnitude and the main point to remember is that the hydraulic barrier can prevent the leakage or stop it in less than a few years instead of letting it continue in the long term, even with a low and declining flow rate. A key issue for a proper implementation of this technique (for its efficiency and for reducing the brine injection and the induced mechanic risks) is the ability of detecting and locating the leak as early as possible. Part of further investigations is to evaluate if this can be achieved by pressure monitoring as it is the first detectable evidence of a leakage.

Figure 1 :

 1 Figure1: Simplified geologic model and its 3D mesh representation for modeling the leakage through a porous column from a storage reservoir to a shallower aquifer. The reservoir layer is assumed to be located at 1200 m deep.

Table 1 :

 1 Rocks properties and initial conditions (left) and characteristic curves models and parameters (right. Notations refers to [11]) Porosity 12 % Permeability 10 -13 m 2 for the storage aquifer and the leak; 10 -14 m 2 in the monitoring aquifer Initial pressure 120 bar in the bottom layer, hydrostatic gradient Initial temperature 45 °C in the bottom layer; 3°C/100 m gradient Initial salinity 15 % wt = 165 g.L -1

  Figure 2: Leakage flow rate through the leak during and after the injection when the injection plan is followed

Figure 3 :

 3 Figure 3: CO2 leakage rate. The CO2 injection stops at 10 years and various cases of hydraulic barriers are experienced. Cf. Table2for the description of the cases and results.

Figure 4 :

 4 Figure 4: Gas saturation (left) and CO2, aq mass fraction (right) in the upper aquifer (average of the three layers) in a vertical cross-section from the brine injection well (located at 0m) to the leak (locate at 1000 m) after 0, 1.5 and 5 years of brine injection at 15 m 3 /h

  Table 2 for the description of the cases and results.

Table 2 :

 2 Hydraulic barrier as a corrective action cases and results. CO2 injection was stopped at 10 years, and at that point there were 6342 tons of CO2 in the shallower aquifer.

	Case	Brine injection design	CO2 in the shallower aquifer after 1000 years
		Delay	Flow-rate	Duration	in tons	Part having leaked
		(month)	(m3/h)	(month)		after 10 years
	Natural recovery	0	0	0	166250	96%
	1	0	30	12	6640	4%
	2	6	30	10	7141	11%
	3	6	15	18	7359	14%
	4	12	30	8	7351	14%

Acknowledgements

This work was funded under the BRGM's Directorate of Research project. We would like to thank P. Audigane and C. Chiaberge and J.-Y. Hervé from BRGM and E. Lasne from CFG-Services as well.

 , 1985, vol 37, n°8, pp. 1267-1275 -[22]Berge, G. Improving wellbore seal integrity in CO2 injection wells, Energy Procedia,1,[3523][3524][3525][3526][3527][3528][3529] Raje M, Asghari K, Vassoughi S, Green DW, Willhite GP (1999) -[26] Parrek N, Jat MK, Jain SK.The utilization of brackish water, protecting the quality of the upper fresh layer in coastal aquifer. Environmentalist 26, 237-246, 2006. -[27] US EPA (1999) The Class V Underground Injection Control Study, volume 20, Salt Water Intrusion Barrier Wells, EPA/816-R-99-014t.


Stéphane Gaillard

I Leguérinel

N Savy

P Mafart

QUANTIFYING THE COMBINED EFFECTS OF THE HEATING TIME, THE TEMPERATURE AND THE RECOVERY MEDIUM PH ON THE REGROWTH LAG TIME OF BACILLUS CEREUS SPORES AFTER A HEAT TREATMENT

Keywords: Bacillus cereus, heat treatment, lag time, recovery

come

Quantifying the combined effects of the heating time, the temperature and the recovery medium pH on the regrowth lag time of Bacillus cereus spores after a heat treatment

Introduction

Bacillus cereus is a pathogen that produces two heat resistant toxins which are likely to cause more or less severe infections [START_REF] Granum | Bacillus cereus and its toxins[END_REF]Johnson,1984). The level of population which can generate infections is in the magnitude of 10 5 -10 6 spores per gram [START_REF] Granum | Bacillus cereus and its food poisoning toxins[END_REF]. This bacteria belongs also to the spoilage flora of dairy products because of the action of its lecithinase on the globule membrane of milk fat (Jean [START_REF] Stone | The action of lecithinase of Bacillus cereus on the globule membrane of milk fat[END_REF].

The heat resistance of Bacillus cereus spores is extremely variable, with a D-value (time of decimal reduction) ranging from 5 to 108 minutes at 85°C and from 0.3 to 27 minutes at 100°C respectively [START_REF] Bergère | Heat resistance of Bacillus cereus spores[END_REF]Picoche et al., 1993). Because of their relatively low heat resistance, most of strains are able to survive and grow after a pasteurisation .

It is well recognised that the lag time of growth of bacteria is dependent on the "history" of the bacterial population, especially its previous thermal conditions. As an example, [START_REF] Kaufmann | Effect of heat treatment on the growth of surviving cells[END_REF] observed a lag time of growth of 25 hours for the strain of Micrococcus MS102 after a heat treatment at 82°C instead of 19 hours after a heating at 76°C. A few studies have been published on modelling the influence of environmental recovery conditions on the viability of injured spores [START_REF] Mafart | Modelling the heat stress and the recovery of bacterial spores[END_REF]Baker and Griffiths, 1993).

However, the mathematical description of the growth after heat treatment as a function of the duration and the intensity of the thermal stress was very scarcely studied. [START_REF] Mafart | Modelling germination kinetics of spores of Clostridium tyrobutyricum: a tool for predictive microbiology[END_REF] proposed a model describing the part of the lag corresponding to the activation and the germination of spores. [START_REF] Bréand | A model describing the relationship between lag time and mild temperature increase duration[END_REF][START_REF] Bréand | A model describing the relationship between regrowth lag time and mild temperature increase for Listeria monocytogenes[END_REF] studied the impact of a previous thermal stress on the growth of Listeria monocytogenes and Eschericia coli. They observed a three-phases behaviour of the lag time versus the duration of the heating exposure. The lag first increased until a maximum before decreasing at a steady level. Similar observations regarding Bacillus cereus were reported by [START_REF] Laurent | A quantitative approach for studying the effect of heat treatment conditions on resistance and recovery of Bacillus cereus spores[END_REF], with a decreasing phase which was less clear than that observed by Bréand et al.

The aim of our work was to get a quantitative approach of the effect the heating time, heating temperature and pH of the recovery medium on the lag time of growth of Bacillus cereus.

Material and methods

Microorganism and spore production

The strain of B. cereus (Bce1), isolated from a dairy food line process, was supplied by Danone (France). Spores were kept in distilled water at 4°C. Cells were precultivated at 37°C for 24 h in Brain Heart Infusion (Difco). The preculture was used to inoculate nutrient agar plates (Biokar Diagnostics BK021) added with MnSO 4 40 mgl -1 and CaCl 2 100 mg -1 on the surface area. Plates were incubated at 37°C for 1 month. Spores were then collected by scraping the surface of the agar and suspended in sterile Phosphate buffer M/15 at pH 7 and washed three times by centrifugation (10 000 x g for 15 min) (Bioblok Scientific, model Sigma 3K30). The pellet was then resuspended in 5 ml distilled water and 5 ml ethanol. The suspension obtained was kept at 4°C for 12 h in order to eliminate vegetative nonsporulated bacteria and washed again three time by centrifugation. Lastly, the final suspension (about 10 10 spores ml -1 ) was distributed in sterile Eppendorf micro-tubes and kept at 4°C.

Thermal treatment of spore suspension

First, 30 l of spore suspension was diluted in 3 ml heating medium (Biokar nutritive broth, 20g / L) . Capillary tubes of 100 l (vitrex) were filled with 100 l of sample and submitted to a thermal treatment in a thermostated bath. After heating, the tubes were cooled in water/ice bath, washed in solution of soap and rinsed with sterile distilled water. Finally, ends were flamed with ethanol. The capillary tubes were broken at both ends and their contents poured into a tube containing 9 ml of sterile tryptone salt broth (Biokar Diagnostics) for an appropriated series of decimal dilutions, by rinsing with 1 ml broth contained in a needleequipped syringe.

When the effect of the duration (up to 50 minutes) and the temperature (85, 90 and 95°C) of the heat treatment on the lag was investigated, the pH of the heating medium was fixed at 7.

The investigated ranges of times and temperature correspond to those which are classically used in food process.

Growth conditions and measurements

Liquid tryptone salt broth was adjusted to the aimed pH by citric acid and distributed by fractions of 10 ml in special flasks topped by a calibrated tube allowing measurements of optical density with a spectrophotometer (600 nm). Each flask was inoculated with 1 ml from the last decimal dilution tube and incubated at 25°C under shaking (150 rotations per minute).

A calibration of the spectrophotometer (optical density versus cellular concentration) was previously carried out: spores were firstly submitted to a thermal activation (90°C for 1 min at pH 7). The growth was then followed both by the optical density of the culture and the Most Probable Number technique. Because spores and vegetative nonsporulated cells don't yield the same optical density, the calibration curve was fitted only after the growth time corresponding to a sufficient cellular concentration (3.10 6 cells per ml) that allowed the concentration of spores to be neglected. The following equation was obtained:

Ln OD = 0.793 Ln N -15.583 (R 2 = 0.991)

. The effect of the pH of the medium, ranging from 5.5 to 7, was investigated by fixing the temperature of the heat treatment at 90°C.

Lag time estimation

The lag time was defined as the intersection point of the straight line describing the exponential growth expressed as logarithm of the bacterial concentration versus time, with the horizontal line at the logarithm of the initial bacterial concentration. It was checked that the size of the inoculum had no effect on the lag time (data not shown).

Parameters estimation

The estimations of the parameters of the models are obtained by the least squares method via the Matlab© function `nlcurvefit'. The criterion of Beale [START_REF] Beale | Confidence regions in non-linear estimation[END_REF] provides us a tool allowing construction, by numerical simulation (technic near to that of Lobry et al. [START_REF] Lobry | A fortran subroutine for the determination of parameter confidence limit in non-linear models[END_REF]), of a hypervolume of confidence to the risk 5% which is conventionally retained .

Projection on each axis of the space of the parameters gives us an interval of confidence of this parameter.

Results

General pattern of curves

The figure 1 shows the effect of the time of heating at 90°C and different pH, on the lag time of growth after the thermal treatment. As expected, it can be seen that roughly, the lag increases with the time of heating exposure, but patterns of curves are more or less complex.

Under pH 6, a three-phase behaviour of the lag versus treatment time which recalls that observed by [START_REF] Bréand | A model describing the relationship between lag time and mild temperature increase duration[END_REF] can be observed: an increasing phase followed by a short steady or decreasing phase and, lastly, an increasing phase again, with a higher slope than that of the first one. The minimum lag times were observed at pH 6.5.

When duplicates or triplicates were carried out, the repetability of data was relatively fair for short times of heat treatments, but, in proportion as the exposure time increased, curves became more and more divergent (see fig. 2). On the other hand, the observed three-phase patterns , when they existed, were less clear than those observed by Bréand et al., and were always suggested by a single point of curves. For these reasons, it was decided to fit only the first linear phases of curves which was limited to the interval ranging from the initial time to the time corresponding to the decimal destruction ratio n = 2 (n = log N 0 /N herein N 0 and N represents the initial number of spore and the number of surviving bacteria after the heating respectively). It was then assumed that in this restricted range, the lag of growth versus the previous heating time followed a linear relationship:

 =  0 + mt (1)

Secondary modelling of the initial linear phase

Data corresponding to the previously limited range (0 < n <2) were fitted according to a simple linear regression. The logarithm of the slope (log m) was then plotted versus temperature at pH 7 (fig 3) and versus pH at a heating temperature of 90°C (fig 4).A Bigelow type linear relationship between log m and the heating temperature could be observed.

Regarding the effect of pH on the slope m, the pattern of the curve recalled that which was previously observed by plotting logarithm of D-values of spores versus pH [START_REF] Mafart | Modeling combined effect of temperature and pH on the heat resistance of spores by a linear-Bigelow equation[END_REF]. Assuming a priori that interactions between the heating temperature and the pH of the medium could be neglected, we tried to fit the slope of Eq 1 according to the following four parameters equation:

(2) herein T* represents the reference temperature, while pH opt is a parameter to be estimated which corresponds to the pH at which the m-value is minimum. Parameters  T and  pH play the same rules than the conventional z-value and the z pH value which is included in the previous Mafart model respectively. Lastly, m* represents the slope of Eq 1 at the reference temperature and the optimal pH. Parameters estimates are indicated in table 1.

Despite the difficulty of getting accuracy data related to lag times, the adjusted R 2 (0.889) indicates a fair goodness of fit of the model.

Figures 5 and6 represent the plotting of the logarithm of the intercept  0 of the linear Eq 1 versus the heating temperature and pH respectively. As  0 corresponds to the lag time of growth without any heat treatment, the absence of effect of the heating temperature on this

2 * * log log              pH opt T pH pH T T m m  
parameter was expected. A variance analysis (not shown) detected a slight but significant effect of pH on the value of  0 . However, the lack of accuracy of results (see fig 6) did not allow any fitting of the data to a relevant model. Rough data allow only to get approximate magnitudes of  0 ranging from around 2.5 h at pH 6.5 to 6.3 h at pH 5.5.

Discussion

The overall lag time of growth of spores includes both the time of germination of spores and the time of first division of outgrown cells. Moreover, the overall observed lag time decreases as the maximum germination ratio of the population of spores increases [START_REF] Mafart | Modelling germination kinetics of spores of Clostridium tyrobutyricum: a tool for predictive microbiology[END_REF]. It is then clear that the measured lag is narrowly linked to the conditions of activation and germination of spores, as well as to the lethal effect of heating: the resulting counteracting factors could then explain the relative complexity of the patterns of curves (figure 1) . Powell and Hunter (1955) observed, at temperatures ranging from 50°C to 80°C, that the ratio of germination of Bacillus spores decreased when temperatures increased. In the case of Bacillus megaterium , Levinson and Hyatt (1970) found an effect of temperature, with an optimal value, both on the rate of activation of spores and on the maximum ratio of germination. Above 68°C, they observed a decrease of the ratio of germination and an increase of the lag time of germination. This last observation is in agreement with our data which point out an increase of the lag with heating temperature.

The low value of  pH (0.98) indicates a high sensitivity of the lag time toward the pH of the heating medium: a difference of about 1 pH unit with the optimum pH, inside the investigated range, causes a ten-fold increase of the lag.

The z-value of the strain was previously estimated: it can be seen that this value (z = 8.55°C with a confidence interval of 7.30-10.29°C, unpublished datum ) is close to the  T estimate ( T = 7.06°C with a confidence interval of 4.94-12.38°C). This comparison allows to consider that, in the case of the studied strain, the assumption of an equality between z and  T values could not be rejected. In these conditions, for a fixed pH of the heating, Eq 2 could be expressed as follows:

Or (3) (4)
The combination of Eq 1 and 4 yields:

(5) herein F represents the well known sterilisation value (F-value) which is defined as the time (in minutes) of a heat treatment at the constant reference temperature (generally, T* = 121.1°C°), or as any equivalent heat treatment which would cause the same destruction ratio.

Then, Eq 5 points out an interesting significance of m* which would correspond to the slope of a linear relationship between the lag time of growth and the sterilisation value submitted by spores before growing. The high sensitivity of the overall lag time toward the pH can be explained both by the well known effect of this factor on the lag time of outgrown of cells and by its effect on the germination of spores. Blocher and Busta (1985) observed a progressive inhibition of the germination of Clostridium botulinum when pH decreased from 7 to 5.5. Regarding Bacillus cereus, Vas and Proszt (1957) noted a decrease of the rate and of the maximum ratio of germination when pH was decreasing, regardless of the type of organic acid implemented for controlling pH, except acetic acid which caused a total inhibition of germination at pH as high than 5.5.

  Fig 2aFig2b

of germination requirements as a result of preheating. J. Gen. Microbiol. 13 , 59-67. Vas, K. , Proszt, G. 1957. Effect of temperature and hydrogen-ions concentration on the germination of Bacillus cereus. Nature. 179, 1301-1302.

Legend Table

Parameters estimates of equation 2.

Legend Figure