Bertrand Guilloux

STAPS Bertrand Baron
email: bertrand.baron@univ-reunion.fr

Pacing Strategies and Emotional Pattern During Intermittent 3-min runs in Secondary School Participants

Keywords: Pacing strategy, Emotions, Motivation, Perceived exertion

The aim of this study was to analyse pacing strategy and emotional regulation during intermittent 3-min runs. 127 school participants performed 2 exhaustive intermittent 3-min runs at different days. The effort, the pleasure, the desire to continue, the desire to stop and the level of resources were measured every 100m with Likert scales from 0 to 10. The CONTROL group was asked to realize 2 runs as fast as possible without any other consign. The RPE group was asked to realise the first run with the same consign but has to start the second run at a minimal RPE level corresponding to the average RPE of the first run. For this, subjects were asked to self-select the intensity which induced the expected RPE. Then, exercise is totally self-paced.

The strategy, which consists in a slow start with an increase of speed at the end, could be observed, for each test of each group. Fluctuations of running intensities exist, except during the second run of the RPE group. An important emotional reserve was observed in each condition. But this reserve was lower during the second run for the RPE group, contributing to the increase in performance during the second run for the RPE group (+13.5%), whereas it was not significantly different for the CONTROL group.

For each group and each test, effort, affective balance and desire to stop significantly increased between the first and the last repetition, whereas pleasure, desire to continue and available resources significantly decreased during running. The most important observation is that the emotional pattern corresponded to a linear evolution in each condition whereas exercise is self-paced. This highlights that emotional regulation is a part of pacing strategy.

Finally, we define the motivation to pursue a tired exercise as the level of acceptance of effort. We propose that the ratio between the desire to continue and the level of effort could be considered as a good marker of the motivation in this context.

Elite athletes optimally monitor the intensity of exercise in order that their energy-producing capacities are not exhausted before they reach the finish line [START_REF] Hulleman | The effect of extrinsic motivation on cycle time trial performance[END_REF]. Hettinga et al. [START_REF] Hettinga | Pacing strategy and the occurrence of fatigue in 4000-m cycling time trials[END_REF] have suggest that athletes develop a stable template of the power outputs they can sustain during exercise of different durations or distances. The optimum pacing strategy requires the presence of an accurate pre-established estimate of the power output that can be sustained for the duration of the event [START_REF] Hettinga | Pacing strategy and the occurrence of fatigue in 4000-m cycling time trials[END_REF]. This process has been described as an internal negotiation, which requires an estimation of the magnitude of the task remaining, the momentary aerobic power output and the remaining anaerobic energetic reserves amongst other inputs [START_REF] Foster | Effect of competitive distance on energy expenditure during simulated competition[END_REF]. Pacing strategies can be thought of as a complex process in which the subject controls the intensity of exercise at any time by taking into consideration physiological and psychological reserves in relation to the estimated time until the finish [START_REF] Garcin | A new rating scale of perceived exertion based on subjective estimation of exhaustion time: a preliminary study[END_REF] at that exercise intensity.

During exercise performed at severe intensity, what prevents the occurrence of catastrophic fatigue is the interaction of a protective mechanism that precedes the failure in physiological systems and manifests itself as powerful perception of fatigue and displeasure [START_REF] Baron | Variation and homogeneity in affective responses to physical activity of varying intensities: an alternative perspective on dose-response based on evolutionary considerations[END_REF]9].

Emotional process is of great importance in pacing strategy [START_REF] Baron | Variation and homogeneity in affective responses to physical activity of varying intensities: an alternative perspective on dose-response based on evolutionary considerations[END_REF]. Individuals develop strategies that allow them to reach their goals, and mobilize and monitor their behaviours in order to attain their goals [START_REF] Seo | The Role of Affective Experience in Work Motivation[END_REF]. Emotional phenomena represents central mechanisms of self-regulation that help humans deal effectively with their environments [START_REF] Seo | The Role of Affective Experience in Work Motivation[END_REF][START_REF] Damasio | Descartes'error: Emotion, Reason and the Human Brain[END_REF][START_REF] Damasio | The Feeling of what Happens: body and emotion in the making of consciousness[END_REF].

The study of Lander et al. [START_REF] Lander | Self-paced exercise is less physically challenging than enforced constant pace exercise of the same intensity: influence of complex central metabolic control[END_REF] demonstrates that self-paced exercise pose a reduced metabolic challenge when compared with matched-intensity enforced constant paced submaximal exercise. It is likely that this is attributable to the ability to voluntary fluctuate power output in accordance with transient sensations of fatigue during the exercise bout. The voluntary behavioural change fluctuate pace is therefore a conscious decision based on subconscious physiological feedback from array of peripheral receptors. This suggests that pacing is a mechanism to minimize the conscious sensations of fatigue experienced during exercise, which enables homeostasis to be defended during exercise.

Introduction

The ability to accurately self-pace an exercise bout is a feature of race and time trial performance [START_REF] Abbiss | Models to explain fatigue during prolonged endurance cycling[END_REF][START_REF] St | Evidence for complex system integration and dynamic neural regulation of skeletal muscle recruitment during exercise in humans[END_REF]. Research on pacing strategy during exercise is the 'unexplored territory' in sports performance [START_REF] Foster | Pacing strategy and athletic performance[END_REF]. This statement is especially true in physical education.

Ekkekakis et al. [9] consider that pleasure to signify utility and displeasure to signify danger. Because low-intensities are associated with pleasure, it tends to evoke approach reactions. On the opposite high intensities tend to evoke withdrawal reactions because it is associated with displeasure [9]. Indeed, when an athlete selects high exercise intensity, he must also accept that the sensation of effort will have to increase progressively until the finish line. This requires that the motivation level is sufficient in order to maintain the expected power output [START_REF] Baron | Variation and homogeneity in affective responses to physical activity of varying intensities: an alternative perspective on dose-response based on evolutionary considerations[END_REF].

Sports teachers and coaches need for easy tools to measure the motivation of subjects. Unfortunately, measure motivation to continue an exercise despite the occurrence of psychophysiological mechanisms of fatigue is not easy and no psychometric scale was designed for it.

Nevertheless, Gendolla and Richter [START_REF] Gendolla | Effort mobilization when the self is involved: some lessons from the cardiovascular system[END_REF] have proposed that effort refers to the intensity aspect of motivation. But the motivational processes that allow the athlete to control its intensity in relation to the perceived sensations are complex. It is difficult to imagine that the study of a single parameter such as perceived exertion can allow a complete analysis of motivational processes. Thus, we have recently used other emotional parameters in addition to the perceived exertion to better understand the process of pacing strategy during intermittent sprints [START_REF] Baron | Emotional responses during repeated sprint intervals performed on level, downhill and uphill surfaces[END_REF]. These parameters were pleasure, the desire to continue the exercise, the desire to stop the exercise and the available level of resources.

The first aim of the present study was to test whether the use of these parameters may allow an estimation of motivation to continue a tiring exercise.

The second aim of this study was to test the effect of a start to a higher perceived exertion than spontaneously chosen on pacing strategy, emotional regulation and motivation.

It is well known that well-trained athlete have the ability in this complex skill [START_REF] St | The role of information processing between the brain and peripheral physiological systems in pacing and perception of effort[END_REF] whereas inexperienced subjects are unable to pace themselves effectively [START_REF] Buckley | Reliability and validity of measures taken during the Chester step test to predict aerobic power and to prescribe aerobic exercise[END_REF][START_REF] Eston | Reliability of ratings of perceived effort regulation of exercise intensity[END_REF]. Indeed, the process of pacing strategy amounts to make compatible the nature of the task and the personal psycho-physiological capacities [START_REF] Baron | Variation and homogeneity in affective responses to physical activity of varying intensities: an alternative perspective on dose-response based on evolutionary considerations[END_REF]. This process is based on representations. When a subject has no prior experience of a particular exercise, the representations of the task are imprecise because no element of comparison from a prior event is available in the memory. In this context, the expected time to cover a distance cannot be precisely estimated. Likewise, physiological capabilities and the capacity to resist the sensations of fatigue are not yet known. As a result, the optimum pacing strategy cannot be determined either before or during the exercise bout. Herbert et al. [START_REF] Herbert | Interoceptive sensitivity and emotion processing: an EEG study[END_REF][START_REF] Herbert | Interoceptive sensitivity and physical effort: implications for the self-control of physical load in everyday life[END_REF] have shown that there is a strong association between interoceptive sensitivity and the intensity of emotional experience, which corresponds to the quantity of memorised emotions. In accordance, it is argued that cognitive information developed by each training session would reinforce the interoceptive sensitivity and the physiological awareness [START_REF] Baron | Variation and homogeneity in affective responses to physical activity of varying intensities: an alternative perspective on dose-response based on evolutionary considerations[END_REF]. For this reason, self-paced exercises are often used in Physical Education in order to improve the capacity to control exercise intensity in relation with personal psychophysiological capacities.

In a recent study, Foster et al have shown that the pattern of learning the performance template is primarily related to increased confidence that the trial can be completed without unreasonable levels of exertion or injury [START_REF] Foster | Pattern of developing the performance template[END_REF]. Pacing strategies can be thought of as a complex process in which the subject controls the intensity of exercise at any time by taking into consideration physiological and psychological reserves in relation to the estimated time until the finish [START_REF] Garcin | A new rating scale of perceived exertion based on subjective estimation of exhaustion time: a preliminary study[END_REF] at that exercise intensity [START_REF] Baron | Variation and homogeneity in affective responses to physical activity of varying intensities: an alternative perspective on dose-response based on evolutionary considerations[END_REF].

The assumption of Gendolla and Richter [START_REF] Gendolla | Effort mobilization when the self is involved: some lessons from the cardiovascular system[END_REF] is that all our behaviour is guided by the energy conservation principle. Indeed, athlete has to confront the fact that enough energy is mobilized to cope with obstacles in goal attainment process and the fact that enough energy has to be conserved to reduce the probability of depletion and exhaustion.

Accordingly, we hypothesised that this principle would impose that an emotional reserve exists at the end of exercise in school participants when the intensity is self-paced even when maximal performance is asked because the maximal personal capacities are unknown. Indeed, if psycho-physiological process of fatigue could be envisaged as protective mechanisms, it could be hypothesised that pacing strategy would correspond to a protective behaviour in novice. Only experience could induce that this emotional reserve will be reduced, when subject becomes aware that more important effort could be supported for the duration of the task.

We hypothesise that a more important effort than spontaneously mobilized may be supported by the school participants. Moreover, we expect that the method, which consists in imposing a more important effort at the beginning, would improve performance.

Finally, according to St Clair Gibson et al. [START_REF] St | The role of information processing between the brain and peripheral physiological systems in pacing and perception of effort[END_REF], pacing strategy is acquired during adolescence and is a stable process. The pacing strategy is dependent on the pre-established template and considerable time and effort may be required to change a specific strategy that has been followed frequently [START_REF] St | The role of self-talk in the awareness of physiological state and physical performance[END_REF]. St Clair Gibson et al. [START_REF] St | Neural control of force output during maximal and submaximal exercise[END_REF] have suggested that the motor sequences representative of the performance template are almost certainly programmed into the motor cortex from prior athletic performance, potentially from childhood Thus, an interesting possibility is that training methods could be designed, even during childhood, to improve the efficiency and stability of the pacing strategies.

Recently, we showed that emotional responses were controlled during intermittent sprints in order that effort could be maintained until the end whether during level, downhill and uphill running in young adults [START_REF] Baron | Emotional responses during repeated sprint intervals performed on level, downhill and uphill surfaces[END_REF]. Results have shown that the gradient of the running surface did not influence the pattern of emotional responses, which corresponds to a quasi-maximal level of emotional reserve at the beginning and a low level at the end of exercise.

In accordance, we suggest that a pre-established template in emotional responses would exist in school participants. We hypothesize that it would remain constant even when a faster start is imposed at the beginning of the exercise.

Pacing strategies were analysed during 2 exhaustive 3-min runs for a control group and a test group. Effort was measured using Borg's category ratio scale [START_REF] Borg | The increase of perceived exertion, aches and pain in the legs, heart rate and blood lactate during exercise on a bicycle ergometer[END_REF], which consists of 11 statements ranging from 0 to 10 (from "nothing" to "maximum"). This scale was used in order to quantify all the other emotional parameters as previously proposed [START_REF] Baron | Emotional responses during repeated sprint intervals performed on level, downhill and uphill surfaces[END_REF]: that is, the pleasure, the desire to continue, the desire to stop, and the available resources. The affective balance (AB) was calculated as the difference between effort and pleasure [START_REF] Baron | Emotional responses during repeated sprint intervals performed on level, downhill and uphill surfaces[END_REF].

Participants

127 secondary school participants have realized running tests during their sport classes. Participants aged 15.2 ± 1.0 year. They were taught to use the Rating of Perceived Exertion (RPE) scale [START_REF] Borg | The increase of perceived exertion, aches and pain in the legs, heart rate and blood lactate during exercise on a bicycle ergometer[END_REF] to monitor their exercise intensities during precedent classes. Thus, all participants were accustomed to quantifying their individual RPE, but also other emotional parameters [START_REF] Baron | Emotional responses during repeated sprint intervals performed on level, downhill and uphill surfaces[END_REF] for 1 training session when running. Local ethics committee has approved this work.

Procedures

A CONTROL group (56 participants) and a RPE group (71 participants) performed an incremental test (test 1) and 2 exhaustive 3-min runs (tests 2 and 3). During these 3-min runs, participants were asked to realize the most important performance as possible. They were stopped at each 100m for 1 min in order to respond to the emotional questioner. During these arrests, the chronometer was stopped.

The CONTROL group was asked to realize their 2 runs as fast as possible without any other consign. The RPE group was asked to realise the first run with the same consign but has to start the second run at a minimal RPE level corresponding to the average RPE of the first run.

For this, subjects were asked to self-select the intensity which induced the expected RPE. Then, exercise is totally self-paced.

The emotional parameters were collected every 100m. Running tests were performed on a 100m track. The speed was measured every 100m for the firsts 500m. Then, the speed was measured for the last 100m.

Statistical analysis

Calculations were performed using XLSTAT. Standard statistical methods were used for the calculation of mean and standard deviations. Student test was used to determine significant differences of measured variables between each running condition.

ANOVA with repeated measurements was used to compare the changes in parameters during the tests. Normal Gaussian distribution of the data was verified by the Shapiro-Wilks test. Compound symmetry, or sphericity, was verified by the Mauchley test. Multiple comparisons were made with the Tukey HSD post hoc test when the Greenhouse-Geisser epsilon correction factor was > 0.50, or with the Bonferroni post hoc test when the epsilon was < 0.50. The Pearson's coefficient was computed to test linear correlation among variables measured at the end of each repetition.

Statistical significance was set at a level of p = 0.05 for all analyses.

Results

Test 1: Incremental test VAM was 12.40 ± 1.67 km.h -1 for the group CONTROL and 12.14 ± 1.81 km.h -1 for the group RPE.

During the incremental test, effort, pleasure, desire to continue, desire to stop and the level of resources are correlated to intensity (R 2 = 0,65; -0,18; -0,24; 0,41 et -0,47, respectively, P < 0.05).

Test 2 and 3: first and second 3-min run for the group CONTROL and the group RPE

Average distance, speed and emotional parameters of the two groups for the two races were presented in Table 1.

Evolution of self-selected speed

Test 1 group RPE: Self selected speed significantly increased between the start and the finish of the run (p < 0.05) but significantly decreased between the start and the 500m (p < 0.05). Post-hoc tests show significant differences between all measures (Figure 1).

Test 2 group RPE: Self-selected speed significantly increased between the start and the stop of the run (p < 0.05) but did not significantly evolve between the start and the 500m (p < 0.05). Post-hoc tests show significant differences between the 500m and the finish (Figure 2). Test 1 group CONTROL: Self-selected speed significantly increased between the start and the stop of the run (p < 0.05) and between the start and the 500m (p < 0.05). Post-hoc tests show significant differences between all the measures (Figure 3). Test 2 group CONTROL: Self-selected speed significantly increased between the start and the stop of the run (p < 0.05) and between the start and the 500m (p < 0.05). Post-hoc tests show significant differences between all the measures (Figure 4). Test 2 group RPE: Effort, affective balance and desire to stop significantly increased between the first and the last repetition (5.02 ± 1.42 vs 7.87 ± 2.19, p < 0.05; -1.57 ± 2.67 vs 4.59 ± 2.82, p < 0.05; 2.14 ± 2.49 vs 6.15 ± 3.4, p < 0.05, respectively), whereas pleasure, desire to continue and available resources significantly decreased during running (6.59 ± 3.19 vs 3.28 ± 2.96, p < 0.05; 6.87 ± 3.11 vs 3.19 ± 3.00, p < 0.05; 8.27 ± 2.06 vs 3.45 ± 2.96, p < 0.05, respectively).

Relations between time and emotional parameters

Test 1 group CONTROL: Effort, affective balance and desire to stop significantly increased between the first and the last repetition (1.86 ± 1.57 vs 5.29 ± 2.77, p < 0.05; -6.1 ± 2.57 vs -0.5 ± 2.5, p < 0.05; 0.93 ± 1.54 vs 3.71 ± 2.93, p < 0.05, respectively), whereas pleasure, desire to continue and available resources significantly decreased during running (7.96 ± 3.00 vs 5.79 ± 3.30, p < 0.05; 8.59 ± 2.37 vs 5.95 ± 3.23, p < 0.05; 8.79 ± 1.99 vs 5.82 ± 3.16, p < 0.05, respectively). Each parameter was correlated with time in each group and each test of running. During the first 3-min test of the group RPE, the duration of exercise was significantly correlated with effort, pleasure, affective balance, desire to continue, desire to stop and available resources (0.70, -0.36, 0.58, -0.43, 0.44 and -0.52; respectively; p < 0.05).

During the second 3-min test of the group RPE, the time was significantly correlated with effort, pleasure, affective balance, desire to continue, desire to stop and available resources (0.47, -0.32, 0.45, -0.35, 0.39 and -0.52; respectively, p < 0.05).

During the first 3-min test of the group CONTROL, the time was significantly correlated with effort, pleasure, affective balance, desire to continue, desire to stop and available resources (0.50, -0.29, 0.43, -0.33, 0.42 and -0.39; respectively, p < 0.05).

During the second 3-min test of the group CONTROL, the time was significantly correlated with effort, pleasure, affective balance, desire to continue, desire to stop and available resources (0.34, -0.22, 0.31, -0.27, 0.23, -0.26; respectively, p < 0.05).

For the CONTROL group, the slope of the relation between the time and the evolution of effort, pleasure, affective balance, desire to continue and available resources were significantly different between the first and the second 3-min run (0.04 ± 0.03 vs 0.02 ± 0.02, -0.03 ± 0.02 vs -0.02 ± 0.02, 0.06 ± 0.04 vs 0.04 ± 0.03, -0.03 ± 0.02 vs 0.02 ± 0.03, -0.04 ± 0.03 vs -0.02 ± 0.03; respectively, p < 0.05) whereas results were not significantly different for desire to stop (0.03 ± 0.03 vs 0.02 ± 0.03; p = 0.117). For the RPE group, the slope of the relation between the time and the evolution of effort, affective balance were significantly different between the first and the second 3-min run (0.06 ± 0.03 vs 0.03 ± 0.02, 0.10 ± Participants. J Exerc Sports Orthop 2(2): 1-9.

Pacing Strategies and Emotional Pattern During Intermittent 3-min runs in Secondary School Participants

Copyright: © 2015 Baron et al.

0.06 vs 0.07 ± 0.05; respectively, p < 0.05) whereas results were not significantly different for pleasure, desire to continue, desire to stop and available resources (-0.04 ± 0.04 vs -0.04 ± 0.03, -0.04 ± 0.04 vs -0.04 ± 0.03, 0.05 ± 0.04 vs 0.05 ± 0.04, -0.06 ± 0.03 vs -0.05 ± 0.03; respectively, p > 0.05).

For the CONTROL group, the Y-intercept of the relation between the time and the evolution of effort was significantly different between the first and the second 3-min run (1.04 ± 1.80 vs 1.37 ± 1.76; p < 0.05) whereas results were not significantly different for pleasure, affective balance, desire to continue, desire to stop and available resources (8.56 ± 3.11 vs 8.86 ± 2.72, -7.52 ± 3.89 vs -7.48 ± 3.52, 9.33 ± 2.42 vs 9.69 ± 1.51, 0.28 ± 1.84 vs 0.05 ± 1.30, 9.57 ± 2.15 vs 9.80 ± 1.41; respectively, p > 0.05). For the RPE group, the Y-intercept of the relation between the time and the evolution of effort and affective balance, were significantly different between the first and the second 3-min run (0.70 ± 1.79 vs 4.35 ± 1.72, -6.17 ± 5.36 ± -2.94 ± 4.39; respectively, p < 0.05) whereas results were not significantly different for pleasure, desire to continue, desire to stop and available resources (6.94 ± 4.41 vs 7.28 ± 3.66, 7.54 ± 4.07 vs 7.78 ± 3.52, 0.98 ± 3.19 vs 1.30 ± 2.98, 8.86 ± 3.52 vs 9.19 ± 2.52; respectively, p > 0.05).

Relations between speed and emotional parameters

The evolution of speed was not correlated with the evolution of emotional for any run and any group (p > 0.05).

Discussion

Incremental test

The results of the incremental test show that all the emotional parameters were correlated with the intensity whereas participants were accustomed to these scales for 1 training session, highlighting that these parameters are of interest to objectify the occurrence of fatigue.

Performance and motivation during the 3-min runs

The results of the group CONTROL show that the performance of the second 3-min run was no different of the first 3-min run whereas the comparison of the emotional parameters attests that a more important emotional reserve exist during the second run. Indeed, the average levels of effort, affective balance and desire to stop were lower whereas the average levels of pleasure, desire to continue and personal resources were higher. This could be explained by the effect of training or because participants were accustomed to this event by the first 3-min run. But it is important to keep in mind that participants were asked to realise the most important performance during the 2 running sessions. Results highlight that when participants confront the fact that enough energy is mobilized to cope with obstacles in goal attainment process and the fact that enough energy has to be conserved to reduce the probability of depletion and exhaustion, the most important parameter of the strategy is energy conservation in accordance with the theory of Gendolla and Richter [START_REF] Gendolla | Effort mobilization when the self is involved: some lessons from the cardiovascular system[END_REF]. It could be hypothesised that a representation of individual level of performance is developed during the first 3-min run and that even if a more important emotional reserve is observed; the level of investment is not improved in order to realise a better performance.

The results of the group RPE show that when a more important effort is imposed at the beginning of the second 3-min run, a greater distance was run. At first, this result seems obvious. But again, it is important to keep in mind that participants are allowed to pace the runs, as they wanted. Thus, they could choose to reduce or less increases the level of effort after the start. The results suggest that the performance was higher during the second run in group RPE because the emotional reserve is lower than in the first run. If effort refers to the intensity aspect of motivation [START_REF] Gendolla | Effort mobilization when the self is involved: some lessons from the cardiovascular system[END_REF], it could be considered that the motivation

Pacing Strategies and Emotional Pattern During Intermittent 3-min runs in Secondary School Participants

Copyright: © 2015 Baron et al.

during the second run of group RPE was higher. Indeed, the average level of effort, affective balance and desire to stop were higher during the second run when compared with the first race.

According to Locke and Latham [START_REF] Locke | A theory of goal setting and task performance[END_REF] motivation was less intense if people performed tasks without clear performance standard ("do-your-best") than when they performed a difficult task, that is, a task with clear and high performance standard. But resources are mobilized only if success is possible (i.e., not too difficult) and worthwhile (i.e., justified by the importance of success) [START_REF] Gendolla | Effort mobilization when the self is involved: some lessons from the cardiovascular system[END_REF].

In RPE group, starting the second run at average level of effort observed during the first run, apparently did not exceed the potential motivation, which is the maximum effort a person is (potentially) willing to mobilize for accomplishing a goal-that is the amount of justified effort [START_REF] Gendolla | Effort mobilization when the self is involved: some lessons from the cardiovascular system[END_REF]. Potential motivation is determined by the importance of success. The more important is succeeding, the more effort is justified.

In non-experts school participants, the knowledge of their capacity to realize the run is limited and underestimated. For this reason, the emotional reserve is important during the first run. Our results suggest that the instruction of the second run seems reinforcing the belief that the goal of a more important performance can be achieved. Because performance has direct consequences for individuals' self-definition and self-esteem [START_REF] Gendolla | Effort mobilization when the self is involved: some lessons from the cardiovascular system[END_REF], a more important effort is consented.

Nevertheless, even in this condition, emotional reserve is still observed and more important level of effort could have been prescribed to the participants.

Pacing strategies during the 3-min runs

While there are an infinite number of possible pacing strategies that a subject may adopt during a run, four categories have been described by Foster et al [START_REF] Foster | Pacing strategy and athletic performance[END_REF], an even paced strategy, a slow start with an increase through the event. A variable paced strategy, a strategy in which the intensity is increased during the event. The last is the all-out pacing strategy in which the athlete begins at the maximal possible pace and attempts to continue. It is probably the most difficult strategy, which requires experience because the slightest mistake in the intensity at the start can induce the occurrence of a premature and catastrophic fatigue. There appears to be no clear optimal pacing strategy identified by previous research, and it may be that each individual has uniquely optimal pacing strategy [START_REF] St | The role of information processing between the brain and peripheral physiological systems in pacing and perception of effort[END_REF]. Nevertheless, modelling studies have already shown that all-out performance is optimal for sprint cycling whereas benefits of a relatively fast start seem to overweigh the negative consequences of the uneven velocity profile for 1500m [START_REF] De Koning | Determination of optimal pacing strategy in track cycling with an energy flow model[END_REF][27][28]. For longer distances (4000m), a relatively even-paced pattern appears optimal [START_REF] De Koning | Determination of optimal pacing strategy in track cycling with an energy flow model[END_REF].

In our study, the strategy, which consists in a slow start with an increase of speed at the end, could be observed, for each test of each group. This is principally explained by the increase of speed between 500m and the last 100m of the runs. It is more interesting to observe the evolution of speed between the start and the 500m.

The common factor that is observed when the exercise is totally self-paced (first and second runs of group CONTROL and first run of group RPE) is that fluctuations of running intensities exist between the start and the 500m of exercise in untrained school participants. When a more important effort is imposed at the beginning (second run of RPE group), the intensity did not significantly evolve during this interval. It is of great interest because this strategy is known to be efficient in long duration sport events [START_REF] St | The role of information processing between the brain and peripheral physiological systems in pacing and perception of effort[END_REF]. Moreover, it is probably the first strategy to master because all-out is more difficult. In addition to improved performance, the set used in the second run of RPE group improved the pacing strategy. This is of great interest in nonexperts school participants.

But the fact that the better strategy during middle duration, as 3-min runs, consists to a rapid start with a slight diminution of the speed until the finish line, suggests that a more important effort mobilisation than those corresponding to the average value of the test 1 would be more efficient on performance. The fact that an increase of the running speed was observed between 500m and the end corroborate this hypothesis.

Emotional strategy during the 3-min runs

The most important finding of this study is that the pattern of emotional responses seems to be the same in all conditions. It corresponds to a quasi-maximal level of emotional reserve at the beginning and a low level at the end of exercise. It could be hypothesized that during exercise, participants compare perceived exertion with the maximum effort they are willing to mobilize for accomplishing their goal [9], i.e. more generally the level of emotional responses and the consented level in relation to the remaining time as suggested previously [START_REF] Baron | Variation and homogeneity in affective responses to physical activity of varying intensities: an alternative perspective on dose-response based on evolutionary considerations[END_REF].

Moreover, the results highlight that there is a linear increase in emotional parameters between the start and the end in all conditions. This seems to be the most important foundation of the pattern of emotional regulation when participants were asked to realize the most important performance. Indeed, our results show that emotional pattern corresponded to a linear evolution in emotional parameters during the 2 runs for the 2 groups in the direction of a decrease of emotional reserve between the start and the end of the run whereas the participants were free to pace their runs, as they wanted.

It could be suggested that it is because emotional reserve is decrease throughout the runs that the speed is increased between the start and the end of the tests. Nevertheless, results show that speed was not correlated with emotional parameters for any run and any group. Indeed, we have previously suggested that emotional arousal likely takes longer to develop than do the processes involved in physiological control [START_REF] Baron | Variation and homogeneity in affective responses to physical activity of varying intensities: an alternative perspective on dose-response based on evolutionary considerations[END_REF]. We proposed that a non-conscious physiological process is the most effective when rapid adjustments in power output are needed during short events. We supposed that a conscious process reinforces subconscious controls only during more prolonged exercise. The period of 3-min in these conditions of intermittent exercise appears to be insufficient for emotional regulation impact pacing strategy with significant correlation in school participants.

The results of our previous study [START_REF] Baron | Emotional responses during repeated sprint intervals performed on level, downhill and uphill surfaces[END_REF] show that the pattern of emotional regulation seems to be just translated in relation with the subjective difficulty of the task as proposed by the motivational intensity theory [START_REF] Gendolla | Effort mobilization when the self is involved: some lessons from the cardiovascular system[END_REF]. Indeed, Y-intercepts of the evolution of most of emotional parameters were higher when 10 repeated sprints of 60m were performed on uphill surface when compared with level running. On the contrary, Y-intercepts were lower during downhill sprints. The slopes of the evolution of most of emotional parameters were not influenced by the nature of the running surface. We propose that Y-intercepts could be envisaged as a marker of the subjective difficulty of the exercise.

The results of the present research allowed us to propose the following explanatory hypothesis:

For the group CONTROL, Y-intercepts of all emotional parameters (except effort) were not significantly different between the 2 tests because the 2 runs corresponded to the same duration without any other change in the nature of the task. The slopes of the evolution of all emotional parameters (except for the desire to stop which was not significantly different) were in the way of a smaller decrease of emotional reserve during the second run. It could be explained by the theory of Gendolla and Richter [START_REF] Gendolla | Effort mobilization when the self is involved: some lessons from the cardiovascular system[END_REF] in which the most important parameter of the strategy is energy conservation. Hence, participants were aware to be able to attain the goal during the first run and energy conservation was the most important factor in the dilemma between the fact that enough energy is mobilized to cope with obstacles in goal attainment process and the fact that enough energy has to be conserved to reduce the probability of depletion and exhaustion [START_REF] Gendolla | Effort mobilization when the self is involved: some lessons from the cardiovascular system[END_REF]. Indeed, the body does not mobilize more resources than necessary [START_REF] Gendolla | Effort mobilization when the self is involved: some lessons from the cardiovascular system[END_REF].

For the group RPE, Y-intercepts of all emotional parameters (except effort) were not significantly different between the 2 runs for the same reason. The slopes of all emotional parameters (except RPE) were not significantly between the 2 runs. It could be hypothesized that it is because they were confronted by the same dilemma: enough energy has to be mobilized to cope with obstacles in goal attainment process but enough energy has to be conserved to reduce the probability of depletion and exhaustion. Obstacles in goal attainment process of the second run are new because the instruction was different (faster start), imposing that level of motivation was not lower than during the first test.

Estimation of Motivation

The aim of this study was not to understand the process of giving participants a reason for running so fast but rather how measuring the level of motivation which is necessary to run so fast.

According to Gendolla and Richer [START_REF] Gendolla | Effort mobilization when the self is involved: some lessons from the cardiovascular system[END_REF], effort refers to the intensity of motivation. But in this case, our results should be interpreted in the sense of an increase of motivation during the test, despite the occurrence of fatigue. It would also mean that participants would be more motivated when a more fast start was asked. It seems in contradiction with logic and field observations. Rather, we proposed using other parameters to estimate the level of motivation.

We define the motivation to pursue a tired exercise as the level of acceptance of effort. The more the motivation is, the more the level of consented effort is. On the contrary, when the motivation is down, subject would not support a high level of effort. Thus, we propose that the ratio between the desire to continue the exercise and the level of effort could be used in order to estimate the motivation to pursue a tired exercise. Logically, this parameter would decrease during exercise with the occurrence of fatigue.

In accordance, our results show that this ratio decreased with time during the 3-min tests in all conditions. Moreover, this ratio was lower when a more important effort was asked at the beginning of the test (test 2 vs test 1 for RPE group) whereas it was higher when the self paced run was repeated for the second time, associated with a higher pleasure to run (test 2 vs test 1 for the CONTROL group).

Conclusion

Whereas the role of motivation is of great importance in sport performance, little is known about how to measure it during exercise. We propose that the ratio between the desire to continue the exercise and the level of effort could be used in order to estimate the motivation to pursue a tired exercise.

Whereas training programs are often designed in order to develop physiological resources, this study shows that the performance has been immediately improved by imposing a more important effort mobilization at the start without the occurrence of a catastrophic failure. Performance has been improved because a more important part of the emotional reserve has been used. Whereas many training sessions are needed in order to develop performance through an increase of physical condition, only one session was needed to improve performance with this method.

Figure 1 :

 1 Figure 1: Evolution of self-selected speed during the first 3min run of the group RPE when speed is totally self-paced: *: Significant evolution (p < 0.05); ns: not significantly evolution (p > 0.05).

Test 2

 2 group CONTROL: Effort, affective balance and desire to stop significantly increased between the first and the last repetition (1.93 ± 1.62 vs 4.02 ± 2.46, p < 0.05; -6.57 ± 2.20 vs -2.98 ± 2.78, p < 0.05; 0.52 ± 1.08 vs 2.53 ± 2.71, p < 0.05, respectively), whereas pleasure, desire to continue and available resources significantly decreased during running (8.50 ± 2.63 vs 7.00 ± 3.04, p < 0.05 ; 9.29 ± 1.40 vs 7.60 ± 2.66, p < 0.05 ; 9.53 ± 1.29 vs 7.38 ± 2.68, p < 0.05, respectively).Participants. J Exerc Sports Orthop 2(2): 1-9.Pacing Strategies and Emotional Pattern During Intermittent 3-min runs in Secondary School ParticipantsCopyright: © 2015 Baron et al.

Figure 2 :

 2 Figure 2: Evolution of self-selected speed during the second 3min run of the group RPE when speed is self-paced but the start has to be at least equal to the average RPE of the test 1: *: Significant evolution (p < 0.05); ns: not significantly evolution (p > 0.05).

Figure 3 :

 3 Figure 3: Evolution of self-selected speed during the first 3min run of the group CONTROL when speed is totally self-paced: *: Significant evolution (p < 0.05); ns: not significantly evolution (p > 0.05).

Figure 4 :

 4 Figure 4: Evolution of self-selected speed during the second 3min run of the group CONTROL when speed is totally self-paced: *: Significant evolution (p < 0.05); ns: not significantly evolution (p > 0.05).

Pacing Strategies and Emotional Pattern During Intermittent 3-min runs in Secondary School Participants Copyright: © 2015 Baron et al. First race group CONTROL Second race group CONTROL First race group RPE Second race group RPE

	Distance (m)	737.00 ± 122.88	745.53 ± 144.61 ns	702.11 ± 127.81	796.83 ± 135.22* (+13.5%)
	Speed (km.h -1 )	14.74 ± 2.45	14.91 ± 0.80 ns	14.04 ± 2.70	15.93 ± 106.1* (+13.5%)
	Speed (%age VAM)	118.80 ± 13.28	120.36 ± 18.86 ns	115.83 ± 14.01	131.53 ± 14.30* (+13.5%)
	effort	3.47 ± 2.34	2.75 ±8.04*	4.19 ± 2.60	6.04 ± 1.97*
	pleasure	7.09 ± 3.1	8.04 ± 2.61*	5.14 ± 3.40	5.42 ± 3.29 ns
	Affective balance	-3.62 ± 4.25	-5.29 ± 3,56*	-0.94 ± 5.15	0.61 ± 4.40*
	desire to continue	7.52 ± 2.81	8.62 ± 1.93*	5.30 ± 3.32	5.65 ± 3.34 ns
	desire to stop	2.07 ± 2.30	1.29 ± 1.83*	3.47 ± 3.14	3.60 ± 3.14 ns
	Available resources	7.48 ± 2.67	8.52 ± 1.96*	5.79 ± 3.08	6.08 ± 2.91*
	Desire to continue / effort	4.46 ± 3.61	5.47 ± 3.58*	2.18 ± 2.48	1.10 ± 0.78*
			Test 1 group RPE: Effort, affective balance and desire to stop
			significantly increased between the first and the last repetition
			(1.73 ± 1.37 vs 7.41 ± 2.15, p < 0.05; -4.62 ± 2.70 vs 4.27 ± 2.27, p
			< 0.05; 1.85 ± 2.50 vs 6.02 ± 3.24, p < 0.05, respectively), whereas
			pleasure, desire to continue and available resources significantly
			decreased during running (6.35 ± 3.69 vs 3.14 ± 2.63, p < 0.05;
			6.82 ± 3.25 vs 2.89 ± 2.51, p < 0.05 ; 7.80 ± 2.93 vs 3.17 ± 2.53, p <
			0.05, respectively).

Participants. J Exerc Sports Orthop 2(2): 1-9.

Table 1 :

 1 Average distance, absolute speed (km.h -1 ), relative speed (%age VAM), effort (RPE), pleasure (P), desire to continue (DC), desire to stop (DS), personal resources to realized the run (R) and the ratio between the desire to continue and the effort for the group CONTROL and group RPE during the first and the second races (maximal performance was asked for the 2 groups during 2 races. During the test 1 the 2 groups totally freely control the speed. During the test 2, the group RPE has to start at least at the RPE which corresponds to the average value of the test 1 whereas the group CONTROL totally control the speed all around the run.

*: Significant difference with test 1 (p < 0.05). ns: not significantly different with test 1 (p > 0.05).


R I C H A R D Sempi~ri~

LOW MOLECULAR WEIGHT DICARBOXYLIC ACIDS AND RELATED POLAR COMPOUNDS IN THE REMOTE MARINE RAIN SAMPLES COLLECTED FROM WESTERN PACIFIC

Keywords: c~, co-dicarboxylic acids, ketoacids, ct-dicarbonyls, TOC, rainwaters, western Pacific

During the western Pacific Ocean cruise of R/V Hakuho-Maru (20°N-40°S), fourteen rainwater samples were collected. They were studied by a capillary gas chromatography (GC) and GComass spectrometry (GC/MS) for the molecular distributions of Cz-C1 o ~, og-dicarboxylic acids and related polar compounds, i.e. ketoacids (C2-C9) and ct-dicarbonyls (C2-C3). Samples were also analysed for dissolved (DOC) and total organic carbon (TOC). Total diacid concentration range was 36-959 # g : -i and accounted for 3 % (av.) of TOC (1.2-2.5 mgC/-1), which is much higher than the previous numbers found in Tokyo rain samples (av. 1%). This indicates that low molecular weight diearboxylic acids are an important class of organic compounds in the marine rains. All the samples showed that the smallest diacid (oxalic acid) which comprised 50% of the total diacids was the most abundant followed by malonic (Ca) or succinic acid (C4). The shorter chain diacids (C2-C4) accounted for 63-90% (av. 80%) of total diacids and their relative abundances increase from the Northern to the Southern Hemisphere. These results suggest that shorter chain diacids are in part produced in the marine atmosphere by photochemical oxidation of organic matter through the intermediates such as ketoacids and dicarbonyls. The major portion of diacids and their precursors is probably derived from the Asian and Australian continents by a long-range transport.

These water soluble compounds have been found at significant concentrations in wet precipitations from various locations [START_REF] Lunde | Organic micropollutants in precipitation in Norway[END_REF][START_REF] Norton | Tropospheric oxalate[END_REF][START_REF] Likens | The composition and deposition of organic carbon in precipitation[END_REF][START_REF] Kawamura | Organic compounds in the rainwater of Los Angeles[END_REF][START_REF] Kawamura | Capillary GC determination of short-chain dicarboxylic acids in rain, fog, and mist[END_REF]. However, to our knowledge, only few rainwater analyses were conducted by the use of BF3/n-butanol derivatization technique followed by gas chromatography (GC) determination which provides the molecular distributions of a homologous series of diacids (C2-Clo) (Semp6r6 and [START_REF] Setup&6 | Comparative distributions of dicarboxylic acids and related polar compounds in snow, rain and aerosols from urban atmosphere[END_REF]. At this time and among other techniques this method allows better recoveries especially for shorter chain diacids and permits the detection of co-oxocarboxylic acids (Cz-Clo), pyruvic acid and ~t-dicarbonyls (C2-C3) as well [START_REF] Kawamura | Distributions of low molecular weight dicarboxylic acids in the North Pacific aerosol samples[END_REF][START_REF] Kawamura | Identification of C2 Clo ~-oxocarboxylic acids, pyruvic acid, and C2-C3 ct-dicarbonyls in wet precipitation and aerosol samples by capillary GC and GC/MS[END_REF]. These results indicated that among these water soluble compounds, shorter chain diacids, particularly oxalic acid, are the most abundant in the urban [START_REF] Kawamura | Motor exhaust emissions as a primary source for dicarboxylic acids in Los Angeles ambient air[END_REF][START_REF] Kawamura | Seasonal changes in the distribution of dicarboxylic acids in the urban atmosphere[END_REF]Semp6r6 and Kawamura, 1994;Khawaja, 1995) and marine aerosols [START_REF] Kawamura | Distributions of low molecular weight dicarboxylic acids in the North Pacific aerosol samples[END_REF].

Determination of specific compounds in wet precipitations such as dicarboxylic acids can contribute 1609 AE 30:lOlll-F Texte Sempéré, R., Kawamura, K., (1996) Low molecular weight dicarboxylic acids and related polar compounds in the remote marine rain samples collected from western Pacific. Atmospheric Environment 30, 1609-1619. https://doi.org/ 10.1016/1352-2310(95)00436-X. to a better understanding of the transport of organic matter in the marine troposphere as well as to the heterogeneous oxidative processes such as oxidation/ reduction of iron in the atmosphere (Zuo andHoign6, 1992, 1994;[START_REF] Hoign6 | Photochemical reactions in atmospheric waters: role of dissolved iron species[END_REF], Moreover, L M W diacid emission and production represent a potential source of cloud condensation nuclei (Semp6r6 and [START_REF] Setup&6 | Comparative distributions of dicarboxylic acids and related polar compounds in snow, rain and aerosols from urban atmosphere[END_REF]. However, only a few studies have been conducted on L M W diacids in remote marine atmosphere and there are no available data on the composition of C2-Clo ~, ~o-dicarboxylic acids and related polar compounds in rains for such environments. In this paper we report t h e detailed distribution of the L M W dicarboxylie acids, ketoacids and dicarbonyls in the marine rainwater samples collected from western Pacific Ocean. We discuss the sources of these compounds and formation mechanisms.

EXPERIMENTAL

Collection of rain samples

Fourteen rainwater samples (RI-R14) were collected at the upper deck of R/V Hakuho Maru (c. 14m above the sea surface) during the KH92-4 cruise: August-October 1992. The cruise track is shown in Fig. 1. Rainwater samples were collected in a pre-cleaned brown glass bottle using a stainless steel rain collector with a cross-section of 2800 cm 2 and protected from biodegradation with HgCI2 during sample collection. Sample storage was done at 4°C in darkness. The collected rainwater volumes and duration of rain ranged from 0.08 to 3.8 ~ and from 1 to 25.8 h, respectively. Table 1 presents sample informations.

Determination of dicarboxylic acids and related compounds by GC and GC/MS

Rain samples (100-150 ml) were concentrated by a rotary evaporator under a vacuum and dried in a nitrogen stream. The dried samples were then reacted with 14% borontrifluoride (BF3) in n-butanol (0.3 ml) to derive carboxyl and e~ 0.

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aldehyde groups to the butyl esters and dibutoxyacetals, respectively. The derivatives were extracted with n-hexane (5 ml) in the presence of an organic free pure water (3 ml) and acetonitrile (0.3 ml) and the extracts were washed with the pure water (3 ml x 2). The derivatives were concentrated to 50/A and determined with a Hewlett-Packard (HP 5890) gas chromatograph (GC) equipped with a split/splitless injector, a HP-5 fused silica capillary column (0.32 mm i.d. × 25m x 0.52/~m), and an FID detector. Identification of the derivatives was performed by a comparison of GC retention times with those of authentic standards. Identification of diacids and ketoacids was confirmed by a GC/MS (Finnigan-MAT ITS-40).

Recoveries of oxalic acid were 70% whereas those of malonic, succinic and adipic acids were 77, 86 and 90%, respectively. Procedural blanks run with organic free pure water showed only small peaks of oxalic, pyruvic and phthalic acid derivatives in the GC chromatograms; they presented less than 4% of the actual samples• Analytical errors in the determination of diacids were within 5% for dicarboxylic acids, 15% for ketoacids, 7% for glyoxal and 26% for methylglyoxal based on duplicates analysis of the rain sample R1. The concentrations of the acids presented here are corrected for the procedural blanks• The organic free water was prepared by boiling Milli Q water with KMnO4 to oxidise organic impurities followed by subsequent distillation•

Measurement of DOC and TOC in rain samples

Wet precipitation samples were gently filtered with an allglass filter holder through a pre-heated (500°C) Pallflex quartz fibre filter. An aliquot of unfiltered and filtered samples were taken in the pre-heated (450°C) glass screw vials (10 ml) with a Teflon lined cap. After acidification (pH < 2) with 1.2 M HC1 solution (50/~1), the samples were bubbled with pure nitrogen gas for 5 min to purge inorganic carbon. The water sample (20-50/A) was injected to a Shimadzu TOC-500 carbon analyser with a combustion column packed with a quartz wool impregnated with platinum. Injections were repeated five times for each sample. The data sets having the highest and lowest values were discarded, whereas the remaining three values were averaged and used for TOC and DOC calculation• The analytical precision of the procedure was within 2%. Particulate organic carbon (POC) was calculated by the difference between TOC and DOC values. The carbon blank of the water used for the standard solutions was estimated to be 120 ttg by injections of different amount of pure water (10-50/d) and subtracted for the standards. Unfortunately, we lost some samples for TOC measurements and are able to present only four remote marine (R3, R12 and R13 and R14) rainwater samples (Table 1).

RESULTS AND DISCUSSION

TOC, DOC and POC in rain samples

Table 1 gives results of total and dissolved organic carbon contents in the rain samples as well as precipitation data. T O C concentrations were found to be 1.2-2.5 m g C f -1 (n = 4; av. 1.6 + 0.6). By contrast, previous results from Tokyo rains (Semp6r6 and K a w a m u r a , 1994) showed higher T O C values ranging from 1.2 to 15.4 m g C f -1. Rain organic matter collected from remote sites probably originated from the continent-derived dusts and gases t h r o u g h long-range atmospheric transport [START_REF] Simoneit | Organic matter in eolian dusts over the Atlantic Ocean[END_REF][START_REF] Duce | Inputs of organic matter to the ocean[END_REF][START_REF] Atlas | Global transport of organic pollutants: Ambient concentrations in the remote marine atmosphere[END_REF][START_REF] Gagosian | Atmospheric transport of continentally derived lipids to the tropical North Pacific[END_REF]Gagosian et al., , 1987; K a w a m u r a and Gagosian, 1987) also from the ocean itself by direct sea-air gas exchange [START_REF] Liss | Processes of gas exchange across an airwater interface[END_REF]Ratte et al., 1993) as well as by sea-salt spray and bubble bursting mechanisms [START_REF] Woodcock | Salt nuclei in marine air as a function of altitude and wind force[END_REF][START_REF] Barger | Surface active organic material in the marine atmosphere[END_REF][START_REF] Marty | Relationship between the lipid compositions of marine aerosols, the sea surface microlayer and subsurface water[END_REF]. Organic carbon in the precipitation was found mostly in the dissolved form (av. DOC % in TOC = 92 _ 3, see Table 1) being similar to the number (70--99%) reported for continental rains (urban and rural) [START_REF] Liljestrand | Spatial variations of acid precipitations in Southern California[END_REF][START_REF] Likens | The composition and deposition of organic carbon in precipitation[END_REF][START_REF] Kawamura | Organic compounds in rainwater[END_REF]Semp6r6 and Kawamura, 1994). However, the 'dissolved' phase was here operationally defined as those passing through the quartz fibre filter (effective retention=0.5 #m) thus, besides gaseous and truly dissolved organic compounds, rain DOC may comprise a continuum of small particles in colloidal size range as well. As seen in Table 1, TOC values are generally higher when rainfall intensity is low, indicating that weaker rains scavenge organic materials more efficiently per unit of precipitation volume. Based on our limited numbers of TOC measurements, organic carbon flux was calculated to range from 0.31mgCm-2h -1 (duration of 25.8 h) to 17.8 mgCm -2 h-~ (duration of 1 h). For Enewetak Atoll rain samples (western North Pacific) which showed similar DOC values, [START_REF] Zafiriou | Air-to sea fluxes of lipids at Enewetak Atoll[END_REF] estimated the wet plus dry deposition flux of 0.63gCm-2yr -1, being in the same order of magnitude as the flux of organic carbon to the deep sea in the north central Pacific Ocean [START_REF] Smith | Food energy supply and demand: a discrepancy between particulate organic carbon flux and sediment community oxygen consumption in the deep ocean[END_REF]. These results suggest that rainwaters may provide locally and temporally significant amount of organic carbon to the surface seawater in the Pacific Ocean.

Identification and origin of dicarboxylic acids, ketoacids and dicarbonyls in rain samples

Figure 2 shows a reconstructed total ion chromatogram of derivatives of dicarboxylic acids, ketoacids and dicarbonyls isolated from the rain sample R13. A homologous series of straight-chain saturated (C2-Clo) dicarboxylic acids were identified in all the samples together with branched-chain (iso) saturated (methylmalonic: C4, methylsuccinic: C5), aliphatic unsaturated (maleic: cis C4; fumaric: trans C4), aromatic (phtbalic: Ca), oxo (oxomalonic: C3; 4-oxopimelic: C7) and hydroxy (malic: C4) diacids. The distribution of normal saturated diacids is generally characterised by a predominance of oxalic acid followed by either malonic (C3) or suconic (C4) acid. The diacids with more carbon numbers are less abundant (Fig. 2). Interestingly, similar chain-length distribution has been reported in urban rain and snow/sleet samples (Semp6r6 and [START_REF] Setup&6 | Comparative distributions of dicarboxylic acids and related polar compounds in snow, rain and aerosols from urban atmosphere[END_REF]. Dicarboxylic acids have been considered to be mainly produced by secondary photochemical reactions occurring on anthropogenic and natural organic compounds (Grosjean et al., 1978;[START_REF] Grosjean | Formation of organic aerosols from cyclic olefins and diolefins[END_REF][START_REF] Yokouchi | Characterization ofqoolar organics in airborne particulate matter[END_REF][START_REF] Kawamura | Atmospheric transport of soil-derived dicarboxylic acids over the North Pacific Ocean[END_REF] as well as direct emission from incomplete oxidation of fossil fuels during combustion processes [START_REF] Kawamura | Motor exhaust emissions as a primary source for dicarboxylic acids in Los Angeles ambient air[END_REF]. In the marine atmosphere, C6-C 11 diacids with a predominance of C9 are produced by the photooxidaticn of biogenic unsaturated fatty acids [START_REF] Kawamura | Implications of co-oxocarboxylic acids in the remote marine atmosphere for photo-oxidation of unsaturated fatty acids[END_REF].

In addition to diacids, low molecular weight ketoacids and dicarbonyls were also detected in the rain samples. The ketoacids detected include pyruvic acid (Ca) and a hornologous series of co-oxocarboxylic acids (C2-C9). The group of dicarbonyls includes glyoxal (C2) and methylglyoxal (Ca). Dicarbonyls may be intermediates in the photochemical oxidation reactions of aromatic hydrocarbons to oxalic acid [START_REF] Norton | Tropospheric oxalate[END_REF]. Diacids are c. 9 times more abundant than kctoacids which are considered as some of their precursors. On the other hand, a previous study reported a lower diacid/ketoacid ratio for snow/sleet (3) and rain (5) samples collected in Tokyo area (Semp6r6 and [START_REF] Setup&6 | Comparative distributions of dicarboxylic acids and related polar compounds in snow, rain and aerosols from urban atmosphere[END_REF]. Some ketoacids (e.g. ~o-oxoacids) are probably intermediate products in the photochemical oxidations of organic compounds such as unsaturated fatty acids which also produce dicarbcxylic acids [START_REF] Kawamura | Implications of co-oxocarboxylic acids in the remote marine atmosphere for photo-oxidation of unsaturated fatty acids[END_REF]. Therefore, it is likely that stronger photochemical oxidative processes are responsible for higher diacid/ketoacid ratios found in the marine rainwaters than in the continental rains.

Concentration lewis of diacids, ketoacids and dicarbonyls in the western Pacific rainwaters

Table 2 gives concentrations of individual diacid as well as ketoacid and dicarbonyl in wet precipitation samples. Concentration range of total dicarboxylic acids (C2-Clo) was 35.9-959 #g#-i (av. 237 #g f-1) which is similar to those reported for the urban rains (12.2-538#g~ -1, av. 186#g~-1; Semp6r6 and [START_REF] Setup&6 | Comparative distributions of dicarboxylic acids and related polar compounds in snow, rain and aerosols from urban atmosphere[END_REF] Significantly high concentrations (93.2-626/~g E-~) were obtained for rain samples collected in the western South Pacific (R6--R13; Fig. 3) and close to the equator (R5; 148/~g~-1). The highest concentration (959#gf -~) was obtained for the sample (R1) collected in the North Pacific. This area is known to receive high input of windblown dust from the deserts in China [START_REF] Duce | The atmospheric input of trace species to the world ocean[END_REF]. However, the diacids accounted for 1-5% (av. 3%) of DOC in the remote marine rainwaters being c. 3 times higher than those (0.3-2%; av. 1%) reported in the urban rains (Semp6r6 and [START_REF] Setup&6 | Comparative distributions of dicarboxylic acids and related polar compounds in snow, rain and aerosols from urban atmosphere[END_REF]. These results are consistent with our aerosol studies (Semp6r6 and Kawamura, in pr,~ss) and suggest that dicarboxylic acids detected in lhe western Pacific atmosphere are significantly produced in the marine atmosphere probably by the photochemical oxidation of various organic compounds including hydrocarbons, aldehydes and carboxylic acids. Based on precipitation data, a flux of the diacids was calculated to range from 4.51 to 487 #gm-2h -1, (av. 122 # g m -2 h -1).

Ketoacid concentration range is 3.51-106/zg~ -1 (av. 29.4 #g ¢-1) being in the same order of magnitude as those reported in continental rain samples from Tokyo (3.73-93.5 pgf-1; av. 40.4/~g~ -1). The highest value was observed in the South Pacific sample (R10:106/~g ~-1). This feature was mainly due to the high content of pyruvic acid (87.2/1gf -1) whereas oJ-oxoacids showed a concentration maximum in the Rll sample (32.1 #gE-1). Total ketoacids accounted for 0.2-0.6% (av. 0. 4%) of DOC which is higher than the value found for Tokyo rainwater samples (0.06--0.6%: av. 0.3%; Semp6r6 and [START_REF] Setup&6 | Comparative distributions of dicarboxylic acids and related polar compounds in snow, rain and aerosols from urban atmosphere[END_REF], being consistent with the case of diacid considerations. Flux of ketoacids was calculated to range from 0.59 to 82.2 #gm-Zh -1 (av. 21.3 #gm-2h-1).

Concentrations of dicarbonyls were lower than diacids as well (Table 2; Fig. 3): their concentration range is 0.69-37.8 #g ~-1 (av. 11.8 #g E-i) being in the same order of magnitude with that reported for the Tokyo rain samples (0.57-88.8 #g ~-1; av. 28.1/~gC-1). They accounted for 0.1-0.7% (av. 0. 4%) of DOC which is twice the value reported for the Tokyo rains (Semp6r6 and [START_REF] Setup&6 | Comparative distributions of dicarboxylic acids and related polar compounds in snow, rain and aerosols from urban atmosphere[END_REF]. Higher dicarbonyl concentrations were observed in the samples collected in the higher latitudes of the Southern Hemisphere (e.g. R11-R13 : 16.3-37.8/~g~-1). Glyoxal was more abundant than methylglyoxal in the South Pacific and vice versa in the North Pacific. Based on the concentration and precipitation data, a flux of the dicarbonyls was calculated to range from 0.20 to 42.2#gm-2h -1 (av. 10.6#gm-Eh-1).

Molecular distribution of dicarboxylic acids, ketoacids and dicarbonyls in the western Pacific atmosphere

The molecular distributions of dicarboxylic acids in the western Pacific rainwaters were characterised by a predominance of shorter chain diacids. Oxalic acid (C2) was the most abundant species comprising 39-64% (av. 50%) of the total diacids detected (Table 3, Fig. 4a). Preferential photochemical production of oxalic acid has been observed in the urban atmosphere where its concentration is well correlated with oxidant concentrations [START_REF] Kawamura | Seasonal changes in the distribution of dicarboxylic acids in the urban atmosphere[END_REF]. Oxalic acid produced by the oxidation of many precursors containing carbon number > C 2 is an end product of the photochemical oxidation reactions and can be accumulated in the atmosphere [START_REF] Kawamura | Seasonal changes in the distribution of dicarboxylic acids in the urban atmosphere[END_REF]. The predominance of oxalic acid has been observed in the urban rain and snow samples and ice/snow samples from Greenland. However, the relative abundance of oxalic acid in the total diacids (av. 50%) in the remote marine rainwaters is much higher than those in urban rain (37%), snow/sleet (28%) samples (Semp6r6 and [START_REF] Setup&6 | Comparative distributions of dicarboxylic acids and related polar compounds in snow, rain and aerosols from urban atmosphere[END_REF] and Greenland ice/snow samples (28%) (Kawamura [START_REF] Kawamura | Organic acids and aldehydes in the ice s~unples from Site-J, Greenland[END_REF]. These results suggest that photochemical reactions to produce oxalic acid is more significant in the m~trine atmosphere than continental air. Interestingly, oxalic acid has been found in eastern Pacific Ocean wate:~s by the use of HPLC [START_REF] Steinberg | Oxalic acid, glyoxalic and pyruvic acids in eastern Pacific Ocean waters[END_REF]. Unfortunately, these authors did not collect surface waters but reported oxalic acid concentrations of c. 10#gE -1 at 75m depth. They considered that oxalic acid is a product and substrate of marine bacteria. However, concentrations of oxalic acid in the western Pacific rainwaters were found to be 2--40 times higher than those reported in seawater, suggesting that sea-to-air transport of oxalic acid is not an important process. The second most abundant species was either succinic (C4), malonic (C3) or phthalic acid (Cs) followed by glutaric (Cs), adipic (C6) and azelaic (C9) acids (Fig. 4). The C 4 diacid comprised 9-20% (av. 13%) whereas malonic acid comprised 4-19% (av. 12%) of the total diacids (Table 3). Shorter chain diacids (C2-C4) accounted for c. 80% of the total diacids and their relative abundances increase from the Northern to the Southern Hemisphere (Fig. 5). These results suggest that during long-range transport, photochemical oxidation of organic matter produced preferentially short chain diacids (C2-C4). Actually, in the marine atmosphere, volatile fatty acids with carbon numbers > C 4 as well as mid-chain 4-oxo ketocarboxylic acids which are both present in the marine atmosphere [START_REF] Kawamura | Identifications of aliphatic keto carboxylic acids in marine aerosols using capillary gas chromatography-mass spectrometry[END_REF][START_REF] Duce | The atmospheric input of trace species to the world ocean[END_REF] may serve as precursor compounds of succinic acid. Conversely, hydroxylation of succinic acid produces malic acid which is further decomposed to malonic acid [START_REF] Kawamura | Seasonal changes in the distribution of dicarboxylic acids in the urban atmosphere[END_REF]. Some of these species may further be oxidised to result in oxalic acid in the remote marine atmosphere. Phthalic (Ca), glutaric (Cs) and azelaic acids (C9) accounted for 1-21% (av. 7%), 2--4% (av. 3%) and 0.5-8% (av. 3%) of the total diacid, respectively. Interestingly, phthalic acid was the second most abundant in the R1 sample (21%) whereas it represents less than 10% in the other marine rains (Table 3; Fig. 4c). Ester forms of this compound are used as plasticisers. Phthalic acid has been reported in high concentrations in Los Angeles [START_REF] Kawamura | Capillary GC determination of short-chain dicarboxylic acids in rain, fog, and mist[END_REF][START_REF] Simoneit | Organic tracers in ambient aerosols and rains[END_REF] and Tokyo aerosol samples [START_REF] Kawamura | Seasonal changes in the distribution of dicarboxylic acids in the urban atmosphere[END_REF]Semprr~ and Kawamura, 1994) as well as in Tokyo precipitation samples (Semprr6 and [START_REF] Setup&6 | Comparative distributions of dicarboxylic acids and related polar compounds in snow, rain and aerosols from urban atmosphere[END_REF]. This aromatic acid is potentially derived by the atmospheric oxidation of polynuclear aromatic hydrocarbons such as naphthalene [START_REF] Kawamura | Seasonal changes in the distribution of dicarboxylic acids in the urban atmosphere[END_REF]. Our results suggest that an anthropogenic source is more significant in western North Pacific (R1) well known to receive dust particles from China and other Asian countries [START_REF] Duce | The atmospheric input of trace species to the world ocean[END_REF]. However, marine sources producing phthalic acid cannot be precluded because phthalic acid was abundantly detected in the remote marine rainwaters. The C 9 diacid has been considered as a unique photochemical oxidation product of biogenic unsaturated fatty acids which contain a double bond predominantly at C 9 position [START_REF] Kawamura | Organic compounds in the rainwater of Los Angeles[END_REF][START_REF] Yokouchi | Characterization ofqoolar organics in airborne particulate matter[END_REF][START_REF] Kawamura | Implications of co-oxocarboxylic acids in the remote marine atmosphere for photo-oxidation of unsaturated fatty acids[END_REF]. Relative abundance of azelaic acid in the total diacids ranged from c. 0.5% (Rll) to c. 8% (RI0). Interestingly, relative abundance of C 9 diacid showed a negative correlation with that of phthalic acid in the samples (R1-R7) collected in the Northern Hemisphere and equatorial Pacific (Fig. 4c). On the other hand, glutaric (Cs) and adipic (C6) acids have been reported as ozone oxidation products of cyclohexene (Grosjean et al., 1978;[START_REF] Hatakeyama | Ozone-cyclohexene reaction in air: quantitative analysis of particulate products and the reaction mechanisms[END_REF] 1985) and considered as a potential tracer of continental aerosol [START_REF] Kawamura | Distributions of low molecular weight dicarboxylic acids in the North Pacific aerosol samples[END_REF]. However, the C6 diacid comprised only 1% of the total diacid in the R1 sample, which was collected in the mid-latitude of western North Pacific (Fig. 1). The relative abundance of C 6 diacid rather showed a parallel distribution with that of C 9 diacid (Fig. 4b), suggesting that adipic acid may be of natural origin in the remote rainwater.

It is likely that the former considerations based on laboratory simulation [START_REF] Hatakeyama | Ozone-cyclohexene reaction in air: quantitative analysis of particulate products and the reaction mechanisms[END_REF] and urban aerosol studies [START_REF] Kawamura | Seasonal changes in the distribution of dicarboxylic acids in the urban atmosphere[END_REF] are not valid for wet precipitation in the remote marine atmosphere. Pyruvic or glyoxylic acid was the dominant ketoacid, the longer chain to-oxoacids being less abundant (Fig. 6). However, the chain length distributions of ~o-oxoacids seems to be consistent with those of ~, ~o-dicarboxylic acid. The parallel distributions suggest that these LMW ~o-oxoacids are one of the precursors of LMW ~, to-dicarboxylic acids. It is of interest to note that pyruvic acid (C3) is either the second or first dominant ketoacid species, being in good agreement with previous urban studies [START_REF] Kawamura | Seasonal changes in the distribution of dicarboxylic acids in the urban atmosphere[END_REF]Semp6r6 and Kawamura, 1994) suggesting a different source for pyruvic and co-oxoacids. Moreover, the lifetime of pyruvic acid is rather short (few hours) suggesting that the occurrence in rain samples of this species is mainly due to an in situ production rather than long-range transport. Interestingly, glyoxylic and pyruvic acids have been detected in eastern Pacific seawaters [START_REF] Steinberg | Oxalic acid, glyoxalic and pyruvic acids in eastern Pacific Ocean waters[END_REF]. The authors found pyruvic and glyoxylic acid concentrations at 75 m depth (no samples in the surface waters) to be 20 and 5 g g : -1 , respectively. These values are also in the same order of magnitude as those reported for marine rainwater samples (Table 2). These ketoacids are probably more abundant in the surface waters due to stronger biological activities [START_REF] Bada | Combined amino acids in Pacific Ocean waters[END_REF] and may in part contribute to the ketoacids in the marine atmosphere.

co-Oxononanoic acid (C9), a unique photooxidation product of biogenic unsaturated fatty acids whose double bond exists predominantly at the C 9 position [START_REF] Kawamura | Implications of co-oxocarboxylic acids in the remote marine atmosphere for photo-oxidation of unsaturated fatty acids[END_REF] was also detected in some rain samples as only minor species. A similar trend was also observed in the relative abundance of C 9 diacid (Fig. 4b). Interestingly, this compound was found to be more abundant in the remote aerosol samples collected over the ocean in the same area (Semp~r~ and Kawamura, in press). The difference in the molecular distribution of C 9 to-oxoacid between aerosol and rain may suggest that the ~o-oxoacid is further oxidised to corresponding diacid and related compounds in the upper levels of the troposphere and/or in the rain droplets.

Cis/trans configuration of unsaturated dicarboxylic acids in urban atmosphere

Two aliphatic unsaturated diacids were detected in the marine rain samples: maleic (cis configuration) and fumaric acid (trans configuration). Interestingly, the cis/trans ratio showed a diversity ranging from 0.5 to 3.8 (av. 1.3). The M/F ratio is probably controlled by the production of maleic acid from the photochemical oxidation of benzene [START_REF] Bandow | Ring-cleavage reactions of aromatic hydrocarbons studied by FT-IR spectroscopy. I. Photooxidation of toluene and benzene in the NOx-air system[END_REF] and the subsequent isomerisation to fumaric acid [START_REF] Kawamura | Seasonal changes in the distribution of dicarboxylic acids in the urban atmosphere[END_REF]. Alternatively, maleic acid may be produced from marine derived aromatics including phenolic materials, which have been reported to originate from macro algae and enrich in the microlayers of seawater [START_REF] Carlson | Surface microlayer phenolic enrichments indicate sea surface slicks[END_REF]. It is of interest to note that M / F ratios are lower than those (av. 5.8) from Tokyo rain samples (Semp6r6 and [START_REF] Setup&6 | Comparative distributions of dicarboxylic acids and related polar compounds in snow, rain and aerosols from urban atmosphere[END_REF]. It is likely that the maleic acid production is enhanced in the urban atmosphere, whereas in remote areas the cis-trans isomerisation may prevail in the control of maleic acid concentration.

CONCLUSIONS AND SUMMARY

Remote marine rainwater samples collected over the western North Pacific showed the presence of homologous series of dicarboxylic acids (C2-Clo) as well as ketoacids (C2-C9) and dicarbonyls (C2-C3). In all the rain samples, oxalic (C2) acid was found as the most abundant diacid species followed by malonic (C3) or succinic (C4) acid. Longer chain diacids are generally less abundant.

The concentrations of total diacids were found as high as 9 5 9 # g ~ -1. The concentration level (av. 237 # g f -1 ) was unexpectedly high compared to continental rainwater (e.g. 12-540#g~ -1 for Tokyo rains). High concentrations were interpreted by (1) long-range atmospheric transport of continental air mass containing diacids and related polar compounds, and (2) production of diacids in the marine atmosphere by photo-induced oxidation of > C 3 organic precursors of both continental and marine origin. Ketoacids such as glyoxylic (C2) and pyruvic (C3) acids are likely intermediates to result in oxalic acid. Photochemical production and subsequent accumulation were supported by the higher relative abundance of oxalic acid (av. 50%) in the remote marine rainwater than that of continental rain/snow (28-33%) and Greenland snow/ice (28%) samples.

The dicarboxylic acids were found as the important chemical species of rainwater D O C (av. 1.6 mgC #-1), accounting for up to 5% (av. 3%) of DOC. These values are c. 3 times higher than that of continental rainwaters. This study suggested that, in the remote marine atmosphere, organic compounds originated from either long-range transport of continental sources or sea-to-air emission of marine organic matter are subjected to photochemical oxidations to produce oxalic acid and other polar compounds.

  Fig. l. Cruise track of R/V. Hakuho Maru: KH-92 started 16 September 1992 at Tokyo, Japan, and ended 26 October 1992 at Cairns, Australia. The circles indicate the sampling area for rainwater collection during the cruise.

Fig. 3 .

 3 Fig. 3. Latitudinal distribution of the dicarboxylic acid (a), ketoacid (b) and dicarbonyl (c) concentrations in the western Pacific rainwater samples, September-October 1992.

Fig. 4 .

 4 Fig. 4. Relative abundance of individual dicarboxylic acids in the western Pacific rainwater samples, September-October 1992: (a) oxalic acid (C2), malonic (C3) and succinic acids (C4); (b) adipic (C6) and azelaic acids (C9); (c) phthalic (C8) and azelaic acids; (d) pimelic acid (C?), suberic (C8) and azelaic acids.

Fig. 5 .

 5 Fig.5. Latitudinal changes in the relative abundance (%) of cumulated C2--C4 dicarboxylic acids including oxalic, malonic, methylmalonic, oxomalonic, maleic and succinic acids in the total diacids (C2-Clo) in the western Pacific rainwater samples, September-October 1992.

Fig. 6 .

 6 Fig. 6. Relative abundance of individual (o-oxoacids and pyruvic acid in the western Pacific rainwater samples, September-October 1992: (a) glyoxylic (C2), 3-oxopropanoic, and 4-oxobutanoic acids; (b) 5-oxopentanoic, 6-oxohexanoic and 9-oxononanoic acids; (c) pyruvic acid (Ca).

but TOT I 488 c~i c•i c, = :8 ' I 688 Gly

				Ph
	~, l o :	-.,'-~
		, :	;	.	/	!	I
		888	I 1808	'		I :12.88	'	I 1488
		Scan Number
	Fig. 2. A reconstructed total ion chromatogram (RIC) of the derivatives of dicarboxylic acids, ketocar-
	boxylic acids and dicarbonyls isolated from the marine rain sample collected from the South Pacific (RI3),
	October 1992. For abbreviation see Table 2. C, means dicarboxylic acid with n carbon numbers, iC,
	indicates branched chain (iso) diacid. M and F are abbreviations of unsaturated diacids: maleic and fumaric
	acids, respectively. C.to indicates og-oxocarboxylic acid with n carbon numbers. Me-Gly, Pyr, Malic, Gly,
	Ph mean methylglyoxal, pyruvic, malic, glyoxylic and phthalic acids, respectively.

Table 2 .

 2 Concentrations of dicarboxylic acids and related polar compounds in the rainwater samples collected from western Pacific atmosphere in 1992

	U, 7~
		Av.		123	30.1	1.01	1.14	2.17	27.8	1.87	2.66	0.66	5.45	5.20	2.36	2.91	24.5	1.80	3.68	0.58	237	83.8	122		11.9	12.2	1.07	3.08	0.56	0.43	0.16	29.4	11.3	21.3		4.93	6.87	11.8	5.31	10.6
	R9 R10 Rll R12 R13 R14	Oct. 14 Oct. 15 Oct. 17 Oct. 17-18 Oct. 2(~21 Oct. 25		398 48.0 119 131 74.9 84.0	71.5 8.25 49.6 44.8 25.3 19.3	1.58 0.33 2.92 2.34 0.90 0.96	3.29 0.68 1.17 0.84 0.51 1.12	4.45 1.11 3.75 3.20 1.22 0.92	57.7 13.2 53.0 40.7 19.9 22.6	1.89 1.60 4.92 4.07 1.50 1.90	5.35 1.71 1.96 1.48 3.06 1.78	0.45 3.14 0.26 0.18 0.05 0.04	12.5 5.49 9.56 6.19 3.47 3.87	9.78 10.8 3.36 2.34 5.67 2.93	6.74 1.95 1.10 0.70 0.89 0.82	5.60 6.59 1.02 0.86 0.98 0.95	38.8 10.4 6.07 3.74 15.1 6.37	3.18 0.23 3.71 2.28 1.14 0.85	4.70 9.38 1.27 1.36 2.09 2.34	1.47 1.30 0.10 0.10 0.32 0.30	626 124 262 246 157 151	206 49.1 89.8 81.0 55.9 50.8	67.1 50.0 183 118 39.1 71.9		3.26 87.2 11.8 10.0 3.39 0.97	17.8 9.92 21.4 12.7 6.71 4.62	0.59 0.51 0.94 3.96 0.76 0.45	2.63 3.24 7.97 7.28 3.87 1.74	1.43 1.18 0.91 0.83 0.61 0.37	0.16 2.61 0.87 0.67 0.19 0.03	0.07 1.03 0.02 0.14 0.03 0.05	26.0 106 43.9 35.6 15.6 8.22	9.46 43.3 16.8 14.2 6.14 3.13	2.77 42.6 30.6 17.1 3.87 3.91		5.46 0.11 8.72 16.0 5.21 4.09	8.09 0.95 18.8 21.8 11.1 4.81	13.6 1.06 27.5 37.8 16.3 8.91	6.08 0.45 12.1 17.0 7.18 4.04	1.45 0.43 19.2 18.2 4.05 4.24
	Samples ID R1 R2 R3 R4 R5 R6 R7 R8	Date Sep.19 Sep. 21-22 Sep. 22 Sep. 22-23 Sep. 23 Sep. 23 Sep. 30-Oct.1 Oct. 6	Diacids (pg Y-1)	Oxalic, Cz 461 27.5 18.7 26.9 59.6 13 57.9 44.7	Malonic, C3 109 1.96 2.47 2.47 21.3 25.9 16.8 13.7	Methylmalonic, iC4 2.18 0.00 0.14 0.17 0.97 0.99 0.41 0.27	Oxomalonic, C3 5.32 0.35 0.00 0.00 0.59 0.96 0.29 0.32	Maleic, uC4 7.50 0.29 0.22 0.65 6.34 1.61 1.38 1.97	Succinic, C4 88.2 5.74 4.26 6.34 20.1 24.8 11.5 13.0	Methylsuccinic, iC5 5.72 0.15 0.24 0.33 0.82 0.99 0.46 0.49	Fumaric, uC4 13.5 0.62 0.38 0.60 1.68 2.85 0.57 0.74	Malic, hC4 1.09 0.23 0.35 0.00 0.57 1.91 0.51 0.32	Glutaric, C5 15.2 2.04 1.19 1.32 3.97 5.22 2.45 2.35	Adipic, C6 10.4 2.97 3.03 1.75 3.93 7.85 3.93 2.82	Pimelic, C7 11.9 1.04 0.65 0.56 1.78 2.43 1.21 0.74	Suberic, C8 10.8 1.42 1.19 0.94 2.08 3.75 2.23 1.52	Phthalic, C8 197 3.69 0.40 2.99 19.7 19.6 7.42 7.16	4-Oxopimelic, C7 8.18 0.47 0.21 0.30 0.77 1.87 0.57 0.39	Azelaic, C9 9.65 1.78 2.32 1.76 3.05 4.95 3.92 2.28	Sebacic, Clo 1.60 0.26 0.15 0.23 0.42 0.77 0.59 0.37	Subtotal 959 50.5 35.9 47.4 148 219 112 93.2	Total diacid-C (#gC~ -1) 359 18.2 12.9 16.7 55.5 77.9 39.5 33.2	Diacid flux (#gm-2h -1) NM 4.51 487 16.9 264 117 40.0 NM	Ketoacids (/~g E-1)	Pyruvic, C3 8.27 2.41 2.19 0.64 10.2 15.4 3.60 5.30	Glyoxylic, C2 49.9 2.15 1.91 1.13 11.6 14.9 8.47 7.50	3-Oxopropanoic, C3 2.51 0.44 0.60 1.16 0.97 0.89 0.55 0.54	4-Oxobutanoic, C4 5.25 1.29 0.94 0.47 2.68 3.61 1.07 0.63	5-Oxopentanoic, C5 0.21 0.28 0.19 0.09 0.04 0.77 0.28 0.21	6-Oxohexanoic, C6 0.00 0.09 0.14 0.02 0.22 0.68 0.04 0.07	9-Oxononanoic, C9 0.51 0.00 0.09 0.00 0.06 0.11 0.03 0.00	Subtotal 66.7 6.65 6.05 3.51 25.76 36.3 14.0 14.2	Total ketoacid-C (/~gC~-1) 23.5 2.66 2.43 1.38 9.77 14.0 5.13 5.26	Ketoacid flux (/~gm-2 h -1) NM 0.59 82.2 1.35 46.0 19.5 5.01 NM	Dicarbonyls ~g t -1)	Methylglyoxal, C3 8.95 1.26 1.98 0.48 3.77 6.98 1.62 3.21	Glyoxal, C2 7.94 0.97 1.13 0.21 11.5 7.82 2.16 3.67	Subtotal 16.9 2.24 3.11 0.69 15.3 14.8 3.78 6.88	Total dicarbonyl-C (/~gC E 1) 7.76 1.03 1.46 0.33 6.66 6.73 1.70 3.12	Dicarbonyl flux (/~gm-Zh -1) NM 0.20 42.2 0.25 27.3 7.93 1.35 NM

i: iso; u: unsaturated; h: hydroxy; NM: not measured.

Table 3 .

 3 Relative abundance (%) of dicarboxylic acids and related polar compounds in the rainwater samples(n = 14) collected from western Pacific atmosphere in 1992

	Classes of compounds	Range	Average
	Diacids (%)
	Oxalic, C2	39-64	50 _ 6
	Malonic, C3	3.9-19	12 _ 5
	Methylmalonic, iC4	0.0-1.1	0.5 -4-0.3
	Oxomalonic, C3	0.0--0.7	0.4 + 0.2
	Maleic, uC4	0.6-4.3	1.2 + 10
	Succinic, C4	9.2-20	13 ___ 3
	Methylsuccinic, iC5	0.3-1.9	0.8 + 0.5
	Fumaric, uC4	0.5-2.0	1.1 ___ 0.4
	Malic, hC4	0.0-2.5	0.5 + 0.6
	Glutaric, C5	1.6-4.0	2.8 _ 1
	Adipic, C6	1.0-8.7	3.6 +__ 2
	Pimelic, C7	0.3-2.0	1.1 + 1
	Suberic, C8	0.4-3.3	1.7 + 1
	Phthalic, Ca	1.1-21	7.4 ___ 5
	4-Oxopimelic, C7	0.2-1.4	0.7 _ 0.3
	Azelaic, C9	0.5-7.6	2.7 + 2
	Sebacic, Clo	0.1M-I.1	0.4 + 0.2
	Total	100
	Ketoacids (%)
	Pyruvic, C3	12-83	31 + 18
	Glyoxylic, C2	9.4-75	45 _ 16
	3-Oxopropanoic, C 3	0.5-33	6.7 _ 8
	4-Oxobutanoie, C4	3.1-25	13 + 7
	5-Oxopentanoic, C5	0.2-4.5	2.5 + 2
	6-Oxohexanoic, C6	0.0-2.5	1.2 + 1
	9-Oxononanoic, C9	0.0-1.5	0.4 _ 0.4
	Total	100
	Dicarbonyls (%)
	Methylglyoxal, C3	10-69	43 _ 15
	Glyoxal, C2	31-90	57 _ 15
	Total	100
	i: iso. u:unsaturated, h: hydroxy.

Acknowledgements--The authors are very grateful to K. Tanaka for the help of sample collection. We wish to acknowledge the Japan Society for the Promotion of Science (JSPS) for the post-doctoral fellowship to R. S as well as useful comments of referees. The authors appreciated the help of Dr France Van Wambeke for drawing Fig. 1. This study was in part supported by the Ministry of Education, Science and Culture through Grant-in-Aid No 06453009.