Elfrida M Carstea

G Pavelescu

C Ioja

L Cristescu
email: cristescu@inoe.inoe.ro

Evaluation of the anthropogenic impact on surface water systems: case of Lower Arges Basin, Romania

Keywords: Sewage, pollution, developing countries, quality, treatment

Evaluation of the anthropogenic impact on surface water systems: case of Lower Arges Basin, Romania

INTRODUCTION

European Union countries must achieve good ecological status for all rivers until 2015. This goal is more problematic in developing countries where cities are rapidly growing and authorities have to deal with new wastewater management problems. One of the most polluted areas from Romania is the Arges Lower Basin due to the fact that it collects large quantities of untreated waste from Bucharest metropolitan area. This large city (2.5 million inhabitants) lacks a wastewater treatment plant and the municipal waste is directly discharged into the river.

During the last decades, fluorescence spectroscopy has been intensely used in water river quality studies [START_REF] Reynolds | Rapid and direct determination of wastewater BOD values using a fluorescence technique[END_REF][START_REF] Baker | Fluorescence properties of some farm wastes: Implications for water quality monitoring[END_REF][START_REF] Baker | Protein-like fluorescence intensity as a possible tool for determining river water quality[END_REF][START_REF] Hudson | Fluorescence analysis of dissolved organic matter in natural, waste and polluted waters-a review[END_REF]. It is a rapid and sensitive technique that requires only small quantities of sample, without any preparation. Depending on the setup parameters, a sample can be measured in approximately one minute offering the spectral fingerprint for any type of water body. Due to its effectiveness, many researchers suggest using fluorescence spectroscopy as a surrogate technique for conventional water quality parameters, such as biochemical oxygen demand [START_REF] Reynolds | Rapid and direct determination of wastewater BOD values using a fluorescence technique[END_REF][START_REF] Hudson | Can fluorescence spectrometry be used as a surrogate for the Biochemical Oxygen Demand (BOD) test in water quality assessment?[END_REF].

The water quality indicator detected with fluorescence spectroscopy is dissolved organic matter, which is the ubiquitous fraction in water systems. The characteristic and quantity of dissolved organic matter helped in numerous studies [START_REF] Baker | Fluorescence properties of some farm wastes: Implications for water quality monitoring[END_REF][START_REF] Baker | Protein-like fluorescence intensity as a possible tool for determining river water quality[END_REF][START_REF] Wu | Relationships between DOC concentration, molecular size and fluorescence properties of DOM in a stream[END_REF] to identify the contaminant and easily quantify the degree of pollution. Dissolved organic matter comprises two principal fluorescence components: the microbial derived component and the terrestrial derived one. Protein-like fraction, microbial derived, indicates the bacterial and algal activity, while the humic-like component shows the quantity of degraded plant material present in the river [START_REF] Mcknight | Spectrofluorimetric characterization of dissolved organic matter for indication of precursor organic material and aromaticity[END_REF][START_REF] Samios | Structural investigations of aquatic substances from different watershed[END_REF]. These components are brought into the river system through soil leaching, surface run-off and point source pollution [START_REF] Novotny | Water Quality: Diffuse Pollution and Watershed Management[END_REF][START_REF] Goel | Water Pollution -Causes, Effects & Control[END_REF].

The aim of this study was to evaluate the anthropogenic impact, mostly the urban influence, on the Arges Lower Basin. Therefore, the water quality analysis was performed using fluorescence spectroscopy and physical and chemical parameters (biochemical oxygen demand, pH, conductivity and turbidity) with standard procedures.

MATERIAL & METHODS

Four experimental campaigns had been performed in 2006 and 2007 collecting river samples from the Arges Lower Basin. In the lower basin, Arges River has two major tributaries: Sabar River with good ecological status and Dambovita River that crosses Bucharest and collects discharged municipal waste. In total, nine samples points had been established, as can be seen in figure 1. Six points were set on Arges Lower Basin: 1 -Sabar River, 2 -Colibasi on the Arges River before the confluence with Sabar, 3 -Hotarele after the confluence with Sabar, 4 -Budesti on Dambovita River before the confluence with Arges River, 5 -Soldanu on Arges after the confluence with Dambovita River and 6 -Clatesti before the Arges River flow into the Danube. Danube water was also sampled ( 7) in order to evaluate the quantity of contamination carried into the river. The last two sampling points (8 -named 1Dambov and 9 -named 2Dambov) were set on the Dambovita River while it crossed the Bucharest city. Laser induced fluorescence measurements were performed with a Shamrock Spectrograph and ICCD Andor to record the spectra and a YAG-Nd laser was used (266 nm) as excitation source with 10 Hz frequency and 3-6 ns pulse duration. The spectrofluorometer FLS920 Edinburgh Instruments was also used to record fluorescence spectra. The measuring parameters were: excitation wavelength 265 nm, emission wavelength range 285 -550 nm with steps of 1 nm,

Evaluation of the anthropogenic impact on surface water systems: case of Lower Arges Basin, Romania -Elfrida M. CARSTEA 3 / 6 integration time 0.2 s. The standard biological (biochemical oxygen demand) and physical (pH, turbidity, conductivity) parameters were measured using conventional techniques.

RESULTS AND DISCUSSION

The water sampled at the strategically set collection points clearly evidenced the human impact on the water quality. The highest values for conductivity and turbidity were registered at Budesti sample, on Dambovita River, and the lowest at samples collected from points located before the Dambovita and Arges River confluence. The pH values ranged from 7 to 8.2 and no correlation with the other physical parameters was observed.

All four campaigns presented high quantities of organic matter at Budesti sample. In figure 2, the fluorescence emission spectrum for Budesti is presented, with the protein-like and humic-like fluorescence centres. Due to the fact that the protein-like component indicates the microbial activity, this fluorophore was used to quantify the degree of contamination with sewage water. The maximum at 294 nm emission wavelength is the Raman peak, which represents the scattered light on water molecules, with a constant shift of 3290cm -1 from excitation wavelength. Therefore, this peak was taken as reference and all fluorescence values were normalized to the Raman value.

The fluorescence intensities of the protein-like fraction are presented in figure 3a for the samples collected along the Arges River flow and in figure 3b The two samples, named 1Dambov and 2Dambov (fig. 3b), collected from Dambovita River in Bucharest before sewage discharge, showed low protein-like fluorescence intensities. The significant increse of microbian pollution was detected in Budesti location, proving that the major source of pollution for Dambovita and Arges Rivers is the Bucharest municipal wastewater.

An hourly variation was observed in the organic matter fluorescence intensity depending on the quantity of sewage water released into the river. The variation can be seen in figure 4. The protein-like component measured at Budesti sample presented the highest values in the morning (7 AM) and in the afternoon (6 PM) and the lowest values before noon (11 AM). This trend was determined by the increase in human activity at 7 AM and 6 PM in the Bucharest metropolitan area. The humic-like component followed the same behaviour and this could probably be explained by the fact that the municipal waste, once released into the river, increased the debit carriyng along higher quantities of soil and degraded plant matter. Therefore, the quantity of humic substances, in this case, was proportional to the quantity of water discharged into the river. Evaluation of the anthropogenic impact on surface water systems: case of Lower Arges Basin, Romania -Elfrida M. CARSTEA

/ 6

The organic matter varied also at seasonal scale, with different responses for the protein-like and humic-like fractions, as can be seen in figure 5 for Budesti sample. The protein-like component presented the highest values in spring and the lowest in autumn. In winter and summer, approximately the same values were detected. However, more research is needed to establish if this is a general yearly trend and, if so, the cause of this trend has to be determined. A different behaviour was observed at the humic-like fluorescence; similar values were recorded in autumn and spring, higher than those registered in winter and summer. The increased precipitation quantities in spring and autumn probably generated higher quantities of humic substances. In order to obtain further water quality information biochemical oxygen demand was also measured. The results are presented in figure 6

CONCLUSIONS

Organic matter fluorescence intensity and biochemical oxygen demand were analysed in order to evidence the anthropogenic impact on the river water quality, specifically the Lower Arges Basin. The results revealed the significant contamination with wastewater discharged from Bucharest, especially at Budesti. After the Dambovita River confluence with Arges, the river started to be less contaminated due to the autopurification process. An hourly organic matter trend was detected due to the increased human activity in morning and afternoon hours. These results underline the need to develop wastewater treatment facilities at the discharge points.

Figure 1 :

 1 Figure 1: Sampling points on Arges River and tributaries.

Figure 2 :

 2 Figure 2: Fluorescence emission spectrum for Budesti sample. The protein-like and humic-like fluorescence centres are presented.

  for samples collected along Dambovita River. The samples collected at Colibasi, Sabar and Hotarele (Fig.3a) showed very low fluorescence intensities for the protein-like component, which represents a minor contribution from the nearby farms. Meanwhile, Budesti sample exhibited high fluorescence intensities for the protein-like fraction, due to the large input with sewage wastewater from Bucharest households into Dambovita River. The intensity of the protein-like fluorescence started to decrease at the next location, Soldanu, until Arges River flow into the Danube, showing the effects of the autopurification process (dilution).

8thFigure 3 :

 3 Figure 3: Fluorescence intensity maxima for the protein-like component measured at samples collected from Arges (a) and Dambovita (b) Rivers.

Figure 4 :

 4 Figure 4: Fluorescence intensity maxima for the protein-like component measured for Budesti sample at hourly frequency.

Figure 5 :

 5 Figure 5: Seasonal variation of the protein-like fluorescence for Budesti sample.

Figure 6 :

 6 Figure 6: Biochemical oxygen demand results in comparison with protein-like fluorescence intensity.