Assessment of Heavy Metals Content in Water and Sediments from the Lower Danube River Using EcoIndex

Transcription

1 Assessment of Heavy Metals Content in Water and Sediments from the Lower Danube River Using EcoIndex VIOLETA MONICA RADU 1 *, ALEXANDRU ANTON IVANOV 1, GYORGY DEAK 1, ELENA DIACU 2 1 National Institute for Research & Development in Environmental Protection, 294 Spl. Independentei, , Bucharest, Romania 2 Politehnica University of Bucharest, Faculty of Applied Chemistry and Materials Science, 1-7 Polizu Str., , Bucharest, Romania EcoIndex allow an integrated assessment of chemical pressures on ecosystems, observing spatial and temporal evolution of these pressures and the correlation of biotic and abiotic factors. This study aims to present an integrated assessment of the metals (Cd, Cr, Cu, Pb, Zn, Ni) content in Lower Danube River water and sediment, using EcoIndex for water (EIA) and EcoIndex for sediments (EIS). Water and sediment were sampled monthly, from 10 locations on the Calarasi-Braila section (km 375-km 175), for a period of four months (May August 2013). In the monitored areas, works took place for the improvement of navigation conditions. The overall assessment of water and sediment quality was achieved. The monitoring locations that require a more detailed assessment were highlighted for quantifying a potential accidental pollution. Keywords: EcoIndex, Heavy Metals, Danube River Water is the most important, limited, and vulnerable natural resource [1]. Worldwide the pollution has become one of the most important environmental problems [2]. With the development of human society, the environment is under increasing pressure, pollution becoming a global factor affecting all media of life: air, water and soil [3]. Surface waters are affected by pollution from industry, agriculture, transport, household activities, and tourism [4, 5]. Water quality monitoring is one of the most important priority in environmental policy [5-7], and this cannot be achieved without an integrated assessment of the water and sediment factors quality in the ecosystem [1]. Quality assessment for the aquatic ecosystem can be a complex process that requires several parameters that can have different pressures on overall water quality [1]. Currently, water quality assessment also focuses on heavy metals [8], because they are non-degradable, toxic, and persistent [9]. Anthropogenic activities and rocks disintegration are considered major sources for the accumulation of heavy metals in water resources [10-12]. Because of their toxic effects even in low concentrations, heavy metals are harmful for the biotic components of the ecosystem [13]. After reaching the aquatic environment, heavy metals accumulate in suspended matter and sediment becoming sources of long term pollution [14, 15] affecting aquatic life and ultimately human health [8, 9]. The best way to protect the environment is to prevent pollution [15, 16], which is easier than remediation. The remediation can be extremely expensive, complicated, with associated risks and unwanted side effects. This study presents an integrated assessment of chemical pressures on ecosystems based on the EcoIndex for water (EIA) and sediment (EIS), highlighting the spatial evolution of these pressures and linking the abiotic and biotic factors, in order to quantify a potential accidental pollution. Experimental part Study area With a relatively large share in Romanian water resources, the Danube is the second largest river in Europe [17], entering the country with a high load of pollutants which increases in transit until it flows into the Black Sea. Some pollutants exceed the permissible limits [18]. The monitoring sites are located in areas depicted in figure 1, where hydro-technical works are implemented in order to fulfill the Danube Commission s recommendations to maintain minimum depths during dry seasons for normal navigation. The hydro-technical works include activities such as dredging, embankments and sills that may have a potential impact on water quality and biodiversity [19, 20]. Samples The water and sediment samples were collected in polyethylene containers according to current standards [21-23]. Prior to sampling, the polyethylene containers were washed, treated with dilute hydrochloric acid and finally rinsed with deionized water. For each established sampling point, water samples were collected at three depths (0.5, 1.5 and 3 m) from left bank (LB), right bank (RB) and river center (C) and sediment samples were collected at 0.5 m from left bank (LB) and right bank (RB). In the laboratory, homogenized and unfiltered water subsamples were acidified with concentrated nitric acid to 0.5 % (v/v) and left for 48 hours at room temperature before determining the total metals content [24-26]. The sediment samples were dried, milled and granulometrically fractionated. Subsamples from the fraction with particle sizes under 63 µm were digested with aqua regia for the determination of metals content [27]. The concentration of heavy metals from water and sediment samples were determined with flame and graphite furnace atomic absorption methods using a Thermo M5 spectrometer. * radumonica33@yahoo.com REV.CHIM.(Bucharest) 67 No

2 Fig. 1. Monitoring areas [20] Reagents and quality assurance The reagents (Merck) used throughout the analyses were of analytical purity. The solutions were prepared with ultrapure water obtained through a Micropure Ultrapure water system (TKA, Germany). The determinations were carried out according to current standards [21-27]. The analytical quality assurance was monitored with certified reference materials and duplicate samples. Results and discussions The EcoIndex EIA and EIS values are obtained by correlating the monitored chemical indicators values to a natural reference background or baseline for a suitable water body (for a similar ecosystem unaffected by human activities). Such correlations can be obtained directly by dividing the monitored chemical indicator value to the reference and, if necessary, taking into account some corrective measures for general hydrographic conditions (for example the flow rate in the sampling period or the turbidity of the analyzed samples). The reference values for the EcoIndex can be obtained from historical data relevant to the water body or from national and international benchmarks values such as EPA (US Environmental Protection Agency) Freshwater Sediment or Freshwater Screening Benchmarks [28]. This study used as reference values the first class limits for water and the quality standards for sediment introduced by the Annex of the Romanian Ministerial Order no.161 from 2006 [29]. Usually, an EcoIndex value below 1 shows the absence of any chemical pressures to the environment from the evaluated chemical indicator. If the EcoIndex has a value between 1 and 3, some minor anthropic pressures are accounted for, but the environment suffers only minor damage, being able to adapt itself to the pressure. For EcoIndex values between 3 and 6, the chemical pressures affect the environment and, depending on the species which populate the water body, various degrees of effects are to be expected. Due to the difficulty in obtaining specific reference values for the evaluated water body and the different limnological conditions, these values should be carefully evaluated against the specific water body characteristics by field specialists. At values beyond 6, a greater environmental impact occurs, the water body requiring additional analysis, evaluation and even remediation. These numerical intervals are empirical in origin and are also used in more complex algorithms leading to various environmental indices [30-34]. In some individual cases further investigation are required to distinguish between anthropogenic pollution and higher natural levels. Riverbed geology, hydrological conditions, meteorological or other natural phenomena in the evaluated ecosystem can cause higher natural levels of mineral constituents. The integrated assessment based on EcoIndex values must take into account the relevant hydro-morphological parameters for the evaluated ecosystem, such as flow rate, water speed and water level. These parameters are useful in the spatio-temporal evaluation of EcoIndex values from different locations and different sampling dates. Elevated hydrological parameters (flow rate, water level and speed) lead to an increase in the amount of particulate matter in water and to changes in the sediment composition, through dislocation of sediments and erosion phenomena. Also, the presence of particulate matter leads to an increased total concentration of metals in the water, depending on the metals contained by the respective solid matter. Figure 2 shows the EIA and EIS cadmium levels calculated for each monitored location. EIA cadmium for the L1-L7 locations is mostly similar between river banks and center. For the L8-L10 locations, EIA cadmium is Fig. 2. EcoIndex cadmium levels in the REV.CHIM.(Bucharest) 67 No

3 Fig. 3. EcoIndex chromium levels in the Fig. 4. EcoIndex copper levels in the Fig. 5. EcoIndex lead levels in the slightly elevated for right and left banks, probably due to a higher solids content caused by shore erosion phenomena. Overall, the EIA cadmium falls below 0.15 suggesting the absence of respective chemical pressure to the environment. EIS cadmium shows differences between river banks and locations, caused by the high heterogeneity of the sediment types along the sampling points. Overall, the EIS cadmium falls below 1 suggesting the absence of respective chemical pressure to the environment. Figure 3 shows the EIA and EIS chromium levels calculated for each monitored location. EIA chromium is mostly similar between locations for the river center. The variations between river banks and locations are mostly due to combinations of shore erosion phenomena with different shore geochemical makeup. Overall, the EIA chromium falls below 0.05 suggesting the absence of respective chemical pressure to the environment. EIS chromium is similar between river banks and locations, probably due to the high mobility of its ionic species. Overall, the EIS chromium falls below 0.5 suggesting the absence of respective chemical pressure to the environment. Figure 4 shows the EIA and EIS copper levels calculated for each monitored location. EIA copper is mostly similar between river banks and locations. Overall, the EIA copper falls below 0.3 suggesting the absence of respective chemical pressure to the environment. EIS copper shows differences between river banks and locations, caused by the high heterogeneity of the sediment types along the sampling points. Overall, the EIS copper falls below 1.5 suggesting the presence of slight chemical pressures to the environment. Historically, the Danube sediments in the monitored area are characterized by slightly elevated levels of copper and nickel. These higher levels are either caused by the conjunction between decades of industrial pollution combined with a high degree of retention at sediment level or by uptake and transport from the hydrographic catchment areas where the geochemical content of these metals is higher. Most probably, the elevated levels are caused by a combination of these two phenomena. Either way, considering the long time that the riverbed ecosystem was exposed to these slightly elevated levels of copper and nickel, we can assume that the benthic biota is already adapted to these circumstances and the chemical pressures are chronic rather than acute. Figure 5 shows the EIA and EIS lead levels calculated for each monitored location. EIA lead is mostly similar between the river banks and locations. The slightly elevated levels fort the right bank in L8-L10 locations are mostly due to combinations of shore erosion phenomena with different shore geochemical makeup. Overall, the EIA lead falls below 0.4 suggesting the absence of respective chemical pressure to the environment. EIS lead shows differences between river banks and locations, caused by the high heterogeneity of the sediment types along the sampling points. Overall, the EIS lead falls below 0.4 suggesting the absence of respective chemical pressure to the environment. Figure 6 shows the EIA and EIS zinc levels calculated for each monitored location. EIA zinc is mostly similar between the river banks and locations. The slightly elevated levels for the right bank in L8-L10 locations are mostly due to combinations of shore erosion phenomena with different REV.CHIM.(Bucharest) 67 No

4 Fig. 6. EcoIndex zinc levels in the Fig. 7. EcoIndex nickel levels in the monitored locations (a water, Fig. 8. The Danube flow rate in the monitored locations shore geochemical makeup. Overall, the EIA zinc falls below 0.15 suggesting the absence of respective chemical pressure to the environment. EIS zinc shows differences between river banks and locations, caused by the high heterogeneity of the sediment types along the sampling points. Overall, the EIS zinc falls below 1 suggesting the absence of respective chemical pressure to the environment. Figure 7 shows the EIA and EIS nickel levels calculated for each monitored location. EIA nickel is mostly similar between locations for the river center. The variations between river banks and locations are mostly due to combinations of shore erosion phenomena with different shore geochemical makeup. Overall, the EIA nickel falls below 0.3 suggesting the absence of respective chemical pressure to the environment. EIS nickel shows differences between river banks and locations, caused by the high heterogeneity of the sediment types along the sampling points. Overall, the EIS nickel falls below 1.5 suggesting the presence of slight chemical pressures to the environment. Considering the historical levels for nickel and copper, we can assume that the benthic biota is already adapted to these circumstances and the chemical pressures are chronic rather than acute. As seen from figure 8, the Danube flow rate for the monitored locations varies from approximately 6000m 3 /s Fig. 9. The Danube water speed in the sampling points Fig. 10. The Danube level at the monitored locations on the main branches (L1 and L10) and m 3 /s on the medium sized branches (L2-L5 and L7-L9) to under 250 m 3 /s for L6. Figure 9 shows the water speed for the sampling points and Fig. 10 shows the Danube level in the monitored locations. The water speed is different between river banks and center, promoting different erosion rates for the respective locations. The water level from L1-L7 is aproximately m and for L8-L10 is aproximately 4 m (the distance between L1-L7 and L8-L10 is about 200 km). From integrated analysis of the environmental factors in conjunction with the hydrological conditions it can be observed that the overall situation of the monitoring period is characterized by the absence of additional environmental pressures. Conclusions The water EcoIndex (EIA) and sediment (EIS) EcoIndex allow integrated assessment of chemical pressures on ecosystems, highlight the spatial and temporal evolution of these pressures and links the abiotic and biotic factors. EIA and EIS provide an easily interpretable overview of the numerous chemical parameters of water and sediment quality. The EcoIndex approach is easy to use, the accuracy of the evaluation depending mainly on the reference values suitability REV.CHIM.(Bucharest) 67 No

5 The presented study was able to offer an overview of the Lower Danube ecosystem quality. This showed that the evaluated ecosystem is not affected by strong anthropogenic pressures from the monitored quality indicators in the monitored period. The presence of slightly higher level for some quality parameters such as copper and nickel content in sediments is historical and likely caused by a combination of natural phenomena and anthropogenic sources. In the monitored timeframe, EIA and EIS did not indicate a behavior that can be associated with local accidental pollutions. Acknowledgements: The authors are grateful to the general management and colleagues from INCDPM for their valuable assistance and suggestions in the development of EcoIndex. References 1. OLUBUKOLA ADEOGUN, A., European Journal of Scientific Research, 74, no. 2, 2012, p MOHAMMAD SALAH, E.A., TURKI, A.M., AL-OTHMAN, E.M., Journal of Environmental Protection, 3, 2012, p NOORI R. ET AL., Environmental Modeling & Assessment, 17, 2012, p. 411, DOI /s ISTVÁNOVICS, V., HONTI, M., Hydrobiologia, 686, 2012, p JENA, V. K., DIXIT, S., TIWARI, V., DUBEY, P., SINGH, R., GUPTA, S., DHUNDHEL, R.S., DAVIC, N., MATIC, N., RADOVIC, D., International Journal of Water Research, 1, no. 2, 2013, p BOYACIOGLU, H., Water SA, 32, no. 3, 2006, p SINGOVSZKA, E., BALINTOVA, M., Chemical Engineering Transactions, 26, 2012, p MAHAR, M.T., KHUHAWAR, M.Y., JAHANGIR, T.M., BALOCH, M.A., Journal of Environmental Science and Engineering, 2, 2013, p JUMBE, A.S., NANDINI, N., American Journal of Environmental Sciences, 5, no. 6, 2009, p AHMET, D., FEVZI, Y., TUNA, A.L., NEDIM, O., Chemosphere, 63, 2006, p CHANPIWAT, P., STHIANNOPKAO, S., KIM, K.W., Microchemical Journal, 95, 2010, p MUHAMMAD, S., SHAH, M.T., KHAN, S., Food Chemical Toxicology, 48, 2010, p IONESCU, P., RADU, V.-M., DEAK, Gy., DIACU, E., REV. CHIM. (Bucharest), 65, no. 9, 2014, p KUMARASAMY, P., JAMES, R.A., DAHMS, H.-U., BYEON, C.-W., RAMESH, R., Environ Earth Sci., 2013, DOI /s MAJOLAGBE, A.O., YUSUF, K.A., DURU, A.E., European Scientific Journal, 3, 2013, p ETIM, E.U., ADIE, G.U., Research Journal of Environmental and Earth Sciences, 4, no. 12, 2012, p TAKIC, L.M. ET AL., Advanced technologies, 1, 2012, p RADU, V.-M., DIACU E., VARDUCA A., REV. CHIM. (Bucharest), 64, no. 3, 2013, p MORIKI, A., SAVVIDIS, Y., KOMBIADOU, K., DIMITRIADIS, X., HATZINIKOLAOU, A., HOULLI, F., J. of Environmental Protection and Ecology, 14, 2013, p RADU, V.-M., IONESCU P., DEÁK Gy., IVANOV A.A., DIACU E., Journal of Environmental Protection and Ecology, 15, no. 2, 2014, p *** ISO /1998: Sampling Part 6: Guidance on sampling of water from rivers and streams. 22. *** ISO /2001: Sampling Part 12: Guidance on sampling of bottom sediments. 23. *** EN ISO /2004: Water quality. Sampling. Part 3: Guidance on the preservation and handling of water samples. 24.*** ISO 8288/2001: Water quality. Determination of cobalt, nickel, copper, zinc, cadmium and lead. Flame atomic absorption spectrometric methods. 25. *** EN 1233/2003: Water quality Determination of chromium Atomic absorption Spectrometric methods. 26.*** EN ISO 15586/2004: Water quality. Determination of trace elements using atomic absorption spectrometry with graphite furnace. 27.*** ISO 11047/1999: Soil quality Determination of cadmium, chromium, cobalt, copper, lead, manganese, nickel and zinc in aqua regia extracts of soil Flame and electrothermal atomic absorption spectrometric methods. 28.*** Information on 29.*** Ministerial Order No. 161 of 16 February 2006 approving the Norms on surface water quality classification to determine the ecological status of water bodies. 30. QINGJIE, G., JUN, D., YUNCHUAN, X., QINGFEI, W., LIQIANG, Y., Journal of China University of Geosciences, 19, no. 3, 2008, p LUO, W., LU, Y., WANG, T., HU, W., JIAO, W., NAILE, J.E., SEONG KHIM, J., GIESY, J.P., AMBIO, 39, 2010, p SESHAN, B.R.R., NATESAN, U., DEEPTHI, K., Int. J. Environ. Sci. Tech., 7, no. 2, 2010, p WU, Y., XU Y., ZHANG J., HU S., Trans. Nonferrous Met. Soc. China, 20, 2010, p ABDEL-LATIF, N.M., SALEH, I.A., Journal of American Science, 8, no. 6, 2012, p. 379 Manuscript received: REV.CHIM.(Bucharest) 67 No