Heavy metals are essentially for hydrobionts, while at high concentrations being toxic. According to EU Directive (2006/11EC), due to their toxicity and bioacumulation, metals and their compounds are introduced in the list of hazardous substances to the aquatic body [1]. Metals in natural waters are presented both in dissolved and suspended forms. The proportion of these forms is varied for different metals and different water bodies. The toxicity and sedimentary potential of heavy metals are changed depending on their forms [2]. The metals are presented in different phases of the water system, including abiotic and biotic phases. As abiotic phases can be distinguished bottom sediments, their interstitial water, particulate materials and water [3]. Of the three phases (water, particulate materials and sediments), about 99% of the total content of metals is presented in sediments [4]. In order to identify the variation of heavy metals content, along the Prut River, the samples were collected seasonally. For determination of the heavy metals content in the sediments (freshly sampled), the extraction procedure recommended by the American Geological Agency was used [5]. The content of heavy metals was determined by the flame atomic absorption spectrometry. During of 2009-2010 years, the increasing trend of Cu content in the water layer along the Prut River has been established, while a higher content of Zn was identified in the middle sector. In the most samples the content of heavy metals in interstitial water is exceeding their concentrations in the water horizon. This demonstrates that the sediments can become a potential source of the metals mobilization in water layer. The content of heavy metals in the water layer did not exceed the allowable maximums set by the EU [6], Romania [7], USA [8] and Canada [9]. The content of heavy metals in the sediments, generally, did not exceed the quality requirements adopted in Romania [7]. However, the content of Ni exceeded the threshold effect level for bottom sediments, according to the USA [8] and Canada criteria [9]. References: [1] Directive 2006/11/EC of the European Parliament and the Council of the 15th of February, 2006 on pollution caused by certain dangerous substances discharged into the aquatic environment of the Community. [2] Chapman, D.; Kimstach, V. Selection of water quality variables In: Water Quality Assessments - A Guide to Use of Biota, Sediments and Water in Environmental Monitoring, 2nd Edition, Chapman D. (ed) ©UNESCO/WHO/UNEP, 1996. [3] Salomons, W. Sediment pollution in the EEC © ECSC-EEC-EAEC, Brussels, 1993, 136p. [4] Lee, S.; Moon, J.; Moon, H. In: Environmental Geochemistry and Health 2003, 25, p. 433–452. [5] Techniques of water-resources investigations of the United States Geological Survey, Fishman M., Friedman L. (Eds) Book 5, 3d edition, Washington, 1989, 545 p. [6] Directive 2008/105/EC of the European parliament and of the Council of 16 December 2008 on environmental quality standards in the field of water policy. [7] Order 161/2006 of 16 February 2006 concerning the classification of surface water to determine the ecological status of water bodies. [8]. Öztürk, M. et. al. In: Iran. J. Environ. Health Sci. Eng. 2009, 6(2), p. 73–80. [9] Osman, A.; Kloas, W. In: Journal of Environmental Protection. 2010, 1, p. 389–400.
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