Health and ecological risks assessment of heavy metals and metalloids in surface sediments of Urmia Salt Lake, Northwest of Iran.

Urmia Lake, in the northwest of Iran, is the largest body of saline water in the Middle East, which has been desiccated in recent decades. To investigate the pollution status and ecological-health risks of heavy metals and metalloids in the surface sediments of this lake, 26 sediment samples were collected along the salt marshes of the lake and were analyzed for heavy metals and metalloid concentrations. The potential ecological risk assessment was carried out using enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF), and potential ecological risk (Eri) standard indices. The average concentrations (mg kg-1) of heavy metals and metalloids were as follows: Fe (11,714) > Sr (320.8) > Mn (274.3) > V (28.5) > Cu (24.7) > Zn (21.2) > As (17.3) > Ni (14.8) > Cr (12.6) > Pb (11) > Co (4.0) > U (1.7), Hg (0.6) > Mo (0.36). The concentrations of As, Hg, and Sr in lake sediments were higher than geochemical background values. The non-carcinogenic risks caused by heavy metals and metalloids were insignificant regarding health risks. Levels of carcinogenic risk for metal(loid)s were in the acceptable ranges (10-6-10-4). The ecological risk was low, except for As, Sr, and Hg which showed moderate to significant EF, Igeo, and CF values. Arsenic and Sr were enriched in the surface sediments in desiccated parts of the lake due to complete lake water evaporation. It seems that further drying of the lake increases the potential ecological risk of heavy metals and metalloids in the surface sediments of Urmia Lake.

Environmental impact assessment of salt harvesting from the salt lakes.

Urmia Saline Lake, USL which is registered as an international park by the United Nations, has suffered hypersalinity and serious dryness in recent years. Increasing the dryness trend has been led to a great tendency, especially by private sectors to harvest salt from different parts of the bed sediments. During this study the four- step process was used for environmental impact assessment of such a large scale salt harvesting activities with specialized Folchi matrix and enriched by data on heavy metal concentrations in the limited number of sediment samples. Impact analysis using matrix showed that the most significant impacts were on environmental components, namely "land use", "gradient and topography of the lake bed" and "hydrology and lake water quality" with score values of 73.22, 73.21 and 72.45, respectively. The mean concentrations of As, Cd, Cr, Hg, Pb, Ni and Zn in salt and sediment samples were 15.2±8.8, 0.05±0.047, 15±8.2, 0.54±0.3, 11.9±6.28, 15.4±9.56 and 22.3±13.66 mg/kg, respectively. The higher concentration of arsenic and lead in comparison with earth crust averages, warns that dispersion of salt particles from storage piles may affect local people's health. This study provides readers and authorities with environmental impacts of salt harvesting from unique saline Lake of Iran, presents effective management options such as stopping any unlicensed and unrestrained salt harvesting activities on the USL bed, avoiding deep excavations, minimizing accumulation of piles to prevent the diffusion of salt particles etc. and also specialized the Folchi matrix for application in similar projects.