evaluation of mercury accumulation in sediments and benthic invertebrate masses from sanandaj gheshlagh reservoir

previous studies showed that the level of total mercury (thg) in sanandaj gheshlagh reservoir (sgr) water is higher than those limits established by who (i.e., 1 µg/l). therefore a research project to evaluate the level of total mercury in sgr sediments and benthos masses during july to december 2009 from three different sites with different depths (2 to 30 meters) was carried out. samples were obtained using ekman grab. to prevent methyl mercury volatilization, samples were dried out using freeze drier and the level of the total mercury in sediments and benthic samples was measured by advanced mercury analyzer on the dry weight basis. szefer et al., 1999 method was used to calculate biota–sediment accumulation factor (bsaf). mean total mercury (± s.e.) concentration in benthos masses and sediments were 94.3 ± 5.02 and 117.66 ± 9.72 ng g-1 respectively. mean total mercury were not significantly differed in benthos masses during sampling efforts (f5, 10 = 2.16, p = 0.14), whereas the levels of total mercury in sediments were significantly different (f5, 10 = 4.88, p = 0.02). all calculated bsaf were lower than one which means the capacity of sgr benthos are not an important fact with respect to their level of thg. but due to the mercury methylation by benthos and its biomagnifications capability, strong considerations have to be taken into the account in respect to consumption of sgr benthivorous fish.