Concentration of Total and Organic Mercury and Antagonistic Relationship Between Selenium and Organic Mercury in the Sediments of the International Anzali Wetland

Mercury (Hg) is considered as a global pollutant that is widely dispersed in the environment. Monitoring of total mercury (THg) concentration in the sediments without determination of organic mercury (OHg) and selenium (Se) is an unreliable approach to evaluate the precise toxicological effects of Hg. In the present study, concentrations of THg, OHg and Se in the surface sediments of the eastern and western parts of Anzali wetland were investigated. In addition, the correlation of THg and OHg with Se and total organic carbon were analyzed.
Forty surface sediment samples were collected from the eastern and western parts of the wetland. Analysis of total and organic mercury in the sediment samples were done with Advanced Mercury Analyzer and the concentration of selenium was measured using inductively coupled plasma atomic emission spectroscopy (ICP-OES).
The average concentrations of THg in the East and West wetlands were 109.53 and 68.39 ng/g dw, respectively. The average concentration of THg in the sediments of the eastern part of Anzali Wetland was significantly higher than that of the western part (P The THg concentration in the sediments of Anzali wetland was lower in comparison to other studied regions of the world. However, the percentage of OHg in the Eastern and Western part of wetland was high. Therefore, bioavailability and toxicity of Hg would be high in the sediments and aquatic environment. In this study, in spite of high molar ratio of Se to THg, there was relatively high content of OHg. We recommend to measure the various Se-species that are effectively bound to inorganic Hg and to determine the amount of Se and Hg in aquatic organisms.