The Rate of Changes in Agricultural Pesticides and TPHs in a Sediment Core from the Eastern Part of Anzali International Wetland, Iran

Abstract:

Organic pollution in aquatic ecosystems is one of the fundamental environmental problems that have human and biological origins. Furthermore, the increasing use of pesticides and herbicides, threats these ecosystems. In this study, we measured vertical distribution of agricultural pesticides (Diazinon, Butachlor, and Chlorpyrifos) and Total Petroleum Hydrocarbons (TPHs) in one core sediment sample from the eastern part of Anzali wetland, one of the most important international wetlands located in Iran. We also measured sedimentation rates using the dating method of ²¹⁰Pb. We found Chlorpyrifos, Diazinon, and Butachlor had the maximum levels of 72.0 ng g^-1, 25.0 ng g^-1, and 18.0 ng g^-1, respectively, during the years between 1988 and 2016. In general, the pesticide concentrations have significantly increased from 1904 to the present, due to excessive use in rice farms in the eastern part of the wetland. We also found the average concentration of TPH in the core sample was 52.75 mg kg^-1. The Carbon Preference Index (CPI) of 5.93 and Natural N-alkane Ratio (NAR) of -1.03 indicate biological contamination sources in the region. The results showed the overall sedimentation rate of 0.9 cm yr^-1, while the observed changes in depth of wetland and land use suggest higher rates during recent years. These results show more strict policies should be considered in ecological management strategies.