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Estimation of diffuse pollution loads of pesticides in tersakan sub-basin of Yeşilirmak river

Ayyıldız, Ceren
Tersakan Creek is one of the highly polluted tributaries of Yeşilırmak River because it receives pollution loads both from discharges of the industrial facilities and run-off water of the agricultural areas in the sub-basin. A monitoring program was implemented to determine the water quality status of the sub-basin in accordance with the EU Water Framework Directive (WFD). The results of the water sample analyses revealed that concentrations of 22 pesticides, out of the detected 57 pesticides, exceeded the pre-defined environmental quality standards (EQSs). Some of the pesticides are discharged by industries; however, mass balance calculations showed that their contribution to the pollution was relatively lower. This implied that main contribution to pesticide load to the Tersakan Creek was attributable to diffuse loads from agricultural lands. This study aimed to estimate the agricultural diffuse pollution loads for pesticides exceeding EQSs in the Tersakan Creek, which is simply calculated through multiplying the sediment yield (estimated by a GIS based model, Dynamic Erosion Model and Monitoring System developed by the General Directorate of Combating Desertification and Erosion) by pesticide soil concentration (estimated by a pesticide fate and transport model PESTRANS). Results from a drainage area of the Tersakan Creek showed that suggested and reported application rates of the pesticides such as Cypermethrin, Alpha-cypermetrhin and Dichlorvos contribute to diffuse pollution loads causing the exceedance of EQSs at the Tersakan Creek. Furthermore, additional calculations were also performed to estimate the required maximum pesticide application rate not to exceed EQSs.