Spatial variations of linear and cyclic volatile methyl siloxanes in a riverbasin and their air-water exchange

Özet

Linear and cyclic volatile methylsiloxanes (VMS) are Si and O containing organic compounds that are increas-ingly subject to scientific studies in recent years. They are used as solvents and coating materials in personal careproducts, cleaning materials and industrial applications. In this study, it was aimed to investigate the spatialvariations of VMS levels in river water and ambient air in Kucuk Menderes Basin and their air-water exchangepatterns. Grab river water samples and passive ambient air samples collected from 10 sites throughout KucukMenderes Basin located in Izmir region in Turkey, and they were analyzed for VMS. The concentrations ofΣVMSin river water and ambient air ranged from 48.4 to 148 ng L−1and from 41.7 to 433 ng m−3, respectively.Among the VMS compounds, the predominant compounds were found to be D5 and D3 in ambient air and riverwater, respectively. In general, concentrations of all VMS congeners increased towards downstream of the riverfor both water and ambient air samples and there were substantial fluctuations between the sampling points.These fluctuations may be due to wastewater discharges at some sites (increase), followed by loss by volatili-zation along the river (decrease). VMS concentrations measured in air and river water samples were used toestimate the net air-water exchange fluxes. In all cases, fluxes were negative, ranging between −159 (L4) and−11100 (D3) ng m−2day, indicating volatilization from water is a source for atmospheric VMS.