Spatial and temporal distribution of pesticides and PCBs in the atmosphere using XAD-resin based passive samplers: A case study in the Quequén Grande River watershed, Argentina

Özet

XAD-resin based passive air samplers were deployed at 10 sites in the Quequén Grande River watershed inArgentina during three periods to evaluate the spatial and temporal variations of pesticides and PCBs in theatmosphere. Endosulfan and chlorpyrifos were the most prevalent pesticide because of their continued usage inArgentina, while DDTs, HCHs, chlordanes, dieldrin and heptachlors registered lower levels, reflecting their usein the past. Atmospheric endosulfan levels were 1–2 orders of magnitude higher during the application period(application: 800–12,000 pg/m3, pre- and post-application: < 2–350 pg/m3), suggesting that its use in the areacontinued even after a ban came into effect. The remaining organochlorine pesticides also reached higherconcentrations during this period, which is more likely attributable to temperature controlled air-surface exchangethan current applications. The highest concentrations of chlorpyrifos were recorded during the applicationperiod, in particular at agricultural sites, where its use is wide-spread on soybean fields. The fungicidechlorothalonil was found predominantly at urban sites and in proximity to Quequén harbor, suggesting that itsuse might be domestic and as a biocide in antifouling paints. A different temporal pattern was observed for theherbicide trifluralin, suggesting its use in the early stages of the wheat-growing season during winter. Limitedspatial variations in PCBs levels indicate a diffuse contamination source in the study area, while their relativelyhigh correlation with temperature suggests re-volatilization from local sources. Relative enrichment of lighterPCBs congeners could be attributed to re-evaporation from secondary sources as well as atmospheric transportfrom urban sites.