Occurrence of atmospheric current-use and historic-use pesticides at a CAWNET background site in central China

Abstract

China as an agricultural country has a considerable amount of pesticide usage. However, studies of current-use pesticides (CUPs) in the background air are very limited. Meanwhile, though historic-use pesticides (HUPs) have been banned globally, the abundance of HUPs in the background areas require urgent attention. In this study, air samples were collected using an active air sampler from January 2018 to January 2019 every six days at a background site (Jinsha, JSH) in central China to investigate the concentrations, seasonal variations and sources of CUPs and HUPs. The total volume for each sampling was 430 m3. Finally, a total of 54 sets of samples was collected. The annual median concentrations (gas plus particle) were 1053 (140–6409) pg m−3 for CUPs and 33.2 (2.12–158) pg m−3 for HUPs, respectively. Pyrethroids were the most abundant class of CUPs, accounting for 97.8% of the total CUPs. Most CUPs exhibited high levels in spring (chlorothalonil and trifluralin) and summer (pyrethroids, chlorpyrifos and dicofol), while no obvious seasonal pattern was observed for HUPs. The results of Clausius-Clapeyron equation and back trajectories suggested that most CUPs (excluding chlorpyrifos) and HUPs (HCHs, chlordane and α-endosulfan) were affected by long-range atmospheric transport, chlorpyrifos and β-endosulfan were influenced by short-range atmospheric transport or re-volatilization, and HCB was affected by regional combustion processes. Moreover, data of HUPs in 2012/2013 from previous studies was used for comparison. From 2012/2013 to 2018/2019, atmospheric concentrations of HCB, chlordane, α-HCH and γ-HCH declined by about 94%, 74%, 85% and 73%, respectively, indicating the effective emission controls of these compounds in China. However, the concentration of α-endosulfan increased by 51%, hinting at the fresh input transported from Anhui, Guangdong and Jiangxi provinces. Therefore, special attention and follow-up control measures should be taken for endosulfan in China.