Gas-particle partitioning of pesticides in the atmosphere of the North China Plain

Abstract. Pesticide residues are ubiquitous in the atmosphere in the North China Plain (NCP), with concentrations largely determined by application patterns and physicochemical parameters such as persistence and volatility. However, knowledge of gas-particle partitioning of pesticides remains limited, hindering a comprehensive understanding of their abundance, transport, and health risks. Here, we aim to elucidate the underlying mechanism of gas-particle partitioning for pesticides. In this study, 14 pairs of air and particulate matter samples were collected simultaneously in Quzhou County, the NCP. A total of 19 pesticides were observed in both gas and particulate-phases. Average pesticide concentrations in particulate phase (2025.76 ± 1048.83 pg/m³) were significantly higher than in gas phase (143.38 ± 146.31 pg/m³), accounting for 93.4 % of the total atmospheric pesticide mass. Tebuconazole (662.49 ± 448.52 pg/m³), pyraclostrobin (212.01 ± 119.70 pg/m³), and carbendazim (158.68 ± 86.54 pg/m³) exhibited the highest concentrations in the particulate phase, whereas pyrimethanil (93.00 ± 79.18 pg/m³), pymetrozine (22.96 ± 21.50 pg/m³), and imidacloprid (5.78 ± 2.64 pg/m³) were predominant in the gas phase. A positive correlation between temperature and particulate-phase pesticide concentrations was found, as indicated by rising of logK_p values which is likely attributable to an interplay of pesticide physicochemical properties, ambient relative humidity, particle phase state and pesticide use patterns. Gas-particle partitioning model simulations showed absorption as the main mechanism of gas-particle partitioning, indicating atmospheric pesticides are absorbed into the interior organic film of particulate matter.