PCDD/Fs and PCBs scavenged through cloud water during northeast monsoon

Although numerous studies have explored the capacity of cloud/fog water to scavenge atmospheric pollutants, research specifically focused on chlorinated persistent organic pollutants (Cl-POPs), such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs) within cloud/fog water remains limited. In this study, we aim to investigate the characteristics, partitioning, and scavenging efficiency of Cl-POPs in cloud/fog water by deploying active and passive cloud/fog collectors on Mt. Bamboo in northern Taiwan during the northeast monsoons of 2018-2019. To ensure accurate detection, we collected cloud/fog water samples ranging from 2.84 to 20.9 liters in volume. Our findings unveiled cloud/fog water's significantly higher Cl-POP concentrations compared to precipitation, highlighting its superior scavenging ability attributed to a larger surface-to-volume ratio. PCDD/Fs were predominantly observed in the particle phase (79 %), whereas PCBs were in the dissolved phase (>50 %). The scavenging ratio (SR) of the total PCDD/Fs in cloud/fog water (10⁴-10⁷) surpassed that of precipitation (10³-10⁵). Conversely, PCBs in precipitation fell within the same range in our data sets (10³-10⁵). Our study illustrates the critical role of cloud/fog water in scavenging Cl-POPs from the atmosphere and the potential transport of these pollutants, which can have implications for the environment and human health.