Dioxins in the Arctic: local sources vs. long-range transport†

With a unique geographical location and a fragile ecological environment, the Arctic has been a major concern of contamination by persistent organic pollutants (POPs), such as dioxins, also termed polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) due to their high toxicity. Under the influence of global warming, increasing wildfires have occurred in northern territories of the Northern Hemisphere (NH) in the recent decade. Given the proximity of these natural sources, the Arctic is likely subject to growing risks of local and nearby wildfire emissions of POPs. By implementing an updated global PCDD/Fs atmospheric emission inventory from 2011 to 2020 into an atmospheric transport model, we quantitatively assessed the PCDD/Fs pollution in the Arctic atmosphere. We explored the impact of wildfire combustion on PCDD/Fs pollution in the Arctic atmosphere and evaluated the relative significance of local and remote emissions from wildfire and anthropogenic sources. The results revealed that PCDD/Fs emissions from wildfire sources played an increasingly important role in PCDD/Fs pollution in the Arctic, contributing to about 70% of PCDD/Fs concentrations in Arctic air in 2020. Within the Arctic circle, wildfire emissions have also exceeded anthropogenic emissions since the late 2010s. This study provides data support for further assessment of wildfires' impact on the Arctic region's ecological environment and valuable information for assessing the effectiveness of PCDD/Fs (and other POPs) emission control.