Global inter-regional contributions to PAH inventories and depositions, 1970-2018

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitously found organic pollutants, and human carcinogens. PAH emissions have been estimated to occur since the 1970s. There have been regional shifts in PAH emissions and the proportional contributions of different regions (Africa, Asia, Australia, Europe, and North and South America) to global emissions have changed substantially over time. To support international agreements, it is important to ascertain source-receptor relationships quantifying the contribution of one region to the contamination of another region, and to better track the shifts in regional contributions with changes in source locations. Here, we use a multimedia fate and transport model, BETR-Global, to estimate the time varying contributions of emissions of the PAHs, BaP, BbF, BkF and IcdP, in one region to the atmospheric deposition and terrestrial inventories in other regions, including the Arctic and Antarctica, for the period 1970-2018. Total PAH emissions were dominated by BbF and BaP (37% and 33%, respectively). Europe's relative and absolute contributions declined after the early 1990s, while Africa's absolute contribution to global deposition has increased. Depositions and inventories in North America, South America and Australia were dominated by contributions from within-region emissions. PAH deposition to the Arctic was higher compared to Antarctica. For the four PAHs combined, soil inventory was dominated by contribution from within-region emissions. Asia's self-contribution increased from 89% in 1990 to 94% in 2018. Europe's self-contribution declined from 94% to 85% in 1990 and 2018, respectively. Transboundary contributions to soil inventory were generally low, except for the Arctic, where Asia and Europe contributed a major part of the soil inventory of PAHs.