China took aggressive air pollution control measures from 2013 to 2017, leading to the mitigation of atmospheric mercury pollution as a cobenefit. This study is the first to systematically evaluate the effect of five major air pollution control measures in reducing mercury emissions, the total gaseous mercury (TGM) concentration and mercury deposition flux (FLX) for unit emissions reduction. From 2013 to 2017, China’s mercury emissions decreased from 571 to 444 tons, resulting in a 0.29 ng m–3 decrease in the TGM concentration, on average, and in a 17 μg m–2 yr–1 decrease in FLX. Ultralow emission renovations of coal-fired power plants are identified as the most effective emission abatement measure. As a result of this successful measure, coal-fired power plants are no longer the main mercury emitters. In 2017, the cement clinker sector became the largest emitter due to the use of less effective mercury removal measures. However, in terms of the mitigated TGM concentration and FLX levels per unit emission abatement, newly built wet flue gas desulfurization (WFGD) systems in coal-fired industrial boilers have become particularly effective in decreasing FLX levels. Therefore, to effectively reduce atmospheric mercury pollution in China, prioritizing mercury emissions control of cement clinkers and coal-fired industrial boilers is recommended.

Mercury (Hg) deposition through litterfall has been regarded as the main input of gaseous elemental mercury (Hg0) into forest ecosystems. We hypothesize that earlier studies largely underestimated this sink because the contribution of Hg0 uptake by moss and the downward transport to wood and throughfall is overlooked. To test the hypothesis, we investigated the Hg fluxes contributed via litterfall and throughfall, Hg pool sizes in moss covers and woody biomass as well as their isotopic signatures in a glacier-to-forest succession ecosystem of the Southeast Tibetan Plateau. Results show that Hg0 depositional uptake and pool sizes stored in moss and woody biomass increase rapidly with the time after glacier retreat. Using the flux data as input to a Hg isotopic mixing model, Hg deposition through litterfall accounts for 27–85% of the total accumulation rate of Hg0 in organic soils of glacial retreat over 20–90 years, revealing the presence of additional sources of Hg0 input. Atmospheric Hg0 accounts for 76 ± 24% in ground moss, 86 ± 15% in tree moss, 62–92% in above ground woody biomass (branch–bark–stem), and 44–83% in roots. The downward decreasing gradient of atmospheric Hg0 fractions from the above ground woody biomass to roots suggests a foliage-to-root Hg transport in vegetation after uptake. Additionally, 34–82% of atmospheric Hg0 in throughfall further amplifies the accumulation of Hg0 from atmospheric sources. We conclude that woody biomass, moss, and throughfall represent important Hg0 sinks in forest ecosystems. These previously unaccounted for sink terms significantly increase the previously estimated atmospheric Hg0 sink via litterfall.