Field Evidence for Asian Outflow and Fast Depletion of Total Gaseous Mercury in the Polluted Coastal Atmosphere

Abstract

Atmospheric mercury (Hg) cycling in polluted coastal atmosphere is complicated and not fully understood. Here, we present measurements of total gaseous mercury (TGM) monitored at a coastal mountaintop in Hong Kong downwind of mainland China. Sharp TGM peaks during cold front passages were frequently observed due to Asian pollution outflow with typical TGM/CO slopes of 6.8 ± 2.2 pg m–3 ppbv–1. Contrary to the daytime maximums of other air pollutants, TGM exhibited a distinct diurnal variation with a midday minimum. Moreover, we observed four cases of extremely fast TGM depletion after sunrise, during which TGM concentrations rapidly dipped to 0.3–0.6 ng m–3 accompanied by other pollutants on the rise. Simulated meteorological fields revealed that morning upslope flow transporting anthropogenically polluted but TGM-depleted air masses from the mixed layer caused morning TGM depletion at the mountaintop location. The TGM-depleted air masses were hypothesized to result mainly from fast photooxidation of Hg after sunrise with minor contributions from dry deposition (5.0%) and nocturnal oxidation (0.6%). A bromine-induced two-step oxidation mechanism involving abundant pollutants (NO2, O3, etc.) was estimated to play a dominant role, contributing 55%–60% of depleted TGM and requiring 0.20–0.26 pptv Br, an amount potentially available through sea salt aerosol debromination. Our findings suggest significant effects of the interaction between anthropogenic pollution and marine halogen chemistry on atmospheric Hg cycling in the coastal areas.

Oxidative Immobilization of Gaseous Mercury by [Mo3S(S2)6]2–-Functionalized Layered Double Hydroxide

“…Since the industrial era began (∼1850) until 2010, North America has had the highest (30%) cumulative mercury discharges to the environment . The lifetime of atmospheric mercury against removals, such as deposition and recycling, is about six months, allowing transport on a hemispheric to global scale. ,, The atmospheric mercury drops down to soil and surface waters, where bacterial activities contribute to the formation of neurotoxic methyl mercury, which subsequently accumulates in humans and animals via the food chain. , The severe noxiousness of mercury enforces the US EPA to designate it as a highly toxic and hazardous air pollutant under the Clean Air Act Amendments (CAAA)…”

SEARC Mathematical Modeling of Drug Addiction in South Sulawesi Province

“…In the case of the spread of drug addiction, the SEIR model can be used to understand the dynamics of interactions between individuals who may be exposed to drugs, infected, and recovered [26]. This model helps to predict and understand trends in drug spread in the population [27], thus assisting in determining effective prevention and control strategies [28].…”