Explore the vast range of titles available.

Environmental mercury (Hg) contamination is a global concern requiring action at national scales. Scientific understanding and regulatory policies are underpinned by global extrapolation of Northern Hemisphere Hg data, despite historical, political, and socioeconomic differences between the hemispheres that impact Hg sources and sinks. In this paper, we explore the primary anthropogenic perturbations to Hg emission and mobilization processes that differ between hemispheres and synthesize current understanding of the implications for Hg cycling. In the Southern Hemisphere (SH), lower historical production of Hg and other metals implies lower present-day legacy emissions, but the extent of the difference remains uncertain. More use of fire and higher deforestation rates drive re-mobilization of terrestrial Hg, while also removing vegetation that would otherwise provide a sink for atmospheric Hg. Prevalent Hg use in artisanal and small-scale gold mining is a dominant source of Hg inputs to the environment in tropical regions. Meanwhile, coal-fired power stations continue to be a significant Hg emission source and industrial production of non-ferrous metals is a large and growing contributor. Major uncertainties remain, hindering scientific understanding and effective policy formulation, and we argue for an urgent need to prioritize research activities in under-sampled regions of the SH.

The atmospheric deposition of mercury (Hg) occurs via several mechanisms, including dry and wet scavenging by precipitation events. In an effort to understand the atmospheric cycling and seasonal depositional characteristics of Hg, wet deposition samples were collected for approximately 5 years at 17 selected GMOS monitoring sites located in the Northern and Southern hemispheres in the framework of the Global Mercury Observation System (GMOS) project. Total mercury (THg) exhibited annual and seasonal patterns in Hg wet deposition samples. Interannual differences in total wet deposition are mostly linked with precipitation volume, with the greatest deposition flux occurring in the wettest years. This data set provides a new insight into baseline concentrations of THg concentrations in precipitation worldwide, particularly in regions such as the Southern Hemisphere and tropical areas where wet deposition as well as atmospheric Hg species were not investigated before, opening the way for future and additional simultaneous measurements across the GMOS network as well as new findings in future modeling studies.

Mercury (Hg) speciation and bioavailability were studied in surface water, surface sediment and freshwater fish samples collected upstream and downstream of the Medupi (currently under construction) and Matimba power stations in the Waterberg area, Limpopo Province. The initial survey was conducted in May 2010 and continued periodically/seasonally until October 2014. This study was designed to provide an overall description of the levels of Hg in areas potentially impacted by emissions from the coal-fired power station and provide the necessary information to enhance the understanding of the factors regulating the fate and transport of Hg in the environment. Percent loss on ignition (LOI) and ancillary water quality measurements were also carried out. In this study, the total mercury (TotHg) concentrations ranged between 0.92 and 29.13 ng/L, and 0.13 and 8.00 ng/L for methylmercury (MeHg) in water. Total Hg concentrations ranged between 0.50 and 28.60 ng/g, while the MeHg concentration ranged between 0.08 and 2.22 ng/g in sediments. Mercury concentrations in fish ranged between 40 and 1200 ng/g for TotHg, and 13.42 and 600 ng/g for MeHg. Methylmercury concentrations in freshwater fish sampled exceeded the United States Environmental Protection Agency criteria (300 ng/g) in 10% of the total fish sampled and 5% exceeded the WHO guideline (500 ng/g).