Increases of Total Mercury and Methylmercury Releases from Municipal Sewage into Environment in China and Implications

Abstract

As a globally transported pollutant, mercury (Hg) released from human activity and methylmercury (MeHg) in the food web are global concerns due to their increasing presence in the environment. In this study, we found that Hg released from municipal sewage into the environment in China is a substantial anthropogenic source based on mass sampling throughout China. In total, 160 Mg (140-190 Mg, from the 20th percentile to the 80th percentile) of Hg (THg) and 280 kg (240-330 kg) of MeHg were released from municipal sewage in China in 2015. The quantities of released THg and MeHg were the most concentrated in the coastal regions, especially in the East, North and South China regions. However, the per capita release of THg and MeHg was the highest in the Tibetan region, which is recognized as the cleanest region in China. THg released into aquatic environments was mitigated from 2001 to 2015 in China, but the amounts released into other sinks increased. This study provides the first picture of the release of Hg from municipal sewage into various sinks in China, and policy makers should pay more attention to the diversity and complexity of the sources and transport of Hg, which can lead to Hg accumulation in the food web and can threaten human health.

Impact of Water-Induced Soil Erosion on the Terrestrial Transport and Atmospheric Emission of Mercury in China

“…The increase indicates that terrestrial ecosystems in China have received extensive inputs of anthropogenic THg (including direct and legacy sources) in the last several decades. 27,47 A previous study found that 530 Mg of anthropogenic THg was emitted into the atmosphere in 2014 in China and had increased rapidly from 250 Mg in 1990, consistent with our estimates on the increasing rate. 24 However, the THg release from direct industrial sources into surface soils still lacks adequate quantification in China.…”

“…The concentration in Tibet around 2010 was 2.6-fold higher than that around 1990 due to the increase in human activity in this area; for example, it has the highest per capita THg release from domestic sewage among all provinces in China. 27 …”

“…26 We also modeled the flux of eroded soil THg induced by water erosion in 31 provinces based on the administrative division in China (except Taiwan Province, Hong Kong and Macao). 27 In eq 1, C THg ,j ( x ) is the probabilistic distribution of the surface soil THg concentration (ng/g) in county j . The concentrations of soil THg followed log-normal distributions that were considered in the uncertainty analysis based on the Monte Carlo method in this study.…”

“…26,27 Details of parameter settings are provided above. Median values and the 60% confidence intervals (ranging from 20% to 80%) of the statistical distributions were modeled to quantify the THg fluxes and to characterize the uncertainty ranges.…”

“…25 In recent papers, we have quantified that 110 Mg of THg was released from direct anthropogenic sources into the aquatic environment in China in 2015. 26,27 While the terrestrial ecosystem is an important source for the aquatic environment, to our knowledge, however, quantification of the THg amount released from natural processes into the aquatic environment has not been adequately studied in China.…”