Research Highlights

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  • Earth & environment

Published online: 18 January 2007 | doi:10.1038/nchina.2007.070118-1

Atmospheric mercury: How clean is the air you breathe?

Nicki Stevens

Introduction

How clean is the air you breathe?  Background levels of atmospheric mercury in Guiyang, capital of Guizhou Province, are up to five times greater than average Northern Hemisphere levels. Air pollution is a pressing problem in this expanding industrial city of over 3.5 million people.

Human activity, namely coal burning, was previously blamed for the high levels of atmospheric mercury.  However, researchers showed that around 40% of airborne mercury in Guiyang is emitted naturally from local soils. 

Guiyang is located in the Circum-Pacific Global Mercuriferous Belt, and the soil is naturally enriched with mercury. Xinbin Feng and colleagues from the Chinese Academy of Sciences measured mercury evaporation directly from the soil. They found that the rate of emission is weather-dependent: it increases with the Sun's radiance, with peak emissions coinciding with midday on sunny days. Rain showers also enhance mercury evaporation rates, but to a lesser extent. The cycle reverses at night, when soil re-absorbs mercury vapour.  They used their observations to model the annual flux, and calculated that 408 kg per year of atmospheric mercury in Guiyang originates from natural sources¹.

Authorities recognize the importance of mitigating air pollution health risks, and an environmental management strategy involving a circular, or recycling, economy, was implemented in recent years by the State Environmental Protection Administration.  Targets are set for cleaning up industrial emissions and switching to other energy sources. Xinbin's research provides a new insight into the origin of a significant proportion of Guiyang atmospheric mercury.

References

1. Feng, X. B. et al. Total gaseous mercury emissions from soil in Guiyang, Guizhou, China. J. Geophys. Res. Atmos. 110, D14306 (2005). | Article |