Spatio-temporal variation of total mercury in precipitation in the largest industrial base in China: impacts of meteorological factors and anthropogenic activities

A 12-month investigation of total mercury (Hg) in event-based precipitation was performed in China’s biggest industrial base, Yangtze River Delta, a hotspot of anthropogenic Hg emissions. Concentrations of total Hg in precipitation were measured, and the spatial and temporal variations of Hg were addressed. The results show that Hg concentrations (median=92 ng L⁻¹) are comparable to the reports of other cities in China, but higher than those of remote sites. In spatial, Hg levels are significantly higher in urban and suburban precipitation than in rural samples. The pH, precipitation depth and antecedent drying period appear to be potential factors influencing Hg concentrations in precipitation, but in general no strong correlation was found between Hg and individual parameters. A seasonal variation of Hg in precipitation was found, and the concentrations in winter are generally higher, possibly associated with fossil fuel combustion. In addition, the dominant wind direction was found to be a factor influencing seasonal pattern of Hg by atmospheric transport of air pollutants. The backward trajectories suggest that local sources, for example, emissions from coal combustion and industry activities, are possibly important contributors to Hg in precipitation.