[Temporal and spatial variation of mercury in water of agro-forestry and livestock compound watershed in the three Gorges Reservoir Area].

ABSTRACT

The temporal and spatial distribution of mercury (Hg) in four different sources of stream (aquaculture wastewater, bare land, forestry land and agro-forestry land) and well water of an agro-forestry and livestock compound watershed in the Three Gorge Reservoir region was studied during the period from March 2013 to March 2014. The total mercury (THg) concentrations ranged 9.95-15.26 ng x L(-1) with an average of (11.95 +/- 1.87) ng x L(-1), and the THg concentration decreased in the order of bare land > aquaculture wastewater> forestry land > agro-forestry land > well water. The total methylmercury (TMeHg) concentrations ranged 0.120-0.441 ng x L(-1) with an average of (0.232 +/- 0.099) ng x L(-1), and the TMeHg concentration decreased in the order of aquaculture wastewater > agro-forestry land > forestry land > bare land > well water. THg and TMeHg in well water were both dominated by the dissolved fraction, whereas for other sources of stream, the particulate phase accounted for the major fraction of THg and TMeHg. The THg concentrations in winter and spring were significant higher than those in summer and fall, however, no obvious seasonal trend of TMeHg distribution was observed. Comprehensive analysis showed human activities and weather conditions such as air temperature and precipitation etc. were the main reasons for the difference of temporal and spatial distribution of THg and TMeHg.