Characteristics And Sources Of Atmospheric Mercury In Typical Urban Area Of Yunnan Province

Mercury can cause extreme damage to organisms,and its special physicochemical properties enable it to migrate and transform in the ecological environment.Mercury is the only heavy metal listed in international environmental conventions.China is the world’s largest producer,user,and emitter of mercury,and it faces greater pressure to prevent and control mercury pollution.Non-ferrous metal smelting is the main source of atmospheric mercury non-coal anthropogenic emissions in Yunnan Province.This study selected the main urban area and the Chenggong new urban area of Kunming City,which is the capital of Yunnan Province.the Mengzi City,a non-ferrous metal smelting industry in Yunnan Province,the Zhaotong City,which is rich in coal production and use,For the research object,set up four monitoring points.By monitoring the urban areas atmospheric mercury content and anthropogenic emissions,the distribution characteristics and influencing factors of urban atmospheric mercury concentration are analyzed,the main sources of mercury in different cities were studied based on the characteristics of urban atmospheric mercury concentration and anthropogenic emission.Following is the main results of this study:The average concentration of total gaseous mercury(TGM) in four urban areas in Yunnan Province order was:Mengzi(1.99±3.17)ng/m~3,Zhaotong(1.69±1.5)ng/m~3,Kunming(1.2±0.99)ng/m~3,Chenggong new town of Kunming(0.71±0.47)ng/m~3.The mean concentrations of TGM in Mengzi was significantly elevated above the continental background(1.5～1.7ng/m~3) in Northern Hemisphere,which was close to that in Zhaotong,while the concentration level in the Chenggong new town of Kunming was the lowest.Affected by emissions from non-ferrous metal smelting and other industrial sources,the temporal change of TGM in Mengzi is different from others.The seasonal changes are higher in summer and autumn than in winter,and the daily changes are higher in daytime than at night.Affected by the large amount of coal-fired emissions in the cold season,the TGM content of Zhaotong in autumn and winter is significantly higher than that in spring and summer.Temperature and wind speed are the main meteorological factors that affect the change of TGM concentration.The TGM concentration decreases after sunrise and rises after sunset,which is related to the change in the height of the atmospheric boundary layer caused by temperature changes.At higher wind speeds,it helps the diffusion of atmospheric pollutants Therefore,the concentration of TGM is reduced,but due to the effects of anthropogenic point source emissions,the transmission of mercury-containing gas masses at a specific wind speed downwards will also affect the concentration of TGM at the monitoring point.A study on the source of atmospheric mercury in the pollution events found that the mercury pollution incident in the Kunming main city and Chenggong was greatly affected by the transport of the emissions of biomass combustion sources in Southeast Asia.The mercury pollution incident in summer and autumn in Mengzi was caused by industrial source emissions.During the winter monitoring period,there was no significant industrial source emissions,which was greatly affected by biomass combustion emissions.The mercury pollution incident in autumn and winter in Zhaotong is affected by both industrial source emissions and civil bulk coal emissions.The results of sampling and analysis of mercury concentration in industrial source indicate that the non-ferrous metal smelting,chemical industry,and cement production are the main anthropogenic mercury emission sources.In addition,vehicle emissions are also the main anthropogenic mercury emission sources.The concentration of TGM in the non-ferrous metal smelting and chemical industry plant boundary environment is relatively high,and the health risks of workers exposed in a lead-zinc smelting plant are the greatest.