| As a highly toxic trace heavy metal pollutant,mercury is widely found in the atmosphere,land,water,and marine ecosystems,posing a great threat to human health and ecosystem security.China's coal-fired units are an important source of atmospheric mercury emissions,accounting for 47%of China's anthropogenic mercury emissions.Among them,coal-fired power plants account for half of coal consumption and are one of the largest sources of mercury emissions.This paper selected Qianbei power plant located in Jinsha county,Bijie prefecture,Guizhou province as the research object and collected samples of particulate matters(TSP,PM100 and PM2.5)with different particle sizes at five sampling points in different directions and distances around the coal-fired power plant,the concentrations of mercury in particulate matters and its ExPM?exchangeable particle-phase mercury?,HPM?hydrochloric soluble particle-phase mercury?,EPM?elemental particle-phases mercury?and RPM?residual particle-phase mercury?were measured by a cold atomic fluorescence mercury analyzer,and to analysis the pollution levels and characteristics of particulate matters,the temporal and spatial distribution of total mercury and its mercury species in particulate matters and discuss the distribution and proportion of mercury species in particulate matters.in order to provide basic data for the study of mercury in atmospheric particulates of coal power plants,it was of great significance to prevent and control mercury pollution in regional environment.The main findings were as follows:?1?During the sampling period,the mass concentrations of TSP,PM100 and PM2.5inthestudyareawere53.28405.32?g/m3,40.30341.39?g/m3and37.26206.41?g/m3,the average mass concentrations were 156.50±63.53?g/m3,103.08±43.46?g/m3 and 82.53±30.95?g/m3,and exceeding standard rates were 15%,39%and 70%,respectively,The pollution level of particulate matters was PM2.5>PM10>TSP.The spatial-temporal distribution showed that the average mass concentrations of TSP,PM100 and PM2.5.5 in winter and autumn were higher than that in spring and summer,for spatial variations,the concentrations of mercury collected at upwind direction were much lower than that at the downwind direction,mercury concentrations at dominant wind direction were generally higher than that at the non-dominant wind direction,the coal fired power plant,local wind direction and the location of sampling point had great influence on it.?2?The average annual volume concentrations of total mercury in TSP,PM100 and PM2.5.5 were 171.15324.40pg/m3,97.46233.30pg/m3 and 91.37183.39pg/m3,the average values were 262.39±59.82pg/m3,190.27±57.31pg/m3 and 139.85±33.50pg/m3,mass concentrations were 0.901.99?g/g,1.042.25?g/g and 1.162.62?g/g,the average values were 1.42±0.43?g/g,1.81±0.49?g/g and 2.11±0.59?g/g,respectively.The volume concentrations of total mercury in particulate matters were TSP>PM10>PM2.5,which were higher than some domestic and foreign cities and higher than the background concentrations,indicating that the study area had been contaminated by mercury.The ratios of PM2.5/PM100 and PM10/TSP of mercury in the samples were 35.41%99.64%and 48.11%99.80%,the ratios of PM2.5/PM100 and PM10/TSP in particulate matters were 55.74%95.67%and 46.70%88.46%,respectively.This indicated that the mercury in the study area was more likely to be concentrated in PM2.5.The spatial-temporal distribution showed that the volume concentrations of total mercury in TSP,PM100 and PM2.5.5 in winter and autumn were significantly higher than that in spring and summer,which was related to the local wind direction,meteorological factors,the location of sampling point,boiler operation conditions,the spatial distribution of total mercury in TSP,PM100 and PM2.5showed a similar pattern to that of particulate matters.?3?Chemical continuous extraction method was used to extract different mercury species in particulate matters.The concentrations of ExPM,HPM,EPM and RPM in TSP,PM100 and PM2.5.5 were different from that in other parts of the country,which was related to the location of sampling point,pollution source and meteorological factors.Seasonal distribution showed that the volume concentrations and mass concentrations of ExPM,HPM,EPM and RPM in TSP,PM100 and PM2.5.5 in winter and autumn were significantly higher than that in spring and summer.Among them,the maximum volume concentrations of ExPM,HPM,EPM and RPM were 86.59pg/m3?winter?,243.84pg/m3?winter?,107.10pg/m3?autumn?and 58.05pg/m3?autumn?,the mass concentrations were 0.51?g/g?autumn?,1.25?g/g?winter?,1.02?g/g?winter?and0.77?g/g?autumn?.?4?The particle size distribution and proportion of mercury species showed that the proportion of HPM in particulate matters was larger?the average value was50.18%?,followed by EPM?the average value was 21.03%?,the ExPM and RPM were relatively lower?the average values were 15.58%and 13.21%?.Among them,ExPM and EPM were mainly concentrated in particles with a particle size?10?m?the average values were 15.92%and 21.53%?.Spatial distribution showed that the annual average concentrations of ExPM and HPM in TSP,PM100 and PM2.5.5 were higher in 2#,3#and 4#,EPM were in 2#,3#and 5#,and RPM were in 3#,4#and 5#.Among them,the maximum concentrations of ExPM,HPM,EPM and RPM appeared in winter 4#?133.13pg/m3?,winter 2#?370.28pg/m3?,autumn 5#?145.79pg/m3?and autumn4#?94.42pg/m3?. |
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