| Coal combustion is the main source of atmospheric particulate matters?PM?and iodine in the continental environments.Active iodine can promote nucleation of the secondary particles.Regarding the study on the trend of atmospheric PM mass concentration changes and iodine species in the atmosphere surrounding coal-fired power plant,it may not only help to further evaluate the impacts from coal combustiononatmosphericparticulatematterlevelsandcorresponding environmental effects but also clear the interaction mechanism between atmospheric PM and iodine.Xin-chang Power Plant and Huang-jinbu Power Plant were selected as the representatives of coal-fired to conduct the research in this paper,sampling points were set down along the prevailing wind direction with different distances from the power plant.Particulate iodine and gaseous pollutant samples were simultaneously collected using special equipment samplers.To evaluate the level of active iodine in atmosphere of coal-fired area,the concentrations of iodine were measured with ICP-MS.This may provide reference data for the generation of secondary particulate.At the same time,we determined the concentrations of some gaseous pollutants,such as SO2,NOX,NH3,VOCs;Moreover the interaction mechanism between atmospheric particles and active iodine were discussed systematically.As a control,Nanchang University was selected as the representative of noncoal-fired area,excepting for collecting PM and iodine during the same period of sampling in the coal-fired area,atmospheric PM2.5was also collected from April to November,2017.Samples were analyzed to determine the concentration of iodine.Fine particles and aerosol iodine were also analyzed to evaluate the concentration level of iodine in the urban atmosphere.Characteristics of daily and seasonal concentration distribution of iodine in fine particles were obtained.Meteorological factors were discussed to understand its effects on iodine.The study may propose a new idea for source apportionment of urban secondary particles.Particularly,it also contributes fundamental data to complete the system of evaluation of urban air quality monitoring.The research showed that atmospheric particles in the coal-fired area mainly composed of fine particles.Value range of TSP mass concentration in Xinchang power plant is 127190?g/m3,when that of PM2.5 is 69124?g/m3,PM2.5 accounts for TSP of 4499%;on the other hand,value range of TSP mass concentration in HuangJinbu power plant is 47202?g/m3,and that of PM2.5 is 36115?g/m3,accounting for TSP of 4490%.PM10 mass concentration showed a‘bimodal'trend,which peaked at 0.11?m and 12.5?m.Mass and number concentrations of PM1are in the highest for atmospheric particles.Secondary particles are the major contributors for atmospheric particles in coal-fired areas.At non-combustible coal areas,PM10mass concentration showed a‘single-peak'trend,which peaked at 0.11?m,indicating that it might greatly affected by traffic emission.The concentration of iodine in the coal-fired area is relatively high than that of non-coal fired area.The iodine concentration in Xin-chang power plant ranged from1.54 to 19.2 ng/m3,and in Huang-jinBu power plant from 5.70 to 39.9 ng/m3,particulate iodine has the highest concentration of all iodine species,followed by HI and I2.Concentrations of HOI are lower than the former,and the organic iodine varies greatly.Concentrations of particulate iodine are higher than that of gaseous iodine in coal-fired area.Iodine in the non-fired coal area showed an opposite trend with the level of gaseous iodine.Concentration of total iodine is 16.6 ng/m3,organic iodine is the major component of atmospheric iodine.Followed by particulate iodine,then HI and I2.High content level of iodine surrounding coal-fired area is obviously higher than that of non-combustible coal area,it indicated that coal combustion contributes to atmospheric iodine.Particulate iodine concentration is relevant to the mass concentration of particles.The mass concentration of particles increase followed by the the concentration of iodine.HI,I2 and organic iodine are gaseous iodine,they can directly volatilized to the air.HOI is the product from photochemical reaction of gaseous iodine,and both of them belong active iodine of atmosphere.The results showed non-fired coal area atmosphere have a higher level of active iodine than that have in coal-fired area.Total iodine concentration showed positive but not significant correlation with NOX,NH3 and VOCS Gaseous pollutants may effect the level of iodine.Total iodine concentration showed a significant correlation with SO2?R2=0.951,P<0.05?,atmospheric iodine and SO2 may emission from the same source,or iodine may effect the atmospheric process of SO2.According to the linear regression analysis,meteorological conditions such as temperature,humidity,and wind speed and direction also contributed to changes in the concentration of iodine.The article showed that the iodine level increased with the reduction of the PM mass concentration.Number and mass concentrations of submicron particles had a positive correlation with particulate iodine and HI,I2.It means that iodine may promote the growth of PM,especially fine particles.The results showed that the value of iodine of PM2.5 in Nan Chang Honggutan District is relatively low from April to November,2017.The value of iodine ranged from 0.20 to 11.0 ng/m3,and the highest iodine concentration of it appeared in November,which was?11.0±0.76?ng/m3.However,the value of iodine in coal-fired area was lower than that in the coal-fired area during the same period,which was?12.9±0.99?ng/m3.There was a significant positive correlation between the iodine concentrations and the PM2.5 mass concentration?R2=0.859,P<0.01?.Meteorological conditions had a great impact on the distribution of iodine.The article confirmed that the atmospheric iodine concentration of coal combustion area enriched the contents of environmental pollutants emission from the coal burning.Providing theoretical supporting for atmosphere,especially for the atmospheric environment in coal combustion area. |
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