Pollutant Characteristics Of Heavy Metals Indoors And Health Risk Assessment On Campus

With the development of the social economy,the atmosphere air quality of our country is facing a severe test.Because of the strong infiltration ability of fine particles,the indoor air quality is seriously affected.Human beings spend most of their time indoors,and the indoor air quality is closely related to human health.Therefore,it is of great significance to study the health risk exposure of indoor PM2.5.In order to have a better understanding of college students'indoor PM2.5 health risk exposure during the school,two typical indoor PM2.5 samples were measured in the urban Campus student offices and dormitories in Nanjing.Samples were analyzed by an inductively coupled plasma optical emission spectrometer(ICP-OES)for As,Cd,Cr,Cu,Fe,Mn,Ni,Pb and Zn.This study used enrichment factor,geoaccumulation index and potential ecological risk method to assess the pollution degree of heavy metals,respectively;and used I/O ratio and linear regression method to study the effect of outdoor PM2.5 and heavy metals on the indoor PM2.5 and heavy metals;and then used the correlation matrix and PMF receptor model analysis to to qualitatively estimate the main source of indoor PM2.5;Finally,Monto Carlo simulation and health risk assessment model of US EPA for College students health risk assessment were exploited.The experiment results show that:PM2.5 pollution in the dormitories had obvious winter and summer characteristics,and the mass concentrations of PM2.5 in dormitories were lower than that in the ambient.During the period of winter sampling,the average mass concentration of PM2.5 of the dormitoriy was 2.05 times as high as that in summer.The mass concentrations of PM2.5 in the dormitories in winter were between 32.00?31.00?g/m3,and the average mass concentration of PM2.5 was(83.44±31.00)?g/m3.During the summer sampling period,the mass concentrations of PM2.5 in the dormitories were between 19.62?96.67?g/m3,and the average mass concentration of PM2.5 was(40.67±17.33)?g/m.And during the summer sampling,the pollution degree of students' dormitories was more serious than that of the students' office.During the period of winter sampling,Fe had the highest average mass concentration in the dormitory,which was(670.58±256.17)ng/m3,followed by Zn>Pb>Cr>Mn>Cu>As>Ni>Cd.During the summer sampling,Fe also had the highest average mass concentration in the dormtoriy,which was(265.54±100.51)ng/m3,followed by Zn>Pb>Mn>Cu>Cr>As>Ni>Cd.The pollution characteristics of Cr in winter and summer were obvious differences,and the average mass concentrations of heavy metals in the student office were lower than that of the dormitory during the summer sampling period.The results of enrichment factor,geoaccumulation index and potential ecological risk method pollution assessment showed that the contamination of Cd indoors was extremely strong,and the pollution degree of heavy metals indoors was higher than that of outdoor.During the summer sampling,compared with the student's office,the pollution degree of dormitory was more serious.The results of I/O ratio and linear regression showed that the source of PM2.5 in the dormitory came from indoors and outdoors,and the concentration of PM2.5 in the dormitory was strongly influenced by outdoor PM2.5.The indoor-outdoor infiltration coefficients of the heavy metals were not obvious in winter and summer,but the indoor source contribution rate to dormitory pollution in summer was greater than that in winter.The results of correlation matrix showed that the correlation coefficients between heavy metals in the dormitory in summer were lower than that in winter.Indoor source had certain contribution to heavy metals in dormitory,which resulted the correlation coefficients between heavy metals in the dormitory were not as remarkable as outdoor.And the correlation coefficients between heavy metals in the student office were also stronger than that in dormitory.The results of PMF analysis showed that the sources of indoor and outdoor PM2.5 were mixed sources during the sampling period,and the sources of heavy metals mainly include industrial process,soil/dust source,fuel and coal mixed source.During the winter and summer,vehicle emission was the largest source of PM2.5 in both the indoor and outdoor.The results of health risk assessment showed that the non-carcinogenic hazard of heavy metals in PM2.5 in the dormitory for college students can be neglected.Therfore,Mn and Cr had the maximum health risk,and Ni had the minimum health risk in the dormitory during the sampling time.In winter,Cr had potential harm to the health of college students in the dormitory,and the average carcinogenic risk was greater than 1.00E-06.The non-carcinogenic risk and carcinogenic risk of heavy metals in the dormitory PM2.5 in winter were greater than those in summer.During the summer sampling,the non-carcinogenic risk and carcinogenic risk of heavy metals in the dormitory and office were also in the safe limits.However,the non-carcinogenic risk and carcinogenic risk indoor were five times higher than the outdoor.