Contamination Level And Source Apportionment Of PM_2.5 In Residential Indoor Of Zhuzhou

Most People usually spend most of their time in various indoor environments.Indoor air quality?IAQ?affects human health directly or indirectly.Indoor air quality standards in some countries or regions impose limits on PM_2.5 concentrations and heavy metal elements.However,there is currently a lack of relevant research on the investigation,source analysis and health risk assessment of domestic residential PM_2.5.Therefore,this paper studies the monitoring and investigation of PM_2.5 pollution levels,its chemical components,its pollution sources and human exposure to PM_2.5.5 of urban residential buildings in Zhuzhou city,the research results have certain practical significance for PM_2.5 pollution control and control in this region.Zhuzhou is a typical industrial city.Four households with no mechanical ventilation are selected in different geographical locations in Zhuzhou City for indoor and outdoor PM_2.5 mass concentration and inorganic element sampling observations for one year.The current situation of urban outdoor air pollution is studied based on the monitoring data from local Environmental Protection Agency.The pollution level of residential indoor PM_2.5 and the composition characteristics of its heavy metal elements in different seasons are analyzed by sampling.First,the enrichment factor analysis?EF?method is adopted.Then,principal component analysis with multivariate linear regression?PCA/MLR?and positive definite matrix factorization?PMF?model are used to further analyze the PM_2.5 source.Finally,a comprehensive health risk assessment model based on questionnaires is conducted.The conclusion are shown as follows:The residential indoor PM_2.5.5 concentration in Zhuzhou City is77.83+42.93?g/m³?the average value is slightly higher than the National Grade II standard of 75?g/m³?,and the outdoor is 64.43+46.37?g/m³.The mass concentration of PM_2.5 sampled in the indoor environment without mechanical auxiliary ventilation is higher than that of PM_2.5 at the same time in the corresponding residential outdoor environment,indicating that the indoor PM_2.5 pollution level is more serious than outdoor.However,in the case of heavily polluted haze,the mass concentration of PM_2.5 in the room is significantly lower than that in the outdoor.The total average quality level of inorganic heavy metal elements in indoor and outdoor residential buildings is divided into three parts:main components?Ca,Mg,Fe,Zn,Ti?,secondary components?Pb,Mn,V,Cr,Cu,As,Ni?and Trace components?Cd,Co,Mo?;The average total mass of trace metal elements analyzed in indoor PM_2.5 is higher than that of outdoor.The seasonally significant level of metal components in indoor PM_2.5 samples is significantly weaker than that in outdoor PM_2.5.The annual average values of indoor and outdoor contents of Cr,Cd and As exceeded relevant upper limit values of the national Environment Air Quality standard?GB3095-2012?.There are regional distribution characteristics of PM_2.5 inorganic element content in each outdoor sampling point,especially in winter.The key outdoor pollution factors for residential outdoor air in Shifeng District are industrial sources and combustion sources,which still make an important contribution in outside Zhuzhou City.The characteristics of outdoor air heavy metal pollution sources in the Hetang District and Shifeng District in autumn and winter are relatively close.In terms of indoor enrichment,Ca,Mg,Mn,Ti,and Co elements are less enriched and less affected by humans.V and Ni are moderately enriched;Cu and Cr elements are significantly enriched,and Cd,Mo,Pb,Zn and As elements are heavily enriched.The PCA/MLR analysis results show that the indoor PM_2.5 sources are mainly indoor soil dust sources,coal-fired fuel sources,industrial process sources,smoking smoke sources,indoor cooking smoke sources,and motor vehicle exhaust sources.Their contribution rates are 29.7%,27.1%,20.1%,13.6%and 9.5%,respectively.Outdoor sources are mainly coal-fired fuel sources,comprehensive sources of transportation,building dust sources,industrial process sources,and other sources,with the contribution rates of 26.9%,23.5%,19.1%,18.8%,and 11.6%,respectively.PMF analysis results show that the indoor sources are mainly cooking smoke and combustion sources,indoor soil dust sources,industrial process sources,garbage combustion sources,and motor vehicle exhaust sources.Their contribution rates are 40.3%,23.8%,23.7%,9.6%,and 2.6%,respectively.Outdoor sources are mainly integrated transportation sources,coal-fired fuel sources,industrial process sources,building dust sources,and other sources.Their contribution rates are 34.7%,24.7%,15.8%,15.7%,and 9.1%,respectively.Outdoor PMF and PCA/MLR analysis of PM_2.5.5 sources are roughly the same,mutual proof,with good consistency.However,the results of analyzing indoor PM_2.5 sources are quite different,and the indoor sources are more complicated and further research is needed.Based on the comprehensive risk assessment of indoor and outdoor exposure concentration and residence time distribution,the study shows that the average indoor exposure risk of non-carcinogenic and carcinogenic risks of human body is 8.5 times that of outdoor.The health exposure risk of Co element in indoor air PM_2.5.5 is the largest,while the Cr element in outdoor air PM_2.5 is a more significant risk factor.Mn element has certain non-carcinogenic risk to human body,while Cr,As,Ni,Co and Cd elements have certain carcinogenic risks.In addition,uncertainty studies indicated that Mn and Cr have potential non-carcinogenic risks,while Co and Ni have potential cancer risk.The above results show that the indoor concentration of PM_2.5without mechanical ventilation is more common than that of outdoor.The defense effect of ordinary residential enclosures on fine particulate matter is not great.The weakening of residential ventilation in autumn and winter and the contribution of indoor sources have increased the pollution of indoor PM_2.5.The analysis of inorganic elements show that there are some characteristic elements in indoor and outdoor,which are affected by human activities,that is,the localization characteristics of elemental components are more obvious.The health risks of exposure to PM_2.5mainly occur in the indoor environment.Therefore,it is necessary to pay more attention to the distribution characteristics of inorganic elements in indoor PM_2.5,especially the main contributing elements in the room and the control of pollution sources.