The Concentration Of Water-Soluble Ions&Heavy Metals And Human Health Risk In Atmospheric PM_2.5 Of Tianjin

The pollution of water-soluble ions and heavy metal elements in atmospheric fine particulate matter(PM2.5)has been paid close wide attention widely.It is of very important to research physical and chemical characteristics,source analysis and health risk in PM2.5.In this work.PM2.5 was collected from November 2017 to July 2018.The concentrations of water-soluble ions and heavy metals were determined.The concentrations and seasonal distribution of water-soluble ions and heavy metals were researched.The sources were estimated by enrichment factor method,correlation analysis and principal component analysis.The health risk of heavy metals in PM2.5 were assessed by a health risk model.The conclusions are as follows:(1)The concentration of PM2.5 was measured and calculated using a particle counter.The results show that 24-hour average concentration of the atmospheric PM2.5 in Tianjin is 66.67?g·m-3,which is lower than the secondary standard of 24-hour average concentration in China.The order of seasonal concentration is:winter>spring>autumn>summer.The maximum of PM2.5 concentration is observed in March,mainly related to sandstorm weather.The average concentration of PM2.5 is highest in winter that related to boundary layer stability and coal-burning contribution.The PM2.5 concentrations in summer and autumn are lower than the other seasons that mainly related to high temperature,precipitation and reduction of sources.The average concentration of atmospheric PM2.5 in Tianjin is far higher than that in many foreign cities and domestic southern cities.However it was litter different from that in some northern cities in our country.(2)The water-soluble ions in PM2.5 were determined by a ion chromatography and a Inductive Coupled Plasma Optical Emission Spectrometer(ICP-OES),respectively.The results show that the total average concentration of water-soluble ions is 35.63 ?g·m-3,accounting for 53.44%of PM2.5 mass.The order of water-soluble ions concentration is NO3->SO42->Cl->Ca2+>Na+>K+>F->Mg2+.NO3-,SO42-,Cl-and Ca2+are the main components of water-soluble ions accounting for 92.90%.The range of variation of NO3-concentration is the largest SO42-is the second,and F-is the smallest.The order of the eight water-soluble ion concentrations in different seasonal distributions are winter>spring>summer>autumn.The concentration order is winter>spring>autumn>summer.In the same season,the concentration level of each water-soluble ion and the range of the total ion are different.The seasonal distribution characteristics of the same water-soluble ions concentration are also different.(3)Correlation analysis and principal component analysis of water-soluble ions in PM2.5 indicates that F-,Cl-,NO3-,SO42-and K+ in Tianjin atmospheric PM2.5 are mainly caused by human activities,such as motor vehicles,coal buring.etc.with a contribution rate of 52%.Ca2+.Mg2+ and Na+ are mainly derived from natural sources such as soil dust,with a contribution rate of 36%.The cumulative contribution rate is about 88%.(4)The 16 heavy metal elements in atmospheric PM2.5 were determined by a ICP-MS.The results show that the order from high to low of each heavy metal concentration is Zn>V>Fe>As>Cr>Mn>Pb>Cu>Mo>Ni>Sb>Cd>Ag>Co>U>Th.The concentrations of Zn,V,Fe,As,Cr,Mn,Pb,Cu and Mo account for more than 1%of the total amount of heavy metals.The total concentration of Zn,V,Fe,As,Cr and Mn accounted for about 91%of the total amount of heavy metals.The concentration range of Zn,V,Ni,Cr,Co,Cu,As,Mo,Pb and Cd varied markedly.The concentration of As exceeded the secondary concentration reference limit,indicating that As in Tianjin atmospheric PM2.5 is serious pollution.At the same time,the total concentrations of 16 heavy metal elements show the order of seasonal distribution is winter>autumn>spring>summer,which show a less consistent change with the concentration of atmospheric PM2.5.The seasonal variation of the concentration of different heavy metals,the proportion of heavy metals and the range of variation are not consistent.The distribution and concentration range of the same heavy metal in different seasons are different,which may be related to different meteorological conditions,types and intensity of pollutant sources.(5)The order from high to low of total average EF of heavy metals is Fe>Cd>Ag>As>Mo>Sb>Zn>V>Cr>Pb>Cu>Ni>Co>U>Th.The EFs of Cd,Fe,Ag,As.Mo.Sb and Zn are greater than 100,indicating that the elements are heavily enriched and affected by human activities.The EFs of V,Cr,Pb,Cu and Ni are between 10 and 100,indicating that these elements are slightly enriched and affected by different degrees of human activities.The EFs of Mn.Co,U and Th are between 1 and 10,indicating that these elements are not enriched distinctly.The main sources of PM2.5 are natural sources,which are less affected by human activities.In addition,the enrichment factor of heavy metals show seasonal differences.There are mainly three sources of heavy metals in PM2.5 in Tianjin:the contribution rate of anthropogenic sources such as coal-fired sources and motor vehicle sources is about 40%.The contribution rate of soil dust sources is about 26%.The contribution rate of industrial sources is about 20%.The cumulative contribution rate of the sources is about 86%.(6)The human health risks were assessed using a health risk assessment model developed by the US Environmental Protection Agency's(US EPA).The results show that the order of Hazard Quotient(HQ)of children and adults from large to small in the non-carcinogenic health risk assessment follow by:As>Cr>Pb>Cd>Mn>Zn>Cu>Ni>Co.The HQ of each heavy metal in childern is higher than that in adults.The HQ of mouth intake is higher than that of skin contact and respiratory contact.It was worth noticed that the HQ of As in children only through hand intake is greater than the safety threshold of 1.0,and there is a potential non-carcinogenic risk.Through three ways,the hazard index(HI)of As is much higher than other elements.The order of risk is children>adult women>adult males.Children's HI is higher than adults.Adult women are slightly higher than adult males.The results of carcinogenic risk of heavy metals show that the incremental lifetime cancer risk(ILCR)order from high to low of single carcinogenic heavy metals in the respiratory pathway is Cr>As>Cd>Co>Ni.The same metal element have a higher ILCR for males than females,which may be related to the longer time for adult males to spend outdoor activities.The total ILCR of the five heavy metal elements was less than 10-6 for both male and female,which is lower than the level of carcinogenic risk.The total ILCR in PM2.5 in Tianjin do not have carcinogenic risk,but close to the risk threshold(10-6).It should be noted by people.