Characteristics And Health Risk Assessment Of Particulate Matter Pollution In Ambient Air Of Weinan

The research and utilization of national ambient air quality monitoring data is close to maturity now,providing good technical support for ecological environment governance.However,there are relatively few studies on the characteristics of particulate pollution and health risk assessment in Weinan City,which is located in the core area of the Fenwei Plain.Using the PM₁₀ and PM_2.5 concentration data in Weinan from January 2018 to December 2020,and the 6 kinds of heavy metals concentration data contained in PM_2.5 from September 2019 to August 2020,reveal the changes in the concentration of air particulate matter in the city,explore the regional transfer characteristics of air particulate matter in Weinan,and conduct health risk assessment research.It has certain guiding significance to improve the air quality,improve the health of the population and promote the sustainable development of the region.The daily changes of PM₁₀ and PM_2.5 in Weinan are"W"-shaped,the monthly average concentration of PM₁₀ and PM_2.5 showed"V"and"U"-shaped change.The peaks of PM₁₀ and PM_2.5 concentrations throughout the day appear at noon or night（around 10:00-13:00 and 21:00-02:00）,lower values appear in the early morning or afternoon（around 03:00-07:00 and 16:00-19:00）.The monthly average concentrations of PM₁₀ and PM_2.5 were lower in July to September and April to September respectively.Particulate pollution is mainly concentrated in the first and fourth quarters.Compared with 2018,the concentration of PM₁₀ in 2020 decreased by 25.2%,and the concentration of PM_2.5 decreased by 3.6%.The annual average concentration of PM_2.5in PM₁0 increased from 43.31%to 55.64%,the proportion of days with PM_2.5 as the primary pollutant increased from 23.8%to 31.7%.In the three years,PM₁₀,O₃,and PM_2.5accounted for more than 80%of the primary pollutants.The number of days that the environmental quality of Weinan City has reached the standard is basically on the rise,the number of days with severe pollution has decreased significantly,and the proportion of days with excellent air quality index categories has increased from 7.7%（2018）to 10.7%（2020）.From 2018 to 2020,the reduction effect of PM₁₀concentration in Weinan City is obvious,while the decrease of PM_2.5concentration is very small,and the management of PM_2.5should be paid attention to.The air quality in Weinan is mainly affected by the transmission of short and medium distance air masses.The air masses mainly come from central of Henan Province,north of Hubei Province and junction area of Baoji and Gansu Province.Affected by the southeasterly wind in summer,the air mass from the east and southeast accounted for 68.80%of the total;in winter,it was greatly affected by the air mass from the northwest,accounting for 58.79%.The distribution range of potential source areas and concentration contribution weights of PM_2.5 in Weinan are the widest in winter.South of Shaanxi,northeast of Sichuan,north of Hubei and central of Henan Province are the most widely in autumn and winter,as well as Xingtai,Handan,Jincheng,Yuncheng,Sanmenxia and Luoyang,and north of Hubei and central of Henan Province are the most widely in spring and summer,PM_2.5 has a larger potential contribution source area possibility and higher concentration contribution value.The non-carcinogenic risk value of PM_2.5 in Weinan City in the first and fourth quarters was relatively high,and the quarterly and annual risk values did not exceed the PM_2.5 risk value range specified by the US Environmental Protection Agency.The non-carcinogenic risks of Pb,Zn,Cu,and Mn four non-carcinogenic heavy metals in PM_2.5 in Weinan City to children are significantly greater than those of adults,;Cr,Ni the carcinogenic risk of the two carcinogenic heavy metals to the human body was higher than that for adults.The order of the non-carcinogenic risk values of the six heavy metals to the human body is:Mn>Pb>Cu>Zn>Cr>Ni,the non-carcinogenic risk value of Mn to humans is the largest,which is 0.4320.The carcinogenic risk value of Cr to the human body is greater than that of Ni,and the carcinogenic risk value of Cr to the human body is the largest,which is 1.550×10^-5.The non-carcinogenic and carcinogenic risk values of Mn,Pb,Cu,Zn,Cr,and Ni to the human body are all within the safety threshold specified by the health risk assessment model.