Water-particle Partition And Long-distance Transport Characteristics Of Heavy Metals In Atmospheric Environment During Heating Period In Shanghai And Jinan Of China

As the study on air pollution develops in depth,it was discovered that the research on the mechanism of pollutants could explain the formation process of air pollutants and evaluate the health risk to human body more accurately.Particularly,heavy metal components,which account for a small proportion in atmosphere environment and had low concentration of cumulative carcinogenicity in their biologically available parts,were harmful to human health.When discussing the gas reaction and gas-particle partitioning process of heavy metals,adding the simulation reaction to the liquid phase can precisely calculate the concentrations of biologically available heavy metals in the atmospheric environment.The physical and chemical reaction process of heavy metals in the environment could be understood more clearly.Therefore,we could understand the pollution characteristics and risk assessment of heavy metals in the atmosphere more comprehensively.Based on the collection of pollutants from different media in the atmospheric environment,this study analyzes and explores the water-particle distribution characteristics,source apportionment and health risks of heavy metals in the atmosphere via a variety of scientific analysis methods and simulation studies.This study with the support of the National Natural Science Foundation of China（41877476）project aqueous reaction process and influence mechanism of heavy metals in PM_2.5 during urban haze-fog episodes,selected Minhang in Shanghai and Shizhong in Jinan area.In the winter haze,with atmospheric particle phase and water phase in the four kinds of heavy metal Hg,As,Cd,Pb,as the main object of study,analysis of the concentration changes,combined forms,partition coefficients,water-particle partition and grain characteristics of heavy metals,the backward trajectory simulation analysis method was used to distinguish the contribution of the heating area to the atmospheric particulate matter pollution in the non-heating area.PCA,PMF and other receptor model method,further determine the source of pollutants;Finally,respiratory exposure and skin contact models were used to analyze the exposure risk of metals in the atmosphere.The specific research results of research significance are as follows:（1）The concentrations of heavy metals in the atmospheric environment of Shanghai and Jinan were lower than the secondary daily average limit.The concentrations of Pb,As,Cd and Hg in atmospheric water in Shanghai area were 6.37±3.58 ng/m³,4.37±1.68 ng/m³,0.49±0.37ng/m³ and 0.22±0.14ng/m³,respectively.The concentrations of Pb,As,Cd and Hg in PM_2.5 were 26.4±22.03ng/m³,2.98±1.42ng/m³,1.18±1.09ng/m³ and 0.06±0.04ng/m³,respectively.In Jinan area,the order of heavy metal content in PM_2.5 was still 39.66±25.57ng/m³,2.89±1.69 ng/m³,1.38±1.21 ng/m³,0.13±0.12 ng/m³ for Pb,As,Cd and Hg,respectively.The concentrations of Pb,As,Hg and Cd in atmospheric water were 5.16±4.14ng/m³,2.07±1.29ng/m³,0.24±0.13ng/m³and 0.22±0.21ng/m³,respectively.Due to the high solubility of Hg,the concentration of As in atmospheric water was higher than that in particulate matter,which was affected by the release form of pollution.In addition,under the background of haze period,the change of Cd in the aqueous phase presents a certain lag.（2）The partition coefficients could distinguish the distribution of heavy metals in atmospheric water and PM_2.5.The partition coefficient of different heavy metals in Shanghai and Jinan showed the same change rule.Under the influence of the chemical characteristics of heavy metals,the distribution coefficient from large to small was Pb<Cd<As<Hg.The emission concentrations of particulate matter affect the adsorption capacity of particulate matter to heavy metals.The higher the concentration,the stronger the adsorption capacity.Its adsorption capacity was negatively correlated with temperature and positively correlated with p H value.Hg was strongly affected by temperature and humidity in the non-haze period,and dominated the transformation direction and content distribution of Hg.When the temperature increases,the heavy metal compounds showed the characteristics of heat treatment reversibility,which reduces the adsorption of heavy metals by particles.With the increase of the p H value of the particle phase,the adsorption capacity of the metal material became stronger,which was conducive to the formation of colloids or complexes of heavy metals and inhibits their conversion capacity.Through ion exchange,chemisorption and complexation,inorganic metal ions inhibit the migration activity of heavy metals and affect the change of their occurrence forms.（3）The concentrations of As and Pb in the heating area were significantly different from those in the non-heating cities,and the concentrations of Pb and As gradually decrease from northwest to southeast,and the concentrations of heavy metals in the Bohai Rim area were small and high.It was proved that industrial activities and coal-burning heating activities not only affect the quality of atmospheric environment in the heating area,but also affect the non-heating area under the action of airflow.Therefore,there was a strong spatial correlation of air quality between geographically adjacent cities.Cd and Hg are mainly affected by different pollution sources,the north-south variation rule was not obvious.The winter airflow in Shanghai area mainly came from the Shandong-Hebei-Inner Mongolia route.The Jinan area was mainly affected by the airflow from the south of Hebei to the north of Shanxi to Inner Mongolia.Through the simulation analysis of air flow between Shanghai and Zhejiang,it was concluded that the pollutants were concentrated in the east coast of Shanghai due to the obstruction of Marine air mass and the contribution of Jiangsu and Zhejiang.The contribution of Pb and As in Jinan area was mainly dominated by local emissions,and the contribution was higher in Beijing-Tianjin-Hebei area.Due to the obstruction of the southwest air mass,the inland northwest air mass carrying a lot of pollutants stays,causing serious air pollution.（4）Principal component analysis and positive definite factor matrix were used to analyze pollution sources.It was found that PM_2.5 pollution was strongly affected by long-distance transportation and atmospheric water stayed in the environment for a short time.Therefore,the pollution sources of atmospheric water were mainly local pollution discharge or gas-particle conversion.Industrial activity was the main source of PM_2.5 pollution in the two regions,and the contribution of industrial pollution was higher in Jinan,which was also contributed by the Beijing-Tianjin-Hebei region.Coal burning was the second most important source of pollution after industrial activity.In atmospheric water,the contribution of pollution sources in the two regions was different.Coal-fired heating activity was the main pollution source in Jinan,accounting for36.17%,and the contribution of Na and As increased significantly.The contribution of traffic sources in Shanghai has increased,and natural sources had become an important source of pollution.（5）In Shanghai and Jinan,the non-carcinogenic risk values under the two approaches were all lower than 1,but the risk values in children were all higher than that in adults.The risk values of respiratory exposure pathway and skin infiltration pathway were different to some extent.The non-carcinogenic risk of respiratory pathway to children was Pb>As>Hg>Cd.Under the skin infiltration pathway,in turn As>Cd>Pb>Hg,especially in Jinan,children had a certain carcinogenic risk of As,the emission of As should be focused on.