The Pollution Characteristics And Environmental Risk Assessments Of Heavy Metals In Atmospheric Particulates Of Different Sizes In Nanjing City

Atmospheric particulates have different particle size distributions and a wide range of sources.The harmful heavy metal elements are not degradable and show different bioavailability.They are easy to accumulate in organisms and have a huge impact on the ecological environment and human health.In order to explore the pollution characteristics and environmental risks of heavy metals in atmospheric particles with different particle sizes,this paper takes 4 different urban functional areas in Nanjing as the study area,and analyzes long-term sampling of atmospheric particles with different particle sizes(PM_2.5,PM₁₀,TSP)and their Heavy metal concentration distribution,temporal and spatial changes,source analysis,and corresponding pollution characteristics such as chemical form,bioavailability,human health risk and ecological risk.The main results are as follows:?1?In 2016,the concentration of PM₁₀ in Nanjing was higher than that of PM_2.5.The concentration of PM_2.5 and PM₁₀ showed obvious spatial and temporal distribution characteristics.The spatial change was industrial area>urban area>suburban area>rural area,and the seasonal change was winter>spring>autumn>summer.Affected by meteorological factors,the increase in temperature,the decrease in air pressure,and the wind speed are not conducive to the formation of PM_2.5.Rainfall has a good effect on removing PM_2.5.?2?There are typical seasonal distribution characteristics of heavy metal concentrations in PM_2.5 and PM₁₀ in Nanjing,and there is no clear uniform spatial distribution rule for each element between the study areas.Combining several source analysis methods,sources of heavy metals in PM_2.5 in Nanjing include metallurgy and chemical industry,automobile exhaust,coal combustion,and soil dust.?3?Cd in PM_2.5 has a high bioavailability and poses a great threat to human health.Based on the total amount of elements,Cd and Co have carcinogenic risks in industrial areas and urban areas,and their atmospheric emissions should be strictly controlled;it is more reasonable to evaluate the human health risks of atmospheric heavy metals based on the effective state concentration.?4?The chemical properties of Cd and Pb in TSP are lively,with strong bioavailability,and great impact on the ecological environment.The average pollution risk degree of industrial areas and urban areas is at a very strong ecological hazard level.Although heavy metals are trace components in atmospheric particles,their distribution is not always consistent with the overall atmospheric particles.Therefore,these key factors should be considered for both environmental risk assessment and air quality indicators for air pollution control.Health is recommended to reduce outdoor activities in industrial and transportation areas,especially in spring and winter.In future research,a more detailed and accurate source analysis of environmental aerosols and related heavy metals is required.