Environmental Behavior Of Pahs In Atmosphere Around Chaohu Lake

With the rapid socio-economic development,and the accelerating urbanization and industrialization,the problem of environmental pollution has become increasingly prominent.The problem of atmospheric pollution has also drawn increasing attention.In recent years,the marked increase in haze weather has further illustrated the seriousness of atmospheric pollution.Chaohu Lake,one of China’s five largest freshwater lakes,has also received widespread attention about its surrounding environmental issues.This study collected atmospheric samples in the four seasons around Chaohu Lake through the traditional PUF-GFF sampling system and an eight-stage cascade impactor,including gaseous and particulate PAHs,and collected water from the four estuaries of Chaohu Lake.The overall level,seasonal variation characteristics,particle size distribution,and gas-partile distribution characteristics of PAHs in the atmosphere around Chaohu Lake were analyzed.The assessment of health hazards of respiratory exposure for PAHs in the atmosphere was calculated.The exchange fluxes of PAHs in air and water in summer was calculated.The main results as follows:(1)The concentration of total PAHs in gas phase around Chaohu Lake was 2.10 ~39.08 ng/m3,and the annual average concentration was 19.04 ± 12.57 ng/m3.The concentration of total PAHs in particle was 1.22 ~ 29.68 ng/m3,and the annual average concentration was 7.99 ± 7.81 ng/m3.The concentration of PAHs was highest in winter and the lowest in summer.There were obvious seasonal changes and the spatial difference was not.The concentration increased with decreasing temperature,which indicated that the concentration of PAHs in the area was mainly affected by the local air quality.(2)PAHs in the atmosphere around Chaohu Lake were mainly distributed in fine particles at all sampling sites,and were all above 60%.In four seasons,PAHs in winter accounted for about 74% in fine particles and was the largest.There was a significant correlation between the geometric mean particle diameter and the log-transferred subcooled liquid vapor pressures of PAHs in each season,and the correlation coefficients ranged from 0.60 to 0.88.(3)Log KP and log PL0 of PAHs in the atmosphere in four seasons around Chaohu Lake had a good correlation,and the slope(mr)was-0.306,-0.190,-0.261and-0.221.The gas-particle distribution of PAHs in the atmosphere in four seasons did not reachequilibrium,and the absorption mechanism was the main reason for the PAHs in the air attached to the particles.(4)The major source of PAHs in the atmosphere around Chaohu Lake area is from combustion,including the combustion of biomass and coal,and the combustion of petroleum,with little pollution from oil directly.(5)PAHs in gas phase and in coarse and fine particles have large different exposure risks to people in this region.PAHs in coarse particles have the lowest impact on human body,followed by that in gas phase,and PAHs in fine particles have the largest impact on human body.The people’s exposure to the respiratory hazard of PAHs in gas and particles of the atmosphere around Chaohu Lake are acceptable for and are similar to those caused by daily activities.(6)The residual levels of PAHs in dissolved and gaseous phase were measured in sμmmer in 2016,and by means of two-film model,the air-water exchange fluxes were calculated.The results shown that,PAHs in sμmmer around Chaohu Lake were mainly volatilization exchange across the air-water interface and all LMW PAHs were always exchanged from water into air with high fluxes,while part of HMW PAHs were from air to water with low fluxes and almost reached air-water balance.One reason was that the higher temperatures during the sampling period made semi-volatile PAHs diffuse from water to air easier.Another one was the concentration of PAHs in water was much higher than that in air and the great difference affected the magnitude and direction of PAHs exchange fluxes.