The Temporal And Spatial Distribution And Residual Characteristic Of PAHs Over Multi Media Environment In WWTPs

PAHs are widely distributed in the environment and there are more than 40 kinds of PAHs and its derivatives have a carcinogenic effect.The research of PAHs in influent(2009-2016),effluent(2009-206),sludge(2011-2016)and air(2012-2014)was conducted in this study.73 sludge samples which covered most of the provinces in China were collected in the winter of 2015 and summer of 2016 in order to study the temporal and spatial distribution characteristics and emission factors of PAHs in WWTPs,China.The concentration of PAHs were increased earily but decreased latter in wastewater and sludge which was in consistent with the consume of raw coal in Harbin.The concentration of PAHs in summer and winter were higher than that in autumn and spring in influent,effluent,sludge and air.Rainfall may be the main reason of higher contamination in summer.The coal fired central heating and indoor dust in winter may be reasons of higher PAHs in WWTPs.The mean removal efficiency of total PAHs was about 85%.There was about 3 600-4 900 g/d of PAHs imported into the WWTP,300-1 000 g/d discharged into Songhua River through effluent,140-1 200 g/d absorbed onto sludge and the rest was degraded or volatilized into the air.The concentration of PAHs in Harbin and Yunnan were at a high level both in winter and summer while it was at a low level in Guangdong,Fujian,southern Anhui and southern Hebei.The level of PAHs in Changchun and Gansu varied greatly in winter and summer.The spatial distribution of sludge in China decreased with the increase of longitude but increased with the increase of latitude.The coal fired central heating was the main reason of higher PAHs in sludge.In addition,the different structure of industrial have little impact on the proportion of different rings of PAHs.The PAHs level of TEQ was higher when the concentration of PAHs was higher and there was no sample exceeded the limit value of PAHs for agriculture in China.The sources of PAHs in China were different.In general,vehicle exhaust were the main source of PAHs in Northeast,East,Southwest and Northwest and North while the coal combustion was the main source of PAHs in Mid-South.Gas combustion is the main source of PAHs in East.Domestic heating,heavy industry,high automobile ownership,large population density and higher level of economic development may contribute more PAHs into WWTPs.In general,the temproal and spatial distribution was the combined effects of total factors.