| As a typical persistent organic compound,polychlorinated biphenyls?PCBs?are semi-volatile,non-degradable,highly bioaccumulative,and highly toxic.PCBs have been widely distributed in biological and non-biological matrices around the world,especially in soils from electronic wastes dismantling area and sludge from wastewater treatment plants.At present,the farmland application of sludge has been widely used.However,PCBs can enter the farmland with the sludge application and then accumulate in the crops.Meanwhile,PCBs also can enlarge through the food chain,and then do harm to the ecological safety and the health of species at high trophic.It is of great significance to understand the pollution characteristics of PCBs in these typical media,the uptake and translocation of PCBs in sludge-applied soil,the control and governmence of PCBs pollution,and the formulation of relevant environmental legislations.This paper studies the distribution characteristics of PCBs in different contaminated soils and sewage sludge,and their migration and transformation in sludge-applied soil-plant systems,and the following results have been obtained:?1?We can understand the different types of pollution in the soil through studying the distribution of PCBs in soils in typical contaminated areas such as Jiangcungou landfill site,an enterprise in the Shaanxi Provincial Resource Recycling Industry Park,and the garbage compression station in Chang'an District and the small garbage collection point near Northwestern University.There were 36 kinds of PCBs were detected at all sampling sites,and their contents ranged from 4.26 to 57.77 ng·g-1with an average of 15.31 ng·g-1.Among this PCBs,trichlorobiphenyl and tetrachlorobiphenyl were occupied the main components.The spatial distribution trends of PCBs showed that:the Jiangcungou landfill(avg 20.78ng·g-1)>a company in Shaanxi Province's resource recycling industry park(avg 18.95ng·g-1)>the garbage site near Chang'an District(avg 16.36 ng·g-1).?2?We can understand the pollution characteristics of the sewage sludge in different areas of Shaanxi Province through studying the distribution characteristics of PCBs in sludge from different sewage treatment plants in Shaanxi Province.The content of PCBs in the sludge from the 23 different sewage treatment plants in Shaanxi Province ranged from 9.64 to 213.85 ng·g-1with an average of 49.11 ng·g-1.Among PCBs,trichlorobiphenyl and tetrachlorobiphenyl were the main components.The content of PCBs in the sludge is related to the amount of treated water in the wastewater treatment plant,the type of sewage,and the use technology,and the overall trend presents as:Guanzhong Region>North Shaanxi Province>Southern Shaanxi Province.The main components of different PCBs homologs in the sludge were analyzed,and we can obtain two main components,one is from domestic transformer oil and the other is from the reaction of low-chlorinated biphenyls in air or imported products.?3?The absorption and transport of the plants after application of sludge with a high PCBs content to the soil were studied.The rules of absorption and migration of PCBs in the soil in sludge application were studied though using the greenhouse pot experiments,including setting different types of plants,different types of sludge and its application rates.The study found that sludge application increased the concentration of PCBs in soil and plants,with the percentage of low-brominated PCBs increased sequentially in soil,plant subterranean,and above-ground parts of plants.The Root Concentration Factor?RCF?of wheat to PCBs is greater than that of maize.However,the transport factor?TFs?of each homologue?except heptachlorobiphenyl?is smaller than that of maize.And there is a negative connection between their root enrichment factor of different unites and corresponding Kow?octanol-water partition?.With the increase of sludge application,the RCF value gradually decreases,and the TFs value showed a decrease in 1-3 chlorinated of PCBs,while the trend of tetrachlorinated and above of PCBs were increasing.The sludge application with the lowest organic matter content has the highest RCF value of the plant. |
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