Pollution Characteristics And Health Risk Assessment Of Dioxin In The Soil Of A Typical Area Of The Pearl River Delta

Investigation on level and emission sources of dioxins as well as establishment of effective prevention measurement and legislation are hot global topics.At present,research on dioxin compounds in soil was not enough,especially for the distribution of dioxins in different types of soil.Therefore,study on pollution characteristics and risk assessment of dioxins in soils in typical region was significant.In this paper,the content of dioxin in the soils of a typical area of the Pearl River Delta was determined.And its distribution characteristics were analyzed.The soil/dust intake and skin exposure of residents in different regions were compared.And the environmental health risk of dioxin in sensitive population was evaluated.Possible sources of pollution were explored.The conclusions are as follows:?1?The concentration of dioxins in the soils of a typical area of the Pearl River Delta ranged from 63.36 to 54131.59 ng/kg.And the toxicity equivalent concentration ranged from0.39 to 122.19 ng I-TEQ/kg.According to German relevant soil risk assessment standards,24?41.38%?samples have no effect on human health.And the remaining 34?58.62%?samples should be protected in the use of land.Compared with some areas at home and abroad,the dioxins in the soils in typical area of the Pearl River Delta are at higher concentrations.The distribution of dioxins in the soils of the Pearl River Delta is greatly affected by the regional environment.The distribution of dioxins in the soil of the four regions is characterized by the industrial pollution areas>the urban-rural integration areas>the farmland forests and animal husbandry areas>the background areas.?2?The distribution of dioxin homologues in soil samples was mainly OCDD.Followed by HpCDD/Fs and OCDF.The distribution characteristics of homologues are that the percentage concentration increases with the number of chlorine substitution atoms except OCDF.The concentration distribution of toxic isomers of 17 kinds of dioxins was mainly OCDD.Followed by 1,2,3,4,6,7,8-HpCDD/Fs and OCDF.The toxic equivalent concentration distribution of toxic isomers of 17 kinds of dioxins was mainly OCDD.In addition,the percentage of dioxin of toxicity equivalent concentration in different soil types is quite different.?3?The daily average soil/dust intake of adult at each sampling site was1.14E-07³.57E-05 ng I-TEQ/kg·d.And the daily average soil/dust intake of children was1.30E-06⁴.06E-04 ng I-TEQ/kg·d.The skin exposure of adult was 2.39E-07⁷.49E-05 ng I-TEQ/kg·d.And the skin exposure of children was 2.08E-07⁶.52E-05 ng I-TEQ/kg·d.The environmental exposure of the four regions is characterized by the greatest risk environmental exposure of residents in industrially contaminated areas,especially children.?4?The risk degree?HR?of dioxin exposure is 8.83E-05¹.18E-01,which is less than 1.So the risk is low or negligible.The carcinogenic risk?CR?of dioxin exposure ranged from5.30E-08 to 7.07E-05.The CR of which the 48 sampling points were far less than 10^-6.And they were within an acceptable range.The CR of remaining 10 sampling points were between10^-6and 10^-4.There is no carcinogenic risk between them.?5?According to the theory of Wagrowski and Hites,the source of dioxin in the soil of a typical area of the Pearl River Delta is more complex.It is non-single source of emissions.And there are significant regional differences in the surrounding environment.It can also effect the level of dioxin pollution in the region.Generally speaking,The major emission's sources of dioxin in the soils of a typical area of the Pearl River Delta are automobile exhausting,herbicide using,and industrial pollution,etc.