| Heavy metals are toxicity,durability and bioaccumulative,which can enter the human body through the atmosphere,dust and so on,causing immeasurable harm to the human body.Surface soil and indoor dust are the main reservoirs of heavy metals in the environment,and they play an important role in heavy metal pollution because they can be ingested into the human body in many ways.Up to date,most current research of heavy metals in the soil and dust have mainly concentrated in mining area,farmland and road,but less research has done on the soil and indoor dust of the residential areas in the common environment.In order to investigate general environment of heavy metal pollution and risk of the residential faced,10 heavy metals including As,Cd,Co,Cr,Cu,Mn,Ni,Pb,V and Zn in the surface soil and indoor dust of both urban and rural areas of Taiyuan city were studied.Based on the analysis of heavy metal content from the collected samples of 72 samples in 2018heating season,and 72 samples in 2019 non heating season,by using multivariate statistics,receptor model and risk assessment model,we made an evaluation of the pollution degree,pollution source and potential risk of heavy metals in the urban and rural soil and indoor dust.The purposes of the research were to provide data support for the regional pollution control and prevention policies making of Shanxi Province,and also to provide reference for the research work of multi-media pollution prevention and control and environmental health impact assessment.The main results were as follows.?1?The average values of As,Cd,Cr,Cu,Ni,Pb and Zn in the indoor dust were 16.21±5.53,0.67±0.40,130.89±127.87,71.79±58.37,40.72±27.56,66.00±54.08 and 357.36±365.26 mg/kg,respectively,which were higher than the background values of the soil in Shanxi Province,especially for the content of Pb and Zn it was 4.49 and 5.63 times higher than their background values,respectively.The coefficients of variation of Cr and Zn were 97.69%and 102.21%,respectively,which are highly dispersed and greatly influenced by human beings.Among the 10 heavy metal elements,Cd has the largest geoaccumulation index,and it was in moderate pollution.The enrichment coefficients of Cu,Pb,Zn and Cd were all greater than 5,showing significant accumulation,indicating that it is greatly influenced by human activities.The mean values of As,Cd and Pb in the soil were 11.46±1.54,0.13±0.05and 20.95±3.27 mg/kg,respectively,and the value was slightly higher than that of their background value in Shanxi Province.This indicated that there may be a slight accumulation of these elements.The variation coefficient of the 10 heavy metal elements is all less than 40%,and the in-situ accumulation index of each element is less than 1,which belongs to the pollution-free state.The enrichment coefficient was less than 2,except for Pb,indicating that the heavy metals in the soil are less disturbed by human factors and mainly come from the soil parent material.?2?The results from correlation analysis,principal component analysis and cluster analysis showed that 10 sources of heavy metals in indoor dust can be divided into four categories:V,Co and Mn;Ni,Cu and Cr;Cd,Zn and Pb;CR.On the source of the heavy metal,As have similar sources with V,Co and Mn;and Ni,Cu with Cr.Among them,V,Co and Mn are considered to be from natural sources;Ni,Cu and Cr are mainly affected by living sources;Cd,Zn and Pb are mainly affected by industrial and traffic pollution;and As is mainly affected by both natural and living sources.?3?Among the 10 heavy metal elements in the indoor dust,Cd has a strong hazard level and the largest contribution to the potential ecological risk,and it accounts for 71.34%of the overall contribution rate.The other nine elements have a slight hazard level.The all potential ecological risk index?RI?of the 10heavy metal elements in the soil was less than 40,the potential ecological hazard index RI was 18.48,and the IR was less than 150,indicating that the soil in Taiyuan area was in a relatively clean state.Just as dust accumulation,Cd is the largest contributor to potential ecological risks,accounting for 73.56%of the total contribution.The results of indoor dust and soil heavy metal health risk showed that the daily average exposure of non-carcinogenic health risk was in the order of the handle-mouth way>through skin exposure quantity>through breathing exposure,and among the three ways the way from the hand and mouth accounted for more than 90%of the total daily average exposure.The risk of cancer HQ and total non-carcinogenic risk of HI through various ways are less than 1,and there is no non carcinogenic risk at present.The carcinogenic risk thresholds of the four carcinogenic elements As,Cd,Co and Cr are all less than10-6,and there is no-carcinogenic risk.Therefore,it is concluded that there is no potential safety hazard in the outdoor soil of residential areas in Taiyuan city,and some elements in the indoor dust have potential ecological risks. |
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