| Indoor dust is one of the important carriers for enrichment of heavy metals,and the sources of heavy metals in indoor dust are more complicated than other environmental media.Due to the limited indoor space,the pollution level of heavy metals in dust also poses a more threat to human health.Non-ferrous metal smelting is one of the important sources of heavy metal emissions.There are many non-ferrous metal smelters in China,which cause serious heavy metal pollution to the surrounding environment and endanger the health of people in surrounding area.Among them,indoor dust intake is one of the main ways for people to expose heavy metals.Daye City is one of the five major copper raw material production bases in China.The large-scale copper smelting activities in the local area have caused serious heavy metal pollution to the surrounding environment and have shown initial human health damage effects.In order to research the pollution characteristics and the health risks to human body of heavy metals in indoor dust from Daye nonferrous metals smelting area,35 indoor dust samples were collected in surrounding the smelting factory of Daye.Using multivariate statistical methods and geostatistical methods,the pollution characteristics,spatial structure and distribution characteristics of heavy metals?Hg,As,Pb,Zn,Cu,Cr,Cd,Ni,Tl and Mn?in indoor dust were systematically analyzed.The sources of indoor dust heavy metals were quantitative analysis by PMF model.According to the questionnaire,influence factor analysis was carried out.The exposure risk and health risk of heavy metals in indoor dust were evaluated based on the health risk assessment model from US EPA.Through the analysis of heavy metals,the following conclusions can be obtained:?1?The contents of heavy metals Hg,As,Pb,Zn,Cu,Cr,Cd,Ni,Tl and Mn in indoor dust from the nonferrous smelting area of Daye have different degrees of accumulation,and the average content are 12.39,11.72,10.74,6.75,32.51,2.37,89.69,2.38,2.04,and 1.07 times than the soil background value of Hubei Province,respectively.The accumulation of Cd and Cu is the highest,which indicates Cd and Cu in indoor dust may be affected by human activities in the study area.As,Pb,Zn,Cu,Cd,Ni,and Tl contents in indoor dust from the smelting area are significantly higher than other functional areas,indicating that smelting activities have a certain degree of influence on these elements.There are no significant differences in Mn,Hg and Cr between different functional areas,which indicates that different human activities have less influence to these three elements.?2?Based on the results of Geo-accumulation Index,the pollution level of heavy metals in indoor dust follows a descending order as Cd>Cu>Pb>As>Hg>Zn>Cr>Ni>Tl>Mn,in which Cd is extremely polluted,Cu is strongly to extremely polluted,Hg,As and Pb are moderately polluted,Ni and Tl are mildly polluted,and Mn is typically unpolluted.There are significant differences for the accumulation index levels of heavy metals in different functional areas,different indoor environments,and different distance to the smelter factory.The elements Ni,Cu,Zn,Cd,As,Pb and Tl are significantly higher in the smelting area than in other functional areas,which may be related to pollutant emissions from non-ferrous smelters factory.Element Zn has the highest level of pollution in industrial areas,and elements Hg and Cr have the highest levels of pollution in commercial areas.The pollution levels of elements Mn,Ni,Cr and Tl in all functional area are low.Elements Cu,Zn,Tl,Hg and Cd in indoor dust have the highest pollution level in cultural and educational environment;the pollution levels of elements Pb,Ni and As are the highest in offices;and elements Mn and Cr have the highest pollution level in the family houses.The farther the indoor dust samples from the non-ferrous smelting factory,the lower the pollution level of heavy metals.The spatial distribution characteristics of the pollution load index PLI value confirmed that the spatial distribution of heavy metal pollution in indoor dust is consistent with the prevailing wind direction,and the farther away the samples from the smelter factory,the lower the pollution level of the sample.?3?Elements Mn,Tl and Cr of indoor dust have strong spatial autocorrelation,and elements Hg,As,Cu,Zn,Pb,Ni and Cd are moderately variable.There are similar distribution patterns for the contents of Cu,Pb,Zn,Cd,As,Tl and Ni in Daye nonferrous smelting area.The highest values are distributed near the smelting factory,and the contents of these elements slowly decrease toward the southeast-northwest direction,which is consistent with prevailing wind direction.Mn has the highest value in the vicinity of the garbage station,and the distribution in other areas is relatively flat.The highest value of Hg content appears in the southwestern part of the study area,and the Hg content is relatively low in the northwest and northeast,respectively.The high value area of the element Cr appears near the steel mill,and other areas are more evenly distributed.?4?Heavy metals of indoor dust in Daye nonferrous smelting area are mainly come from three sources,which are industrial activities related to smelting and traffic emission,industrial activities based on coal combustion,and natural source.Cu,Zn,Cd,As and Pb may be mainly affected by industrial activities related to smelting and traffic emission;Mn and Cr may be mainly affected by natural sources;Hg may be derived from industrial activities based on coal combustion;Ni and Tl may be mixed sources,one is a natural source,and the other is an industrial source dominated by smelting activities.Human activities are the predominant influencing factors of heavy metal contents in indoor dust from Daye nonferrous smelting area,and occupied 68.71%of total contributions.In addition,heavy metals of indoor dust are affected by factors such as the age of the house,the distance from the road,the indoor coal burning situation and the frequency of window opening.The longer time the house is built or renovated,the higher the content of heavy metals in the house;households near the street have higher heavy metal contents than households far from the street;coal combustion and smoking in indoor will cause the accumulation of heavy metals in the room;the longer time of window is opened,the easier it is for heavy metals to accumulate;the more people there are in indoor,the more likely it is to accumulate heavy metals in dust.?5?In the indoor dust of Daye nonferrous metals smelting area,except for Hg with steam inhalation as the main exposure route,the main exposure routes of other heavy metals are hand-mouth intake.Children exposed more heavy metals than adults,and the element for the highest exposure dose was Cu.The elements As and Cr in the indoor dust of Daye nonferrous metals smelting area have certain non-carcinogenic risks for children,and the HI values of As and Cr are 4.11 and 1.71,respectively,which both exceeding the safety threshold.Other elements have no non-carcinogenic.The non-carcinogenic risk factors of adults are within the safety threshold.The carcinogenic risks value of four heavy metals?Cr,As,Ni and Cd?in the indoor dust below safe limit of 10-4,indicating there is no carcinogenic risk.The results of this study will help to deepen the understanding of the pollution characteristics of heavy metals in indoor dust and the health risks of population exposure under high-intensity human activities about non-ferrous smelting,and provide a scientific basis for the prevention and control of heavy metal pollution and population health protection in this area.Meanwhile,results of this study can provide a reference for the environmental protection of other non-ferrous smelting areas in China. |
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