Pollution Assessment And Source Apportionment Of Soil Heavy Metals In Soil Of Tumen River Basin

With the acceleration of urbanization,the soil has been damaged by heavy metal pollution such as "three wastes" of industry,automobile exhaust emissions,coal combustion,exploitation of mineral resources,excessive use of chemical fertilizers and pesticides,etc.As the border area of China,Russia and Korea,Tumen River Basin has a special geographical location and complex environment,and its ecological environment has aroused extensive attention.Research on soil heavy metals in Tumen River Basin and determination of soil heavy metal pollution sources are of great significance for effective control of heavy metal pollution.In this study,the concentrations of heavy metals in surface soil samples in the middle and lower reaches of the Tumen River basin were investigated using Inductively Coupled Plasma Mass Spectrometry(ICP-MS),and the pollution characteristics,ecological risks and health risks were discussed.Correlation analysis and principal component analysis were used to identify the sources of soil heavy metals.PMF model was used to identify the pollution sources and judge the contribution of the sources.The contents of vanadium(V),chromium(Cr),manganese(Mn),cobalt(Co),nickel(Ni),copper(Cu),zinc(Zn),arsenic(As),molybdenum(Mo),cadmium(Cd),antimony(Sb),barium(Ba),thallium(Tl)and lead(Pb)in surface soil samples from the middle and lower Reaches of the Tumen River basin.The average concentrations were 62.16,55.33,715.61,9.55,20.39,23.59,77.84,44.99,1.38,0.32,0.95,418.72,0.11,45.88 mg/kg,respectively.Among them,Cr,Mn,Cu,Zn,As,Mo,Cd and Pb exceeded the soil background value,especially the average content of As and Cd exceeded 5.37 and 2.93 times of the soil environmental background value.Compared with the screening values in the Risk Control Standard for Soil Environmental Quality and Soil Pollution in Agricultural Land(GB15618-2018),the exceedance rates of As and Cd were 39.58% and 14.58%,respectively.In the study area,the pollution level of As is the most serious,followed by Cd,and the pollution scope of As is extensive,while Cd has local pollution.When the soil background value was taken as the reference value,the pollution load index of the whole study area was 0.94,which was at the level of no pollution.The average of Nemerow’s composite pollution index was4.89 that belongs to heavy pollution level.When the soil environmental quality standard was taken as the reference value,the pollution load index of the priority control heavy metals in the study area was 0.41,which belongs to the level of no pollution.The average of Nemerow’s composite pollution index was 1.29,which is considered as light pollution.The spatial distribution of heavy metals in soil showed that the concentrations of Cu,Zn,As,Cd,Pb,Mn,Mo and Sb were high near Tianbao Mountain.According to source identification,heavy metals in soil of Tumen River Basin are mainly affected by four pollution sources,which are Cu,Zn,Cd and Pb,Ni and Cr,Mo and Ba and Tl.PMF model source analysis shows that the contribution of mining activities and traffic sources,mining,mixed sources and natural sources are 30,24,27 and 19%,respectively.The results of source identification are in good agreement with those of PMF model analysis.The ecological risk assessment showed that the potential ecological risk index(RI)of heavy metals in soil of Tumen River Basin was 3.64-474.73,with an average value of 50.39,which was a slight ecological risk.The samples with moderate ecological risk accounted for 2.08%,those with strong ecological risk accounted for8.33%,and those with extremely strong ecological risk accounted for 4.17%.The single element potential ecological risk index of Cd and As was relatively high,which further affected the comprehensive ecological risk index.Therefore,appropriate protection measures should be taken when necessary.The samples with slight ecological risk accounted for 85.42%.The evaluation results showed that the overall ecological risk was low in the study area,and the local ecological risk was serious.Health risk assessment showed that heavy metals in soil in the study area were mainly harmful to human health through hand-oral ingestion,of which As had the greatest impact.In addition,children were at higher risk than adults.For children,the non-carcinogenic risk of hand-oral ingestion is greater than 1,indicating a non-carcinogenic risk and potentially adverse effects on local children.The results of uncertainty analysis showed that 19.00% and 55.69% of children were affected by the non-carcinogenic risk of Mn and As,and Mn had a non-carcinogenic risk for a small part of the target population in the adult study area.Therefore,reasonable measures should be taken to prevent the non-carcinogenic effects of As and Mn on local children.The results of carcinogenic risk assessment showed that among the six elements,the exposure risk of As was the highest,and hand-oral ingestion > skin contact > respiratory inhalation.Among the three exposure pathways,hand-oral ingestion was the most critical,which may be related to people’s living habits and ways.Overall,human exposure to heavy metals in the soil of the study area was at a safe level.The uncertainty assessment showed that about 50.33% of the population would be affected by the acceptable risk of cancer caused by As.The results of this study can provide data support for effective control of regional heavy metal pollution and theoretical basis for urban construction and human health protection in the future.It provides scientific basis for rational utilization,development and protection of regional land.