Assessment Of Heavy Metal Pollution And Human Health Risk In Soils And Crops Around The Ni-Mo Polymetallic Mining Area In Songlin, Zunyi, Guizhou

In order to understand the contamination degree of heavy metals in the soils around the Ni-Mo polymetallic mining area in Songlin,Zunyi,China and human health risk level of these elements ingested by surrounding residents through crops planted on the soils,the concentrations of Cu,Zn,Ni,Mo and V in the samples includingupland,paddy soil,forest soil,grain and vegetable crops collected from the Ni-Mo polymetallic mining area were analyzed using Inductively Coupled Plasma Mass Spectrometry?ICP-MS?.The Nemero pollution index?NPI?and health risk assessment model recommended by US EPA was used to evaluate the pollution status of heavy metals in the soil and the human health risk level of the residents of the mining area,respectively.Through the evaluation,we discussed preliminarily the migration process of heavy metals fromblack shale to soil in the mining area.The main conclusions of this study are as follows.?1?The average concentrations of Cu,Zn,Ni,Mo and V in upland in the Xiaozhushui ore point are 64.3,251,254,78.3 and 500 mg·kg^-1,in paddy soil are 55.0,236,209,10.7 and 314 mg·kg^-1,and in forest soil are 59.8,207,80.5,35.0 and 462 mg·kg^-1,respectively.For the Tuanshanbao ore pointare,the average contents of Cu,Zn,Ni,Mo and V in theupland soils are 55.3,215,133 and 2 mg·kg^-1 and in the paddy soilsare 57.7,234,164,14.8 and 277 mg·kg^-1,respectively.The averaged concentrations of Cu,Zn,Ni,Mo and V in the soils are significantly higher than the corresponding background values of these elements in the soil of Guizhou Province.In addition,the contents of Cu,Zn,and Ni in the soils are higher than the corresponding risk control standards for the agricultural land of China,indicated there is heavy metal enrichment in this Ni-Mo polymetallic mining area.?2?Heavy metals contents in grain and vegetable crops in in this Ni-Mo polymetallic mining area exceed their corresponding food limit standards.Among the studied heavy metals in the crops,the average contents of Ni and Mo in rice are 2.85 and 2.57mg·kg^-1,which are 6.5and 3.6 times of their corresponding food limit standards respectively.The average contents of Mo in maize are 0.980 mg·kg^-1,which are 1.4times of the standard limit.The average contents of Ni in sweet potato are 18.0 mg·kg^-1,which is 45 times of the standard limit.For the vegetable crops,Zn,Ni and Mo in Chinese cabbage,Zn,Ni and Mo in pepper,and Cu,Zn and Ni in radish exceed their corresponding food limit standards.?3?The calculated Nemerow pollution index?NPI?indicate that the soils in this Ni-Mo polymetallic mining area are polluted by Cu,Zn,Ni,Mo and V.Among the heavy metals,the contamination degree of Mo are the most serious,Ni and V are the second,while Cu and Zn are relatively light.The average value of Nemero pollution index?NPI?of six heavy metals in upland soils,paddy soils and forest soilsare 19.9,4.8and 10.9,and the corresponding pollution degree are high,moderate and high levels,respectively.?4?The health risk assessment results suggest that the total hazard quotient?THQ?values of Cu,Zn,Ni,Mo and V absorbed into human body through six crops are 0.626,0.707,0.132,3.619 and 25.143,respectively,which suggests that the health risk of heavy metals to human would be caused by long-term regular consumption of these crops.The hazard quotient?HQ?values of rice,maize,sweet potato,Chinese cabbage,pepper and radish are 15.209,1.540,1.515,8.430,0.319 and 3.213,respectively.Except pepper,all the other crops have a certain degree of health risk.Consuming crops and Chinese cabbage ismajor exposure pathway of the five heavy metals to the residents.Mo and V in rice and Chinese cabbage are major risk sources and pollutants.?5?The characteristics of heavy metals enrichment in black shale and Ni-Mo polymetallic ore,the difference heavy metals contentsin various medium and the correlation of heavy metals in the soils were investigated.The results show that the black shale and Ni-Mo polymetallic ore in the mining area are enriched with heavy metals,accordingly,the soilswere also enriched with corresponding elements,and there is a significant correlation between theseheavy metals.The transfer of heavy metals from the black shale?or Ni-Mo ores?to the soils has occurred in the Ni-Mo polymetallic mining area.The results of this study show that the soils in the Ni-Mo polymetallic mining area in Songlin,Zunyi,China has enriched with multiple heavy metals,which causedserious heavy metal pollution in upland,paddy soils and forest soils.Meanwhile,there is a certain degree of human health risk for local residents via long-term regular consumption ofcropsplanted on the soils.