| When the accumulation of the heavy metal goes up to a certain amount,it will make the soil pollution of heavy metal.When the amount of heavy metal in the vegetables goes up to a certain amount,it may affect the growth of vegetable, furthermore the heavy metal will go though the food chain into human body and make affect to people health.The soil pollution of heavy metal has been one of the global problem of people attention.The quality safety of the agricultural produce causes anxiety.In this thesis,the present situation of heavy metal(Cu,Pb,Mn,Zn,Cd,Cr,Ni)pollution of vegetable garden soil and vegetables in Zhengzhou city suburbs was investigated and evaluated.The relation between heavy metal content in vegetables and that in soil was also discussed.The results were showed as follow:1.The pH value of the surface soil the study area is from 5.80 to 6.02,which belonges to the slightly acid soil,the organic matter content ranges from 6.77 to 17.62 mg·kg-1,the average is 12.71 mg·kg-1,which is in the lower-stage.The P content ranges from 3.65to 52.74 mg·kg-1,the average is 30.76 mg·kg-1;has a higher content.2.The heavy metal content of the surface soil in the study area show as follows: Cu19.12mg·kg-1,Mn544.5 mg·kg-1,Zn51.70 mg·kg-1,Ni27.74 mg·kg-1g,Cr57.99 mg·kg-1,Pb18.50 mg·kg-1,Cd0.156 mg·kg-1.Among which the content of Cd is 2.44 times than the environment background value of the Henan Province,that proves the heavey metal pollution has happened in this area.The order of the heavy metal pollution in the vegetable plot of the plouth horizon is Cd＞Ni＞Mn＞Cu＞Cr＞Pb＞Zn. The One-factor Pollution Index is 2.44,1.02,0.97,0.96,0.92,0.85 and 0.83 respectively.The Comprehensive Pollution Index is 1.9,which belonges to light pollution.3.There usually has accumulation in surface or Subgroups accumulation in surface in the profile of the heavy metal element of the soil.As a whole the surface is higher than the middle-level,and the middle-level is higher than the lower level.The heavey metal will accumulate as the length of planting.Correlation analysis indicated that there were significantly positive correlations between Ni and Cu,Cu and Pb,Ni and Pb,Mn and Ni.Therefore,it can be assumed that Ni,Cu,Pb maybe come from the same source.4.The order of the vegetables heavy metal content is Materconvnlvulus＞Amaranth＞Caraway＞Leaflettuce＞Ciboulette＞Towel qourd＞Auberqine＞Corn.The heavy metal content of leafy vegetables was higher than other vegetalbles obviously. According to the indexes of single contaminants Pollution the result showed:The content of Pb was significantly higher than Cd which is easier bioconcentration.Some vegetables have high levels of Pb.5.Health risk assessment of heavy metals in soils results show that:the order of the human intake of heavy metals in three ways was as follows:direct intake＞intake absorbed through the skin＞respiratory intake;from the body's absorption of view, intake of heavy metals in order of Mn＞Cr＞Zn＞Ni＞Cu＞Pb＞Cd.From the point of carcinogenic risk view,the heavy metals for children and adults are carcinogenic risk factor does not exceed the standard 10-6,in the acceptable range.6.According to the heavy metal exposure on human health of exposure to the risk evaluation method,the order of THQ is Pb＞Cd＞Cu＞Zn＞Ni＞Cr.The average levels of heavy metals in vegetables is beloe the 'food hygiene standards',but some samples have a high level of heavt metal,we must pay attention to the healt risks. |
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