Investigation And Evaluaiton About Heavy Metals Pollution Of Vegetables And Soils In Cixi

Influenced by many aspects such as environment,man’s activities,features of crops and so on,theheavy metal was one of the important factors of affecting the quality safety of agricultural products.Thisproject included three objects of study: the agricultural area near industry,the agricultural area on bothsides of the road,and the normal agricultural area. By detecting the content of Pb,Cd,Cr,Cu,Hg,and Asin the vegetabls and soils in the three areas,the six heavy metals pollution level of vegetables and relatedsoils in Cixi would be fundamentally grasped to analyse and compare the features of pollution andreasonable causes of soils and vegetables from different areas.The study on heavy metals in three region showed, the averages of Pb,Cd,Cr,Cu,Hg and As were21.0~22.8,0.14~0.25,66.4~74.5,25.9~31.9,0.0762~0.0925and6.13~6.92mg/kg, but Cr and Cd hadsignificant difference.With the method of integrated pollution index and the standard of the naturalbackground values of elements,the result of the assessment in the three areas showed,the agriculturalarea on both sides of the road reached the light pollution level and the index was1.01; the normalagricultural area and the agricultural area near industry reached the alert level and the index were0.72and0.78.According to the standard of green food environment of porduction area and the second levelcriterion of standard of soil Environment,the three areas were all non-polluted. The results of furtheranalysis showed that the heavy metals pollution level were Cd>Cu>Cr>Pb>As>Hg in the agriculturalarea near industry and the index of Cd was1.09and reached the light pollution level; the heavy metalspollution level were Cd>Cr>Pb>Cu>As>Hg in the agricultural area on both sides of the road，and theindex of Cd was1.37and reached the light pollution level，and the index of Cr was0.70and reachedthe alert level,and the others index were0.32~0.50;the heavy metals pollution in the normal agriculturalarea was Cr>Cu=Pb>Cd>Hg>As and the index was0.38~0.64.By analysing the possible source of thepollution,the Cd polltion in the agricultural area near industry and the agricultural area on both sides ofthe road were connected with the agricultural intensification,the frequence of repeated planting andfertilizers,especially the organic fertilizer,while the Cu pollution in the agricultural area near industrywere mainly from melting.The content of Cd in the three areas,higher than normal was due to the nativeoriginal soils.With the standard of GB2762-2012the maximum allowable amounts of contaminants in certainfoods,8of the156samples in the three areas were unqualified and the qualified rate was94.9％.With the integrated pollution index to all kinds of vegetables,the combined pollution of heavymetals index was low,ranging0.13~0.29. Pollution level:solanaceous vegetable>legume vegetable>leafvegetable>root vegetable>brassica vegetable.With the comparison of each heavy metal’s damage to theenvironment,the index of Pb was1.05and the most dangerous,reaching the light pollution levelmoreover the risker of legumes and leaves and solanaceouses; the next was Cd of0.71,reaching the alertlevel morever the risker of leaves and legumes;Cr,Hg and As were almost non-polluted and the index of0.06~0.29.With the analysis of the integrated pollution index to collection areas and kinds of vegetables, the combined pollution of heavy metals index of leaf vegetable: the gricultural area on both sides of theroad>the normal agricultural area> the agricultural area near industry; the combined pollution of heavymtals index of legume vegetable: the agricultural area near industry>the agricultural area on both sidesof the road>the normal agricultural area; the combined pollution of heavy mtals index of brassicavegetable:the he agricultural area on both sides of the road>the normal agricultural area>the agriculturalarea near industry; the combined pollution of heavy metals index of root vegetable: the normalagricultural area>the agricultural area near industry>the agricultural area on both sides of the road; thecombined pollution of heavy metals index of solanaceous vegetable: the agricultural area on both sidesof the road>the agricultural area near industry>the normal agricultural area.With further analysis of eachheavy metal’s damage to the environment,Cd pollution had the highest risk in the agricultural area onboth sides of the road.The possible reason was the high content of Cd in the soils on both sides of theroad and the many applications of some cultivating additions,especially the organic fertilizer.Pbpollution had the highest risk in the agricultural area near industry because of the small pollutedenvironment there.In a conclusion,the inevitable relevance between soils and the heavy metals pollution of vegetableswas not found.The reasons were as follows:Firstly,the quality of the alkaline soils in the areas was wellas a whole,and the vitality of heavy metals was poor enough not to directly threaten the safetyproduction of vegetables.Secondly,there was a big gap at the adsorption capacity to heavy metals amongwide varieties of vegetables.Thirdly,the risk of the heavy metals pollution depended on the difference ofthe production styles of agriculture and the different applications of agricultural inputs.