| At present,with the development of economy and society,the problem of soil heavy metal pollution is becoming more and more serious.Vegetables are one of the necessities of daily life,and it is of great significance to ensure their safety.Shandong Province is a big province of vegetable production,we research on the origin of soil heavy metals pollution of vegetable in Shandong Province should not only be limited to the evaluation of the total heavy metal,should also include the study of soil heavy metal forms,so as to provide the production safety and the prevention and control of soil heavy metals pollution of vegetable theory basis.So we choose two typical vegetable producing areas in Fangcun of Tai'an and Shouguang of Weifang as the study area.And I measure the soil physicochemical properties,the soil heavy metal content,the soil heavy metal content of each form,and analyze correlation between heavy metal content and the soil physicochemical properties,the influencing factors of the various forms of heavy metals and the bioavailability of the heavy metals.The main results are as follows:?1?The results of the study of regional physicochemical properties showed that:The average pH value of Fangcun soil was 6.40,it was weak acid soil,the water content was15.40%,and the percentage of clay particles was 7.75%.The average content of soil organic matter?OM?,available nitrogen?AN?,available phosphorus?AP?and available potassium?AK?are 25.69 g·kg-1,139.77 mg·kg-1,268.28 mg·kg-1,411.13 mg·kg-1,and the soil fertility is better.The average pH value of Shouguang soil is 7.33,the soil is neutral,the moisture content is 15.89%,and the percentage of clay is 7.55%.The average content of soil organic matter?OM?,available nitrogen?AN?,available phosphorus?AP?and available potassium?AK?are 18.80 mg·kg-1,57.32 mg·kg-1,171.18 mg·kg-1,332.81 mg·kg-1.The content of organic matter?OM?and the average content of available nitrogen?AN?are not very high,which is lower than that of the study area in the village.?2?The determination of heavy metal content in the study area soil by atomic absorption spectrometry shows that:The average contents of Zn,Cu,Pb and Cr in the Fangcun soil are respectively 87.51 mg·kg-1,36.92 mg·kg-1,21.11 mg·kg-1,69.99 mg·kg-1.The average contents of Zn,Cu,Pb and Cr in the Shouguang soil are respectively 144.00mg·kg-1,32.34mg·kg-1,30.30 mg·kg-1,85.73 mg·kg-1.At the same time,the concents of Cd are not detected by AA-7000 atomic spectrophotometer in the two regions.The average content of the regional elements Zn,Cu,Pb and Cr were higher than that of the agricultural soil background values in Shandong Province,but all were lower than the value of environmental quality evaluation standard for greenhouse vegetable production?HJ333-2006?.?3?The results of the modified BCR method for the determination of heavy metals in the soil in the study area showed that the proportion of the chemical forms of heavy metals in the soil was different.The proportion of the four forms of heavy metals in the Fangcun study area:Zn residual>reducible>acid soluble>oxidizable,Cu residual>reducible>oxidizable>acid soluble,Pb residual>reducible>oxidizable>acid soluble,Cr residual>oxidizable>reducible>acid soluble;the proportion of the four forms of heavy metals in the Shouguang study area:Zn residual>reducible>acid soluble>oxidizable,Cu residual>reducible>oxidizable>acid soluble,Pb residual>reducible>oxidizable>acid soluble,Cr residual>oxidizable>reducible>acid soluble.?4?The analysis of the influence factors of soil heavy metals in the study area showed that the soil elements Cu and Zn showed significant correlation,Pb and Cr also showed significant correlation,indicating that Cu and Zn,Pb and Cr may have some homology;element Cu and the content of physicochemical properties of available nitrogen?AN?,available potassium?AK?and available phosphorus?AP?content.There was significant correlation between the element Zn and available potassium?AK??soil water content.Element Pb showed significant correlation with soil pH,organic matter?OM?,available nitrogen?AN?,available phosphorus?AP?,available potassium?AK?,clay grains and planting years.Element Cr had a significant correlation with soil pH.?5?The analysis of the influence factors of heavy metal forms in regional soil showed that:The acid soluble state,reducible state,oxidizable state and residual state of Zn?Cu and the acid soluble state,reducible state,and oxidizable state of Pb showed significant correlation with the total amount of elements.The reducible,oxidizable and residual states of Cr have significant correlation with the total amount.The acid soluble states of Zn have significant correlation with the available phosphorus?AP?,available potassium?AK?and water content of soil physical and chemical properties,but the reducible state is only with the available potassium?AK?.There is significant correlation between the oxidizable state and the soil pH,and the residual state has a significant correlation with the organic matter?OM?,available phosphorus?AP?,available potassium?AK?and water content in the soil;the acid soluble state and the reducible state of the Cu have significant correlation with the available nitrogen?AN?.There is significant correlation between chemical state and available nitrogen?AN?and available phosphorus?AP?.Residual state has significant correlation with soil pH,organic matter?OM?,available phosphorus?AP?,available potassium?AK?and water content.The acid soluble state of Pb is closely related to soil pH,organic matter?OM?,available phosphorus?AP?and available potassium?AK?,and the reducible state and available nitrogen?AN?are effective.There is significant correlation between oxidizable between available phosphorus?AP?and soil available nitrogen?AN?.Residual state and organic matter?OM?have significant correlation.The acid soluble state of Cr have significant correlation with soil pH,organic matter?OM?,available nitrogen?AN?and available phosphorus?AP?,and the reducible state and soil pH,available phosphorus?AP?,available potassium?AK?and the clay particles.And there was a significant correlation between the oxidizable state and the available phosphorus?AP?,the available potassium?AK?,the water content and the percentage of the clay particles.The residual state was significantly correlated with the soil pH,organic matter?OM?,available nitrogen?AN?and available phosphorus?AP?.?6?The study on the bioavailability of heavy metals in the soil showed that:The bioavailability of elements Cu,Pb and Cr was low,and the environmental risk was low.Only the environmental risk of Zn was medium,but it was also safe because Zn was a necessary element for vegetable growth. |
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