| Fertilization and other agricultural activities can bing some heavy metal into soil. Heavy metal moves hardly 1 and accumulate easily in soi. Therefore, study on heavy metal environment proceeding have an important academic and practical significance for proctecting soil entironment, ensuring agricultural quality and achieving agricultural continuable development. At present, there are a lot of studys about changing characteristic of soil nutrient, however, there are little reports on content of heavy metal in soil under long-term fertilization. This paper was studied on the effects different fertilizer treatments on heavy metal content and it's form change in soil ,as well as analysed the biologic availabibity of heavy metal by using long-term fertilization experiment and laboratory analysis method.The results of tong-term fertilization for 15 years showed that Pb,Cd,Zn,Fe,Cu were obviously enriched in plowland (0-20cm). The totle content of Pb,Cd,Zn,Fe,Cu were respectively increased 51.6%,30.9%,8.7%,72.8%,25.2%, but the totle content of Cr,Mn are reduced 15.7%,9.7% in 2006 compared with 1991. The soil Cd content (1.87mg/Kg-2.66mg/Kg) overstep the third class standard of country soil environmental quality (1.00mg/Kg) ,however, the Pb,Cr,Cu,Zn,Fe content are all in the range of first class standard of country soil environmental quality,and they could not bring about damage in a short time.All of the treatments of soil total Pb content had increased obviously, and the Pb content of topsoil overtoped soil plow sole, the content of Pb in top soil had increased 51.6% and in soil plow sole had increased 19.5% in 2006 compared with 1991. After 15 years, the treatment of blank of Pb content had increased 56.5mg/kg, and the treatments with fertilizer had increased 51.0mg/kg, so we can see that the fertilizer in different treatments have little difference, It is indicated that the commucatin of soil Pb are mainly come form the external environment as dry and wet settlement in this 15 years. As to the commucation of soil Pb , the external environment contribution is overtoped applying fertilizer. The long-term fertilization had increased the Content of soil available Pb, but the treatment of CK had lilttle chang.Afert 15 years reasearch of long-term fertilization, the content of topsoil total Cd had increased, but the content of soil plow sole total Cd had little changed; applying phosphate fertilizer had increased the content of soil totle Cd, for example, the content of soil Cd in the treatments of PK, NPK,NPK+S are obviously overtop other treatments . long-term fertilization had increased the content of topsoil available Cd, the content of soil available Cd in the treatments of Applying fertilizer increased 23.4% compared with CK, and so it had increased the plant validity. Different other heavy metals, the content of soil plow sole Cr are overtop the topsoil Cr; Th content of soil totle Cr had reduced but the content of soil available Cr had increased after 15 years. And the increas of the content of soil plow sole available Cr overtop the topsoil.The content of topsoil total Zn had increased, but the content of soil plow sole total Zn had reduced in 2006 compared with 1991; the content of soil available Zn has increased except the treatment of CK(0-20cm) and NK (20-40cm), but the content of soil available Zn in most of treatments are in the range of 0.4～1.0mg/kg, except the treatments of M and S (they are overtop the content of 1.0mg/k).The content of topsoil totle and soil plow sole had reduced; The content of soil plow sole totle Mn had increased, but the content of soil plow sole available Mn had reduced (from 43.3mg/kg to 4.5mg/kg) in the 15 years. In the condition of rice field-upland field rotation ,soil Mn had moved downward and be soaked, so we must do more attation to applying Mn fertilizer in dry farming wheat. After 15 years' rice field-upland field rotation, the content of soil in 2040cm totle Fe had obviously increased,and all treatments had little difference; The long-term fertilization had increased the content of soil available Fe, but it's content in the treatment of CK had reduced. The content of soil total Cu in all of the treatments had increased more or less in 2006 compared with 1991, and the content of soil available Cu in other treatment are obviously reduced except the treatment of S.The correlativity between the content of soil available heavy metal and soil totel heavy metal indicate that the content of soil available Cu, Cr and the content of soil total Cu,Cr are related, and it's effectiveness of the crop is depend on the soil itself; However, the correlativity between the content of soil available Zn,Pb,Cd,Fe,Mn and soil totel Zn,Pb,Cd,Fe,Mn are no significant correlation,So, we can conclude that this 5 heavy metals on the effectiveness of crop major soil environmental and external conditions impact. The Speciation of soil Pb,Cd,Zn,Cu are mainly RES, and the order of soil form Pb is RES(60.8%)>Fe-Mn (28.6%) >O.M (8.2%) >EX (2.4%), different fertilizer had brought great influence to the EX and O.M of Pb ,but the influence to the RES and Fe-Mn is little. The treatments of applying fertilizer compared with the treatment of CK, applying fertilizer had reduced the EX of Pb, and increased the O.M of Pb. the order of soil form Cd is RES(58.5%) >EX (18.1%) >Fe-Mn (14.2%) >CAB (9.2%), different fertilizer had brought great influence to the EX and CAB of Cd ,K increased the content of EX Cd, applying fertilizer and organic fertilizer had obviously reduced the content of CAB Cd. The correlativity between the content of Speciation of soil heavy metals and rice heavy metals are low correlation, the correlativity between the soil Fe-Mn Cu content and the heavy metal content of wheat grian are significant correlation. The order of bioavailability of heavy metals and mobility of heavy metals in soil in Cd>Pb>Zn>Cu.Wheat and rice have a strong enrichment to the soil Cr, also fertilizer in different treatments have little influence to Cr, but the content of Cr in Wheat and rice had overstep the safety standards of food hygiene,it is because the purple soil Cr is high, and crop have a strong enrichment to Cr. long-term fertilization had influenced the content of heavy metals of wheat and rice, compared with CK, applying fertilizer had increased the content of Cd,Pb of wheat and rice(except the treatment of N); Applying phosphor and kalium had increased the content of Cd,Pb of wheat and rice; The content of Pb of wheat and rice in all of the treatments had overstep the safety standards of food hygiene; The content of Cd of wheat grain did not overstep the safety standards of food hygiene, because rice have the a stronger enrichment than wheat. In the test, we must control the soil and crop pollution from exterior heavy metals. |
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