Study On The Technologies For Heavy Metal Source Apportionment Of Agriculture Soils

There have been more and more heavy metal pollution events happened regularly in recent years. Hundreds of millions of people suffer from toxic effects of heavy metals. Heavy metal is eroding people’s health, even take the lives of people. As the problems of heavy metal excess levels in agricultural products arise, like "Cd rice", and agricultural safety caused by the heavy metal pollution is being paid more and more attention to, the research of heavy metal pollution in agricultural soils allows of no delay. Investigating and controlling the sources of heavy metal pollution in agricultural soil originally is one of the most effective ways to solve the problems of heavy metal pollution in soils, which is increasingly seen as crucial to treat for heavy metal in contaminated soils. People concentrated on researches of heavy metal pollution levels, harm mechanism of heavy metal in environment and human bodies and the removal of heavy metals in soils, etc. However, less investigation of sources of heavy metals in soils was being conducted in the past. At present, there still have no standard methods to trace the sources of heavy metals in agricultural soils, species and quantity message of manmade products and natural materials which could be potential sources of heavy metal pollutions in soils is not clear yet, basic data of discharges of heavy metal pollutants is lack, methods of tracing sources of heavy metal pollutions in soils should be improved. People now use single methods to investigate sources of heavy metals, which cause results of investigation become more partial and inaccurate. Therefore, it is necessary to find a new comprehensive method to investigate the sources of heavy metal pollutions in soils. The present study choose a typical area which has both agriculture and industry to research methods of investigating the sources of heavy metal pollutions in soils. On the basis of the investigation of local conditions, sample analysis and data calculation, final discussion and results are given in this study. The results showed:1. The local agriculture areas mainly is successive, a few of fields are like home gardens. There are major industries like electroplate factories, auto parts factories, printing and dyeing mills, etc and numerous of individual casting workshops located in the survey region. Local area mainly product cabbage, broccoli, rice, watermelon, sugarcane, etc, heavy metals in most of them were nearly in excess of the standards. As a whole, the level of Hg and Cd pollution was higher than Pb and Cr pollution in the local area. Samples of sources of heavy metals in soils collected from the survey region include chemical and organic fertilizer, industrial waste, road dust, irrigation water, etc. High concentration of Pb was found in industrial waste and road dust. High concentration of Hg was found in organic fertilizer, industrial waste and road dust. High concentration of Cd was found in chemical fertilizer and road dust. High concentration of Cr was found in organic fertilizer and road dust.2. Three methods of tracing sources of heavy metal pollutions in soils, including multivariate statistical analysis, spatial analysis and isotope ratio analysis, were summarized in this study. The results showed:The most possible sources of Pb pollution in soils were industrial waste and road dust, Pb pollution caused by road dust distributed widely and concentrate in middle level, while Pb pollution caused by industrial waste distributed narrow and concentrated in high level. The most possible sources of Hg pollution in soils were organic fertilizer, industrial waste and road dust, Hg pollution caused by organic fertilizer mainly distributed in the agriculture areas far from industries and roads, Hg pollution caused by road dust was near the roads and distributed widely, Hg pollution caused by industrial waste distributed narrow and concentrated in high level. The most possible sources of Cd pollution in soils were industrial waste, but also was possible because of unknown pollutant sources. The most possible sources of Cr pollution in soils were organic fertilizer and road dust, Cr pollution caused by organic fertilizer mainly distributed in the agriculture areas far from industries and roads, Cr pollution caused by road dust was near the roads and distributed widely. In addition, waste water of electroplate factories also was a real source of Cr in local area according to the investigation.3. The methods of tracing sources of heavy metal pollutions in soils was improved in the present study. Principal component analysis and clustering analysis from multivariate statistical analysis was chosen on the basis of its principle and feature. Inverse Distance Weighted (IDW) was used in spatial analysis as a appropriate interpolation method which considered the effects of processing data. The measurement processes of isotope ratio were improved to increase accuracy, contribution calculation model was used to deal with isotope ratio data.