Analysis Of Taiyuan Sewage Irrigation Areas Available Heavy Metals Content In Soils And Crops

Irrigation with sewage water is not only can save lots of water, but also the nutrition materials in, the sewage water are conducive to the growth of plants. Currently, people use sewage water for agricultural irrigation; the majority of the sewage was untreated. Wastewater containing heavy metals, organic matter and other pollutants, these pollutants can be accumulated in the soil, and get into the food chain through crop uptake resulting in harm to human body. Volatile organic compounds in the soil easily volatilize. In the study areas which had been irrigatated by polluted water in the long period. We choose eight heavy metals Cu, Zn, Pb, Cd, Mn, Ni, As and Hg as the main object of study. Available heavy metals in soil are the main absorbing form of crops. So it is important for sewage irrigation to analyze in the soil migration law, factors of available heavy metal content and heavy metal content in crop.In this study, there are four typical irrigation area of Taiyuan: Xiaodian,Jinyuan, Jiancaoping and Qingxu as the main study areas. Through the subject of the 150 soil samples which from the five soil layers of the 12 points (0～20cm,20～40cm,40～60cm,60～80cm,80～100cm), determine the total volume and effective contents of Cu, Zn, Pb, Cd, Mn, Ni, As and Hg, soil pH and the typical crop of heavy metals and the vertical migration of Pb, Zn, Cu, Ni, Mn and Cu content of soil. Through calculative evaluation and theoretic analysis, some knowledge are acquired as follows:1. According to the heavy metals content in Taiyuan wastewater irrigation areas, we can know, heavy metal manganese in soils, Mn, As, Cd and Pb content Xiaodian district, Jinyuan district in soils of are higher than the other three areas, Qingxu county available Hg content was the highest, Jiancaoping District the measured content of eight heavy metals are in the middle level. 2. The eight heavy metals transformation in soil profiles are grouped into three types:(1)The surface accumulation higher than the lower ground floor, including Cu, Zn, Ni, As. (2) The lower surface of bottom deposition. Only Pb belongs to this type. (3) Content in soil was distributed interval, including Mn, Cd and Mn.3. There were positively relations between the amount of heavy metals in sewage irrigated soil and available heavy metals. Available heavy metal content had a negative relation to soil pH.4. The crop classification can be showed that heavy metals of fruit crops Cu, Ni and Cd were higher, The content of Mn and Pb in leafy vegetables is high, heavy metal Zn content in the root crops were the highest. Heavy metals in Taiyuan sewage irrigation main crops of Ni, Cu and Zn were lower than limit value. The content of Pb in corn and lettuce is higher than limit value.