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Project Details:
Part 1: Investigation on heavy metal contents and speciation in swine manures in intensive livestock farms in the suburb of Hangzhou
Livestock and poultry manure have been widely applied as important fertilizer sources in agriculture. Application of organic manure to soils has been conducted to increase crop production by providing nutrients and organic materials that improve overall soil tilth and fertility. However, the use of feed additives to prevent diseases and improve weight gains has resulted in some organic manure containing high concentrations of Cu, Zn, Mn and As and so on. Thus, successive application of heave metal enriched manures to agricultural soils has been questioned due to concern about potential environmental hazards. For example, about 25-40% of the total annual Cu, Ni, and Zn inputs to agricultural lands in England and Wales from various sources derived from animal manure. However, most of the environment problems associated with land application of manure have centered on the contamination of groundwater and/or surface water with two major nutrients, N and P. Furthermore, most research on metal contamination in soils has been examined in relation to municipal sewage sludge application and, to date, very little work has been done in relation to metal input from livestock and poultry manures.
Part 2: Effects of forms of nitrogen fertilizer on the bioavailability of heavy metals in the soils amended with biosolids
Sludge is the deposited sediments produced in the process of sewage treatment plants. It is estimated that the amount of wet sludge generated only in municipal sewage treatment plant in China has exceeded 127.50 million m3. As to Hangzhou, sludge generated annually will amount to 20,000 t when wastewater treatment rate reach 30%. Land application of sludge has been conducted to increase crop production by providing nutrients and organic materials. However, the use of sludge as soil conditioner or fertilizer is limited by the elevated pollutant contents, particularly heavy metals. Although sludge was properly treated to reduce the activity of heavy metals and decrease their migration and uptake into plants, the heavy metals fixed temporarily in the sludge will be activated when soil conditions and plant rhizosphere environment changed. It is probable that the heavy metals will do harm to environment and human health because of their migration in soil and uptake by plants. Soil pH is one of most important factors affect heavy metal transformation, mobility in soils and bioavailability. The application of nitrogen fertilizers has distinct influence on soil pH and other soil properties. However, there were fewer reports on effect of different forms of nitrogen fertilizers on bioavailability of heavy metals. In the present study, the rhizobox experiment was conducted to elucidate the effects of different forms of nitrogen fertilizer on heavy metal bioavailability, so as to provide scientific basis for how to take measures to reduce uptake of heavy metal by plants and guarantee the safety of agricultural products.
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