Study On Heavy Metals Pollution In Farmland Soils Around Scale Swine-farm

With the rapid development of scale swine-farms in China, the swine waste which was brought by intensive hoggery was disposed in farmland soils around swine farm region. Due to plentiful heavy metals in swine waste, heavy metals can be accumulated in soils if long-term and large quantity swine manure is applied. Studing heavy metals in swine waste could regulate the recycling of swine waste and prevent the accumulation of heavy metals in soils, and put forward the countermeasure of interdiction and control of agricultural tri-dimensional pollution of heavy metals brought from swine breeding industry.The disposition technics of swine waste were investigated and the characteristics of swine wastewater was measured in numbers of swine-farms. The object of this studing research was heavy metals in swine waste which could be accumulated in soils and the area researched was the farmland around swine-farm. The results of the field trials and pot trials were further illuminated the accumulation effect of heavy metals.Innovation and characteristics of this paper include:1. The source of heavy metals were distinguished according to correlation analysis, principal component analysis, geostatistical and GIS, which could draw the conclusion that Zn, Cu, Mn and As come from swine waste, Cd from swine waste and fertilizer, Pb from fertilizer, and Ni and Cr from soils material.2. It can be forecasted the accumulation of some heavy metals in soils. According to the model, the total concentration of Cu and Zn in soils could exceed the second grade of the national farmland soil environmental standard after 10 and 15 years of continual swine manure-applied with the 150 m³.hm^-2.a quantity respectively.3. The pH would decrease after swine waste applied, and the bioavailability concentration of heavy metals would increase and the environmental risk of heavy metals would increase.Main conclusions were got from the former research:1 Investigation and trials showed T-Zn, T-Cu and T-Mn could increase, and T-Cd, T-Ni, T-Cr, T-Pb and T-As could increase indistinctively, and the bioavailability content of heavy metals would increase, pH would decrease after swine manure or swine wastewater long-term applied in soils. The bioavailability content of heavy metals could increase and have negative relation with pH (p<0.05). According to the model, the total concentration of Cu and Zn in soils would exceede the second grade of the national farmland soil environmental standard after 10 and 15 years continual swine manure-applied with the 150 m³.hm^-2.a quantity respectively. The content of heavy metals in soils sewage-irrigated was higher than that in soils groundwater-irrigated obviously.As had short-term accumulation and Cr, Ni, Mn, Pb to some degree, and Cd were not accumulated evidently in soils applied swine manure. With the increase of swine manure quantity applied, B-Zn, B-Cu, B-Cd, B-Pb, B-Mn and B-As could increase. When the swine manure quantity applied in unit area was 600m³.hm^-2, T-Zn and T-Cu increased from 55 mg.kg^-1 and 20 mg.kg^-1 to 120 mg.kg^-1 and 50 mg.kg^-1 respectively, the former was twice than the latter, and B-Zn, B-Cu, B-Mn, B-Pb and B-As in soils were fivefold, tenfold, fourfold, threefold and twice than that in CK soils respectively.2 The content of heavy metals in kernel collected in sewage-irrigated soils was higher than that collected in groundwater-irrigated soils as a whole, and the content of Zn, Cu, Mn, Cd, Ni, Cr and As was varied with the total and bio-available concentration of that in the same direction. It was showed through field trials and pot trials that the content of Zn, Cu and Mn in cole was relational to the total content and bio-available content of that in soils respectively, and the content of As was relational to the total content and bio-available content of As in soils indistinctively, and the content of Cd, Ni, Pb and Cr in cole was under the measure limit.3 The source of heavy metals could be well distinguished according to correlation analysis, principal component analysis, geostatistical and GIS, and the fractal dimension could interpret the results of variogram. Cconclusion would be drawn that Zn, Cu, Mn and As were come from swine waste, and Cd was come from swine waste and fertilizer, and Pb was come from fertilizer, and Ni and Cr were come from soils material from the multianalysis, geostatistical and GIS.4 The results indicated that the spatial variability of Zn, Cu and As was related principally to quantity and character of swine wastewater irrigated and land use, but had little to do with the distribution of small regional scale, soils material and cropping system, and Cr and Ni was related principally to soils material and land use. But the spatial variability of all of the bio-available heavy metals was was related principally to the quantity and character of swine wastewater irrigated.5 From the analysis of single factor pollution index, Nemerow compositive pollution index, Hakanson potential risk assessment index and Geoaccumulation index, it was indicated that Zn, Cu, Cr, Ni, Pb and As in soils were light pollution, and B-Cd and B-Pb were no pollution or light pollution, and B-As was medium grade pollution where applied swine wastewater 8 years continuously or swine manure 4 years continuously whose total quantity was 624.00±273.64 m³.hm^-2, and B-Zn and B-Cu were medium-strong or strong grade pollution. The potential ecology risk index (RI) was moderate risk.In a word, swine manure or swine wastewater was long-terms and continually applied in soils, whose pH would decrease and Cu and Zn could be accumulated, and As could be accumulated to some degree, which would bring the pollution risk of the total content and bio-available content of heavy metals to some extent. Though the index of heavy metals were light or moderate pollution after swine wastewater applied 8 years continually, the bio-available content of heavy metals in soils could be increased because pH in soils could be decreased, which could increase potential ecology risk of heavy metals. To decrease the environmental risk of heavy metals accumulation in soils which were applied swine waste, the measures could be that the swine waste quantity applied per unit farmland should be decreased, and pH should be increased to decrease the bio-available content of heavy metals, and the environment-friendly feed should be developed to cut off the headstream of heavy metals to the environment.