| With MSWIP (municipal solid waste incineration plant) being applied widely, tail gas of MSWIP will influent on environment. MSW (municipal solid waste) is collected with mixed method in China, containing a great quantity of heavy metals. while with the speeding up of urbanization, the expansion of the matching network and the rapid development of industry. many incinerators are no longer isolated pollution sources, which surrounding also includes industrial, traffic sources, agricultural sources and others.it is of vital important to research heavy metal source analysis in the area of soil.But for incinerators around a variety of heavy metal pollution in soil characteristics, source analysis and comprehensive assessment research is still relatively rare.Chongqing is the fourth municipality in china, with rapid economic development in recent years, the waste of the siege problem is increasingly serious as well. Incineration is the important means to solve the problem of waste of chongqing, ChongQing incinerators have been put into operation for many years. The incinerator of the region and the current research of geographical climate conditions have significant difference. This area is a typical mountainous, hilly topography and meteorological conditions with small static wind have limited diffusion, MSWI pollutants will be settled in a relatively small area near the soil. At the same time, the heavy metals in soils is difficult to migrated, and incinerator design life is very long, the emissions of heavy metals accumulation, will engender the environment risk. There were lack of relevant research data and theoretical support to determine and predict risk of such a kind of environment.This study takes ChongQing incinerators as the research object,using multivariate statistics to study the physical and chemical properties of the soil surrounding the waste incinerator,and the correlation between physical and chemical properties of soil and concentrations of heavy metals in soils.6 heavy metals (Cr,Mn,Cu,Pb,Zn and Fe) were analyzed by GIS and geostatistics analysis in soil samples which were collected from the area has mountain terrain characteristics surrounding the ChongQing incinerator to study spatial distribution. Using Pearson coefficient method, principal component analysis, Variation function structure analysis,enrichment factor method to analyze heavy metal sedimentation characteristics and source.While, the spatial distribution maps of heavy metal content of the surface soil in this region were produced by means of the optimum kriging interpolation. The single pollution index,geoaccumulative index method and the composite pollution index were used to evaluate the soil heavy metal pollution. Pollution source analysis are used for environmental studies and give an objective and scientific consistency to evaluate heavy metals pollution condition. There were two main aims of the study,firstly,to evaluate the presence of trace metals in the soil around MSWI with mountain area and small wind climate, and secondly,to provide important theoretical support for the similar area exhaust pollution control and environmental risk assessment. Main conclusions are as follows:(1) Physicochemical characteristics analysis results show that the soil pH of the study area were 3.71 to7.95,the average value was 6.46;the range of Electrical conductivity (EC) were 7.00 to 837 us/cm; With a mean of 110.36 us/cm;the range of Oxidation reduction potential (ORP) were-58 to 180 mv, the average was 37.72 mv;The TOC content is 8.65 to 69.17 mg/kg, the average was 13.74 mg/kg; The content of CEC were 2.24 to 37.88 cmol/kg, with a mean of 26.8 cmol/kg. A clear correlation were not presented between the physical and chemical properties in the soil of study area. this may be associated with soil background and environmental conditions.(2) In the surface layer and subsurface of soil surrouding the MSWI plant,Cr, Mn, Fe, Cu and Zn, the average contents of six kinds of heavy metal were 216.74,639.33,38134.93,33.67, 69.79,47.96 mg·kg-1,respectively. The measured Cr, Pb, Cu content were higher than the background value,which showed have influenced distinctly by human.(3) Using Pearson correlation coefficient method to analyze their relevance,including the relativity analysis of six kinds of heavy metals as well as the correlation between the physical and chemical properties and analysis of heavy metals. The results showed:The Oxido-reduction Potential (ORP) and pH has significant correlation with Pb, Zn, respectively.And has significant correlation with Mn. Declaring the pH and ORP in the physical and chemical properties of the content of Mn in the soil surrounding the incinerator has a great influence. The content of Zn, Pb were affected by the ORP and pH.(4) Clustering and principal component analysis showed that the six kinds of heavy metals could be four components. The first principal component were Zn and Pb; The second principal components were Fe, Mn;the third principal component was Cu; the fourth principal component was Cr. The clustering of heavy metals in the soil surrounding the incinerator showed that Zn and Pb had similarities, their source or origin is similar; Fe andMn have similarities, Cu and Cr, respectively, have different sources.(5) Sources of analytical results showed:the first principal component Pb and Zn,with recent high concentration area was distributed in the early years of small family factory clusters, mainly affected by industrial pollution residues; The second principal component distribution of Fe and Mn without clear regularity,mainly be considered as an expression of the soil biogeochemical effect of circumstance. As the third principal component;Cu mainly considered as an expression of the agricultural use of the soil and vehicular traffic pollution;industrial pollution was the source causing Cr pollution.(6) Discusses the influence of the terrain and incinerators interannual variability of the heavy metal concentration distribution in the soil surrounding the incinerator, the results showed that there were no clear correlation between content of heavy metals in soil and elevation.It may also be derived from waste incineration exhaust has not caused obvious heavy metal pollution surrounding the soil, the sides towards or back to waste incineration exhaust of the hills has no obvious regularity of heavy metal concentration in the soil.it may be results of small wind climate conditions and lower source from incinerators.(7) Interannual variation histogram of heavy metals indicated the interannual variation of Cr, Mn, Fe, Cu and Zn presents the obvious normal distribution.which concentrated from 0.0 to 0.2.The field investigation showed the interannual variability of heavy metals were fit for their sources extremely. While Pb has increased slightly compared with the previous year in the area of roads and few located in the traffic and industrial source.The traffic impact may as another supplement source of Pb.Waste incineration source might have contributed to the change of Pb, was likely to be the short time.(8) Results of pollution assessment of the research area of soil heavy metal indicated that the single factor pollution index of Mn and Fe was 1.01 and 1.01 respectively, they were no pollution; the single factor pollution index of Cu, Zn and Pb was 1.83,1.23 and 1.70, which were the light pollution; the single factor pollution index of Cr was 2.03 on average, was moderate pollution.The average composite pollution index was 1.91 and it was light contamination. Geoaccumulation index analysis showed that Cr, Mn, Fe, Cu,Zn and Pb had no obvious cumulative pollution completely. |
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