| Soil is the essential biological habitat and the foundation of human civilization,and the quality of soil environment is related to human health and social stability.Chinese agricultural soil environment is under tremendous pressure due to the longterm and deep impacts from human activities including the rapid expansion of urbanization,the continuous development of industrialization,and the high intensity utilization of agriculture.It is urgent to manage the soil environment because of the characteristics of soil heavy metal including high toxicity,long-term,and complexity.Understanding the situation of soil heavy metal pollution is an important basis for accurately assessing pollution risk levels and carrying out pollution prevention and control work.Large-scale regional soil environmental quality surveys usually costs high time and labor,and the published soil pollution research results are numerous but lack regional representativeness.This thesis took agricultural soil in the Yangtze River Delta(YRD)as the research object,based on the Meta-analysis,synthesized smallscale literature data to obtain the large-scale area soil heavy metal pollution situation and spatial and temporal distribution characteristics.The main research and conclusion are as follows:(1)The study collected 118 relevant literatures and extracted 986 heavy metal pollution data.Taking into account the basic idea of Meta-analysis and the characteristics of literature data,the number of sampling points,the area of the study area,and the standard deviation of the data were introduced as weighting factors to participate in the calculation.According to the results of data heterogeneity analysis,the random-effects model was used to calculate the mean value of heavy metal content in agricultural soils in the YRD.It could be seen that the average concentration of Cd,Hg,As,Pb,Cr,Cu,Zn and Ni in the soil were 0.25 mg/kg,0.14 mg/kg,8.14 mg/kg,32.32 mg/kg,68.84 mg/kg,respectively.32.58 mg/kg,92.35 mg/kg,and 29.30 mg/kg respectively,the data results were basically consistent with the national average soil heavy metal content.Compared with the background value of the soil environment,the other six heavy metal elements except Cd and Hg had no obvious accumulation trend in the agricultural soil of the YRD.(2)The study analyzed the distribution characteristics of heavy metal content in farmland soils of provinces and cities in the YRD,and used the potential ecological risk index to assess the pollution risk level.The consequence indicated that the pollution risk level of heavy metals in the overall soil of the YRD was moderate,and the pollution risk mainly come from Cd and Hg elements.Some area have relatively higher pollution risk,which were closely related to the mining and smelting activities.The temporal trend of the average heavy metal content in the agricultural soil of the YRD was analyzed.The results showed that the content of Cd,Hg,As,Pb,Zn and Ni in the soil showed a downward trend between 1993 to2020,and the decline rate of different elements was different.(3)In order to realize the standardized management,security sharing and visual expression of soil pollution data,this research used Web GIS technology to develop the YRD soil pollution shared database system.The system included three functional modules: literature query,data query and map display,to meet the functional requirements of operators for previewing literature text,querying pollutant information,and visualizing pollution distribution maps.The system provides effective tools for the detection,prevention and management of soil pollution in the YRD. |
PDF Full Text Request