Response Of Soil Heavy Metal Accumulation To Land Use And Landscape Patterns

Land use type and land cover have been profoundly changed by human activities with a result of a series ecological and environmental issues.Pollution of soil heavy metal is one of them.The land use/land cover change and landscape patterns change reflect the temporal-spatial influence of human activities,and therefore,is an important point of entry in study of soil heavy metal accumulation process,influencing factors and its mechanism.This study took X city in Zhejiang province as an example,by obtaining the multi-temporal land use/land cover remote sensing information and analyzing the comprehensive pollution degree of eight soil heavy metal(As,Cd,Cr,Cu,Hg,Ni,Pb,Zn),it revealed the relationships between soil heavy metal accumulation and land use/land cover change and landscape patterns change.Based on that,the study analyzed the reponse of soil heavy metal accumulation to land use and landscape patterns quantitatively by introducing the theory and method of ordination in ecology.It provides useful supplements to understanding the relationship between landscape patterns and accumulation process of heavy metals and discovering the mechanism of accumulation occurrence and inherent laws of heavy metal pollution.It also provides scientific basis and decision-making references for exploring landscape ecology approaches for the prevention and control of heavy metal pollution risks and rational allocation and sustainable utilization of land resources.The main conclusions are as follows:(1)the main land use/land cover changes in the study area from 2003 to 2013 are:cultivated land to residential land and industrial land,water to industrial land.Cultivated land,forest and water area decreased with different degrees while construction land area increased significantly with a large amount of cultivated land changing for residential land and industrial land.Socio-economic factors including population growth and industrial development may be an important driving force for the increase of construction land.(2)the heavy metal pollution in the study area has changed from single pollution to compound pollution,and from point source pollution to non-point source pollution.Seven soil heavy metals except Cd showed different degrees of accumulation with the highest accumulation of Hg,Ni and Cr.The spatial variability of the eight heavy metals contents generally got more volatile with more local high-value areas.The comprehesive pollution degree in 2013 was significantly higher than in 2003.Most areas have been polluted by the soil heavy metal,and the pollution degree of the heavily polluted area continued to increase.(3)the pollution increased in construction land and cultivated land changing from other land use types.The landscape patterns in polluted area are fragmented,complex and aggregated.The trend of more fragmented,complex and agglomerated landscape patterns of cultivated land,residential land and industrial land was most closely related to the soil heavy metal accumulation.(4)the redundancy analysis of soil heavy metal accumulation and land use and landscape patterns indicated that:the accumulation of most soil heavy metal will increase significantly with the patches in construction land getting more agglomerated.With higher degree of landscape diversity and more complex shape of the cultivated land and garden plots,the accumulation of Cu,Hg,Pb and Cd will get higher.The content of Cd will increase obviously with shorter distance to the mining site.In addition,the interaction between shape factor(landscape shape index of cultivated land and garden plots)and heterogeneity factor(Shannon's diversity index)should not be ignored.(4)the study discussed an environment-friendly land use optimization method,including the optimization of land use structure based on pollution source control and optimization of landscape pattern based on "source-sink" theory.