The Effect Of Different Land Use Patterns On Distribution Of Soil Heavy Metals In Jiaodong Mountain Area

Land use as a comprehensive reflection of the various activities of human use of land is the most common,direct and profound factor affecting soil quality change.The heavy metal content of soil is an important index to evaluate the environmental quality of agricultural products.It is very important to analyze the effect of land use change on soil heavy metal pollution.Qixia City as the main producing areas of China's apple,to understand the accumulation of heavy metals in the history of apple planting,to ensure the safety of agricultural products,ecological security and human health.In this paper,the remote sensing images of Qixia City in 1987,1992,1997,2002 and 2007 were used as data sources,combined with the statistical data of the study area,environmental annual report and other information,At the same time,field investigation and field visits were conducted to obtain the data of land use change in the past 20 years.The dynamic changes of land use in Qixia City were analyzed on GIS platform.According to the cumulative characteristics of heavy metals,the soil heavy metal survey data of Qixia City in 2007 were used as static data sources,and the land use change was simulated by static data.The effects of land use change and land use change on soil heavy metal accumulation in Qixia were studied.Conclusion are listed below:(1)During the period from 1987 to 2007,the area of grassland and grassland in Qixia City increased and then decreased,and the area of cultivated land and unused land decreased continuously.The area of forest land and construction land increased continuously,and the land use rate was the fastest.The spatial conversion between cultivated land,unused land and land use type of construction land is relatively frequent.The change of cultivated land,unused land and garden land area is larger than that of forest land,construction land and grassland land area.(2)The contents of Cd,Cu,Hg and Ni in the surface soil were higher than those in Shandong Province,and the average content of Cu in Shandong Province was 2.25 times higher than that in Shandong province.Cr,Pb and Zn The average content is slightly higher than its background value.The average value of heavy metal content in deep soil is slightly higher than that in deep soil of Shandong Province,which indicates that the deep soil of Qixia City is also disturbed by human activities.Cu,Ni and Zn have very important physiological functions in plants,and three kinds of heavy metals have high accumulation in grassland,woodland,garden and cultivated land.The study area adopts intensive production mode,and three kinds of heavy metals are important for intensive The growth stability and yield of plant under the production mode are of great significance.While the accumulation of As,Cd,Cr,Hg and Pb in different species is small.The vertical cumulative statistical analysis of soil heavy metals under different land use patterns in different land types has a high vertical accumulation rate in the garden and construction land.Qixia City as the main producing areas of apple,in the orchard management process,for the use of chemical fertilizers and pesticides to increase the content of heavy metals in the soil,and the garden of the special biological characteristics of the plant,making the soil heavy metal infiltration effect is significant,and construction land is human Activities of the most influential areas,the human soil damage to the soil structure to promote the vertical migration of soil heavy metals.In the unused land and woodland,the vertical mobility of each element is low,and The results showed that the effects of different land use types on the vertical migration of heavy metals were as follows: construction land> farmland> cultivated land> grassland> forest land> unused land.The content of heavy metals in the whole soil is within the national environmental quality standard,which is conducive to ensuring the smooth progress of local agricultural activities.(3)To identity the potential sources of heavy metals in Qixia.The multivariate analysis results suggested that Cd,Pb,Zn,Ni,Hg and Cu in the soil were consistently from anthropogenic sources,while As and Cr were from natural sources with low concentrations.Cultivated land,garden land and construction land are affected by human activities,the waste produced by human production and life,and the soil and fertilizer in the process of agricultural production have an effect on the accumulation of heavy metals.In these three types of land use,Cd,Pb,Zn,Ni,Hg and Cu all showed a high accumulation.As and Cr in the different land use patterns did not appear cumulative phenomenon(4)The influence of different land use patterns on the distribution of heavy metals in soils has found that the strength of human activities directly determines the content of heavy metals in soil.The distribution of heavy metals in the soil showed that the land use was in the area> cultivated land> cultivated land> grassland> forest land> unused land.Based on the vertical distribution of heavy metals in soils under different land use types,Cu,Cd and Hg could be accumulated in different land use patterns.Cu,Zn and Ni are necessary as trace elements for plant growth and remain in the normal range.Combined with the theory of source and sink,the cultivated land,the construction land and the garden land are regarded as the "source type",which can promote the accumulation of heavy metals in the soil.The influence of human activities makes this part become the key area of heavy metal accumulation.The grassland,the woodland and the unused land as the "sink type",these areas are less affected by human activities,and at the same time have a certain self-purification ability,can effectively adsorb heavy metals in the soil elements(5)Based on the evaluation criteria,Qixia City is divided into clean area,priority protected area,safe use area,strict control area and risk restriction area,95.9% of the whole area is located in the area of Qixia City.The soil environmental quality of Qixia City is evaluated by single factor pollution index and comprehensive pollution index.Within a range of minor contamination,a few areas meet the risk limits.According to the single factor pollution index can be found,Cu and Hg pollution is relatively heavy,especially Hg pollution,but the overall slightly lower than the national environmental quality standards,within the controllable range.Combined with the comprehensive pollution index can be found,heavy metal pollution has a clear flaky distribution.