Eco-geochemical Assessment Of Grassland In West Jilin Province

Western Jilin Province is located in the transitional zone of Da Hinggan mountainsForest, Horqin prairie wetlands, and transitional Songliao plain ecosystems.The maingrassland types in this area are plain meadow steppe, plain meadow, and terraced hillssteppe grassland. The grassland in west Jilin Province is not only an importantecosystems and ecological barrier of Jilin Province, but also an important agriculturalproducing area. In recent years, due to the disturbence of human and the change ofnatural environment, grassland degradation in west Jilin Province is moreserious.Therefore, the comprehensive investigation of the distribution characteristics ofmineral nutrients and heavy elememts， the content property and the enrichmentcharacteristic of grass is of great significance.In this study, soil samples and grass samples were taken and analyzed to describe thegeochemistry characteristics, enrichment characteristics of soil mineral nutrients andthe characteristics of heavy metal elements form and elements in forage, and thestatistical correlation of elements. The grades of the soil fertility and the pollution ofheavy metal elements are also evaluated. Through research, we obtained the followingconclusions:1. The contents of Al2O3, TFe2O3, MgO, B, Mn, Co, Mo, Pb, Cu, Zn, As, Hg, Ni,Cr, Cd in the soil of west Jilin Province grassland are lower than soil the environmentalbackground value, Na2O, K2O contents are higher than the soil background value.Thecoefficient of variation of CaO, N, Cl contents are big，so the spatial differences CaO,N, Cl contents large.Geographically, nutrient elements have the trend decreasing fromthe north to the south.2. The result of correlation analysis and factor analysis showed that the main sourceof mineral nutrients such as Co, Cu,Zn, Mo, and Mn, and heavy metal elements suchas Cr, Ni, As, Pb, Hg,(Cu), and (Zn) in this area is contributed from parent rocks ofsoils. The contents of N, P, K2O, CaO and Cd in the soils are easily impacted by pedogenesis.The contents of B, MgO are greatly correlated with pH. Soil electricalconductivity is affected by Cl and Na2O contents.3. The ratio of element contents beween the surface soil and subsoil indicates that N,P, Cl, Na2O, and K2O are enriched in the surface soil, and the enrichment factor ofheavy elements suggested that they are enriched in the surface soil.4The contents of available Mn, available Mo, available Zn are of very low level, thecontent of available Cu is of moderate level, and the content of available B and availableFe are of very high level. Soil hydrolysis N, available P, available K, available Zn, andavailable B contents are affected by pH, electrical conductivity and soil organic carboncontent. The heavy elements As, Zn, Cr, Pb are mainly derived from soil, and Hg andCd occurred mainly in the mobile form, so the both potential ecological risks arerelatively higher than other heavy elements.5. Using analytic hierarchy process to evaluate the soil fertility levels in this area, theresults show that the soil fertility level of terraced hills steppe grassland is highest,followed by the soil in the plain meadow steppe grassland, which is graded at the secondlevel, and the soil in plain meadow grassland has the lowest fertility level. UsingNemerow index to assess heavy element pollution of grassland soil in this area, theresults show that the heavy element content in soils is mostly at a safe level, withexception of the soil around Chaganhua town, where the heavy elements in soils areslightly polluted by the relative enrichments of As, Cr, Hg, Pb, Ni, Zn concentrations.6.The content of As, B, Ni, Na, Ca, Cr, Mn, Fe, Co, Cd, Pb, F, P in grass is quitedifferent, Na and P contents in grass is remarkably correlated with the pH and organiccarbon content in soil, and other elements contents have poorly correlation with the pHand organic carbon content in soil. By the reference of feeded trace elementsrecommended by NRC, Zn, Cu, and P contents in grass are deficient, while Ni contentin grass is exceeded, and K, Mg, Ca, Mn, Co and Mo in grass can meet the needs forsheep growth and normal metabolism.In general, the level of the grassland soil fertility in the west Jilin Province is low.Theavailable content of mineral nutrients is of very low level. Although the level of heavyelement content is in the safety level, and the potential ecological risk of Hg, Cd is relatively higher than other heavy elements. Grass lacks Zn, Cu and P, and K, Mg, Ca,Mn, Co and Mo in it can meet the need of prairie animal growth.