| Soil heavy metal pollution as an important component of the soil pollution, it is a hot issue forthe world. Soil heavy metal pollution is a serious threat on crop growth, human health and ecological safety, so we must pay enough attention to protect soil.Xi'an Lintong district is located in the middle of Guanzhong Plain of Shaanxi Province, itis a famous international tourist resort destination, and also aplace for agricultural products and the main supply tourism commodities.It has a theoretical value and practical value tomonitor and evaluate soil pollution in Lintongdistrict. This study selected five kinds of land use types in Lintong district, namely sweet potato field, wheat field, actinidia field,pomegranate field, abandoned landassoil samples. Soil physical and chemical properties, constant elements and heavy metals content, soil prime element in profiledistribution characteristics, and heavy metals potential pollutionrisk of different land using types were analysed. Finally, the relationship between the soil heavy elements andsoil physical and chemical properties,heavy metal elements possible sources were discussed. According to pollution status inLintong, somecorresponding countermeasures and suggestions were put forward. The main conclusions are as follows:(1) The pH values offiveland use types in Lintong were alkaline soil, the pH values of soil ranged from 7.58-8.27, thepH value of sweet potato fieldis the minimum, the pH value of the abandoned land is the maximum. The average electrical conductivity of five kinds of land use type soil in Lintong ranged from 147.37-344.41uS/cm. According to the order from big to small, the averagesoil electrical conductivity were followed by sweet potato field> actinidia field>wheat field>abandoned land>pomegranate field. The average magneticsusceptibility of five land use types soil in Lintong varied between 66.07-121.1 l×10-8 m3/kg. According to the order, the average magnetic susceptibility valuefrom big to small were followed by pomegranatefield>wheat field>abandoned land> actinidia field>sweet potatoes field. The particle size distribution of five land use types soil in Lintong was dominated by silt which content varied between 58.27-70.27%.Clay content was the second which varied between 16.08-25.89%. Sandcontent was the least whichvaried between 3.98-25.65%.(2) The average soil concentration ofFe,CA, K, Mg, Na, Al, Si in Lintong varied between 5.28-6.36%,2.36?3.23%,1.55?1.69%,1.81?2.01%,1.58?2.33%,7.26?8.18%, 33.41-34.93%. Among the five types of agriculturalland, wheat fieldhave three elements which content were higher than the rest of four land use types. Sweet potato field have four elements which content were lower than other land use types.(3) The averagesoil heavy metals contentof As,Co,Cr,Cu,Ni,Pb,Mn, Zn in Lintong varied between 11.53?16.05mg/kg,17.46?25.12mg/kg,29.35?145.30mg/kg, 16.92?22.61 mg/kg,30.09?38.37mg/kg,12.03?21.64mg/kg,484.34?599.78mg/kg, 29.49?39.90mg/kg. Among the five types of agriculturalland, pomegranate field have four heavy metal elements which content were higher than the rest of four land use types. Sweet potato field also have four heavy metal elements which content were higher than the rest of four land use types.(4) Based on the Shaanxi Province soil element background value, pomegranate fieldsoil werepolluted by As, Cu, Co, Cr, Ni, Mn. Wheat field and abandoned landsoil werepolluted by As, Cu, Co, Cr, Ni. Actinidia field, sweet potato fieldsoil werepolluted by As, Co, Cr, Ni.The result of Nemerow comprehensive pollution index and potential ecological risk index indicate five land use types soilbelonging light pollution level and low ecological harm degree. Based on the limitation values of national soil quality standard, five land use types of soil in Lintong were at an uncontaminated level.(5) Soil heavy metal elements of five land use types in Lintong had significant differences in enrichment depth, and showed multilayer enrichment characteristics.Heavy metals not only accumulated in the surface ofsoil, but also accumulated in thedeeper soil layers of l-2m. Heavy metal ofCo, Cr, Zn were mainly accumulated 0?0.6m soil layer. Heavy metal ofAs, Cu, Ni, Pb, Mn were mainly concentrated in the 1.1?1.7 depth soil.(6) As, Co, Cr, Ni contents offive land use types inLintong were higher than Shaanxi soil element background value. On the one hand, the reason is due to natural sources. On the other hand, the reason has a close relationship with all kinds of human activities. Agricultural production and transportation factors were mainly reasons for soil heavy metal pollution of anthropogenic sources. Combined the condition ofsoil heavy metal pollution in Lintong, this paper argues that security rules and comprehensive management ideasshould be taken toprevent soil heavy metal pollution. |
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