Soil Copper Enrichment Mechanism And Land Use Zoning In Linshui County,Guang’an City,Sichuan Province

Copper is not only an indispensable nutrient element for life,but also a very important heavy metal element.At present,people pay more attention to soil Cu heavy metal pollution,but ignore the value of Cu as a nutrient element.In this paper,Xicao,Linshui County,Guang’an City,Sichuan Province is selected as the research area.The systematic collection of area soil and bulk crop seed-root soil samples has ascertained the geochemical characteristics of soil Cu in the study area and its controlling factors.The migration and transformation between bulk crop seeds and root soil and their main controlling factors,a prediction model for the Cu content of bulk crop seeds was established,and the area soil geochemical survey data was used to predict the Cu content of bulk crop seeds,and the ecology of Cu was comprehensively considered.For risk and nutritional value,the Cu-rich arable land and Cu-rich crop planting areas were divided into the study area.The main knowledge gained in the thesis is as follows:1.The average value of Cu element content in the soil in the study area is26.27 mg/kg.According to the evaluation results of the"Land Quality Geochemical Evaluation Specification（DZ/T 0295-2016）",the first-class land area in the study area is 135.2km²,accounting for 18.3%;the second-class land area is 333.0 km²,accounting for 45.1%.The soil in the Huaying mountainous area is rich in Cu,and the soil near the towns on the Yulin River is relatively deficient in Cu.2.The soil-forming parent material has the greatest impact on the soil Cu content,and the carbonaceous shale soil-forming parent material has a higher Cu content in the soil.There is a negative correlation between Cu and Si O₂.Organic matter and iron-manganese oxide have a positive correlation with Cu due to their strong adsorption capacity.3.The characteristics of Cu content,enrichment capacity and influencing factors of corn seeds,rice seeds and sweet potatoes in the study area were ascertained.The order of Cu enrichment capacity of the three crops is:sweet potato>corn>rice.The common main controlling factors of the Cu enrichment capacity of rice and corn are soil TFe₂O₃ and organic matter.Based on this,a prediction model of Cu content in rice seed and corn seed was established.Using area soil geochemical survey data to predict the copper-rich arable land,the copper-rich corn arable land is 24.92km²,accounting for 3.37%of the entire study area,mainly distributed near Huaying Township,and the planting area has a certain scale.The Cu enrichment degree of rice seeds is low,and the conditions for large-scale planting of Cu-rich rice are not available.4.Using geo-accumulation index method and potential ecological risk index method to evaluate the degree of soil heavy metal pollution and ecological risk in the study area,the results show that the degree of soil heavy metal pollution in the study area is extremely low,and there is only slight pollution in some areas.Heavy metal pollution exists in the Tianyi Valley Scenic Spot and the suburban transportation hub of Linshui County in the study area.Human factors such as vehicle exhaust and factory pollution may be the main sources of pollution.