A Study On Soil Heavy Metal Environmental Capacity Characteristic And Pollutional Control Countermeasure In Wenjiang District Of Chengdu

Soil is one of the natural media most frequently contacted in process of production and human's life,it is also maintain close ties with human's health.In recent years,the content of heavy metals in soil has become a key factor to change the patterns of land use for people with the outbreak of soil contamination incidents,soil contamination can even determins the values of land.This paper mainly explores the pollution level of heavy metal,distribution characteristics and environmental capacity of mercury,arsenic,lead,partition and total chromium of soil in seven different land-use types in Wenjiang district,and puts forward pollution control countermeasures for this situation targeted.After setting up soil sampling points with grid method,soil samples in different land-use types was collected and soil heavy metal concentration was measured.This paper take risk screening values of “Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land(GB15618-2018)" and "Soil Environmental Quality Risk Control Standard for Soil Contamination of Development Land(GB36600-2018)" as the limits of soil heavy metals concentration to evaluate the status of soil contamination in seven land-use types.The environmental capacity of five kinds of soil pollution in different land-use types were calculated with soil capacity model,and studies the characteristics of environmental capacity in Wenjiang district,puts forward soil contamination control countermeasures for this situation targeted.The main results as follows:(1)Pollutant concentration and its evaluation: Mercury concentration in soil of seven land-use types in Wenjiang has not exceed the corresponding standards.Mercury concentration in soil of seven land-use types ranged from 0.027 mg/kg to 0.458 mg/kg.Industrial land has the highest mercury concentration.The arsenic concentration in soil of different land-use types ranged from 19.8 mg/kg to 31.8 mg/kg,among which the arsenic concentration in soils of industrial land is the highest,there are 6 of 7 land-use types arsenic concentration have below the corresponding standards,while the arsenic concentration in soil of urban development land was 29.7 mg/kg,which exceeded the corresponding standard(20 mg/kg)of this type of land,and the lead concentration in soils of all land types have not exceed the national limit.The concentration of lead in soil is between 27.1 mg/kg and 43.4 mg/kg.The highest concentration of lead in soil is vegetable planting land.The total chromium concentration in the soil of the seven land types have not exceed thecorresponding standard limit.The total chromium content in the soil has between 76.2mg/kg and 57.2 mg/kg.The vegetable planting land is the land type with the highest total chromium concentration in the soil.Soil cadmium was not detected in all seven land types,which indicated that soil cadmium concentration is lower than the minimum detection limit of 0.1 mg/kg.All land types had safe environmental quality of cadmium.(2)Environmental capacity: The environmental capacity of soil mercury,arsenic,lead and total chromium in different land types ranges from 0.22-20.07 t/km2;arsenic:-5.14t-18.66 t/km2;lead: 55.60-408.05 t/km2;total chromium: 64.395-286.624 t/km2.According to the total environmental capacity of seven types of land,the land-use types with the largest total environmental capacity of soil mercury,arsenic,lead and total chromium are seedling and flower planting land;their values are mercury: 2432.22t;arsenic: 941.61t;lead:4949498.26t;total chromium: 34563.28 t.In addition,the lowest total environmental capacity of soil mercury was vegetable planting land with a value of 6.72 t.The lowest total environmental capacity of soil arsenic is urban development land,which is-213.2t(no capacity).The smallest total environmental capacity of soil lead and total chromium is river conservation forest land.The total environmental capacity is lead: 403.46 T and total chromium: 284.59 t,respectively.By predicting the trend of soil dynamic capacity in the next five,ten and twenty years,it was found that the environmental capacity of pollutants increased slowly.(3)The high concentration of arsenic in urban development land may be due to the application of calcium phosphate,ammonium phosphate and other fertilizers in the process of urban development land development,while the excessive application of chemical fertilizers with arsenic residues will lead to the increase of arsenic concentration in soil.It is suggested that urban managers carry out follow-up risk assessment of arsenic contamination in soil and cut off exposure routes to reduce the risk of health damage through isolation measures such as ground hardening during land use.