| With China’s emphasis on environmental protection,a large number of illegal factories were forced to shut down in the last century,resulting in a large number of venues with environmental risks.An arsenic plant in Hechi,Guangxi was built in 1990,discontinued in 1993,and during the course of production of arsenic,the site could be contaminated with soil.This paper to a legacy of arsenic factory pollution area as the research object,through field investigation,sampling analysis,assess the soil environmental quality of the site,using Hakanson ecological risk assessment methods and《Technical guidelines for risk assessment of contaminated sites》to evaluate ecological risk and health risk of heavy metals in the sites.Through indoor culture research several iron base materials for the main pollutants of the venue arsenic stabilization effect,the results for the further scientific governance provides the theoretical basis and repair contaminated sites.The results include:（1）The site investigation,according to the results of site soil by heavy metals As,Zn,Pb,Cd,Cu,different levels of pollution,the pollution degree of the As>Zn>Pb>Cd>Cu,the scope of the determination of heavy metals,respectively,As:2482.53～21273.28 mg/kg,Zn:383.86～4577.58 mg/kg,Pb:8.38～5091.92 mg/kg,Cd:0.13～16.71 mg/kg,Cu:23.24～604.16 mg/kg.The soil effective arsenic content varied greatly,between 1.89～554.32 mg/kg,and the soil As leaching concentration（nitric acid method）was 0.04～8.74 mg/L,（horizontal oscillation method）is 0.09～14.90 mg/L.P1 and P4,P12,P13,P14,P18 point As leaching of soil concentrations higher than 5 mg/L,the maximum allowable concentration of the《Identification standards for hazardous waste》,these points are mainly distributed in carrying the goods into the factory and smelting furnace,most of the water extract of the soil As concentration is higher than《standard of sewage comprehensive discharge》As:maximum allowable emission concentration of 0.5 mg/kg,As that the contaminated sites with high risk.（2）Soil pH in the site:3.33～8.18;organic matter content:2.42～23.01 g/kg;urease activity:0.04～0.45 mg/g;hydrogen peroxidase activity:2.56～10.14 ml/g;dehydrogenase activity:0.00-0.92 ml/（g·24h）.The soil microbial activity and soil enzyme activity were low.（3）Soil heavy metal potential ecological risk assessment results show that the pollution of ground soil of a variety of potential ecological harm of heavy metals index is greater than 600,the pollution there exists strong potential ecological risk.The potential ecological hazard index of each heavy metal is As:1210.99～11415.03;Zn:5.08～60.55;Pb:1.75～1060.82;Cd:14.04～1877.34;Cu:4.18～108.66.As to the soil of the whole site has a strong ecological hazard,Pb and Cd have a strong ecological harm to the soil in some areas of the site.Zn and Cu have a slight ecological harm to the soil in some areas of the site.The results of health risk assessment of soil heavy metals in the site showed that the carcinogenic risk indexes of each heavy metal were As:1.20 x 10-2;Cd:3.89 x 10-7;The non-carcinogenic hazards of heavy metals are As:617.41;Cd:0.40;Cu:0.04;Zn:0.05;《Technical guidelines for risk assessment of contaminated sites》regulation of carcinogenic risk index and non cancer hazard acceptable level for 10-6 and 1,As far more than acceptable level,to the area of people to have high health risks.（4）Indoor culture experiments show that adding material with a quality ratio of 5%of chelate iron + Ca（OH）2（3:1）and chelate iron + CaO（3:1）on soil arsenic has good stability,stabilization rate has reached more than 96%,after stabilizing soil water extraction As the content of sulfuric acid and nitric acid leaching As was reduced by 96.68%,96.64%and 96.67%and 96.68%respectively,and the soil pH and soil water leaching solution of pH to maintain between 7 and 8. |
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