铁氧化物复合功能材料在砷污染农田修复中的应用

The application of iron oxide composite restoration functional materials in arsenic polluted farmland

以铁氧化物以及黏土矿物为主要成分的复合药剂为原位钝化功能材料,选用土壤调理剂、生物质炭及酵素为土壤盐碱化改善功能材料,对目标地块进行修复及改良。修复后对项目605亩农田分5个修复区域进行修复,最后采集共计47个土壤样品检测数据进行分析,发现经原位钝化修复后本项目区域表层(0~30 cm)土壤中有效态砷含量从修复前均值0.458 mg/kg降低至修复后均值0.025 mg/kg,平均降幅达到92.54%。采集共计47个水稻籽粒样品检测数据进行分析,结果表明谷物砷含量降低到《食品安全国家标准食品中污染物限量》(GB 2762—2012)限值0.5 mg/kg以下,从修复前均已接近0.5 mg/kg的状态降低为均值在0.232 mg/kg,降低了砷的生物可利用性降低,且有效降低植物对重金属的吸收剂重金属的生态毒性。土壤pH值从修复前8.42的降到修复后的7.42,土壤盐碱化程度从弱碱性降至中性。土壤有机质含量提升到20 g/kg以上,达到全国第二次土壤普查养分分级标准第三级水平要求,表层土壤有机质均值从8.44 g/kg提高到32.39 g/kg,提高了2.84倍。修复区域大部分点位EC降低为2000μs/cm,均值为1616.4μs/cm,属于中盐渍化水平,达到此标准以后作物出苗率将增加到50%以上。修复区域土壤耕作层的主要肥力指标碱解氮、有效磷、速效钾平均含量分别提升到54.25 mg/mg、28.3 mg/mg、268.8 mg/mg,土壤肥力达到较高标准,改良效果显著。

According to the survey,the arsenic pollution was ranked third in eight kinds of heavy metal elements,behind cadmium and nickel. After entering the farmland soil,heavy metal can affect the activity of soil and microbes,resulting in a decline in soil fertility and crop production,and a risk to human health. There’s a large number of high salinity farmland in the northwest of China,non-metallic nature makes that the arsenic(Ⅴ)and arsenic acid radical salt arsenite(Ⅲ)the two main form in the nature,the shape of the bigger toxicity of arsenic concentration increased with the increase of pH,so the toxicity of arsenic in saline-alkali land is bigger. The research aimed at the high salinity farmland soil of arsenic pollution repair technology shows that,in situ passivating repair technology can be suitable for farming and repair of production requirements well. This project has chosen the iron oxide and clay minerals content as the main component of composite reagents for in situ passivating functional materials,choosing soil conditioner,biomass carbon and enzyme improve functional materials for soil salinization,repair and improvement of target block. The restoration aera is 403 535 m2,which is divided to 5 areas,and finally took a total of 47 soil samples for testing and data analyzing.The results showed tha,t the arsenic content of the surface(0 ~ 30 cm)soil is reducing from average 0.458 mg/kg before repair to average 0.025 mg/kg after repair,fell to 92.54% on average. A total of 47 rice grain samples tested data is analyzed,the results show that grain arsenic content is reduced to the National Food Safety Standards of f Food Contaminants in Limited(GB 2762-2012),under the limit of 0.5 mg/kg,which has been reduced from average 0.5 mg/kg to 0.232 mg/kg.The biological availability of arsenic is reduced,and the uptaking of heavy metals by plants by ecological toxicity of heavy metals was effectively reduced. The pH of the soil rhas educed from 8.42 before repair to 7.42 after repair,the degree of soil salinity from weak alkaline dropped to neutral. Soil organic matter content up to more than 20 g/kg,reached the second soil census nutrient classification standard of the third level requirements,the mean of surface soil organic matter increased from 8.44 g/kg to 32.39 g/kg,increased 2.84 times. The EC of most points of the epair area have reduced to 2 000 μs/cm,the averages is 1 616.4 μs/cm,belongs to the middle level of salinization,reach the standard of crop emergence rate will increase to more than 50%. The main fertility index of soil magnetism,the average content of alkaline hydrolysis N,available P,available K in the repair area have risinged up to 54.25 mg/mg,28.3 mg/mg,268.8 mg/mg,respectively. The fertility of the soil has reached to a high standard,the improvement effect is remarkable.