村镇生活垃圾焚烧底渣农用的重金属污染风险评价

Health Risk Assessment of Heavy Metal Pollution of Agricultural Use of Municipal Solid Waste Incineration Bottom Ashes

随着生活垃圾焚烧处理方式的不断推广,生活垃圾焚烧底渣的处置也成为一个日益严峻的问题。为了明确生活垃圾底渣农用的可行性,于2014年在江苏常熟农业生态实验站进行了小白菜(Brassica rapa L.Chinensis Group.)盆栽试验,各施肥处理土壤中分别添加底渣的比例为0%、5%、10%、20%、50%、100%,以不施肥处理和单施底渣(10%)处理为对照。于小白菜收获时,取样分析小白菜产量、品质,以及小白菜和土壤中Cd、Cr、Cu、Ni、Pb、Zn含量,并采用内梅罗综合污染指数法和目标危害系数法评价了底渣农用的重金属污染风险。结果表明,施用适量的底渣可以有效增加小白菜产量,亦增加了小白菜中可溶性糖、维生素C和硝酸盐含量,并且硝酸盐含量未超过中国无公害蔬菜安全要求;小白菜地上部重金属含量和土壤重金属含量在不同处理中均随底渣施用比例的增加而增加,且底渣施用量超过12.2%时,土壤内梅罗综合污染指数大于1,土壤呈轻度重金属污染,底渣施用量超过15%时,小白菜地上部重金属Cr含量超过中国食物污染物的限量标准;小白菜单一重金属目标风险系数在不同处理中均小于1,而底渣用量大于或等于10.7%时小白菜重金属复合目标风险系数大于1,存在食用健康风险,健康风险以Pb、Cd为主,并且儿童更易遭受小白菜重金属危害。因此,在保证小白菜产量、品质和土壤安全下,底渣一次性安全施用比例不能超过10%。

As incineration is more widely chosen as one of the major treatments of municipal solid waste in China, the disposal ofmunicipal solid waste incineration bottom ashes （MSWIBA） has become an increasingly serious problem. In order to identify thefeasibility of agricultural use of MSWIBA a pot experiment in greenhouse was tested with a local pakchoi as material in Changshuagro-ecological experimental station, Jiangsu Province, China in 2014. The proportion of MSWIBA was 0%, 5%, 10%, 20%, 50%,100% in each fertilization treatment, with no fertilization application and single MSWIBA （10%） as control. Variations on yield andquality of pakchoi and the contents of Cd, Cr, Cu, Ni, Pb, Zn in aboveground pakchoi and soil were detected during the harvestseason. The Nemerow multi-factor index method and the target hazard quotient were used to evaluate the health risk assessment ofheavy metal pollution of agricultural use of MSWIBA. The results indicated that application of appropriate MSWIBA had greatlyincreased pakchoi yield and the contents of soluble sugar, vitamin C and nitrate, however, the nitrate concentration was below thenational pollution-free vegetable standard level. Both heavy metal contents of pakchoi aboveground part and heavy metal contents insoil had an increase tendency as the proportion of MSWIBA increased in different treatments. The Nemerow multi-factor index wasmore than 1 as the proportion of MSWIBA exceeded 12.2%, which suggesting the soil was slightly polluted, and the content of Crexceeded the national food contaminants standard limit as the proportion of MSWIBA exceeded 15%. The target hazard quotient（THQ） value of the single heavy metal in different treatments was lower than 1,while the total target hazard quotient （HI） value ofheavy metals was higher than 1 when the proportion of MSWIBA was over or equal to 10.7%, which indicated that consumption ofthe polluted vegetables would lead to potential health risk, especially for children, which mainly originated from Pb and Cd. So in thepremise of ensuring the safety of pakchoi yield, pakchoi quality and soil quality, one-off application ratio of MSWIBA was lowerthan 10%.