摘要
以西南地区广泛分布的紫色土-灰棕紫泥为对象,探讨了硫化物种类(S、Na_2S、FeS、Na_2S_2O_3和DTCR(二硫代氨基甲酸盐))、用量对不同水平汞污染土壤的稳定化效果。结果表明5种硫化物对土壤汞均具有显著的稳定化效果。固定S:Hg摩尔比为1:1条件下,在1.5～250 mg·kg^(-1)汞污染土壤中,几种硫化物稳定效率相对大小顺序:DTCR>Na_2S>Na_2S_2O_3>S>FeS。Na_2S和DTCR在高浓度汞污染土壤中均表现较高的稳定化效果,在不同汞污染浓度下均能在3d内使土壤浸出汞浓度满足美国固体废弃物毒性浸出程序(TCLP)浸出标准要求(0.2 mg·L^(-1)),Na_2S_2O_3稳定效果相对较差,对250 mg·kg^(-1)的汞污染土壤,稳定化处理时间需要15d才能达到浸出标准要求,当汞污染浓度≥150 mg·kg^(-1)时,S和FeS不能满足浸出标准要求。固定汞污染浓度为150 mg·kg^(-1)稳定化效果取决于硫化物的用量,其中,仍然以DTCR效果最好,S:Hg=1稳定化处理3 d时即可达汞浸出标准。Na_2S和Na_2S_2O_3则均需要在较高的浓度下才能实现汞的稳定化,但是过高的用量会导致土壤中HgS再次溶解,两者的最佳施用量为S:Hg=5。元素S和FeS则需要以S:Hg>5稳定化处理7 d以上才能达到浸出标准要求。土壤中汞的浸出活性与其赋存形态有关,交换态(Exc-Hg)和碳酸盐结合态汞(Carb-Hg)与土壤浸出汞浓度呈显著正相关,高效稳定剂显著促进了汞向有机质结合态(OM-Hg)和残渣态(Res-Hg)转化。硫化物稳定化处理9个月内土壤中浸出汞浓度始终维持在极低水平,满足持续稳定化要求。
The effects of sulfide species （S, Na2S, FeS, Na2S2O3 and DTCR （sodium dithiocarbamate）） and concentrations on the stabilization mercury （Hg） were discussed in the gray-brown purple soil, which is widely distributed in the Southwest China. The results showed that the five sulfides had significant stabilization effect on Hg in soil. When the elemental S：Hg ratio is 1：1, the stabilizing efficiencies followed the order of DTCR〉Na2S〉Na2S2O3〉S〉FeS at Hg concentration ranged from 1.5 to 250？mg·kg-1 in soil. The Hg concentrations？in the leachate can reach to a very low level in 3 days after Na2S and DTCR treated, even under the highest Hg contaminated condition. Na2S2O3 showed lower passivation effect on soil Hg, it would take 15 days for the leaching Hg concentration to meet the stabilization criteria at soil Hg concentration of 250 mg·kg-1. S and FeS treatments cannot match the stabilization criteria when soil Hg≥150 mg·kg-1. At the constant soil Hg concentration of 150 mg·kg-1, the stabilization effect depends on the amount of sulfides, where DTCR still shows the best performances for the stabilization of soil Hg. Higher S：Hg ratios are needed to reach leaching standard both for Na2S and Na2S2O3 treatments, whereas the further higher dosage will cause the re-dissolution of HgS, and their optimum application rate is 5. It would take more than 7 days to meet the leaching standard both for S and FeS treatments with S：Hg ratio higher than 5. The soil Hg mobility is related to its speciation, and a significant positive correlation exists between exchangeable Hg（Exc-Hg）, carbonate bound Hg （Carb-Hg） and the concentration of soil leaching Hg. The high efficiency stabilizer significantly promoted the transformation of exogenous Hg to organic affinity Hg（OM-Hg） and residual Hg（Res-Hg）. The concentration Hg in the soil leachate was kept at a very low level within 9 months after soil treated by sulfides, indicating sulfides treatment can meet the requirements of continuous stabilization.
出处
《环境工程学报》
CAS
CSCD
北大核心
2018年第3期893-903,共11页
Chinese Journal of Environmental Engineering
基金
重庆市科学技术委员会重点研发计划项目(cstc2017shms-zdyf0036)
国家重点基础研究发展计划(973)项目(2013CB430003-04)
关键词
紫色土
汞污染
硫化物
浸出浓度
稳定效率
purple soil
mercury pollution
sulfide
leaching concentration
stabilizing efficiency
