硫酸污染土壤原位搅拌中和修复案例分析

文章主要研究了某硫酸污染土壤原位搅拌中和处置工程。通过地球物理探测和精细化调查确定了填埋场内的防渗膜埋深和土壤分区污染程度。按污染空间分布划分为pH 3~4、4~5、5~6共3个浓度区,针对3个浓度区分别采用质量比为4%、2%、1%的氢氧化钙药剂,将土壤pH调节成6~9。考察了搅拌桩原位中和过程中土壤孔隙率、含水量、药剂添加量、地层土压力对修复效果的影响,确定氢氧化钙浆液的浓度配比和注浆压力。修复结果表明借助于科学的氢氧化钙添加量和工程机械混合措施能快速有效地修复酸化地块土壤。

基于16S rRNA基因序列分析受砷和硫酸盐污染的土壤细菌多样性(英文)

为了了解普通耕地土壤(Nor-1)和受砷及硫酸盐污染土壤(Sul-1)中的细菌组成和多样性差异,对2个不同土壤样品直接提取总DNA,通过PCR扩增16S rRNA基因并建立文库,对文库克隆进行核糖体DNA扩增片段酶切分析(ARDRA)和测序,构建系统进化树。从Nor-1土壤样品中测序获得23个16S rRNA基因序列,分析序列系统发育关系表明,共包含Acidobacteria(12.3%,8/65)、Actinobacteria(3.1%,2/65)、Firmicutes(21.5%,14/65)、Nitrospira(3.1%,2/65)和Proteobacteria(60%,39/65)等5个不同细菌门。而从Sul-1土壤样品中测序获得19个16S rRNA基因序列,分析序列系统发育关系表明,共包含Firmicutes(29.5%,13/44)和Proteobacteria(70.5%,31/44)等2个不同细菌门。结果表明,受高浓度的砷和硫酸盐的影响,Sul-1土壤中细菌群落结构相较于普通耕地土壤(Nor-1)发生了明显的改变,多样性明显下降,但有大量具有较强的污染物降解能力的不动杆菌(Acinetobacter)相关序列在Sul-1土壤细菌群落中被发现。

砷和硫酸盐污染土壤的细菌多样性

硫酸广泛用于化工、轻工业、纺织、冶金、石化和制药工业，是基本的化工原料。生产硫酸的主要原料是黄铁矿，其过程中所排放的砷、氟化物和重金属对环境造成污染，对人的健康造成严重危害‘钔，因此治理环境中砷与硫酸的污染迫在眉睫。由于微生物可以通过还原、氧化和甲基化将砷转化为无害物质，因而是治理砷和硫酸污染的最有效手段，研究砷和硫酸污染土壤的微生物多样性及砷无害化转化的基因具有重要的意义。

Remediation of in-situ Leach Mining Contaminated Soil by Amendment-plant Synergism

This study aimed to remediate in-situ leach mining contaminated soil by amendment-plant synergism. The results showed that plant species exhibited ex-tremely significant effects on the concentration of nitrate nitrogen; to be specific, the concentration of nitrate nitrogen in soil planted with wheat was reduced from 692.19 mg/kg to lower than 100 mg/kg; when the mass ratio of amendment to soil reached 3：50 and the amendment particle size was 1-2 mm, the concentration of nitrate ni-trogen in soil planted with wheat was reduced to 43 mg/kg. The amendment type exhibited extremely significant effects on the concentration of ammonium nitrogen; to be specific, when the mass ratio of amendment to soil reached 10：50, the concen-tration of ammonium nitrogen in soil added with 2-3 mm zeolite was reduced from 23 593.75 to 3 300 mg/kg on day 15. Amendments and plants mainly exhibited desorption performance for sulfate radical in soil, and the amendment type extreme-ly significantly affected the concentration of sulfate radical; to be specific, the con-centration of sulfate radical in soil added with limestone increased from 370 mg/kg to 900 mg/kg on day 7.

Dechlorination of DDT and DDE by Dithionite in Dicofol Type DDTs-Contaminated Soil

Dicofol type DDTs-contamination is of great concern as environmental organochlorine pollutant. In the present study, dechlorination time-course ofp,p＇-DDT and p,p＇-DDE in dithionite treated waterlogged DDTs-contaminated soil, non-contaminated soil solution and citrate-bicarbonate buffer （0, 50, 100 mmol L^-1, dithionite） for 72 hrs was investigated based on residual amount of p,p＇-DDTs （p,p＇-DDT and p,p＇-DDE） analyzed by GC-ECD. The metabolites ofp,p＇-DDTs in dithionite treated non-contaminated soil solution, and citrate-bicarbonate buffer were detected by GC-MSD. The dechlorination time-course of p,p＇-DDT and p,p＇-DDE exhibited rapid dechlorination at the first 3.0 hrs, slow dechlorination after 3.0 hrs. For 50 mmol L^-1 dithionite treatments, the dechlorination ratios ofp,p＇-DDT and p,p＇-DDE were 36.42% and 35.08% respectively at 3.0 hrs. For 100 mmol L^-1 dithionite treatments, the dechlorination ratios of p,p＇-DDT and p,p＇-DDE were 58.62% and 57.39% respectively at 3.0 hrs in DDTs-contaminated soils. Significant differences of dechlorination ratio were also confirmed in dependence on dithionite concentrations, reaction systems and the chemical structure of DDTs. The dechlorination ratio ofp,p＇-DDT/DDE increased with the increasing of dithionite concentrations irrespective of reaction systems. Dithionite-induced dechlorination ratio of p,p＇-DDT was higher than that of p,p＇-DDE. The p,p＇-DDD （1,1-dichloro-2,2-bis（4-chlorophenyl）-ethane）, p,p＇-DDE and p,p＇-DDMU （1-chloro-2,2-bis（4-chloropheny）-ethylene） were identified to be metabolites ofp,p＇-DDT in buffer and non-contaminated soil solution, however, no metabolites ofp,p＇-DDE treated by dithionite were detected. The possible pathways explaining the dechlorination of p,p＇-DDT and p,p＇-DDE by dithionite were also proposed. Dithionite could be used to develop an effective and fast remediation option for DDTs-contaminated soils and sediments.

Comparison of Persulfate Activation and Fenton Reaction in Remediating an Organophosphorus Pesticides-Polluted Soil

Organophosphorus pesticides （OPs） are one of the most regular pollutants and frequently detected in the contaminated sites, so developing an efficient method for the treatment of OPs is highly required. The aim of the present study was to compare the effectiveness of persulfate （PS） activation and Fenton reaction in remediating the soil polluted with OPs. The polluted soil used in this study was sampled from an abandoned insecticide factory in Nantong, Jiangsu Province of China, mainly containing chloropyrifos （CP） and 4-bromo-2-chlorophenol （BCP, the raw material of profenofos） with total concentration of about 30 000 mg kg- 1. The results showed that both BCP and CP were efficiently degraded by base activation of PS, and increasing the ratio of NaOH/PS enhanced CP degradation, but slightly decreased BCP degradation. The greatest degradation rates for CP and BCP were 92% and 97%, respectively, with 7.0 tool L-1 NaOH and 0.21 tool L-1 PS and a soil-to-liquid ratio of 1：1. Furthermore, ferrous iron activation of PS also degraded BCP efficiently, but only 60% of CP was degraded under the same reaction conditions. These results indicated that base activation of PS was more feasible than Fe2＋ activation and Fenton reaction in remediating the soil polluted with OPs. The high degradation rate for CP may be linked to the initial hydrolyzation of CP by base to 3,5,6-trichloro-2-pyridinol, which can be further rapidly degraded by free radicals generated from base activation of PS.