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土壤中二苯砷酸的结合机制和生物及化学修复研究
朱濛1,2
学位类型博士
导师骆永明 研究员
2017-05-23
学位授予单位中国科学院大学
学位授予地点北京
关键词二苯砷酸 土壤 高效液相色谱-串联质谱法 结合机制 生物刺激修复 芬顿氧化修复
其他摘要
        二苯砷酸(Diphenylarsenic acid,DPAA)是含砷化学武器经水解和氧化后生成的一种新型环境污染物。近年来,DPAA造成的局部地区土壤和地下水砷污染问题逐渐引起国际社会的高度关注。为深入了解DPAA在土壤及其组分中的吸附特性和微观结合机制,并探索受其污染土壤的生物和化学修复技术,本论文开展了以下研究工作,并取得了初步进展。建立了适用于我国不同类型土壤中DPAA和苯砷酸(PAA)的分析方法。研究了海岸带土壤对DPAA的吸附特性,考察了盐度对DPAA吸附的影响及土壤组分对DPAA吸附的贡献,同时通过微观技术手段揭示了DPAA在土壤中的结合机制。明确了DPAA在土壤矿质胶体和铁矿物中的结合形态及其微观机制。详细研究了外加乳酸钠和硫酸钠的生物刺激法对淹水土壤中DPAA的去除效果,并探讨了硫酸盐还原和铁还原对DPAA固-液分配和转化的影响及其作用机制。同时,明确了(类)芬顿氧化对土壤中DPAA的去除效果和降解路径。上述研究结果可为DPAA在土壤-水系统中环境行为的研究和环境风险的评估提供了方法学及新的科学依据,为DPAA污染土壤的修复提供了新的技术途径。
本论文的主要研究结果如下:
(1)建立并优化了土壤中DPAA和PAA的分析方法,以 0.1 mol/L Na2HPO4作为提取剂,采用高效液相色谱-串联质谱仪(HPLC-MS/MS)作为检测器。本方法对DPAA和PAA的回收率分别为73.1%~99.0%和76.7%~109.1%,基质效应分别为107%~115%和102%~107%,仪器检出限分别为0.01和1.00 µg/L,方法检出限分别为2.52~3.42 µg/kg和0.23~0.33 mg/kg,准确度分别为3.0%~5.5%和2.4%~7.0%,日内和日间相对标准偏差(RSD)均小于5.0%,满足土壤中DPAA和PAA定量分析的要求。
(2)采用批试验和扩展X射线吸收精细结构光谱(EXAFS)技术研究了DPAA在11种海岸带土壤和2种非海岸带土壤(江西鹰潭红壤和水稻土)中的吸附特性及微观结合机制。结果表明:铁铝氧化物含量高的酸性硫酸盐土、水稻土、火山灰土、砖红壤和红壤较铁铝氧化物含量低的棕壤、潮土和黑土对DPAA的吸附能力更强,吸附等温线均可用Freundilich方程很好地描述。DPAA的吸附常数Kf值整体上表现为随盐度增加而增加。非晶质氧化物在土壤吸附DPAA过程中发挥了最为重要的作用。DPAA在土壤中的吸附机制为:在铁氧化物上生成内圈层双齿双核和单齿单核络合物,As-Fe键的原子间距分别为3.34和3.66 Å。
(3)采用连续分级提取法(SEP)和EXAFS技术研究了DPAA在土壤矿质胶体中的结合形态及其微观机制。结果显示,土壤矿质胶体中DPAA主要是以专性吸附态和氧化物结合态(45.1%~88.7%)存在,DPAA在土壤矿质胶体中的吸附机制为:在铁氧化物表面及嵌入铁氧化物颗粒内部发生配位交换作用,生成内圈层双齿双核络合物,As-Fe键的原子间距为3.18~3.25 Å。
(4)通过吸附动力学、SEP、傅里叶变换-红外吸收光谱(FTIR)和EXAFS技术研究了铁矿物对DPAA的吸附能力和微观吸附机制。结果表明:铁矿物对DPAA的吸附能力表现为:水铁矿≈赤铁矿>针铁矿>磁铁物>菱铁矿,DPAA在针铁矿、赤铁矿和菱铁矿上同时生成了内圈层双齿双核和外圈层络合物,而在水铁矿和磁铁矿上主要生成内圈层双齿双核络合物,同时伴有少量外圈层络合物。As-Fe键的原子间距为3.19~3.33 Å。
(5)通过8周的室内模拟试验研究了添加乳酸钠和硫酸钠的生物刺激法对黑土中DPAA的去除效果及机理。结果显示:外加碳、硫体系存在明显的DPAA释放现象,DPAA在培养初期(0~4周)和培养后期(4~8周)的释放分别与乳酸钠和铁还原有关。硫酸盐还原对DPAA的转化起着重要作用,释放到液相中的DPAA耦合硫酸盐还原,促进了DPAA硫化。
(6)通过8周的室内模拟试验研究了添加乳酸钠和硫酸钠的生物刺激法对红壤中DPAA的去除效果及机理。结果表明:外加碳、硫体系DPAA的释放在培养初期和培养后期分别与乳酸钠和铁还原有关。PAA和二苯基硫代砷酸(DPTAA)是外加碳、硫体系DPAA的主要转化产物,且DPAA先释放到液相,后发生脱苯环或硫化反应。
(7)通过室内模拟试验研究了(类)芬顿氧化对DPAA的去除效果、影响因素及降解路径。结果显示:对红壤和黑土分别采用类芬顿和芬顿氧化法,在H2O2初始投加浓度为1.0 mol/L,含铁催化剂初始投加浓度为0.25 mol/L,土水比1:3的条件下反应1 h,可获得较高的DPAA去除率(>65%)。在(类)芬顿氧化过程中,DPAA一方面逐步脱苯环并部分降解为无机砷,另一方面与高活性•OH反应生成羟基化二苯砷酸。
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    Diphenylarsinic acid (DPAA) is an emerging environmental contaminant derived from hydrolysis and oxidation of arsenic related chemical weapons. The compound has caused soil and groundwater pollution and has aroused widespread concerns and worries in the international community recently. The purpose of this study is to deep understand the characteristics and mechanisms of DPAA adsorption onto the whole soil and its components, and to explore the biological and chemical remediation techniques to remove DPAA from contaminated soils. The sutiable extraction procedure and HPLC-MS/MS method were developed for the determination of DPAA and phenylarsonic (PAA) in different types of soils in China. The characteristics of DPAA adsorption onto different types of coastal soils were investigated in order to clear the effect of salinity and the contribution of soil components to DPAA adsorption. A microscopic technique was employed to elucidate the molecular binding mechanism of DPAA in the soil. The speciation and adsorption mechanisms of DPAA in various clay mineral fractions in the soils and different iron minerals were studied. Soil incubation experiments were carried out to examine the transformation of DPAA in the flooded soils with the addition of sulfate and sodium lactate, and to elucidate the impact of sulfate and iron reduction on the solid-solution partitioning and transformation of DPAA. Degradation efficiencies and pathway of DPAA in soils by Fenton and Fenton-like reactions were also investigated. These results could provide reliable analytical methodology and new scientific evidences for studies of environmental fate and risk assessment of DPAA in the soil-water system and offer new technical approaches for the remediation of DPAA contaminated soils.
Results from this study are summarized as follows:
(1) The analytical method was deveploped and optimized for the simultaneous determination of DPAA and PAA in soil samples. The DPAA and PAA in soils were extracted using 0.1 mol/L Na2HPO4 solution and analyzed by HPLC-MS/MS method. The recovery was 73.1%-99.0% and 76.7%-109.1% for DPAA and PAA, respectively. The matrix effect was 107%-115% and 102%-107% for DPAA and PAA, respectively. The instrument detection limit (IDL) was 0.01 μg/L for DPAA and 1.00 μg/L for PAA. The method detection limit (MDL) was 2.52-3.42 µg/kg for DPAA and 0.23-0.33 mg/kg for PAA. The intraday and interday relative standard deviations (RSDs) were less than 5.0% for both analytes. These results showed that the established method can meet the requirements of quantitative analysis of DPAA and PAA in soil samples.
(2) Bath experiment and EXAFS technique were used to investigate the adsorption characteristics and molecular binding mechanisms of DPAA on 11 coastal soils and two non-coastal soils (Acrisol and Gleyic Acrisol collected from Yingtan city, Jiangxi province). The results showed that Acid Sulfate soil, Gleyic Acrisol, Andosol, Latosol or Acrisol with a higher content of iron (hydr)oxides exhibited stronger adsorption capacity toward DPAA compared with Cambisol, Fluvisol or Phzeozem with a relatively lower content of iron (hydr)oxides, and all adsorption isotherm could be well fitted by the Freundilich equation. Overall, the Kf values increased with the increase in salinity. The non-crystalline oxides played the most important role in DPAA adsorption. DPAA adsorbed on soil mainly via forming bidentate-binuclear and monodentate-monuclear complexes with As-Fe distances at 3.34 and 3.66 Å, respectively.
(3) The sequential extraction procedure (SEP) and EXAFS technique were employed to investigate the speciation and adsorption mechanisms of DPAA in clay mineral fractions in the soils. The results showed that the specifically adsorbed DPAA and DPAA associated with (hydr)oxides of iron and aluminum was the dominant phase and it constituted 45.1%-88.7% of the total DPAA. DPAA adsorbed on soil clay minerals mainly via specific adsorption, interacting with iron (hydr)oxide either through surface complexation or through embedding inside of the mineral particles and primarily formed 2C complexes with As-Fe distances of 3.18-3.25 Å.
(4) Adsorption kinetics, SEP, fourier transformed infrared (FTIR) and EXAFS techniques were used to investigate the adsorption capacities and molecular binding mechanisms of DPAA on different iron minerals.The results showed that DPAA loadings decreased in the following order: Ferrihydrite (Fer) ≈ Hematite (Hem) > Goethite (Goe) > Magnetite (Mag) > Siderite (Sid). DPAA formed simultaneously innersphere 2C complexes and out-sphere complexes on Goe, Hem and Sid, while dominantly inner-sphere 2C complexes on Fer and Mag with the formation of out-sphere complexes occured to only a limited extent, and As-Fe distances ranged from 3.19 to 3.33 Å.
(5) An eight-week incubation experiment was carried out to elucidate the effect and mechanism of biostuimulation remediation for DPAA in the Phzeozem with the addition of sodium lactate and sodium sulfate. The results showed that DPAA was effectively mobilized in culture with the addition of carbon and sulfur, and DPAA was mobilized primarily due to sodium lactate addition and iron reduction at the initial (0-4 weeks) and later incubation stages (4-8 weeks), respectively. Sulfate reduction played an important role in DPAA transformation, and DPAA was firstly released into the liquid-phase and then thionated coupled with sulfate reduction.
 (6) An eight-week incubation experiment was also carried out to elucidate the effect and mechanism of biostuimulation remediation for DPAA in the Acrisol with the addition of sodium lactate and sodium sulfate. The results showed that DPAA was effectively mobilized in culture with the addition of carbon and sulfur, and was mobilized primarily due to sodium lactate addition at the initial incubation stage and iron reduction with the extension of the incubation time, respectively. PAA and diphenylthioarsinic acid (DPTAA) were the major metabolites of DPAA in culture with the addition of carbon and sulfur, and DPAA was firstly released into the liquid-phase and then transfotmed to PAA or DPTAA.
(7) Other laboratory experiments were carried to investigate the degradation efficiencies, the related influencing factors and degradation pathways of DPAA by Fenton and Fenton-like reactions. The results showed that under the preparation conditions of initial H2O2 concentration of 1.0 mol/L, iron catalyst dosage of 0.25 mol/L, soil-water ratio of 1:3 and reaction time of 1 h, more than 65% of the total DPAA in the Acrisol and Phaeozem were removed by Fenton and Fenton-like reactions, respectively. DPAA was on the one hand degraded to PAA by dephenylation, and subsequently partially degraded to inorganic arsenic, on the other hand, high activity ·OH could be involved in the phenyl substituents of DPAA to form hydroxylated DPAA during Fenton and Fenton-like reactions.
学科领域环境科学技术基础学科其他学科
文献类型学位论文
条目标识符http://ir.yic.ac.cn/handle/133337/22442
专题中科院烟台海岸带研究所知识产出_学位论文
作者单位1.中国科学院烟台海岸带研究所
2.中国科学院大学
第一作者单位中国科学院烟台海岸带研究所
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朱濛. 土壤中二苯砷酸的结合机制和生物及化学修复研究[D]. 北京. 中国科学院大学,2017.
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