|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|
（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。
（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。
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.
|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.|