污染土壤中硝基苯热脱附研究

以南京黄棕壤和江西红壤为实验土样,通过实验室批量热脱附试验,研究了热脱附温度、热脱附时间、土壤含水率、初始浓度以及土壤类型等对污染土壤中硝基苯热脱附效率的影响。结果表明,当土壤含水率2%,硝基苯初始浓度165.54 mg/kg,脱附温度300℃,脱附时间30 min时,硝基苯的热脱附效率为85.88%,处理后土壤中硝基苯残留浓度为23.37 mg/kg,远低于展览会用地土壤环境质量评价标准（HJ350-2007）（暂行）中的B级标准限值（100 mg/kg）。土壤含水率过高和过低都不利于硝基苯的脱附,当含水率为15% 时,达到了最佳的热脱附效果。硝基苯初始浓度对其脱附效率有较大的影响,随初始浓度的增加,硝基苯脱附效率呈现增大的趋势。而土壤类型对硝基苯热脱附效率的影响较小,在实际修复过程中可以忽略。研究结果可为热脱附法修复硝基苯污染土壤的实际应用提供科学依据。     

复杂有机物污染地块原位热脱附修复技术的研究

鉴于复杂有机物污染地块治理难度大,国内用地形势紧张,因此关于原位热脱附技术在复杂有机物污染地块中的运用越来越受到学术界的广泛关注。综述了三类主要的原位热脱附技术:电阻热脱附、热传导热脱附和蒸汽热脱附,根据污染场地状况总结了各类原位热脱附技术的影响因素和适用范围,并给出了相应的技术路线。阐明了温度、时间、土壤含水率、土壤渗透性等因素对热脱附效果的影响。研究表明温度越高、时间越长、土壤含水率适中、渗透性较好的土壤,有机污染物热脱附性能更好。对于有机物重度污染的难处理地块,相比其他原位修复技术,原位热脱附技术具有更好的运用前景。     

植物–微生物联合对土壤不同粒径组分中 PAHs 的修复作用

采用温室盆栽试验,在种植紫花苜蓿的同时,分别施加木霉菌剂、根瘤菌菌剂以及木霉与根瘤菌复合菌剂,并采用离心分级法将处理后土壤分为4个粒径团聚体,即细黏粒(0.1~1μm)、粗黏粒(1~5μm)、粉粒(5~50μm)以及细砂粒(50~250μm),分析了植物–微生物联合作用对不同粒径土壤中PAHs的去除效应。研究结果表明:紫花苜蓿–根瘤菌联合作用对PAHs污染土壤的修复效果最优,其降解率达60%以上。不同粒径组分中PAHs含量的分布表现为细砂粒粉粒粗黏粒细黏粒,且PAHs在不同粒径团聚体中去除率差异性较大。低环(2、3环)PAHs在各粒径组分中去除率较低(20%以下),并在不同粒径组分间呈非均衡分配状态;4环PAHs的去除主要集中在粉粒和细砂粒中,而5环PAHs的去除主要发生在细黏粒上。可见,PAHs在土壤不同粒径组分中分布特征及降解效应为进一步阐明PAHs污染土壤的生物修复机制提供了科学依据。     

污染土壤中PAHs水蒸气剥离法试验研究

对水蒸气剥离法去除污染土壤中多环芳烃(PAHs)进行了研究，研制了实验室规模的污染土壤中PAHs水蒸气剥离法试验装置，获得了多环芳烃脱附的基本试验数据，考察了泥浆质量流量、泥浆浓度和反应温度对脱附效率的影响，对上述影响因素进行了分析，确定了分离工艺的最佳参数范围，为大规模治理污染土壤提供了可靠依据。试验结果表明，泥浆流速增加会显著降低脱附效率，一般应取G≤2 kg/s为好。另外，提高反应温度则会使脱附效率有所增加，故反应器内温度保持在150～200℃范围内较好。     

干湿循环下云南非饱和红土土—水特性研究

以云南红土为研究对象,以脱湿、吸湿引起的干湿循环作为控制条件,考虑初始干密度(1.20,1.25,1.30g/cm3)、初始含水率(30.0%,33.0%,36.0%)、预固结压力(0,50,100,200kPa)、过筛粒径(0.5,1.0,2.0mm)等影响因素,通过压力板仪法,研究干湿循环下云南非饱和红土的土—水作用特性。结果表明:干湿循环过程中,不同影响因素下红土的基质吸力随含水率的增大而减小,其土—水特征曲线呈直线型或"倒J"形,其脱湿变化过程可以分为快速脱湿、缓慢脱湿、稳定脱湿3个阶段,对应的吸湿变化过程也可以分为快速吸湿、缓慢吸湿、稳定吸湿3个阶段。相同基质吸力下,随初始干密度、初始含水率、预固结压力的增大,红土的含水率增大;随粒径的增大,红土的含水率减小。初始干密度、预固结压力、粒径(0.5mm除外)影响下的红土的土—水特征曲线可采用幂函数关系进行拟合,不同初始含水率、粒径0.5mm时的土—水特征曲线可采用线性函数关系进行拟合。红土脱湿过程的含水率高于吸湿过程的含水率,脱湿—吸湿过程中的土—水特征曲线存在滞后现象,其实质在于干湿循环作用下红土具有孔隙效应、瓶颈效应、角度效应的综合结果。     

低分子量有机酸作用下土壤中菲和芘的残留及形态

采用微宇宙试验方法,以菲和芘为多环芳烃(PAHs)代表物,研究了几种低分子量有机酸作用下黄棕壤中菲和芘的残留和形态。结果表明,老化60 d后土壤中菲和芘的残留含量明显减少;不施加有机酸的对照土壤中,菲和芘的残留含量为10.13和29.18 mg kg-1,去除率为87.33%和63.50%。与对照相比,供试浓度(0～64 mg kg-1)范围内,柠檬酸、草酸、酒石酸等3种低分子量有机酸作用下土壤中PAHs残留含量提高,去除率减小,表明供试条件下有机酸抑制土壤中菲和芘的降解;进一步分析发现,少量(≤4 mg kg-1)的有机酸即可对PAHs降解产生高的抑制效果。微生物降解在PAHs的去除中起重要作用,且芘比菲更抗微生物降解。供试条件下,可脱附态和有机溶剂提取态是土壤中菲和芘存在的主要形态,而结合态残留占总残留的比例很小(<8.5%)。3种有机酸均提高了土壤中可脱附态和有机溶剂提取态菲和芘的残留含量,施加有机酸使土壤中菲和芘的可脱附态含量较对照分别提高了46.67%～749.1%和1.83%～80.20%,有机溶剂提取态则提高了8.73%～375.2%和22.63%～114.3%;低分子量有机酸作用下结合态的菲和芘含量仍很小。     

基于热脱附法的汞污染土壤修复研究进展

以汞为代表的重金属土壤污染已成为当前最受关注的环境议题之一。为去除土壤中的汞成分,使土壤满足工农业使用要求,人们已提出了多种技术手段,其中热脱附法以其诸多优点受到了大量关注。本文详细介绍了热脱附法的装置和工作原理,并根据已有研究和工程案例总结了该方法用于汞污染土壤修复应注意的问题,以及后续技术发展的方向。     

东莞市土壤中多环芳烃的含量、代表物及其来源

2002年10~12月采集东莞市各地土壤样品64个,采用气相色谱-质谱仪对土壤中的16种优先控制的多环芳烃(PAHs)进行分析。结果显示,东莞市土壤中16种PAHs平均含量413μg/kg,含量较高的几种组分分别是菲、萤蒽、屈、苯并[b]萤蒽、芘。与PAHs总含量相关性较好的7种组分分别为屈、苯并[a]蒽、苯并[b]萤蒽、苯并[k]萤蒽、苯并[a]芘、茚并[1,2,3]芘、二苯并[a,h]蒽;所有相关系数R2均超过0.9000,可作为东莞市土壤中PAHs的代表物。北部平原水乡的PAHs污染明显高于南部丘陵山区、水乡上游保护区以及中部过渡带。化石燃料高温燃烧产物的大气沉降为东莞市土壤中PAHs的主要来源。东莞市农业土壤中PAHs含量显著低于天津市受污染严重的农业土壤。     

初始湿度对覆膜开孔蒸发水盐运移的影响

为了解初始含水率(湿度)变化对覆膜开孔蒸发的盐分与蒸发量的定量关系,通过不同湿度土壤的室内蒸发实验,研究了覆膜开孔率影响下土壤水分和盐分的运动特征.结果表明,初始含水率越大,不同覆膜条件下累积蒸发量越大,单位膜孔面积累积蒸发量(E_R)随开孔率增大而急剧减小.不同初始湿度的ER与覆膜开孔率的关系可用乘幂表示;表土返盐量随覆膜开孔率的增大而逐渐增加;不同含水率土壤的盐分浓度削面分布趋势一致,含水率越大,表层盐分浓度越大,含水率较小的土壤.盐分浓度在表层最大.在盐分含量最低点附近达到最小值,表层以下4-13cm的盐分浓度均小于初始值;不同覆膜开孔率条件下不同含水率土体剖面盐分浓度与垂直位置之间可用幂函数表示.研究表明,初始湿度对土壤水盐运动的影响存在定性特征,而覆膜开孔率对水盐运动的影响有定量关系可循.     

有机黏土对污染土壤中苋菜生理和吸收积累菲、芘的影响

基于有机改性黏土具有廉价、高效吸附多环芳烃(PAHs)等特性,探究了3-巯基丙基三甲氧基硅烷改性蒙脱土(TMSP-SMF)和十六烷基三甲基溴化铵改性蒙脱土(CTAB-SMF)对污染土壤中PAHs的固定效果,并考察了其施用后对土壤理化性质、微生物群落以及植物吸收累积PAHs的影响.结果表明:TMSP-SMF和CTAB-S...     

名山河流域黄壤组分对微团聚体吸附解吸镉的影响

选取名山河流域4种土地利用方式（林地、水田、茶园、旱地）的黄壤为研究对象,采用平衡液等温吸附法和NH4OAC、EDTA溶液解吸法,研究土壤组分（有机质、游离氧化铁）对微团聚体吸附解吸Cd2＋的影响。结果表明：去除土壤组分前后,原土及各粒径微团聚体对Cd2＋的吸附量均随Cd2＋初始浓度增大而增大,吸附量均按以下次序递减：（〈0.002mm）〉2～0.25mm〉原土〉0.053～0.002mm〉0.25～0.053mm,与有机质、游离氧化铁、CEC呈极显著正相关。吸附减少量大小关系为：去除有机质〉去除游离氧化铁,有机质的贡献率大于游离氧化铁。Freundlich方程拟合效果最佳,达到极显著水平,分布系数Kd值与Cd2＋初始浓度呈曲线负相关。NH4OAC解吸率随原吸附Cd2＋初始浓度增大而增大,以最大解吸率计,递减规律为：0.25～0.053mm〉0.053～0.002mm〉原土〉2～0.25mm〉（〈0.002mm）;EDTA解吸率随原吸附Cd2＋初始浓度增大而减小,递减规律与NH4OAC解吸率相反。去除土壤组分后,NH4OAC解吸率上升,EDTA解吸率下降,茶园与旱地黄壤非解吸率减小,林地与水田黄壤非解吸率增大。去除土壤组分后,非专性吸附与吸附总量呈极显著正相关,专性吸附与吸附总量呈极显著负相关。     

Cosolvent-enhanced Desorption and Transport of Heavy Metals and Organic Contaminants in Soils during Electrokinetic Remediation

Numerous sites are contaminated with both heavy metals and polycyclic aromatic hydrocarbons (PAHs) and the technologies to treat such mixed contaminants are very limited. Electrokinetic remediation has the potential to remediate mixed contaminants in soils, including low permeability soils; however, the efficiency of this technology depends on the extracting solution employed. Previous studies on electrokinetic remediation have focused on the removal of heavy metals and organic compounds when they exist individually in clayey soils. In the present study, the feasibility of using cosolvents to enhance the electrokinetic removal of PAHs from clayey soils in the presence of heavy metals is investigated. A series of laboratory electrokinetic experiments was conducted using kaolin soil spiked with phenanthrene and nickel at concentrations of 500 mg/kg each to simulate typical field mixed contamination. Experiments were performed using n-butylamine (cosolvent) at concentrations of 10 and 20% and deionized water, each mixed with 0.01 M NaOH solution and circulated at the anode to maintain alkaline conditions. A periodic voltage gradient of 2 VDC/cm in cycles of 5 days on and 2 days off was applied in all the tests. During the initial stages when the soil pH was low, nickel existed as a cation and electromigrated towards the cathode. However, as the soil pH increased due to hydroxyl ions generated at the cathode and also flushing of high pH n-butylamine solution from the anode, nickel precipitated with no further migration. Phenanthrene was found migrating towards the cathode in proportion to the concentration of n-butylamine. The extent of phenanthrene removal was found to depend on both the electroosmotic flow and the concentration of n-butylamine, but the presence of nickel did not influence the transport and removal of phenanthrene.     

熟污泥改性黄土对镉的吸附解吸特征

使用序批实验方法,研究熟污泥改性黄土对镉(Cd)的吸附解吸特征。结果表明:Cd初始添加浓度大于20 mg/L,供试改性黄土对Cd的吸附等温线发生显著变化;Freundlich型吸附等温式是描述供试改性黄土对Cd吸附过程的最佳模型。各土样对Cd的解吸量与吸附量的关系可以用幂函数很好地描述。随着土样中熟污泥含量的增加,Cd的吸附固定作用增强。有机质成分是影响供试土样Cd固定能力最大的因素。     

Low‐molecular‐weight organic acids enhance desorption of polycyclic aromatic hydrocarbons from soil

The impact of low‐molecular‐weight organic acids (LMWOAs) on desorption of phenanthrene and pyrene as representative polycyclic aromatic hydrocarbons (PAHs) from a contaminated soil was investigated by using a laboratory batch experiment. Three LMWOAs were used in this study and were citric, oxalic and malic acids. The LMWOAs in aqueous solution promoted desorption of PAHs from soil significantly and demonstrated an increasing trend as the concentration of LMWOAs increased. When compared with desorption of phenanthrene and pyrene from soil to water, the addition of LMWOAs enhanced desorption of test PAHs by up to 285 and 299%, respectively. Among the three LMWOAs studied, citric acid demonstrated the greatest efficiency in promoting PAH desorption from soil. Solutions of LMWOA continuously promoted PAH removal from soil during the multiple cycles of desorption. Overall, the experimental results suggest that LMWOAs in aqueous solution could disrupt soil organic matter (SOM)–metal cation–mineral linkages in soils, resulting in the release of SOM from soil and simultaneous increase of dissolved organic carbon (DOC) in solution. The loss of SOM from soil and increase of DOC in solution are responsible for the enhanced PAH desorption from soil. The positive correlation between DOC in solution and desorbed PAHs from soil suggests that the loss of SOM from soil plays an important role in LMWOA‐enhanced desorption of PAHs from soil.     

Effect of SDBS–Tween 80 mixed surfactants on the distribution of polycyclic aromatic hydrocarbons in soil–water system

Purpose

Enhancing desorption of hydrophobic organic contaminants from soils is a promising approach for the effective remediation of soils contaminated with organic compounds. The desorption efficiency of chemical reagent, such as surfactant, should be evaluated. In this study, the effect of mixed anionic–nonionic surfactants sodium dodecylbenzene sulfonate (SDBS)–Tween 80 on the distribution of polycyclic aromatic hydrocarbons in soil–water system was evaluated.

Materials and methods

Batch desorption experiments were employed to evaluate the distribution of polycyclic aromatic hydrocarbons (PAHs) and surfactants in soil–water system. PAHs and SDBS were determined by high-performance liquid chromatography, Tween 80 by spectrophotometry, and total organic carbon with a carbon analyzer.

Results and discussion

Sorption of PAHs to soil was increased at low surfactant concentration due to the effective partition phase on soil formed by sorbed surfactants. The mixture of anionic and nonionic surfactants decreased the sorption of surfactants to soil, increasing the effective surfactant concentration in solution and thus decreasing the sorption of PAHs on soil. Anionic–nonionic mixed surfactant showed better performance on desorption of PAHs from soil than single surfactant. The greatest desorption efficiency was achieved with low proportions of SDBS (SDBS/Tween80?=?1:9).

Conclusions

SDBS–Tween 80 mixed surfactant showed the highest desorption rate with low proportion of SDBS, which indicated that the addition of relative low amount of anionic surfactant could significantly promote the desorption efficiency of PAHs by nonionic surfactants. Results obtained from this study did provide useful information in surfactant-enhanced remediation of soil and subsurface contaminated by hydrophobic organic compounds.     

Ultrasonic Enhanced Desorption of DDT from Contaminated Soils

In this study, using high-power low-frequency ultrasound, heated slurries with anionic surfactant sodium dodecyl sulfate (SDS) were treated to enhance desorption of DDT from soils with high clay, silt, and organic matter content and different pH (5.6?C8.4). The results were compared with DDT extracted using a strong solvent combination as reference. Slurry ranges from 5 to 20 wt.% were studied. For a soil slurry (10 wt.%) at pH 6.9 with 0.1% v/v SDS surfactant heated to 40°C for 30 min, desorption was above 80% in 30 s using 20 kHz, 932 W/L ultrasonic intensity without solvent extraction. Other soils gave lower desorption efficiency in the range 40?C60% after 30 s ultrasonic treatment. The percentage of organic matter, dissolved organic carbon, soil surface area, clay and silt percentage, and soil pH level were the key parameters influencing variations in desorption of DDT in the three soils in similar experimental conditions. DDT dissolution in SDS and soil organic matter removal employing the ultrasonic-enhanced organic matter roll-up mechanism emerged as the two best possible methods of DDT desorption. The method offers a practical, potentially low-cost alternative to high volume, costly, hazardous solvent extraction of DDT.     

外源添加作物秸秆对PAHs污染土壤有机碳矿化和污染物降解的影响

本文通过土壤腐解试验研究外源添加水稻或玉米秸秆对多环芳烃（PAHs）污染土壤CO2-C释放和污染物去除率的影响，同时清晰秸秆腐解中间产物溶解性有机碳（DOC）与土壤PAHs降解的关系。结果表明：秸秆添加处理促进了PAHs污染土壤CO2-C的释放，以玉米秸秆提升效果较好。外源添加秸秆显著增加了土壤DOC含量，且增加幅度随秸秆添加量的增加而增大；水稻秸秆对土壤DOC含量的提升幅度较大。与对照相比，秸秆添加处理下土壤菲、芘残留量均显著降低，菲、芘去除率显著增加，去除效果：玉米＞水稻，高量＞低量，菲＞芘；与对照相比，添加高量玉米秸秆处理（PY15）对土壤菲、芘去除率的增加幅度分别为91.7%和182%。此外，在一定范围内土壤DOC含量与PAHs去除率呈正相关关系。可见，农作物秸秆，尤其是玉米秸秆添加可提升PAHs污染土壤有机碳矿化，亦可在提升土壤DOC含量的同时促进污染土壤PAHs的降解。     

Microwave heating remediation of soils contaminated with diesel fuel

Purpose

Diesel fuel represents a permanent source of soil pollution, and its removal is a key factor for human health. To address the limitations of conventional remediation techniques, microwave (MW) heating could be employed due to its great potentiality. This work presents the lab-scale experiments performed to study the potential of MW processing for diesel-polluted soils treatment and related modeling for the optimization of MW systems operating conditions.

Materials and methods

A sandy soil was artificially contaminated with diesel fuel, moisturized with different amounts of water content, and thermally treated by MW radiation using a lab-scale apparatus to investigate the effect of soil moisture on soil temperature profiles and contaminant removal kinetics. An operating power, ranging from 100 to 1,000 W, and treatment times of 5, 10, 18, 30, and 60 min were investigated. Contaminant residual concentration values were fitted using the first order kinetic model, and desorption parameters were calculated for each soil at different operating powers.

Results and discussion

Main results show that the operating power applied significantly influences the contaminant removal kinetics, and the moisture content in soil has a major effect on the final temperature reachable during MW heating. Minimal contaminant concentrations were achievable by applying powers higher than 600 W for a treatment time longer than 60 min. For remediation times shorter than 10 min, which result in a soil temperature of about 100 °C, the effect of the distillation process increases the contaminant removal, whereas for longer times, soil temperature is the main key factor in the remedial treatment.

Conclusions

MW thermal desorption of diesel-polluted soil was shown to be governed by pseudo-first-order kinetics, and it could be a better choice for remediation of diesel-polluted soils, compared to several biological, chemical–physical, or conventional thermal treatments, due to its excellent removal efficiency. The results obtained are of scientific and practical interest and represent a suitable tool to optimize the treatment operating conditions and to guide the design and the scale-up of MW treatments for full-scale remediation activities of diesel-polluted soils.     

Adsorption and Desorption of Copper in Pasture Soils

Abstract

Copper (Cu) is bound strongly to organic matter, oxides of iron (Fe) and manganese (Mn), and clay minerals in soils. To investigate the relative contribution of different soil components in the sorption of Cu, sorption was measured after the removal of various other soil components; organic matter and aluminum (Al) and Fe oxides are important in Cu adsorption. Both adsorption and desorption of Cu at various pH values were also measured by using diverse pasture soils. The differences in the sorption of Cu between the soils are attributed to the differences in the chemical characteristics of the soils. Copper sorption, as measured by the Freundlich equation sorption constants [potassium (K) and nitrogen (N)], was strongly correlated with soil properties, such as silt content, organic carbon, and soil pH. The relative importance of organic matter and oxides on Cu adsorption decreased and increased, respectively, with increasing solution Cu concentrations. In all soils, Cu sorption increased with increasing pH, but the solution Cu concentration decreased with increasing soil pH. The cumulative amounts of native and added soil Cu desorbed from two contrasting soils (Manawatu and Ngamoka) during desorption periods showed that the differences in the desorbability of Cu were a result of differences in the physico‐chemical properties of the soil matrix. This finding suggests that soil organic matter complexes of Cu added through fertilizer, resulted in decreased desorption. The proportions of added Cu desorbed during 10 desorption periods were low, ranging from 2.5% in the 24‐h to 6% in the 2‐h desorption periods. The desorption of Cu decreased with increasing soil pH. The irreversible retention of Cu might be the result of complex formation with Cu at high pH.