影响土壤中PAHs降解的环境因素及促进降解的措施

土壤中的多环芳烃(PAHs)类有机污染物的生物有效性低,不易降解。本文综述了影响污染土壤中多环芳烃降解的环境因素和促进降解措施的研究进展。影响土壤中多环芳烃降解的因素,包括水分、养分、土壤物理条件等;促进土壤中多环芳烃降解的措施有:向污染土壤添加有机溶剂、利用冯顿反应、添加堆肥和有机物料等。从目前研究来看,应当通过促进多环芳烃从土壤上解吸和培育具有较高多环芳烃降解能力的微生物来促进多环芳烃污染土壤的修复。     

植物修复多环芳烃污染土壤的根际效应机制研究进展

多环芳烃类有机污染物在土壤中可长期存在,进而通过食物链对人类健康产生重大潜在风险。对多环芳烃污染土壤进行植物修复是一种环境友好且经济有效的污染补救策略。进行植物根际效应机制研究对于开发可持续性多环芳烃污染土壤的植物修复技术具有重要指导意义。对近年来的相关研究工作进行了总结,结果表明:多种禾本科植物具有较强的多环芳烃污染耐受性和较好的修复效能,利用多植物混植的联合修复方式表现出优于单一植物的修复优势。低分子量有机酸类根系分泌物通过与土壤中多环芳烃污染物形成反馈回路决定植物修复体系中多环芳烃的命运。修复植物根系分泌物可塑造特定的根际微生物区系,根际微生物可通过多种机制来降解土壤环境中的多环芳烃。针对在植物修复多环芳烃污染土壤研究过程中尚存在一些问题,提出了未来植物修复根际效应机理研究中应该关注的重点和方向,旨在为优化多环芳烃污染土壤植物修复技术提供科学依据与理论参考。     

生物质炭中的污染物含量及其田间施用的环境风险预测

生物质炭在碳固定、污染修复和酸性土壤改良中的应用非常广泛,但对生物质炭中所含污染物的研究甚少,其在田间应用中的环境风险并不清楚。该文选择松针和麦秆为原料,采用不同制备方法,研究了不同条件下获得的生物质炭中的重金属和多环芳烃含量,并初步评估了其田间应用的环境风险。研究表明,不同有机废弃物来源制备的生物质炭中均含有一定量的重金属(0.301～128mg/kg)和多环芳烃(1.48～5.48mg/kg);松针制备的生物质炭中的重金属含量普遍高于麦秆制备的生物质炭,而多环芳烃含量则相反,且高温制备有助于降低生物质炭中的多环芳烃含量;在低施用量的田间条件下,生物质炭的施用不易对土壤造成多环芳烃的环境风险,但在高施用量条件下,生物质炭中含有的多环芳烃容易使土壤中多环芳烃含量达到中度或重度污染的程度;生物质炭中的重金属在土壤中的积累量比较有限,环境风险较小。     

土壤/沉积物中天然有机质对疏水性有机污染物的吸附作用

通过对土壤/沉积物中天然有机质的组成分析,阐述了天然有机物在吸附疏水性有机污染物过程中所起的重要作用,其中包括可溶性有机质的增溶作用和不溶性有机质的吸附作用。本文着重探讨了天然有机质结构的异质性对吸附作用的影响,导致吸附等温线的非线性,从而从土壤/沉积物有机质的微观结构上进一步解释了非线性吸附机理。     

1,2,4-三氯苯/四氯乙烯和1,2,4,5-四氯苯在土壤/沉积物上的竞争吸附

在多种有机污染物共存的水-土壤/沉积物体系,疏水性有机污染物(HOCs)的吸附/解吸行为与其在单溶质吸附体系有很大的不同[1～7]。共溶质的存在,可能改变主溶质的迁移能力、生物有效性和毒性[2],因此,针对多污染物复杂体系修复方案就会更加复杂,清除污染物的目标也变得更为困难。已有研究表明,竞争吸附发生在土壤/沉积物自然有机质(NOM)的硬碳部分[1～4,8]。但是基于具体的竞争吸附机制尚存在不少疑问,在以前的关于多溶质组分体系的竞争和取代实验研究中也存在一些不同的结果,譬如有些研究人员报道了共存溶质之间存在竞争现象,并且已经吸附的溶质会被另一种溶质取代的现象[9,10],而相反的研究结果也屡见     

北京市东南郊再生水灌区地下水多环芳烃污染风险评估

为研究污染物随再生水进入地下环境后其迁移衰减情况及对地下水的潜在危害性,以Multi-cell模型为基础,结合污染物质量守恒、在水土中吸附再分配、生物降解等机理,针对地下水污染风险评估构建了计算污染物随水在土壤剖面的垂向迁移衰减一维模型,并以北京通州大兴再生水灌区为研究区域,以再生水中持久性有机污染物多环芳烃萘和菲为研究对象,根据当地钻孔资料及灌溉水水质、地下水水质资料,应用该模型进行试算。结果表明,经过多年连续灌溉后,通州大兴大部分地区进入潜水含水层的萘、菲浓度较低,整体污染风险较低,仅在通州区潞城镇等个别地区萘、菲浓度较高,应引起重视;由于大兴区整体包气带较厚,其污染风险低于通州区。土壤粘土层是萘、菲积累的主要层位,其吸附容量远大于细砂等粗颗粒介质,在土壤表层低环多环芳烃迁移性更强。应用这一模型,能够较为宏观地掌握通州大兴再生水灌区不同区域地下水中多环芳烃萘和菲的污染风险差异。     

纳米TiO2对土壤Hg2+吸附解吸性能的影响

为了研究纳米TiO_2对土壤吸附解吸汞性能的影响,以三峡水库消落区土壤为代表,选择2种晶型(锐钛矿和金红石)的纳米TiO_2颗粒,设置3个浓度梯度(2,4,8g/kg),制成含有不同浓度纳米TiO_2颗粒的土样,配制不同浓度的Hg~(2+)溶液,进行吸附解吸试验。结果表明:纳米TiO_2颗粒可提高土壤对Hg~(2+)的吸附量,但受颗粒的晶型和浓度的影响;锐钛矿颗粒对土壤吸附解吸Hg~(2+)的影响更大,其吸附作用力更强,不易解吸,其中4g/kg处理组吸附作用最强,与对照相比,最大吸附量可提高32.65%,且其解吸率低于对照组;金红石颗粒处理组对Hg~(2+)的吸附量随颗粒浓度的升高而增大,但吸附作用力较弱,容易被解吸,8g/kg处理组影响最大,与对照相比,最大吸附量提高18.18%,但其解吸率也最大。因此,纳米TiO_2颗粒增强土壤对汞的吸附作用,从而可能影响汞在环境中的迁移转化过程,特别是锐钛矿型颗粒。     

四环素对芘污染农田土壤微生物修复的影响及响应过程

针对城郊农田土壤中多环芳烃和抗生素复合污染的新特征,通过室内模拟土培实验,研究四环素(Tetracycline,TC)胁迫下,降解菌Sphingobium sp.PHE3对长三角典型农田土壤中芘的降解效果和影响机制。研究表明,接种降解菌处理(B)能明显促进土壤中芘的降解,TC的引入可显著抑制土壤中芘的深度降解过程(P0.05)。经过90天培养后,B处理与接菌+添加TC处理(BTC)的降解率分别为40.1%、25.7%,较对照分别提高了23.0倍、14.1倍。通过土壤微生物群落结构多样性分析发现,降解菌数量在经历90天的土壤环境适应期后逐渐快速增加,其数量变化与污染物芘在土壤中含量消减趋势呈负相关;引入芘和四环素对土壤细菌群落结构多样性和功能稳定性具有显著影响(P0.05),然而对土壤真菌群落影响不显著(P0.05)。此外,B和BTC处理条件下,土壤过氧化氢酶活性、荧光素二乙酸酯酶活性和土壤微生物生物量碳氮值显著高于单独添加芘处理(P)和单独添加TC处理(TC),但P处理与TC处理之间无显著差异(P0.05),说明外源污染物(芘或四环素)对于土壤酶活性和微生物生物量碳氮具有显著抑制作用(P0.05),致使降解菌功能作用受到抑制。综上研究结果表明TC可明显抑制土壤中典型四环多环芳烃的微生物降解过程,针对多环芳烃与抗生素复合有机污染农田土壤的微生物强化修复技术有待深入研究。     

生物质炭对有机污染物的吸附及机理研究进展

生物质炭是一种利用废弃生物质材料在缺氧或厌氧环境中热化学转换制备的多孔级富碳固体材料。因其吸附能力强,制备原料来源广泛,生产成本低且环境友好等优点受到学术界越来越多的关注。探究生物质炭对有机污染物的吸附机理和规律,对于评估其环境行为和应用价值至关重要。着重综述了目前研究报道的生物质炭吸附有机污染物的吸附机理,包括分配作用、表面吸附作用和孔隙截留等。一般低温生物质炭对非极性有机物的吸附机制以分配作用为主,这种非竞争性吸附机理可以解释高浓度有机污染物在生物质炭上的吸附过程。表面吸附是一种非线性竞争性吸附作用,是有机污染物在生物质炭表面有效吸附位点上形成静电作用或通过氢键、离子建、π-π相互作用等结合的过程。孔隙截留是另一种生物质炭固定有机污染物的微观机制,有机污染物在孔隙内部的分配和吸附也是生物质炭吸附能力的重要体现。而在实际复杂的污染环境中,各类生物质炭对有机污染物的吸附过程需要多种机制共同解释。此外,本文对吸附机制的影响因素进行了分析和总结,生物质炭自身理化特性决定了其应用价值,生物质炭的性质与有机污染物的极性、芳香性和分子大小等相匹配才能更好地实现吸附固定,不同的吸附环境如吸附介质、p H和共存离子等也会对吸附机制和吸附效果产生影响。最后,文章进一步探讨了生物质炭吸附有机污染相关研究未来应着重解决的问题,以及生物质炭在有机污染土壤修复中的应用前景。     

污泥中多环芳烃分析方法的综述

多环芳烃是列于美国EPA黑名单上的一组优先污染物,一般指2个或2个以上苯环以稠环形式相连的化合物,如萘、蒽、菲等,由于其特殊的结构,具有致癌、致畸、致突变作用,而且广泛的存在于环境当中,种类繁多且难降解,对人类的危害很大,所以对环境中多环芳烃的测定及分析引起人们的关注,分析测定环境中的多环芳烃越来越重要,本文对污泥中多环芳烃的分析测定方法进行了系统的综述     

Effect of soil pH on the sorption capacity of soil organic matter for polycyclic aromatic hydrocarbons in unsaturated soils

Sorption by soil organic matter (SOM) is considered the most important process affecting the bioavailability of hydrophobic organic chemicals (HOCs)in soil.The sorption capacity of SOM for HOCs is affected by many environmental factors.In this study,we investigated the effects of soil pH and water saturation level on HOC sorption capacity of SOM using batch sorption experiments.Values of soil organic carbon-water partition coefficient (K_OC) of six selected polycyclic aromatic hydrocar...     

腐殖物质对有机污染物的吸附行为及环境学意义

综述了近年来腐殖物质的研究进展,具体包含以下几个方面的内容:腐殖物质的分离、纯化、元素组成和结构特征及其环境意义。重点讨论了腐殖物质的环境学意义,阐述了腐殖物质主要是胡敏素在吸附疏水性有机污染物的过程中所起到的重要作用,其中包括可溶性腐殖物质的增溶作用和不溶性腐殖物质———胡敏素的吸附固定作用;且对吸附/解吸的机理及一些模型的建立进行了探讨。最后针对研究中面临的问题,提出了今后的重点研究方向。     

Potential contributions of smectite clays and organic matter to pesticide retention in soils.

Soil organic matter (SOM) is often considered the dominant sorptive phase for organic contaminants and pesticides in soil-water systems. This is evidenced by the widespread use of organic-matter-normalized sorption coefficients (K(OM)) to predict soil-water distribution of pesticides, an approach that ignores the potential contribution of soil minerals to sorption. To gain additional perspective on the potential contributions of clays and SOM to pesticide retention in soils, we measured sorption of seven pesticides by a K-saturated reference smectite clay (SWy-2) and SOM (represented by a muck soil). In addition, we measured the adsorption of atrazine by five different K-saturated smectites and Ca-saturated SWy-2. On a unit mass basis, the K-SWy-2 clay was a more effective sorbent than SOM for 4,6-dinitro-o-cresol (DNOC), dichlobenil, and carbaryl of the seven pesticides evaluated, of which, DNOC was sorbed to the greatest extent. Atrazine was sorbed to a similar extent by K-SWy-2 and SOM. Parathion, diuron, and biphenyl were sorbed to a greater extent by SOM than by K-SWy-2. Atrazine was adsorbed by Ca-SWy-2 to a much lesser extent than by K-SWy-2. This appears to be related to the larger hydration sphere of Ca(2+) (compared to that of K(+)) which shrinks the effective size of the adsorption domains between exchangeable cations, and which expands the clay layers beyond the apparently optimal spacing of approximately 12.2 A for sorption of aromatic pesticide structures. Although a simple relation between atrazine adsorption by different K-smectites and charge properties of clay was not observed, the highest charge clay was the least effective sorbent; a higher charge density would result in a loss of adsorption domains. These results indicate that for certain pesticides, expandable soil clays have the potential to be an equal or dominant sorptive phase when compared to SOM for pesticide retention in soil.     

土壤矿物和胡敏酸对阿特拉津的吸附-解吸作用研究

选取了6种土壤矿物(蒙脱石、高岭石、钙饱和处理蒙脱石、钙饱和处理高岭石、无定型氧化铁和无定型氧化铝),以及从土壤中提取纯化的3种胡敏酸为材料,采用批量吸附平衡法,研究土壤矿物和胡敏酸对阿特拉津的吸附特性。结果表明,各吸附剂对阿特拉津的吸附均能采用Frundlich方程进行较好地拟合(r≥0.982,p0.01)。胡敏酸对阿特拉津具有最大的吸附性能,其固-液分配系数(Kd值)随平衡浓度(Ce值)的变化基本恒定,吸附等温线呈线性(Frundlich方程常数N≈1),吸附以分配溶解作用为主,吸附可逆性较高。黏土矿物(特别是蒙脱石)对阿特拉津也具有较强的吸附能力,Kd值随Ce值增加而增加,吸附等温线呈S型(N1),吸附主要是通过表面亲水作用。无定型氧化铁铝的Kd值随Ce值增加而降低,当Ce达到一定水平后,Kd趋于恒定,吸附等温线呈L形(N1),吸附主要是通过无定型氧化物表面的羟基与阿特拉津分子间的化学键合作用,吸附可逆性最差。     

Organic matter effects on phosphorus sorption in sandy soils

Phosphorus (P) sorption processes in soils contribute to important problems in agriculture: a deficiency of this plant nutrient and eutrophication in aquatic systems. Soil organic matter (SOM) plays a major role in sorption processes, but its influence on P sorption remains unclear and needs to be elucidated to improve the ability to effectively manage soil P. The aim of this research was to investigate the influence of SOM on P sorption. The study was conducted in sandy soil profiles and in topsoils before and after removal of SOM with H₂O₂. The results were interpreted with the Langmuir and Freundlich isotherms. Our results indicated that SOM affected P sorption in sandy soils, but that P sorption also depended on specific soil properties (e.g. values of the degree of P saturation (DPS), P sorption capacity (PSC) and pH) often related to land use. Removal of SOM decreased PSC in most of the topsoils tested; other soil properties became important in controlling P sorption. An increase in P desorption observed after SOM removal indicated that SOM was potentially that soil constituent which increased P binding and limited P leaching from these sandy soils.     

运用岩石热解产生的S3和S4信号进行土壤有机质特征研究

Variations in the abundance of soil organic matter（SOM） constituents with different stability have a major impact on important environmental processes, e.g., carbon dioxide（CO2） fluxes between the soil and the atmosphere. Recently, besides the bulk Rock-Eval（RE） data, the mathematical deconvolution of the signals derived from hydrocarbon-like compounds released by thermal cracking of SOM during RE pyrolysis has been increasingly used to estimate the relative contribution of the major SOM classes differing in origin and preservation. This study applied the mathematical deconvolution of the S3 and S4 signals of carbon monoxide（CO） and CO2, produced both by the pyrolysis of the oxygen-containing moieties and by the oxidation of the residual highly resistant organic matter, to characterize the stability of these components. Our results suggested that the stability of the oxygen-containing moieties was controlled by the precursor material and was strongly affected by the land use and the presence of humic substances in the surface horizon of some main soil types in Hungary. In consistence with the bulk RE data, results of the mathematical deconvolution also proved to be diagnostic markers for discriminating the aquatic or terrigenous plants as the main sources of SOM. The mathematical deconvolution of S4 signals derived from the highly resistant SOM fraction allowed us to quantify the contribution of constituents with different stability. Furthermore, the results of this study displayed that the stability of this highly abundant SOM fraction in the surface soil samples depended on source biomass and intensity of leaching.     

Sorption of naphthalene derivatives on to soils from a long-term field experiment: a particle size fractionation and extraction study

The present work investigates the impact of site management on the retention of organic compounds in soil in a long‐term field experiment and focuses on the role of particle size fractions. Specifically, we studied the influence of long‐term farming practices on the soil’s ability to adsorb five hydrophobic organic compounds (HOCs), specifically naphthalene derivatives (naphthalene, 1‐naphthol, 1‐naphthylamine, 1‐hydroxy‐2‐naphthoic acid, 1,4‐naphthoquinone). We examined the sorption on soil and its particle‐size fractions with varying amounts and origins of organic matter in soil amended with farmyard manure and mineral fertilizers over more than 40 years. The soil organic matter had no significant impact on the sorption behaviour of the HOCs. Adsorption on the clay and silt fraction provided a deeper insight into the mechanisms and indicates a strong affinity with adsorption sites of the mineral phase. Naphthalene derivatives with hydrogen atoms in their functional groups adsorbed more strongly than other compounds on to soils containing smaller amounts of organic carbon. Desorption experiments with five organic extractants showed partitioning models for HOCs between extractant and soil surface. Only in experiments with the most polar extractant, formamide, did we observe an influence of the compound’s functional groups on the desorption mechanisms. Column experiments with a HPLC‐system and on‐line UV‐detection proved to be a satisfactory alternative to batch experiments. This approach should enable investigations of adsorption with larger numbers of compounds and soils at the same time.     

Long‐Term Tillage and Cropping System Effects on Chemical and Biochemical Characteristics of Soil Organic Matter in a Mediterranean Semiarid Environment

Several studies have reported how tillage and cropping systems affect quantity, quality, and distribution of soil organic matter (SOM) along the profile. However, the effect of soil management on the chemical structure of SOM and on its hydrophobic and hydrophilic components has been little investigated. In this work, the long‐term (19 years) effects of two cropping systems (wheat monoculture and wheat/faba bean rotation) and three tillage managements (conventional, reduced, and no tillage) on some chemical characteristics of SOM and their relationships with labile carbon (C) pools were evaluated. Soil samples were taken from the topsoil (0–15 cm) of a Chromic Haploxerert (central Sicily, Italy). After 19 years of different tillage and cropping systems management, total organic C significantly differed among treatments with the labile organic C pools showing the greater amount in no till and in wheat/faba bean plots. Hydrophobic and hydrophilic components of SOM, determined by diffuse reflectance infrared Fourier transform spectroscopy, were mainly affected by cropping system, whereas aromatic components of SOM by tillage. Soil organic matter components and characteristics showed significant correlations with the soil biochemical parameters, confirming the expected synergism between chemical and biochemical properties. This study demonstrated that (i) no tillage and crop rotation improve the chemical and biochemical properties of SOM of Vertisols under semiarid environment; and (ii) tillage management and cropping systems have affected, after 19 years, more the chemical and biochemical properties of SOM than its quantity. Copyright © 2014 John Wiley & Sons, Ltd.