包气带对三氯乙烯的吸附行为研究

有机污染物在包气带的吸附行为,直接影响有机污染物在环境中的迁移、转化等过程。采用浅层和深层包气带样品,利用批实验的方法研究不同有机碳含量的样品对三氯乙烯(TCE)的吸附行为。研究表明,包气带表层土壤比深层土壤的有机碳含量高,可能存在竞争吸附的问题,说明该土壤的吸附行为是以矿物吸附为主、有机质吸附为辅的类型;表层土壤的吸附具有较好的线性行为,不存在饱和吸附量;深层土壤有机碳含量低,其吸附为非线性的。     

土壤中有机碳含量对三氯乙烯的吸附影响实验

采用某地区土壤样品,利用批实验的方法,研究不同有机碳含量的土壤样品对三氯乙烯(TCE) 的吸附行为.研究表明,土壤样品中,由于有机碳含量不同,有机污染物三氯乙烯(TEC)的吸附量不同,存在有机碳含量的阈值区间(foc*).最小foc*=0.702%,最大foc*=1.831%,当foc<0.702%时,TCE吸附量随土壤样品的有机碳含量变化较小,基本不随foc变化而发生较大变化;在0.702%1.831%时,TCE吸附量随土壤样品的有机碳含量变化又变得平缓,基本上又不随foc升高而发生较大的变化.     

苯、甲苯碳同位素组成作为气源对比新指标的研究

利用热模拟与在线同位素分析技术研究了天然气与源岩中的苯和甲苯的央同位素组成变化特征,发现热成熟度和运移效应对苯、甲苯碳同位素组成影较小,同一类型气源岩热模拟产物中苯、甲苯同位素组成受热成熟度的影响不大。在４００～６００℃热模拟实验中,除个别点外,变化小于１‰,说明它们基本上不受热成熟度的影响。不同层位气源岩苯、甲苯碳同位素组成有明显区别,大多相差３‰以上。甲苯脱吸附实验表明,甲苯同位素组成在脱吸附     

水稻土中重金属元素Cd、Pb的竞争吸附——以长株潭地区水稻土为例

对中国南方的3个水稻土样品进行了Cd、Pb单一离子和混合离子吸附特点的研究。结果表明,3个水稻土样品中Cd、Pb的吸附特点都相似,Langmuir等温方程可很好地描述Cd、Pb的吸附等温线。3个土壤样品中,有较高pH值和较低有机物、CEC浓度、粘土含量、高岭石含量的2个土壤样品对Cd、Pb有较大的吸附量,且其等温吸附拟合的最大吸附量（B）也较大。在两组分混合溶液中,尽管共存离子的存在影响了土壤对单一离子的吸附,同时土壤对Cd的吸附在一定程度上受影响的程度大,但3个土壤样品都表现出对Pb有强的吸附能力。在3个土壤样品中,Langmuir等温方程中Pb的健合能常数（K）都大于Cd的健合能常数（K）,混合溶液中的K值高于单一溶液的K值,表明2种金属离子对吸附位点的竞争提高了特定吸附位点的保持力,使金属离子在土壤中特定位点的吸附更加坚固。     

水稻土中重金属元素Cd、Pb的竞争吸附 ——以长株潭地区水稻土为例

对中国南方的3个水稻土样品进行了Cd、Pb单一离子和混合离子吸附特点的研究。结果表明,3个水稻土样品中Cd、Pb的吸附特点都相似,Langmuir等温方程可很好地描述Cd、Pb的吸附等温线。3个土壤样品中,有较高pH值和较低有机物、CEC浓度、粘土含量、高岭石含量的2个土壤样品对Cd、Pb有较大的吸附量,且其等温吸附拟合的最大吸附量(B)也较大。在两组分混合溶液中,尽管共存离子的存在影响了土壤对单一离子的吸附,同时土壤对Cd的吸附在一定程度上受影响的程度大,但3个土壤样品都表现出对Pb有强的吸附能力。在3个土壤样品中,Langmuir等温方程中Pb的健合能常数(K)都大于Cd的健合能常数(K),混合溶液中的K值高于单一溶液的K值,表明2种金属离子对吸附位点的竞争提高了特定吸附位点的保持力,使金属离子在土壤中特定位点的吸附更加坚固。     

土壤酶对碘离子在土壤中吸附行为的影响

以批式试验法研究了微生物、葡萄糖氧化酶、脲酶、纤维素酶及其催化底物葡萄糖、尿素和纤维素对Ⅰ-在土壤中吸附的影响,结果表明微生物能显著提高Ⅰ-吸附量,但葡萄糖氧化酶、脲酶、纤维素酶及葡萄糖、尿素和纤维素对Ⅰ-吸附并无促进作用.葡萄糖氧化酶及葡萄糖含量在小于100 mg/L时对Ⅰ-吸附无影响,1000 mg/L时与Ⅰ-呈竞争吸附;脲酶及尿素随浓度增大,对Ⅰ-吸附的抑制作用变得明显;1～1000 mg/L范围内,纤维素酶和纤维素对Ⅰ-吸附没有影响;但葡萄糖氧化酶和葡萄糖生成的中间产物可促进土壤对Ⅰ-的吸附.平衡液中溶解性有机碳(DOC)含量随时间增加而逐渐降低,有机质浓度越大,降低趋势越明显.     

甲苯在土壤地下水中迁移规律研究

石油泄漏导致甲苯等有机污染物污染土壤地下水,并且甲苯等石油类有机污染物对土壤地下水污染具有隐蔽性强、难以逆转等特点,污染治理难度大。因此,研究甲苯有机污染物在土壤地下水中运移规律是治理的关键。该文以某污染场地为研究区,以甲苯有机污染物为研究对象,考虑了淋滤、吸附的影响,采用模型计算方法,分析了甲苯在污染场地土壤地下水中迁移规律。结果表明：甲苯在土壤地下水中迁移过程中,淋滤作用对甲苯浓度变化影响显著;吸附影响下扩散作用及地下水位变化对甲苯迁移产生的影响均受到抑制。该文获得的甲苯在土壤地下水中迁移规律可为甲苯有机污染物污染场地修复提供依据。     

土壤有机碳含量及异质性对三氯乙烯的吸附影响实验

采取北京城区表土样品和土壤标准参考样共7件,对原土样以及经H2O2氧化处理去除低聚合有机碳后的土样分别采用静态批实验方法,研究其对三氯乙烯(TCE)的等温吸附方程。实验结果表明7种土样对TCE的吸附模式均符合线性等温吸附方程,采用H2O2氧化去除土壤样品中的低聚碳,并没改变等温吸附线型,只是方程的参数发生了变化。剩余有机碳的含量仍都大于0.1%,仍然以有机碳的吸附为主;原土样、高聚碳、低聚碳对TCE吸附均表明,有机碳的含量与样品吸附TCE的能力没有明显的关系,证实不管是总有机碳、低聚碳还是高聚碳都有明显的异质性,它们所表现出来的吸附能力并不相同,有机碳结构组成的差异往往是影响其吸附的关键因素。而土壤有机碳经历矿化和腐殖化程度的差异是造成土壤有机碳结构组成差异的主要原因。     

包气带土壤组成对三氯乙烯的吸附影响研究

有机质和矿物质是包气带土壤中的主要吸附介质,其吸附特性直接影响有机污染物在环境中的迁移、转化等过程。分别采用分析纯石英砂和典型粘土矿物高岭石模拟土壤的原生矿物和粘土矿物,利用批实验的方法研究土壤中各组成部分对三氯乙烯(TCE)的吸附行为。土壤有机质的吸附行为通过全土样和矿物质的对比得出。结果表明,粘土矿物是吸附氯代烃的主要矿物质,原生矿物对氯代烃的吸附量很小;土壤有机质含量和土壤吸附量之间有很好的正相关性;土壤有机碳含量与土壤粘土矿物含量的比值是影响吸附行为的另一重要因素,比值越小,Koc值越大,土壤对TCE的亲和力就越强。由于自然界中的土壤有机质大都与矿物质形成有机质-粘土矿物结合体,据此推测有机质-矿物质结合体会影响有机质的组成和形态,从而对其吸附行为有重要作用。     

岩溶地下河系统石灰石对BTEX的吸附动力学和热力学

石油类单环芳香烃BTEX是岩溶地下水中常见的有机污染物,但有关BTEX与石灰石的吸附研究报道很少。文中利用静态吸附实验,研究了桂林寨底地下河系统石灰石含水介质对汽油组分BTEX化合物的吸附动力学和吸附热力学。结果表明：（1）石灰石含水介质对BTEX具有明显的吸附性,BTEX实验吸附容量介于0.004~0.061 mg/g,大小顺序为甲苯>苯>间对二甲苯>邻二甲苯>乙苯,其动力学过程适合用假二级动力学模型描述,表明乙苯和二甲苯的吸附速率明显高于甲苯和苯,模型预测的BTEX吸附容量介于0.005~0.067 mg/g,大小顺序与实验结果一致。（2）BTEX在石灰石含水介质中的吸附热力学符合Freundlich模型及其特例Linear模型,Freundlich常数介于0.076 4~0.189 3［mg/g］［L/mg］1/n,1/n介于0.943 4~0.970 1,BTEX分配系数为0.002 3~0.021 2 L/g。BTEX吸附能力顺序为间对二甲苯>乙苯>邻二甲苯>甲苯>苯。然而,石灰石与BTEX之间的吸附等温线不适合用Langmuir模型描述。这项研究能够为深入探讨BTEX在西南岩溶地下水中的迁移与归宿机制提供科学依据。     

A laboratory batch study on arsenic sorption and desorption on guava orchard soils of Baruipur,West Bengal,India

Groundwater contaminated with arsenic (As), when extensively used for irrigation, causes potentially long term detrimental effects to surface soils. Such contamination can also directly affect human health when irrigated crops, such as rice, vegetable and fruits, are used for human consumption. Therefore, an understanding of the sorption and desorption behavior of As in surface soils is of high importance, because these processes regulate the bioavailability of As in the soil environment. In this study, we have collected soils from guava orchards of Baruipur, West Bengal, and characterized soil chemistry and batch sorption and desorption behavior in the laboratory. The sorption and desorption behavior of As in the soils were examined using the Langmuir and Freundlich sorption equation. Regression analysis of the soil chemical characteristics and sorption equation parameters were also performed. The results suggest that the sorption behavior of arsenate is highly dependent on soil characteristics, specifically organic carbon, clay and Al₂O₃ content of the soils. Whereas desorption behavior is critically influenced by the presence of high concentrations of amorphous and/or crystalline Fe₂O₃ in the soils. Retention of the significant portion of As in the soils (~ 84% of the total) suggests that As in the orchard soils may not be highly bioavailable to plants for uptake. However, more detailed studies will be required to ascertain the role of individual soil components on the As sorption and desorption processes.     

Sorption characteristics of ethyl <Emphasis Type="Italic">tert</Emphasis>-butyl ether to Chinese reference soils

As a gasoline additive, ethyl tert-butyl ether (ETBE) has great market potential and its utilization might cause groundwater contamination problem. However, little research has been done on its sorption in soil. In this study, the sorption characteristics of ETBE to Chinese reference soils were studied in batch experiments. The results showed that the ETBE sorption to six soils can be described by linear sorption isotherm. The temperature influences the sorption process of ETBE to soils. The negative sorption enthalpy (ΔH < 0) indicated that the sorption process was exothermic. Furthermore, ΔH is in a range from −8 to −32 kJ/mol. This showed that van der Waals forces and other specific interactions happened simultaneously in the sorption process. With the increasing ionic strength, content of ETBE sorption to all soils decreased, which is probably also an indication of other sorption mechanisms besides ETBE partitioning into soil organic carbon.     

Effects of organic matter heterogeneity on sorption and desorption of organic contaminants by soils and sediments

This review highlights the major progress over the last decade on characterization of geochemically heterogeneous soil/sediment organic matter (SOM) and the impacts of SOM heterogeneity on sorption and desorption of hydrophobic organic contaminants (HOCs) under equilibrium and rate limiting conditions. Sorption and desorption by soils and sediments are fundamental processes controlling fate and transport of less polar and nonpolar organic pollutants in surface aquatic and groundwater systems. Recent studies have shown that soils and sediments exhibit an array of HOC sorption phenomena that are inconsistent with an early partition model based on an assumption of homogeneous gel-like SOM. Increasing data have revealed that isotherm nonlinearity, varied sorption capacity, sorption–desorption hysteresis, and slow rates of sorption and desorption are characteristics for HOC sorption by soils and sediments. These phenomena have been shown to result from different types of condensed SOM that exhibit capacity limiting sorption processes. Recent findings of glass transition phenomena and the nonlinear HOC sorption by humic acids provide a scientific foundation for drawing an analogy between humic acids and synthetic organic polymers that supports a dual mode model for sorption by soils and sediments. Humic acid is glassy or rigid at temperatures lower than its glass transition temperature and exhibits relatively nonlinear sorption isotherms for HOCs. Fractionation and quantification of SOM indicate that soils and sediments contain significant amounts of black carbon and kerogen of different origins. These particulate organic materials have rigid 3-dimensional structures and are often less polar compared to humic substances. Limited studies show that black carbon and kerogen exhibit nonlinear sorption for HOCs and may dominate the overall nonlinear sorption by soils and sediments.     

红壤中矿物表面对腐殖质吸附萘的影响

矿物表面可改变土壤腐殖质对疏水性有机污染物的结合能力。采用红壤和高岭石分别与胡敏酸结合制备得到的两种复合体对萘的吸附等温线非线性显著,其n=0.76或0.74,并且有机碳归一化吸附分配系数的实验值Koacds是采用Kow计算得出的理论值Koc的5倍以上,表明红壤、高岭石均对腐殖质吸附萘有强化作用,且红壤较之高岭石对腐殖质吸附萘的影响稍强些。主要原因是,红壤中除了高岭石外,还有与腐殖质结合力很强的铁氧化物,而且很可能是吸附态腐殖质组成结构形态发生了有利于对萘吸附的改变。     

Toluene sorption behavior on soil organic matter and its composition using three typical soils in China

The effect of soil organic matter (SOM) content and composition on sorption behavior of toluene for fluvo-aquic, red and black soils in China was investigated in batch experiments. Tested SOM was fractionated into two primary sorptive domains (‘soft’ and ‘hard’) to explain the dependence of sorption behavior on SOM composition. All the tested soils exhibited similar sorption kinetics and nonlinear sorption isotherms. Soils with high SOM content possessed a high sorptive capacity. Clay minerals also contributed to the sorptive capacity, especially for fluvo-aquic and red soils with low SOM content. In comparison, after removing most ‘soft’ SOM fraction from soils through hydrogen peroxide treatment, the residual ‘hard’ SOM fraction of three soil samples exhibited a slower sorption rate and a less sorption capacity compared to the untreated soil samples. The nonlinear degree of sorption was positively correlated with the content of ‘hard’ SOM for all soil samples. This is explained by the combined effect of SOM content and the composition on toluene sorption rates, sorption capacity and nonlinear degree of sorption of three typical soils in China.     

CBs在沉积物上的吸附-解吸行为

采用批量平衡实验,研究了氯苯、1,4-二氯苯、1,2,4-三氯苯和1,2,4,5-四氯苯4种氯苯类化合物（CBs）在含不同特性的自然有机质（NOM）的5种沉积物上的吸附．解吸行为。研究结果表明,所有吸附等温线均表现出明显的非线性和吸附-解吸滞后现象。1,2,4-三氯苯在不同沉积物上吸附等温线的非线性程度以及在沉积物上解吸滞后效应都随着沉积物NON聚合度的增加而增大。另外,CBs溶质分子本身的性质也影响着其在沉积物上的吸附．解吸性能。4种CBs在同一种沉积物上吸附等温线的非线性程度及其解吸滞后系数按氯苯、1,4-二氯苯、1,2,4-三氯苯、1,2,4,5-四氯苯的顺序依次减弱,说明CBs的分子尺寸越大,其在沉积物上的吸附非线性程度和解吸滞后现象也越弱。     

有机组分土-水分配系数的确定(英文)

有机组分的土水分配系数(Kd)是描述有机组分在地下系统中吸附特征的重要参数。同时,它也是物质运移模拟和环境评价中的主要参数之一。影响Kd的因素可概括为三个方面:土壤性质、有机组分本身特征及水相的物理化学性质。一般而言,对于非极性和弱极性有机组分,土壤中的有机质含量(foc )是影响Kd的最主要因素。但是,对于极性有机组分(POCs), 特别是在土壤有机质含量较低的情况下,土壤中矿物的种类和含量、水化学组分特征(pH、离子力等)经常在吸附过程中起重要作用。实验室内测定Kd的方法包括批实验和柱实验方法。批实验法适用于研究Kd较高情况下的吸附。在Kd较低的情况下,如低有机质土壤对极性有机污染物的吸附,土柱色谱法(SCC)是更适宜的选择。另外,可用土柱色谱法快速了解各种因素对吸附过程的影响,并获取详细的吸附和解吸信息。应用土柱色谱法时应当注意非平衡吸附和可能的柱堵塞问题。很多文献中提到结合柱实验和已有的吸附数据来预测土壤有机碳标准化的分配系数Koc(=Kd/foc)。但是,如果没有考虑吸附中特定的作用过程(如矿物吸附),对极性有机组分Koc的预测将会产生很大的误差。在环境评价中,将从一种土壤测定的Koc 应用到不同性质的土壤中,可能会导致错误的认识。在进行室内实验时,应把标准土(如Eurosoi     

Models of natural organic matter and interactions with organic contaminants

Adsorption of organic contaminants onto soils, sediments and other particulates has the potential to be a major controlling factor in their bioavailability, fate and behavior in the environment. Models for estimating the amount and stability of sorbed organic contaminants based on the fraction of organic carbon in a soil or sediment can oversimplify the process of sorption in the environment. In order to help understand sorption of organic contaminants in soils and sediments, we modeled various components of natural organic matter (NOM) that are possible substrates for sorption. These substrates include soot particles, lignin, humic and fulvic acids. The molecular scale interactions of selected aromatic hydrocarbons with different substrates were also simulated. Results of the simulations include the 3-D structures of the NOM components, changes in structure with protonation state and solvation and the sorption energy between PAH and substrate. This last parameter is an indicator of the amount of contaminant that will sorb and the energy required to free the contaminant from the substrate. Although the simulation results presented in this paper represent a first-order examination of NOM and contaminant interactions, the findings highlight a number of essential features that should be included in future molecular models of NOM and contaminant sorption.     

Distribution and sorption of potentially toxic metals in four forest soils from Hungary

Metals of natural and anthropogenic origin behave differently in soils mostly due to their different mobility. In this study, sequential extractions and batch sorption experiments were performed to relate the fractionation of native Ni, Cu, Zn and Pb to the sorption properties of added metals in four soils with contrasting physiochemical characteristics. A significant effect due to sample composition on both the mobility and sorption characteristics of these metals was found. The efficiency of soil components in metal immobilization was in the order of carbonate > organic matter > swelling clay minerals. The partitioning of native metals together with the information gained through the sorption isotherms allows a deeper insight on the fate and behavior of metals in soils with various compositions.     

Lead sorption onto thermally treated soil samples from Irbid

Open burning of waste at dumpsites sites may alter many physical and chemical properties of underlining soil layers including its ability to retard the migration of potential contaminants, such as lead, through the vadose zone. In this study, lead sorption onto soil samples from Irbid that were subjected to high temperatures has been investigated. These samples were collected from ground surface and heated to temperatures of 25, 70, 100, 200, 225, 250, 275, 300, 400, and 550°C. Based on these temperatures the soil was divided into ten different groups. Each group was first characterized by conducting a set of experiments to estimate the Atterberg limits (liquid limit, plastic limit, and plasticity index), the organic carbon content, and a set of batch experiments to study lead adsorption. Results indicate that the LL, PL, total organic carbon are slightly affected by high temperatures less than 200°C, show an abrupt change between temperature from 200 and 300°C, and then slight change above 300°C. Sorption of lead onto heated samples, however, was not significantly changed. This may be explained by the fact that adsorption of heavy metals mainly occurs onto the soil mineral parts which are slightly affected by the temperature range used in this study.