土壤和沉积物对多环芳烃吸附作用的研究进展

多环芳烃在土壤和沉积物上的吸附作用是影响其持留、分布、迁移转化及最终归趋的关键过程。本文阐述了土壤和沉积物对多环芳烃的吸附作用机理,分析了其影响因素及吸附作用对其他降解过程的影响,并探讨了所存在的主要问题及发展趋势。土壤/沉积物是一个复杂的多介质多界面体系,具有复杂的吸附活性中心,多环芳烃在其上的吸附是矿物成分和有机物质共同作用的结果而非单一的表面吸附过程或分配过程,因此形成了各式各样的吸附等温线。在吸附过程中,土壤和沉积物的粒度、有机质含量与组成、温度、pH以及被吸附多环芳烃的性质均是重要的影响因素。在多环芳烃吸附过程中,如何结合其定量结构性质、有机无机复合体的界面结构以及环境化学特征认识吸附机理是今后研究的一个趋势。     

干旱半干旱地区湖泊沉积物对Cu2+的吸附-解吸研究

吸附-解吸是重金属在沉积物中迁移转化的重要过程。本文研究干旱半干旱地区湖泊———乌梁素海不同区域沉积物对Cu2+的吸附-解吸过程。结果表明,吸附过程中,pH值逐渐降低;沉积物TOC含量越高,其对Cu2+的吸附能力也越强;生活污水和工业废水影响的S1样点及受农田退水影响的S2样点对Cu2+的吸附量相对较低,而相对较洁净的S3和S4样点具有较高的Cu2+吸附量。4个样点吸附量能力大小为S3>S4>S2>S1。解吸实验显示,沉积物吸附的Cu2+大部分都不能被解吸。试验结果符合Langmuir和Freundlich等温吸附方程,Langmuir方程的拟合效果要好于Freundlich方程,Langmuir方程拟合的饱和吸附量分别为3.31 mg/g、4.84 mg/g、8.39 mg/g和7.75 mg/g。     

溶解性有机物影响抗生素吸附的研究进展

不同环境中存在的抗生素会对人类的健康产生威胁。吸附法作为一种高效、简单的抗生素去除技术是目前的研究热点。然而，不同环境中普遍存在的溶解性有机物(Dissolved Organic Matter, DOM)会对抗生素的吸附过程产生影响。对人工合成材料体系(石墨烯和生物炭)和自然体系(土壤和底泥)中DOM对抗生素吸附过程的影响进行了梳理，同时总结了DOM影响抗生素吸附的机理，并对今后的研究趋势进行展望，以期能为环境中抗生素的吸附去除提供一定的参考。     

静态条件下持续时间对底泥中有机氯农药释放的影响

有机氯农药是广泛存在于环境中一类有机污染物，溶解度低，疏水性强，容易被颗粒物吸附，并随其在沉积物中积累，蓄积在沉积物中的有机氯农药在沉积物的再悬浮过程中会重新释放进入水体，造成二次污染。为了考察悬浮持续时间对沉积物中有机氟农药的释放的影响，采用沉积物释放模拟装置在60天内对微山湖沉积物中有机氯农药释放进行研究。结果表明，随着扰动时间的延长，上覆水中有机氯农药的含量在0—20天内增长很快，在60天左右含量趋于到稳定。不同的有机氟农药在扰动条件下，释放的速率和浓度是不一样的，其中水溶性大的农药更易向水体再次释放。     

重金属在沉积物系统中吸附行为的研究进展

本文综述了沉积物吸附重金属的研究进展，主要讨论了沉积物的表面特征，吸附过程的模拟，等温吸附模式及其影响因子等方面的问题。     

水环境中抗生素的污染现状及其去除方法研究进展

抗生素是用于防治人类和动物病菌性疾病,以及促进动物生长的一大类化学品.基于目前国内外大量使用抗生素的情况,本文针对抗生素对环境水体造成的污染,从环境水体中抗生素的来源入手,分析了抗生素在环境水体中的残留与污染水平.并讨论了目前国内外抗生素去除的研究情况,主要对常规处理技术、化学氧化、吸附3种手段进行了分析,最后对抗生素...     

兽药抗生素潜在生态效应及其环境行为

在集约化畜禽养殖过程中,兽药抗生素被广泛地作为饲料添加剂,用于预防和治疗动物疾病以及促进动物生长。本文介绍了兽药抗生素在国内外的发展形势及其随着畜禽粪便排出体外的抗生素在环境中的残留和生态效应。最后,论述了兽药抗生素在环境中的行为特征,并重点介绍了在土壤中的降解行为和吸附解吸特征。     

乌鲁木齐东道海子湖岸表层沉积物对氨氮的等温吸附特征研究

乌鲁木齐东道海子是乌鲁木齐河与头屯河下游的尾闾湖泊,东道海子水体氮素主要受放牧和采樵对荒漠植被破坏和农业排碱影响。而湖泊沉积物是湖泊水体污染物源汇关系中的重要介质,这些沉积物可能成为污染物运移转化的载体。本文通过野外采样与实验室模拟的方法,研究东道海子湖岸沉积物对氨氮的吸附特征。在吸附动力学特征中,准二级反应动力学达到极显著水平,沉积物Q_(max)变化范围在179~450mg/kg之间,平均值为238mg/kg,沉积物对氨氮的最终平衡时间在2h,均遵循先快后慢的规律,在前30min的吸附量基本已经与最终的吸附平衡浓度差别不大。在吸附热力学特征中,在低浓度条件下,对吸附浓度与吸附量进行拟合,Henry模型的拟合效果基本达到了显著水平,东道海子沉积物对氨氮吸附规律适用于低浓度吸附氨氮,在低浓度下Langmuir和Freundlich模型对数据没有达到显著水平,拟合效果不如Henry模型。     

调理吸附稳定法处理低含油沉积物

通过吸附、分散、固定等协同作用,可将沉积物中的有机物、重金属等污染物转化为不易溶解、不易迁移的状态。针对含油量5%、含水量60%的低含油、低含水污水池沉积物,调理吸附稳定技术可实现大规模、快速的处理。应用该技术处理孤岛某污水池底沉积物约8×103 m3,药剂投加量为沉积物质量的10%,强化养护时间≥3d,处理后沉积物含油量2%,浸出液的氨氮、pH值及石油类达到GB 8978—1996《污水综合排放标准》一级标准,COD去除率约80%。     

石油类污染物在土壤中的环境行为

土壤中石油类污染物的环境行为一直是环保界研究的重点。为此,简述了土壤中石油类污染物的来源、危害及存在状态,介绍了其在土壤中的迁移、吸附和降解行为,以及其行为特征和影响因素。全面了解土壤中石油类污染物的环境行为,对保护生态环境、推动石油工业的持续发展具有重要意义。     

Sorption and degradation of pesticides in nursery recycling ponds

Knowledge of pesticide distribution and persistence in nursery recycling pond water and sediment is critical for preventing phytotoxicity of pesticides during water reuse and to assess their impacts to the environment. In this study, sorption and degradation of four commonly used pesticides (diazinon, chlorpyrifos, chlorothalonil, and pendimethalin) in sediments from two nursery recycling ponds was investigated. Results showed that diazinon and chlorothalonil were moderately sorbed [K(OC) (soil organic carbon distribution coefficient) from 732 to 2.45 x 10(3) mL g(-1)] to the sediments, and their sorption was mainly attributable to organic matter content, whereas chlorpyrifos and pendimethalin were strongly sorbed (K(OC) > or = 7.43 x 10(3) mL g(-1)) to the sediments, and their sorption was related to both organic matter content and sediment texture. The persistence of diazinon and chlorpyrifos was moderate under aerobic conditions (half-lives = 8 to 32 d), and increased under anaerobic conditions (half-lives = 12 to 53 d). In contrast, chlorothalonil and pendimethalin were quickly degraded under aerobic conditions with half-lives < 2.8 d, and their degradation was further enhanced under anaerobic conditions (half-lives < 1.9 d). The strong sorption of chlorpyrifos and pendimethalin by the sediments suggests that the practice of recycling nursery runoff would effectively retain these compounds in the recycling pond, minimizing their offsite movement. The prolonged persistence of diazinon and chlorpyrifos, however, implies that incidental spills, such as overflows caused by storm events, may contribute significant loads of such pesticides into downstream surface water bodies.     

The role of condensed organic matter in the nonlinear sorption of hydrophobic organic contaminants by a peat and sediments

This study examines the effect of soil organic matter heterogeneity on equilibrium sorption and desorption of phenanthrene, naphthalene, 1,3,5-trichlorobenzene (1,3,5-TCB), and 1,2-dichlorobenzene (1,2-DCB) by soils and sediments. Two estuary sediments, a Pahokee peat (PP; Euic, hyperthermic Lithic Haplosaprist), and two subsamples (base- and acid-treated peat [TP] and acid-treated peat [FP]) of the peat were used as the sorbents. The contents of black carbon particles were quantified with a chemical extraction method. Petrographical examinations revealed the presence of the condensed soil and sediment organic matter (SOM) in Pahokee peat. The Freundlich isotherm model in two different forms was used to fit both sorption and desorption data. The results show that the sorption and desorption isotherms are generally nonlinear and that the apparent sorption-desorption hysteresis is present for phenanthrene and TCB. Detailed analysis of sorption data for the tested sorbent-sorbate systems indicates that black carbon is probably responsible for sorption isotherm nonlinearity for the two sediments, whereas the humic substances and kerogen may play the dominant role in nonlinear sorption by the peat. This investigation suggests that the microporosity of SOM is important for the hydrophobic organic contaminant (HOC) sorption capacity on the peat.     

Sorption kinetics of chlortetracyline and tylosin on sandy loam and heavy clay soils

Antibiotics may appear in the environment when manure, sewage sludge, and other organic amendments are added to soils. There is concern that the presence of antibiotics in soils may lead to the development of antibiotic-resistant bacteria which may spread to the rest of the environment. This paper aims at evaluating the sorption kinetics of two antibiotics frequently used in pig production. The results indicate that sorption of chlortetracycline (CTC) and tylosin (TYL) in sandy loam and clay occurs very fast. More than 95% of the CTC adsorption is completed within 10 min on both soils and of TYL within 3 h. These results suggest that 24-h soil and antibiotic solution mixtures is enough for sorption studies. Also, there is less likelihood that these antibiotics will leach through soil and appear in the ground water since their sorption on soils is very high unless they are carried by soil particles through preferential flow. There was also no effect of soil sterilization on sorption kinetics of these antibiotics thus suggesting that there is minimal probability of the antibiotics degrading by microorganisms during 24- to 48-h adsorption studies.     

Phosphorus sorption characteristics of estuarine sediments under different redox conditions

Phosphorus (P) plays a major role in eutrophication of aquatic systems. Estuarine sediments could function as sources or sinks for P to the overlying water column depending upon their physico-chemical characteristics. Understanding of P sorption phenomena in estuarine sediments is important in regulating the P availability in estuaries. Phosphorus sorption characteristics of sediments from the Indian River Lagoon, Florida, USA, were determined to examine the role of selected physico-chemical properties of the sediments on soluble reactive P status in estuary water. Mean equilibrium P concentrations (EPCo) of 0.75 mg L(-1) and mean P sorption maxima (Smax) of 32.2 mg kg(-1) were obtained under anaerobic conditions, compared with EPCo of 0.05 mg L(-1) and Smax of 132.7 mg kg(-1) under aerobic conditions. The higher EPCo values under anaerobic conditions and the greater Smax values under aerobic conditions were associated with amorphous and poorly crystalline iron. These results suggest that sediments enriched with amorphous and poorly crystalline forms of iron act as an excellent reservoir for P by adsorbing excessive P in aerobic sediment zones and releasing it upon burial under anaerobic conditions. This study also indicates that P compounds in sediments independently maintain equilibrium with P in solutions. Thus, heterogeneous systems like soil and sediment simply behave as a mixture of homogeneous surfaces as far as their P sorption characteristics are concerned, and hence can be successfully described by the Langmuir and Freundlich models.     

The influence of lipids on the energetics of uptake of polycyclic aromatic hydrocarbons by natural organic matter

Although most of the organic carbon in soils and sediments may be composed of humic substances, their interaction with other compounds, especially their sorption interactions, may be significantly affected by the presence of small amounts of the other components of natural organic matter (NOM). In this investigation, the influence of the lipid fraction of NOM on the sorption thermodynamics of fluorene, phenanthrene, and pyrene to several geosorbent samples was examined before and after extraction of lipids. Batch experiments were performed at the same concentration for all polycyclic aromatic hydrocarbons (PAHs) (0.025 x their solubility in water) at different temperatures (10, 20, 30, and 40 degrees C), and the thermodynamic parameters were calculated. Removal of the lipids increases the sorption capacity of the samples as well as the exothermicity of the process. The free energy change was negative for all the samples and no significant differences were noticed on lipid removal. The entropy changes were small and positive for the whole geosorbent samples, but even smaller or more negative when the lipids were removed. This indicates that the interaction of PAHs with soils and sediments in the absence of extractable lipids is stronger and the mechanisms involved may be different, changing from a partitioning-like mechanism to specific adsorption. Because of the competition between lipids and PAHs for the same sorption sites, the lipids can be viewed as an "implicit sorbate."     

Nonlinear and competitive sorption of apolar compounds in black carbon-free natural organic materials

Numerous studies have reported a spectrum of sorption phenomena in soils, sediments, and organic matter isolates of those materials that are inconsistent with a partition model proposed in the late 1970s and early 1980s, a model predicated on a hypothesis that sorption is linear and noncompetitive. To explain these nonideal phenomena, prior studies have proposed a hard-soft (glassy-rubbery) model for SOM (soil and sediment organic matter), while others have attributed them singularly to BC (black carbon: soot and charcoal) particles present in topsoils and sediments. In this study, we demonstrated nonideal sorption behavior (isotherm nonlinearity, competitive effects) for a group of apolar compounds in a large set of natural and model organic materials, including a commercial lignin and humic acids from different sources. Complete oxidation of samples by an acidic dichromate method was taken to signify the absence of BC. (However, polymethylene units are stable even if functionalized on both ends, making the technique unreliable for quantifying BC.) Other samples were inferred free of BC by their source and method of preparation. Characterization by thermalanalytical methods indicated the glassy character of the organic materials. The origin of the nonideal behaviors appears to be the glassy character of these materials. Sorption nonlinearity increased or decreased by changing temperature, cosolvent content, or degree of cross-linking by metal ions as predicted for organic solids in a glassy state. We conclude that macromolecular humic substances in the environment may exhibit nonideal sorption behavior in soils and sediments, quite apart from any such behaviors attributable to BC.     

Sorption studies of mixed chromium and chlorinated ethenes at the field and laboratory scales

The sorption and desorption behavior of hexavalent chromium and chlorinated ethenes in a sandy ground water aquifer with a low reduction capacity was evaluated by performing a variety of analyses and experiments at the laboratory (batch and column studies) and field (in situ injection-withdrawal experiment) scales. The partitioning coefficients determined from the field and laboratory experiments are generally similar. Both sets of experiments yielded relatively low partition coefficients for chromium and chlorinated ethenes. The column studies and injection-withdrawal experiment indicate that chromium has the potential to leach from aquifer sediments and act as a secondary source of contamination. However, the magnitude of the secondary source effect is not significant due to low concentrations of leachable contamination. The chromium sorption isotherm data were also simulated using the triple layer surface complexation model (TLM). The isotherm data were modeled using the TLM, illustrating the applicability of geochemical modeling for sorption of chromium to these sediments under variable pE-pH conditions.     

Effect of heat treatment on sorption of polar and nonpolar compounds to montmorillonites and soils

Batch sorption isotherms of 1,3,5-trichlorobenzene, 1,3,5-trinitrobenzene, and tetracycline to organic-free montmorillonites and soils receiving heat treatment (375°C for 24 h) were compared with those to unheated sorbents. Sorption of the nonpolar 1,3,5-trichlorobenzene to soil was lowered after the removal of humus by heating, consistent with the mechanism of hydrophobic partition into organic matter. For 1,3,5-trinitrobenzene, the enhanced sorption to heated soils was attributed to specific interactions with exchangeable cations facilitated by heating-induced irreversible partial dehydration of the clay interlayer. For tetracycline, an additional mechanism for sorption enhancement could be due to increased exposure of strong complexation sites on clay minerals after removal of the humic coating. These hypotheses were supported by the sorption data to heated and unheated Na-, K-, and Cs-saturated montmorillonites. The combustion method is commonly adopted to measure the content of black carbon in soils and sediments. However, findings from the present study indicate that combustion may greatly modify the structural properties of clay minerals, leading to misinterpreted sorption contributions of different soil components to sorption of polar or ionic compounds.     

Anionic polyacrylamide effects on soil sorption and desorption of metolachlor,atrazine, 2,4-D,and picloram

Polyacrylamide (PAM) treatment of irrigation water is a growing conservation technology in irrigated agriculture in recent years. There is a concern regarding the environmental impact of PAM after its application. The effects of anionic PAM on the sorption characteristics of four widely used herbicides (metolachlor, atrazine, 2,4-D, and picloram) on two natural soils were assessed in batch equilibrium experiments. Results showed that PAM treatment kinetically reduced the sorption rate of all herbicides, possibly due to the slower diffusion of herbicide molecules into interior sorption sites of soil particles that were covered and/or cemented together by PAM. The equilibrium sorption and desorption amounts of nonionic herbicides (metolachlor and atrazine) were essentially unaffected by anionic PAM, even under a high PAM application rate, while the sorption amounts of anionic herbicides (2,4-D and picloram) were slightly decreased and their desorption amounts increased little. The impact mechanisms of PAM were related to the molecular characteristics of PAM and herbicides. The negative effects of PAM on the sorption of anionic herbicides are possibly caused by the enhancement of electrostatic repulsion by presorbed anionic PAM and competition for sorption sites. However, steric hindrance of the large PAM molecule weakens its influence on herbicide sorption on interior sorption sites of soil particles, which probably leads to the small interference on herbicide sorption, even under high application rates.     

Phosphorus export from an agricultural watershed: linking source and transport mechanisms

Many source and transport factors control P loss from agricultural landscapes; however, little information is available on how these factors are linked at a watershed scale. Thus, we investigated mechanisms controlling P release from soil and stream sediments in relation to storm and baseflow P concentrations at four flumes and in the channel of an agricultural watershed. Baseflow dissolved reactive phosphorus (DRP) concentrations were greater at the watershed outflow (Flume 1; 0.042 mg L(-1)) than uppermost flume (Flume 4; 0.028 mg L(-1)). Conversely, DRP concentrations were greater at Flume 4 (0.304 mg L(-1)) than Flume 1 (0.128 mg L(-1)) during stormflow. Similar trends in total phosphorus (TP) concentration were also observed. During stormflow, stream P concentrations are controlled by overland flow-generated erosion from areas of the watershed coincident with high soil P. In-channel decreases in P concentration during stormflow were attributed to sediment deposition, resorption of P, and dilution. The increase in baseflow P concentrations downstream was controlled by channel sediments. Phosphorus sorption maximum of Flume 4 sediment (532 mg kg(-1)) was greater than at the outlet Flume 1 (227 mg kg(-1)). Indeed, the decrease in P desorption between Flumes 1 and 4 sediment (0.046 to 0.025 mg L(-1)) was similar to the difference in baseflow DRP between Flumes 1 and 4 (0.042 to 0.028 mg L(-1)). This study shows that erosion, soil P concentration, and channel sediment P sorption properties influence streamflow DRP and TP. A better understanding of the spatial and temporal distribution of these processes and their connectivity over the landscape will aid targeting remedial practices.