Setting information priorities for remediation decisions at a contaminated-groundwater site.

Many sites of contamination due to inappropriate disposal of hazardous materials or wastes have been found. These sites have the potential of damaging the environment and human health and thus need to be evaluated as to whether and what actions should be initiated. In the decision on whether a contaminated site should be subject to management, the knowledge concerning important parameters that would influence the decision will be beneficial to planning of data collection to support the decision. This paper presents a case study of contaminated site located in northern Taiwan, where the groundwater is contaminated by chlorinated hydrocarbons including trichloroethylene (TCE) and tetrachloroethylene (PCE). A site-specific multimedia risk assessment is performed to estimate the total risk resulting from the contamination. In addition, Monte Carlo simulation, rank correlation coefficients, and decision criteria are combined to develop a methodology for assessing the important of parameters in terms of their influence on the decision. It is found that TCE concentration, vegetable yield, deposition interception fraction of vegetables, and plant surface loss constant, are the four parameters important to the decision-making of the case problem.     

关于制定地下水修复目标上限值 (风险管制值) 的建议

修复目标值是评判场地修复是否合格以及修复后地块能否安全利用的唯一标准,因此制定合理的修复目标值对于污染场地修复治理和安全利用起着至关重要的作用。大部分污染场地需要同时进行土壤和地下水修复,生态环境部发布了《建设用地土壤污染修复目标值制定指南 (试行) 》,然而地下水修复目标值制定的指南标准尚未发布。少数项目制定的地下水修复目标值过于宽松,无法保障地块的风险可控和安全利用。因此,建议借鉴土壤环境管理的思路,制定一个类似于“土壤管制值”的“地下水修复目标上限值 (风险管制值) ”。该值的制定不能只基于风险评估计算的结果,而应充分考虑每种污染物各自的理化性质、迁移转化归趋机制、环境赋存特征、健康和环境风险、国外同类标准的取值、检测方法的准确度和成本、经济社会承受能力等因素,力争做到合规合法、科学严谨、综合平衡。     

Using stochastic risk assessment in setting information priorities for managing dioxin impact from a municipal waste incinerator

The objectives of this study were to assess site-specific carcinogenic risk of incinerator-emitted dioxins in a manner reflecting pollutant transfer across multimedia and multi-pathways. The study used site-specific environmental and exposure information and combined the Monte Carlo method with multimedia modeling to produce probability distributions of risk estimates. The risk estimates were further categorized by contaminated environmental media and exposure pathways that are experienced by human receptors in order to pinpoint significant sources of risk. Rank correlation coefficients were also calculated along with the Monte Carlo sampling to identify key factors that influenced estimation of risk. The results showed that ingestion accounted for more than 90% of the total risk and that risk control on ingestion of eggs, aboveground vegetables, and poultry should receive priority. It was also found that variation of parameters with variability accounted for around 35% of the total risk variance, while uncertainty contributed to the remaining 65%. Intake rates of aboveground vegetables, eggs, and poultry were the key parameters with the largest contribution to variance. In addition, sufficient sampling and analysis of dioxin contents in eggs, aboveground vegetables, poultry, soil, and fruit should be performed to improve risk estimation because the variation in concentrations in these media accounted for the largest overall risk variance. Finally, focus should be placed on reduction of uncertainty associated with the risk estimation through ingestion of aboveground vegetables, eggs, poultry, fruit, and soil because the risk estimates associated with these exposure pathways had the largest variance.     

PCB remediation in schools: a review

Growing awareness of polychlorinated biphenyls (PCBs) in legacy caulk and other construction materials of schools has created a need for information on best practices to control human exposures and comply with applicable regulations. A concise review of approaches and techniques for management of building-related PCBs is the focus of this paper. Engineering and administrative controls that block pathways of PCB transport, dilute concentrations of PCBs in indoor air or other exposure media, or establish uses of building space that mitigate exposure can be effective initial responses to identification of PCBs in a building. Mitigation measures also provide time for school officials to plan a longer-term remediation strategy and to secure the necessary resources. These longer-term strategies typically involve removal of caulk or other primary sources of PCBs as well as nearby masonry or other materials contaminated with PCBs by the primary sources. The costs of managing PCB-containing building materials from assessment through ultimate disposal can be substantial. Optimizing the efficacy and cost-effectiveness of remediation programs requires aligning a thorough understanding of sources and exposure pathways with the most appropriate mitigation and abatement methods.     

Suitability of Scirpus maritimus for petroleum hydrocarbons remediation in a refinery environment

Purpose  

In the ambit of a project searching for appropriate biological approaches for recovering a refinery soil contaminated with petroleum hydrocarbons (PHC), we compared results obtained in the absence and in the presence of the salt marsh plant Scirpus maritimus or Juncus maritimus or an association of these two plants, which were tested in the refinery environment. Synergistic effects caused by addition of a non-ionic surfactant and/or a bioaugmentation product were also investigated. Major challenges of this study were: field conditions and weathered contamination.     

Development of a biobarrier for the remediation of PCE-contaminated aquifer

The industrial solvent tetrachloroethylene (PCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to develop a biobarrier system, which includes a peat layer to enhance the anaerobic reductive dechlorination of PCE in situ. Peat was used to supply primary substrate (electron donor) continuously. A laboratory-scale column experiment was conducted to evaluate the feasibility of this proposed system or PCE removal. This experiment was performed using a series of continuous-flow glass columns including a soil column, a peat column, followed by two consecutive soil columns. Anaerobic acclimated sludges were inoculated in all three soil columns to provide microbial consortia for PCE biodegradation. Simulated PCE-contaminated groundwater with a flow rate of 0.25 l/day was pumped into this system. Effluent samples from each column were analyzed for PCE and its degradation byproducts (trichloroethylene (TCE), cis-dichloroethylene (cis-DCE), vinyl chloride (VC), ethylene (ETH), and ethane). Results show that the decrease in PCE concentrations and production of PCE byproducts were observed over a 65-day operating period. Up to 98% of PCE removal efficiency was obtained in this passive system. Results indicate that the continuously released organics from peat column enhanced PCE biotransformation. Thus, the developed biobarrier treatment scheme has the potential to be developed into a cost-effective in situ PCE-remediation technology, and can be utilized as an interim step to aid in system scale-up.     

Modified nanoscale zero-valent iron in persulfate activation for organic pollution remediation: a review

Environmental Science and Pollution Research - Under the action of different activators, persulfate can produce sulfate radicals (SO4·–) with strong oxidizing ability, which can destruct...     

重金属污染土壤植物修复及进展

土壤污染是当今面临的一个重要环境问题。常规的土壤污染物理化学治理技术 ,如客土换土法、冲洗法、热处理、固化、玻璃化、动电修复法等 ,由于其技术要求高或经济成本高昂 ,对土壤结构的扰动破坏较严重 ,因而 ,大规模推广应用存在较大问题。重金属超累积植物的不断发现 ,使人们认识到有可能利用植物于土壤污染的治理修复。自 2 0世纪 90年代起 ,植物修复成为环境污染治理研究领域的一个前沿性课题。研究表明 ,通过植物的吸收、挥发、根滤、稳定等作用 ,可以净化土壤或水体中金属污染物 ,达到净化环境的目的。近 10年来 ,在超累积植物的找寻培育、植物根际微生物共存体系研究、植物对重金属的耐忍性、超量吸收及其解毒机制以及植物修复的工艺技术方面已有不少研究 ,并取得长足的进展 ,现代分子生物学的发展以及基因工程技术的应用有可能使植物修复技术取得根本性的突破。     

Use of abiotic oxidative-reductive technologies for remediation of munition contaminated soil in a bioslurry reactor

The possibility to clean-up TNT contaminated soil, 400 mg TNT kg-1, surrounding Nebraska Ordnance Plant's (US), below the USEPA goal of 17.2 mg TNT kg-1 using Fenton oxidation (Fe2+ + H2O2), Fe0 reduction, combined Fe0/H2O2 and CaO2 was explored at pilot scale. Treatments were performed in a 60 l airlift reactor, which was a prototype of larger commercial unit. All the treatments reduced TNT soil concentration below the required clean-up goal and in shorter time with respect to bench scale. Using 2% (w/w) Fe0, TNT soil concentration reduced below the required standard just within 4 h. No significant TNT destruction improvement was observed when 2% Fe0 (w/w soil) was combined with four sequential additions of 0.25% H2O2. Laboratory experiments with 14C-TNT indicated that most of the 14C, approximately 80%, was unextractable residue. A time greater than 24 h was required either with Fenton reagent, 8 x (80 mg Fe2+ L-1 + 0.125% H2O2) or 0.2% (w/w) CaO2. The optimal performance of Fenton reagent was obtained when the reagent was added in eight increments rather than in a single or double dose and less cumulative amount of H2O2 (0.75%) was required with respect to bench scale (1%).     

Ability of salt marsh plants for TBT remediation in sediments

Introduction  

The capability of Halimione portulacoides, Spartina maritima, and Sarcocornia fruticosa (halophytes very commonly found in salt marshes from Mediterranean areas) for enhancing remediation of tributyltin (TBT) from estuarine sediments was investigated, using different experimental conditions.     

Hydraulic characterization for steam enhanced remediation conducted in fractured rock

To explore the viability of Steam Enhanced Remediation (SER) in fractured rock a small-scale steam injection and water/vapour extraction pilot study was conducted at the former Loring Air Force Base in northern Maine, USA. A detailed well testing program was undertaken to assist in the design of the injection and extraction well array, and to assess the possibility of off-site heat and contaminant migration. A structurally complex limestone having low matrix porosity and a sparse distribution of fractures underlies the study site. To characterize the groundwater and steam flow pathways, single-well slug tests and more than 100 pulse interference tests were conducted. The results of the well testing indicate that the study site is dominated by steeply dipping bedding plane fractures that are interconnected only between some wells in the injection/extraction array. The SER system was designed to take advantage of interconnected fractures located at depth in the eastern end of the site. An array of 29 wells located in an area of 60 by 40 m was used for steam injection and water/vapour extraction. The migration of heat was monitored in several wells using thermistor arrays having a 1.5 m vertical spacing. Temperature measurements obtained during and after the 3 month steam injection period showed that heat migration generally occurred along those fracture features identified by the pulse interference testing. Based on these results, it is concluded that the pulse interference tests were valuable in assisting with the design of the injection/extraction well geometry and in predicting the migration pathways of the hot water associated with the steam injection. The pulse interference test method should also prove useful in support of any other remedial method dependant on the fracture network for delivery of remedial fluid or extraction of contaminants.     

水中有机污染物电化学清除的研究进展

介绍利用直接电解发、间接电解和电化学吸附等方法去除水中有机污染物的研究现状,并指出今后的工作方面。     

次级河流水污染事件应急处置程序及环境损害评估技术路线

近年来,随着我国经济的发展,次级河流突发性水污染事件频繁发生,对生态环境及居民生活造成了严重的影响。次级河流突发性水污染事件发生后,为减少污染造成的损失和影响,保证受损的环境资源得到恢复和补偿,不仅要立即采取行之有效的应急处置措施,而且应当积极开展环境损害鉴定评估工作,全面追究污染者的环境责任。根据次级河流本身的特点,结合各省市在环境应急处置过程中的具体做法,建立了一套应对突发性次级河流水污染事件的应急处置工作程序;阐述了环境损害鉴定评估的必要性、工作方法和技术路线,同时从受损环境资源的确认、污染源和污染物的识别以及暴露途径的建立3个方面构建了开展次级河流突发性水污染事件环境损害鉴定评估工作的因果关系链条,对实际开展相关工作具有重要意义。     

Geostatistics as a validation tool for setting ozone standards for durum wheat

Which is the best standard for protecting plants from ozone? To answer this question, we must validate the standards by testing biological responses vs. ambient data in the field. A validation is missing for European and USA standards, because the networks for ozone, meteorology and plant responses are spatially independent. We proposed geostatistics as validation tool, and used durum wheat in central Italy as a test. The standards summarized ozone impact on yield better than hourly averages. Although USA criteria explained ozone-induced yield losses better than European criteria, USA legal level (75 ppb) protected only 39% of sites. European exposure-based standards protected ≥90%. Reducing the USA level to the Canadian 65 ppb or using W126 protected 91% and 97%, respectively. For a no-threshold accumulated stomatal flux, 22 mmol m⁻² was suggested to protect 97% of sites. In a multiple regression, precipitation explained 22% and ozone explained <0.9% of yield variability.     

Microbial fuel cell system: a promising technology for pollutant removal and environmental remediation

Environmental Science and Pollution Research - The microbial fuel cell (MFC) system is a promising environmental remediation technology due to its simple compact design, low cost, and renewable...     

Sources and remediation for mercury contamination in aquatic systems--a literature review

Sources of mercury contamination in aquatic systems were studied in a comprehensive literature review. The results show that the most important anthropogenic sources of mercury pollution in aquatic systems are: (1) atmospheric deposition, (2) erosion, (3) urban discharges, (4) agricultural materials, (5) mining, and (6) combustion and industrial discharges. Capping and dredging are two possible remedial approaches to mercury contamination in aquatic systems, and natural attenuation is a passive decontamination alternative. Capping seems to be an economical and effective remedial approach to mercury-contaminated aquatic systems. Dredging is an expensive remedial approach. However, for heavily polluted systems, dredging may be more effective. Natural attenuation, involving little or no cost, is a possible and very economical choice for less contaminated sites. Proper risk assessment is necessary to evaluate the effectiveness of remedial and passive decontamination methods as well as their potential adverse environmental effects. Modeling tools have a bright future in the remediation and passive decontamination of mercury contamination in aquatic systems. Existing mercury transport and transformation models were reviewed and compared.     

Use of CALPUFF for exposure assessment in a near-field,complex terrain setting

CALPUFF is an atmospheric source-receptor model recommended by the U.S. Environmental Protection Agency for use on a case-by-case basis in complex terrain and wind conditions. The ability of the model to provide useful information for exposure assessments in areas with those topographical and meteorological conditions has received little attention. This is an important knowledge gap for use of CALPUFF outside of regulatory applications, such as exposure analyses conducted in support of risk assessments and health studies. We compared deposition of cadmium (Cd), lead (Pb), and zinc (Zn) calculated with CALPUFF as a result of emissions from a zinc smelter with corresponding concentrations of the metals measured in attic dust and soil samples obtained from the surrounding area. On a point-by-point analysis, predictions from CALPUFF explained 11% (lead) to 53% (zinc) of the variability in concentrations measured in attic dust. Levels of heavy metals in soil interpolated to 100 residential addresses from the distribution of concentrations measured in soil samples also agreed well with deposition predicted with CALPUFF: R² of 0.46, 0.76, and 079 for Pb, Cd, and Zn, respectively. Community-average concentrations of Cd, Pb, and Zn measured in soil were significantly (p < 0.0001) and strongly correlated (R² ranged from 0.77 to 0.98) with predicted deposition rates. These findings demonstrate that CALPUFF can provide reasonably accurate predictions of the patterns of long-term air pollutant deposition in the near-field associated with emissions from a discrete source in complex terrain. Because deposition estimates are calculated as a linear function of air concentrations, CALPUFF is expected to be reliable model for prediction of long-term average, near-field ambient air concentrations in complex terrain as well.     

焦化厂污染土壤堆肥修复过程的毒性变化

以北京某焦化厂污染土壤为研究对象,按照5∶1的比例添加锯末后加入5%的草炭进行好氧堆肥,通过对污染土壤堆肥处理过程中16种PAHs的降解率、CAT值、SOM值、土壤毒性、pH和TN值的变化规律进行比较,研究添加草炭好氧堆肥对实际有机污染土壤中PAHs的降解效果。研究结果表明,(1)添加草炭好氧堆肥能有效降解有机污染土壤中PAHs,堆肥49 d后,EPA优控的16种PAHs总值从1 085.42 mg/kg降低到71.10 mg/kg,总降解率为93.27%。(2)焦化厂土壤中PAHs浓度较高的分别为荧蒽、菲、芴、苯并(a)蒽、芘、蒽和苯并(k)荧蒽,它们的和占Σ16PAHs总量的73.56%,其中荧蒽的含量最高,浓度为186.913 mg/kg。这7种PAHs的经过49 d添加草炭堆肥后降解率分别为95.67%、93.52%、92.22%、93.12%、93.01%、95.19%和96.24%。(3)通过有机质值和Σ16PAHs总量作图发现,有机质值和Σ16PAHs总量有一定的相关性,这表明在堆肥过程中,微生物在PAHs降解过程中起到很大的作用。     

The use of anthracene as a model compound in a comparative study of hydrous pyrolysis methods for industrial waste remediation

Polycyclic aromatic hydrocarbons are very stable compounds and tend to bioaccumulate in the environment due to their high degree of conjugation and aromaticity. Hydrous pyrolysis is explored as a technique for the treatment of industrial water containing PAH, using anthracene as a model compound. The reactivity of anthracene under a range of temperatures and durations are studied in this paper. Aliquots of 1.0-10.0 mg of anthracene in a range of 1.0-5.0 mL of H₂O are subjected to hydrous pyrolysis under varied conditions of temperature, reagents and duration. The conditions include oxidising systems comprising distilled water, hydrogen peroxide and Nafion-SiO₂ solid catalyst in water; and reducing systems of formic acid and formic acid/Nafion-SiO₂/Pd-C catalysts to assess a range of redox reaction conditions. Oxygen in air played a role in some of the reaction conditions. Pyrolysed products were identified and quantified by the use of Gas Chromatography-Mass Spectrometry (GC-MS). The major products were anthrone, anthraquinone, xanthone from oxidation; and multiple hydro-anthracene derivatives from reductive hydogenation. The nature of reaction conditions influenced the extent of anthracene degradation. The products formed are more reactive (less stable) as compared to anthracene the starting material and will therefore be less persistent in the environment.     

Solanum nigrum L. weed plants as a remediation tool for metalaxyl-polluted effluents and soils

In this work, the phytoremediation potential of metalaxyl, a commonly used persistent, mobile and leachy fungicide, by Solanum nigrum L. plants was studied. The study revealed that this plant species can be used as an excellent metalaxyl phytoremediation tool, thus providing a cost effective and environmentally friendly clean technology for the decontamination of sites and effluents. As it can be sowed directly in the remediation site, is able to complete its life cycle without suffering major stress. Because it accumulates high amounts of the fungicide in the aboveground tissues, enables its concentration and proper disposal by cutting off the corresponding plant part. The study also suggests that the tolerance to metalaxyl is due to a suitable antioxidant response comprising proline accumulation and guaiacol peroxidase and glutathione-S-transferase enhanced activities, that reduce oxidative damage to the plant organs.