PRB技术在地下水污染修复中的研究进展

在综合分析可渗透反应墙（PRB）修复污染技术基础上,提出了存在问题及发展趋势,进而理出需通过深入研究,提高修复系统性能及其可行途径。预计在不远的将来,PRB处理工艺的持续性也同样会有大幅度改进和发展。     

地下水渗透反应格栅技术发展综述

面对日益严重的地下水污染,地下水渗透反应格栅技术作为一种原位、简易、被动技术在地下水污染修复中被广泛研究和应用。依据渗透反应格栅技术的定义及发展历程,渗透反应格栅技术的发展大致可以分为2个阶段,即2000年以前的传统零价铁渗透反应格栅阶段和2000年以后的新型复合介质渗透反应格栅阶段。伴随地下水污染形势的日益复杂化,以及渗透反应格栅技术的不断应用和材料科学等其他学科的飞速发展,未来渗透反应格栅技术的发展将主要集中于复合介质与新介质的开发、组合式渗透反应格栅技术的研发、渗透反应格栅技术与其他修复技术的联用以及渗透反应格栅工程的长期监测及管理。     

珠江三角洲地区地下水污染调查内容综述

地下水污染问题得到我国政府的高度重视,珠江三角洲地区地下水污染调查评价于2005年展开实施,简要综述该区地下水污染调查内容,主要包括：污染源调查、地下水污染现状调查、水土测试指标的选取以及采样点的控制等。     

地下水污染风险评价的迭置指数法研究综述

目前,我国大部分城市采用地下水作为饮用水源,而地下水污染状况日益严重,地下水污染风险评价作为管理者制定污染防治方案的一种手段,显得尤为重要。地下水污染风险评价虽然已经有一定范围的应用,但对其概念并没有统一的定义,因此,在总结国内外地下水污染风险评价研究进展的基础上,提出地下水污染风险的定义,并重点讨论迭置指数法在地下水污染风险评价中的应用,并在此基础上提出存在的问题及建议。     

Development of modified flyash as a permeable reactive barrier medium for a former manufactured gas plant site, Northern Ireland

A sequential biological permeable reactive barrier (PRB) was determined to be the best option for remediating groundwater that has become contaminated with a wide range of organic contaminants (i.e., benzene, toluene, ethylbenzene, xylene and polyaromatic hydrocarbons), heavy metals (i.e., lead and arsenic), and cyanide at a former manufactured gas plant after 150 years of operation in Portadown, Northern Ireland. The objective of this study was to develop a modified flyash that could be used in the initial cell within a sequential biological PRB to filter complex contaminated groundwater containing ammonium. Flyash modified with lime (CaOH) and alum was subjected to a series of batch tests which investigated the modified cation exchange capacity (CEC) and rate of removal of anions and cations from the solution. These tests showed that a high flyash composition medium (80%) could remove 8.65 mol of ammonium contaminant for every kilogram of medium. The modified CEC procedure ruled out the possibility of cation exchange as the major removal mechanism. The medium could also adsorb anions as well as cations (i.e., Pb and Cr), but not with the same capacity. The initial mechanism for Pb and Cr removal is probably precipitation. This is followed by sorption, which is possibly the only mechanism for the removal of dichromate anions. Scanning electron microscopic analysis revealed very small (<1 μm) cubic highly crystalline precipitates on the flyash, although this new crystalline zeolite growth did not occur rapidly enough to enable productive zeolite formation. Surface area measurements showed that biofilm growth on the medium could be a major factor in the comparative reduction of surface area between real and synthetic contaminant groundwaters. The modified flyash was found to be a highly sorptive granular material that did not inhibit microbiological activity, however, leaching tests revealed that the medium would fail as a long-term barrier material.     

牡蛎壳改性及联合释氧复合材料修复地下水氨氮污染实验研究

为研究以牡蛎壳-释氧复合材料为填料的渗透反应格栅去除地下水氨氮污染的效果及其经济实用性,开展了相关室内实验:采用高温加热方式对牡蛎壳进行改性,通过测定牡蛎壳改性后的比表面积判定其吸附效果;以过氧化钙为释氧化合物,将其与水泥、石英砂/牡蛎壳粒、钙基膨润土以一定比例混合制成粒径约1.8 cm球型释氧材料,采用静态实验研究不同原料配比的释氧材料的释氧性能;最后研究了两种不同粒径牡蛎壳粒-释氧复合材料修复地下水氨氮的效果及不同供氧方式下不同吸附材料修复地下水氨氮的效果及其经济实用性。结果表明:对牡蛎壳粒进行高温改性,牡蛎壳粒高温条件下会产生团聚现象,比表面积随煅烧温度升高呈下降趋势,高温改性方式并不能有效改善牡蛎壳粒吸附性能;实验中制作的释氧材料在95天的实验期间,各实验柱的溶解氧量可以保持在18 mg/L左右,且在嗜碱菌作用下pH值得以有效降低,所制作的释氧材料可为硝化细菌长期在溶解氧低的地下水环境中生长提供氧气;以牡蛎壳-释氧复合材料为填料的渗透反应格栅通过耐碱硝化细菌的硝化作用可以将氨氮浓度从50 mg/L降至约35 mg/L,不同粒径牡蛎壳粒修复效果差异不明显。使用牡蛎壳-释氧复合材料渗透反应格栅长期修复地下水氨氮,不仅可以达到活性炭及沸石作为骨架的修复效果,而且更加具有经济实用性。     

海底地下水排泄研究回顾与进展

海底地下水排泄是全球水循环的重要组成部分,是近岸、滩涂和河口地区典型而重要的海水—地下水相互作用过程。作为全球水循环的重要组成部分,海底地下水排泄是海洋中水和各种化学物质的重要来源之一,同时也是各种污染物从陆地向海洋输送的一个重要而隐蔽的通道。综述了海底地下水排泄(SGD)的研究现状与进展,对海底地下水排泄的过程、研究方法、研究分布以及环境意义等方面进行了详细介绍,指出了目前研究存在的不足和需要努力的方向,从而为我国开展大规模海底地下水排泄研究提供了一定的思路。     

~(15)N Isotope Used for Study of Groundwater Nitrogen Pollution in Shijiazhuang City, China

Shijiazhuang City is the capital of Hebei province, China. Groundwater is the major water supply source for living and industry need of the city. Due to a rapid increase of population and development of industry and agriculture, a series of groundwater environmental problems are created. In the paper, the situation of groundwater pollution in Shijiazhuang city is reported. Based on the groundwater chemical data and ~(15)N measurement results both on groundwater and soils, the reason of groundwater nitrate pollution is studied.     

Ecohydrology of Groundwater Dependent Ecosystems: A Review

Groundwater Dependent Ecosystems (GDEs) are ecosystems that must have access to groundwater to maintain their ecological structure and function. In other words, the vegetation dynamics moisture dynamics, and water-salt balance in GDEs are significantly affected by and directly related to the groundwater. This work reviews the most recent research advances in the ecohydrology of GDEs from: ①the interactions between groundwater and vegetation, ②the interactions between groundwater and soil moisture dynamics in the vadose zone, the interactions between ground and ③surface-water systems, ④the interactions between groundwater and salt accumulation dynamics, ⑤the responses of GDEs to climate changes and human disturbances, and ⑥the ecohydrological modeling works toward sustainable management of GDEs. It is pointed out that several issues need to be taken into account in the managements of GDEs, i.e., how does the vegetation of GDEs response to fluctuations and decreases in the groundwater level, whether there is a catastrophic loss of the functions of GDEs, and what is the threshold value below which such a catastrophe may occur. The key to solving those issues lies in how to delineate the different ecohydrological processes occurred in the soil medium from the top of the ground surface to the water table. Therefore, observation and modeling efforts are needed and will be important research priorities in the future, especially for GDEs in arid environments. We also argued that four more difficulties should be addressed towards sustainable management of GDEs in future: ①how to identify GDEs in the field, and determine which habitats and species are reliant on groundwater for their persistence in the landscape, ②what groundwater regime is required to sustain the existence of GDEs, ③how to manage GDEs with limited social resources, and ④what measures of ecosystem function can be monitored to determine that management is effective?     

Permeable Reactive Barrier for the treatment of contaminated surface water in Katedan industrial development area, Hyderabad, India

Permeable Reactive Barrier （PRB） is an emplacement of inert material （s） in the subsurface, designed to intercept a contaminated plume, provides a preferential flow path through the reactive media, and transforms the contaminant into environmentally acceptable forms to attain concentration remediation goals at the discharge of the barrier. The phenomena, which help in remediation within PRB, are adsorption/sorption, precipitation, oxidation/reduction and biodegradation. Various materials like zero-valent iron, zero-valent bi-metals, natural zeolites, organic carbon, fly ash, zeolites, limestone, activated alumina, apatites, etc. have been tried by many researchers to remove organic and inorganic contaminants. In USA, Canada, and many European countries commercial full-scale and pilot scale PRBs are successfully working. The design and installation of full scale PRBs needs laboratory treatability and dynamic flow column experiments？ The concept of PRB is being applied to treat contaminated surface water in the Katedan industrial area, Hyderabad, India. National Geophysical Research Institute （NGRI）, Hyderabad, India, conducted systematic studies in collaboration with Norwegian Geotechnical Institute （NGI）, Norway, to develop PRB technique to decontaminate the surface water pollution due to industrial effluent. A site assessment study in the Katedan Industrial Area, were carried out and water, soil and sediment from the lakes of the area were found to be polluted with high concentrations of heavy metals like As, Pb, Cr, Cd, Ni, etc. Adsorption studies at NGRI with synthetic samples and in-situ industrial effluent using different reactive media for removing contaminants like arsenic, chromium, cadmium, copper, nickel, lead and zinc have been carried out and yielded satisfactory results. The performance of zero-valent iron and limestone is encouraging in removing As,     

Groundwater Sustainability in Arid and Semi-arid Environments: A Review2

Groundwater is an important part of the global hydrological cycle. Sustainable utilization of groundwater is related to regional ecological security and food security, especially in arid and semi-arid environments. This paper reviewed the important achievements of the research on groundwater sustainability in arid and semi-arid environments during the past 30 years, and summarized the research progress in groundwater sustainability of arid and semi-arid environments from the conception evolution of groundwater sustainability, evaluation methods, influencing factors, sustainable management, and research frontiers. Our analysis suggests that groundwater in water limited environments around the world has shown unsustainable characteristics both in terms of quantity and quality. However, the existing research focuses more on the quantitative characteristics than the quality characteristics of groundwater, and thus the seriousness of the decline in groundwater sustainability is potentially underestimated. It is pointed out that more research efforts need to be done in the future in balancing the groundwater resources for human and nature, clarifying the impacts of human disturbance and climate change on groundwater sustainability, and strengthening groundwater sustainability through transboundary watershed management. We argued that the difficulty remains how to quantify the sustainable yield of a groundwater basin, and how to assess the groundwater sustainability. Further investigations are required in improving the theoretical framework of groundwater sustainability, modeling the impacts of the various alternative groundwater development scenarios, developing more flexible and efficient indicator frameworks for sustainability evaluation of groundwater system, and deploying more sophisticated groundwater monitoring network for real-time data acquisition. Finally, awareness should also be raised towards ground water sustainability both at the legal level and in the sphere of political action.     

Remediation of TCE-contaminated groundwater using zero valent iron and direct current: experimental results and electron competition model

The objectives of this study are to design an optimal electro-enhanced permeable reactive barrier (E2PRB) system for the remediation of trichloroethylene (TCE)-contaminated water using zero valent iron (ZVI) and direct current (DC) and to investigate the mechanisms responsible for TCE degradation in different ZVI-DC configurations. A series of column experiments was conducted to evaluate the effect of different arrangements of electrodes and ZVI barriers in the column on the TCE removal capacity (RC). In twelve different combinations of ZVI and/or DC application in the test columns, the rate of reductive dechlorination of TCE was improved up to six times with simultaneous application of ZVI and DC compared to that using ZVI only. The most effective arrangement of electrode and ZVI for TCE removal was the column set with ZVI and a cathode installed at the down gradient. Based on the electrokinetic study for the column systems with only DC input, single acid front movement could explain different RCs. An enhanced dechlorination rate of TCE using E2PRB systems, compared to a conventional PRB system, was observed, and is considered to be attributed to more electron sources: (1) external DC, (2) electrolysis of water, (3) oxidation of ZVI, (4) oxidation of dissolved Fe²⁺, (5) oxidation of molecular hydrogen at the cathode, and (6) oxidation of Fe²⁺ in mineral precipitates. Each of these electron sources was evaluated for their potential influencing the TCE RC through the electron competition model and energy consumption. A strong correlation between the quantity of electrons generated, RC, and the energy-effectiveness was found.     

氯代挥发性有机物(VOCs)氯同位素测试技术及其在地下水污染中的应用研究进展

在有机氯污染的研究中,氯同位素（³⁷Cl）的应用能够在原子水平上识别污染源并研究污染机理,为更加有效地研究地下水的有机污染提供了有利的工具。综述了8种氯代VOCs氯同位素的测试方法与技术,论述了氯代VOCs氯同位素在识别地下水污染源、监测有机污染物的降解过程、检验防治措施的修复效果、鉴别氯代VOCs的生产厂商、示踪氯代VOCs在土壤和水体中的迁移和混合过程等方面的应用,认为应尽快在国内研制先进的测试流程,开展有机氯同位素分馏机理的研究,加强应用C和Cl同位素技术对氯代VOCs污染和检测修复效果的研究。