对重金属和辐射污染的土壤和地下水的微生物修复

由重金属和辐射产生的环境污染在世界范围内产生了一系列问题.利用特殊的微生物如金属还原和耐金属细菌对环境中的金属和辐射污染进行处理具有非常好的前景.现场的生物修复的成功应用将对清除污染环境中的重金属和辐射提供潜在方法.最近的研究还关注于了解在微生物群体内重金属和辐射对微生物的作用.生物毯和生物膜是在生物修复中具有代表性的两种微生物群落的机能.金属的种类和价态变化、转移过程以及微生物代谢作用是对金属和辐射生物修复的三种重要的组成部分.结合以上三方面,可以更好的了解自然中的微生物和生物修复过程之间的关系.     

环境生态系统散落核素示踪研究新进展

环境生态系统中的放射性核素既具有生态毒性,对生物和人体健康产生重要影响,又具有稳定的衰变函数和输入通量,对环境生态系统具有重要示踪价值。人类可利用放射性核素来认识环境生态系统:①环境生态系统中放射性核素的基准:放射性强度与环境生态系统之间的平衡关系;②环境生态系统中放射性核素的行为:在环境生态系统不同宿体和组分间的运移关系。考察放射性核素在生态系统不同环节中比活度的变化有助于认识环境生态过程生物地球化学作用的影响。       

Natural radionuclides and trace elements in rice field soils in relation to fertilizer application: study of a chronic kidney disease area in Sri Lanka

The rising number of chronic kidney disease patients with no identifiable cause (CKD of uncertain aetiology), prevalent in some areas of the dry zone of Sri Lanka is suspected to be related to the environmental exposure to heavy metals. Agricultural soils are well recognized as being contaminated with potentially toxic metals from various forms of fertilizers and agro-chemicals, which could easily enter the human body through the food chain. The objective of this paper is to determine the content of heavy metals and activity concentration of background radionuclides such as K-40, Ra-226 and Th-232, in rice field soils. Rice farming is the most common agricultural practice in the affected region and possible heavy metal sources such as fertilizers are applied in abundance in the rice fields. Soils collected from a rice field in a non-CKD region was used for the comparison. In dry zone soils, Ca, K, Ba, Pb and Zr contents were higher and Fe, Mn, Cr, Ni and Zn contents were lower compared to that of soils from the wet zone non-CKD region. However, the activity concentration of soils was mostly the same in all samples, except for the K-40 contents of the soils, which were higher in the rice field soils compared to the undisturbed forest soils and also to the world averages. The mean U content was 3.6 mg/kg in the studied soils, although extremely high uranium contents were found in some fertilizer samples particularly in the triple superphosphates. Most uranium applied via fertilizer could contaminate the drinking water sources and even low uranium concentrations in drinking water may cause nephrotoxic effects.     

Numerical modeling of coupled fluid flow and thermal and reactive biogeochemical transport in porous and fractured media

Subsurface contamination problems of metals and radionuclides are ubiquitous. Metals and radionuclides may exist in the solute phase or may be bound to soil particles and interstitial portions of the geologic matrix. Accurate tools to reliably predict the migration and transformation of these metals and radionuclides in the subsurface environment enhance the ability of environmental scientists, engineers, and decision makers to analyze their impact and to evaluate the efficacy of alternative remediation techniques prior to incurring expense in the field. A mechanistic-based numerical model could provide such a tool. This paper communicates the development and verification of a mechanistically coupled fluid-flow thermal-reactive biogeochemical-transport model where both fast and slow reactions occur in porous and fractured media. Theoretical bases, numerical implementations, and numerical experiments using the model are described. A definition of the “rates” of fast/equilibrium reactions is presented to come up with a consistent set of governing equations. Two example problems are presented. The first one is a reactive transport problem which elucidates the non-isothermal effects on heterogeneous reactions. It also demonstrates that the rates of fast/equilibrium reactions are not necessarily greater than that of slow/kinetic reactions in the context of reactive transport. The second example focuses on a complicated but realistic advective–dispersive–reactive transport problem. This example exemplifies the need for innovative numerical algorithms to solve problems involving stiff geochemical reactions. It also demonstrates that rates of all fast/equilibrium reactions are finite and definite. Furthermore, it is noted that a species-versus-time curve cannot be used to characterize the rate of homogeneous fast/equilibrium reaction in a reactive transport system even if one and only one such reaction is responsible for the production of this species.     

An investigation about natural radioactivity,hydrochemistry, and metal pollution in groundwater from Calabrian selected areas,southern Italy

The increasing interest in radioactivity has brought about the need for an assessment of human exposure to radiation. It is, therefore, necessary to examine naturally occurring radioactivity in the environment, especially its occurrence in groundwater. The aim of this work was then to study the levels and behavior of the most significant natural radionuclides, also in order to improve the knowledge of the hydrochemical processes involved in the selected groundwater systems. Natural radioactivity in fifteen Calabrian groundwaters for human use was investigated through high-resolution gamma spectrometry (with a negative-biased Ortec HPGe detector) and liquid scintillation measurements. Particular attention was given on those radionuclides (³H, ²³⁸U, ²²⁶Ra, and ²²⁸Ra), which contribute in a significant way to the overall effective dose received by members of the public due to the intake of drinking water originating from groundwater systems. The activity concentration of ²³⁸U varied from 1 to 51 mBq/L, as a result of the geology of the investigated area and of the oxidizing conditions that favored U dissolution. ²²⁶Ra presented a broad range of activity concentrations (0.011–0.14 mBq/L), lower than uranium ones because radium occurs in groundwater under reducing conditions. Some heavy metals (Cd, Pb, Be, Hg, Ag, As, Tl, Sb, Se, and Ni) were also investigated through ICP-MS measurements and compared with the limits set by the Italian Legislation. Metals are released into the environment by both natural and anthropogenic sources; they leach into underground waters, moving along water pathways and eventually depositing in the aquifer.     

Chernobyl fallout and radionuclide activity in bottom sediments at the River Adige estuary (northern Adriatic Sea, Italy)

The artificial radionuclides ¹³⁷Cs, ¹³⁴Cs and ¹⁰⁶Ru have been determined up to 16 cm deep in two sediment cores collected in March 1988 at the River Adige estuary in the northern Adriatic Sea. Interdependent relations between the properties of the sediment levels and the activity of radionuclides have been investigated using multivariate statistical analysis. The interactions between radiocontaminants and the particulate matter or water phase are discussed during their transfer processes from the river to the estuary and the marine environment. Diffusion phenomena within the sedimentary column have also been considered. The vertical distribution of the artificial radionuclides due to Chemobyl fallout in sediment cores from the River Adige mouth, compared to those from similar estuarine environments in the Adriatic Sea, point out a general rapid accumulation of river-borne solid material in coastal zones of the North Adriatic Sea.     

Tailings dam seepage at the rehabilitated Mary Kathleen uranium mine,Australia

This study reports on the seepage of metals, metalloids and radionuclides from the Mary Kathleen uranium mill tailings repository. Since rehabilitation in the 1980s, the capped tailings have developed a stratified hydrochemistry, with acid (pH 3.7), saline, metal-rich (Fe, Mn, Ni, U ± As, Pb, Zn), oxygenated (1.05 mg L⁻¹ DO), radioactive waters in the upper tailings pile and near-neutral pH (pH 7.57), metal-poor, reduced (0.08 mg L⁻¹ DO) waters at depth. Seepage (∼0.5 L s⁻¹) of acid (pH 5.5), metal-rich (Fe, Mn ± Ni, U, Zn), radioactive (U-235, U-238, Ra-226, Ra-228, Ac-227) waters occurs from the base of the tailings dam retaining wall into the former evaporation pond and local drainage system. Oxygenation of the seepage waters causes the precipitation of Fe and coprecipitation and adsorption of other metals (U, Y), metalloids (As), rare earth elements (Ce, La) and radionuclides (U-235, U-238). By contrast, alkalis and alkaline–earth elements (Ca, K, Mg, Na, Sr), Mn, sulfate and to some degree metals (U, Zn, Ni), rare earth elements (Ce, La) and radionuclides (U-235, U-238, Ra-226, Ra-228) remain in solution until pH neutralisation and evaporation lead to their precipitation in efflorescences and sulfate-rich evaporative sediments. While the release of contaminant loads from the waste repository through seepage is insignificant (e.g. ∼5 kg of U per year), surface waters downstream of the tailings impoundment possess TDS, U and SO₄ concentrations that exceed Australian water quality guideline values in livestock drinking water. Thus, in areas with a semi-arid climate, even insignificant load releases of contaminants from capped tailings repositories can still cause the deterioration of water quality in ephemeral creek systems.     

Chemometric analysis of <Superscript>137</Superscript>Cs activity and heavy metals distribution in the Tatras’ soil

The goal of the paper was to determine the activity of ¹³⁷Cs and ⁴⁰K radionuclides as well as heavy metals Zn, Cr, Pb in soil samples taken from the Tatra National Park in the south of Poland. The samples were obtained as cores (10 cm in diameter) from the top 10-cm layer of the soil. Each sample was divided into three subsamples (a, b and c), where a was the subsample closest to the surface and c was the deepest one. Activity of the radionuclides was determined by means of gamma spectrometry, while analysis of heavy metals was performed (after microwave digestion) using atomic absorption spectrometry technique. The highest activity of cesium-137 was detected (5112 ± 120 Bq kg^?1) in the “a” layer of the core with the peak concentration of cesium-137 (14,452 ± 278 Bq m^?2) in the whole soil core. The highest detected concentration of heavy metals was: Zn—52.8 ± 4.4 mg kg^?1, Pb—260.1 ± 9.4 mg kg^?1, Cr—52.8 ± 4.4 mg kg^?1, respectively. Cluster analysis and principal component analysis were used to examine the obtained data. Application of statistical analysis tools allowed specifying the interdependencies between the examined variables.     

Distribution and mode of occurrence of radionuclides in phosphogypsum derived from Aqaba and Eshidiya Fertilizer Industry,South Jordan

Phosphogypsum (PG) is a by-product of the chemical reaction called the "wet process" whereby sul-phuric acid reacts with phosphate rock (PR) to produce phosphoric acid, needed for fertilizer production. Through the wet process, some impurities naturally present in the PR become incorporated in PG, including U decay-series radionuclides, are the main important concern which could have an effect on the surrounding environment and pre-vent its safe utilization. In order to determine the distribution and bioavailability of radionuclides to the surrounding environment, we used a sequential leaching of PG samples from Aqaba and Eshidiya fertilizer industry. The results showed that the percentages of 226Ra and 210Pb in PG are over those in the corresponding phosphate rocks (PG/PR), where 85% of the 226Ra and 85% of the 210Pb fractionate to PG. The sequential extraction results exhibited that most of 226Ra and 210Pb are bound in the residual phase (non-CaSO4) fraction ranging from 45%–65% and 55%–75%, respectively, whereas only 10%–15% and 10%–20% respectively of these radionuclides are distributed in the most labile fraction. The results obtained from this study showed that radionuclides are not incorporated with gypsum itself and may not form a threat to the surrounding environment.     

沉积物微量金属元素在重建水体环境变化中的意义

沉积物所记录的微量金属含量与形态的变化是指示人类活动影响下水体环境变化的有效指标,主要用于指示沉积物重金属污染、水体初级生产力变化和氧化还原条件等方面的水体环境状况。总体而言,沉积物中微量金属含量在近一个世纪以来显著上升,反映了采矿、冶金、污水排放、化肥使用、煤炭和石油燃烧等各种人类活动造成水体和沉积物重金属污染的记录作为浮游植物微量营养元素,Cu、Zn、Ni、Ba、Cd等在沉积物中的记录可以指示水体初级生产力水平。U、Mo、V、Cu、Cd、Mn等氧化还原敏感元素在沉积物中的富集或贫化,及其比值(如Re/Mo、Cd/U、Th/U和V/Sc)的变化,是指示水体和沉积物氧化还原环境的有效指标。但需要指出的是,在受人类活动影响的水体中,这些生产力和氧化还原指标很少能指示水体生产力或氧化还原状况,可能主要与人类活动同时造成这些金属元素大量污染输入而掩盖了其自生来源和内在变化的沉积记录有关。所以,对沉积物中微量金属元素来源的判别(陆源碎屑输入、人为输入和水体自生来源)是重建水体环境变化的重要前提。本文总结了多种化学和统计学方法(包括同位素示踪法、化学提取法、富集因子法和主成分分析法等)在沉积物金属来源判别中的应用另外,成岩作用等多种因素会干扰沉积物金属记录对环境变化的指示作用,所以构建多元素指标来综合判断沉积物记录所反映的环境信息是今后的研究所必须关注的     

Evaluation of dose parameters and radiological hazards in gravel samples of Konyaaltı Beach,Antalya

It is important to know the distribution and transfer of radionuclides such as uranium, thorium, and potassium, which exist naturally in the environment we live in. For this reason, measurements of these natural radionuclides have been carried out for 15 gravel samples collected from Konyaalt? Beach, Antalya. In order to measure the natural activity concentrations of potassium-40, uranium-238, and thorium-232 radionuclides, we performed the measurements by applying a gamma spectrometry method with a “3?×?3” NaI(Tl) detector, which is a multichannel analytical detector in the Suleyman Demirel University gamma spectrometry laboratory. The minimum, maximum, and mean values for the ²²⁶Ra activity concentration were measured as 19.74 Bq/kg, 37.03 Bq/kg, and 31.64 Bq/kg, respectively. The minimum, maximum, and mean values for the ²³²Th activity concentration were measured as 12.76 Bq/kg, 34.32 Bq/kg, and 26.67 Bq/kg, respectively. The minimum, maximum, and mean values for the ⁴⁰K activity concentration were measured as 196.37 Bq/kg, 421.13 Bq/kg, and 350.42 Bq/kg, respectively. Dose parameters and radiation damage indices were calculated using experimentally measured activity results and the resulting dose and hazard index values were compared with the determined limit values. It can be concluded that no risk may threat in terms of the hazard index values. In addition, all results obtained in terms of calculated dose values except for annual gonadal dose are below the recommended limit values.     

放射性核素在地下介质中迁移机理与模型研究

介绍了铀尾矿库的物理、化学概念模型和其中重金属、放射性核素迁移的一般过程 ;论述了沉淀作用、络合作用和胶体作用对放射性核素迁移的影响 ;重点讨论了描述吸附作用的离子交换模型和表面络合模型的建模机理 ;对定量模拟放射性核素迁移行为的 Kd模型、表面络合模型及“反应 -运移模型”的应用进行了评述。     

Evidence of long-lived I and Pu isotopes enrichment in vegetation samples around the Marcoule Nuclear Reprocessing Plant (France)

Iodine-129 and ²³⁸Pu, ²³⁹Pu and ²⁴⁰Pu are radionuclides posing a long-term safety concern due to their potential integration in bio and geo-chemical cycles and their significant half-lives. They are present throughout the environment at very low levels, and more particularly, nuclear fuel reprocessing plants (NRP) have been identified as local sources of these radionuclides. However, due to measurement difficulties, published data concerning their activity levels in terrestrial environments around NRP facilities remain scarce. The aim of the present paper is to communicate ¹²⁹I, ²³⁸Pu and ^239+240Pu measurements results from the area surrounding the Marcoule NRP, which is situated in SE France. Several vegetation samples were collected around the nuclear installation in 1999 and 2000, in order to examine the possible impacts of its atmospheric I and Pu discharges. Based on ²³⁸Pu/^239+240Pu activity ratios and ¹²⁹I/¹²⁷I isotopic ratios, local increases in Pu and ¹²⁹I were detected and related to industrial activity.     

重金属元素的时空分布与矿山采矿历史的地球化学非线性响应

人类活动对环境影响严重,采矿活动尤甚。对矿山环境的研究重要而迫切,特别是重金属元素污染,其首要问题是重金属元素的迁移能力和影响因素,归根结底是污染元素从污染源到外围区域的时空响应和时空结构。中国铜陵、铜绿山等众多金属矿山具有悠久的采矿历史,在为国民经济带来重大效益的同时,也带来了众多的环境问题。目前对矿山环境的研究多集中在非动态及调查性研究方面,很少从时间与空间结构2个角度同时考虑地球化学迁移转化的机理;国内关于矿山环境的研究资料也不多。建议在矿区重金属环境地球化学的研究中应用非线性研究手段,重点是分形、多重分形、非线性时间序列等分析方法,研究重金属元素的时序分布和空间展布机制。     

Gross-beta activity in ground water: natural sources and artifacts of sampling and laboratory analysis

Gross-beta activity has been used as an indicator of beta-emitting isotopes in water since at least the early 1950s. Originally designed for detection of radioactive releases from nuclear facilities and weapons tests, analysis of gross-beta activity is widely used in studies of naturally occurring radioactivity in ground water. Analyses of about 800 samples from 5 ground-water regions of the United States provide a basis for evaluating the utility of this measurement. The data suggest that measured gross-beta activities are due to (1) long-lived radionuclides in ground water, and (2) ingrowth of beta-emitting radionuclides during holding times between collection of samples and laboratory measurements.Although⁴⁰K and²²⁸Ra appear to be the primary sources of beta activity in ground water, the sum of⁴⁰K plus²²⁸Ra appears to be less than the measured gross-beta activity in most ground-water samples. The difference between the contribution from these radionuclides and gross-beta activity is most pronounced in ground water with gross-beta activities > 10 pCi/L, where these 2 radionuclides account for less than one-half the measured ross-beta activity. One exception is groundwater from the Coastal Plain of New Jersey, where⁴⁰K plus²²⁸Ra generally contribute most of the gross-beta activity. In contrast,⁴⁰K and²²⁸Ra generally contribute most of beta activity in ground water with gross-beta activities < 1 pCi/L.The gross-beta technique does not measure all beta activity in ground water. Although³H contributes beta activity to some ground water, it is driven from the sample before counting and therefore is not detected by gross-beta measurements. Beta-emitting radionuclides with half-lives shorter than a few days can decay to low values between sampling and counting. Although little is known about concentrations of most short-lived beta-emitting radionuclides in environmental ground water (water unaffected by direct releases from nuclear facilities and weapons tests), their activities are expected to be low.Ingrowth of beta-emitting radionuclides during sample holding times can contribute to gross-beta activity, particularly in ground water with gross-beta activities > 10 pCi/L. Ingrowth of beta-emitting progeny of²³⁸U, specifically²³⁴Pa and²³⁴Th, contributes much of the measured gross-beta activity in ground water from 4 of the 5 areas studied. Consequently, gross-beta activity measurements commonly overestimate the abundance of beta-emitting radionuclides actually present in ground water. Differing sample holding times before analysis lead to differing amounts of ingrowth of the two progeny. Therefore, holding times can affect observed gross-beta measurements, particularly in ground water with²³⁸U activities that are moderate to high compared with the activity of⁴⁰K plus²²⁸Ra. Uncertainties associated with counting efficiencies for beta particles with different energies further complicate the interpretation of gross-beta measurements.     

Artificial radionuclides in the sediments of the Rhne river: a snapshot of the situation during winter 1994/95

Artificial radionuclides (⁶⁰Co, ¹⁰⁶Ru, ¹³⁴Cs and ¹³⁷Cs) produced in the nuclear power plants along the Rhne valley have been detected in most of the 35 sediment samples collected from the shores of the Rhne river in southern France. In one sample traces of ²⁴¹Am were found, suggesting the presence of transuranic elements. The wide use of river water for irrigation and the occasional big inundations of the Rhne have spread the artificial radionuclides over huge areas, quite far behind the river shores. Although artificial radionuclides are present in fields where food crops are collected, their activity is currently considerably lower than the activity of the natural radionuclides present in the river sediment.     

Conceptual model for radionuclide release,Yucca Mountain,Nevada, USA

A new conceptual model for release rate of radionuclides from the proposed repository for high level nuclear waste located at Yucca Mountain, Nevada is developed. The model predicts that heat generated from radioactive decay combined with the unsaturated environment will lead to an inward flow system that, under many relevant conditions, will slow the release of and sometimes sequester radionuclides at locations of higher heat release and lower water percolation. The amount of protection will be greatest for more concentrated waste forms such as spent fuel and less for glass waste forms. The redistribution and concentration of the radionuclides is anticipated to significantly delay radionuclide release and create a tendency towards gradual release over time that is independent of localized penetrations of metallic barriers.     

The influence of fly and bottom ash deposition on the quality of Kastela Bay sediments

The objective of this study was chemical and radiological characterization of Kastela Bay sediments exposed to numerous anthropogenic sources like deposition of fly and bottom ash enriched in radionuclides and heavy metals, chemical plant, cement plant, iron plant, shipyard, electroplating facility, untreated industrial and domestic waste waters as well as heavy traffic. Totally, 33 samples of the mixture of fly and bottom ash, 12 sediment cores ranging from 0 to 40 cm and nine surface sediment samples were analyzed. Enrichment in heavy metals in the mixture of fly and bottom ash was ranging from 1.5 to 36 times compared to flysch soil while ²²⁶Ra and ²³⁸U were up to 50 times enriched compared to average activities characteristic for surrounding soils developed on the Middle and Upper Eocene flysch. Maximum ²³⁸U activity was approximately 32 times higher and ²²⁶Ra approximately 40 times higher in the Kastela Bay sediment compared to mean value determined for Adriatic sediments. The highest enrichment in sediment cores compared to background values were found for Zn (35.6 times), Pb (16 times), Cr (9.1 times) and Ni (4 times)     

地浸采铀矿山地下水环境修复研究进展

地浸采铀技术已成为世界采铀的主流工艺,采区退役后地下水环境修复亦为人们所关注的热点。文章简要介绍了碱法、中性和酸法三种典型地浸采铀技术的特点,系统分析了地浸采铀对地下水环境的影响,并以酸法地浸铀矿山地下水环境修复技术为例,重点介绍了物理化学修复技术和生物修复技术及其原理与应用,归纳总结了其优缺点,并对未来的研究方向进行了展望。指出下一步应加强在酸性与氧化环境中能使铀固定并长期稳定的新技术,高活性、强适应性修复菌群的选育、驯化技术,地下水异位-原位协同生物修复技术,以及放射性核素及重金属在铀矿地浸地下水环境中的吸附-解吸、氧化-还原、溶解-沉淀等行为与机理及其主控因素等方面的研究。