Rate controlling processes in the release of radium-226 from uranium mill tailings

Uranium mill tailings (a pyritic quartz conglomerate ore) obtained from a Canadian operation were leached according to a modification of the method recommended by I.A.E.A. for the leaching of radioactive ions from solidified wastes. A static leach test procedure was chosen to provide information to permit an assessment of hazard due to release of Ra-226 to the environment. Narrow range size fractions (53 to 75 μm) of both fresh material obtained directly from a tailings line and material weathered for approximately 10 to 15 yr in a tailings basin were leached for up to 70 days. Distilled water and an acidic synthetic effluent (pH 2.5) were chosen as leachants. Two sequential desorption processes were observed, one before and the other after a leaching period of approximately 10 to 15 days. In the later and more significant stage of desorption, the leaching behaviour could be described in terms of a diffusion mechanism. Significantly greater quantities of ²²⁶Ra were leached over relatively short leaching periods by the acidic effluent; thus the quality of the effluent and percolating water in a tailings disposal area would markedly affect the leachability of Ra from tailings. It was also found that the quantities of ²²⁶Ra leached were significantly influenced by the solid: liquid ratio at low leaching volumes.     

The Effect of the Uranium Content in the Tailings on Some Cultivated Plants

Uranium is a radiotoxic and chemotoxic heavy metal. Uptake and accumulation of U has been studied in plants native to uranium mine sites, but not in cultivated plants which are commonly consumed by humans. The objective of this study was better understanding of U uptake and accumulation in cultivated plants and whether different contents of uranium (U) in the substrate affect its concentration in plants and their dry matter mass. Two substrate variants for growing plants, which differed in the uranium content: solid wastes (tailings) and tailings mixed with sand (w/w 1:1). Large amounts of solid wastes (tailings) resulting from the exploitation and treatment of uranium ore from the closed uranium mine Gabrovnica–Kalna, on southeast of Serbia, contained generally 15.33 mg U/kg. In the experiment, three plant species (corn NSSC 231, sunflower N.S. Dukat, and green peas Smederevska Palanka) were grown in pots on the four substrate variants during 40 days. Substrate was suffused by drinking water (DW) and “uranium water” (UW), which issue out from the mine, contained 0,053 mg U/ dm³. Obtained results show that when UW was added to tailing concentration of U in plants increased. When the content of U in the substrate was lowered by adding sand, the concentration of U in plants decreased, though was significantly higher in comparison to the variants to which DW was added. Dry matter mass was higher in variants where UW was used. Concentration of U was significantly higher in root than in above-ground parts.     

Solid Wastes In Urban And Rural Areas Of Ibadan,Nigeria: Composition,Treatment And Public Health Concerns

The composition of solid waste produced at various locations in Nigeria differs considerably because the amounts generated and the constituents thereof are determined by social customs and living standards. Nigeria has undergone extensive industrial development which has often changed the composition of domestic solid waste as well as agricultural wastes. The disposal and utilization of these mixed wastes has presented new risks and problems for our society and environment. Though most solid waste in Nigeria contains little human and animal material, pathogenic organisms affecting both continue to be present. Potential risks to human health and the environment that can arise from domestic solid waste disposal and utilization in Nigeria include pollution of water and air, accidents, contact contamination and breeding sites for flies and rodents. There also are long-term problems in relation to the human food chain.     

Environmental impact of radioactive waste management in the nuclear industry

Radioactive wastes from the nuclear industry are classified into low, intermediate and high activity levels, and problems of their storage and release examined in detail. Current means of storage are considered with reference to processing of low and intermediate level liquid waste, processing of high level waste, processing of airborne waste, and ground disposal and processing of solid waste. Release is discussed in terms of effluent release limits, monitoring and the use of permanent records, impact of release to the human environment, impact of release to the material environment, and guides for preventing accidental release. Contamination of the shore of Lake Huron from radioactive fallout is discussed as a particular example. Problems to be solved are identified in three main areas: gaseous wastes, actinide-contaminated wastes, and permanent disposal, and some specific suggestions for study are made.     

Plant uptake assay to determine bioavailability of inorganic contaminants

A laboratory technique has been developed to rapidly assess the potential uptake of contaminants by plants growing into waste burial sites. A soil-less planting media was used to provide rapid plant growth and reproducible growing conditions. The uptake of contaminants by several plant species grown on uranium mill tailings materials has been examined. The bioavailability of Mo, Se, Cl, and other trace metals in tailings was greater than in a surface soil from a uranium mining area. Significant differences in nutrient and contaminant contents in aboveground biomass were found between species.     

Thorium 230 determination in polluted lake water — A study of interferences

The effect of contaminants, both known and unidentified, in interfering with the coprecipitation of ²³⁴Th tracer with BaSO₄ is described. The effect is illustrated by results obtained on water from Nero Lake, a uranium mine tailings dumping area. While most of the components of the water are known, attempts to duplicate the effect using synthetic water were less successful. Thus some strongly interfering substance in the water remains to be identified. A successful alternative method for Ra and Th determination is mentioned.     

Impact of Past Mining Activity on the Quality of Water and Soil in the High Moulouya Valley (Morocco)

Physical and chemical properties and the total content of potentially toxic metals (PTMs) in waters and soils were studied from the High Moulouya Valley (Morocco) in order to assess the impact of the past mining activity on their quality and to lay the foundations of a potential reclamation of the area. Surface water and groundwater samples were collected from the Moulouya River and mine pit lakes; tailings and soils were sampled inside and outside the mine sites of Zeïda, Mibladen, and Aouli. Both waters and soils were alkaline, due to the limestone environment, and contained Pb and Zn as main metallic contaminants. Pollution levels were highest within the Mibladen mining site, and soil pollution was mainly restricted to the areas where activities of metal concentration were carried out. Tailings and soils from these areas besides Pb and Zn were also polluted by As, Cd, and Cu showing clay fraction highly enriched in metal contaminants. At the time of study, all soils and wastes (including the highly polluted tailings) were in advanced stage of spontaneous herbaceous and arbustive revegetation. It is concluded that, in the High Moulouya Valley, the processes governing PTM transfer from the element-rich sites to the nearby environment are strongly influenced by pH, carbonate content, and semi-arid climate reducing metal mobility from the mining waste impoundments by dissolution. The transfer by wind and water erosion of metal-enriched fine waste particles is likely to be a much more important vector for metal dispersion. In this perspective, among a range of land remediation techniques available, natural and oriented revegetation could represent a low-cost and possible permanent solution.     

云贵高原农村地区生活垃圾特性与管理分析

鉴于当前农村生活垃圾的污染日益突出,且云贵高原农村地区生活垃圾的研究尚处于空白,随机选择了该地区9个自然村,通过访问式问卷调查、现场采样、实验室测试等方法,对当地农村生活垃圾的特性、群众对生活垃圾的认知以及参与管理的意愿进行了调研,以期为农村生活垃圾的管理与处理处置提供理论支撑和技术指导。研究表明：云贵高原农村地区生活垃圾产生量为160g·人-1·d-1;主要组分有厨余类、灰土类、橡胶类、纸类和木竹类;垃圾容重、含水率、灰分、可燃物和热值分别为106kg·m-3、39．16％、19．48％、41．37％和7615kJ·kg-1。此外,云贵高原农村地区群众对生活垃圾的污染性认知主要来自于直观感受,对可回收生活垃圾的认知直接受当地废品回收商的影响,对有毒有害生活垃圾的认知不足;群众对生活垃圾处理处置的支付意愿较好,参与生活垃圾保洁和管理工作的意愿较强,该地区已基本具备开展农村生活垃圾管理与处理的群众基础。     

Adaptation of Working Conditions of an Operating Drinking Water Treatment Plant to Remove Naturally Occurring Radionuclides

Naturally occurring radionuclides such as uranium and radium are present in water used for human consumption. There are several procedures to remove the uranium and/or radium content in drinking water, although they have mainly been used just in laboratory tests, and in only a few cases in pilot plants. In the present work, an operating drinking water treatment plant (DWTP) with gross alpha activity above the 0.1?Bq?L^?1 threshold was selected, with the water??s uranium content being principally responsible for this activity. The routine procedure used in the DWTP was incapable of removing this activity from the drinking water. A modification of the procedure in the coagulation?Cflocculation step successfully removed 50?C83?% of the uranium from the drinking water finally consumed by the population, with the resulting gross alpha activity being reduced to below 0.1?Bq?L^?1. The modified procedure was reversible??whenever the procedure was halted, no uranium was removed. The uranium removed ended up concentrated in the sludge generated by the plant. A sequential extraction procedure applied to the sludge showed most of it to be attached to the easily and moderately reducible fractions and hence extractable with hydroxylamine and ammonium oxalate, respectively. This was because in the coagulation?Cflocculation process, the uranium was essentially removed by association with aluminium oxides.     

Differentiation of physical from chemical toxicity in solid waste fish bioassays

This study showed that particulate (i.e., physical) toxicity was responsible for rainbow trout deaths in bioassays with two separate solid wastes. This conclusion was based on: (1) fish necropsies which indicated physical damage to gills but no evidence of chemical damage to liver or kidney, (2) chemical analyses which indicated that levels of Priority Pollutants and other target compounds were too low to cause the observed toxicity, (3) structural and chemical analyses of the waste particles which showed that these consisted of inert materials, and (4) the use of centrifugation techniques to remove most of the suspended particulate material in bioassay tanks resulting in an elimination of most of the toxicity. The particles associated with the lethal effects were approximately 5 to 10 μm in size. Regulatory testing of solid wastes must distinguish physical and chemical toxicity since disposal options can vary depending on the mode of toxicity. For instance, chemical toxicity raises concern regarding leaching through soils into groundwater, whereas if physical particles are responsible for toxicity, such leaching is not of concern.     

Effects of cover materials on leaching of constituents from dolomitic lead mine tailings

Five raised-bed test plots were used to study the effects of cover materials on the leaching of constituents from dolomitic Pb mine tailings over a 2-yr period. The cover materials studied were a fertilizer and seed mixture, anaerobically digested sewage sludge, loam and sod, and fallen leaves from silver maples (Acer Saccharinum); one plot was not covered. Fresh leachates and receiving pool waters were analyzed for ten metals, Si, P, inorganic anions, filterable organic carbon (FOC), and alkalinity. The mixture of fertilizer and seed decreased leaching of Pb and Zn during the first year. The leaf cover increased leaching of Pb during both years; this effect decreased as the leaves weathered. Sludge caused some increase in Pb leaching during the first year, and increased Cd leaching during both years. Concentrations of most leachate constituents decreased, and pH increased in the receiving pools. Concentrations of Pb remained higher in the receiving pool for the leaf-covered plot than in the other pools. Increases in leaching of Pb and Cd with a sludge cover were moderate, and the ability of the material to support plant growth on the tailings suggested that it may be a good medium for inducing growth of vegetative cover on the dolomitic tailings. Other organic materials may cause pronounced increase in the concentration of toxic trace metals in leachate from the tailings.     

Removing Uranium and Radium from a Natural Water

Different types of iron- or aluminium-based coagulants were used to study the influence of the key water potabilization processes of coagulation, flocculation, and decantation on the elimination of significant concentrations of uranium and radium. We first determined the physico-chemical and radiological characteristics of a natural water to use in the trials, to which we then added known activities of ²³³U and ²²⁶Ra. While the efficiency of the decontamination processes was found to be independent of coagulant dose, there was a clear dependence on the pH at which the coagulation was carried out, with the optimum for the elimination of uranium being pH 6 and for radium pH 10. Uranium elimination was independent of the type of coagulant used, but the best radium elimination was with the iron-based reagents.     

Geochemical and Mineralogical Features of Overbank and Stream Sediments of the Beal Wadi (Cartagena-La Union Mining District, SE Spain): Relation to Former Lead�CZinc Mining Activities and Its Environmental Risk

Heavy metals and some major element concentrations were investigated in overbank sediments and stream bed sediments of the ephemeral Beal wadi creek in the Cartagena-La Union mining district (SE Spain). Two vertical sediment profiles were extracted and the chemical and mineralogical compositions were both investigated by X-ray fluorescence and X-ray diffraction. Geochemical variations in vertical profiles of these two kinds of sediments allow observing noticeable heavy metals pollution (especially Fe, Pb, and Zn) in both kind of sediments but especially in the overbank sediments (reaching values of approximately 13% Fe, 6% Pb, and 6% Zn). A single extraction (DIN 38414-S4 leaching test) was made to observe the transfer of metals from solids to liquid phase. Pb, Zn, Cu, and Cd contents surpass the leaching values established by the DIN 38414-S4 limits established by Spanish legislation to consider these wastes as hazardous wastes. Geochemical comparison between leaching behavior of the two types of sediments reveals a major ability of overbank sediments in transferring heavy metals to the water flow.     

The state of natural radionuclides of uranium,radium, and thorium in soils

A review of publications is presented on the state of uranium, radium, and thorium in soils. It is shown that the properties of radionuclides in soils provide the diversity of the forms and mechanisms of their fixation in the soil exchange complex. Organic substances and clay minerals are the most important sorbents of uranium, radium, and thorium. According to the available data, the processes of ion exchange, complexing, hydrolysis, and reduction-oxidation are responsible for the uranium and thorium fixation in soils. For radium, the ion exchange and coprecipitation with its chemical macro analogs and iron hydroxides are considered to be the most important. The initial chemical form of the elements and the presence of macrocomponents affect the sorption behavior of radionuclides from technogenic sources. It is emphasized that the current methods of investigation do not allow assessing in full measure the transformation of the forms and the mechanisms of uranium, radium, and thorium fixation in soils. The causes are presented that make the interpretation of the results obtained difficult.     

Prioritization of ground water contaminants and sources

The objective of this research was to identify chemical, physical, bacteriological, and viral contaminants, and their sources, which present the greatest health threat in public ground water supplies in the USA; and to classify (prioritize) such contaminants and relative to their health concerns. The developed contaminant prioritization methodology was based on frequency of occurrence and adverse health effects. Adverse health effects were based on carcinogenic potency, toxicity, hazardous chemical priorities and drinking water standards. Application of the methodology for wellhead protection areas, (WHPAs) revealed that approximately 200 different contaminants have been detected in the nation's public ground water supplies. The seven chemical constituents with the highest priority were arsenic, chromium, cadmium, carbon tetrachloride, chloroform, 1, 1-dichloroethylene, and ethylene dibromide. Other contaminants of concern were trichloroethylene, nitrates, barium, 1,1,1-trichloroethane, benzene, tetrachloroethylene, selenium, lead, toluene, mercury, gross alpha radiation, methylene chloride, coliform bacteria, metolachlor, metribuzin, 1, 1, 2, 2-tetrachloroethane, dibromochloroethane, simazine, radium-266, and toxaphene. The contaminant source prioritization methodology was also based on frequency of occurrence. Over 30 categories of sources were evaluated, with the eight with highest priority including agricultural activities, hazardous waste sites, landfills, industrial operations, septic tank systems, oil and gas field activities, urban land use, and underground storage tanks.     

农业固体废物分类及其污染风险识别和处理路径

防治农业固体废物污染,对保障农民身体健康,维护农业生态安全,促进农村经济社会可持续发展具有重要意义。在总结农业固体废物内涵和外延的基础上,探讨农业固体废物的主要来源、分类方法和基本特征,按照来源、毒性、组分和形态对农业固体废物进行了分类,剖析来源单一与类型多样的双重性、潜在污染与重要资源的两面性、周年持续与季节波动的复杂性等农业固体废物的基本特征。识别农业种植固体废物、畜禽水产养殖固体废物、废旧农业投入品和农产品初加工固体废物的潜在污染风险。梳理农业固体废物污染防治、处理利用代表性法规政策,分析农业固体废物全链条运营和监管体系,提出\     

Risks due to groundwater contamination at a plutonium processing facility

The specter of contaminated groundwater looms over industrialized, suburban, and rural areas. The sources of groundwater contamination are many and the contaminants numerous. Historical waste disposal practices pose the greatest threat to groundwater in the United States. Common solvents such as trichloroethylene, tetrachloroethane, benzene, and carbon tetrachloride have been found in widespread areas. For this study, a risk assessment is performed using a multimedia environmental transport model to estimate public risk from a contaminated groundwater plume. From 1955 to 1973, a crib above the groundwater plume was used for the disposal of plutonium processing waste. The plume contains chemical and radioactive wastes that could pose a health threat to people living in the vicinity of the site. Remedial designs are selected for remediating the different contaminants in the groundwater plume through a multiple phase treatment process. This study evaluates: baseline health risks to the public, health risk reduction to the public as a result of the remedial activities, health risk to the workers directly involved in cleaning up the site, and costs associated with each remedial activity.     

A field study of diffusion controlled migration of copper,zinc and cadmium in a clay formation

The distribution of Cu, Zn and Cd within an illitic clay formation located beneath a ca 150 yr old deposit of sulfidic mine tailings was studied. Total concentrations of metals have been quantified as a function of depth. The distribution between the pore water and the solid phase has been measured. Qualitative information was obtained by an operational leaching procedure. Field measurements were validated with batch adsorption experiments. The results suggest that transport of metals originating from the tailings is diffusion controlled. Apparent diffusivities as well as distribution coefficients were estimated.     

Permeability and Retention to Water and Leachate of a Compacted Soil Used as Liner

In many developing countries, a landfill remains one of the most extensively employed solid waste disposal solutions. Although a landfill is a well-designed engineering system, the base lining of a landfill may perform poorly and allow the leachate to reach the underlying soil layers and groundwater. Leachates contain a variety of toxic and hazardous contaminants, which are attenuated in the soil by various processes that slow or transform them. Thus, the objective of this research was to study the water and leachate permeability and retention of the liner soil in a landfill experimental cell by subjecting it to geotechnical, chemical-mineralogical, and physicochemical characterizations, water and leachate permeability tests, and mercury intrusion porosimetry (MIP). In addition, the water and leachate retention curves were determined and analyzed using RETention Curve (RETC) software to obtain the unsaturated permeability curves. The leachate in the soil decreased the suction considering the moisture content of the compacted soil in the field, which consequently increased the leachate permeability of the mineral liner. For the same suction value, in the drying pathways, the soil retained a greater amount of distilled water than leachate. In the wetting pathways, the opposite occurred. Microorganisms were detected in the soil during the filter paper test. The permeability coefficients of the unsaturated soil were directly proportional to the gravimetric moisture content for the water and the leachate, which demonstrated that the soil presents lower unsaturated permeability coefficients for water than for leachate for the same water content.     

Recovery of aluminum from solid waste

Several wet and dry methods for extracting Al from mixed municipal refuse and other Al-bearing wastes (such as auto shredder residues) are discussed. Analytical results are given for samples of non-ferrous metals and Al concentrates obtained from mixed solid wastes. These analyses include both the chemical constituents of the samples and observed melt losses. The analytical results are compared with specifications that have been developed for Al recovered from mixed municipal refuse. The various uses for this material by the Al industry are discussed.