Simulation of flow and mercury transport in Upper East Fork Poplar Creek,Oak Ridge,Tennessee

As a result of nuclear processing activities started back in the 1950s, the environment in the vicinity of the Y‐12 National Security Complex (Y‐12 NSC) in Oak Ridge, Tennessee, and surrounding watersheds has been contaminated by nearly 1,000 tons of elementary mercury. To comply with the state and federal surface water quality standards, a significant reduction in mercury concentration to parts‐per‐trillion levels has been proposed. In order to analyze the mercury cycle in the environment and provide forecasting capabilities for the flow and transport of mercury within the Upper East Fork Poplar Creek (UEFPC) watershed, an integrated surface and subsurface flow and transport model has been developed using the hydrodynamic and transport numerical package, MIKE, developed by the Danish Hydraulic Institute. The model has been constructed and calibrated using an extensive collection of historical records (i.e., hydrological data, and mercury concentration measurements in groundwater, soil, and sediment) obtained from the Oak Ridge Environmental Information System database. Daily fluctuations in stream flow, as a result of scattered rainfall, flooding, and flow augmentation, resuspend the contaminated streambed sediments and/or erode the polluted streambank soil and provide a secondary source of mercury to the creek. In order to investigate the significance of sediment‐mercury interactions on the fate and transport of mercury within the UEFPC study domain, simulations were performed for two different cases (i.e., with and without consideration of sediment‐mercury interactions). Computed total suspended solids and mercury concentrations at the integration point of the creek are compared with the corresponding historical records in both cases. As confirmed by the numerical simulations, a substantial portion of the mercury detected in the river is likely in the form of sediment particle–bound mercury (i.e., mercury particulates). © 2012 Wiley Periodicals, Inc.     

Review of in situ remediation technologies for lead,zinc, and cadmium in soil

This article presents a review of in situ technologies for the remediation of soils contaminated with lead, zinc, and/or cadmium. The objective of this review is to assess the developmental status of the available in situ technologies and provide a general summary of typical applications and limitations of these technologies. The literature review identified seven in situ remediation technologies—solidification/stabilization, vitrification, electrokinetic remediation, soil flushing, phytoextraction, phytostabilization, and chemical stabilization. These technologies were considered for their ability to meet a specific set of remediation objectives under a range of conditions. Each of these technologies has both strengths and weaknesses for addressing particular remedial situations discussed in the article for each of the technologies. A general summary of which technologies are most applicable to common remedial scenarios is also provided. © 2004 Wiley Periodicals, Inc.     

Quantitative analysis of remedial approaches,costs, and time required to remediate dry cleaner sites

This article presents an analysis of remedial approaches, costs, and time required to remediate dry cleaner sites in the United States based on data compiled by the State Coalition for the Remediation of Dry Cleaners (SCRD). Trends in soil and groundwater remedy selection are identified and discussed. Median costs and the time required to remediate dry cleaner sites are presented. In addition, median costs and the duration of soil and groundwater remediation for the most widely used remedial approaches are reported. The analysis is intended to serve the needs of stakeholders, including responsible parties, consultants, regulators, and litigants, as well as real estate developers, banks, and other holders of portfolios of impacted dry cleaner sites by providing quantitative results useful for planning and transactional analysis. © 2011 Wiley Periodicals, Inc.     

Dynamics of copper and zinc sedimentation in a lagooning system receiving landfill leachate

This study characterises the sediment dredged from a lagooning system composed of a settling pond and three lagoons that receive leachates from a municipal solid waste (MSW) landfill in France. Organic carbon, carbonate, iron oxyhydroxides, copper (Cu) and zinc (Zn) concentrations were measured in the sediment collected from upstream to downstream in the lagooning system. In order to complete our investigation of sedimentation mechanisms, leachates were sampled in both dry (spring) and wet (winter) seasonal conditions. Precipitation of calcite and amorphous Fe-oxyhydroxides and sedimentation of organic matter occurred in the settling pond. Since different distributions of Zn and Cu concentrations are measured in sediment samples collected downstream in the lagooning system, it is suggested that these elements were not distributed in a similar way in the leachate fractions during the first stage of treatment in the settling pond, so that their sedimentation dynamics in the lagooning system differ. In the lagoons, it was found that organic carbon plays a major role in Cu and Zn mobility and trapping. The presence of macrophytes along the edges provided an input of organic matter that enhanced Cu and Zn scavenging. This edge effect resulted in a two-fold increase in Cu and Zn concentrations in the sediment deposited near the banks of the lagoons, thus confirming the importance of vegetation for the retention of Cu and Zn in lagooning systems.     

Bacterial leaching of copper,zinc, nickel and aluminum from discarded printed circuit boards using acidophilic bacteria

Journal of Material Cycles and Waste Management - E-waste is an important secondary source of precious metals. Especially discarded printed circuit boards (PCBs) contain high concentrations of...     

Effect of composting process on phytotoxicity and speciation of copper, zinc and lead in sewage sludge and swine manure

The concentration and bioavailability of heavy metals in composted organic wastes have negative environmental impacts following land application. Aerobic composting procedures were conducted to investigate the influences of selected parameters on heavy metal speciation and phytotoxicity. Results showed that both of sewage sludge (SSC) and swine manure (SMC) composting systems decreased the pH, the content of organic matter (OM) and dissolved organic carbon (DOC), and total amounts of Cu, Zn and Pb. Sequential extraction showed that readily extractible fractions of exchangeable and carbonate in Cu and Zn increased during SSC composting but decreased during SMC composting, thus their bioavailability factors (BF) enhanced in SSC but declined in SMC. The fraction of reducible iron and manganese (FeMnOX) of Cu and Zn in SSC and FeMnOX-Cu in SMC decreased, but FeMnOX-Zn in SMC gradually increased in the process of compost. In contrast, the changes of Pb distributions were similar in two organic wastes. Pb was preferentially bound to the residual fraction and its BF decreased. The evolution of heavy metal distributions and BF depended on not only total metal concentrations but also the other properties, such as pH, decomposition of OM and decline of DOC. The germination rate (RSG), root growth (RRG) and germination index (GI) of pakchoi (Brassica Chinensis L.) increased during the composting process. Linear regression analysis demonstrated that GI, which could represent phytotoxic behavior to the plants, could be poorly predicted by BF or total amount of metals, i.e., BF-Zn, T-Cu. However, the inclusion of other physicochemical parameters (pH, OM and DOC) could enhance the linear regression significances (R).     

Effect of unburned carbon on lead, zinc, and copper recovery from molten fly ash by chloride-induced volatilization

The present work focuses on investigation of the effective recovery of heavy metals from molten fly ash by applying chloride-induced volatilization. In particular, the effect of unburned carbon on the chloride-induced volatilization of lead, zinc, and copper from model and real molten fly ashes was investigated in the temperature range 873–1173 K under a N₂ atmosphere. As a result, almost 100% of lead and a significant proportion of zinc were volatilized from the real molten fly ash samples at 1173 K. In contrast, for the model fly ash, volatilization ratios of lead and zinc at 1173 K were only 85% and 25%, respectively. Further, the results of X-ray diffraction analysis suggested that PbO in molten fly ash was converted either to Pb₂OCl₂ or Pb by respective chlorination and reduction reactions. Meanwhile ZnO and CuO in the molten fly ash were reduced to Zn and Cu by reaction with unburned carbon. Subsequently, Pb, Zn, and Pb₂OCl₂ were volatilized, but Cu remained in the solid residue. Finally, the volatilization ratio of zinc increased with the addition of carbon, and more than 98% of zinc was volatilized at 1173 K from a fly ash with a carbon content of 20%.     

Effect of sewage sludge or compost on the sorption and distribution of copper and cadmium in soil

The application of biosolids such as sewage sludge is a concern, because of the potential release of toxic metals after decomposition of the organic matter. The effect of application of sewage sludge (Sw) and compost (C) to the soil (S) on the Cu and Cd sorption, distribution and the quality of the dissolved organic matter (DOM) in the soil, was investigated under controlled conditions. Visible spectrophotometry, infrared spectroscopy, sorption isotherms (simple and competitive sorption systems), and sequential extraction methods were used. The E4/E6 (lambda at 465 and 665 nm) ratio and the infrared spectra (IR) of DOM showed an aromatic behaviour in compost-soil (C-S); in contrast sewage sludge-soil (Sw-S) showed an aliphatic behaviour. Application of either Sw or C increased the Cu sorption capacity of soil. The Cd sorption decreased only in soil with a competitive metal system. The availability of Cu was low due to its occurrence in the acid soluble fraction (F3). The Cu concentration varied in accordance with the amounts of Cu added. The highest Cd concentration was found in the exchangeable fraction (F2). The Sw and C applications did not increase the Cd availability in the soil.     

A dynamic study of the sorption and the transport processes of cadmium in calcareous sandy soils

The interactions of Cd2+ with silica and calcite were observed through laboratory dynamic experiments. Cd2+ sorption processes were characterised as a function of reaction kinetics in aqueous solutions saturated or not with respect to calcite. Chromatographic column experiments show that Cd2+ sorption on silica can be considered as a reversible equilibrate reaction which depends on water composition and pH. For a porous medium composed by a mixture of silica and calcite, the Cd2+ migration behaviours are predominantly controlled by calcite. The amount and the reversibility of sorbed Cd on calcite are strongly affected by kinetic limitations. Stirred flow through reactor experiments provide an original method to separate and characterise the 'fast' and 'slow' Cd sorption on calcite processes. The 'fast' Cd reversible adsorption isotherms and the rate of Cd subsequent uptake by 'slow' reactions are determined. In addition, the inhibition of calcite dissolution is observed as a function of sorbed Cd in order to provide a complete mechanistic database for coupled transport-geochemistry models.     

Use of Natural 35S to Trace Sulphate Cycling in Small Lakes,Flattops Wilderness Area,Colorado, U.S.A.

Measurements of the cosmogenically-produced ³⁵S, a radioisotope of sulphur (t_1/2 = 87 days), are reported for the Ned Wilson Lake watershed in Colorado. The watershed contains two small lakes and a flowing spring presumed to be representative of local ground water. The watershed is located in the Flattops Wilderness Area and the waters in the system have low alkalinity, making them sensitive to increases in acid and sulphate deposition. Time series of ³⁵S measurements were made during the summers of 1995 and 1996 (July–September) at all three sites. The system is dominated by melting snow and an initial concentration of 16–20 mBq L^-1 was estimated for snowmelt based on a series of snow samples collected in the Rocky Mountains. The two lakes had large initial ³⁵S concentrations in July, indicating that a large fraction of the lake water and sulphate was introduced by meltwater from that year's snowpack. In 1995 and 1996, ³⁵S concentrations decreased more rapidly than could be accounted for by decay, indicating that other processes were affecting ³⁵S concentrations. The most likely explanation is that exchange with sediments or the biota was removing ³⁵S from the lake and replacing it with older sulphate devoid of ³⁵S. In September of 1995 and 1996, ³⁵S concentrations increased, suggesting that atmospheric deposition is important in the sulphate flux of these lakes in late summer. Sulphur-35 concentrations in the spring water were highly variable but never higher than 3.6 mBq L^-1 and averaged 2 mBq L^-1. Using a simple mixing model, it was estimated that 75% of the spring water was derived from precipitation of previous years.     

Effect of leachate recirculation on the migration of copper and zinc in municipal solid waste and municipal solid waste incineration bottom ash co-disposed landfill

Municipal solid waste incinerator (MSWI) bottom ash was allowed to be disposed of with municipal solid waste (MSW) in landfill sites in the recently enacted standard of China. In this study, three sets of simulated landfill reactors, namely, conventional MSW landfill (CL), conventional MSWI bottom ash and MSW co-disposed landfill (CCL), and leachate recirculated MSWI bottom ash and MSW co-disposed landfill (RCL), were operated to investigate the environmental impact of the co-disposal. The effect of leachate recirculation on the migration of Cu and Zn in the co-disposed landfill was also presented. The results showed that the co-disposal of MSWI bottom ash with MSW would not enhance the leaching of Cu and Zn from landfill. However, the co-disposal increased the Cu and Zn contents of the refuse in the bottom layer of the landfill from 56.7 to 65.3 mg/kg and from 210 to 236 mg/kg, respectively. The recirculation of the leachate could further increase the Cu and Zn contents of the refuse in the bottom layer of the landfill to 72.9 and 441 mg/kg, respectively. Besides these observations, the results also showed that the co-disposed landfill with leachate recirculation could facilitate the stabilization of the landfill.     

A mathematical model to predict the composition and generation of hospital wastes in Iran

The aim of this study is to investigate the quality and quantity of hospital wastes in Iran. The generated hospital wastes have been estimated by the number of hospitals and the number of active beds in each province of Iran in 2001. All data and information have been gathered from: (i) Iran Statistics Center, (ii) literature review, and (iii) hospital waste investigations for an average hospital. Physical analyses have been conducted in terms of various materials (plastic, textile, paper, metal, and others) and components (biological, infectious, medical, and regular wastes). Based on the above-mentioned investigation and information, a mathematical model has been developed to calculate the generation of (infectious) hospital wastes for any desired year. Utilizing the model, generated infectious hospital wastes has been estimated as 698,937 tones for 2008 (short-term) and 3,494,387 tones for 2028 (long-term period). If the real infectious wastes are collected separately, then the generated infectious wastes will be reduced by 15.1% of the above-mentioned amount (139,787 tones for 2008, and 698,877 tones for 2028). Results of physical analysis show the components of the hospital waste as: (a) infectious, 67.3%; (b) medical, 8.8%; (c) biological, 1.8%; and (d) common municipal wastes, 22.1%. An appropriate collection method requires training the staff at hospitals along with preparation of the required facilities. Of course, both of these requirements are cost intensive.     

Characterisation of major component leaching and buffering capacity of RDF incineration and gasification bottom ash in relation to reuse or disposal scenarios

Thermal treatment of refuse derived fuel (RDF) in waste-to-energy (WtE) plants is considered a promising solution to reduce waste volumes for disposal, while improving material and energy recovery from waste. Incineration is commonly applied for the energetic valorisation of RDF, although RDF gasification has also gained acceptance in recent years. In this study we focused on the environmental properties of bottom ash (BA) from an RDF incineration (RDF-I, operating temperature 850-1000 °C) and a RDF gasification plant (RDF-G, operating temperature 1200-1400 °C), by evaluating the total composition, mineralogy, buffering capacity, leaching behaviour (both at the material’s own pH and as a function of pH) of both types of slag. In addition, buffering capacity results and pH-dependence leaching concentrations of major components obtained for both types of BA were analysed by geochemical modelling. Experimental results showed that the total content of major components for the two types of BA was fairly similar and possibly related to the characteristics of the RDF feedstock. However, significant differences in the contents of trace metals and salts were observed for the two BA samples as a result of the different operating conditions (i.e. temperature) adopted by the two RDF thermal treatment plants. Mineralogy analysis showed in fact that the RDF-I slag consisted of an assemblage of several crystalline phases while the RDF-G slag was mainly made up by amorphous glassy phases. The leached concentrations of major components (e.g. Ca, Si) at the natural pH of each type of slag did not reflect their total contents as a result of the partial solubility of the minerals in which these components were chemically bound. In addition, comparison of total contents with leached concentrations of minor elements (e.g. Pb, Cu) showed no obvious relationship for the two types of BA. According to the compliance leaching test results, the RDF-G BA would meet the limits of the Italian legislation for reuse and the European acceptance criteria for inert waste landfilling. RDF-I BA instead would meet the European acceptance criteria for non hazardous waste landfilling. A new geochemical modelling approach was followed in order to predict the leaching behaviour of major components and the pH buffering capacity of the two types of slags on the basis of independent mineralogical information obtained by XRD analysis and the bulk composition of the slag. It was found that the combined use of data regarding the mineralogical characterization and the buffering capacity of the slag material can provide an independent estimate of both the identity and the amount of minerals that contribute to the leaching process. This new modelling approach suggests that only a limited amount of the mineral phases that control the pH, buffering capacity and major component leaching from the solid samples is available for leaching, at least on the time scale of the applied standard leaching tests. As such, the presented approach can contribute to gain insights for the identification of the types and amounts of minerals that control the leaching properties and pH buffering capacity of solid residues such as RDF incineration and gasification bottom ash.     

Modeling hydrology and reactive transport in roads: the effect of cracks, the edge, and contaminant properties

The goal of this research was to provide a tool for regulators to evaluate the groundwater contamination from the use of virgin and secondary materials in road construction. A finite element model, HYDRUS2D, was used to evaluate generic scenarios for secondary material use in base layers. Use of generic model results for particular applications was demonstrated through a steel slag example. The hydrology and reactive transport of contaminants were modeled in a two-dimensional cross section of a road. Model simulations showed that in an intact pavement, lateral velocities from the edge towards the centerline may transport contaminants in the base layer. The dominant transport mechanisms are advection closer to the edge and diffusion closer to the centerline. A shoulder joint in the pavement allows 0.03 to 0.45 m(3)/day of infiltration per meter of joint length as a function of the base and subgrade hydrology and the rain intensity. Scenario simulations showed that salts in the base layer of pavements are depleted by 99% in the first 20 years, whereas the metals may not reach the groundwater in 20 years at any significant concentrations if the pavement is built on adsorbing soils.     

Usefulness of TAO model to predict and manage the transformation in soil of carbon and nitrogen forms from West-Africa urban solid wastes

The TAO model of Transformation of Added Organic materials (AOM) calibrated on AOMs and substrates of temperate areas was used to assess the transformations in soil of carbon and nitrogen forms of AOMs: raw materials, selected mixtures and composts from Ouagadougou urban wastes. AOMs were studied in terms of chemical and biochemical contents and for their C and N mineralization during incubations in a typical Ferric Lixisol of the sub-urban agriculture of Ouagadougou. The TAO model was used to predict the transformations of C (very labile, resistant and stable organic C) and N (very labile, resistant and stable organic N, produced and immobilized inorganic N) forms driven by AOM biochemical data. Without any change in calibration formulae, TAO predicted accurately the C transformations and inorganic N production of most of the tested AOMs, with a tendency to slightly overestimate C mineralization of previously well-composted materials and re-mineralization of immobilized N. Complementary adjustments using more complete data from laboratory experiments are suggested, but the model agrees with other data collected in the field and appears as a promising tool to optimise the management of urban wastes in the tropical area as well as for agro industrial organic fertilizers of the temperate zone. This application suggests ways to improve the management of urban wastes aiming to optimize agricultural yields, system sustainability and C sequestration in soil.     

Activated carbon from Ceiba pentandra hulls, an agricultural waste, as an adsorbent in the removal of lead and zinc from aqueous solutions

The ability of low-cost activated carbon prepared from Ceiba pentandra hulls, an agricultural waste material, for the removal of lead and zinc from aqueous solutions has been investigated. In the batch tests experimental parameters were studied, including solution pH, contact time, adsorbent dose and initial metal ions concentration. The adsorbent exhibited good sorption potential at pH 6.0. Maximum removal of lead (99.5%) and of zinc (99.1%) with 10 g/l of sorbent was observed at 50 mg/L sorbate concentration. Removals of about 60-70% occurred in 10 min, and equilibrium was attained at around 50 min for both metals. The functional groups (CO, SO,-OH) present on the carbon surface were responsible for the adsorption of metal ions. The adsorption parameters were analysed using both the Freundlich and Langmuir models. The data are better fitted by the Freundlich isotherm as compared to Langmuir model, and the adsorption capacities for lead and zinc were 25.5 and 24.1 mg/g, respectively. Kinetics of adsorption obeyed a second order rate equation and the rate constant was found to be 2.71 x 10(-2) and 2.08 x 10(-2) g/mg/min for lead and zinc, respectively. The desorption studies were carried out using dilute HCl, and the effect of HCl concentration on desorption was studied. Maximum desorptions of 85% for lead and 78% for zinc were attained with 0.15 M HCl.     

GHG emission factors developed for the collection,transport and landfilling of municipal waste in South African municipalities

Greenhouse gas (GHG) emission factors are used with increased frequency for the accounting and reporting of GHG from waste management. However, these factors have been calculated for developed countries of the Northern Hemisphere and are lacking for developing countries. This paper shows how such factors have been developed for the collection, transport and landfilling of municipal waste in South Africa. As such it presents a model on how international results and methodology can be adapted and used to calculate country-specific GHG emission factors from waste. For the collection and transport of municipal waste in South Africa, the average diesel consumption is around 5 dm³ (litres) per tonne of wet waste and the associated GHG emissions are about 15 kg CO₂ equivalents (CO₂ e). Depending on the type of landfill, the GHG emissions from the landfilling of waste have been calculated to range from ?145 to 1016 kg CO₂ e per tonne of wet waste, when taking into account carbon storage, and from 441 to 2532 kg CO₂ e per tonne of wet waste, when carbon storage is left out. The highest emission factor per unit of wet waste is for landfill sites without landfill gas collection and these are the dominant waste disposal facilities in South Africa. However, cash strapped municipalities in Africa and the developing world will not be able to significantly upgrade these sites and reduce their GHG burdens if there is no equivalent replacement of the Clean Development Mechanism (CDM) resulting from the Kyoto agreement. Other low cost avenues need to be investigated to suit local conditions, in particular landfill covers which enhance methane oxidation.     

Exposure assessment of lead to workers and children in the battery recycling craft village,Dong Mai,Vietnam

Human exposure to lead (Pb) due to uncontrolled Pb-acid battery recycling has been an environmental health issue in newly developed industrial regions. We conducted a human monitoring survey in Dong Mai, a battery recycling village in Vietnam, to assess exposure status to Pb. Lead level was measured in hair, blood and urine samples of residents in Dong Mai and two reference sites during 4 years spanning 2007–2011. In Dong Mai, Pb levels in three matrixes were significantly higher than those in reference sites. Blood Pb levels of all adults and children exceeded 10 μg/dL, the Centers for Disease Control and Prevention definition of an elevated blood Pb level. Clear increase of urinary δ-aminolevulinic acid (ALA) level with increasing blood Pb level indicated disruption of heme synthesis. One adult exceeded 100 μg/dL of blood Pb, where encephalopathy is of concern. The blood Pb levels achieved various toxic effect threshold values, and elevated blood Pb was not limited to recycling workers, but was also in children and women of reproductive age. Serious pollution status of Dong Mai village suggests an importance of further monitoring surveys in various developing Asian countries.