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In this study. Baghdad hospital waste ash was analyzed to determine the type of heavy and toxic concentrations in the waste and to study the potential effects of radioactive waste, health risks and the effectiveness of S/S hardening/stabilization processes based on local cement. Toxic medical waste was used in this work as bottom ash, which includes large amounts of pollutants such as As, Co, Cr, and Hg. Ash samples were taken from the medical waste incinerators of the main hospital in the city. The heavy metal sludge is stabilized and solidified using this bottom ash. The curing matrix was between 7% and 25% local cement in varying amounts. Before arriving at the physical and chemical properties of the solid, it underwent six different periods of treatment. Filtration experiments using solid-liquid partitioning as a function of pH, the filtration method was deployed to determine treatment efficiency. The compressive strength confined to the forms was also measured to ensure the solidity and durability of the molds. After disposal, the most effective solid material with good strength was found, which contains 25% of local cement. In addition, the results of the study showed that the efficiency of treating the filtration method for toxicological properties Ranging from 85% to 100%. The range of treatment efficiency in liquid/solid technology was 75%-100%. The S/S process can be a very good, effective and safe treatment process for handling and disposing of toxic medical waste ash or the possibility of reusing the formwork in bridges and roads. [ABSTRACT FROM AUTHOR]

• Dextran carbamate derivatives were synthesized as building blocks for preparing nanocapsules. • Corrosion inhibitors were loaded in dextran and dextran carbamate nanocapsules by the inverse miniemulsion process. • Release profiles depended on the chemical structure of the dextran derivatives, solubility of payload, and pH values. Controlled release of payloads such as drugs or corrosion inhibitors from nanocapsules is a prerequisite for their utilization. Indeed, premature leaching and contamination of the environment can be avoided. Herein, we investigate the pH-dependence of release kinetics of corrosion inhibitors from nanocapsules. Nanocapsules are formed by interfacial crosslinking of dextran derivatives in inverse miniemulsion and subsequently re-dispersed in aqueous solutions. Release kinetics are highly dependent on pH value and can be explained by a complex interplay involving swelling of nanocapsules shell, solubility of corrosion inhibitors, and electrostatic interactions between payloads and the shell. [ABSTRACT FROM AUTHOR]

Disposal of fly ash produced in a large quantity is a major problem in coal fired thermal power plants. The coal quality depends upon its rank and grade. Fly ash content in Indian coal ranges from 35% to 50% consisting of a variety of toxic elements including heavy metals that damage the surrounding environment. During transportation, disposal and storage phases, the residues from coal combustion may pollute both ground and surface waters through leaching. The fly ash enriched in Ca, Ni and Fe showed greater leachability in acidic or ion exchangeable conditions. Principal mechanisms of metal leachability are the dissolution of primary solids under aggressive environment and/or precipitation sorption reactions, which are primarily dependent on pH. Fe is found to be tightly bound to the ash and does not leach easily while Ca is highly soluble and leaches out almost all the mediums. The leachabiltiy of trace elements in fly ash is time dependent and pH values of the leachant. [ABSTRACT FROM AUTHOR]

The aims of this study correspond to (i) determine the feasibility of synthesize geomaterial from two main Pb-contaminated mining sediments (Sed1 and Sed2) without prior activation in substitution to metakaolin (MK), (ii) understand the mechanisms involved toward two types of silicate solution (Na and K one), and (iii) to evaluate the change in the Pb metallic element speciation and leaching after alkali treatment. The raw material as well as consolidated material were characterized by X-ray diffraction, infrared spectroscopy, and electron microscopy. The mechanical properties were evaluated, and the leaching behavior realized according to EN12457-2. The results evidence the limit of mining sediment incorporation by substitution near 50% whatever the sediments and the alkaline solution used. There is no difference in the mechanical properties up to 10% substitution then decrease with the increase of sediment content. The Pb-bearing phases are dissolved during alkaline treatment and redistributed in the geomaterial matrix. Finally, the leaching experiments clearly evidenced the possibility to stabilize Pb into MK-based geomaterial matrix up to 25–30% weight of mine waste. [ABSTRACT FROM AUTHOR]

Alterations in the timing, frequency, and magnitude of water level fluctuations (WLF) in lakes may result in important changes in abiotic parameters that can affect sediment-borne contaminant mobility at the sediment-water-biota interfaces in littoral zones. This study aims to assess the mobility of trace metals (TMs)—Cd, Cr, Cu, Ni, Pb, and Zn—under laboratory-simulated WLF (i.e., drying and reimmersion of sediments) through a three-pronged approach. One surficial sediment was sampled from the shoreline of a large French lake exhibiting an artificially limited WLF. A sample was enriched with a solution of TMs to ensure significant measurements of mobility. The spiked and naturally contaminated sediments were dried and reimmersed. The first approach consisted in measuring the mobility of TMs from the sediment to the water column under resuspensions of particles through leaching tests. The second approach assessed the partitioning of TMs between the different binding forms within the sediments through sequential extraction tests. The last approach tested the changes in TM bioconcentration in organisms exposed to sediment through microcosm assays. The hypothesis was that WLF may increase mobility from the sediment to the water column relative to mobility from the residual to easily mobilizable fractions within the sediments and consequently increase the bioconcentration of less inert trace metals, mostly Cd and Zn. This hypothesis was partly rejected as TM binding forms mainly increased toward the residual fractions within the sediment, especially for Cd and Zn, and bioconcentration mainly decreased following WLF. However, TM concentration increased in the water column when WLF included great resuspension of particles. The study also provides insights into the complex relationships among contaminant mobility to the water column, bioavailability, and bioconcentration, especially in the context of large abiotic disturbances such as WLF. These findings may be useful for further management strategies for WLF-regulated lakes and reservoirs. [ABSTRACT FROM AUTHOR]

Limitations of the toxicity characteristic leaching procedure (TCLP) for simulating pollutant leaching from wastes disposed of in full-scale landfills are well understood in the waste management profession; the TCLP solution has a lower pH and greater organic acid content than typical landfill leachate. The TCLP serves its intended regulatory objective, however, as long as a conservative estimate of leaching is provided. Here, we examine TCLP's ability to represent worst-case leaching conditions for monofilled municipal solid waste incineration (MSWI) ash. A critical examination of TCLP's applicability to MSWI ash is especially relevant, as ash management at MSWI facilities often centers on passing TCLP, regardless of environmental risk posed by the ash or its recyclability. Multiple batch leaching tests were conducted on different MSWI ash streams: mixed ash, fly ash, and different size fractions of bottom ash. Batch-test results were compared with leachate simulating MSWI ash monofills. The TCLP did not consistently provide the most conservative estimate of leaching, supporting the need to consider alternative methodologies in future regulatory development. Implications: This paper analyzes the existing hazardous waste regulatory testing requirement for municipal solid waste incinerator (MSWI) ash management to evaluate whether the TCLP serves its intended purpose in providing the most conservative estimate of landfilled MSWI ash. The results will serve as guidance and motivation for policy makers and the regulatory community to reevaluate the TCLP's application for characterizing MSWI ash leaching in certain disposal scenarios and could promote consideration of alternative testing procedures based upon results of this study. This study serves to promote representative and accurate quantification of leaching risk from MSWI ash. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) releasing polymers have been widely applied as biomaterials for a variety of biomedical implants and devices. However, the chemical leaching of NO donors and their byproduct species is almost always observed during the application of polymers doped with NO donors, unless the donor is covalently linked to the polymer. Herein, we report the first NO releasing poly(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP) fluorinated copolymer prepared by incorporating a fluorinated S -nitrosothiol as the NO donor. Under physiological conditions, the resulting polymeric films can release NO for 16 days. Importantly, due to both fluorine-fluorine and electrostatic charge interactions between the fluorinated NO donor and the PVDF-HFP copolymer, the total chemical leaching of the fluorinated NO donor and its disulfide product after 9 day was only 0.6% (mol%) of the initial amount of NO donor loaded into the film. These new NO release PVDF-HFP films exhibit antimicrobial and anti-biofilm activities against both Gram positive S. aureus and Gram negative P. aeruginosa strains. The NO-releasing PVDF-HFP polymer can also be coated on Teflon tubing to release NO under physiological conditions for extended time periods. This NO-releasing PVDF-HFP copolymer with greatly reduced chemical leaching could help enhance the biocompatibility and antimicrobial activity of various biomedical devices. Fluoropolymers have been widely used in creating various biomedical implants and devices. However, nitric oxide (NO) release fluoropolymers have not been well studied to date. Additionally, in the application of biomaterials doped with NO donors, a significant amount of NO donors and their byproducts almost always leach into aqueous environment. We now report an NO releasing poly(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP) fluoropolymer by incorporating a new fluorinated S -nitrosothiol. The NO release can last for 16 days under physiological conditions. The total chemical leaching was determined to be only 0.6 mol% of the initial S -nitrosothiol loaded. As expected, significant antimicrobial/anti-biofilm activities of the NO release PVDF-HFP film were observed against Gram positive S. aureus and Gram negative P. aeruginosa bacterial strains. [ABSTRACT FROM AUTHOR]

Highlights • NO 3 -N leaching was two orders of magnitude less below a perennial grain than maize. • Soil solution NO 3 -N was lower beneath a perennial grain than maize and switchgrass. • N fertilizer increased perennial grain yield without increasing NO 3 -N leaching. Abstract Global expansion of high-input annual grain crops and associated nitrogen (N) fertilizer use can have negative consequences for the environment and human health. Nitrate nitrogen (NO 3 -N) leaching from fertilized annual crops can contaminate groundwater and pollute natural aquatic ecosystems and rural drinking water sources. Intermediate wheatgrass (IWG; Thinopyrum intermedium) is a perennial grass being domesticated to serve as the world's first widely available perennial grain crop. Our objective was to measure water quality variables and crop yields in order to model NO 3 -N leaching beneath IWG, maize, and switchgrass under three N fertilizer treatments; low N (0 kg N ha−1), medium N (maize = 80, switchgrass and IWG = 40 kg N ha−1), and high N (maize = 160, switchgrass and IWG = 120 or 160 kg N ha−1). The switchgrass and IWG medium N treatments also included alfalfa as an intercrop. The NO 3 -N concentration in soil solution 50 cm below the surface was one and two orders of magnitude lower in high N fertilized IWG compared to switchgrass and maize, respectively. Soil solution NO 3 -N increased with N fertilizer in all crops. Soil water content was less at 50 and 100 cm depths in IWG compared to switchgrass and maize but was unaffected by N fertilizer treatment. Using the Denitrification and Decomposition (DNDC) model, average annual NO 3 -N leaching estimates in the high N treatments were 21.7 kg N ha−1 for maize and 3.7 and 0.2 kg N ha−1 for switchgrass and IWG, respectively. Despite consistent biomass yields through time, IWG grain yields decreased with stand age at all N fertilizer treatments. Alfalfa did not persist in the IWG and switchgrass medium N treatments, thus other legumes should be tested for intercropping with perennial grain crops. Intermediate wheatgrass has great potential to provide food-quality grain and biomass while preventing NO 3 -N leaching. [ABSTRACT FROM AUTHOR]

Highlights • Laboratory centrifugal dense media separation was tested on Pb-Zn mine tailings. • High metal recoveries and upgrade ratios were obtained. • Centrifugal dense media separation can serve as a depollution technique for base-metal mine tailings. • The separation efficiency was assessed by the Toxicity Characteristic Leaching Procedure environmental test. Abstract The management of mine tailings has become a worldwide environmental concern. In fact, with the more restrictive environmental regulations, there is a pressing need to develop efficient and clean techniques to properly manage these industrial wastes. This work investigates the use of centrifugal Dense Medium Separation (DMS) as a depollution process of Pb-Zn tailings in order to reduce their residual metal content. The obtained results showed that DMS technique allowed high recovery of cerussite (PbCO 3) and smithsonite (ZnCO 3) present in the studied tailings. Consequently, it has successfully depolluted the studied mine tailings. The effectiveness of DMS was accessed both by the Separation Efficiency (SE) factor and the Toxicity Characteristic Leaching Procedure (TCLP) environmental test. The recoveries of Zn and Pb to the heavy fraction are 88.83% and 91.66% respectively. The observed concentrations of contaminants in TCLP leachates from the light fraction, consisted mainly of dolomite and silicates (quartz, orthoclase, albite and chlorite), are below the limits authorized by the US-EPA regulation for non-hazardous wastes. The DMS allowed a reduction of the concentration of leached Pb by more than 95% in both tailings, and a reduction of the concentration of leached Zn by more than 78% in the case of Bb tailings. [ABSTRACT FROM AUTHOR]

Abstract Recently, glycine, one of the simplest amino acids, has been emerging as an efficient and environmental-friendly lixiviant for copper leaching. In the present study, an alkaline glycine–peroxide lixiviant system was used to leach copper from chalcopyrite concentrate by a suite of kinetic studies under different conditions. The particle size of the concentrate was P80 40 μm. Glycine concentration was varied from 0.5 to 3.0 M (glycine to copper molar ratio of 1.1 to 6.6:1) and the pH was maintained at 11 during the experiment. The copper extraction within 96 h was observed from 13 to 14% with glycine concentrations from 0.5 to 2 M, while the copper extraction decreased at 3 M of glycine. By reconstituting the glycine concentration during the leach test and adding hydrogen peroxide periodically, the copper extraction with 1 M glycine at 96 h increased from 14 to 21%, respectively. By changing the glycine and hydrogen peroxide solution every 24 h, 42% of copper extraction was achieved within 168 h. With increasing temperature, copper extraction decreased, while iron dissolution increased. Copper sulfide and copper sulfate precipitates were found in the leaching liquor at 22 °C test. Poorly crystalline copper-iron sulfate phase was observed in the leaching liquor at 35 and 45 °C. This precipitation is believed to be one of the factors to decrease the copper recovery from chalcopyrite. Highlights • An alkaline glycine-peroxide system was used to leach copper from chalcopyrite. • Leaching mechanisms were investigated by a suite of kinetic studies. • The copper extraction decreased with increasing temperature. • Copper sulfide or sulfate precipitates were found in the leaching liquor at 22 °C. • Poorly crystalline copper‑iron sulfate precipitates were observed at 35 and 45 °C. [ABSTRACT FROM AUTHOR]

Abstract Organic sulfur in coal is usually integrated with macromolecular skeleton structure of organic components and hence difficult to remove through physical separation. Chemical leaching and biological treatments are considered as the effective methods for the removal of organic sulfur from coal, however these treatment processes require huge investment and long treatment period. In this paper, low rank coal co-pyrolysis with reduced iron powder (Fe powder) and then followed by dry magnetic separation was used to reduce the sulfur content of low rank coal. After dry magnetic separation, the organic sulfur content can be reduced from 2.00% for low rank coal before the pyrolysis to 0.33% for the coal after 700 °C co-pyrolysis with Fe powder at the coal/Fe-powder mass ratio of 4:1. However, the organic sulfur content can be only reduced to 1.28% for the coal after 700 °C pyrolysis without Fe powder. The Fe powder can promote/enhance the decomposition of organic sulfur and the released sulfur can be bonded with Fe powder to form the sulfocompounds which is separated along with the Fe powder during dry magnetic separation. X-ray photoelectron spectroscopy was used to indicate the sulfur forms in the separated Fe powder (namely magnetic tailings) and showed the magnetic tailings contained more FeS and FeS 2 compounds than the Fe powder before the pyrolysis. The magnetic tailings contained about 4.6% sulfur content at the co-pyrolysis temperature of 700 °C while the sulfur content of the Fe powder before the pyrolysis was nearly zero. A large proportion of organic sulfur was transferred to the Fe powder and then was separated along with the magnetic tailings by dry magnetic separation. Highlights • Fe powder significantly promote the removal of organic sulfur from low rank coal. • Coal/Fe-powder mass ratio was optimized at 4:1 at 500 °C pyrolysis. • Pyrolysis temperature was optimized at 700 °C at coal/Fe-powder mass ratio of 4:1. • A large proportion of organic sulfur in coal is transferred to the Fe powder. • Plenty of Fe-related compounds (FeS, FeS 2) can be formed in pyrolysised Fe powder. [ABSTRACT FROM AUTHOR]

Abstract Spent pot-lining from aluminum electrolysis and coal gangue are toxic and hazardous solid wastes with high recovery value and contents of valuable elements, such as carbon, silicon, aluminum and fluorine. Thus, harmless treatment and recycling of these materials are of considerable importance. For extracting valuable components, Spent pot-lining and coal gangue were co-treated by hydrothermal acid-leaching method in this study. Effect of adding spent pot-lining on impurities leaching rate of coal gangue was systematically studied, and results indicated that fluoride in spent pot-lining positively affected the decomposition of coal gangue. Moreover, effects of leaching temperature, initial acid concentration, time, and particle size, on the extraction efficiency of aluminum were investigated comprehensively. Optimum parameters obtained by single-factor test included reaction temperature of 200 °C, initial hydrochloric acid concentration of 10 mol/L, time of 10 h, liquid–solid ratio of 10:1, and particle size below 200 mesh. Under these conditions, leaching rate of aluminum reached to 92.47%. Acid-leaching residue was used in the preparation of silicon carbide powder by carbothermal reduction, and silicon carbide powder with small size (D 50 , the median diameter, of 18.15 μm) was obtained by firing the acid-leaching residue at temperature of 1600 °C for 5 h. This study provides an inspiring approach for recovering and reusing spent pot-lining and coal gangue. Graphical abstract Image Highlights • SPL and CG were co-treated by hydrothermal acid-leaching process at one step harmlessly. • Fluoride in SPL positively affected the decomposition of CG and improved the leaching rate of aluminum. • Leaching residue was successfully used in preparation of SiC instead of pure carbon and silica powder. [ABSTRACT FROM AUTHOR]

Abstract Because over 60% of the total energy consumed in conventional mining consists of excavating, hauling, and liberating processes, the energy consumption in conventional methods of mining has increased exponentially with the decline in global ore-grades. In-situ leaching (ISL) is an alternative mining technology, which eliminates these processes. However, ISL is currently limited to porous rock. Expansion of ISL to impervious mineral bearing rocks requires controlled, artificial fracture stimulation and the current practice of hydraulic fracturing is not compatible due to the associated environmental impacts and uncontrolled fracture propagation. Therefore, to extend the application of ISL to impervious rocks, an alternative fracturing method using Soundless Cracking Demolition Agents (SCDAs), which is capable of producing controlled fractures in a rock mass, is proposed in this study. With the aim of understanding the fracturing performance of SCDA under in-situ stress conditions prevalent in ISL environments, a 3D numerical model for SCDA charging was produced using Particle Flow Code (PFC3D 5.0) and validated with experimentally obtained data. The model was then extended to investigate the fracture mechanism of SCDA charging at various confining pressures of 5, 10, 15, and 20 MPa. Simulation results suggest that during SCDA charging, the number of radial fracture propagations and the total fracture damage in the rock mass increase with the confinement and the fracture pattern is dependent on the confining stress of the surrounding rock. In comparison to a hydraulically fractured specimen with identical dimensions, the fracture density of SCDA charged specimen showed a ten-fold increase at high confining pressures (20 MPa). Furthermore, as opposed to an uncontrolled, unidirectional diametrical fracture generated by hydraulic fracturing, SCDA charging produces multiple radial fractures around the injection well facilitating better spatial distribution of fluid flow for ISL. The results of this study imply that SCDA charging produces a denser and a controllable fracture network compared to hydraulic fracturing, which could potentially expand ISL applications to impervious rocks. [ABSTRACT FROM AUTHOR]

Speciations of metals were assessed in a tropical rain-fed river, flowing through the highly economically important part of the India. The pattern of distribution of heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) were evaluated in water and sediment along with mineralogical characterization, changes with different water quality parameters and their respective health hazard to the local population along the Damodar River basin during pre-monsoon and post-monsoon seasons. The outcome of the speciation analysis using MINTEQ indicated that free metal ions, carbonate, chloride and sulfate ions were predominantly in anionic inorganic fractions, while in cationic inorganic fractions metal loads were negligible. Metals loads were higher in sediment phase than in the aqueous phase. The estimated values of Igeo in river sediment during both the seasons showed that most of the metals were found in the Igeo class 0-1 which represents unpolluted to moderately polluted sediment status. The result of partition coefficient indicated the strong retention capability of Cr, Pb, Co and Mn, while Cd, Zn, Cu and Ni have resilient mobility capacity. The mineralogical analysis of sediment samples indicated that in Damodar River, quartz, kaolinite and calcite minerals were dominantly present. The hazard index values of Cd, Co and Cr were > 1 in river water, which suggested potential health risk for the children. A combination of pragmatic, computational and statistical relationship between ionic species and fractions of metals represented a strong persuasion for identifying the alikeness among the different sites of the river. [ABSTRACT FROM AUTHOR]

The emissions of nitrous oxide (N2O) and leaching of nitrate (NO3) have considerable negative impacts on climate and the environment. Although these environmental burdens are on average less per unit area in organic than in non-organic production, they are not smaller per unit of product. If organic farming is to maintain its goal of being an environmentally friendly production system, these emissions should be mitigated. We discuss the impact of possible triggers within organic arable farming practice for the risk of N2O emissions and NO3 leaching under European climatic conditions, and possible strategies to reduce these. Organic arable crop rotations can be characterised as diverse with frequent use of legumes, intercropping and organic fertilizers. The soil organic matter content and share of active organic matter, microbial and faunal activity are higher, soil structure better and yields lower, than in non-organic, arable crop rotations. Soil mineral nitrogen (SMN), N2O emissions and NO3 leaching are low under growing crops, but there is high potential for SMN accumulation and losses after crop termination or crop harvest. The risk for high N2O fluxes is increased when large amounts of herbage or organic fertilizers with readily available nitrogen (N) and carbon are incorporated into the soil or left on the surface. Freezing/thawing, drying/rewetting, compacted and/or wet soil and mixing with rotary harrow further enhance the risk for high N2O fluxes. These complex soil N dynamics mask the correlation between total N-input and N2O emissions from organic arable crop rotations. Incorporation of N rich plant residues or mechanical weeding followed by bare fallow increases the risk of nitrate leaching. In contrast, strategic use of deep-rooted crops with long growing seasons in the rotation reduces nitrate leaching risk. Reduced tillage can reduce N leaching if yields are maintained. Targeted treatment and use of herbage from green manures, crop residues and catch crops will increase N efficiency and reduce N2O emissions and NO3 leaching. Continued regular use of catch crops has the potential to reduce NO3 leaching but may enhance N2O emissions. A mixture of legumes and non-legumes (for instance grasses or cereals) are as efficient a catch crop as monocultures of non-legume species. [ABSTRACT FROM AUTHOR]

The safety of drinking water remains a major challenge in developing countries and point-of-use (POU) drinking water treatment device plays an important role in decentralised drinking water safety. In this study, a novel material, i.e. a silver nanowires-polyacrylonitrile/thermoplastic polyurethane (AgNWs-PAN/TPU) composite membrane, was fabricated via electrospinning and vacuum filtration deposition. Morphological and structural characterisation showed that the PAN/TPU fibres had uniform diameters and enhanced mechanical properties. When added to these fibres, the AgNWs formed a highly conductive network with good physical stability and low silver ion leaching (<100 ppb). A POU device equipped with a AgNWs-PAN/TPU membrane displayed complete removal of 10 5  CFU/mL bacteria, which were inactivated by silver ions released from the AgNWs within 6 h. Furthermore, under a voltage of 1.5 V, the bacteria were completely inactivated within 20–25 min. Inactivation efficiency in 5 mM NaCl solution was higher than those in Na 2 SO 4 and NaNO 3 solutions. We concluded that a strong electric field was formed at the AgNW tips. Additionally, silver ions and chlorine compounds worked synergistically in the disinfection process. This study provides a scientific basis for research and development of silver nanocomposite membranes, with high mechanical strength and high conductivity, for POU drinking water disinfection. [ABSTRACT FROM AUTHOR]

Recycling of incineration bottom ashes (IBA) is attracting great interest as it is considered as a vital aspect for closing the waste loop to achieve sustainable development at the growing cities around the world. Various laboratory-testing methods are developed to assess the release potential of heavy metals – one of the most important concerns of using IBA, by reflecting the release conditions of heavy metals from IBA based on the targeted land reclamation application scenarios and corresponding environmental conditions. However, realistic release of the concerned elements in actual application with the presence of complex environment could possibly deviate from the outcomes produced by leaching tests carried out in the laboratory. Hence, a set of large-scale column trial experiments was performed to experimentally determine the effective release of heavy metals, when IBA is used as a filling material in land reclamation. 20 tons of IBA and 320 m 3 of seawater were used in six column trial experiments. The release of 13 heavy metal elements was analyzed through multiple aspects which included kinetics of release, distribution of elements in seawater and the impacts of two different dumping methods, with and without application of a chute. After dumping of IBA into the seawater, almost instantaneous release of heavy metals with uniform horizontal dispersion was observed. Higher concentration of these elements was observed near the bottom of the column, especially when a chute was applied. Comparative analysis was then carried out to establish relationships between the results obtained from the column trial with batch leaching test carried out in the laboratory. Distinctive relationships were observed for different heavy metals which suggests the need of pursuance of further understanding on leaching of IBA in real application scenario and complex environment. [ABSTRACT FROM AUTHOR]

Soil pore waters are a vital component of the ecosystem as they are efficient tracers of mineral weathering, plant litter leaching, and nutrient uptake by vegetation. In the permafrost environment, maximal hydraulic connectivity and element transport from soils to rivers and lakes occurs via supra-permafrost flow (i.e. water, gases, suspended matter, and solutes migration over the permafrost table). To assess possible consequences of permafrost thaw and climate warming on carbon and Green House gases (GHG) dynamics we used a “substituting space for time” approach in the largest frozen peatland of the world. We sampled stagnant supra-permafrost (active layer) waters in peat columns of western Siberia Lowland (WSL) across substantial gradients of climate (−4.0 to −9.1 °C mean annual temperature, 360 to 600 mm annual precipitation), active layer thickness (ALT) (>300 to 40 cm), and permafrost coverage (sporadic, discontinuous and continuous). We analyzed CO 2 , CH 4 , dissolved carbon, and major and trace elements (TE) in 93 soil pit samples corresponding to several typical micro landscapes constituting the WSL territory (peat mounds, hollows, and permafrost subsidences and depressions). We expected a decrease in intensity of DOC and TE mobilization from soil and vegetation litter to the supra-permafrost water with increasing permafrost coverage, decreasing annual temperature and ALT along a latitudinal transect from 62.3°N to 67.4°N. However, a number of solutes (DOC, CO 2 , alkaline earth metals, Si, trivalent and tetravalent hydrolysates, and micronutrients (Mn, Co, Ni, Cu, V, Mo) exhibited a northward increasing trend with highest concentrations within the continuous permafrost zone. Within the “substituting space for time” climate change scenario and northward shift of the permafrost boundary, our results suggest that CO 2 , DOC, and many major and trace elements will decrease their concentration in soil supra-permafrost waters at the boundary between thaw and frozen layers. As a result, export of DOC and elements from peat soil to lakes and rivers of the WSL (and further to the Arctic Ocean) may decrease. [ABSTRACT FROM AUTHOR]

The use of organophosphate pesticides (OPPs) to protect a variety of crops has increased in Bangladesh. OPPs may contaminate surrounding aquatic environments through several routes including spray drift, surface runoff and groundwater leaching. Since it is unknown how much OPP end ups in aquatic environment in Bangladesh, the objectives of the present study were to quantify the residues of ten most commonly used OPPs in water and sediment of water bodies of north-west Bangladesh and to assess their ecological risks for aquatic organisms. The risks of the pesticides in surface water and sediment were assessed using a first-tier risk quotient (RQ) approach. The higher-tier PERPEST model was used to refine the ecological risks of pesticides when RQ indicated a potential risk. Results showed the most frequently detected pesticides that appeared in high concentrations were chlorpyrifos, diazinon and quinalphos in surface water and sediment. The highest concentration of OPPs measured in water was 9.1 μg chlorpyrifos/L (median of 1.95 μg/L), while this was 51 μg diazinon/kg dw (median of 11 μg/kg dw) for sediment. Furthermore, results showed high acute and/or chronic RQs (RQ > 1) in surface water and sediment for chlorpyrifos, diazinon, quinalphos, malathion and fenitrothion. The higher-tier PERPEST model confirmed risks of chlorpyrifos, diazinon, quinalphos and fenitrothion for aquatic insects, micro- and macro-crustaceans which were previously derived by RQ-based risk assessment for aquatic organisms. Furthermore, the results of the PERPEST model also indicated possible indirect effects of these pesticides on algae and macrophytes, community metabolism, rotifers and other macro-invertebrates. [ABSTRACT FROM AUTHOR]

Understanding nitrogen and phosphorus leaching rates is critical for controlling non‐point source pollution. As of now, no studies have dealt with the spectrums of N or P leaching loss, a new concept is suggested in the present study, which can be used to assess the risks of N or P leaching loss. The spectrums of N or P leaching loss consist of the highest leaching loss (HLLr), mean leaching loss (MLLr), lowest leaching loss (LLLr), lowest leaching loss at an upper limit (LLLU), and lowest leaching at a lower limit (LLLL), and annual average of the lowest leaching loss (AALLL) and annual average of different‐level leaching loss (AADLL). These indices are tested with leaching experiments with distilled water, lysimeters, and PVC‐pipe method based on Darcy's law on seven land‐use types in the Dachong karst watershed in China. LLLL is similar among all land‐use types, except vegetable land. Four types of forests show few differences in LLLU and LLLL. HLLr, MLLr and LLLr, and AALLL and AADLL in the croplands are clearly greater than those in the forests. The HLLr of total nitrogen in vegetable land is highest (16.08 mg L−1) but the HLLr of nitrate nitrogen, ammonium nitrogen, and total phosphorus in paddy field are highest (11.01, 1.39, and 0.3 mg L−1, respectively). LLLr, MLLr, and HLLr in the same type of land use are one to three times higher than LLLU in N leaching loss. The spectrums intuitively show differences in N and P leaching losses among land‐use types in the karst watershed in China. [ABSTRACT FROM AUTHOR]

Bio-oxidation technology for leaching sulfide mineral of refractory gold concentrate is cleaner than conventional methods. Although liquid agitation can maintain cells and particles in suspension, thereby improving the mass transfer efficiency of oxygen, carbon dioxide, and nutrients, it also generates shear stress, which can reduce bio-oxidation reaction efficiency by destroying shear sensitive cells. In this study, a multiphase Eulerian model with the standard k - ε equation and auxiliary models were evaluated based on previously conducted experiments investigating two and three phase flows of gas-liquid, solid-liquid and gas-liquid-solid. The predicted shear stress on bacteria, gas holdup, bubble diameter and turbulence energy dissipation rate were then calculated by these models to reveal the key factors influencing bio-leaching efficiency and to analyze the primary region in which cell death occurs. The results showed that shear stress on bacteria in the impeller region is higher than in other regions. Based on the results of the study, an optimal operation condition was applied to bio-oxidation technology investigations. Comparing with classic roasting technology, bio-oxidation technology completely eliminates toxic gas emissions, reduces 4.3tons of wastewater per ton of refractory gold concentrate and reduces the leaching toxicity of total arsenic in the solid waste from 0.57 mg/L to 0.36 mg/L. It is demonstrated that bio-oxidation technology is cleaner and more eco-friendly than classic roasting technology. This work provides guidance for further study and designation of the stirred bioreactor scale-up in both biochemical and environmental engineering applications. [ABSTRACT FROM AUTHOR]

Naturally-occurring uranium can be found at elevated concentrations in groundwater throughout the world, with the potential to cause kidney damage in chronically exposed individuals. Empirical evidence shows that uranium mobilization can be enhanced in the presence of ions that are associated with leachate from construction and demolition (C&D) disposal sites. There is need for a simple and effective procedure to evaluate soil and rock formations for uranium mobility prior to the permitting of waste disposal facilities which could alter groundwater chemistry. A series of leachate extractions were performed to represent the impact of C&D leachate on uranium-bearing rocks, focusing on the impact of calcium, sodium, chloride, sulphate, and bicarbonate concentrations on uranium mobilization. Based on these observations a uranium leaching procedure (ULP) was developed and compared to the synthetic precipitation leaching procedure (SPLP). The ULP was capable of mobilizing an order of magnitude more uranium than the SPLP from six rock samples and shows promise as a tool for assessing the risk of groundwater contamination by C&D waste through uranium mobilization. [ABSTRACT FROM AUTHOR]

In the present study, the long-term leaching behaviors of heavy metals in the cement composites prepared by the municipal solid wastes incineration (MSWI) bottom ash are evaluated based on the modified NEN 7375 protocol. The leaching test of the compact and ground cement composites were performed in both the deionized water and saline water for 180 days. The results showed that the heavy metals investigated could be classified into three categories according to their leaching behaviors. In the first category, the concentrations of Cu, Cd, Pb, As, V and Ba in the leachate increased with the leaching time. Zn and Sn can be included into the second category, because a decline in their leaching concentrations was observed after the initial increase. In the third category, the concentration of Ni in the leachate decreased initially, but increased afterward. The results revealed that the concentrations of most heavy metals were within the corresponding regulation, except for As in saline water. The kinetic study revealed that, for most heavy metals, the leaching kinetic is controlled by diffusion in the deionized water, while by the surface wash-off in the saline water. Finally, the mechanical tests confirmed that the cement composites prepared by MSWI bottom ash were durable in the saline water. The overall results demonstrate that the MSWI bottom ash can be a promising alternative as the cementitious component applied in cements or concretes for civil engineering. [ABSTRACT FROM AUTHOR]

Nowadays, in many countries the household waste is more and more incinerated, converting refuse in municipal solid waste incineration bottom ash (MSWI BA). A main concern related to the reuse of BA is linked to the leaching of contaminants, such as heavy metals and salts, to the surrounding environment. To limit this leaching, BA is applied as aggregate in the construction field, since the hydration products of cement are able to immobilize contaminants. Although not always suitable from an environmental point of view, a hydrothermal treatment (HT) can be applied to further increase the contaminants retention, as it stimulates the formation of tobermorite and it densifies the cement matrix. However, not many studies have investigated the influence of HT on cement based mortars and even less have been conducted concerning the optimization of the HT conditions. This study investigates the minimum HT duration for the maximization of mechanical performances and minimization of the environmental impact, for mortars including 25% BA, as sand replacement. The optimal autoclaving duration is found to be 6 h HT, which increases the compressive strength by 30% and it improves the retention of ions as Ba 2+ , Zn 2+ , and Cl − by 90%, 60% and 32%, respectively, compared to the standard cured sample. For longer treatment (8 h), the HT is not beneficial, since the leaching of contaminants increases due to the decomposition of reaction products as AFt and AFm. [ABSTRACT FROM AUTHOR]

This study explores the leaching of oxyanionic metalloid species (As, Mo, Se, V and Cr) from alkali activated slag-fly ash materials (AAM), dependent on various mixture parameters i.e., activator molarity, slag-fly ash precursor/binder compositions, liquid to binder ratio, curing time and strength. The analyses focusses on the leaching of potentially hazardous elements in a monolithic and granular material state. For monolithic state AAMs (concrete) overall leaching is within comparable range with traditional Portland cement and in both systems their leaching is far below the regulatory leaching limit values even though AAM strongly differs in mixture composition. For granular state AAMs (aggregate) the parameters, activator alkalinity and the slag-fly ash precursor/binder composition, significantly influence the leaching. The release of As and V strongly increases with a higher activator molarity as an effect of changes in the system alkalinity and related material pH. The release of As, Mo, Se and V strongly increase with a higher fly ash content within the precursor/binder composition. Overall, the leaching of aggregate state AAMs meets the Dutch leaching limits for open application of granular building materials, when the fly ash content within the binder composition ≤ ≈30 wt%. Typically, the pH dependent leaching data show oxyanionic metalloid species have a relatively high leaching potential, being less effectively bound as a result of the amorphous AAM microstructure. However, the leachable concentrations of a AAM system are within the bandwidth with that of blended (slag and or fly ash) Portland cement system. [ABSTRACT FROM AUTHOR]

The recovery of copper, nickel, zinc, silicon, iron, aluminum, tin and fluoride ions from fluoride leach liquors of non-ground printed circuit boards (PCBs) from mobile phones is described in detail. These PCBs were leached with HF + H 2 O 2 mixtures after previous treatment with 6 mol L −1 NaOH (removal of the solder mask). A combination of solvent extraction (SX) and precipitation techniques was used. 99.5 wt% zinc, copper and nickel, in this order, were extracted in one stage (Zn, Ni) or two stages (Cu) with di-2-ethylhexylphosphoric acid (D2EHPA) diluted in kerosene (25 °C, A/O = 1 v/v) after adjusting the pH of the leachate. They were easily stripped by aqueous H 2 SO 4 . Iron, aluminum and tin did not interfere because they were masked by fluoride ions. Iron and aluminum were precipitated together as Na 3 FeF 6  + Na 3 AlF 6 by careful addition of aqueous NaOH. Silicon, tin and fluoride ions were recovered together (Na 2 SiF 6  + Na 2 SnF 6  + NaF) by careful evaporation of the aqueous solution after SX of nickel. The tin salt was leached from this solid by absolute ethanol. High HF concentration (10 mol L −1 ) in the leachant affected SX of Cu(II) and precipitation of iron/aluminum flurocomplexes since some NaF partially precipitated at acidic pH. [ABSTRACT FROM AUTHOR]

Polybrominated diphenyl ethers (PBDEs) are commercial flame retardants that have been commonly used in vehicle interior to reduce fire-related hazards. Due to high temperatures and intense insolation that can be attained inside cars parked in the sun, additive PBDEs are prone to leach out and attach to in-vehicle dust, as well as to photo-debrominate. This study examines seasonal variations of concentrations of three common PBDE congeners (BDE-47, BDE-99 and BDE-209) in car dust in Israel. The overall concentrations of these BDEs ranged from 1 to 29 μg/g, and were higher in the summer than in the winter (average of 10.2 and 5.3 μg/g, respectively). Congener-specific concentrations showed distinct seasonal pattern, representing the interplay between leaching, evaporation and photodebromination. Photolysis of the three congeners, while adsorbed on glass filters and exposed to solar radiation, revealed first order kinetics with debromination rates on the order of 10 − 2 /min. Hence, seasonal variations of the meteorological conditions were found to affect the in-vehicle PBDE concentrations, and are therefore expected also to affect the exposure of passengers to PBDEs. [ABSTRACT FROM AUTHOR]

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Lead (Pb) is one of the most abundant metal soil pollutants. In this research, effects of nano-hydroxyapatite (NHAP) on remediation of Pb-contaminated soil were evaluated by the measure of extractable Pb using toxicity characteristic leaching procedure (TCLP) and soil enzyme activities. Results suggested NHAP significantly decreased the concentrations of extractable Pb, achieving the maximum decrement rate of 75.71%. Activity of urease decreased with increasing Pb concentrations. Moreover, activities of alkaline phosphatase, dehydrogenase, and catalase increased at the lower Pb levels and decreased at the higher Pb levels. NHAP had a positive effect on regulating soil enzymes. Thus, soil enzyme activities, especially dehydrogenase, could be used as biological indicators of Pb pollution and NHAP remediation. Moreover, NHAP could reduce the mobility and bioavailability of Pb, while increasing enzyme activities, thereby lowering the leaching risk and biotoxicity of Pb. [ABSTRACT FROM AUTHOR]

To comprehensively reuse the leaching residue obtained from lead-zinc tailings, an active silicon adsorbent (ASA) was prepared from leaching residue and studied as an adsorbent for copper(II), lead(II), zinc(II), and cadmium(II) in this paper. The ASA was prepared by roasting the leaching residue with either a Na2CO3/residue ratio of 0.6:1 at 700 °C for 1 h or a CaCO3/residue ratio of 0.8:1 at 800 °C for 1 h. Under these conditions, the available SiO2 content of the ASA was more than 20%. The adsorption behaviors of the metal ions onto the ASA were investigated and the Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models were used to analyze the adsorption isotherm. The result showed that the maximum adsorption capacities of copper(II), lead(II), cadmium(II), and zinc(II) calculated by the Langmuir model were 3.40, 2.83, 0.66, and 0.62 mmol g−1, respectively. The FT-IR spectra of the ASA and the mean free adsorption energies indicated that ion exchange was the mechanism of copper(II), lead(II), and cadmium(II) adsorption and that chemical reaction was the mechanism of zinc(II) adsorption. These results provide a method for reusing the leaching residue obtained from lead-zinc tailings and show that the ASA is an effective adsorbent for heavy metal pollution remediation. [ABSTRACT FROM AUTHOR]

The research was carried out in the years 2003-2013 in lysimeters filled with loamy sand. The leachate was tested in three variants: Z - no fertilization, S - 20 g·m-2 of N delivered annually in sewage sludge and C - 20 g·m-2 of N in the form of compost. The lysimeters were planted with Miscanthus giganteus, which is an energy plant with a high demand for water and nutrients. The amount of leaching of mineral nitrogen forms was determined on the basis of measured volumes of leachates from the soil and volumes of ammonium nitrogen (N-NH4) and nitrate nitrogen (N-NO3) contained in them. The research results showed a significant increase in the average content of mineral nitrogen forms in the effluents from the fertilized soil (S - 6.8 mgg·mdm-3 of N-NO3 and 0.3 mgg·mdm-3 of N-NH4, C - 7.8 mgg·mdm-3 of N-NO³ and 0.4 mgg·mdm-3 of N-NH4), compared to their concentrations in the leachates from non-fertilized soil (Z - 2.1 mgg·mdm-3 of N-NO3 and 0.2 mgg·mdm-3 of N-NH4). The content of mineral forms of nitrogen, in particular N-NO3, were similar in both fertilization variants. The lowest concentrations of mineral nitrogen in the leachates occurred in the third and fourth year after planting Miscanthus giganteus, when it entered the period of the highest yield. In the fifth year, due to a cold, snowless winter, there was a weakened growth of plants, which resulted in an increase in the concentration of mineral nitrogen in the leachates from the fertilized soil. It follows that in addition to the intensity of precipitation, the collection of this component by plants primarily influences nitrogen leaching from the soil. The general amount of mineral nitrogen leached from the soil was not large and amounted Z - 2.5 kg·m-2, S - 6.7 kg·m-2, C - 6.4 kg·m-2. This testifies to the intense collection of this form of nitrogen by Miscanthus giganteus. [ABSTRACT FROM AUTHOR]

X-ray diffraction analysis revealed that pentlandite and chalcopyrite were the prominent mineral phases in a South African sulfidic nickel ore concentrate that hosted nickel and copper. Cobalt was found to be closely associated with the nickel-bearing pentlandite phase of the ore sample. Microbial batch leaching experiments designed according to a central composite design model were run for 15 days in a shaking incubator (150 rpm) at a constant temperature (30°C) with variations in experimental parameters like ore pulp density, particle size, bacterial inoculum, pH of the culture medium, and residence time. Quadratic mathematical models were developed to predict the rate of metal extractions. The suitability of the model of the microbial leaching process was confirmed from normal probability curves. An analysis of variance indicated that the residence time, pulp density of the ore, and particle size were the most significant factors. Bacterial inoculum size hardly showed any effect on the total metal extractions. Maximum nickel (82%), cobalt (76%) and copper (25.6%) extractions were achieved under optimum conditions, operated for 15 days at pulp density of 2% and particle size of −75 µm at pH 1.5. [ABSTRACT FROM AUTHOR]

A 3-years field test and laboratory leaching test have been conducted to assess the environmental impact of land application of sewage sludge compost in conjunction with wheat and rice crops. Considering the complexity and variability of field conditions, we compared the result of laboratory test with the field test to understand the accuracy and uncertainty associated with using the laboratory test to evaluate the field scenario. The laboratory test with cycling of compost additions and water percolation was a high time-efficient and feasible method to simulate the annually repeated additions of compost in the field application scenario. The results of laboratory test were congruent to the 3-years field test regarding the leaching characteristics and geochemical speciation of toxic trace elements. Both the laboratory and the field test showed that repeated additions of compost to soils can increase leaching concentrations of toxic trace elements at neutral to alkaline pH. Increased toxic trace elements leaching was caused by the increase of organic matter from compost application and organic matter dissolution at alkaline pH. Uncertainties of the laboratory test mainly included the negligibility of crop growth and the strongly reducing condition formed with continuous percolation procedure. [ABSTRACT FROM AUTHOR]

Pre-treatment process carried out on raw municipal solid waste incineration (MSWI) fly ash (FA) sample that did not comply initially with the USEPA method 1311 toxicity characteristic leaching procedure (TCLP) regulatory limits of 2011 reduced its chloride and heavy metal content appreciably, thereby making it compliant with the aforementioned regulatory requirement. More than 98% of each heavy metal was successfully removed. The process was excellent in removing cadmium (Cd) (99.99%) and very good at removing the rest. About 99.96% of Cu was eliminated, 99.96% of cobalt (Co), 99.95% of Zn, 98.61% of Cr, and 98.12% of nickel (Ni). Also, the leachate resulting from these pre-treatment steps met the China (GB 16889-2008) and USEPA method 1311 regulatory standards for safe discharge. The density and compressive strength of all the samples prepared increased as the FA content decreased. The compressive strength of all the samples passed the 1989 USEPA-recommended value of 0.34 MPa (50 psi), thereby making them suitable for industrial application. The sample that attained the highest compressive strength (2.08 MPa) after 28 days of curing incorporated 55% fly ash (FACS55), while the one with the least compressive strength (0.65 MPa) after the same period was made from only fly ash (FACS100). Moreover, the concentration of heavy metals in all the samples generally decreased with the FA content. Chromium was not detected in all the samples, thereby making this an excellent method for its immobilization. From the leachability test results, all the samples prepared met the USEPA method 1311 TCLP regulatory limits. [ABSTRACT FROM AUTHOR]

Heavy metal contamination of surface and ground waters from anthropogenic sources presents a significant risk to human health and the environment. Leaching of metals such as lead, cadmium, and zinc from historic mining residuals has led to extensive groundwater contamination, for example, the elevated concentrations found at the Oronogo-Duenweg Superfund site in Joplin, Missouri, United States. Excessive wastewater buildup and storage at historic mines have also caused the release of metal toxicants into river systems, as was the case in the catastrophic 2015 Gold King mine spill into the Animas River in Western Colorado. Prevention of metals contamination and the reclamation of contaminated water for human and agricultural use are compelling reasons to improve heavy metal remediation technologies. Permeable reactive concrete (PRC) is a novel, cementitious material that demonstrates substantial removal capacity for heavy metals from aqueous solutions at the bench scale. This study investigated breakthrough testing of PRC using a synthetic groundwater solution of lead, cadmium, and zinc at concentrations similar to reported values for the Oronogo-Duenweg site of ∼0.4 mg/L for lead and cadmium and 45 mg/L for zinc. Breakthrough testing elucidates removal mechanisms and reaction rates, but has never before been performed on PRC. Removal mechanisms documented in this study were precipitation of the hydroxide metals, complexation, and sorption of metals into the hydrated cement paste or metal precipitates. Demonstrated removal became more permanent over time, with total testing time around 260 days without breakthrough. Column breakthrough testing timeframes exceeded initial bench scale isotherm estimates by a factor of 20. Cost estimates for PRCs are ∼1/6th to 1/12th the cost of comparable technologies for similar site applications. PRC has been shown in this study to perform equal to, or greater than, comparable technologies and could significantly reduce remediation costs for other contamination sites. [ABSTRACT FROM AUTHOR]

Over several decades, Nigeria has still not been let off the hook for the leeching effects of environmental pollution, particularly that caused by ever-growing mountains of hazardous waste. From the harmful gases put into the atmosphere or the toxic waste released into water bodies and to the waste produced from our homes, the unchecked creation of hazardous waste continues to pose a threat not just to the health and lives of both present and future generations but also to economic growth and development as well as the enjoyment of basic human rights. This article aims at examining the major issues surrounding the unbridled production of hazardous waste in Nigeria as well as some practical possibilities within the United Nations system to put an end to the menace. In so doing, a doctrinal method of legal research is employed by conducting a qualitative content analysis of primary and secondary sources of materials. This article finds that in the absence of practical and innovative actions to stem the relentless growth in waste, the future of Nigeria's economic growth is hazy. It is concluded that if the country can take a proactive dive into the United Nations system by shifting the focus from ‘waste management’ to ‘resource management’ through legally binding instruments, there may soon be a pathway for Nigeria to create one of the most sustainable economies in the world. This article recommends a substantial step-change involving both national and local political players as well as the general public to implement more practical solutions to hazardous waste in Nigeria. [ABSTRACT FROM AUTHOR]

Nitrogen is one of the most important nutrients for plant growth and hence heavily applied in agricultural systems via fertilization. Nitrification, that is, the conversion of ammonium via nitrite to nitrate by soil microorganisms, however, leads to nitrate leaching and gaseous nitrous oxide production and as such to an up to 50% loss of nitrogen availability for the plant. Nitrate leaching also results in eutrophication of groundwater, drinking water and recreational waters, toxic algal blooms and biodiversity loss, while nitrous oxide is a greenhouse gas with a global warming potential 300× greater than carbon dioxide. Logically, inhibition of nitrification is an important strategy used in agriculture to reduce nitrogen losses, and contributes to a more environmental-friendly practice. However, recently identified and crucial players in nitrification, that is, ammonia-oxidizing archaea and comammox bacteria, seem to be under-investigated in this respect. In this review, we give an update on the different pathways in ammonia oxidation, the relevance for agriculture and the interaction with nitrification inhibitors. As such, we hope to pinpoint possible strategies to optimize the efficiency of nitrification inhibition. [ABSTRACT FROM AUTHOR]

With increasing amounts of woody biomass being combusted for energy purposes worldwide, more wood ash is being generated and needs management. As an alternative to landfilling, residues may be utilised for liming and fertilising purposes on forest soils. Comprehensive evaluations of long-term leaching from these residues are needed in order to assess potential environmental impacts associated with their utilisation. Two Danish wood ash samples, one fly ash and one mixed ash (a combination of fly ash and bottom ash), were evaluated in long-term percolation column tests (up to L/S ∼2000 L/kg), in order to quantify the release of major, minor and trace metal(loid)s. While columns of three different lengths were used, the leaching of individual elements could be described as a function of the L/S ratio – irrespective of the column length. At L/S 1000 L/kg, the cumulative releases of K, S, Na, Ca and Rb were at 40–100% of their respective solid contents, followed by Ba, Cr, Sb, Sr and V at 15–40% and Al, Mg, Zn, Cd, Co, Fe, Pb, Tl, Mn and P at < 5%. Speciation calculations indicated that (i) the observed concentrations of Ca, Mg, Al, Ba, Si and sulphate from both ash types could be described through the dissolution/precipitation of a limited set of minerals and that (ii) leaching of silicates should be included in long-term assessment of alkalinity release from wood ashes. Non-equilibrium conditions were indicated by flow interruptions. However, the presence of non-equilibrium did not have significant effect on the calculated cumulative releases at high L/S ratios. Based on the assessment of cumulative releases at L/S 10 L/kg and L/S 1000 L/kg it is concluded that low L/S-based data may not provide sufficient background for prediction of long-term release from wood ash, in particular for Ba, Cr, Sb and V, and less critically also for As, Cd, Cu, Mo and Ni. [ABSTRACT FROM AUTHOR]

Leaching of macronutrients such as nitrogen, phosphorus and potassium from soils is of particular interest in the Baltic Sea region because of its adverse effects on water quality. The objective of this study was to evaluate macronutrient leaching in a juvenile hybrid aspen (Populus tremula L. × P. tremuloides Michx.) plantation cultivated in an agroforestry system and fertilized with biogas production residues, wastewater sludge and wood ash in hemi-boreal climate conditions. Analysis of macronutrient concentrations in the soil solution showed that annual macronutrient leaching decreased over time after the establishment of the plantation and application of fertilizers. Moreover, macronutrient leaching was affected not only by meteorological conditions, but also by the type of fertilizer used. During the five years after establishment of the plantation, nitrate-nitrogen leaching decreased up to 99.6%, phosphate-phosphorus leaching decreased up to 97.1%, but potassium ions leaching decreased up to 76.5%. Nevertheless, juvenile hybrid aspen plantations cultivated in an agroforestry system remain an important part in mitigation of leaching of macronutrients from agricultural lands in the Baltic Sea region. [ABSTRACT FROM AUTHOR]

Estimating the movement of dissolved contaminants in heterogeneous aquifers is very important for the monitoring design, risk assessment, and remediation of contaminated aquifers. This work explored the influence of source size, monitoring distance, and aquifer heterogeneity on the accuracy of contaminant mass discharge (CMD) estimation using leaching surface approach as well as on the plume spread uncertainty in a 2-D heterogeneous aquifer. The interaction among source size, monitoring distance, and aquifer heterogeneity regarding the accuracy of CMD estimation and the plume spread uncertainty at downstream of the contaminated aquifer was extensively investigated. The transient leaking of a contaminated aquifer in a saturated heterogeneous aquifer under steady-state flow conditions was simulated. The effect of aquifer heterogeneity on the CMD uncertainty was evaluated through the expected values and variance. The results showed that the CMD estimation error varied from underestimation in the mildly heterogeneous aquifer, over accurate estimation in the medium heterogeneous aquifer to overestimation in the highly heterogeneous aquifer. Additionally, the results illustrated that the mean and variance of the transverse spatial extent of the peak concentrations for the plume at the control plane were very sensitive to the aquifer heterogeneity and detectable concentrations of contaminants. [ABSTRACT FROM AUTHOR]

The US Pacific Northwest is one of the most productive potato regions in the world. However, due to the high inputs, nitrate contamination of groundwater is frequently documented, and maximizing crop productivity while minimizing nitrate leaching is still challenging. The goal of this study was to assess how irrigation level, soil type, and weather condition during various phenological phases would affect tuber yield and the associated nitrate leaching and profit margin. The Cropping System Model (CSM)-SUBSTOR-Potato was used to simulate the response variables for various scenarios that comprised two soil types, five irrigation levels, five phenological phases, five weather conditions, and 75 years of historical weather data for 3 locations in this region. The simulation results showed that nitrate leaching was higher with a higher amount of irrigation and for a lighter soil. Tuber yield and profit margins were lowest for a lighter soil and highest for 300 mm of irrigation for an extremely-drained soil and 400 mm of irrigation for a well-drained soil. The increase in profit margins with an increase in total irrigation up to 400 mm was highest for a well-drained soil, whereas the decrease in profit margins with an increase in irrigation beyond a total amount of 300 mm was larger for an extremely-drained soil. For the different types of weather scenarios that were studied, only severe hot weather had an impact on tuber yield and profit margins. The reduction was highest at tuber bulking and significant when hot weather continued from sprout development through tuber bulking or from plant establishment through tuber maturation. However, any change in weather condition from the long-term average for any growth phase did not affect leaching. These findings might be helpful to potato growers in this region to protect their potatoes from adverse weather conditions through appropriate mitigation strategies. [ABSTRACT FROM AUTHOR]

Indications of the Early Pleistocene paleopedogenesis were analyzed in multilevel sections of pedosediments at Early Acheulian sites within the Lori Plateau in Northern Armenia, with the purpose of reconstructing the paleoclimatic conditions during the initial stage of early human occupation of this region. At the study sites, lithic tools typical of the Acheulian technocomplex dating back to 1.4–1.9 Ma were found. The sections of studied pedosediments were shown to contain material from former paleosols that developed higher up the slope, then were eroded and transported by colluvial processes (presumably during catastrophic events) and finally redeposided in an inverted order at the foot of the slope. Three evolutionary stages of Lower Pleistocene paleosols were identified, which allow for paleoclimatic reconstruction of the initial stages of early human occupation of this region. In the earliest chronointerval, ∼1.9–1.77 Ma, Vertic Cambisols and Colluvic Regosols Humic developed in the region, in savanna-like landscapes under (sub)tropical climatic conditions. Towards the end of this period, ∼1.77 Ma, the climatic conditions remained sub(tropical), but became more humid, with the development of Stagnic Cambisols and Andosols with an abundance of redoximorphic features. During the latest period studied, between 1.77 and 1.4–1.5 Ma, the development of Luvisols indicates a stronger leaching environment under a permanently humid climate with significant cooling. Early hominin communities had to adapt to the cooler environment to be able to continue their uninterrupted development into the Middle Pleistocene. [ABSTRACT FROM AUTHOR]

The virulence properties of Candida spp. presents in landfill leachate still unknown until today and they constitutes a serious source of potential danger for humans. We investigate the antifungal susceptibility, production of hydrolytic enzymes and biofilm formation on polystyrene as well as glass in Candida spp. strains isolated from a landfill leachate treatment station in Borj Chakir (Tunisia). 37 yeast strains were isolated belonging to the following species: C. robusta , C . lusitaniae , C . tropicalis , C . krusei . Most isolated yeast strains were resistant to Amphotericin B, produced several hydrolytic enzymes (67.56% produced phospholipase, 86.04% protease, 64.86% esterase) and most of them are able to degrade hemoglobin. All assayed Candida strains have been able to form biofilm on polystyrene depending on the species and strain of Candida . Landfills receiving clinical waste are a potential source of Candida ssp. strains with several virulence properties which allow them to survive in different aquatic biotopes. [ABSTRACT FROM AUTHOR]

To meet the current challenges of waste water, an efficient, environment friendly and economical treatment process is always desirable for the degradation of toxic organic compounds. Herein, we reported a stable and active bimetallic CuOx@Co-LDH catalyst for the degradation of phenol using persulfate (PS) under mild conditions. The system of PS/CuOx@Co-LDH completely degraded 0.1 mM of phenol in less than 40 min while at the same time, all the other tested catalysts including catalyst precursors remained sluggish. In view of the practical application, CuOx@Co-LDH/PS system demonstrated consistent performance over a broad pH range (pH 5.0–12.0), during which minimum leaching could be detected. Moreover, good resistance to various inorganic anions was demonstrated in CuOx@Co-LDH/PS system. The consistent performance of CuOx@Co-LDH/PS system may originate from the constant buffer pH of catalyst (9.5 ± 0.8), minimum leaching and the generation of diverse free radicals ( SO 4 − , OH or − O 2 ) under different pH conditions. Additionally, LDH structure offered strong synergetic interactions among active components which might also help in minimum leaching and good reactivity of CuOx@Co-LDH catalyst. The results of radical scavengers, EPR and XPS studies collectively proved the mechanism of diverse free radicals, which was accounted to the redox cyclic reactions of active sites (Cu (III) –Cu (II) –Cu (III) and Co (III) –Co (II) –Co (III) ) during degradation of phenol. [ABSTRACT FROM AUTHOR]

A series of laboratory experiments were conducted, in which waste furniture polyurethane foam samples containing tris (1-chloro-2-propyl) phosphate (TCIPP) were contacted with a range of leaching fluids, formulated to simulate the composition of landfill leachate. Leaching was examined under a number of different scenarios, such as: dissolved humic matter concentration, pH, and temperature, as well as the effect of agitation, and waste:leaching fluid contact duration. In addition to single batch (no replenishment of leaching fluid), serial batch (draining of leachate and replenishment with fresh leaching fluid at various time intervals) experiments were conducted. Leaching of TCIPP from PUF appears to be a first order process. Concentrations of TCIPP in leachate generated by the experiments in this study ranged from 13 mg L −1 to 130 mg L −1 . In serial batch leaching experiments, >95% of TCIPP was depleted from PUF after 168 h total contact with leaching fluid. Our experiments indicate leaching is potentially a very significant pathway of TCIPP emissions to the environment. [ABSTRACT FROM AUTHOR]

Quantitatively ascertaining and analyzing long-term responses of crop yield and nitrate leaching on varying irrigation and fertilization treatments are focal points for guaranteeing crop yield and reducing nitrogen loss. The calibrated agricultural-hydrological RZWQM2 model was used to explore the long-term (2003–2013) transport processes of water and nitrogen and the nitrate leaching amount into groundwater in summer maize and winter wheat rotation field in typical intensive plant area in the North China Plain, Daxing district of Beijing. Simulation results showed that application rates of irrigation and nitrogen fertilizer have couple effects on crop yields and nitrogen leaching of root zone. When both the irrigation and fertilizer for summer maize and winter wheat were 400 mm and 400 kg N ha − 1 , respectively, nitrate leaching into groundwater accounted for 47.9% of application amount of nitrogen fertilizer. When application amount of irrigation is 200 mm and fertilization is 200 kg N ha − 1 , NUPE (nitrogen uptake efficiency), NUE (nitrogen use efficiency), NPFP (nitrogen partial factor productivity), and W pi (irrigation water productive efficiency) were in general higher than that under other irrigation and fertilization condition (irrigation from 104–400 mm, fertilizer 104–400 kg N ha − 1 ). Irrigation bigger than 200 mm could shorten the response time of nitrate leaching in deeper soil layer in different irrigation treatment. [ABSTRACT FROM AUTHOR]

Large volumes of disposed mine tailings abound in several regions of South Africa, as a consequence of unregulated, unsustainable long years of mining activities. Tailings dumps occupy a large volume of valuable land, and present a potential risk for aquatic systems, through leaching of potentially toxic chemical species. This paper reports on the evaluation of the geochemical processes controlling the mobility of potentially toxic chemical species within the tailings profile, and their potential risk with regard to surface and groundwater systems. Combination of X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) techniques, show that the tailing profiles are uniform, weakly altered, and vary slightly with depth in both physical and geochemical properties, as well as mineralogical composition. Mineralogical analysis showed the following order of abundance: quartz > epidote > chlorite > muscovite > calcite > hematite within the tailings profiles. The neutralization of the dominant alumino-silicate minerals and the absence of sulfidic minerals, have produced medium alkaline pH conditions (7.97-8.37) at all depths and low concentrations of dissolved Cu (20.21-47.9 µg/L), Zn (0.88-1.80 µg/L), Pb (0.27-0.34 µg/L), and SO42- (15.71-55.94 mg/L) in the tailings profile leachates. The relative percentage leach for the potentially toxic chemical species was low in the aqueous phase (Ni 0.081%, Cu 0.006%, and Zn 0.05%). This indicates that the transport load of potentially toxic chemical species from tailings to the aqueous phase is very low. The precipitation of secondary hematite has an important known ability to trap and attenuate the mobility of potentially toxic chemical species (Cu, Zn, and Pb) by adsorption on the surface area. Geochemical modelling MINTEQA2 showed that the tailings leachates were below saturation regarding oxyhydroxide minerals, but oversaturated with Cu bearing mineral (i.e., cuprite). Most of the potentially toxic chemical species occur as free ions in the tailings leachates. The precipitation of secondary hematite and cuprite, and geochemical condition such as pH of the tailings were the main solubility and mobility controls for the potentially toxic chemical species, and their potential transfer from tailings to the aqueous phase. [ABSTRACT FROM AUTHOR]

Cr 2 O 3 containing refractories are used as the linings of various waste melting furnaces. Formation of hexavalent chromium (Cr(VI)) has been a major concern despite its admirable corrosion resistance properties. Al 2 O 3 -CaO-Cr 2 O 3 refractory castables (0, 4%, 8%, and 12 wt% Cr 2 O 3 ) were fabricated in reducing condition to inhibit Cr(VI) formation while subsequent corrosion tests using waste slag was performed in air atmosphere to simulate the operating conditions. The corrosion mechanism between Cr 2 O 3 -containing corundum castables and synthetic waste slag were investigated by XRD and SEM-EDS, whereas concurrent formations of Cr(VI) were assessed effectively by leaching tests. Corrosion of castables (0 wt% Cr 2 O 3 ) occurs via dissolution of Al 2 O 3 and CA 6 phases, and formation of Ca 2 (Al,Mg)(Al,Si) 2 O 7 and (Ca , Na)(Al,Si) 2 Si 2 O 8 , which were significantly restricted by the formation of Al 2 O 3 -Cr 2 O 3 (III) solid solution (4%, 8%, and 12 wt% Cr 2 O 3 ). Most of the specimens exhibited less than 5 mg/L (EPA limit) of Cr(VI). Only specimen M3 (12 wt% Cr 2 O 3 ) from slag-refractory interface (stage C) leached out 5.41 mg/L of Cr(VI) which is above the EPA limit. Specimen M2 (8 wt% Cr 2 O 3 ) exhibits optimum properties in terms of corrosion and Cr(VI) formation. [ABSTRACT FROM AUTHOR]

Bioprocessing for the recovery of metal from divergent resources using the microbial strategy has emerged as a green technology in metallurgical operations. The limitations to maintain the ideal condition for bacterial growth with slow kinetics, however, have been considered as major obstacles to bioprocessing being implemented more widely. This can be overcome by integrating the microbes with a chemical processing route. The available reports on recent developments in hybrid bio-chemical processing of both primary and secondary resources have presented promising results, exhibiting the potential for use in large-scale metallurgy. In this context, reviewing the factors of the hybrid process would benefit from knowledge acquired in fundamental studies. The present review focuses on bio-chemical process integration using eco-friendly design tools for treating the difficult to extract resources and complex spent materials as well. Furthermore, the potential of hybrid technology has been evaluated by establishing an economic model as a case study which encompasses features of economic development, environmental consideration and societal matters to achieve process sustainability. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]