leaching
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Ethanol and propan-2-ol were used to verify the efficiency of removing persistent organic pollutants from real soil contaminated with PCB (395 mg kg-1) or with oil and tar substances (57,5 g kg-1). In batch extraction 65-90 % contaminants were removed with both solvents. An influence of water content in solvent was examined in a series of experiments. The presence of water in the solvents decreases the extraction efficiency more for oil and tar substances than for PCB. 96 % of PCB and 75 % of oil and tar substances were removed from soil by washing in a column, using five pore volumes of propan-2-ol. Distillation and membrane separation were the methods considered for solvent recovery.
Currently standardised leaching tests require grain size reduction, which for large fragments of slags could overestimate the leaching results. To assess the effect of the fine-grained fraction generated by sample crushing, a set of leaching experiments was performed on copper smelting slag from the Zambian Copperbelt: (i) EN 12457-2 batch tests (standardised grain size <4 mm; modified procedure with grain size of 4-0.5 mm simulating exposure of larger fragments on the dumps) and (ii) CEN/TS 14997 pH-static tests (standardised grain size <1 mm simulating the possible wind dispersion scenario near the slag crushing facilities or disposal of fine-grained granulated slag; additional grain sizes <5 mm, 5-0.5 mm and 5-0.5 mm after ultrasonic cleaning). A higher proportion of the fine-grained fraction generally led to greater leaching of Cu, Co and Zn. The metal levels in the leachates under circum-neutral conditions were all below the EU limits for non-hazardous waste. However, at pH 4, the presence of fine dust particles dramatically increased the concentrations of metals in the slag leachates. The greater leachability of Cu and Co from slag particles under acidic conditions suggests a risk of their mobilisation in acidic soils in the Copperbelt area.
- MeSH
- měď chemie toxicita MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
BACKGROUND: Physically based tier-II models may serve as possible alternatives to expensive field and laboratory leaching experiments required for pesticide approval and registration. The objective of this study was to predict pesticide fate and transport at five different sites in Hawaii using data from an earlier field leaching experiment and a one-dimensional tier-II model. As the predicted concentration profiles of pesticides did not provide close agreement with data, inverse modeling was used to obtain adequate reactive transport parameters. The estimated transport parameters of pesticides were also utilized in a tier-I model, which is currently used by the state authorities to evaluate the relative leaching potential. RESULTS: Water flow in soil profiles was simulated by the tier-II model with acceptable accuracy at all experimental sites. The observed concentration profiles and center of mass depths predicted by the tier-II simulations based on optimized transport parameters provided better agreements than did the non-optimized parameters. With optimized parameters, the tier-I model also delivered results consistent with observed pesticide center of mass depths. CONCLUSION: Tier-II numerical modeling helped to identify relevant transport processes in field leaching of pesticides. The process-based modeling of water flow and pesticide transport, coupled with the inverse procedure, can contribute significantly to the evaluation of chemical leaching in Hawaii soils.
- MeSH
- chemické látky znečišťující vodu analýza chemie MeSH
- chemické modely MeSH
- látky znečišťující půdu analýza chemie MeSH
- monitorování životního prostředí metody MeSH
- pesticidy analýza chemie MeSH
- počítačová simulace MeSH
- pohyb vody MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Havajské ostrovy MeSH
Environments in the vicinity of the lead (Pb) smelters are contaminated by emissions containing high concentrations of antimony (Sb) and arsenic (As). Air-pollution-control (APC) residues from bag-type filters from a secondary Pb smelter were subjected to leaching experiments to elucidate the controlling mechanisms of Sb and As release. Kinetic batch leaching tests at a liquid-to-solid (L/S) ratio of 10 L kg(- 1) within the time frame of 720 hours and batch leaching at various L/S ratios (ranging from 1 to 1000 L kg(-1)) were performed. In contrast to other inorganic contaminants (Pb, Cd, Zn), less than 1% of the total Sb and As content was leached from the residues. At a L/S ratio of 10, the As and Sb concentrations in the leachates exceeded the EU limit values for non-hazardous waste (0.2 and 0.07 mg L(-1) ). According to PHREEQC-2 calculations, the concentrations of As and Sb are controlled by the precipitation of complex arsenates and antimonates mainly at low L/S ratios. The washing and related chemical/mineralogical transformation of APC residues was suggested as a technological pre-treatment process before their re-smelting in a blast furnace. The Ferrox-like processing of the resulting contaminated process water/leachate was simulated using the PHREEQC-2 code. Significant reduction was obtained in the concentration of some key contaminants (As, Cu, Pb, Zn) related to sorption on newly formed hydrous ferric oxides, whereas Sb and Cd exhibited only limited attenuation.
- MeSH
- antimon analýza izolace a purifikace MeSH
- arsen analýza izolace a purifikace MeSH
- hutnictví MeSH
- látky znečišťující vzduch analýza izolace a purifikace MeSH
- olovo analýza izolace a purifikace MeSH
- průmyslový odpad prevence a kontrola MeSH
- spalování odpadů MeSH
- těžké kovy analýza izolace a purifikace MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Low-molecular-mass organic acids (LMMOA) are of key importance for mobilisation and fate of metals in soil, by functioning as ligands that increase the amount of dissolved metal in solution or by dissociation of metal binding minerals. Column leaching experiments were performed on soil polluted with As and Pb, in order to determine the specificity of LMMOA related release for individual elements, at varying organic acid concentrations. Acetic, citric and oxalic acids were applied in 12h leaching experiments over a concentration range (0.5-25 mM) to soil samples that represent organic and mineral horizons. The leaching of As followed the order: oxalic>citric>acetic acid in both soils. Arsenic leaching was attributed primarily to ligand-enhanced dissolution of mineral oxides followed by As released into solution, as shown by significant correlation between oxalic and citric acids and content of Al and Fe in leaching solutions. Results suggest that subsurface mineral soil layers are more vulnerable to As toxicity. Leaching of Pb from both soils followed the order: citric>oxalic>acetic acid. Mineral soil samples were shown to be more susceptible to leaching of Pb than samples characterised by a high content of organic matter. The leaching efficiency of citric acid was attributed to formation of stable complexes with Pb ions, which other acids are not capable of. Results obtained in the study are evidence that the extent of As and Pb leaching in contaminated surface and subsurface soil depends significantly on the types of carboxylic acid involved. The implications of the type of acid and the specific element that can be mobilised become increasingly significant where LMMOA concentrations are highest, such as in rhizosphere soil.
- MeSH
- arsen chemie MeSH
- kyselina citronová chemie MeSH
- kyselina octová chemie MeSH
- kyselina oxalová chemie MeSH
- kyseliny acyklické chemie MeSH
- látky znečišťující půdu chemie MeSH
- minerály chemie MeSH
- olovo chemie MeSH
- půda chemie MeSH
- rhizosféra MeSH
- roztoky MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika MeSH
The leaching behaviors of primary copper (Cu) slags originating from Ausmelt, reverbatory, and converter furnaces operating under a single technological process were compared to a residual slag tailing obtained by slag re-processing via flotation and metal recovery. The EN 12457-2 leaching test, used for assessment of the hazardous properties, was followed by the CEN/TS 14997 pH-static leaching test (pH range 3-12). Both leaching experiments were coupled with a mineralogical investigation of the primary and secondary phases as well as geochemical modeling. Metals (Cd, Cu, Pb, Zn) exhibit the highest leaching at low pH. Under acidic conditions (pH 3-6), Ausmelt slag and slag tailing exhibited higher metal leaching compared to other slag types. Very low leaching of metals (far below EU limits for non-hazardous waste) was observed at natural pH (7.9-9.0) for all the studied slag samples. In contrast, relatively high leaching of As was observed over the entire pH range, especially for Ausmelt slag (exceeding the EU limit for hazardous waste by 1.7×). However, geochemical modeling and scanning electron microscopy indicated that formation of stable Ca-Cu-Pb arsenates and the binding of As to newly formed Fe (oxyhydr)oxides play an important role in efficient As immobilization at the slag-water interface. In contrast, no controls were predicted for Sb, whose leaching was almost pH-independent. Nevertheless Sb leached concentrations at natural pH were below EU limit for hazardous waste. Re-processing of primary Cu slags for metal recovery, and subsequent co-disposal of the resulting slag tailing with dolomite-rich mine tailing and local laterite is suitable for stabilizing the remaining contaminants (except Sb) and limiting their leaching into the environment.
- MeSH
- arseničnany MeSH
- Evropská unie MeSH
- hornictví MeSH
- hutnictví metody MeSH
- kovy MeSH
- látky znečišťující životní prostředí analýza MeSH
- měď * MeSH
- nebezpečný odpad zákonodárství a právo MeSH
- odpadní produkty analýza MeSH
- životní prostředí * MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Namibie MeSH
Nitrogen leaching owing to elevated acid deposition remains the main ecosystem threat worldwide. We aimed to contribute to the understanding of the highly variable nitrate losses observed in Europe after acid deposition retreat. Our study proceeded in adjacent beech and spruce forests undergoing acidification recovery and differing in nitrate leaching. We reconstructed soil microbial functional characteristics connected with nitrogen and carbon cycling based on community composition. Our results showed that in the more acidic spruce soil with high carbon content, where Acidobacteria and Actinobacteria were abundant (Proteo:Acido = 1.3), the potential for nitrate reduction and loss via denitrification was high (denitrification: dissimilative nitrogen reduction to ammonium (DNRA) = 3). In the less acidic beech stand with low carbon content, but high nitrogen availability, Proteobacteria were more abundant (Proteo:Acido = 1.6). Proportionally less nitrate could be denitrified there (denitrification:DNRA = 1), possibly increasing its availability. Among 10 potential keystone species, microbes capable of DNRA were identified in the beech soil while instead denitrifiers dominated in the spruce soil. In spite of the former acid deposition impact, distinct microbial functional guilds developed under different vegetational dominance, resulting in different N immobilization potentials, possibly influencing the ecosystem's nitrogen retention ability.
- MeSH
- Bacteria klasifikace metabolismus MeSH
- buk (rod) růst a vývoj MeSH
- denitrifikace * MeSH
- dusičnany analýza MeSH
- koncentrace vodíkových iontů MeSH
- mikrobiota * MeSH
- půda chemie MeSH
- půdní mikrobiologie * MeSH
- smrk růst a vývoj MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Evropa MeSH
