EPA Toxicity Characteristic Leaching Procedure Research Articles

Investigation of Bagasse Ash as an Alternative Raw Material in Clinker Production

The feasibility of using sugarcane bagasse ash waste (BA) as an alternative raw material for clinker production was investigated. The effect of the BA on the mineral and mechanical properties of clinker at various sintering temperatures, as well as its environmental impact, was examined. The addition of BA increased the formation of C2S at 1,250°C but adversely affected the formation of C3S at 1,450°C, which caused compressive strength loss. However, the addition of BA up to 1.0 percent by weight at 1,450°C meets the ASTM standard that requires a minimum compressive strength of at least 19.0 MPa for seven days of curing time. In The EPA toxicity characteristic leaching procedure (TCLP) revealed that concentrations of As, Cr, Pb, Fe, and Mn in the raw BA exceeded applicable limits These elements were not detected or were negligible after the sintering process. Results indicate that sugarcane BA waste can be used as an alternative raw material in clinker production as a means of recycling this waste product, thus contributing to sustainable waste management.

In situ stabilization of the adsorbed Co2+ and Ni2+ in rice straw biochar based on LDH and its reutilization in the activation of peroxymonosulfate

The stabilization of heavy metals adsorbed in the spent biochar remains a challenge, and the risk of secondary pollution under environmental changes will rise under inadequate post-treatment. Moreover, the safe and sufficient re-utilization of the spent biochar with heavy metals loaded have attracted extensive attention. In this research, the performance and mechanism of rice straw biochar (RSBC) pyrolyzed at different temperature for nickel and cobalt adsorption were investigated, and the stabilization of the adsorbed heavy metals was achieved via a simple two-step strategy: the adsorption of metal ions and the hydrothermal process to form the stable layered double hydroxides (LDH) on biochar, with a leaching rate below 0.005% evaluated by EPA toxicity characteristic leaching procedure (TCLP). Meanwhile, the stabilized RSBC-LDH can be reused as an excellent catalyst in the activation of peroxymonosulfate (PMS) to degrade organic pollutants efficiently. This work eliminated the risk of heavy metal desorption from the spent biochar, and enabled a new strategy for the optimized utilization of biochar in environmental remediation.

Leaching behavior of trace elements from fly ashes of five Chinese coal power plants

The leaching behavior of trace elements in five fly ashes from five Chinese coal-fired power plants were obtained by conducting the new US EPA leaching test methods (LEAF) and the conventional EPA Toxicity Characteristic Leaching Procedure (TCLP) test method. These were done under a range of pH values and liquid to solid ratios. Despite different elemental and mineralogical compositions of the ashes and different ranks of the respective feed coals, the majority of elements show similar liquid/solid partitioning (LSP) curve trends among the different ash samples in the pH-dependent leaching tests. This indicates that most elements are sensitive to changes in pH. Different LSP curves exist for Cr from pH-dependent tests, probably due to different valence states of this element in the unleached fly ashes. Although most elements show similar LSP curves for different fly ash samples from the liquid/solid (L/S) dependent tests, variation exists for LSP curves of some individual elements among different ash samples. Caution should be taken when generating general L/S dependent leaching characteristics for individual elements. The leachate concentrations of the highly soluble elements such as B and Se, as well as oxyanions under alkaline conditions, are dependent on their initial concentrations in the fly ashes. The conventional EPA method TCLP overestimates the leachability of most hazardous elements, such as Be, B, Co, Ni, Cu, Zn, Cd, Sb, and U, at least in the studied alkaline fly ashes. LEAF tests have the advantage of being a comprehensive evaluation of the leaching characteristics, with a range of pH and L/S allowing for the examination of leachability under various conditions at different disposal or beneficial use scenarios.

Cotreatment of MSWI Fly Ash and Granulated Lead Smelting Slag Using a Geopolymer System.

Municipal solid waste incineration fly ash (MSWI FA) and granulated lead smelting slag (GLSS) are toxic industrial wastes. In the present study, granulated lead smelting slag (GLSS) was pretreated as a geopolymer precursor through the high-energy ball milling activation process, which could be used as a geopolymeric solidification/stabilization (S/S) reagent for MSWI FA. The S/S process has been estimated through the physical properties and heavy metals leachability of the S/S matrices. The results show that the compressive strength of the geopolymer matrix reaches 15.32 MPa after curing for 28 days under the best parameters, and the physical properties meet the requirement of MU10 grade fly ash brick. In addition, the toxicity characteristic leaching procedure (TCLP) test results show that arsenic and heavy metals are immobilized effectively in the geopolymer matrix, and their concentrations in the leachate are far below the US EPA TCLP limits. The hydration products of the geopolymer binder are characterized by X-ray diffraction and Fourier transform infrared methods. The results show that the geopolymer gel and Friedel’s salt are the main hydration products. The S/S mechanism of the arsenic and heavy metals in the geopolymer matrix mainly involves physical encapsulation of the geopolymer gel, geopolymer adsorption and ion exchange of Friedel’s salt.

Enhanced sorption capacities for lead and uranium using titanium phosphates; sorption, kinetics, equilibrium studies and mechanism implication

The application of new synthesized titanium phosphates to the lead and uranium removal from acidic aqueous solutions (pH 2) was explored. Batch sorption experiments were carried out using lead- and uranyl solutions of concentration range 50–6000 and 50–4000 mg·L−1 respectively. The effect of pH, concentration, competing cations, temperature and reaction time on the adsorption equilibrium was investigated. The sorbents were examined by FTIR, XRD, XPS and SEM-EDS and characterized as mix salts while the formation of precipitates chloropyromorphite (Pb5(PO4)3Cl) and sodium-autunite (NaUO2PO4) after sorption was demonstrated. Typical sorption isotherms were constructed and modelled by the Langmuir, Freundlich and Temkin equations. The highest sorption capacity values (qmax: 2000 mg·g−1 Pb and 1250 mg·g−1 U) were observed for TiP3 which contains sodium in its structure. The kinetic data, obtained at 298, 308 and 323 K, obeyed a pseudo-second order equation and thermodynamic parameters were calculated. EPA Toxicity Characteristic Leaching Procedure and desorption experiments were performed in order to test the environmental compatibility of the sorbents. The results indicated that the sorption of Pb and U on titanium phosphates can be interpreted by a model combining adsorption and surface complexation toward surface precipitation.

Environmental characterization of Sarcheshmeh Cu-smelting slag, Kerman, Iran: Application of geochemistry, mineralogy and single extraction methods

Annually, more than 370,000tons of slag waste is produced in Sarcheshmeh Copper Complex, the biggest Cu-producer in Iran. Geochemical, mineralogical and single extraction methods were used in order to evaluate the contamination potential of metal(loid)s associated with Sarcheshmeh smelting slags. Results showed that, like the other non-ferrous or base metal slags, Sarcheshmeh slags are considered as one of the metalliferous smelting wastes with the multi-elemental contamination potential of most of the potentially toxic elements. Mineralogical studies revealed that the mineral assemblage of the investigated samples is controlled by at least three main factors, including: (1) primary mineralogy of the ore concentrate (chalcocite, chalcopyrite, covellite±pyrite); (2) smelting process (magnetite, fayalite, pyroxene); and (3) weathering reactions in arid to semiarid climate conditions [thenardite (Na2SO4), bonattite (CuSO4·3H2O) and gypsum (CaSO4·2H2O)]. Results obtained from the U.S. EPA toxicity characteristic leaching procedure (TCLP) and water soluble tests revealed that the order of leachability of target elements from the most to the least in the slag samples is as S≫Cu>>Zn>Fe>Mo>Pb>Ni>Mn>Co>As>Se>Sb>Cd>Cr=Sn=Ag=Bi. The maximum contamination potential, higher than the considered toxicity regulatory levels (one-hundred times the U.S. EPA maximum contamination level in drinking water), of As (9.35mg/L), Mo (186.7mg/L), Sb (3.50mg/L) and Se (6.12mg/L) was observed in the alkaline leached solutions (pH9.67) of the sediments associated with the slag dump drainages, while the maximum concentrations of the other investigated elements such as Cu, Co, Cd, Fe, and Zn were measured in the acidic (pH<5) leached solutions. Annually, about 18.7% of Sarcheshmeh reverberatory slags are used for other purposes such as sandblasting. Wind blowing slag particles, produced from the grinding and sieving facilities, are responsible for the enrichment of elements such as As, Cu, Mo, Pb, Sb, Sn, Zn, Cr, S and Fe in the topsoils around the slag preparation site. Based on the acid acetic (0.43mol/L) and EDTA (0.05mol/L) leaching tests, the solubility and thus the bioavailability of these potentially toxic elements also were increased in the surface contaminated soils, a subject that is very important from environmental point of view. Obtained results also emphasize on the need for the greater caution in the slag waste management.

Mobility and speciation of arsenic in the coal fly ashes collected from the Savannah River Site (SRS)

Arsenic (As) leaching from coal fly ash stockpiled at waste disposal sites is a source of environmental concern. An array of techniques including batch extraction and column leaching tests, in combination with speciation analysis of chemically specific As species, was employed to evaluate the mobility of As in fly ashes collected from the U.S. DOE Savannah River Site. The results obtained using the U.S. EPA Toxicity Characteristic Leaching Procedure (TCLP), a two-step sequential extraction technique, and continuous column leaching experiments suggest that only a small portion of total As in the fly ashes was mobile, but mobilizable As could be a considerable fraction (3.1–43%), varying inversely with alkalinity of fly ash. Speciation analysis by using phosphate extraction suggests that arsenate (AsV) was the major extractable species in the fly ash samples. During the column leaching experiment, however, it was observed that arsenite (AsIII) was an important species leached out of the fly ashes, indicating species conversion during the leaching process. The matrix-bound AsV within the fly ash, once being released from the solid matrix, could be converted to AsIII during its transport inside the column. The pHs of leachates and fly ashes (both acidic in column leaching experiments here) could be related to the dominance of AsIII in the effluents.

Stabilizing lead bullets in shooting range soil by phosphate-based surface coating

Soil lead (Pb) is well known as a threat to human health and ecosystem. Although relatively insoluble, lead bullets in shooting range soil can be readily released into soluble forms through natural weathering processes and thus pose significant human and environmental risks. In this study, laboratory experiments were conducted to investigate if the Pb bullets in shooting range soil can be stabilized through surface coating of phosphate-based materials. Results indicated that FePO 4 or AlPO 4 coatings, insoluble metal phosphates, have been successfully formed on the surface of the Pb bullets. The EPA Toxicity Characteristic Leaching Procedure (TCLP) test showed that FePO 4 or AlPO 4 surface coating would effectively reduce the Pb solubility or leachability of the bullets. The surface coating under pH of 4 coating and 77–98% by AlPO 4 coating as compared with the non-coating. Leachable Pb concentration in the contaminated shooting range soil was reduced by 85–98% or 77–98% as a result of the FePO 4 or AlPO 4 solution treatment. This study demonstrated that the FePO 4 or AlPO 4 –based surface coating on lead bullets can effectively inhibit the Pb weathering and significantly reduce the Pb release from soil through in situ chemical stabilization, which could be potentially applicable as a cost-effective and environmental-sound technology for the remediation of Pb-contaminated shooting range soil.

Treatment method of hazardous pickling sludge by reusing as glass–ceramics nucleation agent

Heavy metal containing pickling sludge (PS) is one of the by-products of the stainless-steel-making industry, which has been considered hazardous due to contained chromium and nickel. Traditional methods of PS disposing are landfill and cement solidification. This research is aimed at disposing PS by solidification/stabilization and reusing it as a nucleation agent of glass–ceramics. The crystallization behavior and the properties of a glass in the CaO–MgO–SiO2–Al2O3 system were studied by considering PS as the nucleation agent. Experimental results confirm that introducing 14 wt% PS as the nucleation agent of glass–ceramics can decrease crystallization temperature by 110.8 °C, refine the grain size by forming isometric crystals with size of 2 μm, enhance Vickers hardness by 2690 MPa and decrease water absorption from (1.21 ± 0.10) wt% to (0.04 ± 0.01) wt%. Therefore, it is reasonable to conclude that PS can be utilized as a nucleation agent to improve the crystallization and mechanical properties of the glass–ceramics. The testing results of US EPA toxicity characteristic leaching procedure (TCLP) confirm the safety of this reusing method.

Trends in Toxic Metal Levels in Discarded Laptop Printed Circuit Boards

Waste printed circuit boards (PCBs) contain toxic metals at concentrations that could pose human and environmental threats if improperly disposed of. Also, PCBs are known to contain appreciable quantities of precious metals with economic value. This study investigated the levels of Cu, Pb, Ni, Zn and Cd in the PCBs extracted from ten discarded laptops and outlined the trends that can be drawn from the results. The laptops were made by a world-wide leading original equipment manufacturer (OEM). The whole laptops were disassembled to enable the extraction of populated PCBs; components were dismounted and all de-populated PCBs were separately crushed, sieved, and total recoverable metals aforementioned were extracted using EPA 3050B method. Also, PCBs were analysed following the EPA Toxicity Characteristic Leaching Procedure (TCLP) and the EPA Synthetic Precipitation Leaching Procedure (SPLP) tests to study their leachability when exposed to municipal landfill and rain water, respectively. The extracts were analysed for metal levels using atomic absorption spectrophotometric technique. The sequence of total recoverable metals was Cu (3.23±0.41%) &gt; Pb (1.95±0.57%) &gt; Ni (0.88±0.36%) &gt; Zn (0.012±0.003%) &gt; Cd (4.00±2.30 mg/kg). Our study revealed a reduction in average % Cu and Zn by at least 6 and 1.5 times, respectively compared with previous studies. The level of Pb also was noticed to decrease from 2.5% in PCBs produced in 2006 to 1.7% in those produced in 2009. On the one hand, this could be a sign of the efforts conducted by OEMs to shift towards the design of eco-friendly products. On the other hand, average Pb (mg/L) level in TCLP and SPLP leachates was respectively 13 and 11 times higher than EPA limit of 5mg/L. Discarded laptop PCBs should still be handled and disposed of as hazardous waste.

Leaching of Arsenic, Lead, and Antimony from Highway-Marking Glass Beads

AbstractGlass beads embedded in pavement markings provide retroreflectivity to ensure safe driving. Recently, elevated concentrations of arsenic (As), antimony (Sb), and lead (Pb) have been observed in glass beads imported to the US. After an initial assessment of total concentrations in glass beads, a factorial study was conducted to determine the impact of environmentally relevant factors on leaching: pH (4, 7, and 10), chemicals applied on roadways (NaCl, CaCl2, KCH3COO, and KCl), ionic strength (10−2–10−1 M), particle size (>100 and <37 μm), and time (18 h to 160 days). Additional leaching studies included the US EPA toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching procedure (SPLP). Results demonstrated that the most important factors affecting leaching were pH and time. For anions of As and Sb, leaching tended to increase with increasing pH, whereas for the cation Pb, leaching increased as pH decreased. As expected, leaching increased with a decrease in particl...

Migration of manganese and iron during the adsorption-regeneration cycles for arsenic removal

Fe-Mn binary oxide incorporated into porous diatomite (FMBO-diatomite) was prepared in situ and regenerated in a fixed-bed column for arsenite [As(III)] and arsenate [As(V)] removal. Four consecutive adsorption cycles were operated under the following conditions: Initial arsenic concentration of 0.1 mg·L−1, empty bed contact time of 5 min, and pH 7.0. About 3000, 3300, 3800, and 4500 bed volumes of eligible effluent (arsenic concentration ⩽ 0.01 mg·L−1) were obtained in four As (III) adsorption cycles; while about 2000, 2300, 2500, and 3100 bed volumes of eligible effluent were obtained in four As(V) adsorption cycles. The dissection results of FMBO-diatomite fixed-bed exhibited that small amounts of manganese and iron were transferred from the top of the fixed-bed to the bottom of the fixed-bed during As(III) removal process. Compared to the extremely low concentration of iron (<0.01 mg·L−1), the fluctuation concentration of Mn2+ in effluent of the As(III) removal column was in a range of 0.01–0.08 mg·L−1. The release of manganese suggested that manganese oxides played an important role in As(III) oxidation. Determined with the US EPA toxicity characteristic leaching procedure (TCLP), the leaching risk of As(III) on exhausted FMBO-diatomite was lower than that of As(V).

Heavy Metal Immobilization through Phosphate and Thermal Treatment of Dredged Sediments

Disposal of dredged sediments is expensive and poses a major challenge for harbor dredging projects. Therefore beneficial reuse of these sediments as construction material is highly desirable assuming contaminants such as heavy metals are immobilized and organics are mineralized. In this research, the effect of the addition of 2.5% phosphate, followed by thermal treatment at 700 degrees C, was investigated for metal contaminants in dredged sediments. Specifically, Zn speciation was evaluated, using X-ray absorption spectroscopy (XAS), by applying principal component analysis (PCA), target transformation (TT), and linear combination fit (LCF) to identify the main phases and their combination from an array of reference compounds. In dredged sediments, Zn was present as smithsonite (67%) and adsorbed to hydrous manganese oxides (18%) and hydrous iron oxides (15%). Phosphate addition resulted in precipitation of hopeite (22%), while calcination induced formation of spinels, gahnite (44%), and franklinite (34%). Although calcination was previously used to agglomerate phosphate phases by sintering, we found that it formed sparingly soluble Zn phases. Results from the U.S. EPA toxicity characteristic leaching procedure (TCLP) confirmed both phosphate addition and calcination reduced leachability of heavy metals with the combined treatment achieving up to an 89% reduction.

Ternary blends containing demercurated lighting phosphor and MSWI fly ash as high-performance binders for stabilizing and recycling electroplating sludge

This paper describes the solidification and stabilization of electroplating sludge treated with a high-performance binder made from portland type-I cement, municipal solid waste incineration fly ash, and lighting phosphor powder (called as cement–fly ash–phosphor binder, CFP). The highest 28-day unconfined compressive strength of the CFP-treated paste was 816 kg/cm 2 at a ratio of cement to fly ash to lighting phosphor powder of 90:5:5; the strength of this composition also fulfilled the requirement of a high-strength concrete (>460 kg/cm 2 at 28 days). The CFP-stabilized sludge paste samples passed the Taiwanese EPA toxicity characteristic leaching procedure test and, therefore, could be used either as a building material or as a controlled low-strength material, depending on the sludge-to-CFP binder ratio.

Remediation of chromite ore processing residue using ferrous sulfate and calcium polysulfide

Batch tests were conducted to assess the potential use of ferrous sulfate and calcium polysulfide for the remediation of chromite ore processing residue (COPR). The remediation process entails addition of ferrous sulfate or calcium polysulfide to chemically reduce hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] in slurry form and pH adjustment to precipitate Cr(III) as chromium hydroxide. The present study investigates the effects of COPR particle size, treatment pH, and chemical dosage on the performance of the treatment. Smaller particle size resulted in increases in alkaline digestion and Toxicity Characteristic Leaching Procedure (TCLP) Cr(VI) concentrations for the untreated samples. The chemical reduction of Cr(VI) with ferrous iron and sulfides was non-stoichiometric. Four times the stoichiometric amount of ferrous iron of two times the stoichiometric amount of polysulfide were needed to meet both the New Jersey Department of Environmental Protection (NJDEP) regulatory limit of 240 mg/kg for Cr(VI) and EPA TCLP regulatory limit of 5 mg/L for chromium [C,r]. pH adjustment was necessary to prevent the formation of ettringite, a swell causing mineral, upon the introduction of sulfate to the COPR material via ferrous sulfate or calcium polysulfide. The slow hydration of some COPR minerals caused the pH of the treated COPR to creep upward during the curing period. However, when sufficient acid was added, the pH value was controlled at less than 9.27 for a curing period of 1.5 years, which prevented the formation of ettringite.

Utilization of treated spent liquor sludge with fly ash in cement and concrete

Design mix of M-20 concrete was prepared in the laboratory by substituting cement with the treated spent liquor sludge (TSLS) and fly ash. During the study, TSLS is fixed at 7.5% by weight, and fly ash is varied as 5%, 10%, 15%, 20% and 25% to study the possibility of replacement of cement. A 15% fly ash gives the optimum compressive strength. Addition of fly ash has resulted in complete removal of toxicity as per US EPA toxicity characteristic leaching procedure (TCLP) test. A total of 7.5% sludge and 15% fly ash in M-20 concrete is expected to save Rs. 252/m 3 (≈USD 5.3/m 3) of concrete.

Chromium Leaching and Immobilization in Treated Soils

The purpose of this study is to investigate the effectiveness of a quicklime-based stabilization/solidification (s/s) technique to reduce the leachability of Cr(III) and Cr(VI) in laboratory-prepared soil. The soils were prepared by mixing kaolinite or montmorillonite with fine quartz sand and then subjecting the samples to s/s treatment. Treatment included quicklime, fly ash, and quicklime–fly ash additions. The effectiveness of the treatment was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) test. To elucidate the controlling Cr(VI) immobilization mechanisms, slurry mixtures were prepared with potassium chromate (K2CrO4), quicklime, and fly ash. X-ray diffraction (XRD) analyses were performed to investigate the reaction products responsible for Cr(VI) immobilization. Experimental results indicate very low Cr(III) leachability upon quicklime treatment. All samples treated with quicklime and quicklime–fly ash show TCLP Cr(III) concentrations below the U.S. EPA TCLP limit of 5 ppm. However, neither quicklime nor fly ash treatment alone was effective in reducing Cr(VI) leachability. An effective reduction in Cr(VI) leachability was achieved only when both quicklime and fly ash were added to the laboratory-prepared soils. Previous research has attributed this reduction in Cr(VI) leachability to the fly ash-induced chemical reduction of Cr(VI) to Cr(III). However, in this study, fly ash was found to be an ineffective reducing agent. XRD analyses results for quicklime–fly ash slurries do not indicate the formation of CaCrO4 or CaCrO4 · 2H2O, which were identified in previous research as the reaction products responsible for Cr(VI) immobilization. A hypothesis is presented in this paper to explain these results and the effectiveness of quicklime-fly ash mixtures in reducing the leachability of Cr(VI). XRD analyses have also identified the pozzolanic compound 3CaOAl2O30.5CaCrO40.5CaSO4 · nH2O as the precipitate most likely responsible for Cr(VI) immobilization.

Leaching of APC residues from secondary Pb metallurgy using single extraction tests: the mineralogical and the geochemical approach

Two air-pollution-control (APC) residues – one from flue gas cooling with alkaline water and one from deionised water cooling – from secondary lead metallurgy were submitted to two different standardized short-term leaching protocols: US EPA toxicity characteristic leaching procedure (TCLP) and static leaching according to Czech/European norm EN 12457-2. The experimental procedure was coupled with detailed mineralogical investigation of the solid material (SEM, XRPD) and speciation-solubility calculations using the PHREEQC-2 geochemical code. Both types of residues were considered as hazardous materials exhibiting substantial leaching of Pb (up to 7130 mg/l) and other inorganic contaminants. However, the APC residue produced by flue gas cooling with alkaline water (sample B) exhibits more favourable leaching and environmental characteristics than that produced by simple deionised water cooling (sample A). At pH < 5, primary caracolite (Na 3Pb 2(SO 4) 3Cl) and potassium lead chloride (KCl·2PbCl 2) are completely or partially dissolved and transformed to residual anglesite (PbSO 4), cotunnite (PbCl 2) and laurionite (Pb(OH)Cl). At pH 5–6, anglesite is still the principal residual product, whereas at pH >6, phosgenite (PbCl 2·PbCO 3) became the dominant secondary phase. The results are consistent with the mineralogical and geochemical studies focused on acidic forest soils highly polluted by smelter emissions, where anglesite, as a unique Pb-bearing phase, has been detected. From the technological point of view, the mixing of APC residue with alkaline water, followed by an increase in the suspension pH and equilibration with atmospheric CO 2, may be used to ensure the precipitation of less soluble Pb carbonates, which are more easily recycled in the Pb recovery process in the metallurgical plant.

In situ remediation of soils contaminated with toxic metal ions using microwave energy

Following onto our work on the in situ remediation of soils contaminated with PAH’s, PCB’s and other polychlorinated organic compounds using microwave energy, we now report a preliminary investigation on the in situ remediation of soils contaminated with toxic metal ions: Cd(II), Mn(II), Th(IV), Cr(III) and mainly Cr(VI). The soil is partially vitrified in the process, and extraction with hot (70 °C) 35% nitric acid for 4.5 h leads to the recovery of very small amounts of the metals which had been spiked into the clean soil: Cd, Mn, and Cr(III) are completely immobilized (unextractable), Th is mostly unextractable, and Cr(VI) partially extractable at very high levels of spiking, but almost completely unextractable using the US EPA Toxicity Characteristic Leaching Procedure. This suggests that contaminated soils which are not going to be used for agricultural purposes can be remediated safely to preset depths without fear of the toxic metal ions leaching out for a long time.

Leaching of metals from soil contaminated by mining activities

Stabilization/solidification (s/s) is one of the most effective methods of dealing with heavy metal contaminated sites. The ability of lime and cement stabilization to immobilize Pb, Cu and Fe contained in a contaminated soil originating from an old mining and smelting area located along the Mediterranean Sea shore in northern Cyprus was investigated. The stabilization was evaluated by applying leaching tests. A series of tests were conducted to optimize the additive soil ratio for the best immobilization process. Additive/soil=1/15 (m/m) ratio was found to be the optimum for both lime and cement. Application of the US EPA toxicity characteristic leaching procedure (TCLP) on the soil samples treated with lime at additive/soil=1/15 (m/m) mixing ratios showed that Cu and Fe solubility was reduced at 94 and 90%, respectively. The results of cement treatment using the same ratio, reduced the solubility 48 and 71% for Cu and Fe, respectively. The Pb solubility was found to be below the regulatory limit of 5 mg/l so no additive treatment was needed. The optimum additive/soil amount (1/15) was selected for more detailed column studies, that were carried out in the acidic pH range. According to the results of column leaching tests, it was found that, the degree of heavy metal leaching is highly dependent on pH.