Influence of humate-solute interactions on aqueous heavy metal ion levels

The extent to which heavy metal ions (Cu, Pb, Zn, Cd) are removed from aqueous solution by humic acid suspensions has been found to vary with solution pH, concentration of competing cations, nature of the organic material, and the complexing power of any ligands present. The amount adsorbed in acid media increased with pH until the threshold value required for partial dissolution of the solid, and formation of soluble metal humates, was exceeded The adsorption maximum pH, and the apparent capacity at lower values, varied with the substrate used and cation being sorbed. The affinity order sequence, as derived from adsorption isotherm studies, was Pb > Cu > Cd > Zn ? Ca > Mg. The retention of metal ion by the solid was reduced in the presence of ligands, with zero uptake occurring when the soluble complexes formed had a greater effective stability than those resulting from humic acid-metal ion interactions. With environmental systems having a high organic content, the humic acid component can play a dominant role in determining the final distribution of metal ions, and for predictive purposes, investigation of the effect of pH on uptake is more informative than measurement of adsorption isotherm parameters, since the observed trends reflect differences in functional group properties, relative affinities and solubility effects. The curves have minima which fall within the pH spreads encountered in natural systems, and small pH changes can cause significant variations in solution levels.     

Surface Modification of Sporopollenin with Calixarene Derivative

In this study, p-tert-butylcalix[4]-aza-crown (CAC) immobilized sporopollenin (Sp) was used as a sorbent for the removal of Cu(II), Pb(II) and Zn(II) from aqueous media. Sporopollenin was firstly functionalized with 3-chloropropyltrimethoxysilane (CPTS) in order to obtain chloro-sporopollenin (Sp-Cl). The Sp-Cl was reacted subsequently with CAC yielding CAC-bonded sporopollenin (Sp-Cl-CAC). The new sorbent was characterized by infrared spectroscopy (FTIR), thermal analysis (TG/DTG) and scanning electron microscopy (SEM). The sorption properties of modified sorbent (Sp-Cl-CAC) are also investigated. The optimum pH values for the separation of metal ions from aqueous solution onto Sp-Cl-CAC were 5.0 for Pb(II) and Cu(II) and 5.5 for Zn(II). The maximum sorption capacities for Cu(II), Pb(II) and Zn(II) were 0.07 (4.44?mg?g^?1), 0.07 (4.58?mg?g^?1) and 0.14 (29.00?mg?g^?1) mmol?g^?1, respectively. Sorption thermodynamic parameters of such as free energy (?G ^o), enthalpy (?H ^o), and entropy (?S ^o) were evaluated.     

Red wine antioxidants bind to human lipoproteins and protect them from metal ion-dependent and -independent oxidation

Plant-derived polyphenols may exert beneficial effects on atherosclerosis and cardiovascular diseases, in part, because of their antioxidant properties. In this study we compared the effects of unbound (free) and lipoprotein-associated red wine components on in vitro antioxidant protection of human low-density lipoprotein (LDL). Preincubation of LDL (1 mg protein/mL) with 0-2.5% (v/v) red wine for 3 h at 37 degrees C followed by gel filtration to remove unbound red wine components resulted in a dose-dependent, up to 4-fold increase in LDL-associated antioxidant capacity (measured as Trolox equivalents). Similar results were obtained with high-density lipoprotein (HDL) and bovine serum albumin (BSA). Furthermore, LDL was subjected to oxidation by copper and aqueous peroxyl radicals (2,2'-azobis[2-amidinopropane] dihydrochloride, AAPH). Under both types of oxidative stress, LDL-associated and free red wine components significantly decreased oxidation of the lipoprotein's protein moiety (assessed by tryptophan fluorescence) and lipid moiety (assessed by thiobarbituric acid-reactive substances and conjugated dienes). Similar protective effects of red wine components were observed against HDL oxidation. In contrast, red wine exerted a pro-oxidant effect on copper-induced oxidation of BSA tryptophan residues, while protecting them from AAPH-induced oxidation. Ascorbate strongly enhanced the protective effect of red wine against copper-induced LDL oxidation, and had an additive effect against AAPH-induced oxidation. Our data indicate that red wine components bind to LDL and HDL and protect these lipoproteins from metal ion-dependent and -independent protein and lipid oxidation.     

General purpose Freundlich isotherms for cadmium,copper and zinc in soils

Assessing the accumulation and transport of trace metals in soils and the associated toxicological risks on a national scale requires generally applicable sorption equations. Therefore Freundlich equations were derived for Cd, Zn and Cu using multiple linear regression on batch sorption data from the literature with a wide variety of soil and experimental characteristics, and metal concentrations ranging over five orders of magnitude. Equations were derived based on both total dissolved metal concentrations and free metal activities in solution. Free metal activities were calculated from total metal concentrations taking into account ionic activity, and inorganic (all metals) and organic complexation (Cu only). Cadmium and Zn were present in solution predominantly as free ions, while Cu was present as organic complexes. Since actual dissolved organic carbon (DOC) concentrations were not available they were estimated using an empirical field relation between DOC and organic matter content. The logarithmic transformation of the Freundlich constant for Cd was regressed on the logarithmic transformations of cation exchange capacity (CEC) (H⁺) and dissolved Ca, and for Zn with CEC and (H⁺). For Cu the log–log regression model of the Freundlich constant included the solid:solution ratio of the batch to account for dilution of DOC in the batch as compared with the field. The explained variance for the fitted Freundlich equations was 79% for Cd, 65% for Cu and 83% for Zn, using log-transformed adsorbed concentrations and soil solution activities. The Freundlich adsorption models underestimated metal contents determined from 1 m HNO₃ digestion on field samples, up to a factor of 6 (Cd and Cu) or 10 (Zn).     

Stability in solution and reactivity with soils and soil components of iron and zinc complexes

Naturally derived complexes with the ability to complex (unidentate) or chelate (polydentate) metals are a cheaper alternative to synthetic chelates to correct micronutrient deficiencies, but despite their widespread use there is a lack of knowledge on their agronomic performance. The aim of this paper was to evaluate the stability of iron (Fe) and zinc (Zn) lignosulfonate, gluconate, amino acid, and humate complexes in solution over time and at different pH values. Also, their stability in a concentrated nutrient solution and their reactivity with soils and soil components was evaluated. In our experimental conditions, all the complexes (except Fe amino acid) remained stable in solution for an extended period of time. All Zn complexes and the Fe lignosulfonate were stable in solution up to pH 7.0–7.5, while Fe gluconate only maintained 20%–40% of the iron in solution in the pH range 5–11 and Fe amino acid and humate complexes barely maintained small concentrations of Fe in solution above pH 3. Most of the complexes maintained Fe and Zn in concentrated nutrient solutions for irrigation systems, but Fe amino acid only maintained around 70% of the iron added. In general, the interactions of complexes with soils and soil components produced a high retention. The interaction of Fe lignosulfonate with peat, illite, and ferrihydrite, and Fe gluconate with peat and illite resulted in significant amounts of Fe to remain in solution, while for the Fe amino acid and humate the Fe remaining in solution was low. All Zn complexes were highly retained in an acidic peat, illite, and montmorillonite clays and soils, while no retention was observed on ferrihydrite. In conclusion, the stability of complexes in different conditions is related to the percentage of complexed element in the products. While complexes can be used to maintain micronutrients in solution in aqueous media (foliar and fertigation), their application to soil should be considered as a measure to increase metal availabilities but not their solubility.     

Influence of clay-solute interactions on aqueous heavy metal ion levels

The extent to which heavy metal ions (Cu, Pb, Zn, Cd) are removed from aqueous solution by clay suspensions (kaolinite, illite or montmorillonite) has been shown to vary with the nature of the clay, solution pH, concentration of competing cations, and the nature (and concentration) of any ligands present. The amount sorbed increases gradually with pH until the threshold value for formation of sparingly soluble hydroxy complexes is reached. The affinity order for divalent cations, and the nature of the sorption process also appear to vary with clay type.     

根迹土壤根诱导的化学变化对植物吸收重金属的影响

It is increasingly recognized that metal bioavailability is a better indicator of the potential for phytoremediation than the total metal concentration in soils; therefore, an understanding of the inffuence of phytoremediation plants on metal dynamics at the soil-root interface is increasingly vital for the successful implementation of this remediation technique. In this study, we investigated the heavy metal and soil solution chemical changes at field moisture, after growth of either Indian mustard (Brassica juncea) or sunffower (Helianthus annuus L.), in long-term contaminated soils and the subsequent metal uptake by the selected plants. In addition, the fractions of free metal ions in soil solution were determined using the Donnan membrane technique. After plant growth soil solution pH increased by 0.2-1.4 units and dissolved organic carbon (DOC) increased by 1-99 mg L^-1 in all soils examined. Soluble Cd and Zn decreased after Indian mustard growth in all soils examined, and this was attributed to increases in soil solution pH (by 0.9 units) after plant growth. Concentrations of soluble Cu and Pb decreased in acidic soils but increased in alkaline soils. This discrepancy was likely due to a competitive effect between plant-induced pH and DOC changes on the magnitude of metal solubility. The fractions of free Cd and Zn ranged from 7.2% to 32% and 6.4% to 73%, respectively, and they generally decreased as pH and DOC increased after plant growth. Metal uptake by plants was dependant on the soil solution metal concentration, which was governed by changes in pH and DOC induced by plant exudates, rather than on the total metal concentrations. Although plant uptake also varied with metal and soil types, overall soluble metal concentrations in the rhizosphere were mainly inffuenced by root-induced changes in pH and DOC which subsequently affected the metal uptake by plants.     

Dynamic headspace analysis of the release of volatile organic compounds from ethanolic systems by direct APCI-MS

Static equilibrium headspace was diluted with a stream of nitrogen to study the stability of the volatile headspace concentration. The headspace dilution profile of 18 volatile compounds above aqueous and ethanolic solutions was measured in real time using atmospheric pressure chemical ionization-mass spectrometry. Under dynamic conditions the volatiles headspace concentration above water solutions decreased readily upon dilution. The presence of ethanol helped to maintain the volatile headspace concentration when the ethanol solution concentration was above 50 mL/L. This effect was such that under dynamic conditions the absolute volatile concentration above an ethanolic solution was higher than that above an aqueous solution, contrary to results observed in equilibrium studies. The ratio of the headspace concentration of volatiles above ethanolic 120 mL/L and water solutions was correlated to their air/water partition coefficient.     

重金属污染土壤的植物修复研究Ⅲ.金属富集植物Brassica juncea对锌镉的吸收和积累

采用温室盆栽试验研究了印度芥菜对土壤中锌镉污染的忍耐、积累能力 ,以检验这种植物修复Zn、Cd污染土壤的可能性及其潜力。在加入Zn 5 0 0和 1 0 0 0mgkg- 1 的土壤中 ,印度芥菜生长 66天后 ,叶片中积累Zn的平均浓度分别达 2 80和 662mgkg- 1 ,地上部带走的Zn分别为每盆 2 1 95和 341 2 μg。在加入Cd 2 0 0mgkg- 1 的土壤中生长的印度芥菜 ,叶片中积累Cd浓度为 1 61mgkg- 1 ,地上部带走的Cd为每盆 381 μg。和普通植物相比 ,印度芥菜更能将Zn和Cd从根运输到地上部。Zn 5 0 0mgkg- 1 处理的土壤在种植印度芥菜后其NH4NO3提取的Zn显著高于不种植物的处理 ;土壤添加Cd 2 0 0mgkg- 1 的处理NH4NO3提取的Cd也显著高于不种植物的处理 ,可能的原因是植物根分泌出特殊的分泌物 ,专一性地螯合溶解根系附近的难溶态Zn和Cd,从而提高土壤溶液中的浓度。印度芥菜对Zn、Cd有较强的忍耐和富集能力 ,是Zn、Cd污染土壤修复有潜力的植物。     

Flavor-protein binding: disulfide interchange reactions between ovalbumin and volatile disulfides

The irreversible binding of selected sulfur-containing flavor compounds to proteins was investigated in aqueous solutions containing ovalbumin and a mixture of disulfides (diethyl, dipropyl, dibutyl, diallyl, and 2-furfuryl methyl) using solid-phase micro-extraction (SPME). In systems which had not been heated, the recovery of disulfides from the headspace above the protein at the native pH (6.7) was similar to that from an aqueous blank. However, significant losses were observed when the pH of the solution was increased to 8.0. When the protein was denatured by heating, much greater losses were observed and some free thiols were produced. In similar heat-denatured systems at pH 2.0, no losses of disulfides were observed. Disulfides containing allyl or furfuryl groups were more reactive than saturated alkyl disulfides. Interchange reactions between protein sulfhydryl groups and the disulfides are believed to be responsible for the loss of the disulfides.     

Suitability of Mn-Oxihydroxides from Karst Caves as Filter Material for Drinking Water Treatment in Gunung Sewu,Indonesia (6 pp)

Background, Aim and Scope   Manganese oxides are widely known as highly efficient heavy metal adsorbing materials. Therefore the use of natural materials containing Mn-oxihydroxides for the treatment of drinking water containing heavy metals in developing countries could be a cheap but nevertheless practical method. In the Karst area of Gunung Sewu, Java, Indonesia, people use the underground water resources as drinking water, which are endangered by heavy metal pollution. Local household filters have been considered for heavy metal elimination, to guarantee high quality drinking water from the Karst water. The aim of this study was to examine the suitability of mineral deposits containing Mn-oxihydroxides found in the Karst cave Bribin as filter material. Materials and Methods: Batch experiments were performed with the selected divalent cations Cd2+, Zn2+ and Ni2+ to test the adsorption efficiency of the Mn-rich deposits from Bribin to immobilize dissolved heavy metals. Results: Maximum adsorption capacities of 285 μmol/g for Cd2+, 217 μmol/g for Zn2+, and 178 μmol/g for Ni2+ were achieved after 24 h reaction time. These values are higher than literature values of Ni, Cd and Zn adsorption to other synthetic and natural manganese oxides. Discussion: Kinetic data from the batch experiments suggest that metal fixation occur in two steps; fast surface adsorption followed by a slower intercalation of the metal ions into the Mn-oxihydroxide lattice. Multi-element analysis of blank samples and samples under competitive conditions implies no desorption of metals from Mn-oxihydroxides. Conclusions: The sorption kinetics and capacities achieved in these experiments suggest that Mn-oxihydroxides from Bribin could be an effective filter material for drinking water purification. Recommendations and Perspectives: Nevertheless, reducing conditions in a filter system must be avoided to prevent Mn-oxides being reductively dissolved and the sorbed heavy metals mobilized.     

Efficient Purification of Heavy-Metal-Contaminated Water by Microalgae-Activated Pine Bark

Batch experiments were performed to study metal sorption by pine bark and algae-treated bark. The biosorption of copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd), cobalt (Co), and nickel (Ni) in synthetic multimetal aqueous solutions was studied as a function of metal content in solution, and amount and size of bark particles used for sorption. Influence of water hardness (Ca²⁺ only was tested) on the metal sorption process was also evaluated. Metal uptake from solutions with high heavy metal content (i.e. 10× the limit for leachate from landfills) was found to be independent of Ca²⁺ concentration. At low metal content in solution (i.e. 1× the limit for leachate from landfills), uptake of Cu, Zn, Ni, and Cd decreased with increasing Ca²⁺ content in water. Microalgae-treated bark was found to increase the metal sorption efficiency. Air-drying of bark-entrapped algae was shown to be the best method for sorbent drying. In general, the green algae, Chlorella sp. and Pseudokirchneriella subcapitata showed the best results in metal uptake. Sorption of Co, Zn, Ni, and Cd from solution with high levels of both heavy metals and calcium increased by almost 50% with algae treatment of bark was applied. At low levels of metals and calcium content, 100% uptake of Cu and Pb in water was observed. Uptake of other metals from solution with low metal and Ca content was relatively high (50–60%). Low pH (pH 3.0) had no influence on metal sorption from solutions with high metal content. For solutions with low metal content a decrease of metal uptake by 10–15% was observed for all the metals but Pb. Thus, the treatment of bark with microalgae was successful and influenced positively the uptake capacity of the bark.     

Effect of the physicochemical parameters of soils on the biological availability of natural and radioactive zinc

The relationship between the main physicochemical properties of soils and the accumulation of natural Zn and ⁶⁵Zn radionuclide has been studied, and the capacity of soils to limit the mobility of the element in the soil–plant system has been assessed. The contribution of each of the selected soil state parameters to the accumulation of zinc by barley has been determined, and the soil state parameters have been ranked. It has been found that the largest contributions to the variation of the resulting parameter (⁶⁵Zn accumulation coefficient, K_a) are made by mobile Fe (25%), free carbonates (21%), and acid-soluble Zn (18%). The largest contributions to the Zn_acK_a are made by free carbonates (13%) and mobile Fe (8%). The contributions of physical clay and organic carbon in soils and qualitative composition of humic substances are almost similar (4% for each). No differences in the inactivating capacity of different soils (soddy-podzolic soils, gray forest soils, and chernozems) for ⁶⁵Zn are observed. This is related to the fact that the transfer of ⁶⁵Zn to plants is statistically significantly controlled by the contents of free carbonates, mobile iron, and potentially plantavailable forms of stable natural Zn (carrier of ⁶⁵Zn) rather than the quantitative and qualitative composition of organic matter and the degree of dispersion of mineral particles. The analysis of the Zn_acK_a/⁶⁵Zn K_a ratios has shown that the share of plant-available Zn in the acid-soluble form of the metal (1 M HCl) is 0.61 on the average for the studied soils, and its share in the total Zn content in the soils is only 0.14.     

Modelling trace metal extractability and solubility in French forest soils by using soil properties

Soil/solution partitioning of trace metals (TM: Cd, Co, Cr, Cu, Ni, Sb, Pb and Zn) has been investigated in six French forest sites that have been subjected to TM atmospheric inputs. Soil profiles have been sampled and analysed for major soil properties, and CaCl₂‐extractable and total metal content. Metal concentrations (expressed on a molar basis) in soil (total), in CaCl₂ extracts and soil solution collected monthly from fresh soil by centrifugation, were in the order: Cr > Zn > Ni > Cu > Pb > Co > Sb > Cd , Zn > Cu > Pb = Ni > Co > Cd > Cr and Zn > Ni > Cu > Pb > Co > Cr > Cd > Sb , respectively. Metal extractability and solubility were predicted by using soil properties. Soil pH was the most significant property in predicting metal partitioning, but TM behaviour differed between acid and non‐acid soils. TM extractability was predicted significantly by soil pH for pH < 6, and by soil pH and Fe content for all soil conditions. Total metal concentration in soil solution was predicted well by soil pH and organic carbon content for Cd, Co, Cr, Ni and Zn, by Fe content for Cu, Cr, Ni, Pb and Sb and total soil metal content for Cu, Cr, Ni, Pb and Sb, with a better prediction for acidic conditions (pH < 6). At more alkaline pH conditions, solute concentrations of Cu, Cr, Sb and Pb were larger than predicted by the pH relationship, as a consequence of association with Fe colloids and complexing with dissolved organic carbon. Metal speciation in soil solutions determined by WHAM‐VI indicated that free metal ion (FMI) concentration was significantly related to soil pH for all pH conditions. The FMI concentrations of Cu and Zn were well predicted by pH alone, Pb by pH and Fe content and Cd, Co and Ni by soil pH and organic carbon content. Differences between soluble total metal and FMI concentrations were particularly large for pH < 6. This should be taken into account for risk and critical load assessment in the case of terrestrial ecosystems.     

Determination of free (pH 2.2) sulfite in wines by flow injection analysis: collaborative study

A method for the determination of free sulfite in wine by flow injection analysis (FIA) is described. The method involves liberation of sulfur dioxide from the wine at pH 2.2, with detection by decolorization of a malachite green solution. The method was collaboratively studied, and the results indicated an average reproducibility of 12% for white wine samples (average level 12.1 ppm SO2) and 26% for red wine samples (average level 3.1 ppm). When the FIA method was compared to an aeration/oxidation method, the results indicated a high degree of correlation between the 2 methods. The FIA method has been adopted by AOAC official first action.     

Sensitive streptavidin-biotin enzyme-linked immunosorbent assay for rapid screening of chloramphenicol residues in swine muscle tissue

A sensitive, competitive enzyme-linked immunosorbent assay (ELISA) for chloramphenicol (CAP) in swine muscle tissue has been developed. The ELISA is based on an earlier procedure. To improve sensitivity, different optimization procedures were investigated. The introduction of a streptavidin-biotin system and the use of a coating antigen with a lower CAP incorporation resulted in the most sensitive ELISA: the CAP concentration giving 50% inhibition decreased from 125 ng/mL to 3.0 ng/mL. This ELISA procedure was applied for a rapid screening of CAP residues in swine muscle tissue. The tissues were extracted with demineralized water. A concentrated phosphate-buffered saline solution was added to the filtered aqueous extract and this sample solution was directly submitted to the ELISA procedure. The results were compared to values obtained by analysis of a corresponding blank. This blank was prepared by treating a part of the aqueous sample solution with an immobilized monoclonal antibody preparation. This treatment was necessary because aqueous extracts of different swine muscle tissues showed a high variation in dose-response curves, probably caused by the complexity and variability of the matrix. In spiked tissues, the presence of CAP at concentrations of 10 micrograms/kg and higher can be easily demonstrated.     

An Assessment of the Fate of Metal Oxide Nanomaterials in Porous Media

Developing procedures for assessing the potential environmental fate and transport of nanomaterials is an active endeavor of the environmental technical research community. Insufficient information exists for estimating the likelihood of nanomaterial deposition on natural surfaces in aquatic environments. This work develops a framework for estimating potential metal oxide nanomaterial self-aggregation through the combined application of recent developments in diffuse layer model surface complexation theory with historical Derjaguin–Landau–Verwey–Overbeek (DLVO) procedures. Findings from the work include: 1) the surface, diffuse layer, and/or zeta potentials of nanomaterials in environmental aqueous systems are likely to have an absolute value less than 25 mV, 2) only nanomaterials with a Hamaker constant as large as 1E-19 J (and an absolute surface potential < 25 mV) will likely aggregate in most environmental aquatic media, 3) natural organic matter coatings may render metal oxide nanomaterials less likely to aggregate in aquatic systems, 4) nanomaterials in aqueous suspension will likely have an absolute surface potential less than their micron-sized counterparts of the same composition, and 5) robust diffuse layer model databases of intrinsic surface site reactivity constants with multivalent aqueous environmental ions will need to be developed in order to provide accurate mechanistic estimates of the surface potential of nanoparticles suspended in aqueous environmental systems.     

Red wine polyphenols alone or in association with ethanol prevent hypertension, cardiac hypertrophy, and production of reactive oxygen species in the insulin-resistant fructose-fed rat

The effects of a red wine polyphenolic extract (RWPE), ethanol, or both combined were evaluated in insulin resistant rats. Rats were fed for 6 weeks with fructose (60%)-enriched food and force-fed with (a) water only (F group), (b) aqueous solution of RWPE (100 mg/kg, FP group), (c) 10% (v/v) mixture of ethanol and water (FE group), or (d) solution containing the same amount of the RWPE and ethanol (FPE group). Animals fed a standard chow (C group) were used for comparison purpose. After 6 weeks, blood pressure was higher in F (130.0 x b1 1.7 mm Hg) than in C animals (109.6 x b1 0.9 mm Hg) and similar to the C group in all other fructose-fed treatment groups. Relative heart weight was higher in F (3.10 x b1 0.05) than in C (2.78 x b1 0.07) and significantly lower in FP (2.92 x b1 0.04) and FPE (2.87 x b1 0.08 mg/g) than in F animals. Left ventricle and aorta productions of reactive oxygen species (O2*-) were higher in F than in C groups and lowered by the RWPE but not by the ethanol treatment. Ethanol but not the RWPE treatment reduced the degree of insulin resistance in the fructose-fed rats. In summary, our study showed that polyphenols are able to prevent cardiac hypertrophy and production of reactive oxygen species in the insulin resistant fructose-fed rat.     

Retention of Cd, Cu, Pb and Zn by Wood Ash, Lime and Fume Dust

Heavy metals are of interest due to their deleterious impacts on both human and ecosystem health. This study investigated the effectiveness of wood ash in immobilizing the heavy metals Pb, Cd, Cu and Zn from aqueous solutions. The effects of initial metal concentrations, solution pH, ash dose and reaction time on metal sorption, as well as the metal sorption mechanisms were studied. To investigate the effect of initial metal concentrations, solutions containing Cd, Zn (25, 50, 75, 100 or 125 mg L^?1), Cu (25, 50, 75, 100, 125, 150 or 175 mg L^?1) or Pb (250, 500, 750, 1000, 1250, or 1500 mg L^?1) were reacted with 10 g L^?1 ash for two hours. For the effect of pH, solutions containing 100 mg L^?1 of Cd, Cu or Zn or 1500 mg L^?1 of Pb were reacted with 15 g L^?1 ash over a pH range of 4 to 7. The wood ash was effective in immobilizing the four metals with a sorption range of 41–100 %. The amounts of metals retained by the ash followed the order of Pb > Cu > Cd > Zn. As expected, absolute metal retention increased with increasing initial metal concentrations, solution pH and ash dose. Metal retention by the ash exhibited a two-phase step: an initial rapid uptake of the metal followed by a period of relatively slow removal of metal from solution. Metal retention by the ash could be described by the Langmuir and Freundlich isotherms, with the latter providing a better fit for the data. Dissolution of calcite /gypsum minerals and precipitation of metal carbonate/sulfate like minerals were probably responsible for metal immobilization by the ash in addition to adsorption.     

Chemical fractions of copper and zinc in organic‐rich particles from aqueous extracts of a metal‐contaminated granite soil

Abstract

Chemical fractions of copper (Cu) and zinc (Zn) in the organic‐rich particles collected from filtered aqueous extracts (<20 μm) of an acid soil were determined. A sequential extraction procedure was used to partition the particulate Cu and Zn into four operationally defined chemical fractions: adsorbed (ADS), iron (Fe) and manganese (Mn) oxides bound (FeMnOX), organic matter bound (OM) and residual (RESD). Total extractable concentrations of Cu and Zn in the fine particles were higher than their total concentrations in the original bulk soil. The concentration of particulate Cu was usually much higher than that of particulate Zn. Addition of lime stabilized sewage sludge cake and/or inorganic metal salts markedly increased the concentrations of particulate Cu and Zn in aqueous extracts, especially from limed soil. The proportional distributions of particulate Cu and Zn were quite similar. The two particulate metals were present predominantly in the ADS and FeMnOX fractions, with less (about 20%) in the OM and RESD fractions. Some of the ADS metal fraction was associated with dissolved organic substances. The concentrations of particulate Cu and Zn in the various extractable fractions were significantly affected by the application of lime, lime stabilized sewage sludge cake, or inorganic metal salts.