Lindane Biodegradation by Defined Consortia of Indigenous Streptomyces Strains

The current study aimed to compare lindane degradation by pure and mixed cultures of Streptomyces sp. Cell-free extracts were assayed for potentiating dechlorinase activity and, based on these results, consortia of two to six microorganisms were assayed for their growth on and degradation of lindane. Furthermore, the role of bacterial consortia of lindane-degrading strains was examined in lindane decontamination soil assays. Four actinobacteria, previously isolated from a pesticide-contaminated area, were selected because of their tolerance to lindane and their ability to use the pesticide as sole carbon source. These strains as well as Streptomyces sp. M7 and Streptomyces coelicolor A3 were used to study specific dechlorinase activity (SDA) and lindane removal in mixed cultures. Pure cultures presented SDA in the presence of 1.66 mg L^-1 lindane as carbon source. SDA was improved by certain mixed cultures until 12 times compared with pure cultures. Mixed cultures with two, three, and four strains showed maximum lindane removal of 46% to 68%, whereas combinations of five and six strains did not efficiently remove the pesticide from the culture medium. The Streptomyces sp. A2, A5, M7, and A11 consortium presented the lowest ratio between residual lindane concentration and SDA and could be a promising tool for lindane biodegradation.     

Laboratory Study of Leaching Properties of Mediterranean Forest Species Ashes

For bioremediation of copper-contaminated soils, it is essential to understand copper adsorption and chemical forms in soils related to microbes. In this study, a Penicillium strain, which can tolerate high copper concentrations up to 150 mmol l^?1 Cu²⁺, was isolated from a copper mining area. The objective was to study effects of this fungus on copper adsorptions in solutions and chemical forms in soils. Results from lab experiments showed the maximum biosorptions occurred at 360 min with 6.15 and 15.08 mg g^?1 biomass from the media with Cu²⁺ of 50 and 500 mg l^?1, respectively. The copper was quickly adsorbed by the fungus within the contact time of the first 60 min. To characterize the adsorption process of copper, four types of kinetics models were used to fit the copper adsorption data vs. time. Among the kinetics models, the two-constant equation gave the best results, as indicated by the high coefficients of determination (R ²?=?0.89) and high significance (p?<?0.01). The addition of the fungal strain to autoclaved soil facilitated increases in concentrations of acid-soluble copper, copper bound to oxides, and of copper bound to organic matter (p?<?0.05). However, the inoculation of Penicillium sp. A1 led to a decrease of water-soluble copper in the soil. The results suggested that Penicillium sp. A1 has the potential for bioremediation of copper-contaminated soils.     

Intracellular chromium accumulation by <Emphasis Type="Italic">Streptomyces</Emphasis> sp. MC1

Streptomyces sp. MC1, previously isolated from sugar cane, has shown ability to reduce Cr(VI) in liquid minimal medium and soil samples. The objective of this work was to demonstrate the intracellular chromium accumulation by Streptomyces sp. MC1 under different culture conditions. This strain was able to accumulate up to 3.54 mg of Cr(III) per gram of wet biomass, reducing the 98% of Cr(VI) and removing 13.9% of chromium from the culture medium supernatants. Streptomyces sp. MC1 chromium bioaccumulation ability was corroborated by using Timm’s reagent technique, a low-cost method, which has been used by first time to detect chromium deposits in bacteria. The results of atomic absorption spectrometry, scanning electron microscopy, and energy dispersive X-ray analysis suggest that the mechanism of Cr(VI) resistance observed in Streptomyces sp. MC1 includes adsorption coupled with reduction to Cr(III), and finally, Cr(III) bioaccumulation. This mechanism have special relevance to remediation of Cr(VI) contaminated environments by Streptomyces sp. MC1.     

Differential copper impact on density,diversity and resistance of adapted culturable bacterial populations according to soil organic status

The effect of copper on the abundance, diversity and resistance of viable heterotrophic and copper resistant bacterial populations (Cu^R) was evaluated in soils differing only by their amount and type of organic matter. These soils have been obtained using a vineyard soil that had been subjected to three different organic matter managements (Not Amended (NA) or amended with Straw (S) or Conifer Compost (CC)) in a long term field experiment. Soil microcosms were artificially contaminated with copper (250 mg Cu kg^?1 of soil) and incubated for 35 days. Throughout the incubation, a differential copper impact on viable heterotrophic and Cu^R bacterial enumeration was demonstrated according to the soil organic status with a magnitude which followed the order: NA > CC ≥ S. Diversity of Cu^R bacteria revealed no significant difference between the uncontaminated soils, as determined by 16S rRNA sequencing. However, copper spiking induced an enrichment of particular populations depending on soil, with Methylobacterium, Ralstonia and Staphylococcus like species becoming dominant in NA, S and CC soils, respectively. Evaluation of the copA gene distribution and diversity, through PCR detection and sequencing, revealed that few Cu^R bacteria (from 7 to 13%) possessed this genetic determinant before the addition of metal. Copper contamination induced an increase in the dissemination of homologous copA genes only in Ralstonia like species indigenous to S soils. From a functional point of view, copper minimum inhibitory concentration for each Cu^R strain was measured. It did not highlight variable copper resistance efficiency between strains belonging to different taxonomic groups, harboring or not the copA gene, and originating from different soils contaminated or not by copper.     

Selection of phosphorus solubilizing bacteria with biocontrol potential for growth in phosphorus rich animal bone charcoal

Bacteria with the ability to solubilize phosphorus (P) and to improve plant health were selected and tested for growth and survival in P-rich animal bone charcoal (ABC). ABC is suggested to be suitable as a carrier for biocontrol agents, offering them a protected niche as well as delivering phosphate to plants, meanwhile re-using P from waste of the food chain. Ninety-seven bacterial isolates from different soils were tested for their potential to dissolve P from ABC. Of these isolates, 60% showed positive scores; they belonged to the genera Arthrobacter, Bacillus, Burkholderia, Collimonas, Paenibacillus, Pseudomonas, Serratia, and Streptomyces. Twelve isolates from different taxonomic groups were selected for further research on growth ability and survival in ABC, and on their potential to control plant pathogens. The highest concentrations of P were dissolved by Pseudomonas chlororaphis and Bacillus pumilus, followed by Paenibacillus polymyxa, Burkholderia pyrrocinia and three Streptomyces isolates. P. chlororaphis and P. polymyxa showed strongest growth inhibition of plant pathogenic Pythium and Fusarium sp., followed by the Streptomyces spp. isolates.     

Streptomyces sp: A source of odorous substances in potable water

Growth medium containing an aquatic actinomycete Streptomyces sp. was analyzed by gas-liquid chromatography and mass spectrometry for the purpose of identifying substances that may represent potential odorous contaminants of water. Twenty-one odorous and nonodorous compounds were identified. Phenyl, C₂, and C₄ structures were predominant. Free fatty acids from C₁₃ to C₁₆ were detected and in some cases accompanied by their ethyl (C₁₆) and butyl (C₁₅ and C₁₆) esters. The long-chain acids and esters had no detectable odor. Although goesmin, an earthy smelling substance with a low odor threshold, was detected, butyric acid was the principal metabolite under the growth conditions employed and represented the greatest potential as an odorous water pollutant under natural conditions.     

Effect of Metals on Decolorization of Reactive Blue HERD by <Emphasis Type="Italic">Comamonas</Emphasis> sp. UVS

Comamonas sp. UVS was able to decolorize Reactive Blue HERD (RBHERD) dye (50 mg L^?1) within 6 h under static condition. The maximum dye concentration degraded was 1,200 mg L^?1 within 210 h. A numerical simulation with the model gives an optimal value of 35.71?±?0.696 mg dye g^?1 cell h^?1 for maximum rate (V_max) and 112.35?±?0.34 mg L^?1 for the Michaelis constant (K_m). Comamonas sp. UVS has capability of decolorization of RBHERD in the presence of Mg²⁺, Ca²⁺, Cd²⁺, and Zn²⁺, whereas decolorization was completely inhibited by Cu²⁺. Metal ions also affected the levels of biotransformation enzymes during decolorization of RBHERD. Comamonas sp. UVS was also able to decolorize textile effluent with significant reduction in COD. The biodegradation of RBHERD dye was monitored by UV–vis spectroscopy, FTIR spectroscopy, and HPLC.     

Effects of bio-organic fertilizer plus soil amendment on the control of tobacco bacterial wilt and composition of soil bacterial communities

Tobacco bacterial wilt (TBW) is caused by Ralstonia solanacearum (R. solanacearum), a severe pathogenic agent with a wide host range. In this study, lime?+?ammonium bicarbonate (L?+?AB), organic fertilizer (OF), bio-organic fertilizer (BOF), and integrated treatment (L?+?AB?+?BOF) were assessed for the ability to control TBW and to influence the composition of native soil bacterial communities. The results showed that disease incidence of L?+?AB?+?BOF for two growth seasons in pot experiment was the lowest, with only 15.56 and 11.11 % at seasons 1 and 2, respectively. The integrated treatment could also significantly suppress TBW in the field, with a disease incidence of only 14.27 % compared with 35.41, 50.03, and 31.32 % in L?+?AB, OF, and BOF treatments, respectively. With application of the integrated treatment in pot and field experiments, the abundances of R. solanacearum were both significantly lower than those with other treatments. Denaturing gradient gel electrophoresis (DGGE) patterns showed that application of BOF significantly affected composition of bacterial communities of rhizosphere. The analysis of 454 sequencing data showed that application of integrated treatment recruited more beneficial bacteria than other treatments, such as Bacillus, Paenibacillus, Arthrobacter, and Streptomyces, while the abundance of Ralstonia with the integrated treatment was decreased. Overall, these results suggested that application of integrated agricultural management could effectively suppress bacterial wilt by affecting the composition of bacterial community and reducing the population of R. solanacearum.     

Heavy metal accumulation by three species of mosses in Shillong,North-Eastern India

Comparisons were made of the accumulation of cadmium, copper, manganese, lead, and zinc in Plagiothecium denticulatum, Bryum argenteum and Sphagnum sp. in Shillong, Meghalaya State, Northeastern India. Samples of P. denticulatum and B. argenteum were collected inside Shillong city (urban) and its immediately adjacent outskirts (suburban), while Sphagnum sp. was collected from a suburban site only. Lead and copper levels were higher in P. denticulatum, while Sphagnum sp. accumulated higher amounts of zinc, manganese, and cadmium. An urban-suburban gradient was evident for lead and zinc in P. denticulatum, and for cadmium in B. argenteum, while a reverse trend could be discerned for manganese in P. denticulatum. Besides vehicles and minor industries, quarry dust was likely to be an important source of manganese, copper, and zinc.     

Adsorption features of Cu(II), Pb(II), and Zn(II) by an ordinary chernozem from nitrate,chloride, acetate,and sulfate solutions

The effect of Cl^?,SO ₄ ^2? , CH₃COO^?, and NO ₃ ^? anions on the adsorption of copper, lead, and zinc by an ordinary chernozem has been studied. The effect of the anions on the adsorption of Cu²⁺, Pb²⁺, Zn²⁺ ions is significant but uncertain. It has been shown that the attendant anions affect the shape of the adsorption isotherms, which are described by the Langmuir, Freundlich, or Henri equations. The constants of the adsorption from a nitrate solution calculated from the Langmuir equation (K _L) decrease in the following order: Cu²⁺ > Pb²⁺ >> Zn²⁺. The values of the maximum adsorption (C _max) decrease in the following order: Cu²⁺ ≥ Zn²⁺ > Pb²⁺ for acetate solutions and in the series Pb²⁺ > Zn²⁺ ≥ Cu²⁺ for nitrate solutions. The values of the Henry constants (K _H) calculated for the adsorption of the same cations from chloride solutions decrease in the same order as the values of K _L. The CH₃COO^? anion has the highest effect on the constant values. The NO ₃ ^? and Cl^? anions “switch their places” depending on the attendant cation, but their effect is always lower than that of the acetate anion. The values of C _max for copper and zinc are most affected by the CH₃COO^? anion, and the adsorption of zinc is most affected by the Cl^? and NO ₃ ^? anions. The assessment of the mobility of the adsorbed cations from the extraction with ammonium acetate (pH 4.8) has shown that the content of the desorbed metals is always lower than the content of the adsorbed cations and varies from 0.025 to 83%. According to their mobility, the adsorbed metals form the following order: Zn²⁺ > Pb²⁺ > Cu²⁺. The effect of the attendant anions on the extractability of the adsorbed cations decreases in the following order: chlorides > sulfates > acetates > nitrates.     

Effects of Ca,Mg, K,Na, and pH on Copper Toxicity to Pakchoi (Brassica chinensis L.)

The influence of calcium, magnesium, sodium, and potassium (Ca²⁺, Mg²⁺, Na⁺, K⁺) ions and pH on copper (Cu) toxicity to pakchoi (Brassica chinensis L.) was independently estimated by measuring root elongation in nutrient solutions. Increases in Ca²⁺, Mg²⁺, and hydrogen (H⁺) significantly increased the 5-d EC50Cu_T (expressed as total soluble Cu) by a factor of 12 for all treatments, which clearly demonstrated the limitation of using total Cu concentration to predict Cu toxicity to pakchoi. EC50{Cu²⁺} (expressed as free Cu²⁺ activity) was not significantly influenced by changing the Ca²⁺, Mg²⁺, and H⁺ activities. The nonlinear relationship between EC50{Cu²⁺} and cations indicated that competition for binding sites between Cu²⁺ and cations was not a significant factor in determining toxicity of Cu²⁺ for pakchoi. The lower variation of EC50{Cu²⁺} suggests that free Cu²⁺ activity was a better predictor of toxicity to pakchoi than EC50Cu_T.     

Using electrical signals of microbial fuel cells to detect copper stress on soil microorganisms

A method based on microbial fuel cells (MFCs) was used to evaluate the effects of copper (Cu²⁺) on soil microorganisms. Soil spiked with 50–400 mg kg^?1 of Cu²⁺ as CuCl₂ was incubated for 24 hours before being packed into the MFC anode chambers and assayed for dehydrogenase activity (DHA), substrate‐induced respiration (SIR) and microbial biomass carbon (C_mic). Soil was amended with 5% (w/w) glucose to accelerate ‘start‐up’ and improve power generation, followed by 150 hours of operation. Anode biofilm and soil was extracted to recover total nucleic acids and the 16S rRNA gene was subjected to PCR‐DGGE, sequencing and phylogenetic analysis. Results showed that increases in soil Cu²⁺ concentrations reduced voltage and postponed start‐up. The quantity of generated electrons within 48 hours was 32.5 coulomb (C) in the without‐Cu control and decreased with increasing Cu²⁺ concentrations (11.7, 7.7, 2.0 and 1.3 C under 50, 100, 200 and 400 mg kg^?1 Cu²⁺, respectively). Cyclic voltammetry identified decreased soil electrochemical activity with increasing Cu²⁺ concentrations. The results indicate that Cu²⁺ reduced electrical signals by inhibiting the electrochemical activity, metabolic activity and biomass of microorganisms. The 16S sequences of recovered anodic bacteria were assigned to Firmicutes, including Bacillaceae, Acetobacteraceae, Clostridium, Bacillus and Sporolactobacillus. In general, the DGGE band intensity of anodic bacteria decreased with increasing Cu²⁺ concentrations, except for bands assigned to Firmicutes and Bacillus, which increased with increasing Cu²⁺ concentrations. We suggest that the short‐term electrical signals generated from MFCs with contaminated soil can be used to assess the toxic effect of heavy metal pollutants on soil microorganisms.     

Synergists and antagonists in the rhizosphere modulate microbial communities and growth of Quercus robur L.

The synergistic and antagonistic interactions among biotic components in the rhizosphere play a crucial role in plant defence against soil-borne pathogens. We investigated if the rhizosphere helper bacterium Streptomyces sp. AcH 505 (HB) indirectly protects the plant from the parasitic nematode Pratylenchus penetrans by modifying the rhizosphere microbial community structure and whether these interactions are dependent on the growth stage of oaks. Changes in the abundance of Streptomyces sp. AcH 505 and the phospholipid fatty acid (PLFA) composition of the rhizosphere soil as well as oak shoot and root biomass were assessed. Investigated were the bud resting stage A and the bud swelling stage B with maximal root elongation of oak microcuttings at two successive harvest times. The deleterious effect of P. penetrans on oak biomass was dependent on plant development, being limited to oak microcuttings growing at the stage B. In comparison to control and HB inoculated soils, shoot biomass decreased by about 33% and 41%, and root biomass by about 33 and 48%, respectively. The antagonistic effect of Streptomyces against the nematode was linked to shifts in the rhizosphere microbial community. The Streptomyces AcH505 strain promoted growth of oak microcuttings at bud swelling stage B during maximal root elongation and enhanced the abundance of saprophytic and ectomycorrhizal fungi in the rhizosphere by 158% with respect to controls. Our results highlight the importance of Streptomyces for counteracting the damage of nematodes and promoting plant growth in natural ecosystems such as forests.     

Copper Release, Speciation, and Toxicity Following Multiple Floodings of Copper Enriched Agriculture Soils: Implications in Everglades Restoration

This study characterizes the effects of water–soil flooding volume ratio and flooding time on copper (Cu) desorption and toxicity following multiple floodings of field-collected soils from agricultural sites acquired under the Comprehensive Everglades Restoration Plan (CERP) in south Florida. Soils from four field sites were flooded with three water–soil ratios (2, 4, and 6 [water] to 1 [soil]) and held for 14 days to characterize the effects of volume ratio and flooding duration on Cu desorption (volume ratio and flooding duration study). Desorption of Cu was also characterized by flooding soils four times from seven field sites with a volume ratio of 2 (water) to 1 (soil) (multiple flooding study). Acute toxicity tests were also conducted using overlying waters from the first flooding event to characterize the effects of Cu on the survival of fathead minnows (Pimephales promelas), cladocerans (Daphnia magna), amphipods (Hyalella azteca), midges (Chironomus tentans), duckweed (Lemna minor), and Florida apple snails (Pomacea paludosa). Acute tests were also conducted with D. magna exposed to overlying water from the second and third flooding events. Results indicate that dissolved Cu concentrations in overlying water increased with flooding duration and decreased with volume ratio. In the multiple flooding study, initial Cu concentrations in soils ranged from 5 to 223 mg/kg (dw) and were similar to Cu concentration after four flooding events, indicating retention of Cu in soils. Copper desorption was dependent on soil Cu content and soil characteristics. Total Cu concentration in overlying water (Cu_w) was a function of dissolved organic carbon (DOC), alkalinity, and soil Cu concentration (Cu_s): log(Cu_w)?=?1.2909?+?0.0279 (DOC)?+?0.0026 (Cu_s)???0.0038 (alkalinity). The model was validated and highly predictive. Most of the desorbed Cu in the water column complexed with organic matter in the soils and accounted for 99% of the total dissolved Cu. Although total dissolved Cu concentrations in overlying water did not significantly decrease with number of flooding events, concentrations of free Cu²⁺ increased with the number of flooding events, due to a decrease in DOC concentrations. The fraction of bioavailable Cu species (Cu²⁺, CuOH⁺, CuCO₃) was also less than 1% of the total Cu. Overlying water from the first flooding event was only acutely toxic to the Florida apple snail from one site. However, overlying water from the third flooding of six out of seven soils was acutely toxic to D. magna. The decrease in DOC concentrations and increase in bioavailable Cu²⁺ species may explain the changes in acute toxicity to D. magna. Results of this study reveal potential for high Cu bioavailability (Cu²⁺) and toxicity to aquatic biota overtime in inundated agricultural lands acquired under the CERP.     

Atmospheric Bronze and Copper Corrosion as an Environmental Indicator. A Study Based on Chemical and Sulphur Isotope Data

Corrosion products have been takenfrom 130 copper or bronze outdoor objects all overEurope. Their chemical composition and crystalsymmetry have been determined by means of scanning electron microscopy (SEM/EDS) and X-ray powderdiffraction. Data on location, sampling, objectcharacteristics, general environment and air pollutionlevel; type, colour and chemical composition of thecorrosion layers have been obtained and evaluated by multivariate statistical analysis. The resultsverify that the highest air pollution levels are usually associated with the occurrence of thick,black or dark grey corrosion layers on copper orbronze objects, preferentially containing soot, ironoxide hydroxides, and antlerite,Cu₃(SO₄)(OH)₄. Pale green corrosionusually contains brochantite,Cu₄(SO₄)(OH)₆, and is rather associatedwith less polluted areas. Atacamite, a copper hydroxide chloride with the chemical formula Cu₂Cl(OH)₃, is preferentially observed in coastal regions.In addition, sulphur isotope analyses have beenperformed on eleven corrosion samples from citycenters. The δ³⁴S values are typically inthe region from +4 to +6‰ relative to the sulphurisotope standard CDT (Canyon Diablo Troilite) with amean value of 4.7±1.2 (1σ), therebyindicating that the sulphur in the corrosion layers,in the form of brochantite or antlerite, mainlyoriginates from a similar source despite geographicvariation, most likely sulphur contained in air pollutants.     

The Effects of Temperature, Suspended Solids, and Organic Carbon on Copper Toxicity to Two Aquatic Invertebrates

Ephemeral wetlands are characterized by temporal changes in abiotic characteristics that could ameliorate or exacerbate contaminant effects on resident species. The goal of this study was to determine the effects of temperature and naturally occurring suspended solids and organic carbon on the response of Daphnia pulex, and the calanoid copepod, Diaptomus clavipes, to a copper reference toxicant. Organisms were exposed to copper at 10, 20 and 30 ^°C in 48-h static renewal tests with a diluent of either reconstituted laboratory water or water from a wetland that had elevated levels of both suspended solids and organic carbon. 48-h LC₅₀ values were calculated for both total and free ion copper concentrations. When wetland water was used as the diluent, LC₅₀ values based on total copper concentrations were significantly greater than free ion LC₅₀s for both species. This difference was not as great in laboratory water, indicating that binding of the metal was greater in the wetland diluent and the free ion was largely responsible for toxicity. While D. clavipes was significantly less sensitive to the metal than D. pulex (48-h LC₅₀ for total copper in laboratory water at 20 ^°C 607.4 μg/L vs. 10.7 μg/L, respectively), the copepod exhibited a much greater response to increasing temperature. When the Biotic Ligand Model was used to generate free ion concentrations, it was found that measured concentrations exceeded the predicted values at each test condition; however measured LC₅₀ values for D. pulex were within a factor of two of the predicted LC₅₀'s at all temperatures and in both diluents.     

Diffusion-induced changes on exchangeable and organic bound copper fractions in acid soil samples enriched with copper

Transport-induced changes in the concentrations of NH₄Cl (Cu_E) and Na-pyrophosphate (Cu_P) extractable Cu in acid soils were studied by using diffusion cells in order to quantify Cu transport by measuring the variation of Cu_E and Cu_P in a half-cell with no copper added (receiving half-cell). An empirical approach based on the Freundlich equation was used to describe the relationship between Cu in the soil water extract, Cu_E, and Cu_P. After 30 d of diffusion, Cu_E and Cu_P in the receiving half-cells increased from 0.2 to 2.6% and from 4.1 to 24%, respectively, relative to their hypothetical concentrations after infinite time. Copper transport was found to be influenced by the nature of the soil and its moisture content.Diffusion was modeled in order to calculate the increase in Cu_E and Cu_P in the receiving half-cell, which were assumed to be in equilibrium with Cu in the soil water extract. Nonlinear retardation in the diffusive transport model was implemented by using the Freundlich equation to obtain nonlinear effective diffusion coefficients for each Cu fraction. The results of the simulations were consistent with their experimental counterparts, which suggests that the moisture content and retardation used in the model provide reasonable estimations of the increase in Cu_P in acid soils.     

Application of bio-organic fertilizer can control Fusarium wilt of cucumber plants by regulating microbial community of rhizosphere soil

Fusarium wilt, caused by Fusarium oxysporum f. sp. cucumerinum J. H. Owen, results in considerable yield losses for cucumber plants. A bio-organic fertilizer (BIO), which was a combination of manure composts with antagonistic microorganisms, and an organic fertilizer (OF) were evaluated for their efficiencies in controlling Fusarium wilt. Application of the BIO suppressed the disease incidence by 83% and reduced yield losses threefold compared with the application of OF. Analysis of microbial communities in rhizosphere soils by high-throughput pyrosequencing showed that more complex community structures were present in BIO than in OF treated soils. The dominant taxonomic phyla found in both samples were Proteobacteria, Firmicutes, Actinobacteria and Acidobacteria among bacteria and Ascomycota among fungi. Abundance of beneficial bacteria or fungi, such as Trichoderma, Hypoxylon, Tritirachium, Paenibacillus, Bacillus, Haliangium and Streptomyces, increased compared to the OF treatment, whereas the soil-borne pathogen, Fusarium, was markedly decreased. Overall, the results of this study demonstrate that the application of the BIO was a useful and effective approach to suppress Fusarium wilt and that the high-throughput 454 pyrosequencing was a suitable method for the characterization of microbial communities of rhizosphere soil of cucumber.     

Short‐scale distribution of copper fractions in a vineyard acid soil

We studied short‐scale variation in the total concentration of copper and its fractions in a soil vineyard. Soil samples were collected at a depth of 0–20 cm between plant rows (1), between individual plants (2) and at their base (3) in a vine‐grown plot in NW Spain. The mean total content in Cu (Cu_t) in the soil was found to be 97 mg kg⁻¹ and that of potentially available Cu (Cu_EDTA) 34 mg kg⁻¹. Copper bound to organic matter (Cu_OM) and to non‐crystalline inorganic soil components (Cu_IA) were the dominant fractions and accounted for 34% of total copper each. The contents in exchangeable (Cu_e), pyrophosphate‐extractable (Cu_p), oxalic/oxalate‐extractable (Cu_o) and total copper (Cu_t) exhibited statistically significant correlations with pH, sum of base cations (S), cation‐exchange capacity (CEC) and exchangeable calcium (Ca_e). Both total and fractional copper contents were higher in plant rows than between them, particularly in the centre of the plot. Also, Cu_OM and Cu_IA were higher in planting rows than between rows. These copper results may have been influenced by the vine‐growing practices of the area and also by the distribution of plants and their pruning. This variability pattern for Cu distribution is crucial with a view to minimising potential adverse effects of fungicides and optimising any reclamation treatments needed. Copyright © 2007 John Wiley & Sons, Ltd.     

Speciation of cadmium,copper, lead,and zinc in contaminated soils

Abstract

To investigate the activity of free cadmium (Cd²⁺), copper (Cu²⁺), lead (Pb²⁺), and zinc (Zn²⁺) ions and analyze their dependence on pH and other soil properties, ten contaminated soils were sampled and analyzed for total contents of Cd, Cu, Pb, and Zn (Cd_T, Cu_T, Pb_T, and Zn_T, respectively), 0.43 MHNO₃‐extractable Cd, Cu, Pb, and Zn (Cd_N, Cu_N, Pb_N, and Zn_N, respectively), pH, dissolved organic matter (DOC), cation exchange capacity (CEC), ammonium oxalate extractable aluminum (Al) and iron (Fe), and dissolved calcium [Ca²⁺]. The activity of free Pb²⁺, Cd²⁺, Cu²⁺, and Zn²⁺ ions in soil solutions was determined using Donnan equilibrium/graphite furnace atomic absorption (DE/GFAA). The solubility of Cd in soils varied from 0.16 to 0.94 μg L^‐1, Cu from 3.43 to 7.42 μg L^‐1, Pb from 1.23 to 5.8 μg L^‐1, and Zn from 24.5 to 34.3 μg L^‐. In saturation soil extracts, the activity of free Cd²⁺ ions constituted 42 to 82% of the dissolved fraction, for Cu²⁺the range was 0.1 to 7.8%, for Pb²⁺ 0.1 to 5.1% and for Zn²⁺2 to 72%. The principal species of Cd, Cu, Pb, and Zn in the soil solution is free metal ions and hydrolyzed ions. Soil pH displayed a pronounced effect on the activity of free Cd²⁺, Cu^2t, Pb²⁺, and Zn²⁺ ions.