Effects of Low-Level Aqueous Hydrogen Sulfide and Other Sulfur Species on Lettuce (Lactuca sativa) Seed Germination

Low concentrations of aqueous hydrogen sulfide (H₂S) can stimulate growth of some crops. However, it is not clear whether H₂S provides crops with only sulfur and whether other sulfur compounds have similar beneficial effects. Therefore, impacts of solutions of sodium sulfate (Na₂SO₄), sodium sulfite (Na₂SO₃), sodium sulfide (Na₂S), ferrous sulfide (FeS), and H₂S at 0.01–1 mM were assessed on 5-day lettuce seed germination. Results showed that 0.01 mM H₂S solution significantly increased lettuce shoot elongation by 40 percent (to 43.6 mm from 31.0 mm in the control), whereas 0.1 mM increased elongation by 24 percent to 38.5 mm. Only a slight 10 percent increase was observed in 0.1 mM Na₂SO₄, suggesting that ameliorative impact of H₂S on plant growth was not a result of providing sulfur nutrient. Other sulfur solutions, however, inhibited lettuce germination and elongation to varying extents, hinting that H₂S might work as a signal molecule in regulating plant cellular activities.     

Microbial Sulfate Reduction and Biogeochemistry of Arsenic and Chromium Oxyanions in Anaerobic Bioreactors

A pilot-scale anaerobic bioreactor with high levels of microbial sulfate reduction, known to be capable of removing cationic metals from a metal- and acid-contaminated waste stream, was utilized to determine if the system would be effective in removing metals in the form of oxyanions such as arsenate and chromate. The system removed 90 % to >99 % of the arsenic and between 86 % and 94 % of the chromium from a waste stream containing 5 mg/L of each. Cadmium, copper, iron, lead, and zinc also were removed. An equilibrium geochemistry computer modeling code, MINTEQAK, modified from MINTEQA2, was used for the chemical modeling of processes in the bioreactor. Experimental evidence on the chemical and biological reduction of arsenic and chromium and fluorescent diffraction analysis of precipitates support the following hypotheses: the primary removal process for chromium was the reduction of Cr(VI) to Cr(III) by sulfides, followed by precipitation of chromium hydroxide [Cr(OH)_3(s)]; removal of arsenic was by direct microbial enzymatic reduction of As(V) to As(III) followed by precipitation of arsenic sulfides (As₂S₃ or AsS). Experimental evidence and modeling with MINTEQAK confirmed that 90 % to 95 % of the removal of arsenic and chromium occurred in the first quarter volume of the bioreactor. Additional removal of arsenic and chromium occurred in the remaining volume of the bioreactor. The use of a sulfate reduction-based anaerobic treatment system was effective for metal-laden wastewater with elevated concentrations of arsenic and chromium.     

Mobility of Iron and Manganese within Two Citrus Genotypes after Foliar Applications of Iron Sulfate and Manganese Sulfate

Seedlings of sour orange (Citrus aurantium L.) and Carrizo citrange (C. sinensis L. cv. Washington navel x Poncirus trifoliata)] were grown in plastic pots containing a sand: perlite mixture and watered with a modified Hoagland No 2 nutrient solution throughout the experiment. Three-months-old plants were divided in three groups and sprayed with 0.018 M iron sulfate (FeSO₄ ^.7H₂O), 0.018 M manganese sulfate (MnSO₄ ^.H₂O), or deionized water. Two months later, plants were harvested and divided into top leaves that grown after the treatments, basal leaves that existed prior to the treatments, stems that partially came in contact with the spray, and roots. The manganese (Mn) spray resulted in a significant increase of Mn concentrations in top leaves, basal leaves, stems and roots of sour orange, and in top leaves, basal leaves, and stems of Carrizo citrange. The iron (Fe) spray significantly increased the concentrations of Fe in the stems and basal leaves of both genotypes. For both genotypes, transport of Mn from basal (sprayed) leaves to top (unsprayed) ones was found. However, the results of this experiment did not give any evidence neither for Mn translocation from sprayed tissues to roots nor for Fe transport from sprayed tissues to unsprayed ones (top leaves, roots). Mn and Fe were found to be relatively mobile and strictly immobile nutrients, respectively, within citrus plants after their foliar application as sulfate salts.     

MINERAL NUTRIENT CONTENT OF TOMATO PLANTS IN AQUAPONIC AND HYDROPONIC SYSTEMS: EFFECT OF FOLIAR APPLICATION OF SOME MACRO- AND MICRO-NUTRIENTS

Effects of foliar applications of some micro- and macro-nutrients on mineral nutrient content of tomato leaves and fruits were investigated in an aquaponic system in comparison with a hydroponic system. Fourteen days old tomatoes seedlings were transplanted on to growth bed of aquaponic and hydroponic systems. Foliar nutrients application began 30 days after transplantation. Eight treatments were used, untreated control and foliar application at the rate of 250 mL plant^?1 with 0.5 g L^?1 potassium sulfate (K₂SO₄), magnesium sulfate (MgSO₄ 7H₂O), ferrous (Fe)- ethylenediamine-N,N′-bis (EDDHA), manganese sulfate (MnSO₄ H₂O), boric acid (H₃BO₃), zinc chloride (ZnCl₂), and copper sulfate (CuSO₄ 5H₂O). Foliar application of potassium (K), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) increased their corresponding concentrations in the leaves of aquaponic-treated plants. On the other hand, foliar spray of K, Fe, Mn, Zn, and Cu caused a significant increment of applied element concentrations in the fruits of hydroponic-grown plants. These findings indicated that foliar application of some elements can effectively alleviate nutrient deficiencies in the leaves of tomatoes grown on aquaponics.     

Microbial Reduction of Iodate

The different oxidation species of iodine have markedly different sorption properties. Hence, changes in iodine redox states can greatly affect the mobility of iodine in the environment. Although a major microbial role has been suggested in the past to account for these redox changes, little has been done to elucidate the responsible microorganisms or the mechanisms involved. In the work presented here, direct microbial reduction of iodate was demonstrated with anaerobic cell suspensions of the sulfate reducing bacterium Desulfovibrio desulfuricans which reduced 96% of an initial 100 µM iodate to iodide at pH 7 in 30 mM NaHCO₃ buffer, whereas anaerobic cell suspensions of the dissimilatory Fe(III)-reducing bacterium Shewanella putrefaciens were unable to reduce iodate in 30 mM NaHCO₃ buffer (pH 7). Both D. desulfuricans and S. putrefaciens were able to reduce iodate at pH 7 in 10 mM HEPES buffer. Both soluble ferrous iron and sulfide, as well as iron monosulfide (FeS) were shown to abiologically reduce iodate to iodide. These results indicate that ferric iron and/or sulfate reducing bacteria are capable of mediating both direct, enzymatic, as well as abiotic reduction of iodate in natural anaerobic environments. These microbially mediated reactions may be important factors in the fate and transport of¹²⁹ I in natural systems.     

Mercury Concentration and Monomethylmercury Production in Sediment: Effect of Dredged Sediment Reuse on Bioconcentration for Ragworms

The effect of dredged sediment reuse on the production and bioconcentration of monomethylmercury (MMHg) was investigated by examining sediments and ragworms found in dredge material banks and surrounding sites in the Venice Lagoon, Italy. Total Hg concentrations in the surface 20 cm of sediments were higher in the banks than in the surrounding sites, but MMHg concentrations were similar, which suggests reduced MMHg production in the banks. Monomethylmercury content in ragworms was significantly lower (p?<?0.05) in the banks than in the surrounding sites. In pore water, concentrations of both sulfate and Fe decreased with depth in the upper 20 cm of the dredge banks. In contrast, sulfate concentrations were constant with depth and large amounts of dissolved Fe occurred in the upper 20 cm of sediments of surrounding sites. Continuous sulfate reduction and possible precipitation of iron sulfide may decrease the production and bioconcentration of MMHg in the dredge material banks compared to the surrounding sites. Overall, the production of MMHg in sediments and its bioconcentration in benthic organisms were connected to the process of sediment diagenesis of organic matter through the control of pore water and sediment geochemistry involving iron and sulfur.     

PISTACHIO RESPONSES TO SALT STRESS AT VARIED LEVELS OF MAGNESIUM

Crop production in many parts of the world is increasingly affected by soil salinization, especially in the irrigated fields of arid and semi-arid regions. The effects of four magnesium levels [0, 0.5, 1, and 22 millliMolar (mM) magnesium as magnesium sulfate (MgSO₄.5H₂O)], and three salinity levels [0, 45 and 90 mM sodium chloride (NaCl)] on growth and the chemical composition of pistachio seedlings (Pistacia vera L.) cv. ‘Badami-e-Zarand’ was studied in sand culture under greenhouse conditions. The experiment was set up as a completely randomized design (CRD) with four replications. After 28 weeks the growth parameters of biomass, leaf number, leaf area and stem height were measured. The results demonstrated that salinity decreased biomass, leaf area and stem height; the application of 2 mM magnesium (Mg) significantly reduced biomass, leaf number, leaf area and stem height; salinity stress increased concentrations of sodium (Na) and potassium (K) in shoot as well as Na concentration in root; however, it decreased Mg and calcium (Ca) concentrations in shoot, as well as Mg, Ca, and K concentrations in root. The application of 2 mM Mg reduced K and Ca concentrations in shoot and Na and K concentrations in root.     

Mobility of Organic and Inorganic Zinc Fertilizers in Soils

Abstract

Zinc sulfate (ZnSO₄ · H₂O) has traditionally been the “reliable” source of zinc (Zn) fertilizer, but other sources of Zn are also available. Some are derived from industrial by‐products, varying from flue dust reacted with sulfuric acid to organic compounds derived from the paper industry. The degree of Zn mobility in Zn sources derived from these various by‐products is related to the manufacturing process, the source of complexing or chelating agents (organic sources), and the original product used as the Zn source. Many claims are made regarding the relative efficiency of traditional inorganic Zn fertilizers and complexed Zn sources. The objective of this column study was to compare the mobility of several commercial Zn fertilizer materials (organic and inorganic) that are commonly used to correct Zn deficiencies in soils. The sources included three granular inorganic Zn sources, two granular organically complexed Zn sources, and liquid ZnEDTA. Soil columns were leached five times with deionized water. Leaching events were separated by approximately 48 h. At the conclusion of the leaching phase, columns were analyzed for plant‐available Zn. Water solubility was the primary factor affecting Zn movement, not total Zn content or organic complexation of the fertilizers. The Zn sources evaluated can be separated into three groups: ZnEDTA, ZnLigno, and ZnSO₄ were the most mobile Zn sources; the ZnOx55 was less mobile, but seemed mobile enough to meet crop needs; ZnOx26 and ZnSuc were relatively immobile Zn sources.     

Toxicity of Uranium to Microbial Communities in Anaerobic Biofilms

Microbial processes have shown promise for the remediation of uranium and nitrate in groundwater impacted by uranium mine tailings. This study investigated the inhibitory impact of uranium(VI) towards different microbial populations in anaerobic biofilms, including methanogenic, denitrifying, and uranium-reducing microorganisms, which are commonly found at uranium bioremediation sites. Results of batch activity bioassays indicated a very distinct level of toxicity depending on the targeted microbial community. U(VI) caused severe inhibition of acetoclastic methanogenesis as indicated by a 50?% inhibiting concentration (IC₅₀) of only 0.16?mM. Denitrifying populations were also impacted by uranium, but their sensitivity depended on the electron donor utilized. Sulfur-oxidizing denitrifiers were the least affected (IC₅₀ for denitrification activity?=?0.32?mM), followed by H₂- and acetate-utilizing denitrifiers (IC₅₀ of 0.20 and 0.15?mM, respectively). In contrast, exposure to U(VI) concentrations up to 1.0?mM did not inhibit the rate of U(VI) bioreduction with H₂ as electron donor in the presence or absence of nitrate. On the contrary, a considerable increase in the uranium-reducing activity of the denitrifying and methanogenic mixed cultures was observed with increasing uranium concentrations. The results suggest that microorganisms responsible for U(V) reduction could tolerate much higher uranium concentrations compared to the other microbial populations assayed.     

Air Drying Affects Extractable Sulfate in Soils of Variable Charge: Test of Two Extraction and Two Quantification Methods

Abstract

Fertilizer recommendations need to be based on reliable soil sulfate determinations. Airdrying samples changes irreversibly many properties of soils with variable charge and might affect the extractable sulfate. In this study, sulfate extracted from air‐dry and field‐moist samples was compared. Two extracting solutions [water and 00.1 M Ca(H₂PO₄) ₂] and two quantification methods (turbidimetry and ion chromatography) were assayed on A and B horizon samples of five Humic Acrisols from southeast Mexico. Air drying increased water‐extractable sulfate in Ah horizons, whereas in Bt horizons, it increased the 00.1 M Ca(H₂PO₄)₂‐extractable sulfate. Airdrying increased dissolved organic carbon contents in all samples and increased soil acidity and oxalate extractable iron in 70 and 60% of the samples, respectively. Results showed larger coefficients of variation in air‐dried samples. Turbidimetry resulted less sensible than ion chromatography. To enhance sensitivity and reproducibility, particularly organic soil samples should be analyzed field‐moist and by ion chromatography.     

Changing pH shifts the microbial sourceas well as the magnitude of N2O emission from soil

Here, we examine the effect of long-term pH differences and short-term pH change on N₂O emissions from soil, and the microbial source (ammonia oxidation versus denitrification) of ¹⁵N-N₂O emissions. ¹⁵N-fertiliser (20 g N m^?2; 10 atom% excess ¹⁵N) was applied to (1) a silt loam soil of pH 7 held at 50% and 65% water-filled pore space (WFPS) (experiment 1) and (2) a loamy sand soil maintained at pH 4.5 and pH 7 for over 40 years (experiment 2). Soils were limed with CaCO₃ or acidified with H₂SO₄, and comparisons were made with unadjusted soils. Ammonia oxidation was the main microbial source of ¹⁵N-N₂O in soils limed to pH 7.0–8.1, unadjusted pH 7.1 (Experiment 1) and long-term pH 7 (experiment 2) soils. Eighty percent of ¹⁵N-N₂O from the long-term pH 4.5 soil (experiment 2) was derived from denitrification suggesting a possible inhibition of N₂O reduction. Short-term acidification to pH 5.6 or 4.3 lowered N₂O emissions. Liming of the pH 4.5 soil resulted in over four times greater N₂O emission (11 mg ¹⁴⁺¹⁵N-N₂O m^?2 over 41 days) than from the long-term pH 7.0 soil (experiment 2), with an associated increase in ammonia oxidiser-N₂O and decrease in denitrifier-N₂O production. This is the first report of a pH-induced change in microbial source of N₂O. Our results highlight the importance of distinguishing between short- and long-term effects of pH management when predicting N₂O emissions from soil, as they exhibit predominance of different microbial groups in N₂O production, with likely adaptation of the microbial community.     

Effects of bicarbonate and different Fe sources on vegetative growth and physiological characteristics of bell pepper (Capsicum annuum L.) plants in hydroponic system

In order to determine the best iron (Fe) sources under alkaline conditions, an factorial experiment was conducted based on a completely randomized design with two factors of Fe fertilizer at four forms [iron sulfate (FeSO₄), Fe- ethylenediaminetetraacetic acid (EDTA), Fe- diethylenetriaminepentaacetic acid (DTPA) and Fe- ethylenediamine-N,N’-bis (EDDHA), and sodium bicarbonate (NaHCO₃)] at three levels (0, 10 and 15 mM) with three replications. Results showed that the highest loss of vegetative growth (stem length, leaf number, leaf area, stem diameter, and leaf, stem and root dry weight) and ecophysiological parameters (F_v/F_m, SPAD and RWC) was observed in plants treated with FeSO₄. Alkalinity stress increased proline concentration especially in FeSO₄ treatment. Bicarbonate treatments decreased Fe concentration in plant tissues. Fe-EDTA and Fe-DTPA fertilizer sources acted similar or even better than EDDHA at 10 mM NaHCO₃ concentration, but the best Fe fertilizer source was Fe-EDDHA at 15 mM NaHCO₃ concentration.     

Differences in Response to Iron Deficiency Among Some Lines of Common Bean

Abstract

Five dry bean cultivars (Coco blanc, Striker, ARA14, SVM29‐21, and BAT477) were evaluated for their resistance to iron deficiency on the basis of chlorosis symptoms, plant growth, capacity to acidify the external medium and the root‐associated Fe³⁺‐reduction activity. Plants were grown in nutrient solution supplied or not with iron, 45 µM Fe(III)EDTA. For all cultivars, plants subjected to iron starvation exhibited Fe‐chlorosis. These symptoms were more severe and more precocious in BAT477 and Coco blanc than in the others cultivars. An important acidification of the culture medium was observed between the 4th and the 8th days of iron starvation in Striker, SVM29‐21 and, particularly, ARA14 plants. However, all Fe‐sufficient plants increased the nutrient solution pH. This capacity of acidification appeared more clearly when protons extrusion was measured in 10 mM KCl + 1 mM CaCl₂. The above genotypic differences were maintained: ARA14 showed the higher acidification followed by Coco blanc and BAT477. Iron deficiency led also to an increase of the root‐associated Fe(III)‐reductase activity in all lines. However, genotypic differences were observed: Striker shows the highest capacity of iron reduction under Fe deficiency condition.     

EFFECTS OF CALCIUM ON LIGNIFICATION RELATED PARAMETERS IN SODIUM CHLORIDE-STRESSED SOYBEAN ROOTS

The effects of exogenous calcium (Ca²⁺) on root growth and lignification-related parameters – phenylalanine ammonia-lyase (PAL) and peroxidases (POD) activities, hydrogen peroxide (H₂O₂) and lignin contents – in roots of NaCl-stressed soybean seedlings were analyzed. Three-day-old seedlings were cultivated in half-strength Hoagland's solution (pH 6.0) with or without 5 mM calcium nitrate [Ca(NO₃)₂] and 50 to 200 mM sodium chloride (NaCl) in a growth chamber (25°C, 12/12 h light/dark photoperiod, irradiance of 280 μmol m^?2 s^?1) for 24 h. In general, results showed that the absence of Ca²⁺ reduced root growth and increased lignification of soybean seedlings grown in NaCl-free nutrient solution. NaCl reduced the root growth and all lignification-related parameters. Root growth, PAL and POD activities and hydrogen peroxide (H₂O₂) contents were more affected after NaCl treatments without Ca²⁺ in the nutrient solution. At 5 mM, Ca²⁺ did not alleviate the deleterious effects of NaCl on lignification-related parameters.     

Redoxpotentiale und redoxprozesse von mangan-, eisenund schwefelverbindungen in hydromorphen böden und sedimenten

Results of laboratory experiments with soil material saturated with sea water indicate that, as predicted by thermodynamics, manganese (III, IV)-oxides are first reduced to Mn²⁺-ions (beginning at about +450 mV at pH 6.1.; E₇ ≈ +400 mV), next amorphous iron (III)-oxides are reduced to Fe²⁺-ions (beginning at about +220 mV at pH 6.0; E₇ ≈ +160 mV), and finally sulphates are reduced to sulphides (beginning at about +10 mV at pH 6.0; E₇ ≈ -50 mV). Direct quantitative relations between redox potentials, pH-values and Mn²⁺- (or Fe²⁺-) contents of water-saturated soils and sediments and calculated redox reactions of known manganese and iron systems could not be established.The influence of organic redox systems produced by microbial fermentation processes on the measured potentials and on the reduction of manganese and iron oxides is discussed.A reduction of the oxides by microbially formed sulphides, which themselves are oxidized by this process, seems also to be possible. Therefore, sulphides do not occur as stable sulphur phase in higher amounts before all available Fe-oxides are reduced to Fe²⁺-ions. Then formation of iron monosulphides takes place by precipitation of Fe²⁺- ions by sulphides (H₂S, HS). In a sulphide-stabilized environment redox reactions of sulphur — especially the reaction H₂S_aq = S₀ + 2 H⁺ + 2 e^? — may determined the measured potentials.The results show that the dynamics and morphology of hydromorphic soils and sediments are strongly dependent on microbial processes.     

Enzyme activities in soil treated with sulfite- or sulfate-based flue gas desulfurization products

A study was conducted to examine the impact of synthetic calcium sulfite (CaSO₃?·?0.5H₂O) and calcium sulfate (CaSO₄?·?2H₂O, i.e., gypsum) from flue gas desulfurization (FGD) on soil enzyme activities, used as soil quality indicators, following land application. We used application rates of 0, 1.12 Mg ha^?1 of FGD-CaSO₃ (CaS-1.12T), 3.36 Mg ha^?1 of FGD-CaSO₃ (CaS-3.36T), and 1.12 Mg ha^?1 of FGD-gypsum (Gyp-1.12T). The field experiments were conducted on a silt loam soil with 1.6 % total C and a pH of 6.5. No crop was grown during the experiment. The concentration of water soluble SO₄ ^2?-S and the associated electrical conductivity (EC) significantly increased during the first 2 weeks following gypsum application but decreased later on (2–4 weeks) due to leaching. There was no significant difference between the Gyp-1.12T and CaS-1.12T treatment after approximately 2 weeks indicating all of the sulfite in the CaS-1.12T treatment was completely oxidized to sulfate. In contrast, the sulfite treated with highest application rate (CaS-3.36T) was not completely oxidized within the 12-week experimental period. Application of FGD-CaSO₃ and FGD-CaSO₄ did not negatively affect C and N mineralization because β-glucosidase and β-d-glucosaminidase activities did not show any negative change compared with the control. Arylsulfatase activity of the CaS-1.12T treatment markedly declined compared with Gyp-1.12T and control, but then increased after 2 weeks. The arylsulfatase activity reduction, however, persisted for the duration of the experiment in the CaS-3.36T treatment. These activity changes were similar to the observed oxidation pattern of sulfite to sulfate, which indicated that arylsulfatase activity could be used as an indicator for the extent of sulfite oxidation in soil.     

Evaluation of Multi-Mixtures of Acids for the Sample Preparation of Organic Soil Amendments for Multi-Element Determination by ICP OES

A method for the simultaneous determination of aluminum (Al), arsenic (As), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), phosphorus (P), lead (Pb), sulfur (S), selenium (Se), vanadium (V), and zinc (Zn) in organic soil amendments using microwave-assisted acid digestion and inductively coupled plasma optical emission spectroscopy (ICP OES) is proposed. Concentrated or diluted acids mixtures (HNO₃, HF, HBF₄, and H₃BO₃) combined or not with H₂O₂ were systematically evaluated in order to achieve the best digestion procedure for masses of around 150 mg of samples. Principal component analysis (PCA) was applied in order to choose the best acid mixture for digestion (3 mL HNO₃ + 1 mL HBF₄ + 2 mL H₂O). The determined concentrations were in accordance with certified values of CRM 029 at the 95% confidence level, according to the Student-t test. This acid mixture was successfully applied for the digestion of four organic soil amendment samples (organic fertilizers, substrates, and soil conditioners) and element determination.     

Predicting Initial Tall Fescue Root Growth Response to Calcium/Aluminum Solution Concentrations

A study was conducted to quantify effects of soluble aluminum (Al) and gypsum (CaSO₄) on initial root growth of three varieties of tall fescue (Festuca arundinacea). Experiments were performed in a growth chamber using hydroponic solutions containing Al from 0 to74 µM in combination with CaSO₄ at 0 to10 mM. Seedlings were grown for 7 d, harvested, air dried, scanned, and weighed for treatment comparisons. Significant differences in root length existed between varieties in Al‐only solutions at low Al concentrations. All varieties showed reduced root growth at concentrations greater than 37 µM Al. Increased calcium (Ca²⁺) and sulfate (SO₄ ^2?) at given concentrations of Al resulted in greater root growth. Relative root growth increased approximately 30% to >80% at 37 µM Al as CaSO₄ increased from 2.5 to 10 mM. A simple logistic model adequately described the effects of Al and CaSO₄ on root growth (r² = 0.86, 0.95, and 0.96 for the three varieties).     

The Use of Goosegrass (Eleusine indica) to Remediate Soil Contaminated with Petroleum

A greenhouse experiment was performed to evaluate effectiveness of goosegrass (Eleusine indica) in phytoremediation of soil contaminated with 8,247 mg kg^?1 of total petroleum hydrocarbons (TPH). We determined seed germination toxicity, soil microbial viable counts, catalase activity, dehydrogenase activity (DHA), and the concentrations of TPH and 14 polycyclic aromatic hydrocarbons (PAHs) in soil and plant tissue. After 5 months, the initial level of contamination was reduced by 47% in planted soil, whereas it was only reduced by 11% in nonplanted soil. Bacterial numbers were 72 times greater in the rhizosphere treated soil than in the unvegetated treatment at the end of the study. There was no correlation between microbial counts or DHA and catalase activity, and the correlation between microbial counts and DHA was weak. Significant chemical reduction of H₂O₂, caused by the soil fabric, was observed in the determination of catalase activity. In case of vegetated treatment, 32% of PAHs was removed, but only 5% of PAHs was dissipated in the unvegetated pots. Gas chromatography/mass spectrometry analysis of plant tissue indicated that a low amount of PAHs (25.50 mg kg^?1 dry biomass) was detected in goosegrass roots growing in the contaminated soil, and no uptake into the shoots was occurring.     

Effect of Organic Ligands on Copper(II) Removal from Metal Plating Wastewater by Orange Peel-based Biosorbents

A neutrophilic, autotrophic bacterium that couples iron oxidation to nitrate reduction (iron-oxidizing bacteria [IOB]) under anoxic conditions was isolated from a working bioremediation site in Trail, British Columbia. The site was designed and developed primarily to treat high concentrations of Zn and As that originate from capped industrial landfill sites. The system consisted of two upflow biochemical reactor cells (BCR) followed by three vegetated wetland polishing cells with sub-surface flow and a holding pond. During a 5-year period (2003–2007), the system treated more than 19,100 m³ of contaminated water, removing and sequestering more than 10,700 kg of As, Zn and sulfate at average input water concentrations of: As, 58.6 mg?l^?1 (±39.9 mg?l^?1); Zn, 51.9 mg?l^?1 (±35.4 mg?l^?1) and SO₄ ^2?, 781.5 mg?l^?1 (±287.8 mg?l^?1). The bacterium was isolated in order to better understand the mechanisms underlying the consistent As removal that took place in the system. Analysis using Basic Local Alignment Search Tool (BLAST) database showed that the closest homologies are to Candidatus accumulibacterphosphatis (95 % homology), Dechloromonas aromatica (94 %), and Sideroxydans lithotrophicus ES-1 (92 %) Within the BCR cells, the IOB oxidized Fe²⁺ generated by iron-reducing bacteria (IRB); the source of the iron was most likely biosolids and coatings of iron oxide on locally available sand used in the matrix. We have provisionally designated the novel bacterium as TR1.