Biodegradation of Hexachlorocyclohexane by two species of Bacillus isolated from contaminated soil

Biodegradation of α, β, γ and δ hexachlorocyclohexane (HCH) isomers was studied in broth medium and soil microcosm by Bacillus circulans and Bacillus brevis isolated from contaminated soil. Degradation of α and γ isomers by both the bacterial isolates was higher than thermodynamically stable β and δ isomers. However, B. circulans was found more effective than B. brevis for β and δ isomers. Maximum rate of degradation was recorded at 150 mg/L followed by 100 and 50 mg/L. Soil microcosm study revealed maximum degradation of HCH isomers in the treatment containing natural soil, pesticide and bacterial inocula than the treatment having sterilised soil, pesticide and bacterial isolates. Chloride release was positively co-related with HCH degradation in broth medium as well as in soil microcosm, suggesting that B. circulans and B. brevis hold promising potential by having efficient enzyme(s) required for dechlorination of HCH from contaminated sites.     

Phytoaccumulation prospects of cadmium and zinc by mycorrhizal plant species growing in industrially polluted soils

The natural vegetation growing along a wastewater channel was subjected to analyze the uptake of Cadmium (Cd) and Zinc (Zn) and their subsequent accumulation in aboveground and underground plant parts. Species which were mycorrhizal and growing in soils receiving industrially contaminated wastewater were collected along with their rhizospheric soil samples. The nearby uncontaminated control (reference) area was also subjected to sampling on similar pattern for comparison. Both Cd and Zn concentrations were significantly higher in soils of the study area as compared to the reference site. Five plant species i.e. Desmostachya bipinnata, Dichanthium annulatum, Malvastrum coromandelianum, Saccharum bengalense, and Trifolium alexandrinum were analyzed for metal uptake. The maximum phytoaccumulation of Cd was observed in Desmostachya bipinnata (20.41 μg g⁻¹) and Dichanthium annulatum (15.22 μg g⁻¹) for shoot and root tissues, respectively. However, Malvastrum coromandelianum revealed maximum Zn accumulation for both the shoot and the root tissues (134 and 140 μg g⁻¹, respectively). The examination of cleared and stained roots of the plants from both the areas studied revealed that all of them were colonized to a lesser or a greater degree by arbuscular mycorrhizal (AM) fungi. The Cd hyperaccumulating grasses i.e. Desmostachya bipinnata and Dichanthium annulatum, from study area had smaller root:shoot (R/S) ratio as compared to those growing on reference area indicating a negative pressure of soil metal contamination. The lower R/S ratio in the mycorrhizal roots observed was probably due to increased AM infection and its mediatory role in soil plant transfer of heavy metals. Furthermore, comparatively lower soil pH values in the study areas may have played a key role in making the overall phytoavailability of both the metals. Consequently variations in Cd and Zn tissue concentration among species were observed that also indicate the phytoaccumulation potential of the native species.     

Phosphate-induced differences in stabilization efficiency for soils contaminated with lead,zinc, and cadmium

Phosphates can cost-effectively decrease the mobility of Pb in contaminated soils. However, Pb always coexists with other metals in soil, their competitive reactions with phosphates have not been tested. In this study, the abilities of KH₂PO₄, K₂HPO₄, and K₃PO₄ to stabilize Pb, Zn, and Cd in soils contaminated with a single metal or a ternary metal for different phosphorus/metal molar ratios were investigated. Results indicated that the stabilization efficiency of KH₂PO₄, K₂HPO₄, and K₃PO₄ for Pb, Zn, and Cd in single metal contaminated soil (P/M ratio 0.6) was 96.00%–98.74%, 33.76%–47.81%, and 9.50%–55.79%, respectively. Competitive stabilization occurred in the ternary system, Pb exhibited a strong competition, the stabilization efficiency of Zn and Cd reduced by 23.50%–31.64%, and 7.10%–39.26%, respectively. Pyromorphite and amorphous lead phosphate formed with excess KH₂PO₄ or K₂HPO₄ addition, while K₃PO₄ resulted in the formation of a hydroxypyromorphite precipitate. Amorphous Zn and Cd phosphates and hydroxides were the primary products. The immobilization rate of Zn and Cd depends on pH, and increased significantly in response to the excess phosphate application. This approach provides insight into phosphate-induced differences in stabilization efficiency in soils contaminated with multiple metals, which is of theoretical and engineering significance.

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Sulphur-oxidising bacteria isolated from deep caves improve the removal of arsenic from contaminated harbour sediments

Acidophilic S-oxidising bacteria isolated from sulphur-rich deep caves (Frasassi, Italy), characterised by relatively low temperature, were tested for their ability to mobilise (semi-)metals from contaminated sediments. Sediment samples from two commercial Italian seaports were used to set up bioleaching experiments. The effect of different growth substrates was also investigated. Our experiments revealed that S-oxidising bacteria isolated from Frasassi caves have a high potential to remove As from contaminated marine sediments, as never reported before. Although As solubilisation efficiency was quite low (i.e. about 30%), only a small amount of As was associated with non-residual fractions of the sediment. On the contrary, the solubilisation efficiencies of Zn and Ni (20% and 10%, respectively) were lower than those previously obtained by the use of other acidophilic bacteria and mainly influenced by the experimental conditions rather than by the presence of the S-oxidising bacteria. Results presented here open new perspectives in bioleaching applications for the remediation of contaminated sediments. Indeed, microbial strains adapted to relatively low-temperature environments could improve sediment bioleaching at temperature regimes where mesophilic and thermophilic strains are not favoured. Such strains could be exploited for developing selective bioremediation procedures for sediments contaminated with As, to be applied in multistep biotreatment processes.     

Uptake of zinc, cadmium and phosphorus by arbuscular mycorrhizal maize (Zea mays L.) from a low available phosphorus calcareous soil spiked with zinc and cadmium

In a multifactorial pot experiment, maize (Zea mays L.) with or without inoculation with the arbuscular mycorrhizal (AM) fungus Glomus mosseae BEG167 was grown in a sterilized soil spiked with three levels of zinc (0, 300 and 900 mg Zn kg⁻¹ soil) and three levels of cadmium (0, 25 and 100 mg Cd kg⁻¹ soil). At harvest after 8 weeks of growth, the proportion of root length of inoculated plants colonized decreased with increasing Zn or Cd additon, and was 56% in the absence of both metals and was reduced significantly to 27% in the presence of the higher levels of both metals. Mycorrhizal plants had higher biomass than non-mycorrhizal controls except at the highest soil level of Cd. Cadmium had more pronounced effects on plant biomass than did Zn at the levels studied and the two metals showed a significant interaction. The data suggest that mycorrhizal inoculation increased plant growth with enchancement of P nutrition, perhaps increasing plant tolerance to Zn and Cd by a dilution effect. AM inoculation also led to higher soil solution pH after harvest, possibly reducing the availability of the metals for plant uptake, and lowered the concentrations of soluble Zn and Cd in the soil solution, perhaps by adsorption onto the extrametrical mycelium.     

Biodegradation of paclobutrazol by a microbial consortium isolated from industrially contaminated sediment

Biodegradability of the plant growth retardant paclobutrazol by a microbial consortium in which Pseudomonas was the predominant strain was investigated in batch culture. The consortium which had been isolated from an industrially contaminated sediment was proven to be useful for the treatment of effluents containing paclobutrazol. Paclobutrazol was degraded by the pure isolated strain of Pseudomonas sp. as well as the microbial consortium. Paclobutrazol was utilized as the sole source of carbon and energy. Sixty percent of the paclobutrazol was degraded by the microbial consortium from an initial concentration of 54 mg L^?1 within 48 h and more than 98% of an initial concentration of 3.4 mg L^?1 was degraded within 36 h. The optimum temperature and pH were determined to be 30°C and 7.0, respectively. A pure strain of a bacterium, isolated from the enrichment culture was identified as Pseudomonas sp. The microbial consortium was tolerant of high pH and could degrade paclobutrazol faster than the pure strain. The degradation rate of this plant growth regulator in an aerobic environment was greater than that under anaerobic conditions.     

Accumulation of cadmium from contaminated water and sediment by the shrimp Callianassa australiensis

The burrowing marine shrimp Callianassa australiensis (Dana) was collected from an uncontaminated area in Western Port, Victoria, Australia in 1977. The shrimp were exposed to cadmium-contaminated water and sediment for 8 wk. The concentrations ranged from 0.5 to 63 g Cd 1^-1 for water and 0.5 to 63 g Cd g^-1 for sediment. The shrimp accumulated cadmium from water at a rate commensurate with increases in the concentration of cadmium in water and the duration of the experiment. Although the cadmium concentration in the sediments was 10³ times higher than that in water, it hat no effect on cadmium uptake by the shrimp. The concentration factors decreased with increasing concentration of cadmium in water but increased as the duration of exposure increased. The shrimp dry weight decreased with increasing concentration of cadmium in water and duration of exposure. As was the case with cadmium uptake by the shrimp, these two factors acted interactively on the shrimp dry weight, but the third factor, concentration of cadmium in sediment, had no effect.     

Biosorption of copper, zinc, cadmium and nickel by Chlorella vulgaris

The sorption capacity of the microalga, Chlorella vulgaris, was investigated using different metals (Cu, Zn, Cd and Ni), in both monometallic and bimetallic solutions. The final metal concentrations were significantly low. In the case of copper, an acid pretreatment (at pH 3) of the biomass was required to avoid an excessive increase in pH and the subsequent precipitation of metal during tests. This pretreatment was not necessary for the rest of the metals. The study of the influence of pH led to a greater metal uptake at a higher pH, suggesting a clear competition between metal cations and protons during the biosorption process. The biomass concentration was also a relevant variable, and the best sorption capacities were achieved at the lowest biomass concentration. pH also had a great influence on the elution of the metal retained by the biomass. The best recovery yields were obtained for the lower pH of the eluent solution. Sorption isotherms were well fitted to the Langmuir model, for both single-metal and two-metal systems. In both cases, the biomass showed a greater affinity for Cd.     

Preparation,characterization, and kinetics of nanoscale iron in nitrate nitrogen removal from polluted water

The aim of this study was to examine the production of nanoscale ions via the liquid phase reduction method and the effectiveness of the removal of nitrate nitrogen (NO₃^?–N) as well as measure the products and kinetics of the reactions. The nanoparticles obtained were approximately 50 nm in diameter and the main component was iron (Fe). This custom-made nanoscale Fe was highly positively charged, and reacted rapidly with NO₃^?–N in oxygen-free and neutral conditions at room temperature. A 90% removal rate was achieved when the reaction occurred for 30 min in simulation sample water with vigorous shaking at 250 r/min at NO₃^?–N concentrations of 30, 50, 80 or120 mg N/L. The nanometer Fe dosage was maintained throughout the experiment at 4 g/L. A first-order kinetics equation was applied to the obtained experimental data which followed a pseudo first-order reaction. Data demonstrated that the removal of nitrate nitrogen from polluted groundwater using a nanoscale Fe iron was effective and rapid.     

滇白前(Silene viscidula)对铅、锌、镉的共超富集特征

为了寻找新的重金属超富集植物特别是多金属共超富集植物,调查测定了云南兰坪铅锌矿区北厂矿段生长的8种植物及其根区土壤的重金属质量分数,以及土壤基本理化性质.结果表明:研究区土壤中磷和钾质量分数较低,总氮、总磷、总钾、铵态氮、硝态氮、速效磷分别占土壤干质量的0.2%、0.03%、0.52%、0.0029%、0.000 12%、0.00068%;有机质质量分数平均为4.81%,pH值平均为6.79,电导率变化范围为11.4～140-3μs·cm-1.该矿区土壤中锌(Zn)、铅(Pb)、镉(Cd)、铜(Cu)的质量分数平均值分别为(38 178±23 870)、(18 671±10 143)、(438±345)、(159±:82)mg·kg>-1,除Cu外均超过国家土壤环境质量(GB 15618-1995)三级标准.8种植物地上部Zn、Pb、Cd、Cu质量分数范围分别为271～17 986、51～5 430、1～617、2～26mg·kg-1,尤以滇白前(Silene viscidula Franch)地上部Zn、Pb、Cd质量分数为最高.进一步采集38个滇白前样本对其重金属富集特征进行深人调查,表明其地上部中含zn、Pb和Cd平均为(11 043±3 537)、(1 546±1 044)和(391±196)mg·kg-1,富集系数(地上部和土壤金属质量分数之比)分别为0.35、0.08和1.05,转运系数(地上部和根中金属质量分数之比)均超过1,均值分别为8.21、3.90和8.36.野外调查数据表明,滇白前是一种Pb/Zn/Cd共超富集植物.滇白前对Zn、Pb富集系数小于1,主要是由于其对应土壤中Zn、Pb质量分数太高(平均分别为(45 778±32 819)、(22 512±13 613)mg·kg-1)所致.     

Characterization of two metal resistant Bacillus strains isolated from slag disposal site at Burnpur, India

Two strains of Bacillus sp. resistant to arsenate and lead designated as AsSP9 and PbSP6, respectively were isolated from the slag disposal site. They were identified to be related to Bacillus cereus cluster on the basis of 16S rDNA based sequence analysis and phenotypic characteristics. Both were rod-shaped (AsSP9, 2-5 microm and PbSP6, 2-4 microm), aerobic, salt tolerant (2-8% NaCI), endospore forming bacteria with minor differences like the AsSP9 showed sporangial bulging and PbSP6 had positive lipase activity. The temperature range for their growth was 20-40 degrees C and pH range 6.0-9.0 with an optimum temperature of 37 degrees C and pH of 7 for both strains. The principal nitrogen sources forAsSP9 and PbSP6 were DL-Tryptophan and L-Phenylalanine, respectively. The suitable carbon source forAsSP9 was lactose and for PbSP6 sucrose. The heavy metal accumulation efficiency was found to be 0.0047 mg g(-1) of dry mass forAsSP9 and 0.686 mg g(-1) of dry mass for PbSP6.     

Influence of cadmium on the growth of Agrocybe perfecta and two Pleurotus spp and translocation from polluted substrate and soil to fruitbodies

The presence of Cd in substrate (wheat straw) strongly depressed the growth and mineralization of substrate by Agrocybe perfecta. Pleurolus ostreatoroseus was only slightly depressed and Pleurotus sp. CCB 068 increased degradation by the two highest Cd concentration. Mineralization rate of fungal substrate were increased by indigenous soil flora. However increase in Cd concentrations added to the soil depressed mineralisation of organic matter. Cadmium also affected the fruitbody yield and only Pleurotus sp. was able to fructify in high Cd concentrations. Translocation and accumulation of Cd in fruitbodies increased with the increase of Cd concentrations in substrate.     

铅、镉污染废水树皮类吸附材料的筛选

近年来,水体重金属污染日趋严重,筛选出绿色高效处理重金属污染废水的吸附材料迫在眉睫.本文采用振荡吸附法研究了10种树皮类生物质吸附材料在不同投加量、初始浓度、pH和吸附时间下对模拟污染废水中Pb~(2+)和Cd~(2+)的吸附效率.结果表明,在25℃和180 r·min~(-1)恒温振荡条件下,10种树皮对Pb~(2+)和Cd~(2+)的吸附效率存在明显差异(P0.05).它们对模拟废水Pb~(2+)和Cd~(2+)的吸附量和吸附率,分别随初始浓度的增加呈递增和递减趋势;在0—120 min内随吸附时间的延长而提高;在pH 2.0—4.0范围内,随pH的增大而明显提升.红外光谱分析表明,羟基和羧基参与了Pb~(2+)和Cd~(2+)吸附.在投加量0.5 g·L~(-1)、模拟废水初始浓度50 mg·g~(-1)、pH 5.50和吸附时间120 min条件下,侧柏(Platycladus orientalis)皮、核桃树(Juglans regia)皮和构树(Broussonetia papyrifera)皮对Pb~(2+)的吸附量可达71.77—83.61 mg·g~(-1),对Cd~(2+)的吸附量达到64.69—70.33 mg·g~(-1),对实际污染废水具有较高的吸附率,最高可达98.21%.因此,侧柏皮、核桃树皮和构树皮可能是是吸附复合污染废水中铅镉的潜在材料.     

微胶囊EDTA对2种土壤中铅释放的影响

选用不同铅污染程度及pH值的土壤,采用连续批浸提实验和土柱淋溶实验,比较研究微胶囊EDTA（Cap-EDTA）和未微胶囊化EDTA（Ncap-EDTA）对不同土壤溶液中pH值和铅离子浓度动态变化影响,以及土壤渗滤液中铅离子淋失特征。结果表明：施加2种不同形式的EDTA,可极显著地增加土壤溶液中铅离子浓度,Cap-EDTA能控制土壤溶液中铅浓度的突增幅度,且使土壤溶液中的铅持续保持在适度浓度的时间更长。同一种土壤不同处理间土壤pH值的变化趋势基本一致,无显著差异。施用2种不同形式EDTA可极显著地增加土壤渗滤液中铅离子含量,土壤铅累积淋失量呈对数曲线上升,但施用Cap-EDTA处理能显著降低土壤中铅的初始淋失量和淋失总量。在相同浓度及形式的EDTA下,高铅浓度和高pH值的土壤铅更易活化和淋失。因此,在进行污染土壤植物修复的EDTA调控时,采用微胶囊化EDTA,能降低其带来的污染地下水风险。     

Distribution,removal and chemical forms of heavy metals in polluted rice seed

In this paper, the distribution, removal and binding forms of heavy metals in polluted seeds of rice were studied using the methods of histochemistry and biochemistry. The results indicate that the distribution of heavy metals in rice grains was very uneven. The heavy metals in rice grains chiefly exist in association with the parts of high protein. Separation of proteins by Sephadex chromatography and subsequent analysis by atomic absorption spectroscopy revealed that Cd, Pb and As were mainly bound to protein of 54.5 and 5.50 kD molecular weights. During the rice processing, the concentrations of heavy metals in the edible rice decrease greatly, for some heavy metals in these parts of chaff, coarse rice bran and fine rice bran were removed.     

Spatial health risk assessment and hierarchical risk management for mercury in soils from a typical contaminated site,China

Due to rapid urbanization and the implementation of ecological civilization construction in China, many industrial factories have been closed or relocated. Therefore, numbers of contaminated sites were generated with contaminated soils which may pose a risk to receptors living nearby. This study presented a spatial health risk assessment and hierarchical risk management policy making for mercury (Hg) in soils from a typical contaminated site in the Hunan Province, central China. Compared with the second class value (0.3 mg/kg) of the Chinese Environmental Quality Standard for Soils, the mean concentrations of Hg in the three soil depths exceeded the second class value. The non-carcinogenic risk of Hg probably posed adverse health effects in 41, 30 and 36 % of the surface soil, the moderate soil and subsoil, respectively, under a sensitive land scenario. The non-carcinogenic risk temporarily posed no adverse health effects in most areas under an insensitive land scenario except for the area around sampling site S29. Spatially, the central, southwest and northeast parts of the contaminated land under a sensitive land scenario should be regarded as the priority regions. For non-carcinogenic effects, the exposure pathways that resulted in the higher levels of exposure risk were ingestion and inhalation of vapors, followed by dermal contact and inhalation of particles. A risk-based integrated risk management policy including the hierarchical risk control values for different soil depths and the calculated remediation earthwork was proposed with consideration of the cost-benefit effect for the related decision-makers.     

Application of electrochemical reactor divided by cellulosic membrane for optimized simultaneous removal of phenols,chromium, and ammonia from tannery effluents

The post treatment of simulated tannery wastewater was evaluated in an electrochemical oxidation process under galvanostatic conditions. A continuous flow reactor divided by a cellulosic membrane consisted of Ti/SnO₂–Sb anodes and iron cathodes was used. Central composite design and response surface methodology (RSM) were applied to investigate the effects of six operational parameters, namely initial concentration of total phenols (TPh), total chromium (TCr), total ammonia nitrogen (TAN), flow rate (Q), current intensity (I), and electrode surface area (A). Effectiveness of the innovative cellulosic membrane was proven by considerable pH variations in the anolyte and catholyte chambers. A faster removal rate was observed for TPh and TAN, followed by TCr. The treatment level was very sensitive to Q and I in the studied ranges. RSM showed the removal efficiencies of 78.14%, 63.42%, and 86.09% for TPh, TCr, and TAN, respectively, are achieved under optimal conditions with consumption of only 9.03 kWh m^?3 electrical energy. Chlorinated compounds such as chloroform, 2,4-dichlorophenol, and chlorobenzene were detected as the degradation intermediates. According to the obtained results, electrolysis in the divided cell with cellulosic membrane is a practical, cost-effective method for advanced treatment of tannery effluents.     

Biosorption of Cu (II) ions by indigenous copper-resistant bacteria isolated from polluted coastal environment

The concentrations of copper in water and sediment samples of Cuddalore coastal area, Tamil Nadu, India were examined. The isolation, characterization, screening, and metal sorption capabilities of copper-resistant bacteria (CURB) also were investigated. Biosorption capabilities and growth time varied among the resistant isolates. All isolates reduced more than 80% of copper from copper-treated broth. However, Bacillus cereus CURB-4 strain absorbed more copper ions (99.9%) than other resistant isolates. Changes in structural group position and synthesis of extracellular polysaccharides (EPS) of CURB-4 strain under copper stress and controlled conditions also were examined. Under copper stress condition, CURB-4 produced more EPS (71 ± 0.6%) compared to control conditions (66 ± 0.4%). Fourier transform infrared spectroscopy revealed that the changes in functional group position of EPS were observed in stressed condition. Overall, synthesis of EPS in bacteria is a protective barrier against environmental stress.     

High zinc removal from water and soil using struvite-supported diatomite obtained by nitrogen and phosphate recovery from wastewater

Zinc is known as an essential element of human life. However, excessive zinc discharge into water and soil causes water pollution, leading to serious health issues such as septicemia, meningitis and iron-deficiency anemia. Here, a novel material made of struvite-supported diatomite was obtained from eutrophic water treated by mesoporous MgO-modified diatomite. This material was applied for zinc remediation in aqueous solutions and contaminated soils to test the reuse of P-containing products. Struvite-supported diatomite was characterized by field emission scanning electron microscopy and X-ray diffraction. Results show that the maximum removal efficiency of Zn(II) from wastewater streams reached 90.54% at an initial pH of 5 and struvite-supported diatomite dosage of 0.3 g/L. Moreover, the X-ray diffraction patterns of precipitates after Zn(II) sorption show that the combination between zinc and the phosphate group played a key role for zinc removal in solution. For Zn-contaminated soils amended with 10% struvite-supported diatomite, available Zn decreased by 65.38% and acid soluble Zn decreased by 56.9% after 56 days.     

Urinary cadmium concentrations in a population downstream: from a zinc mining area in Mae Sot District, Tak Province, Thailand

Urinary cadmium (UCd) is a good indicator of long-term exposure to cadmium. UCd concentrations resulting from juvenile cadmium exposure in 3 sub-districts of Tak Province, Thailand, were investigated. The target population was divided by gender and into 2 age subgroups: 9–12 and 13–15 years. A total of 748 urine samples were collected and analyzed by spectrophotometer. All samples had UCd of more than 1.0 μg/g creatinine (Cr). Total UCd means among the 3 sub-districts were 1.31, 1.01, and 0.87 μg/g Cr; the Thai population mean is 0.5 μg/g. The difference among the three sub-districts was statistically significant (p < 0.05). Total means for UCd were 1.13 μg/g Cr for boys, 1.00 for girls, 1.01 μg/g Cr for those 9–12 years old, and 1.18 for those 13–15. UCd concentrations were not significantly different between genders and age groups. Likely dietary sources of cadmium exposure for the subject population were surveyed.