Phytoremediation of soils contaminated with phenanthrene and cadmium by growing willow (Salix × Aureo-Pendula CL 'j1011')

To assess the phytoremediation potential of an autochthonous willow (Salix × aureo-pendula CL 'J1011') for phenanthrene (PHE)-contaminated soils and PHE-cadmium (PHE-Cd) co-contaminated soils, we conducted field experiments in the lower reaches of the Yangtze River, China. Ethylenediaminetetraacetic acid (EDTA) and ethyl lactate were tested for individual and combined effects on the phytoremediation efficiency. For PHE-contaminated soils, willow plus ethyl lactate resulted in significant removal of PHE from soils after 45 days, and the PHE concentration in the shoots was significantly higher with than without ethyl lactate. For PHE-Cd co-contaminated soils, both willow plus EDTA and willow plus EDTA and ethyl lactate led to a significant decrease in the concentrations of PHE and Cd in the soils after 45 days, whereas willow alone did not. The PHE and Cd concentrations in the willow shoots were significantly enhanced in the presence of EDTA alone and with ethyl lactate, except for the PHE concentration in stems with EDTA alone. Under the same treatment, the presence of Cd had no significant influence on the PHE removal from soils. The results indicate the feasibility of using this willow together with both EDTA and ethyl lactate for the simultaneous removal of PHE and Cd from soils.     

Uptake and Bioaccumulation of Pentachlorophenol by Emergent Wetland Plant Phragmites australis (Common Reed) in Cadmium Co-contaminated Soil

Despite many studies on phytoremediation of soils contaminated with either heavy metals or organics, little information is available on the effectiveness of phytoremediation of co-occurring metal and organic pollutants especially by using wetland species. Phragmites australis is a common wetland plant and its potential for phytoremediation of cadmium pentachlorophenol (Cd-PCP) co-contaminated soil was investigated. A greenhouse study was executed to elucidate the effects of Cd (0, 10, and 20 mg kg^?1) without or with PCP (0, 50, and 250 mg kg^?1) on the growth of the wetland plant P. australis and its uptake, accumulation and removal of pollutant from soils. After 75 days, plant biomass was significantly influenced by interaction of Cd and PCP and the effect of Cd on plant growth being stronger than that of PCP. Coexistence of PCP at low level lessened Cd toxicity to plants, resulting in improved plant growth and increased Cd accumulation in plant tissues. The dissipation of PCP in soils was significantly influenced by interactions of Cd, PCP and plant presence or absence. As an evaluation of soil biological activities after remediation soil enzyme was measured.     

Phytoremediation Efficiency of a PCP-Contaminated Soil using Four Plant Species as Mono- and Mixed Cultures

Bioremediation of soil polluted by pentachlorophenol (PCP) is of great importance due to the persistence and carcinogenic properties of PCP. Phytoremediation has long been recognized as a promising approach for removal of PCP from soil. The present study was conducted to investigate the capability of four plant species; white clover, ryegrass, alfalfa, and rapeseed grown alone and in combination to remediate pentachlorophenol contaminated soil. After 60 days cultivation, white clover, raygrass, alfalfa, and rapeseed all significantly enhanced the degradation of PCP in soils. Alfalfa showed highest efficiency for the removal of PCP in single cropping flowed by rapeseed and ryegrass. Mixed cropping significantly enhanced the remediation efficiencies as compared to single cropping; about 89.84% of PCP was removed by mixed cropping of rapeseed and alfalfa, and 72.01% of PCP by mixed cropping of rape and white clover. Mixed cropping of rapeseed with alfalfa was however far better for the remediation of soil PCP than single cropping. An evaluation of soil biological activities as a monitoring mechanism for the bioremediation process of a PCP-contaminated soil was made using measurements of microbial counts and dehydrogenase activity.     

Variation in the uptake of Arsenic, Cadmium, Lead, and Zinc by different species of willows Salix spp. grown in contaminated soils

The experiment assessed the variability of in seven clones of willow plants of high biomass production (Salix smithiana S-218, Salix smithiana S-150, Salix viminalis S-519, Salix alba S-464, Salix ’Pyramidalis’ S-141, Salix dasyclados S-406, Salix rubens S-391). They were planted in a pots for three vegetation periods in three soils differing in the total content of risk elements. Comparing the calculated relative decrease of total metal contents in soils, the phytoextraction potential of willows was obtained for cadmium (Cd) and zinc (Zn), moderately contaminated Cambisol and uncontaminated Chernozem, where aboveground biomass removed about 30% Cd and 5% Zn of the total element content, respectively. The clones showed variability in removing Cd and Zn, depending on soil type and contamination level: S. smithiana (S-150) and S. rubens (S-391) demonstrated the highest phytoextraction effect for Cd and Zn. For lead (Pb) and arsenic (As), the ability to accumulate the aboveground biomass of willows was found to be negligible in both soils. The results confirmed that willow plants show promising results for several elements, mainly for mobile ones like cadmium and zinc in moderate levels of contamination. The differences in accumulation among the clones seemed to be affected more by the properties of clones, not by the soil element concentrations or soil properties. However, confirmation and verification of the results in field conditions as well as more detailed investigation of the mechanisms of cadmium uptake in rhizosphere of willow plants will be determined by further research.     

Enhanced Remediation of Pentachlorophenol (PCP)-Contaminated Groundwater by Bioaugmentation with Known PCP-Degrading Bacteria

The objective of this study was to test whether bioaugmentation with known pentachlorophenol (PCP)-degrading bacteria (Sphingobium chlorophenolicum and Burkholderia cepacia) could enhance remediation of PCP-contaminated groundwater. Groundwater PCP concentrations were determined by US Environmental Protection Agency (EPA) method 3510C and gas chromatography. Gene expression for PCP-degrading enzymes: pentachlorophenol 4-monooxygenase (pcpB; S. chlorophenolicum) and chlorophenol 4-monooxygenase (TftD; B. cepacia) was determined by real-time polymerase chain reaction (RT-PCR) using gene-specific primers. Bioaugmented treatments with S. chlorophenolicum and B. cepacia showed 32% and 49% decrease (p < .05) whereas un-bioaugmented (indigenous) treatment did not show significant decrease (p > .05) in average PCP concentration, respectively, over 72 days. Decreased PCP levels correlated strongly (r = ?.82, p < .05) with increased PCP-tolerant bacteria in bioaugmented treatments, whereas no significant correlation was observed (r = ?.22, p > .05) in un-bioaugmented treatment. In addition, a decrease in PCP levels also correlated significantly with an increase in gene expression of PCP-degrading enzymes, pcpB (r = ?.77044) and TftD (r = ?.87905) (p < .05). PCP concentrations decreased and pcpB or TftD expressions were higher in bioaugmented treatments with S. chlorophenolicum (50%, 7-fold) or B. cepacia (67%, 10.7-fold), respectively, than indigenous treatment. Therefore, bioaugmentation with known PCP-degrading bacteria enhanced remediation of PCP-contaminated groundwater than indigenous bacteria alone. Results of this study may provide a more efficient and environmentally friendly technique for on-site remediation of PCP-contaminated groundwater.     

The Effect of Mycorrhizal Fungi on the Fate of Aldrin: Phytoremediation Potential

The objective of this study was to investigate the phytoremediation potential of mycorrhizal systems for the remediation of aldrin-contaminated soils. Feltleaf willow (Salix alaxensis) and balsam poplar (Populus balsamifera) were grown in soil spiked with 0.8 mg/kg aldrin- (1,2,3,4,10-¹⁴C). Daconil₂₇₈₇® was employed to suppress indigenous mycorrhizal infection. After 100 days of greenhouse incubation, mycorrhizal infection in the fungicide-amended willows was found to be 2.5 fold lower than in controls. Mycorrhizal infection in the poplar systems was unaffected by fungicide addition. Mycorrhizae were correlated with radiolabel uptake in the willow systems (r = 0.79), and not as strongly in the poplar systems (r = 0.58). Most of the radiolabel in the root material was bound product regardless of mycorrhizal infection, but 12 to 21% was found to be extractable dieldrin. Aldrin was not detected in any vegetative matrix. Dieldrin constituted less than 1% of the radiolabel in the willow leaf material, accumulating to approximately 5 μg/kg. Dieldrin was not detected in the poplar leaves (MDL ≈ 1 μg/kg), although the poplars took up approximately the same amount of radiolabel as the willows. Water-soluble transformation products were formed in the vegetated soils (6 to 12%) and nonvegetated controls (1 to 2%).     

Phytoremediation of petroleum hydrocarbon-contaminated saline-alkali soil by wild ornamental Iridaceae species

As a green remediation technology, phytoremediation is becoming one of the most promising methods for treating petroleum hydrocarbons (PHCs)-contaminated soil. Pot culture experiments were conducted in this study to investigate phytoremediation potential of two representative Iridaceae species (Iris dichotoma Pall. and Iris lactea Pall.) in remediation of petroleum hydrocarbon-contaminated saline-alkali soil from the Dagang Oilfield in Tianjin, China. The results showed that I. lactea was more endurable to extremely high concentration of PHCs (about 40,000 mg/kg), with a relatively high degradation rate of 20.68%.The degradation rate of total petroleum hydrocarbons (TPHs) in soils contaminated with 10,000 and 20,000 mg/kg of PHCs was 30.79% and 19.36% by I. dichotoma, and 25.02% and 19.35% by I. lactea, respectively, which improved by 10–60% than the unplanted controls. The presence of I. dichotoma and I. lactea promoted degradation of PHCs fractions, among which saturates were more biodegradable than aromatics. Adaptive specialization was observed within the bacterial community. In conclusion, phytoremediation by I. dichotoma should be limited to soils contaminated with ≤20,000 mg/kg of PHCs, while I. lactea could be effectively applied to phytoremediation of contaminated soils by PHCs with at least 40,000 mg/kg.     

Remediation of Copper from Copper Mine Wastes and Contaminated Soils Using (S,S)-Ethylenediaminedisuccinic Acid and Acidophilic Bacteria

The biodegradable chelating agent (S,S)-Ehylenediaminedisuccinic acid (EDDS), autochthonous acidophilic bacteria, and a combination of the two means were investigated for the removal of pseudo-total and ethylenediaminetetraacetic acid (EDTA)-available content of Cu from surface layers of three soil categories in the Bor copper mining area. Their efficiencies were compared at mine overburden, flotation tailings, and agricultural land sites in order to determine the potential role of these approaches in the soil remediation process. The most effective removal of Cu was achieved on flotation tailings, where combined treatment showed significant reduction of pseudo-total and EDTA-available concentrations of Cu (40.5?±?27.3% and 99.6?±?0.2%, respectively). Acidophilic bacteria treatment showed high efficiency on flotation tailings, removing 94.1?±?1.2% of EDTA-available Cu. EDDS treatment showed discernible results in the removal of EDTA-available Cu from agricultural land soil (44.4?±?13.9%). In the case of overburden soil material, selected agents did not have statistically significant results in the removal of pseudo-total or EDTA-available fraction of Cu. Chosen remediation approaches showed diverse efficiency for soil categories on investigated sites. Combined approach showed synergistic results in the case of EDTA-available Cu removal from flotation tailings soils, suggesting that this combination deserves further attention as a potentially promising environmentally friendly remediation option.     

Response Surface Modeling for Co-Remediation of Cr6+ and Pentachlorophenol by Bacillus cereus RMLAU1: Bioreactor Trial and Structural and Functional Characterization by SEM-EDS and FT-IR Analyses

This is the first report on optimization of process variables for simultaneous bioremediation of pentachlorophenol (PCP) and Cr⁶⁺ employing traditional and response surface methodology (RSM). In a one-factor-at-a-time approach, the effect of PCP level exhibited maximum bacterial growth and Cr⁶⁺ (82%) and PCP (91.5%) removal at initial 100 mg PCP L^?1 with simultaneous presence of 200 mg Cr⁶⁺ L^?1 within a 36-h incubation. However, at varied Cr⁶⁺ concentrations, maximum growth and Cr⁶⁺ (97%) and higher PCP (59%) removal were achieved at 50 mg Cr⁶⁺ L^?1 with simultaneous presence of 500 mg PCP L^?1 within a 36-h incubation. The Box-Behnken design suggested 100% Cr⁶⁺ and 95% PCP remediation at 36 h under optimum conditions of 75?mg PCP and 160 mg Cr⁶⁺ L^?1, pH 7.0, and 35°C; Cr⁶⁺ removal was further enhanced to 97% in bioreactor trial. Fourier transform infrared (FT-IR) analysis revealed the likely involvement of hydroxyl, amide, and phosphate groups in Cr³⁺ binding. Scanning electron microscopy and energy-dispersive x-ray spectroscopy (SEM-EDS) showed biosorption of reduced chromium on bacterial cell surface. This isolate can be employed for eco-friendly and effective in situ bioremediation of Cr⁶⁺ and PCP simultaneously.     

Phytoextraction of Cd and Zn from agricultural soils by Salix ssp. and intercropping of Salix caprea and Arabidopsis halleri

Contamination of agricultural topsoils with Cd above guideline values is of concern in many countries throughout the world. Extraction of metals from contaminated soils using high-biomass, metal-accumulating Salix sp. has been proposed as a low-cost, gentle remediation strategy, but reasonable phytoextraction rates remain to be demonstrated. In an outdoor pot experiment we assessed the phytoextraction potential for Cd and Zn of four willow species (Salix caprea, S. fragilis, S. × smithiana, S. × dasyclados) and intercropping of S. caprea with the hyperaccumulator Arabidopsis halleri on three moderately contaminated, agricultural soils. Large concentrations of Cd (250 mg kg⁻¹) and Zn (3,300 mg kg⁻¹) were determined in leaves of Salix × smithiana grown on a soil containing 13.4 mg kg⁻¹ Cd and 955 mg kg⁻¹ Zn, resulting in bioaccumulation factors of 27 (Cd) and 3 (Zn). Total removal of up to 20% Cd and 5% Zn after three vegetation periods were shown for Salix × smithiana closely followed by S. caprea, S. fragilis and S. × dasyclados. While total Cd concentrations in soils were reduced by up to 20%, 1 M NH₄NO₃-extractable metal concentrations did not significantly decrease within 3 years. Intercropping of S. caprea and A. halleri partly increased total removal of Zn, but did not enhance total Cd extraction compared to single plantings of S. caprea after two vegetation periods.     

Shrub canopies influence soil temperatures but not nutrient dynamics: An experimental test of tundra snow–shrub interactions

Shrubs are the largest plant life form in tundra ecosystems; therefore, any changes in the abundance of shrubs will feedback to influence biodiversity, ecosystem function, and climate. The snow–shrub hypothesis asserts that shrub canopies trap snow and insulate soils in winter, increasing the rates of nutrient cycling to create a positive feedback to shrub expansion. However, previous work has not been able to separate the abiotic from the biotic influences of shrub canopies. We conducted a 3‐year factorial experiment to determine the influences of canopies on soil temperatures and nutrient cycling parameters by removing ~0.5 m high willow (Salix spp.) and birch (Betula glandulosa) shrubs, creating artificial shrub canopies and comparing these manipulations to nearby open tundra and shrub patches. Soil temperatures were 4–5°C warmer in January, and 2°C cooler in July under shrub cover. Natural shrub plots had 14–33 cm more snow in January than adjacent open tundra plots. Snow cover and soil temperatures were similar in the manipulated plots when compared with the respective unmanipulated treatments, indicating that shrub canopy cover was a dominant factor influencing the soil thermal regime. Conversely, we found no strong evidence of increased soil decomposition, CO₂ fluxes, or nitrate or ammonia adsorbtion under artificial shrub canopy treatments when compared with unmanipulated open tundra. Our results suggest that the abiotic influences of shrub canopy cover alone on nutrient dynamics are weaker than previously asserted.     

Enhanced phytoremediation of cadmium and/or benzo(a)pyrene contaminated soil by hyperaccumlator Solanum nigrum L.

The role of same amendment on phytoremediating different level contaminated soils is seldom known. Soil pot culture experiment was used to compare the strengthening roles of cysteine (CY), EDTA, salicylic acid (Sa), and Tween 80 (TW) on hyperaccumulator Solanum nigrum L. phytoremediating higher level of single cadmium (Cd) or Benzo(a)pyrene (BAP) and their co-contaminated soils. Results showed that the Cd capacities (ug pot^?1) in shoots of S. nigrum in the combined treatment T_{0.1EDTA+0.9CY} were the highest for the 5 and 15 mg kg^?1 Cd contaminated soils. When S. nigrum remediating co-contaminated soils with higher levels of Cd and BAP, that is, 5 mg kg^?1 Cd + 1 mg kg^?1 BAP and 15 mg kg^?1 Cd + 2 mg kg^?1 BAP, the treatment T_{0.9CY+0.9Sa+0.3TW} showed the best enhancing remediation role. This results were different with co-contaminated soil with 0.771 mg kg^?1 Cd + 0.024 mg kg^?1 BAP. These results may tell us that the combine used of CY, SA, and TW were more useful for the contaminated soils with higher level of Cd and/or BAP. In the combined treatments of Sa+TW, CY was better than EDTA.     

Screening of New Zealand Native White-Rot Isolates for PCP Degradation

From a pool of 367 white-rot fungi native to New Zealand (over 77 genera), isolates were screened for their bioremediation potential of pentachlorophenol (PCP). Fungi were tested for their ligninolytic activity (Poly R-478, 367 isolates; wood decay, 235 isolates), tolerance to temperature (261 isolates), resistance to PCP (253 isolates), and PCP degradation potential plus laccase expression (20 isolates). Of the isolates tested, 26% showed a discolouration in the polymeric dye assay, but all caused wood decay (5 to 169 mm) on willow cuttings. In the temperature tolerance tests, all isolates survived incubation from 0 to 30°C, however, 18% and 40% did not survive incubation at 35 and 40°C, respectively. In the PCP resistance tests, 23 isolates (9%) were able to grow on 200 mg/L PCP amended agar, of which 20 isolates were further studied for laccase expression and PCP degradation in vitro. All 20 isolates reduced (P < 0.05) PCP in the liquid fraction in the absence or presence of laccase and five of the isolates produced no detectable levels of PCP. None of the screening tests were predictive for PCP degradation in vitro. The requirements to build a database to select a superior white-rot fungal isolates for bioremediation is discussed.     

Earthworm-assisted bioremediation of petroleum hydrocarbon–contaminated soils from motorcar mechanic workshops in Ibadan,Oyo State,southwestern Nigeria

Enhanced microbial bioremediation of petroleum hydrocarbon–contaminated (PHC) soils with the earthworm Alma millisoni and the bacterium Bacillus spp. was conducted. The petroleum-contaminated topsoils (PCTS) (0–15 cm) collected from motorcar mechanic workshops were thoroughly mixed, sieved, and air dried for 7 days. The pH, water holding capacity (WHC), total nitrogen (N), organic carbon (OC), heavy metal (HM), and bacteriological analysis of the soil samples were evaluated. The indigenous bacterial isolates were subjected to 1%, 5%, and 50% of spent engine oil (SEO), incubated for 7 days at 37°C, and the isolate with the highest tolerance pattern was used for the remediation. Out of four indigenous bacteria isolated, Bacillus spp. had the highest tolerance to SEO. Preliminary exposure assessments of A. millisoni to PHC soils (100%, 60%, 50%, and 40% PHC) were carried out using 48-h avoidance response, coiling exhibition, swollen clitelium, 14-day survival tests, and antioxidant enzyme activities such as catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), and glutathione peroxidase (GPx). Subsequently, four treatments of 1 kg soil mixed with 100%, 75%, 50%, and 0% PCTS were designed and spiked with 20 g of dried cow dung. Each of the treatments consisted of four setups, viz., A. millisoni alone, A. millisoni and Bacillus spp., Bacillus spp. alone, and control. The bacterial counts, total petroleum hydrocarbon (TPH), total and bioavailable HM, and total OC and N of the soils were evaluated every 7 days for 35 days. Significant increases in the activities of CAT, SOD, GPx, and GST compared with control were recorded in A. millisoni exposed to the various treatments. Treatment with combined A. millisoni and Bacillus spp. resulted in significant (p < .05) reduction in TPH, reduction in total and bioavailable heavy metals, and increased total OC and N of the soil compared with other treatments. The percentage reduction in TPH and heavy metals with concomitant increase in total OC and total N recorded in the 50% PHC soils followed the order A. millisoni and Bacillus spp. > A. millisoni alone > Bacillus spp. alone. Hence, enhanced bioremediation using A. millisoni and Bacillus spp. may be a good biocatalyst in the remediation of petroleum hydrocarbon–contaminated soils.     

蚯蚓在植物修复芘污染土壤中的作用

采用盆栽试验法,研究了蚯蚓(Pheretima hupeiensis)在植物修复芘污染土壤中的作用。结果显示,试验浓度(20.24-321.42 mg/kg) 范围内,蚯蚓活动促进了芘污染土壤中修复植物黑麦草(Lolium multiforum)黑麦草的生长,其根冠比明显增大。添加蚯蚓72 d后,种植黑麦草的土壤中芘的去除率高达60.01%-86.26%,其平均去除率(74.66%)比无蚯蚓活动的土壤-植物系统(64.55%)提高10.11%,比无植物对照组(18.24%)提高56.42%。各种生物、非生物修复因子中,植物-微生物交互作用对芘去除的平均贡献率(51.75%)最为突出,比无蚯蚓活动时(44.94%)提高6.81%。说明蚯蚓活动可强化土壤-植物系统对土壤芘污染的修复作用。     

Methylation of Mercury in Earthworms and the Effect of Mercury on the Associated Bacterial Communities

Methylmercury compounds are very toxic for most organisms. Here, we investigated the potential of earthworms to methylate inorganic-Hg. We hypothesized that the anaerobic and nutrient-rich conditions in the digestive tracts of earthworm''s promote the methylation of Hg through the action of their gut bacteria. Earthworms were either grown in sterile soils treated with an inorganic (HgCl₂) or organic (CH₃HgCl) Hg source, or were left untreated. After 30 days of incubation, the total-Hg and methyl-Hg concentrations in the soils, earthworms, and their casts were analyzed. The impact of Hg on the bacterial community compositions in earthworms was also studied. Tissue concentrations of methyl-Hg in earthworms grown in soils treated with inorganic-Hg were about six times higher than in earthworms grown in soils without Hg. Concentrations of methyl-Hg in the soils and earthworm casts remained at significantly lower levels suggesting that Hg was mainly methylated in the earthworms. Bacterial communities in earthworms were mostly affected by methyl-Hg treatment. Terminal-restriction fragments (T-RFs) affiliated to Firmicutes were sensitive to inorganic and methyl-Hg, whereas T-RFs related to Betaproteobacteria were tolerant to the Hg treatments. Sulphate-reducing bacteria were detected in earthworms but not in soils.     

Biodegradation of pentachlorophenol in natural soil by inoculatedRhodococcus chlorophenolicus

Rhodococcus chlorophenolicus PCP-1, a mineralizer of polychlorinated phenols, was inoculated into natural sandy loam and peaty soils with pentachlorophenol (PCP) at concentrations usually found at lightly and heavily polluted industrial sites (30 to 600 mg PCP/kg). A single inoculum of 10⁵ to 10⁸ cells per g of peat soil and as little as 500 cells/g sandy soil initiated mineralization of¹⁴C-PCP. The mineralization rates of PCP were 130 to 250 mg mineralized per kg soil in 4 months in the heavily (600 mg/kg) polluted soils and 13 to 18 mg/kg in the lightly (30 mg/kg) polluted soils. There were no detectable PCP mineralizing organisms in the soils prior to inoculation, and also there was no significant adaptation of the indigenous microbial population to degrade PCP during 4 months observation in the uninoculated soils. The inoculum-induced mineralization continued for longer than 4 months after a single inoculation. Uninoculated, lightly polluted soils (30 mg PCP/kg) also showed loss of PCP, but some of this reappeared as pentachloroanisol and other organic chlorine compounds (EOX). Such products did not accumulate in theR. chlorophenolicus-inoculated soils, where instead EOX was mineralized 90 to 98%.R. chlorophenolicus mineralized PCP unhindered by the substrate competition offered by the PCP-methylating bacteria indigenously occurring in the soils or by simultaneously inoculated O-methylatingR. rhodochrous.     

Anaerobic biodegradation of pentachlorophenol in a contaminated soil inoculated with a methanogenic consortium or with Desulfitobacterium frappieri strain PCP-1

Anaerobic biodegradation of pentachlorophenol (PCP) in a contaminated soil from a wood-treating industrial site was studied in soil slurry microcosms inoculated with a PCP-degrading methanogenic consortium. When the microcosms containing 10%–40% (w/v) soil were inoculated with the consortium, more than 90% of the PCP was removed in less than 30 days at 29 °C. Less-chlorinated phenols, mainly 3-chlorophenol were slowly degraded and accumulated in the cultures. Addition of glucose and sodium formate to the microcosms was not necessary, suggesting that the organic compounds in the soil can sustain the dechlorinating activity. Inoculation of Desulfitobacterium frappieri strain PCP-1 along with a 3-chlorophenol-degrading consortium in the microcosms also resulted in the rapid dechlorination of PCP and the slow degradation of 3-chlorophenol. Competitive polymerase chain reaction experiments showed that PCP-1 was present at the same level throughout the 21-day biotreatment. D. frappieri, strain PCP-1, inoculated into the soil microcosms, was able to remove PCP from soil containing up to 200 mg PCP/kg soil. However, reinoculation of the strain was necessary to achieve more than 95% PCP removal with a concentration of 300 mg and 500 mg PCP/kg soil. These results demonstrate that D. frappieri strain PCP-1 can be used effectively to dechlorinate PCP to 3-chlorophenol in contaminated soils. Received: 14 November 1997 / Received revision: 29 January 1998 / Accepted: 24 February 1998     

Adsorption Evaluation of Herbicide Iodosulfuron Followed by Cedrus deodora Sawdust-Derived Activated Carbon Removal

The paucity of sorption studies of sulfonylurea herbicide Iodosulfuron has led to the current research for investigation of this imperative phenomena. Iodosulfuron adsorption capacity was evaluated through batch equilibrium experiments in six soil samples collected from distinct geographical regions of Pakistan. Activated carbon prepared from sawdust (Cedrus deodara) was investigated as an economical and sustainable adsorbent for the removal of Iodosulfuron from selected soils. Removal efficiency was studied as a function of contact time and pesticide concentration. Results exhibited a good adsorption capability of Iodosulfuron in different soils. Adsorption coefficient values ranged from 8.9 to 26 mL/g. Soil pH and organic matter greatly influenced the rate of adsorption. The linear adsorption model fitted best with the experimental results. Gibbs free energy values (?17 to ?20 kJ/mol) proposed physisorption and exothermic interaction of Iodosulfuron with selected soils. Analysis of variance and regression displayed a negative correlation of soil pH and K_d (R² = ?0.91) and positive correlation with organic matter (R² = 0.87). A good removal rate for was observed in soils by sawdust-derived activated carbon. Soil properties mainly; pH, organic matter and sand content greatly influenced Iodosulfuron removal phenomena. Biomass-derived activated carbon can thus be utilized as a sustainable remediation tool.     

Electrokinetic remediation and microbial community shift of β-cyclodextrin-dissolved petroleum hydrocarbon-contaminated soil

Electrokinetic (EK) migration of β-cyclodextrin (β-CD), which is inclusive of total petroleum hydrocarbon (TPH), is an economically beneficial and environmentally friendly remediation process for oil-contaminated soils. Remediation studies of oil-contaminated soils generally prepared samples using particular TPHs. This study investigates the removal of TPHs from, and electromigration of microbial cells in field samples via EK remediation. Both TPH content and soil respiration declined after the EK remediation process. The strains in the original soil sample included Bacillus sp., Sporosarcina sp., Beta proteobacterium, Streptomyces sp., Pontibacter sp., Azorhizobium sp., Taxeobacter sp., and Williamsia sp. Electromigration of microbial cells reduced the biodiversity of the microbial community in soil following EK remediation. At 200 V m⁻¹ for 10 days, 36% TPH was removed, with a small population of microbial cells flushed out, demonstrating that EK remediation is effective for the present oil-contaminated soils collected in field.