Spatial variability and concentration of arsenic in the groundwater of a region in Nadia district,West Bengal,India

Arsenic pollution in ground water in India and Bangladesh is considered to be the largest contamination problem in the world. About 15?–?18% of the area of West Bengal, India comes under the threat of arsenic (As) contamination and around 5.36 million people are exposed to this hazard. A detailed isoline map corresponding to variations in arsenic concentration and their spatial distribution was prepared for the study area, which comprised two villages Ghentugachi and Gotera in Nadia district, West Bengal and the total area covered was 808 hectares. The pattern of arsenic contamination was highly irregular and diverse. About 11.2% of the study area was affected most (?>?0.50?mg As l^?1) with sample As values reaching 0.71 and 0.80?mg?l^?1. About 22.5% of the area had As content between 0.20 and 0.50?mg?l^?1 and 33.9% of study area had As content below the WHO guideline of 0.01?mg As/l. Thus the local population living around these areas is vulnerable and exposed to arsenic contamination. None of the water samples exceeded the allowable limit (1.0?mg As l^?1) of As for water used in irrigation purposes. The spatial distribution map helped to determine zones with different As concentrations, making it possible to identify high-risk zones.     

Biovolatilization of Arsenic by Different Fungal Strains

The quantification of arsenic biovolatilization by microscopic filamentous fungi Aspergillus clavatus, A. niger, Trichoderma viride and Penicillium glabrum under laboratory conditions is discussed in this article. The fungi were cultivated on a liquid medium enriched with inorganic arsenic in pentavalent form (H₃AsO₄). Filamentous fungi volatilized 0.010 mg to 0.067 mg and 0.093 mg to 0.262 mg of arsenic from cultivation systems enriched with 0.25 mg (5 mg.l^?1 of arsenic in culture media) and 1.00 mg of arsenic (20 mg.l^?1 of arsenic in culture media), respectively. These results represent the loss of arsenic after a 30-day cultivation from cultivation systems. The production of volatile arsenic derivatives by the A. niger and A. clavatus strains was also determined by hourly sorption using the sorbent Anasorb (CSC) on the 29th day of cultivation.     

Effect of fulvic acids on lead-induced oxidative stress to metal sensitive Vicia faba L. plant

Lead (Pb) is a ubiquitous environmental pollutant capable to induce various morphological, physiological, and biochemical functions in plants. Only few publications focus on the influence of Pb speciation both on its phytoavailability and phytotoxicity. Therefore, Pb toxicity (in terms of lipid peroxidation, hydrogen peroxide induction, and photosynthetic pigments contents) was studied in Vicia faba plants in relation with Pb uptake and speciation. V. faba seedlings were exposed to Pb supplied as Pb(NO₃)₂ or complexed by two fulvic acids (FAs), i.e. Suwannee River fulvic acid (SRFA) and Elliott Soil fulvic acid (ESFA), for 1, 12, and 24?h under controlled hydroponic conditions. For both FAs, Pb uptake and translocation by Vicia faba increased at low level (5?mg?l^?1), whereas decreased at high level of application (25?mg?l^?1). Despite the increased Pb uptake with FAs at low concentrations, there was no influence on the Pb toxicity to the plants. However, at high concentrations, FAs reduced Pb toxicity by reducing its uptake. These results highlighted the role of the dilution factor for FAs reactivity in relation with structure; SRFA was more effective than ESFA in reducing Pb uptake and alleviating Pb toxicity to V. faba due to comparatively strong binding affinity for the heavy metal.     

Vermicomposting leachate as liquid fertilizer for the cultivation of sugarcane (Saccharum sp.)

In vermicomposting, the main product is the worm casts, but a leachate is generated that contains large amounts of plant nutrients. This leachate is normally diluted to avoid plant damage. We investigated how dilution of vermicompost leachate combined with different concentrations of nitrogen (N) - phosphorus (P) - potassium (K) triple 17 fertilizer, and polyoxyethylene tridecyl alcohol as dispersant and polyethylene nonylphenol as adherent to increase efficiency of fertilizer uptake, affected sugarcane plant development. The vermicomposting leachate with pH 7.8 and electrolytic conductivity 2.6 dS m^?1, contained 834 mg potassium (K) l^?1, 247 mg nitrate (NO₃^?) l^?1 and 168 mg phosphate (PO₄^3?) l^?1, was free of pathogens and resulted in a 65% germination index. Vermicompost leachate did not inhibit sugarcane growth and mixed with 170 g l^?1 NPK triple 17 fertilizer resulted in the best plant development. No dispersant or adherent was required to improve plant height and stem development.     

Toxicity of Lead to Freshwater Invertebrates (Water fleas; Daphnia magna and Cyclop sp) in Fish Ponds in a Tropical Floodplain

Acute toxicity of Pb to the water flea; (Daphnia sp) and Copepod, (Cyclop sp) both important component of zooplankton diet of fish was determined by static assay. A positive relationship between percentage mortality and exposure concentration was found in all tests. Mean 24-h LC50, 48-h LC50 and 96-h LC50 values were 2.51?±?0.0.04 mg l^?1, 1.88?±?0.06 mg l^?1 and 1.65?±?0.19 mg l^?1 for Daphnia spp and 3.11?±?0.03 mg l^?1, 2.97?±?0.05 mg l^?1 and 2.61?±?0.09 mg l^?1 for Cyclop spp, respectively. For all tested species did the LC50 values decrease with time; the decrease was more marked for Daphnia spp. Observed symptoms include spiral movement followed by change of body colour to white and rapid disintegration of the skin. The Daphnia spp. appear to be more sensitive to Pb poison than Cyclop spp. The results showed that concentrations of Lead (Pb) in excess of 0.19 mg l^?1 and 0.30 mg l^?1 can be potentially harmful to Daphnia magna and Cyclop spp respectively.     

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.     

Extraction and speciation analysis of roxarsone and its metabolites from soils with different physicochemical properties

Purpose

The application of roxarsone (ROX), an arsenic-containing compound, as a feed additive in the animal production industry results in elevated soil levels of ROX and its metabolites, namely, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenate (As(V)), and arsenite (As(III)). This study was conducted to study the extraction and speciation analysis of ROX-related arsenicals in soils with different physicochemical properties and the possible effects of soil properties on the extraction of ROX and its metabolites.

Materials and methods

Analytical method based on high-performance liquid chromatography (HPLC)-inductively coupled plasma–mass spectrometry (ICP-MS) was employed to determine the concentrations of As(III), DMA, MMA, As(V), and ROX extracted by different extraction solvents from different soils spiked by arsenicals. Validity of the developed method was assessed by the recovery efficiencies of arsenic species in soil-dissolved matter solutions containing 20 μg As?·?L^?1 of each arsenic species. Effects of soil properties on the extraction of ROX and its metabolites were analyzed by Pearson’s correlation.

Results and discussion

Arsenic species were separated using gradient elution of water and 20 mmol?·?L^?1 (NH₄)₂HPO₄ + 20 mmol?·?L^?1 NH₄NO₃ + 5 % methanol (v/v) within 27 min. The linear ranges of all arsenicals were 0–200 μg As?·?L^?1 with R ²?>?0.9996. The developed method provided lower limits of detection for As(III), DMA, MMA, As(V), and ROX (0.80, 0.58, 0.35, 0.24, and 1.52 μg As?·?L^?1, respectively) and excellent recoveries (92.52–102.2 %) for all five species. Arsenic speciation was not altered by 0.1 mol?·?L^?1 NaH₂PO₄ + 0.1 mol?·?L^?1 H₃PO₄ (9:1, v/v), which offered better average extraction efficiencies for As(III), As(V), DMA, MMA, and ROX (32.49, 92.50, 78.24, 77.64, and 84.54 %, respectively). Extraction performance of arsenicals was influenced by soil properties, including pH, cation exchange capacity (CEC), total Fe, and amorphous Fe.

Conclusions

ROX and its metabolites from soils could be satisfactorily separated by the developed method for the studied arsenicals. To extract arsenic species from soils, 0.1 mol?·?L^?1 NaH₂PO₄ + 0.1 mol?·?L^?1 H₃PO₄ (9:1, v/v) was recommended. Extraction efficiencies of arsenicals were influenced more by solvent composition than soil physicochemical properties. The present study provides a valuable tool and useful information for determining the concentrations of ROX and its metabolites in contaminated soils.

     

Short-Term Effects of Arsenate-Induced Toxicity on Growth, Chlorophyll and Carotenoid Contents, and Total Content of Phenolic Compounds of Azolla filiculoides

This study evaluated the toxic effects of arsenic (As) on the growth, total antioxidant activity, total content of phenolic compounds, and content of photosynthetic pigments of Azolla filiculoides. The aquatic fern was propagated and exposed to Yoshida nutrient solution contaminated with sodium arsenate (Na₂HAsO₄??7H₂O) at six concentrations (5, 10, 20, 30, 60, and 120???g?As?mL^?1), including the control without As contamination. Azolla cultures were kept under environmental chamber conditions?26??C, 12?h photoperiod and 80% HR for 96?h. Increased As concentrations (>30???g?mL^?1) significantly diminished growth of A. filiculoides and the total content of chlorophyll and total phenolic compounds, but significantly enhanced of total carotenoid?+?xanthophylls content. The concentrations of 5 and 10???g?As?mL^?1 significantly stimulated the growth of A. filiculoides. This aquatic fern tolerates As concentrations lower than 30???g?mL^?1, and its maximum As accumulation (28???g?g^?1 dry weight) was achieved when exposed to 60???g As mL^?1, but showing clear symptoms of As toxicity.     

A Laboratory Study on Revegetation and Metal Uptake in Native Plant Species from Neutral Mine Tailings

Lygeum spartum, Zygophyllum fabago and Piptatherum miliaceum are typical plant species that grow in mine tailings in semiarid Mediterranean areas. The aim of this work was to investigate metal uptake of these species growing on neutral mine tailings under controlled conditions and their response to fertilizer additions. A neutral mine tailing (pH of soil solution of 7.1–7.2) with high total metal concentrations (9,100 and 5,200 mg kg^?1 Zn and Pb, respectively) from Southern Spain was used. Soluble Zn and Pb were low (0.5 and <0.1 mg l^?1, respectively) but the major cations and anions reached relatively high levels (e.g. 2,600 and 1,400 mg l^?1 Cl and Na). Fertilization caused a significant increase of the plant weight for the three species and decreased metal accumulation with the exception of Cd. Roots accumulated much higher metal concentrations for the three plants than shoots, except Cd in L. spartum. Shoot concentrations for the three plants were 3–14 mg kg^?1 Cd, 150–300 mg kg^?1 Zn, 4–11 mg kg^?1 Cu, and 1–10 mg kg^?1 As, and 6–110 mg kg^?1 Pb. The results indicate that neutral pH mine tailings present a suitable substrate for establishment of these native plants species and fertilizer favors this establishment. Metal accumulation in plants is relatively low despite high total soil concentrations.     

Kinetically controlled release of uranium from soils

Although trade element uptake on and release from solid phases are fundamental controls on the migration of the elements in the environment, the controls are incompletely understood. The extraction of uranium from two soils, both of which have been labelled naturally with uranium, was therefore studied using a cation resin exchange technique. One soil was a peat from the Needle's Eye natural analogue site, Scotland, and the other was a calcareous brown earth from Derbyshire, England. The effects of different exchanging cations, solution pH and the presence of complexing anions (Cl^?, CO₃^2?, SO₄^2?) in solution on uranium extraction were assessed. The extraction could be described by a simple, first-order kinetic model with up to three rate constants being identifiable in individual experiments. In both soils no single reaction pathway appeared to dominate, and extraction was slow, with rate constants of 10^?3?10^?4 h^?1 in acid conditions and around 10^?6 h^?1 in neutral conditions. Half-times for uranium release in the experiments were in the range 30–60 days in acid and around 10 years in neutral conditions; in the field they are therefore expected to be several years at both sites. Incorporation of kinetic factors into a simple one-dimensional migration model illustrates that their overall effect is to retard migration. Ideally, therefore, reaction rates should be taken into account in predictive modelling of element transport.     

Characteristics of Nitrous Oxide (N2O) Emissions from Intermittently-Aerated Sequencing Batch Reactors Treating the Separated Liquid Fraction of Anaerobically Digested Pig Manure

In this study, the N₂O emission from an intermittently aerated sequencing batch reactor (IASBR-1) treating the separated liquid fraction of anaerobically digested pig manure (SLAP) was investigated. The wastewater had chemical oxygen demand (COD) concentrations of 11,540?±?860?mg?l^?1, 5-day biochemical oxygen demand (BOD₅) concentrations of 2,900?±?200?mg?l^?1and total nitrogen concentrations of 4,041?±?59?mg?l^?1, with low COD:N ratios (2.9, on average) and BOD₅:N ratios (0.72, on average). Synthetic wastewater, simulating the SLAP with similar COD and nitrogen concentrations but with higher BOD₅ concentrations of up to 11,500?±?100?mg?l^?1, was treated in another identical reactor (IASBR-2) to compare the effects of carbon source on nutrient removals and N₂O emissions. In steady-state, soluble N₂O accumulated in the non-aeration periods, with the highest N₂O concentrations measured at the end of the non-aeration periods. There was a significant reduction in N₂O concentrations during the aeration periods with reductions occurring immediately on commencement of aeration. The mean N₂O emissions in an operational cycle were 253.6 and 205.3?mg for IASBR-1 and IASBR-2, respectively. During the non-aeration periods, only 8.3% and 8.4% of total N₂O emissions occurred in IASBR-1 and IASBR-2, respectively; while during the aeration periods, 91.7% and 91.6% of N₂O emissions took place in IASBR-1 and IASBR-2, respectively. The mean specific N₂O generation rates were 0.010 and 0.005?mg (g VSS·min)^?1 in the aeration periods, 0.024 and 0.021?mg (g VSS·min)^?1 in the non-aeration periods for IASBR-1 and IABSR-2, respectively. Mean nitrogen removal via N₂O emissions was 15.6% and 10.1% for IASBR-1 and IASBR-2, respectively. The IASBR-1 with low influent BOD₅ concentrations emitted and generated more N₂O.     

Toxicity of uranium to Daphnia magna

The toxicity of U to Daphnia magna was determined in acute and chronic tests. The 48-hr LC₅₀ of U (VI) in Columbia River water was 6 mg L^?1. Acute toxicity diminished by a factor of 7.5 as mean water hardness and alkalinity values increased from 70 mg L^?1. and 57 mg L^?1. to 195 mg L^?1. and 130 mg L^?1. respectively. This effect was most likely the result of complexation of uranyl ion with carbonate ions. D. magna reproduction was suppressed in Columbia River water at U concentrations between 0.5 and 3.5 mg L^?1. Potential hazards of U to aquatic life are discussed as they relate to mining practices.     

伴随阴离子对马铃薯种植冲击土中钾素固持与淋溶的影响

A column study was carried out to assess the influence of accompanying anions on potassium (K) leaching at potato growing sites with different soil textures (sandy loam and clay loam) in northwestern India. Potassium was applied in the top 15 cm layer of soil column at 30 and 60 mg K kg^-1 through different sources having different accompanying anions (Cl^-, SO₄^2-, NO₃^- and H₂PO₄^-). Maximum K was retained in the top 0--15 cm layer with a sharp decrease in K content occurring in 15--30 cm layer of the soil column. The trend was similar for both levels of applied K as well as frequency of leaching and soil type. The decrease of K content in soil column after four leaching events was maximum in case of Khanaura sandy loam, while only minor decrease was observed in Hundowal clay loam when K was applied at 60 mg K kg^-1, indicating higher potential of clay rich soil to adsorb K. In general, the K leaching in presence of the accompanying anions followed the order of SO₄^2- ≤ H₂PO₄^2- < NO₃^- = Cl^-. Highest 1 mol L^-1 CH3COONH4-extractable K was retained when K was applied along with SO42- and H2PO4- anions, and the least was retained when accompanying anion was Cl^-1. The influence of anions was more pronounced in the light textured soil and at high amounts of K application. Higher levels of K application resulted in higher losses of K, especially in sandy loam soil as observed from the leachate concentration. Among the different K sources, the maximum amount of K leaching was noticed in the soil column amended with KCl. After four leachings, the maximum amount of K leached out was 6.40 mg L^-1 in Hundowal clay loam and 9.29 mg L^-1 in Khanaura sandy loam at 60 mg K kg^-1 of soil application through KCl. These concentrations were lower than the recommended guideline of the World Health Organisation (12.00 mg L^-1).     

Concentrations and depositions of SO2, SO4 2− etc. in a Chongqing suburban forested area

During the period from 25 May 1991 to 30 May 1992 the atmospheric concentrations and depositions of oxides of sulfur were continuously measured in a suburban masson pine forest which is currently experiencing severe dieback, in Chongqing, China. The annual mean concentrations of SO₂ and particulate SO₄ ^2? were 220 μ g/m³ (77 ppbv) and 32 μ g/m³ respectively. The atmospheric concentrations of these sulfur compounds were high in late autumn and winter. The annual wet and dry depositions of sulfur to the forest as measured by throughfall and stemflow were 93.1 and 46.6 kgSha^?1a^?1 respectively. These depositions are among the highest level ever reported in the world. Althogh the cause of the dieback of the masson pine trees has not been unequivocally determined, it is probable that the direct impact of SO₂ is more likely the cause than acid deposition.     

Detection of Water and Sediments Pollution of An Arid Saltern (Sfax, Tunisia) by Coupling the Distribution of Microorganisms With Hydrocarbons

We investigated the coupling of abundance of bacteria, phytoplankton and ciliates with hydrocarbons in the surface water and sediments of five interconnected ponds in the arid Sfax solar salterns. This study aimed at determining the potential sources of hydrocarbons and the effects of salinity gradients on microorganism metabolism. Hydrocarbon analysis was performed by gas chromatography (GC-FID) and gas chromatography coupled with mass spectrometry (GC-MS). The GC-FID allowed the detection of aliphatic hydrocarbons and n-alkanes ranging from n-C₁₃ to n-C₃₀. Total aliphatic hydrocarbon concentrations varied from 92.5 mg. l^?1 in the first pond (having marine characteristics) to 661.1 mg. l^?1 in the last pond (crystallizer) (316.8?±?120.1 mg. l^?1) for water samples and from 26.7 to 127.8 μg. g^?1 dry weight for sediment samples. The GC-MS enabled us to detect halogenated hydrocarbons (bromoalkanes and chloroalkanes) and n-alkenes. The distribution of n-alkanes indices coupled to several environmental factors suggests that a major fraction of hydrocarbons resulted from both prokaryotic (bacteria) and eukaryotic (protists) developments. A low hydrocarbon fraction might be petrogenic.     

Arsenic Mining Waste in the Catchment Area of the Madrid Detrital Aquifer (Spain)

In recent years, elevated arsenic concentrations in groundwater used for drinking water supplies have been recognised in the Madrid Tertiary detrital aquifer. Although only natural causes have been suggested as the source of arsenic, this study aims to highlight that the anthropogenic contribution cannot be disregarded. During the sub-catchment??s areas sampling, we found many geographical sites where natural arsenopyrite [FeAsS] originally encapsulated in pegmatite bodies and quartz veins, was artificially outcropped and dumped out, since mining wastes were scattered and exposed to weathering. Several mineral and ground specimens were collected to analyse its mineralogical and chemical composition by X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF) spectrometry and by Environmental Scanning Electron Microscope (ESEM). Both, the abundant existence of secondary phases, such as scorodite [FeAsO₄?2H₂O] and jarosite [KFe₃(SO₄)₂(OH)₆], much more soluble than arsenopyrite, and the lixiviation experiments of arsenopyrite in acidic media to simulate acid mine drainage (AMD) conditions, usually found in old mining districts, point to a potential risk of arsenic contamination of surface water bodies, which operate as recharged waters of the aquifer in the studied area. The elemental determination of heavy metals present in ground samples by XRF analyses, reaching up to 1,173 mg kg^?C1 of copper, 347 mg kg^?C1 of lead and 113,702 mg kg^?C1 of arsenic; and the physicochemical and arsenic fractionation studies of soil samples, led us to classify the soil as Spolic Technosol (Toxic). The contamination of the area due to old mining activities could release arsenic to Madrid water supplies; accordingly, additional decontamination studies should be performed.     

Arsenic in field‐collected soil solutions and extracts of contaminated soils and its implication to soil standards

Large concentrations of arsenic in soils, sediments, and freshwaters require risk assessment across the Central Alps and other regions. We measured arsenic concentrations in soil samples collected from 38 sites located in the Austrian Central Alps that had been contaminated due to mining and smelter activities and geogenic mineralization. Medians and ranges of arsenic concentrations (in mg kg^—1) in the soil solid phase were: 77.1 (1—3000) for the total (As_t), 19.2 (0—726) for (NH₄)₂C₂O₄‐extractable (As_o), 2.35 (0—169) for (NH₄)₂HPO₄‐extractable (As_p), and 0.143 (0—11.1) for (NH₄)₂SO₄‐extractable (As_s) arsenic. Arsenic concentrations in soil solutions (As_sol) collected from organic surface layers and mineral horizons at five selected sites using suction cups fitted with nylon membranes ranged from 0 to 171 μg l^—1. Typically, the prevailing species of As in the soil solution was As(V). As_sol was correlated with As_s (As_sol = 0.279 + 15.6 As_s; r² = 0.938; n = 17) and As_t (As_sol = 1.272 + 0.043 As_t; r² = 0.833; n = 17). Using these empirical models, As_sol can be predicted quite accurately based on extraction with 0.05 M (NH₄)₂SO₄ or total arsenic concentrations in the soil. Linking these models to drinking water standards (DWS) we propose soil standards for freshwater protection that vary for As_s (mg kg^—1) between 0.62 (for DWS = 10 μg l^—1 WHO) and 3.19 (for DWS = 50 μg l^—1). Corresponding standards for As_t (mg kg^—1) are 203 (DWS = 10 μg l^—1) and 1133 (DWS = 50 μg l^—1). These considerations demonstrate that changes in legislation on DWS may have dramatic impact on As concentrations in soil that are acceptable for groundwater protection.     

Impact of molybdenum on Chinese cabbage response to selenium in solution culture

Molybdenum (Mo) and selenium (Se) are both essential micronutrients for animals and humans. Increasing Mo and Se contents in food crops offers an effective approach to reduce Mo and Se deficiency problems. A hydroponic trial was conducted to investigate the interactions of Mo and Se on uptake, transfer factors (TF _shoot ) as well as distribution coefficients (DC) of Mo and Se on Chinese cabbage (Brassica campestris L. ssp. Pekinensis). In Experiment 1 three concentrations of Mo (0.01, 0.1 and 1?mg?L^?1) and four concentrations of Se (0, 0.01, 0.1 and 1?mg?L^?1) were arranged with a randomized block design. In Experiment 2, there were three treatments, 0.1?mg?L^?1 Mo, 0.1?mg?L^?1 Se and a combination of 0.1?mg?L^?1 Mo?+?0.1?mg?L^?1 Se. Experiment 1 showed that Se decreased Mo concentrations in shoots and roots. The impact of Mo on Chinese cabbage response to uptake of Se varied, depending on whether the root Se concentration was saturated or not; Experiment 2 showed that there is a strong antagonism between Mo and Se on nutrition uptake when Mo and Se deficiencies persist for long periods; Mo and Se were easily translocated from solution to plants and from roots to shoots. The results will also be of help in cultivating Mo-enriched and Se-enriched crops.     

Evaluation of Pb Phytoremediation Potential in Buddleja asiatica and B. paniculata

The phytoremediation potential for Pb of Buddleja asiatica (a wild species) and a closely related cultivated species, B. paniculata, was investigated by means of field survey, hydroponic and pot experiments, and field trial experiments. Field surveys showed that B. asiatica had an extraordinary accumulation capacity and tolerance for Pb. Plants grown in soil with 2,369.8–206,152 mg kg^?1 total Pb accumulated 1,835.5–4,335.8 mg kg^?1 Pb in their shoots. Under hydroponic conditions (10, 20 mg l^?1 Pb), both B. asiatica and B. paniculata showed unusually high concentrations of Pb in their roots (12,133–21,667 mg kg^?1) and increased biomass production. A pot experiment in a greenhouse without any soil amendments was conducted on three different soils with various Pb contents (10,652, 31,304, 89,083 mg kg^?1) for 3 months. The results showed that both species of Buddleja had an increase in the biomass similar to the control plants. There was a slight decrease in survival rates of plants grown in soil with 89,083 mg kg^?1 Pb content. A field trial experiment was conducted for 6 months at three sites around the Pb mine area in which plants were provided with Osmocote fertilizer. Both Buddleja species showed 100% survival, increased biomass production and phytoextraction capacity (TF 1.1–2.3) when grown in soil with Pb content of 94,584–101,405 mg kg^?1. Plants accumulated 2,273–3,675 mg kg^?1 Pb in their shoots. The results suggest these Buddleja plants are suitable for use in the phytoremediation of Pb-contaminated soil.     

Acute toxicity of water soluble fractions derived from a coal liquid (SCR-II) to three aquatic organisms

Acute toxicity screening tests were conducted with water soluble fractions (WSFs) of a solvent refined coal (SRC-II) liquid from a pilot plant and three reference organisms: the cladoceran Daphnia magna, the fathead (FH) minnow Pimephales promelas, and larvae of the midge fly Chironomus tentans. Stock WSFs typically contained 900 to 1100 mg l^?1 total carbon (TC) and 700 to 800 mg l^?1 total dye complexable phenolics, with lower concentrations of aromatic and saturate hydrocarbons and N compounds. Under standard test conditions (temperature 20 °C, pH 7.3 to 8.2 and hardness 65 to 80 mg l^?1 CaCO₃), mean LC50 values in mg l^? TC were 3.3 for daphnia, 11.l for FH minnow, and 13.7 for midge larvae. Acute toxicity was also examined under other water quality conditions (temperature 10 or 25 °C, pH 6.0 or 6.5, and hardness ? 180 to 220 mg 1^?1 CaCO₃). The coal liquid was less toxic to daphnids at 10 °C than at 20 or 25 °C, but response of other organisms at different temperatures varied. The pH of the liquid had little effect on toxicity values. All organisms were less susceptible in hard water. Chemical compositions of stock WSFs were similar, suggesting that temperature, pH, and hardness had little effect on solubility of major synfucl components. Dilution indexes for stock WSFs were higher than for petroleum oils, and reflect the greater solubility of chemicals from the liquified coal in freshwater.