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1.
Elevated levels of As in contaminated water and soil could pose a major threat to the environment. Relatively high levels of As have been reported in agricultural drainage water and in evaporation pond sediments in Kern County, California. The objective of this study was to enumerate and isolate As-resistant microorganisms from agricultural drainage water and evaporation pond sediments and to assess their tolerance to metals, metalloids and antibiotics. The culture medium was amended with arsenite (III), arsenate (V), methylarsonic acid (MAA), and dimethylarsinic acid (DMA). Among the water samples, As(V), MAA, and DMA added to the medium at concentrations from 0.1 to 1000 mg L?1 showed no effect on the colony forming units (CFUs) compared with no As supplementation, while arsenite (III) (> 1.0 mg L?1) inhibited the population. The sediments showed three trends: (i) no effect on CFUs in the presence of As(V) up to 1000 mg kg?1, (ii) a decline in CFUs in the presence of > 100 mg kg?1, As(III), and (iii) an increase in CFUs upon the addition of MAA or DMA at > 25 mg kg?1, Arsenite (III) was much more toxic to the indigenous microflora than any other As species. Arsenite (III) inactivates many enzymes by having a high affinity for thiol groups of proteins. A plate diffusion method was used to assess the tolerance of the As-resistant bacteria to heavy metals, metalloids and antibiotics. Of 14 isolates tested, all were resistant to Co, Cu, Pb, Ni, Mo, Cr, Se(IV), Se(VI), As(III), As(V), Sb, Sn, and Ag (50 µg mL?1). The most toxic trace elements were Cd followed by Hg>Te>Zn. Multiple antibiotic tolerance (resistance to 2 or more antibiotics) was found among 43% of the isolates. The As-resistant bacteria showed a high tolerance to metals and antibiotics.  相似文献   

2.
The purpose of this study is to evaluate the combined Cr(VI) removal capacities of nonliving (untreated rubber wood sawdust, URWS) and living biomass (URWS-immobilized Acinetobacter haemolyticus) in a continuous laboratory scale downward-flow two column system. Synthetic solutions of Cr(VI) between 237 and 320 mg L?1 were mixed with 1 g L?1 brown sugar in a nonsterile condition. Final Cr(VI) of between 0 and 1.6 mg L?1 indicate a Cr(VI) removal capacity of 99.8–100%. The bacterial Cr(VI) reduction capacity increased with column length. This study shows the feasibility of using the two column system consisting of living (bacteria) and nonliving biomass (URWS) as a useful alternative treatment for Cr(VI) contamination in the aqueous system.  相似文献   

3.
Bader  J. L.  Gonzalez  G.  Goodell  P. C.  Pillai  S. D.  Ali  A. S. 《Water, air, and soil pollution》1999,109(1-4):263-276
Chromium-containing industrial effluents are primarily responsible for environmental contamination by toxic and highly mobile, hexavalent chromium. The dilution plate-count method, using media amended with Cr(VI) at concentrations ranging from 0 to 1000 mg L-1, was used to compare the sizes of Cr(VI)-resistant bacterial populations from a soil contaminated with 25 100 mg kg-1 total Cr [12 400 mg kg-1 Cr(VI)] to those isolated from a slightly contaminated soil (99.6 mg kg-1 total Cr) and two other soils without any history of Cr contamination. Bacterial populations resistant to 500 mg L-1 Cr(VI) were isolated from all soils except the heavily contaminated soil. To determine whether Cr-resistant bacterial populations were indigenous to both the contaminated and the uncontaminated soils, enrichment cultures containing Cr(VI) at concentrations ranging from 0 to 1000 mg L-1 were employed. Bacterial populations, as high as 105 (colony forming units) CFU g-1 soil, tolerant of 500 mg L-1 Cr(VI) were isolated from all soils within 48 h of enrichment suggesting that the presence of aerobic Cr(VI)-resistant bacterial populations is unrelated to contamination levels or contamination history. However, identification of these resistant bacteria using fatty acid profiles was unsuccessful suggesting that these populations may have unique characteristics. Fungal colonies resistant to 1000 mg L-1 Cr(VI) were routinely isolated from both uncontaminated and contaminated soils. The results suggest that Cr-resistant microorganisms may be present in soils, even those with no history of Cr contamination.  相似文献   

4.
A multiple-antibiotic resistantE. coli was applied to rye-grass covered field mini-plots to simulate point-source contamination. Using three mini-plots for testing and a fourth as a control, the ability of the tracer bacterium to survive under field conditions was studied. Three test plots each received separately 107, 108, or 1010 cfu mL?1 E. coli grown for 24 h. in 5 L one-third strength Tryptic soy broth. In Phase I of the study, it was determined that the tracer disappeared from leaf surfaces of rye-grass covering the plots after 41 days. In Phase II, determination of the presence of the tracer in the top 2″ (5 cm) of soil after two months elapsed time indicated that tracer cfu/g dry wt. of soil had declined five, three, and three-logs for test plots 1,2, and 3. In Phase III, subsurface soil sampling using a soil auger on the three test minei-plots indicated the tracer had penetrated through the top-soil and into the underlying B horizon (20 to 50 cm down). In Phase IV, detailed sampling by excavation of the subsurface soil Horizons of the third test mini-plot showed that the tracer had also penetrated through the hardpan (C Horizon) located 0.6 m below the surface to enter the groundwater (1.06 m deep) (Phase V).E. coli counts fell precipitously to 103 cfu g?1 in soil and then, in the groundwater at the groundwater-soil interface, persisted at a concentration of 103 cfu 100 mL?1 for 2 yr. As time past, tracer counts fell to 145 cfu/100 mL in 6 yr. rose to 820 cfu 100 mL?1 in 1986 (8 yr elapsed time), and then fell to 25 cfu 100 mL?1 in 1991 after 13 yr. Serotyping of 1986E. coli isolates indicated that 62% were of the original tracer serotype (0.128:B12) while only 43% of the 1991 isolates were of the same serotype. The penetration rate of the tracer down through the mini-plot soil into the groundwater was 0.02 m day?1 while downslope dispersion occurred at an estimated rate of 1.0 m day?1. The implications of the above findings are discussed.  相似文献   

5.
The removal efficiency and tolerance of Typha domingensis to Cr(VI) in treatments with and without organic matter (OM) addition were evaluated in microcosm-scale wetlands. Studied Cr(VI) concentrations were 15 mg L?1, 30 mg L?1, and 100 mg L?1, in treatments with and without OM addition, arranged in triplicate. Controls (without neither metal nor OM addition—without metal with OM addition) were disposed. Cr(VI) was removed efficiently from water in all treatments. OM addition enhanced significantly Cr(VI) and total Cr removals from water. In the treatments with OM addition, significantly higher Cr concentrations were found in sediment than the treatments without OM addition. Plants of the treatments without OM addition showed significantly higher Cr concentrations in tissues but lower biomass increase than the treatments with OM addition. The highest Cr concentrations in tissues were observed in submerged parts of leaves, followed by roots. According to SEM analysis, in the 100 mg L?1 treatments, the highest Cr accumulation was observed in the epidermis of old leaves. Although Cr(VI) produced changes in root morphology, the OM addition favored the plant growth. In T. domingensis, root morphological plasticity is an important mechanism to improve metal tolerance and Cr uptake in wetland systems minimizing the environmental impact.  相似文献   

6.
This study describes application of free liquid membrane (FLM) in micro-electromembrane extraction (μ-EME) of Cr(VI) from wastewater samples. Amount of Cr(VI) was quantified by electrothermal atomic absorption spectrometry. The transportation of Cr(VI) across the FLM was explored by electrokinetic migration and ion-exchange process. FLM and acceptor solution types, pH of donor and acceptor solutions, applied electrical potential, as well as FLM thickness were optimized. Presence of an anion exchange carrier (methyl trialkyl-ammonium chloride, Aliquat 336) in FLM facilitated Cr(VI) transportation. The best performance was observed for 1-octanol (containing 5% Aliquat 336) with thickness of 1 mm used as FLM, under applied electrical potential of 75 V, when 0.5 M NaClO4 and 0.1 M HCl were used as the acceptor and donor phases, respectively; and the extraction time was set to 5 min. Linearity was obtained in the working range of 0.5–14.0 ng mL?1 Cr(VI) (R2?>?0.98). The calculated limit of detection was below 0.06 ng mL?1. Application of this method to wastewater samples showed that relative recoveries of the spiked Cr(VI) in the samples were in the range of 73.8–85.1%, based on the standard addition method.  相似文献   

7.
The main purpose of this work was to conduct a kinetic study on cell growth and hexavalent chromium [Cr(VI)] removal by Candida sp. FGSFEP in a concentric draft-tube airlift bioreactor. The yeast was batch-cultivated in a 5.2-l airlift bioreactor containing culture medium with an initial Cr(VI) concentration of 1.5 mM. The maximum specific growth rate of Candida sp. FGSFEP in the airlift bioreactor was 0.0244 h?1, which was 71.83% higher than that obtained in flasks. The yeast strain was capable of reducing 1.5 mM Cr(VI) completely and exhibited a high volumetric rate [1.64 mg Cr(VI) l?1 h?1], specific rate [0.95 mg Cr(VI) g?1 biomass h?1] and capacity [44.38 mg Cr(VI) g?1 biomass] of Cr(VI) reduction in the airlift bioreactor, with values higher than those obtained in flasks. Therefore, culture of Candida sp. FGSFEP in a concentric draft-tube airlift bioreactor could be a promising technological alternative for the aerobic treatment of Cr(VI)-contaminated industrial effluents.  相似文献   

8.
The influence of culture medium composition on chromium(VI) quantification according to diphenylcarbazide (DPC) colorimetric determination was evaluated. Considering the eventual biospeciation of Cr(VI) as a mechanism of microbial bioremediation, the possibility to quantify Cr(III) in culture medium was also explored. Yeast nitrogen base (YNB) was identified as the least interferent culture medium for Cr(VI) quantification by DPC and it was applied to compare different strategies for Cr(III) oxidation. The most appropriate oxidation protocol consisted in the reaction with 80 mM KIO4 at room temperature for 30 min prior to DPC. Parameters like basal culture medium (vitamins + salts + oligoelements), C and N source were systematically evaluated, either independently or in combination. Results demonstrated that C source was the most interferent culture medium component, being the use of sucrose preferable to glucose. A medium arbitrarily named as YNB′ (YNB without amino acids and ammonium sulfate plus 50 g L?1 sucrose and 0.6 g L?1 (NH4)2SO4) was defined for Cr(VI)-amended fungal cultures. Kinetics of growth, Cr(VI) removal, and nutrient consumption for isolates A. pullulans VR-8, filamentous fungus PMF-1, and Lecythophora sp. NGV-1 were obtained. The order of Cr(VI) removal efficiency was as follows: A. pullulans VR-8 > Lecythophora sp. NGV-1 > filamentous fungus PMF-1, and a similar trend was observed for biomass yield and nutrients consumption. Studies on biospeciation by means of the selected Cr(III) oxidation protocol were unsuccessful, leading to Cr(VI) values much lower than expected. It revealed that this kind of protocols should be cautiously evaluated when studying microbial Cr(VI) bioremediation.  相似文献   

9.
In order to study the potential use of microfauna as an indicator of effluent quality and operational parameters in an activated sludge system for treating piggery wastewater, an experimental sequencing batch reactor was set up and evaluated by biological and physical–chemical analyses for 12 months. Results show that microfauna (and specifically ciliate protozoa) are a good parameter for assessing effluent quality in terms of both chemical oxygen demand (COD) and ammonia and for assessing the organic and nitrogen load of the system. Specifically, the abundance of ciliates decreases from 20,000 individuals·mL?1 to ca. 2,500 individuals·mL?1 and from ca. 10,000 individuals mL?1 to ca. 200 individuals mL?1 when effluent concentration is between 550 and 750 mg L?1 and above 100 mg L?1 to the COD and ammonia concentrations, respectively. Furthermore, microfauna abundance is reduced from ca. 18,000 individuals mL?1 (organic load between 0.1 and 0.2 mg COD mg total suspended solids (TSS)?1 day?1) to ca. 500 individuals mL?1 (organic load between 0.3 and 04 mg COD mg TSS?1 day?1). Microfauna abundance also decreases as nitrogen loading increases. Nitrogen loading in the range of 5–60 mg NH4–N g TSS?1 day?1 does not have any significant effect on microfauna abundance. However, ammonia loading from 60 to 120 mg NH4–N g TSS?1 day?1 reduces microfauna abundance ca. 6-fold. Ciliate protozoa were the largest microfauna group during the whole period of study, representing ca. 75% of the total microfauna abundance. The largest group in the ciliate community was that of the free-swimming ciliates. This was followed by the group of attached and crawling ciliates. Specifically, the dominant ciliate species during the whole study period were Uronema nigricans, Vorticella microstoma-complex, Epistylis coronata, and Acineria uncinata.  相似文献   

10.
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.  相似文献   

11.
The effects of Hg, As, Pb, Cu, Cd, and Cr (1, 2, and 5 mg L?1 each) on Azolla pinnata R. Br. were analyzed. The treatments (2 and 5 mg L?1) of the heavy metal pollutants decreased Hill activity, chlorophyll, protein and dry wt, and increased tissue permeability over control values. The effects were most pronounced with the treatment of 5 mg L?1. The harmful effects of the metals were, in general, found by the treatments in the order: Cd 〉 Hg 〉 Cu 〉 As 〉 Pb 〉 Cr. There was no significant change in these parameters at 1 mg L?1 of the metals over control. Thus Azolla pinnata shows tolerance to the heavy metals tested up to 1 mg L?1 each.  相似文献   

12.
Continual discharge of textile wastewaters loaded with a variety of synthetic dyes and metals is considered as a huge threat to surrounding ecosystems. In order to treat these undesirable pollutants, microbial bioremediation is considered as an efficient and economical technique. This study was conducted to evaluate the use of bacterial strains for simultaneous removal of azo dyes and hexavalent chromium [Cr(VI)]. Fifty-eight bacterial strains were isolated from Paharang drain wastewater and tested for their potential to decolorize reactive red-120 (RR-120) in the presence of 25 mg L?1 of Cr(VI). Among the tested isolates, FA10 decolorized the RR-120 most efficiently and was identified as Acinetobacter junii strain FA10. Based on quadratic polynomial equation and response surfaces given by the response surface methodology (RSM), Cr concentration and pH were found to be the main factors governing the RR-120 decolorization by FA10. The strain FA10 also exhibited a substantial salt resistance since it showed a considerable decolorization of RR-120 even in the presence of 150 g L?1 of NaCl. Moreover, the strain FA10 also showed the potential to simultaneously remove the Cr(VI) and the selected azo dyes in the same medium. More than 80 % of the initially added Cr(VI) was removed over 72 h of incubation along with the appreciable decolorization efficiency. The strain FA10 also exhibited good tolerance to considerable levels of different heavy metals. The findings of this study suggest that the strain FA10 might serve as an efficient bioresource to develop the biotechnological approaches for simultaneous removal of different azo dyes and heavy metals including Cr(VI).  相似文献   

13.
A chromated-copper-arsenate (CCA) wood preservative was tested for toxic effects on the growth of a bacterial culture (Flavobactenum sp. ATCC 53874) capable of biodegrading pentachlorophenol, another wood preservation chemical. Both a commercially available CCA preparation and a laboratory-prepared CCA solution were tested. Each had an inhibitory effect on the growth of Flavobacterium at diluted CCA levels as low as 1.0×10?4 to 1.0×10?5% wt vol?1. The commercial formulation was generally more toxic. EC50 values calculated after 96 hr of incubation were 1.2 ×10?4% wt vol?1 for the commercial material (containing 0.15/0.097/0.14 μg mL?1 of Cr/Cu/As, respectively) and 3.8×10?4% for the laboratory solution (containing 0.51/0.31/0.49 μg mL?1 of Cr/Cu/As, respectively). CCA toxicity increased during the first 7 to 8 days and then slowly decreased for the balance of the 21 day incubation period. Biodegradation of pentachlorophenol residues in contaminated soil will be negatively affected by the presence of CCA as a co-contaminant.  相似文献   

14.
The goal of this study was to compare the performances of strong base anion (SBA) exchange and activated carbon adsorption in the removal of hexavalent chromium, Cr(VI), from a real groundwater matrix exploited for drinking purposes. Two SBA resins and three granular activated carbons (GAC) were tested by batch experiments for kinetics and equilibrium isotherm determination. SBA resins showed higher affinity toward Cr(VI) (present in raw water at about 20 μg L?1) with respect to the GACs, with faster kinetics and higher equilibrium adsorption capacities. Among GACs, vegetal-based carbons showed higher Cr(VI) removal efficiencies than the mineral-based carbon, which can be related to the more developed textural properties. SBA resins also displayed relevant removal capacities towards nitrate and sulfate (present at mg L?1 concentration levels), while boron (present at about 60 μg L?1) was effectively removed by GACs. Batch experiment results were elaborated to estimate the chromium throughputs for the studied materials, to preliminary compare their performances in a real-scale application. The monitoring of a real-scale GAC adsorption stage permitted to validate throughputs estimation and confirmed that, despite being effective toward synthetic organics, GAC adsorption is a not feasible solution for Cr(VI) removal, with extremely early breakthrough. SBA exchange process resulted to be the most suitable solution, providing the best sorbent usage rates. However, SBA resin usage rates can strongly increase when considering the removal of nitrate and sulfate ions, requiring much shorter cycle times.  相似文献   

15.
Purpose: The purposes of this study were to determine the effect of matrine on the migration and the colonization dynamics of the two fluorescent-tagged rhizobia in Gannong No.5 alfalfa (Medicago sativa L. Gannong No. 5) tissues, and also to determine the effect of the combination treatments on alfalfa seedlings’ growth.

Materials and methods: 0, 100, 200, 300 and 400 mg L?1 matrine levels were added into two cyan fluorescent protein (CFP)-tagged rhizobia; Ensifer meliloti LZgn5f (gn5f) and Ensifer meliloti 12531f (12531f), respectively; and drenched the alfalfa root with the inoculants. Then the migration and colonization of the two rhizobia in alfalfa on D7, D14, D21 and D28, and subsequently seedling growth were investigated.

Results: The results showed that the optimum matrine level enhanced the colonization of both fluorescent-tagged rhizobia in alfalfa roots and the highest colonization densities of log 6.31 cfu g?1 and log 5.87 cfu g?1 were achieved by adding 300 mg L?1 matrine into 12531f and adding 100 mg L?1 matrine into gn5f, respectively. They could migrate to the aerial tissues and most colonize stems through the application of adding 300 mg L?1 matrine into 12531f and 100 mg L?1 matrine into gn5f, respectively. No fluorescent-tagged rhizobia were detected in the control treatment. Alfalfa seedling growth parameters like leaf chlorophyll content, seedling growth rate, root length, seedling biomass and total N percentage also increased the most when 300 mg L?1 matrine was added into 12531f and 100 mg L?1 matrine added into gn5f treatments.

Conclusions: Our results suggest that 300 mg L?1 matrine added into 12531f and 100 mg L?1 matrine added into gn5f might be exploited to promote the colonization of rhizobia in alfalfa tissue and positively impact growth and yield, indicating possible benefits for plant cultivation.  相似文献   

16.
High phosphorus (P) in surface drainage water from agricultural and urban runoff is the main cause of eutrophication within aquatic systems in South Florida, including the Everglades. While primary sources of P in drainage canals in the Everglades Agricultural Area (EAA) are from land use application of agricultural chemicals and oxidation of the organic soils, internal sources from canal sediments can also affect overall P status in the water column. In this paper, we evaluate P release and equilibrium dynamics from three conveyance canals within the EAA. Incubation and flux experiments were conducted on intact sediment cores collected from four locations within the Miami, West Palm Beach (WPB), and Ocean canal. After three continuous exchanges, Miami canal sediments reported the highest P release (66?±?37 mg m?2) compared to WPB (13?±?10 mg m?2) and Ocean (17?±?11 mg m?2) canal over 84 days. Overall, the P flux from all three canal sediments was highest during the first exchange. Miami canal sediments showed the highest P flux (2.4?±?1.3 mg m?2 day?1) compared to WPB (0.83?±?0.39 mg m?2?d?1) and Ocean canal sediments (0.98?±?0.38 mg m?2 day?1). Low P release from WPB canal sediments despite having high TP content could be due to carbonate layers distributed throughout the sediment column inhibiting P release. Equilibrium P concentrations estimated from the sediment core experiment corresponded to 0.12?±?0.04 mg L?1, 0.06?±?0.03 mg L?1, and 0.08?±?0.03 mg L?1 for Miami, WPB, and Ocean canal sediments, respectively, indicating Miami canal sediments behave as a source of P, while Ocean and WPB canal sediments are in equilibrium with the water column. Overall, the sediments showed a significant positive correlation between P release and total P (r?=?0.42), Feox (r?=?0.65), and Alox (r?=?0.64) content of sediments. The contribution of P from the three main canals sediments within the EAA boundary corresponded to a very small portion of the total P load exiting the EAA. These estimates, however, only take into consideration diffusive fluxes from sediments and no other factors such as canal flow, bioturbation, resuspension, and anaerobic conditions.  相似文献   

17.
Seven phosphate-mobilizing pseudomonads were isolated, identified, and characterized in terms of their biofertilizer potential and root-colonizing properties. Pseudomonas protegens (ex-fluorescens) CHA0 was used for comparative purposes. Four isolates (LF-MB1, LF-P1, LF-P2, and LF-P3) clustered with members of the “Pseudomonas fluorescens complex,” whereas the other three (LF-MB2, LF-V1, and LF-V2) clustered with members of the “Pseudomonas putida/Pseudomonas aeruginosa complex.” Assays in buffered liquid growth medium supplemented with tricalcium phosphate enabled the separation of the isolates into two groups: group A (LF-P1, LF-P2, LF-P3, and LF-V1) solubilized P from 151 up to 182?μg?mL?1, and group B (LF-MB1, LF-MB2, and LF-V2) solubilized less than 150?μg?P?mL?1. All isolates displayed acid and alkaline phosphatase activities. With the exception of LF-MB2, all isolates were able to degrade phospholipids from lecithin. Additionally, all isolates exhibited extracellular protease activity, and four isolates produced hydrogen cyanide, two traits that are related to biocontrol of phytopathogens. To study root colonization in non-sterile soil, isolates were doubly tagged with gfp and a tetracycline resistance cassette. After 15?days of competition with the indigenous bacterial flora, all tagged isolates colonized soybean roots at counts ranging from 7.6?×?105 to 1.7?×?107?CFU?g?1. The results indicate that there are already efficient phosphate-mobilizing pseudomonads adapted to agricultural bulk soils under no-till management in Argentina and thus having excellent potential for use as biofertilizers.  相似文献   

18.
The aquatic vascular plant Eurasian watermilfoil (Myriophyllum spicatum L.) was investigated for its potential to take up Cd from nutrient-rich water in a short-term growth and harvest regime. Eurasian watermilfoil plants were grown in and harvested weekly from 0.10M Hoagland nutrient solutions containing concentrations of Cd from 0.04 to 7.63μg Cd mL?1. Dry weights of plants significantly decreas4ed when exposed to 7.63μg Cd mL?1. For both 0.04 and 1.03μg Cd mL?1 treatment the greatest concentration of Cd in plants occurred during the first two weeks. The greatest Cd concentration of Cd in plants for the 7.63μg Cd ML?1 treatment occurred during week one and decreased through week 2. Tissue P concentration in control plants increased over time but did not increase significantly over time when plants were exposed to 0.04 and 1.03μg Cd mL?1 levels. Tissue P concentration decreased over time when plants were exposed to 7.63μg Cd mL?1. Stem length, root dry weights, and root number significantly increased over time in control plants and in those exposed to the 0.04 and 1.03μg Cd mL?1 treatments. Plants treated with 7.63μg Cd mL?1 did not grow. These results suggest that Eurasian watermilfoil would be useful for absorbing Cd from nutrient-rich water when the solution concentration was in the range of 0.04 to 7.63μg Cd mL?1. However, in solutions having the highest concentration of Cd, the harvest regime would have to sustain plant vigor, avoid tissue Cd loss, and realize maximum uptake of Cd from solution.  相似文献   

19.
Aljustrel mining area is located in the Iberian Pyrite Belt, one of the greatest concentrations of massive sulphide deposits that extends from Lousal (Portugal) to Aznalcóllar (Spain). The surrounding streams, Roxo, Água Azeda and Água Forte, are influenced by the erosion of the tailing deposits and the input of acid mine drainage (AMD) from the abandoned Aljustrel pyrite mines, recently reopened in 2007. The purpose of this study was to understand how these adverse conditions influenced the stream sediments, water quality and periphytic diatom communities and establish the pre-restoration local conditions to judge the success of rehabilitation program now under way. For stream sediments, the highest metal concentration samples were found at sites F, G and H. Arsenic, Cu, Fe, Pb and Sb detected concentrations, generally exceeded the probable effect concentration values reaching level 4: the highest toxicity level. In surficial water samples of AMD affected sites (F, G and H), low pH values (1.5 to 3.5) and high metal concentrations of As (6,837 μg L?1), Cd (455 μg L?1), Cu (68,795 μg L?1), Fe (1,262,000 μg L?1), Mn (19,451 μg L?1), Pb (136 μg L?1), and Zn (264,377 μg L?1) were found. In these sites, the diversity index (H′) for diatoms was low (0.6 to 2.8) and the dominant taxa were Eunotia exigua (site F, 33.5%) and Pinnularia acoricola (abundances in sites: F, 86.8%; G, 88.5%; and H, 91.1%). In opposition, in less AMD impacted, H′ was high (1.5 to 4.6) and low metal concentrations and high pH were found. Achnanthidium minutissimum was the dominant taxon in (abundances in sites: A, 76.1% and B, 24.39%). Canonical correspondence analysis showed that spatial variation due to mine influence was more important than seasonal variation, which did not show any pattern.  相似文献   

20.
Abstract

Phytotoxicity, due to chromium [Cr (VI)] additions from low to very high levels in a swell–shrink clayey soil (Haplustert), in maize and spinach was studied in a pot culture experiment. Six levels of Cr (VI) (0, 5, 10, 25, 50, and 75 mg kg?1 soil) for maize and five levels for spinach (0, 2, 5, 10, and 25 mg kg?1 soil) were applied singly and in combination with two doses (0 and 20 t ha?1) of city compost. At levels of more than 75 mg Cr (VI) kg?1 soil for maize there was virtually no growth after germination, whereas 25 mg Cr (VI) kg?1 soil hindered the germination of spinach crop. Initial symptoms of Cr (VI) toxicity appeared as severe wilting of the tops of treated plants. Maize plants suffering from severe Cr (VI) toxicity had smaller roots and narrow brownish red leaves covered with small necrotic spots. In spinach, severe chlorosis was observed in leaves. Higher levels of Cr (VI) inhibited the growth and dry‐matter yield of the crops. However, application of city compost alleviated the toxic effect of Cr (VI). The concentration of Cr (VI) in plant parts increased when Cr (VI) was applied singly but decreased considerably when used in combination with city compost. There was evidence of an antagonistic effect of Cr (VI) on other heavy‐metal (Mn, Cu, Zn, and Fe) concentrations in plant tops. Thus, when Cr (VI) concentration increases, the concentration of other beneficial metals decreases. Chromium (VI) concentration in maize roots ranged from traces (control) to 30 mg kg?1and were directly related to soil Cr (VI) concentration. At 25 mg Cr (VI) kg?1 soil, yield of maize was reduced to 41% of control plants, whereas in spinach, 10 mg Cr (VI) kg?1 soil caused a 33% yield reduction. Experimental results revealed that the maize top (cereal) is less effective in accumulating Cr (VI) than spinach (leafy vegetables). Laboratory studies were also conducted to know Cr (VI) sorption capacity of a swell–shrink clayey soil with and without city compost, and it was found that Cr (VI) sorption reaction was endothermic and spontaneous in nature.  相似文献   

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