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1.
The growth rates of two diatoms, acidophilic Asterionella ralfsii and circumneutral A. formosa, were differentially affected by varying pH, Al, and EDTA in chemically defined media. Free Al ion concentration increased as pH and EDTA concentration decreased. Free trace metal ion concentration decreased as EDTA levels increased but increased by orders of magnitude upon addition of Al. pH had an overriding species specific effect on growth rate; at low pH A. ralfsii had higher growth rates than A. formosa and vice versa at high pH. For both species higher EDTA levels depressed growth rates. Moderate additions of Al generally resulted in growth stimulation. The growth rate stimulations, especially at 200 and 400 μg L?1 Al additions, correlate to increases in free trace metal ion concentrations. The EDTA-AI interaction effects on growth rate were both pH and concentration dependent: at pH 7 both species were stimulated by addition of Al at all EDTA levels (except A. ralfsii at 5.0 mM EDTA and A. formosa at 0.5 mNM EDTA); at pH 6 Al addition either stimulated or had no effect on the growth rates of both species (except at low EDTA and high Al levels); at pH 5 A. formosa did not grow and additions of 200 μg L?1 Al stimulated growth of A. ralfsii. It is likely that the effect of pH, Al, and EDTA on speciation of essential or toxic trace metals affects growth rates of these diatoms in a species specific manner.  相似文献   

2.
We examined the effect of TiO2 nanoparticles (NPs) on the growth of maize and soybean plants and associated soil microbial communities. Plants were grown in a greenhouse, and low levels of undoped or nitrogen-doped TiO2 NPs were applied. Plant growth and nutrient content were determined, and effects of NPs on composition of soil microbial communities were examined using terminal restriction fragment length polymorphism analysis (TRFLP) of rDNA. We found no significant effects of TiO2 NPs on plant growth, nutrient content, or the composition of bacterial communities within the rhizosphere. However, arbuscular mycorrhizal fungal communities were affected by application of undoped and nitrogen-doped TiO2 NPs. This observation may be partially attributed to the small but significant TiO2 NP uptake levels in the root tissues of both plants. Our results suggest that even low concentrations of TiO2 NPs may influence some important groups of soil microbes, such as mycorrhizal fungi, but changes in the composition of microbial communities may not affect plant growth under conditions of adequate moisture and nutrients.  相似文献   

3.
The acute toxicity of commercial herbicide, Paraquat was determined by 96-hr static bioassay on the freshwater chlorophytes Scenedesmus dimorphus (Trup.) Kuetz., Scenedesmus quadricauda (Trup.) de Brebisson and Ankistrodesmus falcatus (Cord) Ralfs. The 96-hr EC50 values of Paraquat for reducing growth and metabolic products of the three algae were determined. The number of days required for cell division increased with increasing Paraquat concentration. The three algae and their test parameters respond differently to Paraquat. Scenedesmus dimorphus was the most susceptible alga and the chlorophyll a was the most sensitive response parameter. On the other hand, the dry weight of the test algae was the most resistant parameter. It was observed that Paraquat has inhibitory effect on the primary producers.  相似文献   

4.
Growth and vigor of trees show considerable variations in young teak plantations in Benin (Vertisols) as well as in Liberia (Ferralsols). Differences in growth are mainly related to topsoil acidity and the foliar Ca-status in Liberia. In Benin, waterlogging (followed by root decay) reduces the Mg-, K- and N-uptake. In addition, growth on the Vertisols is limited by a low KEX/CEC-ratio of usually <1%.  相似文献   

5.
Nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) were compared for their ability to solubilize Pb from a highly-contaminated (PbT 21%) soil collected from a battery recycling facility. For chelant concentrations below 0.04 M (representing a 1:1 chelant-to-PbT molar ratio), EDTA released 10 to 30% more Pb than NTA. NTA-to-Pb T ratios greater than 1:1 reduced Pb recovery because of readsorption of Pb(NTA)2 4? onto positively-charged oxide soil components at pH < 8.5. For the EDTA system, however, complexation completely bound all coordination sites of Pb and EDTA, leaving no functional groups available for surface adsorption. Thus, Pb recovery progressively increased with higher EDTA concentrations, although the additional Pb release with each EDTA increment became smaller. For pH < 5 and EDTA/Pb of 2:1, Pb recovery exceeded 90%. The addition of 0.5 M NaC1O4 enhanced Pb recovery by EDTA for pH 5 to 12, but substantially suppressed recovery by NTA for pH < 11. Because Pb release by NTA was diminished by high ionic strength and chelant-to-metal ratios, NTA may be limited as a soil washing reagent. Stronger complexation and consistent Pb desorption behavior by EDTA favors its use.  相似文献   

6.
The common belief that the sensitivity of plants to Ge is evidence for a Si requirement has been examined experimentally using barely, wheat, cucumber and radish cultivars. All 4 test plants were inhibited by Na2GeO3 (metagermanate) at 1 mM or less, including germination, shoot height, root length, and first leaf growth in barley and wheat. The application of Na2SiO3 (metasilicate) counteracted Ge-inhibition only in barley. Further, only barley growth was stimulated by the application of Na2SiO3. Necrotic lesions were characteristic of Ge-toxicity only in barley leaves, and were reduced when Na2SiO3 was supplied.  相似文献   

7.
The objectives of this study were to determine and to reduce phytotoxicity of two industrial effluents. Phytotoxicity of the treated and untreated samples was determined using millet seed germination test. The results of this and other studies showed that the test was reproducible and useful for effluent toxicity determination. Effluent sample I was from an industrial wastewater pretreatment plant and sample II was from a specialty chemical industry. Sample I was weakly acidic and sample II was alkaline. pH adjusted to 7 to 8 was found to have no effect in phytotoxin removal. Granular and powdered activated carbon effectively reduced phytotoxicity. Amberlite XAD-4 (nonionic polymeric adsorbent) and cation exchange resin had a partial effect. Anion exchange resin, silica gel, Sephadex G-75, and starch xanthate had no effect.  相似文献   

8.
Contamination of the Spring River in southwest Missouri by 2,3,7,8-tetrachlorodibenzo-p -dioxin (TCDD) is believed to result from several well-defined point source waste disposal sites. Analyses of 31 fish samples and samples of crayfish, mussels, other aquatic invertebrates, and sediments collected in 1981-1983 demonstrated a rapid decline in TCDD levels in biota both upstream and downstream of the area of contamination and are believed to indicate a continuing, long term input of TCDD into the river. Mean concentrations of TCDD 0.5 km downstream from the area of contamination were 38 parts per trillion (pptr) in whole fish and 20 pptr in fish fillet; mean concentrations beyond 14 km downstream were below 4 pptr in both whole fish and fillets. Caged mussels (65 day exposure) did not accumulate TCDD (detection limit, 10 pptr). High fish consumption by local sportsmen may indicate maximum permissible concentrations of less than 5 pptr. in fish fillets.  相似文献   

9.
The short term acute toxicity of potassium chromate, potassium dichromate and chromium sulphate has been compared in a simple microbial bioassay. The test parameters were, decrease in viability, genotoxicity and metal uptake. The LC50 values of Cr(III), dichromate Cr(VI) and chromate Cr(VI) for Escherichia coli were 16, 10 and 1.2 μg mL?1, respectively. Among the test substances potassium chromate was most toxic and showed no bioaccumulation while potassium dichromate was less toxic but resulted in significant bioaccumulation. Chromium sulphate was least toxic. As evident from loss of plasmid, genotoxicity was exhibited only by Cr (VI).  相似文献   

10.
Greenhouse soils are regularly treated with metham-sodium, which in soil is quickly transformed to the fumigant methyl isothiocyanate. An experimental fumigation was carried out in a greenhouse with sandy soil. Data were collected on the behavior of methyl isothiocyanate in soil and its permeation through a film of low-density polyethene (LDPE) covering the soil. This cover was found to be highly permeable to methyl isothiocyanate. When the fumigation of greenhouse soil was simulated with a computation model, the use of LDPE film only appreciably reduced the rate of emission into the air in the first two days. The cumulative emission corresponded to about half of the dosage for some practical situations. It is concluded that dosages should be lower and applied more effectively, and less permeable soil covers should be used.  相似文献   

11.
A protozoological survey was performed to analyze the organisms of the subphylum Sarcodina Schmarda, present in waste stabilization ponds located at Santo Tomás Atzingo, México, from March to December 1981. The amoebae isolated were identified and counted. Several physicochemical parameters were also determined and correlated with the biological data. Thirteen amoebic species were isolated and identified: one definite pathogen, Entamoeba histolytica Schaudinn; three species that have shown pathogenic strains for humans: Acanthamoeba polyphaga Page, Acanthamoeba castellanii Douglas, and Naegleria sp. (Alexeieff) Calkins; two opportunist species: Entamoeba coli (Grassi) Casagrandi and Barbagallo, and Iodamoeba bühschlii (Von Prowazek) Dobell; and seven free-living amoebae: Acanthamoeba astronyxis Ray and Hayes, Amoeba proteus (Pallas) Leidy, Hartmannella exundans Page, Hartmannella vermiformis Page, Pelomyxa palustris Leidy, Vahlkampfia avara Page, and Vahlkampfia russelli Singh. A clear correlation between the number of amoebae and the temperature and alkalinity of the system was found. The removal capacity of the ponds for E. histolytica varied from 30 to 100% during the survey. The amoebae showed a succession in space and time in the system studied.  相似文献   

12.
The influence of NTA, EDTA, STPP, Triton X100, PO inf4 sup3 and NO inf3 sup? on the mobilization of Pb, Cd, Cu, Cr and Mn from sediments of two rivers located in Northern Greece was studied. The release caused by all examined complexing agents was higher in deionized water than either Axios or Aliakmon river water due to the lack of competition of Ca and Mg cations with the heavy metals for the studied complexing agents, and the decrease of ionic strength. From all examined agents NTA and EDTA showed the greater mobilization ability. Copper showed the greater tendency for remobilization by all examined agents, (according to the order: EDTA?NTA, Triton X1004 PO inf4 sup3? > NO inf3 sup3? ?STPP) while Cr and Mn the smallest following the orders: NTA, PO inf4 sup3? >> NO inf3 sup? , Triton X1004 EDTA, STPP and STPP > EDTA > NTA > Triton X 100 ? PO inf4 sup3? NO3, respectively. An increase in mobilization was noticed with an increase of agent concentration and time of shaking.  相似文献   

13.
The coastal dune aquifer, providing drinking water for a large part of the population of the western Netherlands, is recharged by fainfall and artificial infiltration of Rhine water. Chernobyl fall-out has been detected in both water sources. At the Castricum lysimeter station the rainfall-derived water, draining from 2.25 m of unsaturated sandy soil, shows levels of Cs-137 around the detection limit of 20 to 40 mBq kg?1. At this site, the soil itself retained some Chernobyl-derived Cs-137 in the top 10 cm, where a similar quantity of old Cs-137 has also been retained. Penetration of old Cs-137 is deeper (up to 70 cm) under oak vegetation than in the bare soil. In the infiltration channels, fed by Rhine water, the bottom mud contains only Chernobyl-derived Cs nuclides. Radioactivity from Cs-137 is about one tenth of that from natural radioactivity due to K-40. Cesium levels are apparently unrelated to adsorptive properties.  相似文献   

14.
Coliform and faccal coliform were isolated from drinking water samples obtained from tap water (TW) and storage tanks (ST) in Baghdad city. All isolates were identified and tested for their resistance to twelve antibiotics. Bacterial identification revealed that Ent. cloacae and Kl. pneumoniae were the predominant organisms from TW and ST water samples, respectively. Overall, 66% of the isolates from TW and 38% from ST were resistant to one or more of the drugs tested. Ampicillin, Carbenicillin, Cefalotin and Colistin resistance in particular were more frequent among bacterial isolates. The overall frequency of multiple antibiotic resistance among bacterial isolates in TW and ST samples were 47% and 33%, respectively. All bacterial strains isolated from drinking water were sensitive to Rifampicin. Results demonstrated the need for periodical bacteriological examination of drinking water and restriction in the use of antibiotics in this country.  相似文献   

15.
This paper deals with the effect of solvents on the pesticide inhibition of ATPase in the gills and brains of a freshwater teleost Labeo rohita after in vitro treatment with chlordane (an organochlorine pesticide) and MetasystoxR (an organophosphate) pesticide after dissolving in different organic solvents viz. benzene, cyclohexane, cyclopentane, dimethylacetamide (DMA), dimethylformamide (DMF), dimethylsulfoxide (DMS), and acetone/ethanol (1:1) mixture. The inhibitory effect of chlordane was greatly reduced by cyclohexane, cyclopentane and benzene, to a less extent by DMA, DMF, and DMS and to a lesser extent by acetone/ethanol (1:1) mixture. ATPase inhibition by MetasystoxR showed less effect on the inhibition of ATPase activities. Effect on the inhibition of Na+, K+-ATPase was observed to be greater than on Mg++ ATPase in both tissues, but the activity of both the ATPase in gill homogenate was decreased compared to brain homogenate. Choice of solvents can have profound effects on the response of ATPase to chlorinated hydrocarbon pesticides.  相似文献   

16.
The study was carried out on 3 groups of 10 fish, each fed on a different natural labelled food. The preys selected were a crustacean (Gammarus pulex), a midge larvae (Chironomus sp.) and the soft tissues from a snail (Lymnaea stagnalis), which are usually consumed by carp in the natural environment. The contaminated food consumption by the fish resulted in a 60Co maximum transfer factor ranging from 1.2 × 10?2 to 5.1 × 10?2 depending on the food type. These values, and the contamination kinetics indicate that the biomagnification of the radionuclides cannot occur, even over the long term. 60Co depuration from fish was also influenced by the contaminated food type, previously ingested. The lower elimination rate correspond to the higher value of the transfer factor (Gammarus pulex) and inversely (Lymnaea stagnalis).  相似文献   

17.

Purpose

Problems associated with Organochlorine pesticide (OCP)-contaminated soils have received wide attention. To understand the anaerobic biodegradation process constraints, innovative mathematical analysis methods are effective.

Materials and methods

Response surface methodology (RSM) and Tenax TA extraction method combined with the first-three-compartment model were employed to systematically investigate the role of nitrate concentration and bioaccessibility enhancer (methyl-β-cyclodextrin, MCD) in the anaerobic biodegradation of OCPs in contaminated soil.

Results and discussion

The sole addition of either KNO3 or MCD could facilitate the anaerobic biodegradation of OCPs. The highest biodegradation for total OCPs, hexachlorocyclohexanes, endosulfans, and chlordanes were 71.6, 82.1, 68.3, and 55.6 %, respectively, when 20 mM KNO3 and 3.0 % (w/w) MCD were applied simultaneously. As predicted by RSM, the theoretical maximum biodegradation for total OCPs ranged from 60 to 80 % when 20 to 25 mM KNO3 and >2.5 % (w/w) MCD were applied simultaneously. Tenax TA extraction method demonstrated the enhancement of OCP bioaccessibility caused by MCD addition. Changes in the soil microbial activities also suggested the positive effects of adding suitable amounts of KNO3 as a cosubstrate to facilitate the anaerobic biodegradation of OCPs.

Conclusions

The amount of KNO3 and MCD are crucial in influencing OCP biodegradation. RSM was demonstrated to be a powerful tool to estimate and predicting the optimal OCP biodegradation under KNO3 and MCD application simultaneously.  相似文献   

18.
The hydrobiological parameters of the waters in the vicinity of ash slurry and cooling water outfall from Ennore Thermal Power Station located on the shore of Bay of Bengal, Madras were determined. In the outfall site, an increase in mean temperature (35 °C), salinity (3.5%), nitrite ? N (25 μg L?1), ammonia ? N (185 μg L?1), phosphate ? P (1 mg L?1), silicate ? SiO2 (1.65 mg L?1), chlorophyll a (21.1 mg m?3), respiration (76% of gross production), suspended solids (3.84 g L?1), BOD (3.65 mg O2) and decrease in pH (8.1), dissolved oxygen (DO) (5.5 mg L?1), nitrate ? N (15 jig L?1), gross production (16.6 Mg C m?3 hr?1) were recorded. Phaeopigment and respiration were inversely related with chlorophyll a and net productivity, respectively. Microbial biomass varied spatially, but was generally low (114.5 jig L?1), at the outfall site. The hydrobiological characteristics of water with high turbidity indicate that the ash slurry and coolant water play a crucial role in a localized area resulting in environmental disturbance. The effect was profoundly influenced by an initial dilution, dispersion, wave mixing and current direction. The ecological relationships between these parameters and their implications in coastal pollution are discussed.  相似文献   

19.
Air pollution and atmospheric deposition by PCBs and organochlorine pesticides (isomers of HCH and p,p′-DDE) were studied at Paris from January 1986 to June 1987. The deposition measured as total (wet plus dry) was also followed during 1986 on two suburban and two rural sites. The distribution of the pollutants between the vapor phase and aerosols was evaluated by sampling air through a glass microfiber filter connected to a Tenax resin cartridge. The study shows that in the atmosphere as in waters of the catchment area of the Seine river, PCBs are the main organochlorine pollutants. Pollution by OCL is of the same order as the one described in literature (mean γ-HCH concentration 1.4 ng m?3) while PCB concentrations in the atmosphere are equal to or higher than those observed in USA and Europe (range 5 to 44 ng m?3). On the average, 93% of the PCBs are in the vapor phase with a composition approximating Aroclor 1242. In aerosols and precipitations the composition is closely related to Aroclor 1254. The total fallout for 1986 was 40 μg m?2 for PCBs and 20 μg m?2 for γ-HCH, rainfall being 611 mm.  相似文献   

20.
The adsorption of phenol, p-chlorophenol and mercuric ions onto activated carbon in fixed beds has been studied. The effects of process variables such as bed height and residence have been studied. The results have been used to predict optimum conditions for the systems based on the C exhaustion rate and the empty bed residence time (EBRT).  相似文献   

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