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1.
Abstract

Hydrogeological investigations have been carried out in rural parts of Guntur district, Andhra Pradesh, India where agriculture is the main occupation. Granite gneisses associated with schists and charnockites are the main lithological formations, which are overlain by black cotton soils. Groundwaters are alkaline, very hard and mostly brackish. Possible sources of fluoride (F?) are weathering and leaching of F?-bearing minerals under the alkaline environment. A high rate of evapotranspiration, longer residence time of waters in the aquifer zone, intensive and longterm irrigation, and heavy use of fertilizers are the supplementary factors to further increase the F? content in the groundwaters. The investigated area has been classified into three types with reference to concentration of F- prescribed for drinking: low-F- (<0.60 mg l?1), moderate-F? (0.60–1.20 mg l?1) and high-F- (>1.20 mg l?1). Forty-five percent of the total groundwater samples belong to the high-F- category. Dental fluorosis is noticed in the region. A groundwater management programme is suggested.  相似文献   

2.
Laboratory experiments were carried out to the influence of different concentrations of copper in feeding and respiratory rates, fecundity and longevity of the marine planktonic copepod Acartia clausi, taken from a polluted and a clean area of the Saronic gulf (Greece). In the range of copper concentrations 0.001 to 0.01 mg l.?1, all tested activities of the animals coming from the clean region seem affected. Feeding acitity, longevity and fecundity showed a progressive reduction from 0.001 to 0.01 mg l.?1 On the other hand oxygen consumption rates showed a continuous increase at the same range of concentrations.The pollution-adapted population of Acartia seems more resistant to sub-lethal copper stress. Although longevity and respiration were affected in all concentrations used (the reaction was of the same kind as for the animals from the clean region), ingestion rate was not affected at 0.001 mg l.?1 decreasing at higher concentrations. The fecundity of the pollution-adapted population is higher than that of the clean area, shows a slight increase at 0.001 and 0.0025 mg l.?1 dropping about to the control animals fecundity level at 0.01 mg l.?1  相似文献   

3.
In a storage reservoir with a hypolimnic volume of 3.5 hm3 the water contains 40 mg/l nitrate. A straw bale of 60 by 20 by 1.5 m was introduced as a reactor. Hypolimnic water having been polluted with a waste product of the fatty acid synthesis (30 … 20% formic, acetic, propionic, butyric and valeric acids) were pumped through it. By the use of a total of 43.8 t fatty acid mixture from June to August an additional oxygen depletion of 14 t O2 is achieved and 49 t NO3? are removed at the same time. The ammonium concentration did not increase, the NO2? concentration, however, rose to 12 … 13 mg/l NO2 at times. The fatty acids were used up save 0.1 mg/l. The increase of the NO2? concentration, of the number of germs and of the iron, manganese and phosphorus back solution due to the controlled anaerobic conditions is the drawback of the process.  相似文献   

4.
Danube river water samples were saturated with mineral oil, and then the primary production (gross) was determined by means of the light-dark bottle method (oxygen) in situ at depths of 0.1… 1.5 m in comparison with untreated samples. Samples were exposed for half a solar day alternately during the first and second half-days. Investigations carried out between March and October for periods of 14 days showed a mean production of 2.56 g · m?2d?1 O2, which was reduced by 36% due to 12.6 mg/l hydrocarbons. Production decreases with the water depth from 6.2 to 0.9 mg · l?1d?1 02, whereas the inhibition by hydrocarbons increases from 31 to 41%.  相似文献   

5.
The geochemical characteristics and the spatial distribution of the fluoride were studied in the soils of Indo‐Gangetic plains using multivariate analysis. The fluoride (F) distribution in soil profiles and surface soil (0–15 cm) samples were studied. It was found that total fluoride (TF) in the profiles ranged from 248 to 786 mg kg?1 with a mean of 515.1 mg kg?1 whereas CaCl2 extractable soluble fluoride (FCa) was found to be in the range of 1.68 to 99.1 mg F kg?1 soil. On the other hand, in surface soils, the TF and FCa ranged from 118 to 436 mg kg?1 with a mean of 251.2 mg kg?1 and 1.01 to 5.05 mg kg?1 with a mean of 2.12 mg kg?1, respectively, in the study area. The principal component analysis revealed that the natural weathering of fluoride bearing rock and minerals, various ion‐exchange and dissolution processes in the soil, alkalinity, sodium adsorption ratio, calcium (Ca), magnesium (Mg), and clay contents of the soil are responsible for high fluoride occurrence in the area. The fluoride contamination index developed by using these factors could explain more than 76% variance of F contamination due to FCa in soils. The interpolated kriged map of FCa in surface soil indicated a distinct loop of 1.0–2.0, 2.0–3.0, 3.0–4.0, and >4.0 mg kg?1.  相似文献   

6.
自2005年以来,程海水体的化学需氧量(COD)持续升高,而生化需氧量(BOD)却维持不变,高锰酸盐指数(COD_(Mn))升高也较缓慢.为研究程海COD持续升高的原因,选取程海水体中具有代表性的无机阴离子(Cl~-、F~-、S~(2-)、HCO_3~-)和溶解性有机质(DOM)中不同浓度的胡敏酸(HA)、富里酸(FA)和商品化腐殖酸(SHA),研究其对COD和COD_(Mn)测定的影响,探讨Cl~-和DOM共同存在下对COD测定的影响.结果表明:程海水体中Cl~-浓度对COD存在显著影响,产生的COD值为5.42 mg/L,S~(2-)、F~-和HCO_3~-对COD影响较小;各离子对COD_(Mn)的影响很小;不同浓度梯度的HA、FA和SHA与COD测定结果呈显著线性相关,氧化1 mg C HA、FA和SHA所产生的COD值分别为2.164、1.964和2.362 mg;氧化1 mg C HA和FA所产生的COD_(Mn)值分别为0.646和0.344 mg;DOM对COD测定值的影响显著大于对COD_(Mn)测定值的影响;且一定浓度Cl~-的存在增强了FA与HA对COD测定的影响.该研究为进一步阐明程海COD逐步升高,COD_(Mn)值缓慢升高的内在原因奠定了基础.  相似文献   

7.
Chemical speciation of vanadium is important to understand the true nature of this element in the environment as well as its biochemical pathways. Sample pretreatment, preparation, and chemical speciation methods were applied for vanadium in coal bottom ash here. Two‐stage microwave acid digestion was used to preparation of samples. Determination of vanadium was performed using inductively coupled plasma‐optical emission spectrometry (ICP‐OES). Speciation of vanadium was carried out using a seven‐step sequential extraction procedure of the coal bottom ash each releasing species of vanadium: Water soluble, exchangeable, carbonate, reducible, oxidizable, sulfide, and residual fractions. Total vanadium concentration in the coal bottom ash is 701 mg kg?1 d.w. The most abundant form of vanadium in coal bottom ash is residual fraction of vanadium (196 mg kg?1 d.w.). Relative abundances of the remaining vanadium fractions in coal bottom ash are as follows: Reducible (176 mg kg?1 d.w.) > sulfide (176 mg kg?1 d.w.) > carbonate (85 mg kg?1 d.w.) > oxidizable (50 mg kg?1 d.w.) > water soluble (10.6 mg kg?1 d.w.) > exchangeable (9.0 mg kg?1 d.w.).  相似文献   

8.
The behaviour of the herbicide bromoxynil (3,5-dibromo-4-hydroxybenzonitrile), labelled with 82Br, is investigated in an activated sludge plant on the laboratory scale with municipal wastewater. Only 5% of bromoxynil present in a concentration of 5 mg/l are degraded after preadaption of activated sludge for some weeks. The known hydrolysis products 3,5-dibromo-4-hydroxybenzamide and 3,5-dibromo-4-hydroxybenzoic acid were identified as degradation products. In addition, 1.9±0.9% of the quantity of 82Br appeared in the solution as Br? by debromination. Moreover, a pronounced adsorption of the active substance on activated sludge occurs. Its activity amounts to about 130% of the initial activity of the solution.  相似文献   

9.
In the dimict lake Arend (5.1 km2, 146 hm3, 49.5 m zmax), nitrogen is production-limiting with concentrations below the detection limit during the production period. Phytoplankton achieves biomasses of up to 18 mg/l fresh matter, essential contributions being made by Aphanizomenon with 2 mg/l and Anabaena with up to 10 mg/l. Nitrogen fixation was measured by the ethine reduction technique (acetylene reduction) during periods of the occurrence of heterocystforming Cyanophyceae and achieved peak values up to 6.59 μg N2 · h?1 · l?1 or 14.87 m?2 · h?1 g N2 · m?2 · h?1. The rates of fixation show a safe correlation with the biomass of heterocyst-containing Cyanophyceae (r = 0.88), their development beginning at values below the N : P-ratio of 2.66.  相似文献   

10.
V. Chaplot  O. Ribolzi 《水文研究》2014,28(21):5354-5366
Dissolved organic carbon (DOC) is a key component of the global carbon cycle, but, to date, large uncertainties still exist on its source and fate in first‐order streams. In a 23 ha rangeland and steep‐slope headwater of South Africa, our aim was to quantify the contribution of overland flow (OF), soil water (SW) and ground water (GW) to DOC fluxes (DOCF), and to interpret the results in terms of DOC sources and fate. The average 2010–2011 DOC concentration (DOCC) at the catchment outlet was 4.7 mg C l?1 with a standard error of ±2.5 mg C l?1, which was significantly lower than in SW (15.2 ± 1.6 mg C l?1) and OF (11.9 ± 0.8 mg C l?1), but higher than in GW (2.3 ± 0.6 mg C l?1). Based on end‐member mixing using Si and Na concentration in the water compartments, the average SW contribution to DOCF was 66.4%, followed by OF (30.0%) and GW (3.6%). The resulting estimated DOCF at the catchment outlet was 8.05 g C m2 y?1. This was much higher than the observed value of 2.80 g C m2 y?1, meaning that 5.25 g C m2 y?1 or 65% of the DOC is lost during its downslope and/or downstream transport to the catchment outlet. Complementary investigations revealed that the DOCC in SW dropped from 15.2 ± 1.6 to 2.6 ± 0.3 mg C l?1 during its downslope transport to the river system, which corresponded to a net loss of 5.10 g C m2 y?1, or 97% of the catchment DOC losses. These results on DOC sources and potential fate in headwaters are expected to improve our understanding of the impact of hydrology on the global C‐cycle. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

11.
Static bioassay acute toxicity tests of Zinc, Copper and Mercury were conducted to determine the median lethal concentrations (LC50s) of a freshwater teleost Channa marulius (HAM .) The 96 h LC50 and 95% confidence limits for Zn2+ were 25.61 (24.13 … 27.12) mg/l; 0.90 (0.80 … 1.038) mg/l; for Cu2+ and 0.314 (0.257 … 0.371) mg/l for Hg2+. However, these values decreased at 240 h of exposure and were: 21.09 (18.29 … 24.60) mg Zn2+/l; 0.66 (0.568 … 0.841) mg Cu2+/l; and 0.131 (0.103 … 0.158) mg Hg2+/l. The relative potency ratio of Zn/Hg, Zn/Cu and Cu/Hg suggests that fish were most sensitive to Hg, followed by Cu and Zn ions. The acute toxicities of mixtures of Zn2+?Cu2+; Zn2+?Hg2+, Cu2+?Hg2+ and Zn2+?Cu2+?Hg2+ up to 48 h of exposure were also investigated. The additive index and ranges for Zn2+?Cu2+ were ?0.241 (-0.577 … 0.054); 0.056 (-0.269 … 0.475) for Zn-Hg; 0.285 (-0.043 … 0.718) for Cu-Hg; and -0.542 (-1.215 … 0.005) for Zn-Cu-Hg. All the mixtures tested showed a greater than additive toxicity because index ranges overlapped zero.  相似文献   

12.
The effects of short-term exposure to tetravalent platinum on survival, opercular movement and post-treatment growth of coho salmon fry (Oncorhynchus kisutch) was investigated. Employing a static water acute toxicity bioassay with platinum as PtCl42HCl·6 H2O, at 8.5±0.2°C, and a water hardness of 55.9±3.5 mg l.?1 (as CaCo3), the 24, 48, and 96-h LC50 values were 15.5, 5.2, and 2.5 mg Pt4+ l.?1 respectively.Rates of opercular movement for fish exposed to platinum increased with increasing concentrations to a level of 1.0 mg l.?1. No further significant increases were evident above this level. Hypoactivity of fish exposed to 0.3 mg l.?1 and higher was evident during the acute toxicity bioassay and much of the post-treatment study. Post-treatment rate of growth for fish exposed to sublethal concentration of platinum for 96 h was less than that of the controls.All organs examined histopathologically were within normal ranges with the exception of the gills and olfactory organ. Lesions in fish exposed to concentration of 0.3 mg l.?1 and higher were characterized by branchial epithelial hypertrophy and hyperplasia, and necrosis of olfactory epithelial cells.  相似文献   

13.
The increased accumulation of toxic pharmaceuticals and personal care products in the environment is a concern of worldwide relevance. Efficient technologies are needed to mitigate the level of such chemicals in natural waters. The suitability of multi‐walled carbon nanotubes (MWCNTs) to remove aqueous triclosan (a widely used anti‐microbial agent) was investigated in the present study. Tested operational parameters included the pH (3.0–11.0) value and the ionic strength (10?3, 10?2, and 10?1 M). Kinetic and thermodynamic studies were conducted at different initial concentrations (4, 8, and 10 mg/L) and temperatures (288, 298, and 308 K). Results showed higher triclosan adsorption at pH 3.0 (157.7 mg/g) than at pH 11.0 (103.9 mg/g). With an increase of ionic strength from 10?3 to 10?2 M, the adsorption capacity increased from 136.1 to 153.1 mg/g and from 80.8 to 105.8 mg/g at pH 3.0 and 10.0, respectively, while further increase of ionic strength to 10?1 M slightly reduced the triclosan adsorption to 149.9 and 94.7 mg/g due to the aggregation of MWCNTs. The Polanyi–Manes model (PMM) provided a best fitting of adsorption isotherms to the experimental data, and the kinetic process was well described by the pseudo second‐order kinetic model. The calculated thermodynamic parameters (ΔH0 = ?88.08 kJ/mol, ΔS0 = ?173.38 J/mol K) suggested that the adsorption of triclosan is spontaneous and exothermic in nature. The findings of the present work have significant implications for the removal of triclosan from aqueous solution with MWCNTs.  相似文献   

14.
The present paper proposes the application of multiwalled carbon nanotubes (MWCNTs) as a solid adsorbent for selective separation/preconcentration of silver(I) in water samples prior to flame atomic absorption spectrometry. The procedure is based on the solid phase extraction of Ag(I)–2‐mercaptobenzothiazole chelate on MWCNTs. The elution step is carried out with 5 mL of 2 mol L?1 HNO3 in acetone solution at a flow rate of 1.0 mL min?1. The influences of the various analytical parameters including pH of the solution, eluent type, sample volume, flow rates of eluent, matrix ions were investigated for optimization of the presented procedure. Tests of addition/recovery for analyte ion in real samples were performed with satisfactory results. Preconcentration factor and limit of detection for Ag(I) were 160 and 0.21 µg L?1, respectively. The synthesized MWCNT exhibited excellent stability in eluent solution and its adsorption capacity was 5.4 mg of silver per gram of sorbent. The proposed method was successfully applied to trace silver determination in a variety of environmental water samples.  相似文献   

15.
Chemical studies have been carried out on a number of water wells from the Dibdiba Formation northeast of Kuwait. Water salinity of this formation ranges between 3,300 mg/l to 7,000 mg/l, increasing with depth. The water entrapped in Dibdiba Formation is mainly sodium chloride type which can be differentiated into three different groups according to the ranges of concentration of the main cations and anions. These groups are: (3331113) sodium chloride water type in which Cl > Na, group (3333113) sodium chloride water type in which Na > Cl. In both groups the sequence of dominant cations is Na > Ca > Mg. Group (3333111) sodium chloride water type has Na > Cl and the sequence of dominant cations is Na > Mg > Ca. Chemical ratios of Ca/Mg, Na/Cl, and C1/HCO3 were worked out for Dibdiba ground water. The ratio of Ca/Mg Dibdiba Formation ranges from 0.4 to 8.58, the ratio of Na/Cl ranges between 0.98 to 1.33, and the ratio of C1/HCO3 is 232. A plot of chemical analysis on a trilinear diagram shows that Dibdiba Formation ground-water chemical properties are dominated by alkalies (Na > Ca) and strong acid (Cl > SO4). Water chemistry may reflect the history of the flow path, indicating regional flow as shown by increasing Na+, Cl-, SO4 and where Ca+, Mg+ achieve equilibrium.  相似文献   

16.
The kinetics of conversion of iron(III) (hydr)oxides to ferrous iron mediated by fulvic acid have been investigated in order to improve the understanding of the redox cycling of iron at the oxic-anoxic boundary in natural waters. Under the conditions similar to natural waters, fulvic acid is able to reduce the iron(III) (hydr)oxide. The kinetics of the reaction depend on the reactivity of iron(III) (hydr)oxides and the reducing power of the fulvic acid. The rate of reaction is 60 nm/h obtained under following conditions: total concentration of Fe(III) 1.0 × 10–4 M, pH 7.5, fulvic acid 5 mg/L. The rate is considered as a net result of reduction and oxidation in the > FeIII-OH/Fe(II) wheel coupled with fulvic acid. In a real natural water system, reductants other than fulvic acid may be of importance. The results obtained in the laboratory, however, provide evidence that the Fe(OH)3(s)/Fe(II) redox couple is able to act as an electron-transfer mediator for the oxidation of natural organic substances, such as fulvic acid by molecular oxygen either in the absence of microorganisms or as a supplement to microbial activity.  相似文献   

17.
The hyporheic zone of riverbed sediments has the potential to attenuate nitrate from upwelling, polluted groundwater. However, the coarse‐scale (5–10 cm) measurement of nitrogen biogeochemistry in the hyporheic zone can often mask fine‐scale (<1 cm) biogeochemical patterns, especially in near‐surface sediments, leading to incomplete or inaccurate representation of the capacity of the hyporheic zone to transform upwelling NO3?. In this study, we utilised diffusive equilibrium in thin‐films samplers to capture high resolution (cm‐scale) vertical concentration profiles of NO3?, SO42?, Fe and Mn in the upper 15 cm of armoured and permeable riverbed sediments. The goal was to test whether nitrate attenuation was occurring in a sub‐reach characterised by strong vertical (upwelling) water fluxes. The vertical concentration profiles obtained from diffusive equilibrium in thin‐films samplers indicate considerable cm‐scale variability in NO3? (4.4 ± 2.9 mg N/L), SO42? (9.9 ± 3.1 mg/l) and dissolved Fe (1.6 ± 2.1 mg/l) and Mn (0.2 ± 0.2 mg/l). However, the overall trend suggests the absence of substantial net chemical transformations and surface‐subsurface water mixing in the shallow sediments of our sub‐reach under baseflow conditions. The significance of this is that upwelling NO3?‐rich groundwater does not appear to be attenuated in the riverbed sediments at <15 cm depth as might occur where hyporheic exchange flows deliver organic matter to the sediments for metabolic processes. It would appear that the chemical patterns observed in the shallow sediments of our sub‐reach are not controlled exclusively by redox processes and/or hyporheic exchange flows. Deeper‐seated groundwater fluxes and hydro‐stratigraphy may be additional important drivers of chemical patterns in the shallow sediments of our study sub‐reach. © 2015 The Authors. Hydrological Processes Published by John Wiley & Sons Ltd.  相似文献   

18.
This study investigates the influence of Ca2+ and Mg2+ on the removal of F? by magnesium potassium phosphate (MPP) from water. The kinetic experiments reveal that the F? concentration decreased from 3.5 to 3.31 mg L?1 in a single (F?) system and to 1.45 mg L?1 in a ternary system (F?, Ca2+, and Mg2+) after 1 min, respectively. Thus, the F? removal efficiencies are found to increase by about 53% with the co‐active effect of Ca2+ and Mg2+ in the solution. Moreover, Ca2+ and Mg2+ are almost completely removed in the F?, Ca2+, and Mg2+ system. According to the pseudo‐first‐order modeling, the rate constants k for F?, Ca2+, and Mg2+ are 0.00348, 0.0106, and 0.0159 min?1 respectively; thus, Mg2+ > Ca2+ > F?. In the ternary system, the removal efficiencies are 53.29–66.03% for F?, 99.99–100% for Ca2+, and 87.21–95.19% for Mg2+ with initial pH 5–10. The removal efficiencies of F? increases with increases in initial concentrations of F?, Ca2+, and Mg2+. The removal of F? is governed by two routes: 1) adsorption by electrostatic interactions and outer sphere surface complexation; 2) co‐precipitation with Ca3(PO4)2, CaHPO4, Mg3(PO4)2, and Mg(OH)2.  相似文献   

19.
The analytical measurement technique presented consists of the ADM 300 flow stream system with two-channel operation and the AE 4 evaluation unit for four-channel operation. Selected parameters for important components of water quality are presented, such as those used in preferred combined methods in the practice of the laboratories of water and wastewater monitoring. The following components with detection limits in mg/l are concerned: ammonium 0.04, nitrite 0.07, nitrate 0.32, Norg. 0.35, o-PO4 0.02, total PO4 0.08, SiO2 0.08, sum of cations 0.79 mmole/l; Mn 0.02, Fe 0.34, Cl? 15.4 and UV-absorbance 0.01 cm?1. The detailed examination of the techniques on samples of waters has proved a statistically secured agreement of the analytical results with the results of the standard methods, with the simultaneous increase of the number of analyses by 100 … 300= and a saving of chemicals of 80= compared with the manual analysis. The device system has the interfaces required for the further data processing by means of PC. The boundary conditions for the application of this technique, especially the necessary lot sizes and laboratory organization, are referred to.  相似文献   

20.
Biological Degradation of 2,4-Dinitrotoluene in a Continuous Bioreactor and Kinetic Studies Experimental results on the aerobic biological degradation with complete mineralization of 2,4-dinitrotoluene (2,4-DNT) are presented. A culture of Pseudomonas sp. DNT from Spain and Nishino was used. The degradation was examined with batch cultures for the determination of kinetic and stoichiometric coefficients. Further experiments were carried out with a continuous culture in a fixed-bed reactor with recirculation in order to obtain high degradation rates. The reactor was packed with ceramic Raschig rings (55 mL) and had a liquid reaction volume of 160 mL. The minimal salt media from Spanggord et al. with and without (NH4)2S)4 as nitrogen source was used as substrate. 2,4-DNT was the sole source of carbon and energy. From batch experiments a yield coefficient YB/S = (0.30 ± 0.05) g g?1 was calculated from a mass balance of the elements. This result was confirmed by calculations using literature data. Fitting the experimental data to the Monod equation, μmax = 0.1 h?1 and KS = 0.01…0.03 mmol L?1 were obtained. It was demonstrated by batch experiments that 2,4-DNT is not only used as the source of carbon and energy but also as the nitrogen source. In the fixed-bed reactor, a degradation of 92…97% was reached with a maximal 2,4-DNT load of 95 mg L?1 h?1. The rate of continuous degradation could be described by a pseudo-first-order reaction (k = 9.73 h?1). The complete mineralization of 2,4-DNT was verified by the measurement of DOC and the formed nitrite and nitrate. The formed nitrite was nitrified simultaneously. It was demonstrated by these experiments that large scale biological treatment of industrial effluent containing 2,4-DNT may be successful.  相似文献   

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