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1.
Sorption by humic acids is known to modify the bioavailability and toxicity of metals in soils and aquatic systems. The sorption of cadmium(II) and copper(II) to two soil humic acids was measured at pH 6.0 using ion-selective electrode potentiometric titration at different temperatures. Sorption reactions were studied with all components in aqueous solution, or with the humates in suspension. Adsorption reactions were described using a multiple site-binding model, and a model assuming a continuous log-normal distribution of adsorption constants. Adsorption of Cu 2+ was more favourable than adsorption of Cd 2+. The log-normal distribution model provided the closest fit to observations and allowed parameterisation of adsorption data using a mean adsorption constant (log K μ). Sorption of Cd 2+ to dissolved humic acids increased slightly in extent and sorption affinity with increasing temperature, but the effect was small (log K μ 2.96–3.15). A slightly greater temperature effect occurred for sorption of Cd 2+ to solid-phase humic acids (log K μ 1.30–2.08). Sorption of copper(II) to both aqueous- and colloidal-phase humates showed more pronounced temperature dependence, with extent of sorption, and sorption affinity, increasing with increasing temperature (log K μ 3.4–4.9 in solution and 1.4–4.5 in suspension). The weaker adsorption of Cd 2+ than Cu 2+, and smaller temperature effects for dissolved humates than suspended humates, suggested that the observed temperature effects had a kinetic, rather than thermodynamic, origin. For any metal-to-ligand ratio, free metal ion concentration, and by inference metal bioavailability, decreased with increasing temperature. The consistency of the data with kinetic rather than thermodynamic control of metal bioavailability suggests that equilibrium modelling approaches to estimating bioavailability may be insufficient. 相似文献
2.
The acute toxicity of monodispersed 6 nm and <100 nm poly-dispersed copper oxide nanoparticles toward Daphnia magna was assessed using 48 h immobilization tests. CuSO 4 was used as a reference. Four different exposure conditions were tested, to study whether the toxicity of the nanoparticle suspensions changed in a way similar to what is known for dissolved Cu: first in ISO standard test conditions (pH 7.8), second with slight acidity (pH 6.5), third in the presence of citric acid, and fourth in the presence of humic acid. For all four exposure conditions, the toxicity of Cu employed in the three forms followed the same sequence, i.e., CuSO 4 > monodispersed 6 nm CuO ? poly-dispersed CuO. The toxicity of all Cu forms decreased from pH 6.5, ? pH 7.8, > pH 7.8 + citric acid, to ? pH 7.8 + humic acid. This pattern is in agreement with concentrations of Cu 2+ calculated using the equilibrium model MINTEQ. These findings show that the acute toxicity of copper oxide nanoparticles is governed by test water composition and the chemical species Cu 2+. 相似文献
3.
The effects of copper (Cu 2+) on photochemical efficiency, cellular viability and total phenolic content in Prosopis glandulosa leaves were evaluated after 4, 8 or 12 h exposure to 0.1, 10 or 100 mM Cu 2+ using the tissue tolerance test. The results showed that significant reductions ( p<0.003) of photochemical efficiency in P. glandulosa leaves were found after 8 h exposure to 100 mM Cu 2+ compared with controls leaves. The results also showed a significant increase ( p<0.05) on electrolyte leakage values in P. glandulosa leaves after 4 h exposure to 100 mM Cu 2+ compared with control leaves. Total phenolic content in P. glandulosa leaves only differed significantly when exposed 12 h to the highest concentration of Cu 2+. These results suggest that Cu 2+ can produce reactive oxygen species that may form hydroxyl radicals that damage proteins and lipids, which in turn causes loss of integrity and reduce photochemical efficiency of leaves. In conclusion, the photochemical efficiency and cellular viability analyses can be used as useful physiological tools to assess early changes in photosynthetic performance of P. glandulosa in response to copper pollution. 相似文献
4.
The interaction of Zn and Cu with dissolved organic matter (DOM) is a significant physicochemical process affecting their sorption as well as mobility in soil. The objective of this study was to examine the influence of DOM from corn straw on the sorption of Zn and Cu by loess through batch adsorption technique. The sorption isotherms of Zn and Cu could be well described by the Freundlich equation, and the partition distribution coefficient ( k) in the presence of DOM was reduced by 86% for Zn and 58% for Cu, as compared to the control receiving no DOM, suggesting that DOM had a stronger inhibitory effect on Zn sorption than that of Cu. In addition, the sorption of metal increased with an increase in pH for loess, with maximum inhibition on metal sorption observed at pH > 7.6 for Zn and pH > 5.5 for Cu in the absence ofDOM but Cu sorption of DOM was suddenly decreased with an increase of pH at pH > 7.9 in the presence of DOM. At a DOM concentration of <200 mg L ?1, sorption of Zn and Cu was reduced by 46% for Zn and 32% for Cu with an increase in DOM concentration. 相似文献
5.
The North Inlet Marsh-Estuarine System Model (NIMES) is a 19-compartment real-time deterministic ecosystem simulation model of intrasystem carbon flow and exchange between an estuary and adjacent coastal water. A complete sensitivity analysis of this model with regard to POM, DOM and nekton annual exchange and annual system net productivity was completed and the functional relationship between these system behaviors and the perturbed parameters were determined by regression techniques. Simulated POM annual exchange between the estuary and the sea was largely controlled by offshore POM concentration, water column respiration and the gross productivity of the marsh and water column flora. Simulated DOM annual estuarine-oceanic exchange was most sensitive to perturbations in the gross productivity and biomass changes in marsh flora and water column microbial DOM uptake. Simulated nekton exchange reflected a sensitivity to migratory behavior and subtidal benthic biomass changes. System annual net productivity as simulated by the model showed a high sensitivity to all model processes which affected component primary production and respiration. From this sensitivity analysis, a scheme is developed to evaluate research needs for further model development for the North Inlet ecosystem. 相似文献
6.
The aim of this study was to assess the toxicity reduction of wastewaster after treatment with fly ash. Fly ash is a waste material which is formed as a result of coal burning in power plants, but has the potential to adsorb heavy metal ions. The present study examined the adsorption capacity of fly ash to adsorb Pb 2+, Cu 2+, and Zn 2+ from waste water under different conditions of contact time, pH, and temperature. Uptake of metal ions by fly ash generally rose with increasing pH. At lower temperatures the uptake of heavy metal adsorption were enhanced. Significant reduction in Pb 2+ (79%), Cu 2+ (53%), and Zn 2+ (80%) content was found after treatment with fly ash of waste water treatment. Using the microtox test toxicity of the effluent was reduced by 75% due to removal of Pb 2+ ion by the fly ash. Data indicated that fly ash generated by power plants may be used beneficially to remove metals from waste water. 相似文献
7.
为评价由酸雨、酸性矿山排水等环境污染导致的水体酸化及水体重金属联合作用对水生生物的生态毒性效应,研究了不同pH值(pH=3、4、5、6、7和7.8)条件下Cu2+对斑马鱼胚胎发育的影响。结果表明,酸性水体及Cu2+单一存在时,酸对斑马鱼胚胎24h半数效应浓度值EC50为pH=3.65,Cu2+(pH=7.8)对斑马鱼胚胎24h-EC50为0.267mg·L-1;当水体酸化及水体中的Cu2+共存时,较低的pH对Cu2+的生物毒性起协同作用,表现为随溶液pH的降低,各浓度Cu2+对斑马鱼胚胎的24h凝结率显著增高(P24h致死率=0.001),而斑马鱼胚胎96h孵化率显著降低(P96h孵化率=0.002),且不同浓度的Cu2+之间的生物毒性效应存在显著性差异(P24h致死率=0.0321;P96h孵化率=0.0028)。这说明酸性水体和Cu2+都显著影响斑马鱼胚胎的发育,且Cu2+在酸性水体中对斑马鱼胚胎的毒性显著增强。因此,在受重金属Cu2+污染的地区,如同时受到酸雨或酸性矿山排水等较低pH值和Cu2+的双重胁迫,较低浓度的Cu2+就能够对水生生物的生殖发育及水生生态系统产生严重的影响和危害。 相似文献
8.
Cod ( Gadus morhua) were exposed to hypercapnia (water Pco 2 = 7.5 mmHg), elevated copper level (0.4 ppm) or a combination of both in order to study extra- and intracellular acid-base
regulation and the influence hereupon of copper. During pure hypercapnia, the extracellular respiratory acidosis was completely
compensated within 12 to 24 h via a chloride-mediated increase in extracellular [HCO 3
−]. Exposure to copper in normocapnic seawater caused a large and progressive increase in plasma [Na +] and [Cl −] and a metabolic acidosis. Exposure to copper in hypercapnic seawater was associated with smaller elevations of plasma [Na +] and [Cl −] than in normocapnic seawater, showing that hypercapnia had a protective effect on the copper-induced osmoregulatory disturbances.
The compensation of the hypercapnic acidosis was, however, slow and incomplete in fish exposed to both copper and hypercapnia.
Extracellular pH remained depressed by 0.3 pH units after 72 h. The data reveal that acid-base regulation was immediately
and persistently inhibited by copper. The limited acid-base regulation during combined copper and hypercapnia exposure was
chloride-mediated as during hypercapnia alone. Intracellular pH recovery was complete and very rapid in ventricular and skeletal
muscle tissues during environmental hypercapnia, whereas acid-base compensation in liver tissue was slower, the kinetics being
similar to that in the extracellular compartment. Intracellular pH compensation was significantly slowed down by copper. Copper
concentration increased drastically in gill tissue already at 3 h, while copper concentrations in liver, muscle and plasma
were significantly elevated only after 48 h, with liver showing the largest elevation.
Received: 15 November 1996 / Accepted: 2 December 1996 相似文献
9.
Powdered maize tassels were studied and found to exhibit metal sorption properties due to the availability of functional groups. The tassels have a high amount of soluble organic substances that can dissolve in aqueous media, contributing to secondary pollution during a water treatment process. A chelating agent was chemically attached on the maize tassels with a view to increase the sorption capacity, minimize leaching, and enhance the tassels’ stability. Thermogravimetric analysis confirmed that modification improved their thermal stability to withstand temperatures above 600°C as well as reduced the “secondary pollution”. The modified sorbent was employed for the sorption of lead, copper, and cadmium ions in both the model solutions and the real samples. The contact time and pH were optimized after which Langmuir and Freundlich isotherms were applied to the data. The sorption capacities for Cu 2+, Cd 2+, and Pb 2+ improved from 3.4, 0.8, and 1.7?g?kg ?1, respectively, to 6.3, 2.6, and 2.6?g?kg ?1 in the same order. The sorbent was shown to remove up to 95% of the metals in less than 10 min. This study has a potential application for the remediation of polluted waters. 相似文献
10.
Studies on the suitability of various chemically prepared activated carbons (CPACs) like straw carbon (SC), sawdust carbon (SDC), dates nut carbon (DNC) and commercial activated carbon (CAC) for the removal of copper(II) ions by adsorption from simulated wastewater have been carried out under batch mode at 30?±?1°C and the results are compared. The percentage removal of Cu(II) ions increased with a decrease in initial concentration, particle size and added electrolytes (ionic strength) and increased with an increase in contact time, dose of adsorbent and initial pH of the solution. The adsorption data were fitted with the Langmuir isotherm. The applicability of the first order kinetic equation viz. Lagergren equation was tested by correlation analysis. The adsorption process is concluded to be a spontaneous, first order reaction, occurring with increased randomness at the solid–liquid interface. Studies on the desorption of Cu 2+-loaded activated carbons (ACs) were carried out with nitric acid (0.2–1?N). The possibility of reuse of the regenerated ACs in cycle (in cue-one after another) was tested. SC was found to be a suitable adsorbent alternative to CAC among CPACs for the removal of metal ions, in general, and Cu 2+ ions, in particular. 相似文献
11.
We studied the removal mechanism and affecting factors of Fe 2+-based replacement–precipitation process for treating CuEDTA-containing wastewaters. Since Fe 2+ was easily oxidized to Fe 3+ in the presence of oxygen, the chelated copper was removed by the synergetic effect of Fe 3+ replacement and NaOH precipitation. Our experiments showed that the copper removal efficiency was considerably dependant
on pH conditions of the solution and molar ratio of Fe 2+/Cu 2+. 相似文献
12.
The adsorptive characteristics of biochar produced from garden green waste (S-char) and a mixture of food waste and garden green waste (FS-char) were investigated. Adsorption of Cu 2+, Zn 2+, and Mn 2+ onto the two biochars reached equilibrium within 48 hours. The metal adsorption was effectively described by the pseudo-second-order kinetic and Freundlich isotherm models which suggest heterogeneous chemisorption. The initial solution pH influenced adsorption of Zn 2+ and Mn 2+ but not of Cu 2+. Simulation via a surface complexation model showed that the fraction of XOCu + adsorbed onto biochar was increased with increasing pH until it reached the adsorption maximum at pH 8.5, while the endpoint for the maximum of XOMn + was higher than pH 12. 相似文献
13.
The bioavailability and toxicity of zinc to aquatic life depend on dissolved organic matter (DOM), such as Suwannee River Fulvic Acid (SRFA), which plays an important role in the speciation of zinc. This study examined reactions of SRFA with zinc at different concentrations from pH 3.0 to 9.0, and competitive binding of calcium/magnesium and zinc to SRFA at pH 6.0, using in situ absorbance. Interactions of Zn2+ with SRFA chromophores were evidenced by the emergence of features in Zn-differential spectra. Among all Zn2+–SRFA systems, dominant peaks, located at 235, 275 and 385 nm, and the highest intensity at 235 nm indicated the replacement of protons by the bound Zn2+. The Zn2+ binding with SRFA could be quantified by calculating the changes of the slopes of Zn-differential log-transformed absorbance in the wavelength range of 350–400 nm (denoted as DS350–400) and by comparing the experimental data with predictions using the Non-Ideal Competitive Adsorption (NICA–Donnan) model. DS350–400 was correlated well with the bound Zn2+ concentrations predicted by NICA–Donnan model with or without Ca2+ or Mg2+. Ca2+ and Mg2+ only affect intensity of the Zn-differential and Zn-differential log-transformed absorbance, not shape. In situ absorbance can be used to gain further information about Men+–DOM interactions in the presence of various metals. 相似文献
14.
The biosorption of Cd 2+ and Cu 2+ onto the immobilized Saccharomyces cerevisiae ( S. cerevisiae) was investigated in this study. Adsorption kinetics, isotherms and the effect of pH were studied. The results indicated that the biosorption of Cd 2+ and Cu 2+ on the immobilized S. cerevisiae was fast at initial stage and then became slow. The maximum biosorption of heavy metal ions on immobilized S. cerevisiae were observed at pH 4 for Cd 2+ and Cu 2+. by the pseudo-second-order model described the sorption kinetic data well according to the high correlation coefficient ( R 2) obtained. The biosorption isotherm was fitted well by the Langmuir model, indicating possible mono-layer biosorption of Cd 2+ and Cu 2+ on the immobilized S. cerevisiae. Moreover, the immobilized S. cerevisiae after the sorption of Cd 2+ and Cu 2+ could be regenerated and reused. 相似文献
15.
The analysis of genotypic shifts in field-exposed populations has been proposed as a tool for monitoring the environmental
impacts of contaminants. Previous laboratory experiments showed the occurrence of genotypic shifts induced by copper exposure
in samples of Hediste diversicolor from the Pialassa estuary (North Adriatic Sea, Italy). In order to test if genotype-tolerance responses observed were consistent
at larger spatial scales, populations of H. diversicolor were sampled in three haphazardly chosen estuaries along the Italian coast (Comacchio, Pialassa, Serchio) and exposed to
0.48 mg l −1 Cu 2+ under laboratory conditions. Survival analysis procedures were used to test for possible relationships between time-to-death
and genotypes at three allozyme loci ( ALD, FH, PGI). Genotype-tolerance responses observed at locus ALD were consistent among populations up to 2500 km distant, with genotype ALD
102/102 associated with the shortest survival times. Comparisons with previous laboratory experiments showed that responses to copper
stress at locus ALD were also consistent in time, with genotypes ALD
102/102 and ALD
100/102 associated with higher 96 h mortality ratios. Results suggested the occurrence of stable relationships between genotypes
at locus ALD and tolerance responses of H. diversicolor to copper stress. Conversely, genotype-tolerance responses at loci PGI and FH were not consistent either in space (among populations from the three estuaries) or in time (between laboratory experiments),
being possibly affected by site-specific features of populations or stochastic factors. Results show that genotype-tolerance
responses should be carefully verified at different spatial and temporal scales, before considering genotypic shifts among
the possible tools for monitoring the effects of environmental stressors. 相似文献
16.
We tested the hypothesis that ultraviolet-absorbing compounds known as mycosporine-like amino acids (MAAs) are not only synthesized but also excreted by marine phytoplankton. An experiment was performed with cultures of the marine dinoflagellate Lingulodinium polyedra (previously known as Gonyaulax polyedra) exposed to visible (photosynthetically available, PAR, 400 to 700 nm) and ultraviolet (UV, 290 to 400 nm) radiation. Absorption properties of both particulate and dissolved organic matter pools (POM and DOM, respectively) showed maxima in ultraviolet absorption at 360 nm. Chromatographic analysis confirmed the presence of MAAs in both pools. Release of organic matter by L. polyedra, as measured spectrophotometrically by changes in UV absorption in the surrounding medium, showed a differential increase at 360 nm in cultures exposed to UV-B + PAR radiation. The changes in absorption in the DOM fraction were inversely proportional to intracellular UV absorption. Photodegradation experiments in which the DOM fraction was exposed to visible and UV-B radiation showed a decrease in absorption with dose. First-order photooxidation decay rates varied between – 0.005 and – 0.26 m 2 (mol quanta) –1 and were also a function of the initial optical density (OD). These results indicate that UV-absorbing compounds synthesized by phytoplankton, such as certain dinoflagellates, may be a component of the DOM pool in surface waters of the ocean and contribute to the attenuation of UV radiation in the water column. Photooxidation consumes only 3 to 10% of the daily production of the DOM absorbing between 280 and 390 nm (including MAAs). This suggests that MAAs dissolved in seawater may contribute to the decrease of UV transmission through the water column on a time scale representative of phytoplankton growth (days) and bloom development (weeks). 相似文献
17.
Biochar, is a low-cost material that can be used as an alternative adsorbent for the removal of heavy metals. In this study, a low-cost and efficient adsorbent synthesised from Jatropha curcas seeds was used for the uptake of Cu 2+ from aqueous solutions. The as-prepared adsorbent was characterised by scanning electron microscopy and Brunauer–Emmett–Teller analysis post calcination at 500 °C, its BET surface area and total pore volume were 39.62?m 2?g ?1 and 0.049?m 3?g ?1, respectively. Subsequently, the effects of initial pH of the solution, contact time, and adsorbent material dosage on the adsorption of Cu 2+ by the prepared adsorbent were investigated. The as-prepared adsorbent exhibited a high performance, with a maximum adsorption amount of 32.895?mg?g ?1 for Cu 2+ at pH 5.0 and 25 °C, owing to the presence of ?OH, C=O, C–O, Si-O-Si, and O-Si-O on its surface. The predominant Cu 2+ adsorption mechanism was assumed to be ion exchange. Notably, the Cu 2+ adsorption could attain equilibrium within 90?min. In addition, the fact that the Langmuir model was a better fit than the Freundlich model for the isotherm data of Cu 2+ adsorption by the as-prepared adsorbent suggested that the adsorption of Cu 2+ was a monolayer adsorption process. 相似文献
18.
Concentrations of Fe, Mn, Cu, dissolved organic matter (DOM), and pH were synthesized from 30 publications to determine the
factors regulating concentrations and behavior of metals in freshwater systems. Results from the review suggest that contrasting
watershed land use can directly (erosion and runoff) and indirectly (in-lake processes including metal–DOM–pH interactions)
affect the metal concentrations in freshwater systems. Among the watershed land uses considered here, concentrations of Fe,
Mn, and Cu were observed in the following order: arctic lakes < forested < agricultural < urbanized < mined. A drastic difference
in mean metal concentrations has been observed when undisturbed or low impact watersheds (arctic and forested) were changed
by agricultural, urban, and mining developments. Relationships between metal concentrations and pH revealed that metals precipitate
at high pH (pH > 5). Additionally, at pH < 5, metal concentrations were significantly correlated with DOM due to metal–DOM
complexation. High ratios of metal: DOM occur only at low DOM concentrations. Collectively, two general conclusions can be
drawn from this review. First, lakes, rivers, and streams with urbanized watersheds are the most susceptible to increased
concentrations of metals. Secondly, these results also suggest that regardless of high or low DOM in the water column, pH
would affect metal concentrations in freshwater systems. Nonetheless, free metal ions would be higher in freshwater systems
with acidic water and low DOM. 相似文献
19.
The comparative kinetics of the accumulation of the trace metals copper, zinc and cadmium have been measured in the estuarine
burrowing polychaete worm Nereis (Hediste) diversicolor from two sites: (a) a metal-rich site, Restronguet Creek, Cornwall, UK, which hosts a copper- and zinc-tolerant population
of worms, and (b) the Blackwater estuary, Essex, UK as a control site. A sediment transfer experiment showed that the Blackwater
worms responded to the increased copper bioavailability in Restronguet Creek sediment by accumulating significantly increasing
copper concentrations over 50 days. The Restronguet Creek worms showed no significant change in copper concentration over
50 days in sediment from either site or in sand. Nevertheless, electron microscopy showed that some Restronguet Creek worms
do appear to excrete accumulated copper, probably in association with renewal of the cuticle over a long time scale. The Blackwater
worms did not accumulate extra zinc from the zinc-rich Restronguet Creek sediment, in probable reflection of the regulation
of body zinc concentration by N. diversicolor. Radiolabelled zinc and cadmium were accumulated from labelled sediment and labelled solution by worms from both sites. The
rate of uptake of labelled zinc from sediment was significantly greater in the Restronguet Creek worms, as was the rate of
uptake of labelled cadmium from 10 μg l −1 dissolved exposure; other rates of uptake did not differ between populations. Mucus, which is secreted by Restronguet Creek
worms in response to enhanced copper exposure, adsorbed very small proportions of zinc and cadmium present in solution, indicating
that the mucus does not act as an adsorption barrier against excessive metal uptake by these worms. 相似文献
20.
An major research area in environmental chemistry is the development of methods for the analysis of biomarkers. Metallothioneins
are used as biomarkers in studies of heavy metals exposure in water, because metallothioneins are synthesized and accumulated
when organisms are exposed to toxic concentrations of pollutants. In this work, simple and sensitive voltammetric methods
were developed for metallothionein and copper (II) determinations in fish liver Lepomis gibbosus. Both analytical methodologies were optimized and applied to samples extracted from individuals previously submitted to sub-lethal
toxicological trials with copper sulphate (CuSO 4) and cadmium chloride (CdCl 2). The obtained results showed that both methods are very precise, sensitive, and involve simple sample preparation processes.
Moreover, metallothioneins showed better correlation with the toxic exposure than Cu 2+. To the best of our knowledge, this is the first time that hepatic metallothioneins and Cu 2+ contents are voltammetrically determined in order to be compared in their function as heavy metal biological indicators. 相似文献
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