离子交换纤维对金属氰络合物吸附性能的研究

采用强碱性离子交换纤维对含氰废水中主要离子铜氰络合物、锌氰络合物的吸附性能进行了研究。实验结果表明：含氰废水的pH在8—11范围内，纤维材料对金属氰络合物具有良好的吸附性能；纤维对铜氰络合物、锌氰络合物的吸附速率很快，4min左右就可达吸附平衡；温度对铜氰络合物、锌氰络合物吸附影响不大，纤维的这些吸附特点对工业应用非常有利。     

离子交换纤维对金属氰络合物吸附性能的研究

采用强碱性离子交换纤维对含氰废水中主要离子铜氰络合物、锌氰络合物的吸附性能进行了研究.实验结果表明:含氰废水的pH在8～11范围内,纤维材料对金属氰络合物具有良好的吸附性能;纤维对铜氰络合物、锌氰络合物的吸附速率很快,4 min左右就可达吸附平衡;温度对铜氰络合物、锌氰络合物吸附影响不大,纤维的这些吸附特点对工业应用非常有利.     

Calcium carbonate phosphate binding ion exchange filtration and accelerated denitrification improve public health standards and combat eutrophication in aquatic ecosystems.

Cultural eutrophication, the process by which a lake becomes rich in dissolved nutrients as a result of point and nonpoint pollutant sources, is a major cause of the loss of natural lake ecosystems throughout the world. The process occurs naturally in all lakes, but phosphate-rich nutrient runoff from sources such as storm drains and agricultural runoff is a major cause of excess phosphate-induced eutrophication. Especially in Madrona Marsh, one of the last remaining vernal marshes in the greater Los Angeles area, California, cultural eutrophication has become a major problem. In this study, calcium carbonate was found to be an excellent phosphate binder, reducing up to 70% of the phosphates in a given sample of water, and it posed relatively negligent ecological repercussions. This study involved the testing of this principle in both the laboratory and the real ecosystem. A calcium carbonate lacing procedure was first carried out to determine its efficacy in Madrona Marsh. Through this, ammonia was found to interfere with the solubility of calcium carbonate and therefore to be a hindrance to the reduction of phosphate. Therefore, various approaches for reduction of ammonia were tested, including aeration, use of fiber growth media, and plants, mainly Caulerpa verticellata, chosen for it hardiness, primarily in an attempt to increase population of Nitrobacter and Nitrosomonas. All were successful in moderately reducing ammonia levels. In addition, soil sampling, sediment analysis, microscopic plant analysis, microorganism and macroinvertebrate identification, and rate law formulations were conducted. The effect of phosphate and ammonia reduction on the populations of enterobacteria was also an important focus of this experiment. Varying concentrations of phosphate, ammonia, and calcium carbonate in conjunction with phosphate were tested in Madrona Marsh to determine their effects on the populations of enteropathogens on nonspecific blood agar, MacConkey agar, and Hektoen agar. Initial analyses suggest a strong correlation between phosphate concentrations and bacterial populations; a 66% decrease in phosphate resulted in a 35% reduction in bacterial populations and a 45% reduction in enteropathogenic populations. Likewise, a strong correlation was shown between calcium carbonate concentrations and bacterial reduction greater than that which can be attributed to the phosphate reduction alone. This was followed by the construction of various phosphate binding calcium carbonate filters, which used the ion exchange principle, including a spring loading filter, PVC pipe filter, and a galvanized filter. All were tested with the aid of Stoke's law formulation. The experiment was extremely successful in designing a working phosphate-binding and ammonia-reducing filter, and a large-scale agitator-clarifier filter system is currently being planned for construction in Madrona Marsh; this filter will reduce phosphate and ammonia levels substantially in the following years, bringing ecological, economical, and health-related improvements to the overall ecosystem and habitat.     

Heavy metal accumulation in Halimione portulacoides: intra- and extra-cellular metal binding sites

Salt marsh plants can sequestrate and inherently tolerate high metal concentrations found in salt marsh sediments. This work intended to understand the Halimione portulacoides (L.) Aellen strategies to prevent metal toxicity, by investigating the metal location in different plant organs and in the cell. A sequential extraction was performed on leaves, stems and roots of H. portulacoides in order to determine and compare the metal (Zn, Pb, Co, Cd, Ni and Cu) concentration in several fractions of the plant material (ethanolic, aqueous, proteic, pectic, polissacaridic, lenhinic and cellulosic). This study shows that all plant organs of H. portulacoides mostly retain metals in the cell wall (65% is the average for all studied metals stored in the root cell wall, 55% in the stems and 53% in the leaves), and the metal content in the intracellular compartment is much lower (21% in roots, 25% in stems and 32% in leaves). High levels of heavy metal in the sedimentary environment do not cause toxicity to H. portulacoides, because H. portulacoides immobilizes them in different cell compartments (cell wall+proteic fraction+intracellular) outside key metabolic sites.     

水环境中腐殖酸与镉离子结合作用的影响因素

通过测定不同化学条件下腐殖酸与镉离子作用后的游离态镉离子浓度及其结合率,研究各因素对腐殖酸与镉离子作用的影响。研究结果表明,pH值、离子强度、投加镉离子总浓度、腐殖酸浓度和反应温度均影响腐殖酸与镉离子的结合。pH值在4.5~6.5范围内,随pH值升高,腐殖酸与Cd²⁺的结合率增大,游离态Cd²⁺浓度减少。溶液的离子强度增大对结合反应有抑制作用。投加Cd²⁺总浓度的增大会导致结合态Cd²⁺浓度和游离态Cd²⁺浓度逐渐增加,而其结合率逐渐减小。腐殖酸浓度逐渐增大,使Cd²⁺和腐殖酸的结合率逐渐增大。在20℃~50℃范围内时,随反应温度升高,游离态Cd²⁺浓度逐渐减小,其结合率逐渐增加。     

典型离子交换水处理技术在低浓度氨氮回收中的应用分析

离子交换技术具有交换容量高、能耗低、可再生效率高、操作过程简单、环境友好,并且能同时实现水质净化和资源原位回收等优势,在水处理领域应用十分广泛。在文献及工程调研的基础上,综述了3种典型离子交换剂：沸石、粉末树脂、磁性离子交换树脂的技术原理及其在污水处理中的应用现状;分析了三者在低浓度氨氮回收过程中存在的问题,并提出了相应的研究策略;评价了3种离子交换剂在工程化应用中的经济性,主要介绍了成熟的磁性离子交换树脂工艺;通过分析可知,将离子交换技术从污水治理领域应用到污水中低浓度氨氮原位富集回收领域,对污水全面资源化利用具有重要意义。     

Removal of metal ions from the complexed solutions in fixed bed using a strong-acid ion exchange resin

Fixed bed removal of equimolar metal ions (Co²⁺, Ni²⁺, Mn²⁺, Sr²⁺) from aqueous solutions using a strong-acid resin was examined. The solution contained a water-soluble complexing agent including ethylenediaminetetraacetic acid, nitrilotriacetic acid, and citric acid. Experiments were performed under different solution pH and molar concentration ratios of complexing agent to the total metals. It was shown from batch studies that the equilibrium exchange of metals and the resin mainly depended on solution pH, and partly on the type of complexing agent used. A mass transfer model was proposed to describe the breakthrough curves of the resin bed, which contained two parameters (τ and k) estimated from the observed breakthrough data. The calculated breakthrough curves agreed well with the measured ones (standard deviation <6%). In fixed bed tests at low pH (=2), the type of complexing agent had little effect on the breakthrough data. For a given complexing agent, the metal with a larger overall formation constant (K_f) showed a smaller exchange capacity. For a given metal ion, the complexing agent with a larger K_f also revealed a smaller exchange capacity.     

Estimates of average major ion concentrations in bulk precipitation at two high-altitude sites near the continental divide in southwestern colorado

The composition of bulk precipitation from two high-altitude sites, established in 1971 near the Continental Divide in southwestern Colorado, has been monitored by season during the past decade. Calcium ions are the predominant cationic species; sulfate is the major anionic consitituent. Bulk precipitation major ion concentrations exhibit log-normal distributions. Representative mean and standard deviation values for the major inorganic ionic species present in bulk precipitation have been calculated for three years of consecutive seasons. Standard deviations for all species, except nitrate, are similar. For two years of data grouped into quarters, deviations from mean values fall well within the plus or minus two standard deviation limit. There does not seem to be a systematic deviation from the mean concentration values, with respect to either ionic component or season.     

Studies of metal-binding sites in natural organic matter and their role in the generation of disinfection by-products using lanthanide ion probes

In this study, the complexation of Tb3+ with natural organic matter (NOM) was studied by the method of time-resolved fluorescence spectroscopy. In the presence of NOM, the excitation of Tb3+ was observed in a wide range of wavelengths, for which virtually no excitation of free Tb3+ took place. The pseudo-quantum yield spectra (excitation intensity normalized by corresponding light absorbance values) had a maximum at 282 nm. This indicated that the excitation of NOM-bound Tb3+ proceeds through energy transfer from aromatic groups in NOM. The concentration of the metal-binding sites (C(L)) was determined by titration with Tb3+ and was found to range from 0.21% to 0.83% of total moles of organic carbon. The actual number of the carbon atoms that comprise these functionalities was hypothesized to be at least seven times higher. The C(L) values were well correlated with the reactivity of NOM with chlorine quantified by total organic halogen formation potential and with the contribution of polyhydroxyaromatic moieties determined by pyrolysis-GC/MS method. The correlation of C(L) with the contributions of aromatic and carboxylic moieties in NOM determined by 13C NMR was poor. Based on the data, it was concluded that the metal binding functionalities in NOM are closely associated with halogen attack sites.     

Dry deposition of particles and canopy exchange: Comparison of wet,bulk and throughfall deposition at five forest sites in Italy

The contribution of dry deposition to the total atmospheric input of acidifying compounds and base cations is of overwhelming importance. Throughfall measurements provide an estimate of the total deposition to forest soils, including dry deposition, but some uncertainties, related to the canopy interaction processes, affect this approach. We compared the concentrations and the fluxes of the main ions determined in wet-only, bulk and throughfall samples collected at five forest sites in Italy. The contribution of coarse particles deposited onto the bulk samplers was of prime importance for base cations, representing on average from 16% to 46% of the bulk deposition. The extent of this dry deposition depended on some geographical features of the sites, such as the distance from the sea and the annual rainfall. The possibility of applying specific bulk/wet ratios to estimate the wet deposition proved to be limited by the temporal variability of these ratios, which must be considered together with the spatial variability. A direct comparison of the dry contribution deriving from the bulk–wet and the throughfall–wet demonstrated that an extensive natural surface (forest canopy) performs better than a small synthetic surface (funnel of the bulk sampler) in collecting dry deposition of SO₄²⁻, NO₃⁻ and Na⁺. The canopy exchange model was applied to both bulk and wet data to estimate the contribution of dry deposition to the total input of base cations, and the uncertainty associated to the model discussed. The exclusive use of bulk data led to a considerable underestimation of base cation dry deposition, which varies among the study sites.     

Selective adsorption of Pb (II) over the zinc-based MOFs in aqueous solution-kinetics,isotherms, and the ion exchange mechanism

Environmental Science and Pollution Research - Two series of metal–organic frameworks (MOFs) with similar formula units but different central metal ions (M) or organic linkers (L), M-BDC...     

铬离子对SBR工艺活性污泥毒性作用研究

针对重金属铬离子对SBR工艺系统中活性污泥的毒性作用,通过检测不同初始污泥容积指数(SVI)下SBR工艺活性污泥在不同铬负荷下的COD值、挥发性污泥浓度以及受铬离子影响的污泥容积指数(SVI),研究重金属铬离子对活性污泥的毒性作用以及对SBR工艺系统处理污水的影响。研究表明,重金属铬离子会导致SBR工艺系统出水COD升高;将铬离子对活性污泥的毒性作用按照挥发性污泥(MLVSS)铬负荷可划分为耐受范围、非耐受范围、细胞失活范围以及细胞分解范围。耐受范围铬负荷低于约30 mg Cr3+/gMLVSS,此范围内铬离子对于活性污泥的毒性作用不大,不致于导致系统出水水质变差;非耐受范围铬负荷在约30~65 mg Cr3+/g MLVSS,在铬离子作用下系统出水COD值明显高于对照系统;细胞失活范围铬负荷在约70~100 mg Cr3+/gMLVSS范围内,SVI大幅下降,微生物部份死亡和失活,出水COD尽管有一些下降,但与进水COD相比差不了多少;细胞分解范围铬负荷在约100 mg Cr3+/gMLVSS以上,微生物大量死亡,部分死亡细胞分解,系统出水COD值因微生物的死亡分解而超出进水COD值,受铬离子影响的系统SVI值大幅度降低。     

Nutrient leaching from conifer needles in relation to foliar apoplast cation exchange capacity

Limited evidence to date suggests that acidic precipitation promotes leaching of nutrient cations from conifer foliage. In order to evaluate the relative contribution of the apoplast cation exchange complex and symplast nutrient pools to the leached ions, the magnitude of foliar leaching in response to acidic solutions was compared to foliar apoplast cation exchange capacity (CEC) for two conifer tree species (Pseudotsuga menziesii and Picea engelmanii). Leaching potential was determined by immersing detached needles in acidic solutions (pH5.6, 3.1, 2.1) over a range of time intervals (1, 4, 8, 24 h) and foliar apoplast cation exchange capacity was determined by potentiometric titration. Leaching increased with decreasing pH and increasing time of immersion. At pH values 2.1 and 3.1, equivalents of H+ depleted from the acidic solutions approximated equivalents of base cations gained by the solutions. Maximum amounts leached were less than 40 microeq g(-1) dry weight of needles for the combination of calcium, magnesium and potassium. Measured foliar apoplast CEC for these species was approximately 120 microeq g(-1) dry weight of needles. These relative magnitudes indicate that the apoplast rather than the symplast provided the leached ions. Because the apoplast foliar cation exchange capacity appears to be large relative to the rates of H+ diffusion across the cuticle, it may help to insulate the symplast nutrient reservoir from exposure to the H+ of acidic solutions bathing the foliage.     

Investigation of structural requirements for inhibitory activity at the rat and housefly picrotoxinin binding sites in ionotropic GABA receptors using DISCOtech and CoMFA

A number of widely diverse compounds that show inhibitory activities at the picrotoxinin binding sites in housefly and rat GABA receptors were investigated by using the distance comparison technique (DISCOtech) and comparative molecular field analysis (CoMFA) methods to explore the pharmacophore models and the three-dimensional quantitative structure-activity relationships (3D-QSAR) of the compounds. These compounds consist of three diverse types of noncompetitive GABA receptor antagonists, i.e., trioxabicyclooctanes and their derivatives, picrodendrins and related terpenoids, and fipronil and its analogs. For investigation of the structural requirements for inhibitory activity at the picrotoxinin binding site of GABA receptor, DISCOtech pharmacophore models containing one center of hydrophobic ring and two hydrogen bond acceptor atoms for both housefly-head and rat-brain GABA receptors were constructed, respectively. In particular, the interacting areas in housefly receptors appear to be wider than that in rat receptors, the differences between rat and housefly receptor models implicate the selectivity of noncompetitive GABA receptor antagonists. In addition, corresponding CoMFA models with good statistical indices (r(2)>0.9 and q(2)>0.5) were also obtained. These models can be used as guidance for the development of new compounds with high activities and selectivities.     

Chronic exposure to environmental stressors induces fluctuating asymmetry in shrews inhabiting protected Mediterranean sites

Many ecotoxicological studies have addressed the effects of contaminant exposure at various levels of biological organization. However, little information exists on the effects of toxicants on wildlife populations. Here we examined exposure of populations of the greater white-toothed shrew Crocidura russula (Soricomorpha, Soricidae) occupying two protected Mediterranean sites (a polluted area, the Ebro Delta, and a control site, Garraf Massif). Bioaccumulation of selected elements (Pb, Hg, Cd, Zn, Cu, Fe, Mn, Cr, Mo, Sr, Ba, and B), a body condition index (BCI) and fluctuating asymmetry (FA) were used to assess the chronic exposure to environmental pollution. BCI was correlated neither to metal concentrations nor to FA, suggesting that this fitness measure only reflects environmental disturbances at a local level. However, shrews from the polluted area showed higher concentrations of metals and metalloids (Pb, Hg, B, and Sr) and greater shape FA than specimens from the reference area. A correlation between FA was found for both first and second principal component vectors suggesting that developmental instability increases as a result of exposure to multiple pollutants. Our results corroborate the suitability of C. russula as a bioindicator of environmental quality and show that FA is an appropriate index to examine impact of developmental stressors in populations inhabiting disturbed areas.     

The binding of three PCB congeners to dissolved organic carbon in freshwaters

The binding of three polychlorinated biphenyl (PCB) congeners to natural levels of dissolved organic carbon (DOC) was measured in 12 lakes and streams using Sep-Pak C₁₈ columns. The association coefficients calculated on the basis of DOC (i.e. K_DOC mL/g C), varied by over an order of magnitude among the different freshwaters and ranged between 2.05 × 10² and 8.86 × 10³ mL/g C for PCB 52 and 1.03 × 10⁴ and 1.70 × 10⁵ mL/g C for PCB 153. In general, there were no significant correlations (p > 0.05) between the K_DOC values and various chemical parameters in the study lakes and streams.

A relationship was derived between the fraction of bound PCB and the octanol-water partition coefficient. While this relationship explained almost 50% of the variation in the observed data, it is apparent that other factors influence K_DOC values and that in natural freshwaters, only a small fraction of the DOC is involved in the binding of PCBs and other hydrophobic pollutants.     

Air and soil dioxin levels at three sites in Italy in proximity to MSW incineration plants

Levels of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) in both air and soil samples were measured at three different sites in Italy, in proximity to three municipal solid waste incinerators (MSWIs) to determine baseline contamination and the contributory role of incinerator emissions. At the first site, located in an agricultural, cattle-breeding, typically flattish area of the Po Valley, the dioxin concentrations had already been measured before the start-up of the new MSWI. These dioxin concentrations were then again measured after two years of continual operation of the incinerator. Despite the presence of the plant, the PCDD/Fs concentrations appear not to have been affected and were found to be in a range of 22-125 fg I-TEQ m(-3) in the air samples and 0.7-1.5 pg I-TEQ g(-1) in the soil samples. The second site is located in an industrial district of the Veneto Region, in the surroundings of an old MSWI that is not equipped with Best Available Technology (BAT) dioxin removal system. The PCDD/Fs concentrations in the air samples were between 144 and 337 fg I-TEQ m(-3). This is a typical range of values for industrial areas, while the soil samples showed contamination levels between 1.1 and 1.4 pg I-TEQ g(-1). The third site lies in the Adige Valley, near a MSWI that has been equipped with BAT for flue gas cleaning. The observed values ranged from 10 to 67 fg I-TEQ m(-3) for the air samples and 0.08-1.2 pg I-TEQ g(-1) for the soil samples. The contributory factors of the varying characteristics of the different areas together with the types of technology adopted at each MSWI plant are discussed. The PCDD/Fs levels are subsequently compared with established values from previous studies.     

Contribution of the diffusive exchange method to the characterization of pore-water in consolidated argillaceous rocks

Consolidated argillaceous rocks, potential host rocks for nuclear waste disposal, display particular properties (low water content, very small pore size) that require specific methods, especially for the characterization of their pore-water. The diffusive exchange method was applied to the claystone of Tournemire by taking into account the effect of swelling or micro-cracks induced by drilling. The good agreement of diffusion parameters with those obtained from the through-diffusion method showed that the extent of this disturbance was low. This method led to stable isotope content values in pore-water in good agreement with those measured in the fracture fluids located in the vicinity, validating the method. On the contrary, the vacuum distillation technique gave a systematic depletion in heavy isotopes of water, probably induced by an incomplete extraction of pore-water. For the chloride tracer, the determination of the accessible porosity on each sample allowed the estimate of chloride concentration of pore-water to be improved, by taking into account all the petrophysical heterogeneities.