Heavy metals regulate physiological and behavioral events by modulating ion channels in neuronal membranes of molluscs

The interaction of heavy metals (HgCl₂, CdCl₂, CuCl₂, PbCl₂ and ZnCl₂) and neurotransmitters (ACh, 5HT and DA) was studied on the excitable membrane of identified neurons of Lymnaea stagnalis and Helix pomatia. It was shown that,

1. The excitability and chemosensitivity of molluscan neurons were modified under the influence of the heavy metals Hg²⁺, Cd²⁺, Cu²⁺, Pb²⁺ and Zn²⁺.
2. Change in excitability to transmitters occurred as a potentiation or depression of the evoked response both in duration of membrane polarization and in frequency of spike activity.
3. The chemosensitivity changes in various ways, namely:
4. excitatory effect was totally eliminated;
5. one component of the effect was depressed.
Different neurons may show different reactions to the same heavy metal.
6. There were differences in the effects of various heavy metals. Hg²⁺ has a more generalized effect than Cd²⁺; Cu²⁺, Pb²⁺ and Zn²⁺ were less effective in a number of neurons. The heavy metal effect was dose dependent, too.
7. Both inward and outward currents, which were evoked by neurotransmitters or voltage induced, were modified in most of the tested neurons. Both an increase and decrease of the membrane permeability occurred in different neurons in response to the same or different heavy metals.
8. The changes can be interpreted as a result of
9. direct effect on specific ionic channels;
10. modification of receptors binding ACh, 5HT, or DA;
11. modification of intracellular processes responsible for the regulation of membrane permeability.

     

Vehicular stress a cause for heavy metal accumulation and change in physico-chemical characteristics of road side soils in Pahalgam

In an effort to determine vehicular impact on soil quality, soil samples were collected from three different zones (Pahalgam, Batakote, and Chandanwari) in Pahalgam forest ecosystem. Results showed that a significant decrease in moisture content, organic carbon, available nitrogen, and potassium was observed in nearby road side soils. However, pH was observed to be on neutral side and available phosphorus recorded high concentration. The concentration of heavy metals Pb²⁺, Cu²⁺, Zn²⁺, Ni²⁺, and Cd²⁺ estimated was also significantly high. Furthermore, concentration of Pb²⁺ at high vehicular load subzones was observed to be highest (1.168 mg/Kg) followed by Zn²⁺ (0.896 mg/Kg), Ni²⁺ (0.649 mg/Kg), Cu²⁺ (0.415 mg/Kg), and Cd²⁺ (0.079 mg/Kg). An inter-zone analysis revealed that the concentration of the heavy metals (Pb²⁺?>?Ni²⁺?>?Cd²⁺) was observed to follow the trend, Z-I?>?Z-II?>?Z-III. Variation along the temporal gradient and the impact on soil qualities were notably higher in summer. Vehicular pollution to a great extent impacts physico-chemical characteristics and more interestingly adds substantial concentration of heavy metals in soils.     

A new <Emphasis Type="Italic">P. putida</Emphasis> instrumental toxicity bioassay

Here, we present a new toxicity bioassay (CO₂-TOX), able to detect toxic or inhibitory compounds in water samples, based on the quantification of Pseudomonas putida KT2440 CO₂ production. The metabolically produced CO₂ was measured continuously and directly in the liquid assay media, with a potentiometric gas electrode. The optimization studies were performed using as a model toxicant 3,5-DCP (3,5-dichlorophenol); later, heavy metals (Pb²⁺, Cu²⁺, or Zn²⁺) and a metalloid (As⁵⁺) were assayed. The response to toxics was evident after 15 min of incubation and at relatively low concentrations (e.g., 1.1 mg/L of 3,5-DCP), showing that the CO₂-TOX bioassay is fast and sensitive. The EC₅₀ values obtained were 4.93, 0.12, 6.05, 32.17, and 37.81 mg/L for 3,5-DCP, Cu²⁺, Zn²⁺, As⁵⁺, and Pb²⁺, respectively, at neutral pH. Additionally, the effect of the pH of the sample and the use of lyophilized bacteria were also analyzed showing that the bioassay can be implemented in different conditions. Moreover, highly turbid samples and samples with very low oxygen levels were measured successfully with the new instrumental bioassay described here. Finally, simulated samples containing 3,5-DCP or a heavy metal mixture were tested using the proposed bioassay and a standard ISO bioassay, showing that our test is more sensible to the phenol but less sensible to the metal mixtures. Therefore, we propose CO₂-TOX as a rapid, sensitive, low-cost, and robust instrumental bioassay that could perform as an industrial wastewater-process monitor among other applications.     

On-site solid-phase extraction and application to in situ preconcentration of heavy metals in surface water

An on-site solid-phase extraction, consisting of the sorption, the separation and the elution function units, was designed for in situ preconcentration of heavy metals ions. The D401 resin powder was employed as sorbent to capture Pb²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Co²⁺, and Ni²⁺, and then they desorbed with 2 mol/L nitric acid as eluent. Under the optimized conditions, these heavy metals ions in West Lake, Taihu Lake, and Yangtze River of China were captured and then determined by ICP-OES with the recovery of 92.5% to 111.5%. The on-site solid-phase extraction achieved a quick preconcentration of heavy metals to avoid the transport and storage of a large volume water sample. It is suitable for in situ monitoring of water quality in mountains, tablelands or other remote areas.     

Adsorption studies and the removal of dissolved metals using pyrolusite as adsorbent

The adsorption of metals from aqueous solutions of Pb²⁺, Zn²⁺ and Mg²⁺ on naturally occurring pyrolusite have been studied. The chemical stability of the pyrolusite has been determined in NaOH, H₂SO₄, HNO₃, HCl, NaCl and NK₄Cl solutions of various concentrations. Adsorption of the metal ions followed the order Pb²⁺>Zn²⁺>Cd²⁺.The maximum adsorption of Pb²⁺ (100%) occurred at pH 7. the relation between the amount of Pb²⁺ adsorbed per unit weight of pyrolusite and the concentration of Pb²⁺ at equilibrium follows the Freundlich adsorption isotherm.The efficiency of pyrolusite has been demonstrated by removing lead from synthetic waste water. 100% and 96% removal of lead have been achieved from synthetic waste water containing 5 mg l^–1 and 120 mg l^–1 of Pb²⁺ respectively at pH 7. The results of these studies suggest that pyrolusite might provide an economical method for the removal of lead from industrial waste water.     

cDNA sequence encoding metallothionein protein from Aegiceras corniculatum and its gene expression induced by Pb2+ and Cd2+ stresses

Constructing various green wetland examples for mangrove wetland systems is a useful way to use natural power to remediate the polluted wetlands at intertidal zones. Metallothioneins (MT) are involved in heavy metal tolerance, homeostasis, and detoxification of intracellular metal ions in plants. In order to understand the mechanism of heavy metal uptake in Aegiceras corniculatum, we isolated its metallothionein gene and studied the MT gene expression in response to heavy metals contamination. Here, we report the isolation and characterization of MT2 genes from young stem tissues of A. corniculatum growing in the cadmium (Cd) and lead (Pb) polluted wetlands of Quanzhou Bay, southeast of China. The obtained cDNA sequence of MT is 512 bp in length, and it has an open reading frame encoding 79 amino acid residues with a molecular weight of 7.92 kDa and the theoretical isoelectric point of 4.55. The amino acids include 14 cysteine residues and 14 glycine residues. It is a non-transmembrane hydrophilic protein. Sequence and homology analysis showed the MT protein sequence shared more than 60 % homology with other plant type 2 MT-like protein genes. The results suggested that the expression level of MT gene of A. corniculatum young stems induced by a certain range concentration of Cd²⁺ and Pb²⁺ stresses (0.2 mmol L^?1 Pb²⁺, 1 mmol L^?1 Pb²⁺, 0.2 mmol L^?1 Pb²⁺, and 40 μmmol L^?1 Cd²⁺; 1 mmol L^?1 Pb²⁺ and 40 μmol L^?1 Cd²⁺) compared with control might show an adaptive protection. The expression levels of MT gene at 20 h stress treatment were higher than those at 480 h stress treatment. The expression levels of MT gene with 0.2 mmol L^?1 Pb²⁺ stress treatment were higher than those with 0.2 mmol L^?1 Pb²⁺ and 40 μmol L^?1 Cd²⁺ stress treatment, and the MT gene expression levels with 1 mmol L^?1 Pb²⁺ treatment were higher than those with 1 mmol L^?1 Pb²⁺ and 40 μmol L^?1 Cd²⁺ treatment. There exists an antagonistic action between Pb²⁺ and Cd²⁺ in the MT metabolization of A. corniculatum.     

Biosorption kinetics of heavy metals by leaf biomass of Jatropha curcas in single and multi-metal system

Biosorption of Cu²⁺, Zn²⁺, and Cr⁶⁺ from aqueous solutions by leaf biomass of Jatropha curcas was investigated as a function of biomass concentration, initial metal ion concentration, contact time, and pH of the solution systematically. The aim of this study was to optimize biosorption process and find out a suitable kinetic model for the metal removal in single and multi-metal system. The experimental data were analyzed using two sorption kinetic models, viz., pseudo-first- and pseudo-second-order equations, to determine the best fit equation for the biosorption of metal ions Cu²⁺, Zn²⁺, and Cr⁶⁺ onto the leaf biomass of J. curcas in different metal systems. The experimental data fitted well the pseudo-second-order equation and provided the best correlation for the biosorption process. The findings of the present investigation revealed that J. curcas leaf biomass was an eco-friendly and cost-effective biosorbent for the removal of heavy metal ions from wastewater.     

A field study of the relationship between sulfide-bound metals and bioaccumulation by Limnodrilus sp. in a heavily polluted river

Acid volatile sulfide (AVS) has been regarded as an important factor controlling metal bioavailability in anoxic sediments, but its effect on metal accumulation under natural conditions is poorly understood. Here, a field study of the influence of AVS on metal accumulation by Limnodrilus sp. in a heavily polluted river is provided. Most of the study area was subject to anaerobic and strongly reducing conditions, and the concentration of trace metals in surface sediments was high, as were the concentration of AVS and simultaneously extracted metals (SEM; average AVS?=?20.3 μmol g^?1, average ∑SEM₅?=?9.42 μmol g^?1; ∑SEM₅ refers to the sum of SEM_Cd, SEM_Cu, SEM_Pb, SEM_Ni, and SEM_Zn). Only a few species and small quantities of benthic invertebrates were found, and Limnodrilus sp. was dominant. There was no correlation between trace metal accumulation and (SEM-AVS), and in stations where (SEM-AVS) <0, the absolute value of bioaccumulation was high (average ∑BIO₅?=?4.07 μmol g^?1; ∑BIO₅ refers to the sum of BIO_Cd, BIO_Cu, BIO_Pb, BIO_Ni, and BIO_Zn), indicating that there was no relationship between (SEM–AVS) and metal accumulation in Limnodrilus sp. This was likely because Limnodrilus sp. ingest sediment particles as their main food source, so pore water metals play a minor role in their bioaccumulation (BIO) of materials. However, ∑BIO₅ was significantly correlated with ∑SEM₅ (r?=?0.795, p?<?0.01), revealing that the large number of sulfide-bound metals (SEM) in sediments may play an important role in metal accumulation in Limnodrilus sp., which can assimilate sulfide-associated metals by the help of the digestive fluids in the digestive systems.     

Incidence of metal and antibiotic resistance in Pseudomonas spp. from the river water, agricultural soil irrigated with wastewater and groundwater

A total of 144 isolates of Pseudomonas spp. (48 each from the Yamuna River water, wastewater irrigated soil and groundwater irrigated soil) were tested for their resistance against certain heavy metals and antibiotics. Minimum inhibitory concentrations (MICs) of Hg^2?+?, Cd^2?+?, Cu^2?+?, Zn^2?+?, Ni^2?+?, Pb^2?+?, Cr^3?+? and Cr^6?+? for each isolate were also determined. A maximum MIC of 200 ??g/ml for mercury and 3,200 ??g/ml for other metals were observed. The incidences of metal resistance and MICs of metals for Pseudomonas isolates from the Yamuna water and wastewater irrigated soil were significantly different to those of groundwater irrigated soil. A high level of resistance against tetracycline and polymyxin B (81.2%) was observed in river water isolates. However, 87.5% of Pseudomonas isolates from soil irrigated with wastewater showed resistance to sulphadiazine, whereas 79.1% were resistant to both ampicillin and erythromycin. Isolates from soil irrigated with groundwater exhibited less resistance towards heavy metals and antibiotics as compared to those of river water and wastewater irrigated soil. Majority of the Pseudomonas isolates from water and soil exhibited resistance to multiple metals and antibiotics. Resistance was transferable to recipient Escherichia coli AB2200 strains by conjugation. Plasmids were cured with the curing agent ethidium bromide and acridine orange at sub-MIC concentration.     

The influence of pH on trace element uptake by an alga (Scenedesmus pannonicus subsp. Berlin) and Fungus (Aureobasidium Pullulans)

Experiments were carried oud in order to obtain information on the uptake characteristics of metals in the algal and fungus components of lichens. The uptake of ¹¹⁵Cd, ⁶⁵Zn, ⁶⁴Cu, ¹⁴⁰La, ¹⁸⁷W, ⁷⁵Se, and ⁷⁶As in the alga Scenedesmus pannonicus, subsp. Berlin and the fungus Aureobasidium pullulans was determined during 11 days of incubation at pH 5 and pH 7. The results indicate different acid-sensitivity of the alga and the fungus. The metal uptake in the alga was generally faster at pH 7, in the fungus uptake rates were higher at pH 5. In both the alga and the fungus for different pH-values hardly any differences in ultimate metal levels could be observed for Cd²⁺, Zn²⁺, La³⁺, and SeO _inf3 ^sup2- . In algae, the ultimate levels of the accumulated anionic forms of W and As appeared to be independent of pH; in the fungi the ultimate W and As levels were higher at pH 5. No differences could be observed in the Zn²⁺ accumulation capacities of both organisms. The As accumulation capacity of the alga was estimated to be about 10 times the As uptake capacity of the fungus. The results indicate the component-specific uptake and accumulatiom behaviour in intact lichens.     

The influence of pre-treatment,temperature and calcium ions on trace element uptake by an alga (Scenedesmus pannonicus subsp. Berlin) and fungus (Aureobasidium pullulans)

Experiments were carried out in order to obtain information on the uptake characteristics of metals in the algal and fungal components of lichens. The uptake of ¹¹⁵Cd, ⁶⁵Zn, ⁶⁴Cu, ¹⁴⁰La, ¹⁸⁷W and ⁷⁶As in the alga Scenedesmus pannonicus, subsp. Berlin and the fungus Aureobasidium pullulans was determined at pH 7 and 5 respectively, in 4 h experiments varying with respect to temperature and Ca²⁺ solution concentrations. Furthermore, the effects of pre-rinsing the cell suspensions on metal uptake were investigated.Pre-rinsing resulted in decreased uptake of W and As by algae and in increased uptake of all elements measured by fungi, which may be attributed to combined effects of starvation and changing densities.For algae, the uptake rates of As, W, Zn and Cd were markedly increased at the highest temperature employed. For Cu and La hardly any effects of temperature were observed, indicating the absence of metabolically controlled uptake. For fungi, but for As no relation of uptake with temperature could be determined.The presence of Ca²⁺ ions in the solution applied hardly affected the uptake of As but resulted in increased uptake of W by both the algae and the fungi. The effects of Ca²⁺ on the uptake of Cu and La were relatively small, probably due to specific binding sites in the cell walls for Cu and to the supercalcium status of the La-ion.The presence of Ca²⁺ caused decreased uptake of Cd²⁺ and Zn²⁺ by algae, but hardly affected the uptake of Zn²⁺ by fungi.The results indicate component-specific uptake and accumulation behaviour in intact lichens.     

Five-year monitoring study of chemical characteristics of Wet atmospheric precipitation in the southern region of Jordan

Wet atmospheric samples were collected from different locations in the southern region of Jordan during a 5-year period (October 2006 to May 2011). All samples were analyzed for pH, EC, major ions (Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃ ^?, Cl^?, NO₃ ^?, and SO₄ ^2?), and trace metals (Fe²⁺, Al³⁺,Cu²⁺, Pb²⁺, and Zn²⁺). The highest ion concentrations were observed during the beginning of the rainfall events because large amounts of dust accumulated in the atmosphere during dry periods and were scavenged by rain. The rainwater in the study area is characterized by low salinity and neutral pH. The major ions found in rainwater followed the order of HCO₃?>?Cl^??>?SO₄ ^2? and Ca²⁺?>?Na⁺ > Mg²⁺ > NH₄ ⁺ > K⁺. Trace metals were identified to be of anthropogenic origin resulting from cement and phosphate mining activities located within the investigated area and from heating activities during the cold period of the year (January to April). The wet precipitation chemistry was analyzed using factor component analysis for possible sources of the measured species. Factor analysis (principal component analysis) was used to assess the relationships between the concentrations of the studied ions and their sources. Factor 1 represents the contribution of ions from local anthropogenic activities, factor 2 represents the contribution of ions from natural sources, and factor 3 suggests biomass burning and anthropogenic source. Overall, the results revealed that rainwater chemistry is strongly influenced by local anthropogenic sources rather than natural and marine sources, which is in a good agreement with the results obtained by other studies conducted in similar sites around the world.     

Hydrochemistry of Wet Atmospheric Precipitation Over an Urban Area in Northern Indo-Gangetic Plains

Rain water samples were collected to study the chemical composition of wet atmospheric precipitation (first event) over the Lucknow city in the northern Indo-gangetic alluvial plains. The samples were collected in the month of July, 2005 from different sites. The wet precipitation samples were analyzed for pH, EC, major ions (, Cl⁻, , , , F⁻, Na⁺, K⁺, Ca²⁺, Mg²⁺, ) and heavy metals (As, Cd, Al, Co, Cr, Cu, Fe, Mn, Mo, Ni, Hg, Pb, Se, Sn, Ti, V, Zn). The pH values of wet precipitation samples ranged between 6.5 and 8.7. The analysis of linear regression applied to the set of studied variables and computation of neutralization factors showed that neutralization occurred in precipitation samples and Ca²⁺ had the maximum neutralization capacity. It was found that Cl⁻, , Ca²⁺, Mg²⁺, Na⁺ and K⁺ in the precipitation samples originated mainly from crustal/anthropogenic sources in the region. On an average Fe, and Al accounted for >72% of the total concentration of trace metals in the wet precipitation samples followed by Zn (>10%). Enrichment factors calculated for heavy metals over reference background level in seawater and Earth’s crust showed relatively higher enrichment of Zn. The principal component analysis (PCA) identified the possible sources of ionic species and heavy metals in the wet precipitation samples.     

神经网络用于光度法同时测定多种重金属离子

采用可见分光光度法,通过构筑16-5-4多目标神经网络模型实现同时测定溶液中Cd2+、Pb2+、Cu2+、As3+的含量。实验以4-(2-吡啶偶氮)-间苯二酚(PAR)作为显色剂,采用"多因素多水平可视化设计法"设计样本,在4种组分可见吸收光谱严重重叠的390~480 nm范围内,选取16个特征波长处的吸光度作为输入信号,应用"留二法"原则训练BP网络。网络准确预测了结果,Cd2+、Pb2+、Cu2+、As3+的平均回收率分别为100.10%、100.03%、100.09%、99.99%,测定结果的相对标准偏差分别为0.18%、0.12%、0.26%、0.13%,达到了4种组分含量同时测定的目的。     

31P-NMR evaluation of organophosphorus pesticides degradation through metal ion promoted hydrolysis

The degradation of some organophosphorus pesticides (OPPs) in the presence of metal ions was studied by ³¹P-NMR spectroscopy. Both ³¹P-NMR and gas chromatography/mass spectroscopy results were used in order to determine the nature of metabolites formed after degradation. The degraded organophosphorus pesticide were investigated for chlorpyrifos and phoxim in the presence of several metal ions including Hg²⁺, Cu²⁺, Cd²⁺, Ni²⁺, Pb²⁺, and Ag⁺. ³¹P-NMR results indicated Ag⁺ and Hg²⁺ ion promoted degradation of OPPs and other metal ions formed complex with OPPs and cannot degrade OPPs. We found that the degradation of chlorpyrifos and phoxim with Ag⁺ or Hg²⁺ led to the formation of O,O-diethyl-O-methyl phosphorothionate, (C₂H₅O)₂(CH₃O)PS, at metal ion/pesticide mole ratios ≤1.0 and completely decomposed at a higher mole ratio of 10. Finally, the method was successfully applied to the degradation study of a number of technical and formulated pesticides in the presence of Ag⁺ ion at a metal ion/pesticide mole ratio of 10.     

Determination of EC 50 toxicity data of selected heavy metals toward Heterocypris incongruens and their comparison to ��direct-contact�� and microbiotests

The sensitivity of Heterocypris incongruens to selected heavy metal ions is discussed. Although the Ostracodtoxkit ${\textregistered}$ has been present on the market for a few years, data on its selectivity and sensitivity to toxicants is scarce; such data is indispensable when interpreting the results of sediment toxicity. The LC₅₀ and EC₅₀ results with the Ostracodtoxkit ${\textregistered}$ are compared with those obtained with other commercially available ??direct-contact?? tests (utilizing Hyalella azteca and Chironomus riparius) and microbiotests for assessing the toxicity of aqueous samples (Vibrio fischeri, Daphnia magna, and Selenastrum capricornatum). The sensitivity of H. incongruens to metal ions (Cd^2?+?>?>Hg^2?+?> Cu^2?+?>Cr^6?+?>Ni^2?+???Mn^7?+?>Zn^2?+?>Pb^2?+?>Li^1?+?> Fe^3?+?) was found to be similar to that of H. azteca and of C. riparius. The Ostracodtoxkit ${\textregistered}$ has shown itself to be an efficient and reliable element of test batteries for toxicity determination.     

Chemical speciation in waters influenced by lead–zinc metallurgical industry

The Lead–Zinc Company region, Kardjali city, Bulgaria, is known to be highly polluted with heavy metals from its pyrometallurgical activities. The polluted levels and the chemical speciation in surface natural waters in the region as well as in the wastewaters of the factory were investigated in January 2008 by application of monitoring studies, thermodynamic modeling, and interpretation in terms of the “softness–hardness” factor. It was found that the levels of trace metals pollution of surface waters were lower than the legislation limits for the regions with Pb and Zn production. The wastewater treatment facilities of the company were found to operate properly, and the quality of the cleaned waters in station Kar4 was comparable to the other surface waters studied (e.g., station Kar5). The trace metals were divided into three groups: (1) Fe^3?+? and Al^3?+?, being “hard” acids, existed in all the studied waters as hydroxy species Fe(OH) $_{2}^{+}$ , AlOH^2?+?, and Al(OH) $_{2}^{+}$ , followed by the phosphate species AlPO $_{4}^{0}$ and Al₂(OH)₂PO $_{4}^{+}$ ; (2) Mn^2?+?, Zn^2?+?, and Cd^2?+? being “soft” acids with crystal field stabilization energy (CFSE) = 0 were present in natural waters mainly as free Me^2?+? ions. Small concentrations of their MeSO $_{4}^{0}$ , MeCO $_{3}^{0}$ species, and of MeCl $_{2}^{0}$ (Me = Zn, Cd) species were also calculated. In the wastewaters, two more species [Me(SO $_{4})_{2}^{2-}$ and Me(SO $_{4})_{3}^{4-}$ ] of the softer Zn and Cd metals were also calculated; (3) Cu^2?+? and Pb^2?+?, as “soft” acids with CFSE $\ne $ 0 preferentially coordinated with softer CO $_{3}^{2-}$ ions and in natural waters existed mainly as MeCO $_{3}^{0}$ and PbHCO $_{3}^{+}$ , followed by free Me^2?+?ions and MeOH^?+?. In the wastewaters, MeSO $_{4}^{0}$ and Pb(SO $_{4})_{2}^{2-}$ species increased at the expense of the free Me^2?+? ions. The highest self-cleaning capability of natural waters was found with respect to Al and Fe, followed by Mn and Cd. The lowest corresponded to Pb, Cu, and Zn.     

The evaluation of the association constant between R-SN and Hg2+

The effective determination of heavy metals from environmental media is among the most important issues for many industrialized countries. The interaction between RS-N, as novel heavy metal probe, and metal ions was studied. RS-N shows selective color change from colorless to pink in the presence of Hg²⁺ in methanol/water solvent and the UV–Vis study shows peak at 560 nm. Fluorescence data revealed that the fluorescence enhance of RS-N by Hg²⁺ dramatically was the result of the formation of [Hg²⁺]RS-N complex. The effective association constants (K _a ) were 3.97?×?10⁵ and 0.204?×?10⁵ M^?1 for Hg²⁺ and Cu²⁺ to RS-N, respectively. The thermodynamic parameters, enthalpy change (ΔH ⁰) and entropy change (ΔS ⁰), were calculated to be ?6.431?±?0.226 kJ/mol and ?0.129?±?0.008 J/K/mol, respectively, according to van’t Hoff equation on the basis of Gibbs free energy (ΔG ⁰) ranged from ?33.8326 to ?28.5389 kJ/mol.     

多元线性回归-分光光度法测定电镀排放废水中重金属

采用多元线性回归-分光光度法进行电镀排放废水中Cr³⁺、Ni²⁺、Zn²⁺的同时测定研究。以4-(2-吡啶偶氮)间苯二酚(PAR)为显色剂，探索了同时测定模拟电镀废水中Cr³⁺、Ni²⁺、Zn²⁺的实验方法，建立多元线性回归模型。根据实际电镀排放废水中Cr³⁺、Ni²⁺、Zn²⁺的质量浓度分布调查结果，设计了测定较低和较高浓度范围2种模型，分别对应不同水质波动程度的电镀企业废水，前者浓度范围设置基本覆盖大多数实际电镀排放废水中Cr³⁺、Ni²⁺、Zn²⁺的浓度，且具有较高精度。测定浓度范围较小模型对应水质波动较小的电镀排放废水，模型中Cr³⁺、Ni²⁺、Zn²⁺的质量浓度分别为0.32～0.44、0.32～0.50、0.72～0.84 mg/L,平均相对误差MR...     

Comparative studies on accumulation of Cr from metal solution and tannery effluent under repeated metal exposure by aquatic plants: its toxic effects

The present study demonstrates comparison of Cr accumulatingpotential by the plants of Najas indica Cham. (submerged),Vallisneria spiralis L. (rooted submerged) and Alternanthera sessilis R. Br. (rooted emergent) under repeatedmetal exposure and its effect on chlorophyll and protein concentrations. These plants were treated with different concentrations of Cr under repeated exposure in controlled laboratory conditions to assess the maximum metal accumulationpotential. The plants of V. spiralis accumulated significantly high amount of Cr under laboratory conditions incomparison to N. indica and A. sessilis. The maximumaccumulation of 1378, 458 and 201 g g^-1 dw Cr was found in the leaves of V. spiralis, N. indica and A. sessilis, respectively at 8 mg L^-1 after 9 day of Cr exposure. These plants have shown a decrease in chlorophyll andprotein concentrations with increase in Cr concentrations. In view of high accumulation of Cr in V. spiralis, the plantswere treated with different concentrations of tannery effluent collected from Common Effluent Treatment Plant, Unnao (UP). Theplants of V. spiralis treated with 100% tannery wastewatershowed the maximum accumulation (57.5 g g^-1 dw) of Cr in the roots after 10 days of exposure. The plants were foundeffective in removing Cr from solution and tannery effluent.