Comparative effects of trivalent and hexavalent chromium on spermatogenesis of the mouse

It has been repeatedly stressed that the biological effectiveness of chromium depends entirely on its oxidation state. The present work compares the histological effects of ingested trivalent and hexavalent chromium compounds on the mouse testes. The results showed comparable data of food consumption and gain in body weight. Both compounds produced ambiguous levels of degeneration in the outmost cellular layers of a number of seminiferous tubules, reduced the number of spermatogonia per tubule and the sperm count, and caused significant increases in the percentage of morphologically abnormal sperms. Generally, all these effects were more pronounced in animals which ingested the hexavalent chromium.     

纳米Fe0对Cr（VI）的还原及其影响因素

采用纳米Fe0还原水溶液中的Cr（Ⅵ）,考察纳米Fe0投加量、Cr（Ⅵ）初始浓度、溶液pH值和有机酸等因素对cr（Ⅵ）还原的影响。结果表明,纳米Fe。对Cr（Ⅵ）的还原效果明显,其对Cr（Ⅵ）的还原率分别是铁粉和铁屑的7和13倍。Cr（Ⅵ）溶液初始质量浓度为20mg·L-1、Fe。投加量为5g·L“条件下,反应24h时纳米Fe0对Cr（Ⅵ）的还原率达82．7％。溶液低pH值可以促进Fe。的腐蚀速度,提高反应速率,当pH值为3．0时还原效果最好。草酸、丙二酸和丁二酸对纳米Fe。还原Cr（Ⅵ）均有明显的促进作用,3种有机酸对Cr（Ⅵ）还原率的提高幅度由高到低依次为草酸、丙二酸和丁二酸。     

Biosorption of hexavalent chromium and malachite green from aqueous effluents,using Cladophora sp.

Biosorption potential of green macroalgae Cladophora sp., (GAC) for the removal of hexavalent chromium (Cr(VI)) and malachite green (MG) from aqueous medium was investigated. Optimal conditions for biosorption experiments were determined as a function of initial pH, GAC dosage, temperature and initial concentration of Cr(VI) and MG. The biosorption equilibrium data were fitted with the isotherm models of Langmuir, Freundlich, Kiselev, Frumkin and Jovanovic, while the experimental data were analysed using the kinetic models such as pseudo-first-order, pseudo-second-order, Ritchie's and intraparticle diffusion. The Langmuir maximum biosorption capacity was calculated as 100.00?mg/g (Cr(VI)) and 142.85?mg/g (MG). The biosorption kinetic data showed better agreement with the pseudo-second-order kinetic model. The thermodynamic parameters indicated spontaneous and endothermic nature of the biosorption process for Cr(VI) removal, whereas exothermic in the case of MG removal. Furthermore, the biosorption efficiencies of the GAC reusability were found significant up to five cycles and tested using 0.1, 0.5 and 1.0?M HCl, respectively. The results of the present study indicated that GAC is a suitable biosorbent for the sequestration of Cr(VI) and MG from aqueous solutions.     

Influence of iron plaque on chromium accumulation and translocation in three rice (Oryza sativa L.) cultivars grown in solution culture

Hydroponic experiments were conducted to investigate the role of iron plaque on root surface in chromium accumulation and translocation in three rice cultivars (90-68-2, CDR22 and Jin 23A). Rice seedlings were grown under 1.0 mg L^?1 trivalent chromium (Cr(III)) stress with and without phosphorus (P) treatments. P addition significantly increased the shoot and root biomass in all three rice cultivars. In the absence of P, the amounts of iron plaque (DCB-extractable Fe) on the root surface increased resulting in the increase of Cr accumulation in iron plaque. Compared to that with P treatment, Cr concentrations in iron plaque without P treatment were enhanced by 2–3 folds in the three rice cultivars. There was a significantly positive correlation between DCB-extractable Cr and DCB-extractable Fe on the root surface of the three rice cultivars. There were no significant effects on Cr concentration in roots and shoots between P treatments, but significant differences among cultivars were observed. Cultivar Jin 23A had the lowest Cr concentration both in roots and shoots regardless of P treatment. The results suggest that iron plaque could be a trap for immobilising Cr from environment but may not affect Cr uptake and translocation. Screening and breeding the cultivars with low Cr accumulation is considered as the most effective approach in Cr contaminated areas.     

Equilibrium,kinetics and thermodynamics of hexavalent chromium biosorption on pristine and zinc chloride activated Senna siamea seed pods

Hexavalent chromium contamination in water is an issue of huge concern due to its use at a high scale, toxicity and non-biodegradability. Biosorption is a cost effective and unconventional strategy for the elimination of Cr(VI). Here, a novel biosorbent Senna siamea seed pod biomass and its chemically activated form have been investigated for the elimination of hexavalent chromium from aqueous solution. The biosorbent was characterized by using BET, FTIR, FESEM-EDX and TGA techniques. Parameters controlling the biosorption process were optimized as pH 2.0, temperature 30°C, initial Cr(VI) concentration 500?mg/L, biosorbent dose 0.5?g/L. Optimized contact time was 210 and 180 min for pristine biomass and activated carbon, respectively. Langmuir isotherm correlated well with experimental data revealing that the biosorption occurred in monolayer pattern. Maximum biosorption capacity calculated by Langmuir biosorption isotherm was 119.18 and 139.86?mg/g for S. siamea pristine biomass and activated carbon, respectively. Pseudo-second order kinetic model correlated well with experimental data. Thermodynamic studies suggested that the biosorption process occurs in a non-spontaneous, stable and endothermic manner. These interesting findings on Cr(VI) biosorption by S. siamea seed pod biomass and S. siamea zinc chloride activated carbon vouches for its potential application as an unconventional biosorbent.     

Removal of contaminants in leachate from landfill by waste steel scrap and converter slag

This study may be the first investigation to be performed into the potential benefits of recycling industrial waste in controlling contaminants in leachate. Batch reactors were used to evaluate the efficacy of waste steel scrap and converter slag to treat mixed contaminants using mimic leachate solution. The waste steel scrap was prepared through pre-treatment by an acid-washed step, which retained both zero-valent iron site and iron oxide site. Extensive trichloroethene (TCE) removal (95%) occurred by acid-washed steel scrap within 48 h. In addition, dehalogenation (Cl⁻ production) was observed to be above 7.5% of the added TCE on a molar basis for 48 h. The waste steel scrap also removed tetrachloroethylene (PCE) through the dehalogenation process although to a lesser extent than TCE. Heavy metals (Cr, Mn, Cu, Zn, As, Cd, and Pb) were extensively removed by both acid-washed steel scrap and converter slag through the adsorption process. Among salt ions (NH₄⁺, NO₃⁻, and PO₄³⁻), PO₄³⁻ was removed by both waste steel scrap (100% within 8 h) and converter slag (100% within 20 min), whereas NO₃^- and NH₄⁺ were removed by waste steel scrap (100% within 7 days) and converter slag (up to 50% within 4 days) respectively. This work suggests that permeable reactive barriers (PRBs) with waste steel scrap and converter slag might be an effective approach to intercepting mixed contaminants in leachate from landfill.     

Electroreduction of hexavalent chromium using a porous titanium flow-through electrode and intelligent prediction based on a back propagation neural network

● Titanium-based flow-through electrode achieved high Cr(VI) reduction efficiency. ● Flow-through pattern enhanced the mass transfer and reduced cathodic polarization. ● BPNN predicted the optimal electroreduction conditions of flow-through cell. Flow-through electrodes have been demonstrated to be effective for electroreduction of Cr(VI), but shortcomings are tedious preparation and short lifetimes. Herein, porous titanium available in the market was studied as a flow-through electrode for Cr(VI) electroreduction. In addition, the intelligent prediction of electrolytic performance based on a back propagation neural network (BPNN) was developed. Voltametric studies revealed that Cr(VI) electroreduction was a diffusion-controlled process. Use of the flow-through mode achieved a high limiting diffusion current as a result of enhanced mass transfer and favorable kinetics. Electroreduction of Cr(VI) in the flow-through system was 1.95 times higher than in a parallel-plate electrode system. When the influent (initial pH 2.0 and 106 mg/L Cr(VI)) was treated at 5.0 V and a flux of 51 L/(h·m²), a reduction efficiency of ~99.9% was obtained without cyclic electrolysis process. Sulfate served as the supporting electrolyte and pH regulator, as reactive CrSO₇²⁻ species were formed as a result of feeding HSO₄⁻. Cr(III) was confirmed as the final product due to the sequential three-electron transport or disproportionation of the intermediate. The developed BPNN model achieved good prediction accuracy with respect to Cr(VI) electroreduction with a high correlation coefficient (R² = 0.943). Additionally, the electroreduction efficiencies for various operating inputs were predicted based on the BPNN model, which demonstrates the evolutionary role of intelligent systems in future electrochemical technologies.     

陕西某地区地下水Cr(Ⅵ)异常的水化学特征及其富集因素分析

以42组水化学测试数据为基础,结合野外调查资料,分析研究区Cr(Ⅵ)异常地下水的分布规律和水化学特征,探讨Cr(Ⅵ)富集的影响因素.结果表明Cr(Ⅵ)异常地下水主要位于基岩含水层,水化学类型以HCO3-Na、HCO3-Na·Ca型为主,随地下水埋深的增加,Cr(Ⅵ)浓度、γNa+/γCl-系数逐渐增大,γCa2+/γHCO-3系数逐渐减小;与正常水相比,Cr(Ⅵ)异常地下水的p H、溶解氧、离子强度的平均值分别由7.2、4.3 mg·L-1、0.011 mol·L-1变为7.6、5.5 mg·L-1、0.028 mol·L-1,溶解氧增加有利于Cr(Ⅲ)的氧化,p H升高、离子强度降低可以促进Cr(Ⅵ)的活化,这些是促使含水介质中Cr(Ⅵ)的解吸、迁移和富集的主要水化学因素.     

地下环境中铁氧化物生物异化还原耦合降解硝基苯的影响因素研究

通过静态实验模拟地下水厌氧环境,研究了碳源、电子受体、初始微生物量和硝基苯浓度等因素对地下环境中微生物异化铁还原作用耦合降解硝基苯的影响。实验选取乙酸铵、葡萄糖、柠檬酸铵为碳源,针铁矿、赤铁矿为电子受体,进行异化铁还原协同耦合降解硝基苯。结果表明：乙酸铵为碳源时硝基苯的降解率最高为78.5%;针铁矿作电子受体时硝基苯降解效果比赤铁矿好,且0.3 mg·L-1效果最好;微生物量对耦合体系中硝基苯降解率有影响但并不显著,最适宜的初始微生物量为4×108cells·mL-1;硝基苯质量浓度在50～150 mg·L-1时,硝基苯浓度与降解率呈负相关,其中对50 mg·L-1的初始硝基苯质量浓度降解效果最好。因此,碳源和电子受体对地下环境中微生物异化铁还原作用耦合降解硝基苯具有重要的影响。     

Effects of reducing agent and approaching anodes on chromium removal in electrokinetic soil remediation

A soil remediation method combining in situ reduction of Cr(VI) with approaching anodes electrokinetic (AAs-EK) remediation is proposed. EK experiments were conducted to compare the effect of approaching anodes (AAs) and fixed electrodes (FEs) with and without sodium bisulfite (NaHSO₃) as a reducing agent. When NaHSO₃ was added to the soil before EK treatment, 90.3% of the Cr(VI) was reduced to Cr(III). EK experiments showed that the adverse effect of contrasting migration of Cr(III) and Cr(VI) species, which limits the practical application of this technique, was eliminated in the presence of the reducing agent. Furthermore, Tessier fractionation analysis indicated that the reducing agent changed the distribution of the chemical forms of Cr. The AAs-EK method was shown to acidize the soil as the anode moved toward the cathode and this acid front pushed the “focusing” region toward the cathode. After remediation, the pH of the soil was between 1.8 and 5.0 in AAs-EK experiments. The total Cr removal efficiency was 64.4% (except in the “focusing” region) when the reduction reaction was combined with AAs-EK method. We conclude that AAs-EK remediation in the presence of NaHSO₃ is an appropriate method for Cr-contaminated soil.     

Bioreduction of hexavalent chromium by Exiguobacterium indicum strain MW1 isolated from marine water of Paradip Port,Odisha, India

Hexavalent chromium-tolerant (1500?mg/L) bacterium MW1 was isolated from harbour water of Paradip Port and evaluated for Cr(VI) reduction potential. The isolate was identified as Exiguobacterium indicum by biochemical and 16S rRNA gene sequence methods. Salt tolerance of the bacterium was evaluated in a wide range of NaCl concentrations (0.5–13%, w/v). The Cr(VI) reduction of the strain was evaluated and optimised with varied Cr(VI) concentrations (100–1000?mg/L), pH (5.0–9.0), temperature (30–40°C) and shaking velocity (100–150?rpm) in two different minimal media (M9 and Acetate). Under optimised conditions, after 192?h of incubation nearly 92%, 50% and 46% reduction in the M9 minimal medium and 91%, 47% and 40% reduction in the acetate minimal medium were observed for 100, 500 and 1000?mg/L of Cr(VI), respectively. The exponential rate equation for Cr(VI) reduction yielded higher rate constant value, that is, 1.27?×?10^?2?h^?1 (M9) and 1.17?×?10^?2?h^?1 (Acetate) in case of 100?mg/L and became lower for 500 and 1000?mg/L Cr(VI) concentrations. Further, the association of bacterial cells with reduced product was ascertained by Fourier transform infrared spectrometer, UV–Vis–DRS and field-emission scanning electron microscope–energy-dispersive X-ray analyses. The above study suggests that the higher reducing ability of the marine bacterium E. indicum MW1 will be suitable for Cr(VI) reduction from saline effluents.     

纳米零价铁颗粒去除水中重金属的研究进展

重金属是毒性大、难降解、易累积的环境污染物,纳米零价铁作为一种新型功能修复材料在去除水体和土壤中重金属方面有着广阔的应用前景.本文综述了纳米零价铁颗粒去除水中重金属的研究进展,包括纳米零价铁的常用制备方法及特性、去除效能、对不同重金属的去除机理以及发展前景和今后的研究方向,以期为该领域的深入研究提供借鉴并拓展新的思路.     

Stabilization of hexavalent chromium with pretreatment and high temperature sintering in highly contaminated soil

• Separate reduction and sintering cannot be effective for Cr stabilization. • Combined treatment of reduction and sintering is effective for Cr stabilization. • Almost all the Cr in the reduced soil is residual form after sintering at 1000°C. This study explored the effectiveness and mechanisms of high temperature sintering following pre-reduction with ferric sulfate (FeSO₄), sodium sulfide (Na₂S), or citric acid (C₆H₈O₇) in stabilizing hexavalent chromium (Cr(VI)) in highly contaminated soil. The soil samples had an initial total Cr leaching of 1768.83 mg/L, and Cr(VI) leaching of 1745.13 mg/L. When FeSO₄ or C₆H₈O₇ reduction was followed by sintering at 1000°C, the Cr leaching was reduced enough to meet the Safety Landfill Standards regarding general industrial solid waste. This combined treatment greatly improved the stabilization efficiency of chromium because the reduction of Cr(VI) into Cr(III) decreased the mobility of chromium and made it more easily encapsulated in minerals during sintering. SEM, XRD, TG-DSC, and speciation analysis indicated that when the sintering temperature reached 1000°C, almost all the chromium in soils that had the pre-reduction treatment was transformed into the residual form. At 1000°C, the soil melted and promoted the mineralization of Cr and the formation of new Cr-containing compounds, which significantly decreased subsequent leaching of chromium from the soil. However, without reduction treatment, chromium continued to leach from the soil even after being sintered at 1000°C, possibly because the soil did not fully fuse and because Cr(VI) does not bind with soil as easily as Cr(III).     

Leaching of metals in buried industrial sludge,spiked with cadmium,chromium and lead. Results of a trial

Sludge resulting from industrial waste water treatment at the industrial area of Patras, Greece, was spiked with cadmium, chromium and lead and entrenched in 4 experimental trenches. Soil from the unsaturated zone and sludge from the trenches were sampled at successive time points over a period of 14 months to monitor the movement of metals. Results showed that 94% of cadmium and 80% of lead but only 32% of chromium migrated from the sludge just 14 months after the entrenchment.

At the end of this time the buried sludge could be considered stabilised, as indicated by the total nitrogen content. Cd content in underlying soil layers at 3 m depth showed an increase in the first 7 months followed by a decrease, afterwards. Soil Pb concentration at 3 and 6 m depth was significantly high, in relation to it's initial concentration 14 months after the entrenchment. Pb and Cd in the soil samples were negatively correlated. It is suggested that lead displaces cadmium in the sediments.     

Process control factors for continuous microbial perchlorate reduction in the presence of zero-valent iron

Process control parameters influencing microbial perchlorate reduction via a flow-through zero-valent iron （ZVI） column reactor were investigated in order to optimize perchlorate removal from water. Mixed perchlorate reducers were obtained from a wastewater treatment plant and inoculated into the reactor without further acclimation. Examined parameters included hydraulic residence time （HRT）, pH, nutrients requirement, and perchlorate reduction kinetics. The minimum HRT for the system was concluded to be 8 hr. The removal efficiency of 10 mg. L-1 influent perchlorate concentration was reduced by 20%-80% without control to the neutral pH （HRT = 8 hr）. Therefore pH was determined to be an important parameter for microbial perchlorate reduction. Furthermore, a viable alternative to pH buffer was discussed. The microbial perchlorate reduction followed the first order kinetics, with a rate constant （K） of 0.761 hr-1. The results from this study will contribute to the implementation of a safe, cost effective, and efficient system for perchlorate reduction to below regulated levels.     

我国六价铬淡水水生生物安全基准推导研究

参照美国国家环境保护局(USEPA)"推导保护水生生物及其用途的国家水质基准的技术指南"的程序和规范,筛选了我国广泛存在的淡水水生生物物种,收集现有的急性和慢性毒性数据,结合课题组实验得到的部分本土生物毒性数据,分别采用物种敏感度排序法(SSR)、物种敏感度分布法(SSD)以及澳大利亚的水质基准技术方法对我国六价铬的淡水水生生物安全基准进行了推导。获得了我国淡水水生生物的六价铬的双值基准,3种方法得到的基准最大浓度(CMC)分别为23.97、22.84、29.06μg·L-1,基准连续浓度(CCC)分别为14.63、10.35、9.00μg·L-1,在同一个数量级上,但与美国的基准值有一些差异,建议使用SSD法推导CMC值和CCC值。研究结果可为我国水质基准的制定提供一些有用的基础资料。     

北方某市城区水环境中轮状病毒的初步检测

轮状病毒(Rotavirus,RV)是引起全世界婴幼儿肠胃炎的最主要病原体.在我国,儿童秋季腹泻发病达到高峰,也主要由轮状病毒引起.论文改进了RT-nested-PCR检测水中轮状病毒的方法,于2006年10月对北方某市城区水环境(包括污水、地表水和饮用水)中的轮状病毒进行了初步检测.结果表明,该市某污水厂进水和不同工艺段出水、主要公园的景观水体、主要自来水厂进水和出水以及城区管网水,均检出轮状病毒.综合分析从水源到管网的过程,认为管网水中的轮状病毒可能与水源水污染有关.管网水中有轮状病毒检出,说明秋季该市饮用水中存在潜在的轮状病毒传染源.同期对管网水进行的细菌学指标检测,没有发现总大肠菌群、耐热大肠菌群、粪链球菌,可见目前城市供水水质标准中的细菌学指标并不能准确反映病毒污染状况.     

Effect of nitrobenzene on the performance and bacterial community in an expanded granular sludge bed reactor treating high-sulfate organic wastewater

Less than 50 mg/L nitrobenzene brought little effect on anaerobic sulfate reduction. Kinetics of sulfate reduction under different nitrobenzene contents was studied. Increased nitrobenzene contents greatly changed the bacterial community structure. Genus Desulfovibrio played the key role in anaerobic sulfate reduction process. Nitrobenzene (NB) is frequently found in wastewaters containing sulfate and may affect biological sulfate reduction process, but information is limited on the responses of sulfate reduction efficiency and microbial community to the increased NB contents. In this study, a laboratory-scale expanded granular sludge bed reactor was operated continuously to treat high-sulfate organic wastewater with increased NB contents. Results successfully demonstrated that the presence of more than 50 mg/L NB depressed sulfate reduction and such inhibition was partly reversible. Bath experiments showed that the maximum specific desulfuration activity (SDA) decreased from 135.80 mg SO₄^2?/gVSS/d to 30.78 mg SO₄^2?/gVSS/d when the NB contents increased from none to 400 mg/L. High-throughput sequencing showed that NB also greatly affected bacterial community structure. Bacteroidetes dominated in the bioreactor. The abundance of Proteobacteria increased with NB addition while Firmicutes presented an opposite trend. Proteobacteria gradually replaced Firmicutes for the dominance in response to the increase of influent NB concentrations. The genus Desulfovibrio was the dominant sulfate-reducing bacteria (SRB) with absence or presence of NB, but was inhibited under high content of NB. The results provided better understanding for the biological sulfate reduction under NB stress.     

Effects of carrier-attached biofilm on oxygen transfer efficiency in a moving bed biofilm reactor

Three laboratory-scale moving bed biofilm reactors (MBBR) with different carrier filling ratios ranging from 40% to 60% were used to study the effects of carrier-attached biofilm on oxygen transfer efficiency. In this study, we evaluated the performance of three MBBRs in degrading chemical oxygen demand and ammonia. The three reactors removed more than 95% of NH ₄ ⁺ -N at an air flow-rate of 60 L·h^–1. The standard oxygen transfer efficiency (αSOTE) of the three reactors was also investigated at air flow-rates ranging from 60 to 100 L·h^–1. These results were compared to αSOTE of wastewater with a clean carrier (no biofilm attached). Results showed that under these process conditions, αSOTE decreased by approximately 70% as compared to αSOTE of wastewater at a different carrier-filling ratio. This indicated that the biofilm attached to the carrier had a negative effect on αSOTE. Mechanism analysis showed that the main inhibiting effects were related to biofilm flocculants and soluble microbial product (SMP). Biofilm flocs could decrease αSOTE by about 20%, and SMP could decrease αSOTE by 30%–50%.     

Wetlands and forest with a flora and fauna of international importance in Northeastern Greece

Due to Mediterranean, continental and oceanic influences we find in Northeastern Greece an exceptionally rich flora and fauna. Distributed over a distance of only 60–70 km from sea level northward to the Rhodopi mountains (with very cold and snowy winters at a height of 1000 m to 1600 m near the Bulgarian border) emerges a complex sequence of biozones unparalleled in a comparably small area in Europe. The low population density and the poor development of industry has allowed some natural landscapes to remain relatively undisturbed. The wetlands, including lake Kerkini and lake Vistonis as well as the deltas of the rivers Nestos and Evros, are a home or hibernating place for a large avifauna that includes vanishing bird species. In the oak‐ and beech‐forests of Rhodopi mountains, unusually rich in flowers, e.g. orchids, most of the large European mammals, including bear, wolf and wild boar, as well as birds of prey still find a basis for living. Pollution and damming of waters, erosion, cutting of riparian forests and overgrazing by domesticated animals are among other serious threats to the whole area. Problems, tasks and possibilities for protecting these zones of extraordinary quality are to be discussed along with an ecodevelopment concept for the whole region.