PURPOSES AND AIMS: Economically efficient methods for removing arsenic from the drinking water supply are urgently needed in many parts of the world. Iron oxides are known to have a strong affinity for arsenic in water. However, they are commonly present in the forms of fine powder or floc, which limits their utility in water treatment. In this study, a novel granular adsorbent, iron-oxide-coated diatomite (IOCD), was developed and examined for its adsorption of arsenic from water. MATERIALS AND METHODS: An industrial-grade diatomite was used as the iron oxide support. The diatomite was first acidified and dried and then coated with iron oxide up to five times. The prepared IOCD samples were characterized for their morphology, composition, elemental content, and crystal properties by various instruments. Experiments of equilibrium and kinetic adsorption of As(V) on IOCD were conducted using 0.1- and 2-L polyethylene bottles, respectively, at different pH and temperatures. RESULTS: Iron oxide (α-Fe₂O₃ hematite) coated onto diatomite greatly improves (by about 30 times) the adsorption of As(V) from water by IOCD as compared to using raw diatomite. This improvement was attributed to increases in both surface affinity and surface area of the IOCD. The surface area of IOCD increased to an optimal value. However, as the IOCD surface area (93 m²/g) was only 45% higher than that of raw diatomite (51 m²/g), the enhanced As(V) adsorption resulted primarily from the enhanced association of negatively charged As(V) ions with the partial positive surface charge of the iron oxide. The As(V) adsorption decreased when the solution pH was increased from 3.5 to 9.5, as expected from the partial charge interaction between As(V) and IOCD. The adsorption data at pH 5.5 and 7.5 could be well fitted to the Freundlich equation. A moderately high exothermic heat was observed for the As(V) adsorption, with the calculated molar isosteric heat ranging from −4 to −9 kcal/mol. The observed heats fall between those for physical adsorption and chemisorption and are indicative of the formation of a series of ion-pair complexes of As(V) ions with iron oxide surface groups. CONCLUSIONS: This study demonstrated that the granular IOCD was successfully developed and employed to remove the As(V) in aqueous solution. The Freundlich isotherm well fitted the equilibrium adsorption data of As(V) onto IOCD, and both the pseudo-second-order model and the pore diffusion model simulated well the adsorption kinetics. Compared to other iron-oxide-based adsorbents reported in the literatures, the adsorption capacity of IOCD is relatively high and its kinetics is fast.

Background, aim and scope The importance of groundwater for human life cannot be overemphasised. Besides fulfilling essential ecological functions, it is a major source of drinking water. However, in the industrial area of Bitterfeld, it is contaminated with a multitude of harmful chemicals, including genotoxicants. Therefore, recently developed methodologies including preparative capillary gas chromatography (pcGC), MOLGEN-MS structure generation and mutagenicity prediction were applied within effect-directed analysis (EDA) to reduce sample complexity and to identify candidate mutagens in the samples. A major focus was put on the added value of these tools compared to conventional EDA combining reversed-phase liquid chromatography (RP-LC) followed by GC/MS analysis and MS library search. Materials and methods We combined genotoxicity testing with umuC and RP-LC with pcGC fractionation to isolate genotoxic compounds from a contaminated groundwater sample. Spectral library information from the NIST05 database was combined with a computer-based structure generation tool called MOLGEN-MS for structure elucidation of unknowns. Finally, we applied a computer model for mutagenicity prediction (ChemProp) to identify candidate mutagens and genotoxicants. Results and discussion A total of 62 components were tentatively identified in genotoxic fractions. Ten of these components were predicted to be potentially mutagenic, whilst 2,4,6-trichlorophenol, 2,4-dichloro-6-methylphenol and 4-chlorobenzoic acid were confirmed as genotoxicants. Conclusions and perspectives The results suggest pcGC as a high-resolution fractionation tool and MOLGEN-MS to improve structure elucidation, whilst mutagenicity prediction failed in our study to predict identified genotoxicants. Genotoxicity, mutagenicity and carcinogenicity caused by chemicals are complex processes, and prediction from chemical structure still appears to be quite difficult. Progress in this field would significantly support EDA and risk assessment of environmental mixtures.

Introduction Arsenic is a well known water contaminant that causes toxicological and carcinogenic effects. In this work magnetite nanoparticles were examined as possible arsenic sorbents. The objective of this work was to develop a sorption kinetics model, which could be used to predict the amount of arsenic adsorbed by magnetite nanoparticles in the presence of naturally occurring species using a first-order rate equation, modified to include adsorption, described by a Langmuir isotherm. Discussion Arsenate and arsenite adsorption to magnetite nanoparticles was studied, including the effect of naturally occurring species (sulfate, silica, calcium magnesium, dissolved organic matter, bicarbonate, iron, and phosphate) on adsorption. Conclusion The model accurately predicts adsorption to magnetite nanoparticles used in a batch process to remove arsenic from spiked Houston, TX tap water, and contaminated Brownsville, TX groundwater.

Purposes Very few data for polybrominated diphenyl ethers (PBDEs) were available in the Yangtze River Delta (YRD), one of the most developed and urbanized region in China. In this study, Chongming Island, located at the estuary of the Yangtze River, was selected as background area to investigate the occurrence, sources, and inventory of PBDEs. Methods Forty-two PBDE congeners were determined in surface soils from farmland, woodland, grassland, tideland, and road collected in Chongming Island. Results The mean concentrations of Σ₂₆PBDE (not including BDE-209) and BDE-209 in soils were 0.76 and 12 ng/g dry weight, respectively. BDE-209 contributed more than 90% of the total of 27 frequently detected BDE congeners, followed by BDE-99 and BDE-47. Weak correlations were found between total organic carbon content and PBDE congeners concentrations in surface soils. PBDE levels varied with land use. Farmland and woodland soils contained higher Σ₂₆PBDE concentrations. BDE-209 levels were the highest in road soils. The mass inventories of PBDEs in soils of Chongming Island were estimated at 3.1 and 310 kg for Σ₂₆PBDEs and BDE-209, respectively. Conclusions The PBDE levels in Chongming Island were similar to those in European background soils, suggesting minimum influence of pollutants from the YRD via air, and wastewater inputs or few PBDE products were used herein. From the standpoint of eco-inland, more studies are needed to explore the reasons of PBDE difference by land use and to assess people intake PBDEs via agriculture products consumption in this region.

Background, aim, and scope Experimental data on partition coefficients and environmental half-lives of sulfur analogs of polychlorinated organic compounds are scarce. Consequently, little is known about their overall persistence and long-range transport potential, which are the most vital measures in the environmental exposure assessment. We performed Multimedia Modeling of environmental fate and transport to complement this paucity of scientific data. The main aim of our study was to investigate whether the sulfur analogs of polychlorinated dibenzo-p-dioxins, -dibenzofurans, and -diphenylethers are as environmentally persistent and/or mobile as their oxygen counterparts and to propose the environmental exposure-related classification of the examined sulfur compounds. Materials and methods Our study included all possible congeners of the sulfur analogs generated in a combinatorial approach. We predicted (1) lacking data on partition coefficients (log K OW, log K OA and log K AW) for oxygen- and sulfur analogs using Quantitative Structure-Property Relationship (QSPR) modeling and (2) their half-lives in air, water, and soil using US EPA tool ‘The PBT Profiler, v. 1.203 2006'. Subsequently, we introduced these results into multimedia mass balance model ‘The OECD POV and LRTP Screening Tool, v. 2.2'. Results Our study revealed that log K OW and log K OA are increasing by constant values of 0.60 and 1.07, respectively, and the values of log K AW are decreasing by 0.90, whenever one oxygen atom in the carbon skeleton is replaced by sulfur. The persistence ranking performed by the PBT Profiler showed that PCDDs, PCDFs, PCDEs, and their sulfur analogs belong to one half-life class. Discussion The Multimedia Modeling by the means of ‘The OECD POV and LRTP Screening Tool, v. 2.2' suggested that the long-range transport potential depends on the presence/absence of oxygen/sulfur atoms in particular molecules, their substitution pattern and the parent carbon skeleton. Sulfur analogs are generally less mobile than their oxygen analogs, but have similar overall persistence and much higher bioaccumulation potential. Thus, according to the classification of chemicals proposed by Klasmeier et al. (Environ Sci Technol 40:53-60, 2006), some of them show POP-like POV and LRTP characteristics while the rest shows POP-like POV characteristics. Conclusions The sulfur analogs of PCDDs, PCDFs, or PCDEs bring environmental mobility comparable with the risk related to the oxygen ones; they belong to the pollutants of ‘highest' or ‘intermediate' priority. Recommendations and perspectives Further studies that would verify the necessity to include the studied sulfur molecules in the international lists of high-priority environmental pollutants are recommended.

Background, aim and scope For reliable environmental risk assessment of pollutants, knowledge on the effects at different levels of biological organisation is needed. During the early days of biomarker research in environmental studies approximately two decades ago, biochemical biomarkers were considered as the most promising tool for such purposes. Among these, three enzymes have often been studied: catalase (CAT), glutathione S-transferase (GST) and cholinesterase (ChE). However, despite their intensive research, their measurements in invertebrates have not been commonly applied in environmental risk assessment (ERA) or for regulatory purposes. Main features In the present review, we summarise our past experiences in biochemical biomarker research in two crustacean species: water flea Daphnia magna and terrestrial isopod Porcellio scaber. This is to orientate their use and to provide recommendations for the use of novel biomarkers in environmental studies, such as proteomic or genomic responses. Results and discussion We assessed the intrinsic properties of biochemical biomarkers CAT, GST and ChE in the D. magna and the isopod P. scaber. It was found that they are not in agreement with the expectations that were previously given for their use in environmental studies. To advance their use in environmental risk assessment, we suggest that based on their properties, their role should be more specifically defined. ERA includes several distinct steps, among them hazard identification, effect assessment and finally risk characterisation, each of which requires a different type of toxicity data. We recommend that the use of biochemical markers is most appropriate for hazard identification because this is a procedure whose purpose is to characterise the potential hazard of the substance in question and is more flexible in terms of using different tools. Furthermore, our results imply that biochemical markers are not always more sensitive than whole-organism responses, as was anticipated. Their sensitivity depends on the mode of action, duration of exposure and test species. Therefore, we suggest that combining both a battery of biomarkers from different levels of biological organisation and an array of biomarkers within a single level could identify hazard adequately. Conclusions The lesson learnt from biochemical biomarkers in environmental studies utilizing crustacean model species is that, for successful application of each group of biomarkers, their intrinsic properties are needed to be known before an (eco)toxicity study is designed. We suggest that a substantial body of experience obtained with biochemical biomarkers should be exploited to new emerging biomarkers in environmental studies in order to facilitate their application. Recommendations and perspectives The future of biomarkers lies in a combination of traditional biochemical and new-generation biomarkers. The latter are not only a potential replacement for existing biomarkers but will also provide new knowledge which might encourage renewed research and development of traditional biomarkers. For research purposes, complete ecotoxicity information should include contributions from molecular fingerprint of an organism, as well as whole organism, population and ecosystem responses. Still, the type of biomarkers used for routine purposes will depend on their reproducibility, their ease of use, robustness, affordability of the methodology and the type of chemicals, organisms and ecosystem of interest.

Introduction Isotope ratios of lead (²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb) in Japanese women's hair of the twentieth century were measured to evaluate lead contamination of human proximate environment of those days. Materials and Methods The historic hair samples (n = 40) were collected in 1980s by staffs of Department of Human Ecology, University of Tokyo, from Japanese women who cut their hair in 1910s to 1968 by themselves for hair piece or needle pad and who had stored it by the time of collection. Additional five contemporary hair samples (one from male and four from females) were also included. The hair samples were digested with HNO₃, diluted with water to Pb concentration of 10 µg/kg, and isotope ratios were measured by inductively coupled plasma mass spectrometry. Results and Discussion Isotope ratios as well as Pb concentration in the hair samples of the twentieth century varied to a considerable extent depending on the period of hair cut. The oldest hair samples (1910-1920s) had the highest concentration and the most distinct isotope ratios from those of Japanese domestic Pb indicating serious contamination of proximate environment of people of those days with Pb originated from mines in other regions of the world, probably through the usage of Pb-containing face powder. The concentration and isotope ratios of Pb decreased thereafter indicating less serious contamination of proximate environment of Japanese which, in turn, should have affected by environmental contamination of mid-twentieth century due to industrial activities and leaded gasoline. Contemporary Pb level was quite low (<1 mg/kg); however, isotope ratios were close to those in 1960s when hair concentration was assumed to be strongly affected by leaded gasoline.

Purpose China's freshwater subtropical shallow lakes are increasingly eutrophic and susceptible to production of heavy growths or water blooms of cyanobacteria. One example was the heavy water bloom that occurred for the first time in Lake Xuanwu, in 2005, an urban lake located in Nanjing city. The aim of the present study was to determine dynamics of water bloom dominating Microcystis in this lake. Meanwhile, the relationship between environmental factors and Microcystis populations was also analyzed. Materials and methods Molecular detection, using quantitative polymerase chain reaction, was used in this lake to study the dynamics of the cyanobacterial community, its Microcystis populations, and the microcystin-producing Microcystis genotypes from August 2005 to November 2006. Results It was shown that Microcystis wesenbergii and Microcystis aeruginosa were the main components of the cyanobacterial blooms in Lake Xuanwu, and they coexisted with species of the filamentous cyanobacterial genera Anabaena, Planktothrix, and Anabaenopsis. Microcystis cells were detected during the entire survey period and in all sample sites. The cell abundance of Microcystis ranged from 3.6 × 10² cells ml⁻¹ to a peak of 3.8 × 10⁶ cells ml⁻¹. The ratio of mcyB-containing Microcystis subpopulations to the total Microcystis varied, ranging from 0.1% to 12.8%. The abundance of Microcystis containing the mcyB microcystin gene was shown to be significantly correlated with concentrations of total phosphorus and phosphate. Conclusions Water temperature was the primary factor affecting Microcystis abundance in the lake, and phosphorus loading was shown to be a main factor in governing the growth of both microcystin-producing genotype and total Microcystis population. Higher Microcystis cell counts at the bottom of the water column before and after appearance of water blooms in Lake Xuanwu suggested that Microcystis numbers in the water column, especially at the bottom of the water column, play an important role in forming the next water bloom.

Purpose To protect the environmental quality of soil, groundwater, and surface water near the landfill site, it is necessary to make an accurate assessment of the heavy metal mobility. This study aims to present the bio-immobilization behavior of heavy metals in landfill and provide some reference suggestion for the manipulation of heavy metal pollution control after closure. Materials and methods Two simulated bioreactor landfill system loaded with real municipal solid waste (MSW), namely, conventional bioreactor landfill (CL) and leachate recirculated bioreactor landfill (RL), were operated. Cu and Zn, the two conventional heavy metals with the highest contents in MSW, were chosen to track the heavy metal bio-immobilization behavior in landfill. Results The MSW in landfill is a great threat to environment because much of the heavy metal is “hidden” in different components. The weight ratio of Cu and Zn in landfill amounts to 0.00427% and 0.00437%, respectively. The accumulated effluent masses of Cu and Zn in CL increased all along, while they still kept at a stable level after day 105 in RL. Conclusions The microbes like sulfate-reducing bacteria mediate the behavior of Cu and Zn in bioreactor landfill system. Cu and Zn can be bio-immobilized in bioreactor landfill system with leachate recirculation like RL.

Background, aim, and scope Chlorinated volatile organic compounds (CVOCs), widely used in industry as solvents and chemical intermediates in the production of synthetic resins, plastics, and pharmaceuticals, are highly toxic to the environment and public health. Various studies reported that Fenton's oxidation could degrade a variety of chlorinated VOCs in aqueous solutions. In acidic conditions, ferrous ion catalyzes the decomposition of H₂O₂ to form a powerful •OH radical. In this study, wastewater from wash of ion-exchange resin containing typical CVOC, 1,2-dichloroethane, was treated using Fenton's oxidation. To reduce environmental load and processing costs of wastewater, Fenton process as a simple and efficient treatment method was applied to degrade 1,2-dichloroethane of wash water. Materials and methods The water samples were collected from three different washing stages of ion-exchange resin. The degradation of 1,2-dichloroethane and total organic carbon (TOC) of wash water of ion-exchange resin by Fenton process was studied with response surface method (RSM). Design of the experiments was conducted by central composite face, and factors included in three models were Fe²⁺ and H₂O₂ doses and treatment time. Relevant quadratic and interaction terms of factors were investigated. Results According to ANOVA, the model predicts well 1,2-dichloroethane reduction of all water samples and TOC reduction of samples 2 and 3. The Fe²⁺ and H₂O₂ doses used in the present study were most suitable when 1,2-dichloroethane concentration of the wash water is about 120 mg L⁻¹. In that case, Fenton's oxidation reduced 1,2-dichloroethane and TOC up to 100% and 87%, respectively, according to the RSM model. With 90-min reaction time and H₂O₂ dose of 1,200 mg L⁻¹, the required Fe²⁺ doses for 1,2-dichloroethane and TOC were 300 and 900 mg L⁻¹, respectively. The optimal H₂O₂/Fe²⁺ stoichiometric molar ratio was between 4-6. Then, concentration of Fe²⁺ was low enough and the amount of residual sludge can thus be reduced. It seems that most of TOC and part of 1,2-dichloroethane were removed by coagulation. Discussion Up to a certain extent, increase of Fe²⁺ and H₂O₂ doses improved the removal of 1,2-dichloroethane and TOC. High Fe²⁺ doses increased the formation of ferric-based sludge, and excessive H₂O₂ doses in sample 2 decreased the degradation of 1,2-dichloroethane. Excess amount of hydrogen peroxide may scavenge hydroxyl radicals, thus leading to loss of oxidative power. Also, the residual hydrogen peroxide of different samples increased with increasing H₂O₂ dose and H₂O₂/Fe²⁺ molar ratio and decreasing treatment time probably also due to scavenging reactions. Due to the saturated nature of 1,2-dichloroethane, the oxidation mechanism involves hydrogen abstraction before addition of hydroxyl radical, thus leading to lower rate constants than for direct hydroxyl radical attack, which for one increases the treatment time. Conclusions Complete removal of 1,2-dichloroethane was attained with initial concentration <120 mg L⁻¹. Also, TOC degraded effectively. Wash water with higher concentration of 1,2-dichloroethane requires longer treatment times and higher concentrations of Fe²⁺ and H₂O₂ for sufficient 1,2-dichloroethane removal. Recommendations and perspectives Due to the results achieved in this study, Fenton's oxidation could be recommended to be used for organic destruction of wash water of ion-exchange resin. Residual sludge, the main disadvantage in Fenton process, can be reduced by optimizing the ferrous dose or by using heterogeneous treatment where most of the reusable iron remains in the solid phase.