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The electronic tongue (ET) system contains an ion selective electrode (ISE) array, with a signal recording system and data processing methodology. It is developed for simultaneous determination of multiple free ions dissolved in solutions for real-time in situmonitoring. This article outlines an application of the ET system to determine chloride (Cl) simultaneously, and multi cationic metal ions, including calcium (Ca), cadmium (Cd), copper (Cu) and lead (Pb). In this study, Principal Component Analysis (PCA) was applied as a data compaction technique to reduce the complexity of data from the ISE array without losing much information. A patent data preprocessing method, geneticICA, was utilized to improve the prediction accuracy of ANN. Moreover, Orthogonal Experiment Design was employed for minimizing the number of training samples without losing any quality characteristics for the specific ions. Using our methodology means that results can be obtained rapidly and accurately without disturbing the natural speciation. The robustness and appropriateness of the approach were assessed using the mean relative error (MRE). When configured and optimized, the ET system can quantify the concentration of the four desired metals and chloride with the average MRE being lower than 0.10. Refereed/Peer-reviewed

With proper training procedures, including the use of a sufficiently large training sample set, ISE array with Back-Propagation Neural Networks (BPNNs) can be used to simultaneously determine the concentrations for multiple ions in environmental water. However, it is not practical for end-users to re-measure the whole training sample set - dozens of samples - to re-build the BPNN model every time after a long storage or measurement period, since both the sensitivity and selectivity of ISEs would be gradually degraded over time. In this study, instead of using BPNNs, we developed and patented some mathematical models to describe the based characteristics of the ISE array's response, including the sensitivity and selectivity. The developed mathematical equations can be used to simulate the response values of ISE array, and to determine the analytes' concentrations from unknown samples. By measuring only a couple of standard solutions, which are practical to the end users, the ISE array can be automatically recalibrated using genetic algorithm (GA). This research is based on an array of Prussian blue modified Carbon Paste Electrodes (PB-CPEs), and the interferences between nitrate (NO3) and chloride (Cl) was used as a case study. Refereed/Peer-reviewed

Nanoscale zero-valent iron (nZVI) has received attention for its potential applications in contaminated site remediation due to its reactivity. However, it is still unclear how nZVI acts as a catalyst to generate sulfate radicals in heterogeneous Fenton oxidation of 2,4-dichlorophenol (DCP). In this paper, various Fe materials such as Fe 2+ , nano-ZVI, and nano-Fe 3 O 4 (nFe 3 O 4 ) were used as heterogeneous catalysts, where the removals of DCP by Fe 2+ , nZVI, and nFe 3 O 4 were 11.9%, 9.0%, and 5.5%, while the degradation of DCP in the presence of persulfate increased to 34.4%, 37.8%, and 5.8%, respectively. These data indicate nZVI can potentially generate sulfate radicals. UV, SEM, EDS and XRD demonstrated that changes on the surface of nZVI occurred owing to the Fe 2+ leaching. It was further observed that DCP degradation increased when the dosage of nZVI and persulfate concentration also increased. However, it decreased when the initial pH and DCP concentration increased. More than 98% of DCP degradation was achieved within 180 min under optimum conditions, but less than 40% of chemical oxygen demand (COD) was removed. The degradation of DCP follows the pseudo-first-order kinetics and it is a chemical control reaction with an activation energy of 91.5 kJ mol −1 . Finally, a possible mechanism of DCP degradation using the nZVI/PS system was proposed.

Nanoscale zero-valent iron (nZVI) was used as the catalyst to remove amoxicillin (AMX) using a heterogeneous Fenton-like system, where 86.5% of AMX was oxidized using nZVI/H 2 O 2 , while only 25.2% of AMX was removed when nZVI was used. The surface change in nZVI before and after reaction was characterized by various techniques. Scanning electron microscopy (SEM) showed that aggregation and corrosion of nZVI had occurred. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) confirmed the existence of Fe 0 and the presence of iron oxide and iron oxohydroxide Fe(II), Fe(III), as well as UV–visible demonstrated that the absorption peak of AMX had disappeared after the reaction. To understand the degradation mechanism, LC–MS analysis of the degraded products shows that the LC–MS spectra found a new peak at m/z 301 (C 8 H 14 O 9 NS), and the mechanism for Fenton oxidation of AMX was proposed. Removal efficiency depended on the nZVI dosage, initial pH, initial H 2 O 2 concentration and the temperature, where 86.5% of AMX was degraded and 71.2% of COD was removed after 25 min at conditions of H 2 O 2 6.6 mM, nZVI 500 mg/L, AMX 50 mg/L, pH 3.0 and temperature 30 °C. Kinetics for the oxidation of AMX fitted well to the pseudo first-order model and the rate constant k obs increased as temperature increased with an apparent activation energy of 30.1 kJ/mol. Finally, nZVI demonstrated its capacity as a catalyst for heterogeneous Fenton oxidation of AMX from wastewater, and the removal percentage was 80.5%.

Iron nanoparticles (Fe NPs) are often synthesized using sodium borohydride with aggregation, which is a high cost process and environmentally toxic. To address these issues, Fe NPs were synthesized using green methods based on tea extracts, including green, oolong and black teas. The best method for degrading malachite green (MG) was Fe NPs synthesized by green tea extracts because it contains a high concentration of caffeine/polyphenols which act as both reducing and capping agents in the synthesis of Fe NPs. These characteristics were confirmed by a scanning electron microscope (SEM), UV-visible (UV-vis) and specific surface area (BET). To understand the formation of Fe NPs using various tea extracts, the synthesized Fe NPs were characterized by SEM, X-ray energy-dispersive spectrometer (EDS), and X-ray diffraction (XRD). What emerged were different sizes and concentrations of Fe NPs being synthesized by tea extracts, leading to various degradations of MG. Furthermore, kinetics for the degradation of MG using these Fe NPs fitted well to the pseudo first-order reaction kinetics model with more than 20 kJ/mol activation energy, suggesting a chemically diffusion-controlled reaction. The degradation mechanism using these Fe NPs included adsorption of MG to Fe NPs, oxidation of iron, and cleaving the bond that was connected to the benzene ring. Refereed/Peer-reviewed

The degradation of naphthalene using immobilized Bacillus fusiformis (BFN) strain on alginate–polyvinylalcohol (PVA)–clays bead was much higher than that of using a freely suspended BFN strain. This was due to the beads facilitating bio degradation by enhancing concentration of naphthalene using the beads as an adsorbent in the cells’ vicinity. This was confirmed by the kinetics of naphthalene on the beads, where its adsorption onto the beads was confirmed by pseudo-second-order kinetics. The biodegradation of naphthalene fitted wellto the first-order rate model. More than 99.7% of naphthalene which was removed within 12 h, contained bentonite 2% (w/v), PVA12% (w/v), alginate 0.3% (w/v) and 10% (v/v)initial bio massloading. Scanning electron microscopy (SEM) of the beads showed that B. fusiformis was evenly distributed within them. Storage stability and reusability results revealed that the ability to degrade naphthalene using beads with immobilized cells remained stable after storage at 4 ◦C for 35 days and being reused 8 times (12 days), respectively. Furthermore the naphthalene degradation rate of immobilized cells was maintained (94.3%) at the eighth cycle Refereed/Peer-reviewed

This study concerns the removal of Pb(II) and Cr(III) using magnetite nanoparticles synthesized by coprecipitation methods with (NCM) or without (CM) nitrogen gas passing through. Removal of Pb(II) significantly decreased from 80.56 to 41.41% when Cr(III) was co-presented, while decrease of Cr(III) was negligible when Pb(II) was present, falling from 42.37 to 38.48%. The characterizations indicated that the removal mechanism occurred through adsorption rather than chemical redox reaction. A co-adsorption mechanism is based on Pb(II) involved surface complexation, while Cr(III) was firstly adsorbed onto magnetite, followed by a partially substitution of Cr(III) for Fe(III) in Cr-Fe3O4 through ion exchanges. Refereed/Peer-reviewed

A new strain isolated from activated sludge and identified as Burkholderia vietnamiensis C09V was used to biodegrade crystal violet (CV) from aqueous solution. To understand the degradation pathways of CV, batch experiments showed that the degradation using B. vietnamiensis C09V significantly depended on conditions such as pH, initial dye concentration and media components, carbon and nitrogen sources. Acceleration in the biodegradation of CV was observed in presence of metal ions such as Cd and Mn. More than 98.86C of CV (30 mg l−1) was degraded within 42 h at pH 5 and 30 °C. The biodegradation kinetics of CV corresponded to the pseudo first-order rate model with a rate constant of 0.046 h−1. UV–visible and Fourier transform infrared spectroscopy (FTIR) were used to identify degradation metabolites. Which further confirmed by LC-MS analysis, indicating that CV was biodegraded to N,N-dimethylaminophenol and Michler’s ketone prior to these intermediates being further degraded. Finally, the ability of B. vietnamiensis C09V to remove CV in wastewater was demonstrated. Refereed/Peer-reviewed

In this study, bentonite (Bent)-supported nanoscale zero-valent iron (Fe 0 ) (Fe 0 Bent) was prepared to remove acid violet red B from an aqueous solution. Scanning electron microscopy (SEM) images of Fe 0 Bent and batch experiments indicated that the presence of bentonite decreased aggregation of iron nanoparticles and increased their reactivity. After reacting for 9 min, Fe 0 Bent removed 95.6% of acid violet red B with a concentration of 800 mg/l compared to Fe 0 , which removed 75.1%. Iron oxide and hydroxide were the reaction products of the reaction of Fe 0 Bent with acid violet red B. UV–vis spectra showed that the absorption peak of acid violet red B was degraded due to the break of azo linkages. Kinetic studies showed that the degradation rate suited the pseudo-first-order model well. The apparent activation energy was 40.86 kJ/mol, which is typical of a chemically controlled reaction on the smectite surface. The Fe 0 Bent used to remove acid violet red B has the potential to be used for in situ remediation.

In this study, bentonite-supported Fe/Ni (B-Fe/Ni) nanoparticles were used to degrade amoxicillin (AMX) in aqueous solution due to their increased rate of degradation. More than 94% of AMX was removed using B-Fe/Ni, while only 84% was removed by Fe/Ni due to bentonite as the material to reduce the aggregation of Fe/Ni nanoparticles, which was confirmed by scanning electron microscopy (SEM) and X-ray energy-dispersive spectrometer (EDS). X-ray photoelectron spectroscopy (XPS) and FTIR spectral confirmed the presence of Fe (II) and Fe (III) in the B-Fe/Ni after reaction with AMX. Furthermore, the removal of AMX was consistent with pseudo first-order reaction kinetics. The reuse and stability of B-Fe/Ni in degradation of AMX show that it is a potential nanomaterial for the environmental remediation Refereed/Peer-reviewed

Iron-based nanoparticles (OT-FeNP) were synthesized using oolong tea extracts. Their morphology, structure and size were confirmed by scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), UV-visible (UV-vis) and Fourier Transform Infrared spectroscopy (FTIR). Formation of FeNP results in mostly spherical particles with diameters ranging from 40 to 50 nm. Degradation of malachite green (MG) using OT-FeNP demonstrated that kinetics fitted well to the pseudo first-order reaction by removing 75.5% of MG (50 mg/L). This indicated that OT-FeNP has the potential to serve as a green nanomaterial for environmental remediation. Refereed/Peer-reviewed

Iron nanoparticles (Fe NPs) were synthesized using tea extracts as a catalyst for the Fenton-like oxidation of monochlorobenzene (MCB), where 69%, 53%, and 39% of MCB were, respectively, degraded by Fe NPs synthesized using green tea extracts, oolong tea extracts, and black tea extracts. Fe NPs synthesized using green tea extracts (GT-Fe NPs) demonstrated the best degradation since green tea contains a high concentration of caffeine/polyphenols used as both reducing and capping agents in the synthesis of Fe NPs. This was confirmed by SEM image, EDS, and XRD pattern of GT-Fe NPs. In addition, batch experiments show that the oxidation of MCB and the removal of chemical oxygen demand (COD) using GT-Fe NPs were 81% and 31%, respectively, at optimal conditions, where dosages were 0.6 g/L GT-Fe NPs, 0.045 mol/L H2O2, and initial pH of 3.0. Compared to homogeneous Fenton oxidation of MCB, GT-Fe NPs as a heterogeneous catalyst indicate that Fe2+ and Fe3+ leached from GT-Fe NPs nanoparticles and consequently reduced the formation of iron sludge. Finally, GT-Fe NPs were successful in removing MCB from wastewaters, and the possible Fenton-like oxidative mechanism of MCB was proposed. The proposition was based on adsorption of MCB on the surface of GT-Fe NPs, decomposition of H2O2, generation of hydroxyl radicals, and oxidation of MCB. Refereed/Peer-reviewed

In this paper, green tea extract was used to synthesize iron nanoparticles (GT-Fe NPs) and degrade mala-chite green (MG) in aqueous solution. The results show that the damage to morphology and increase insize of GT-Fe NPs after reaction with MG were observed by SEM and EDS. XRD shows that there are fewchanges in the characteristic peaks of GT-Fe NPs before and after reaction. UV–vis spectroscopy showsthat the absorption peak of MG decreased, while FTIR shows that the band at 1585 cm−1correspondedto the phenyl after reaction. The factors impacting on the removal efficiency of MG, including the initialsolution pH, the initial concentration of MG, the dosage of GT-Fe NPs, and the reaction temperature,was also investigated. It emerged that 96% of MG was removed with a 50 mg/L at 298 K. Kinetics studiesshowed that the removal of MG fitted well to the pseudo first-order mode. Refereed/Peer-reviewed

Bentonite supported Fe/Pd nanoparticles (B/nZVI/Pd) were synthesized as composites that exhibit functionalities assisting in the removal of methyl orange (MO) from aqueous solution. The results showed that 91.87% of MO was removed using B/nZVI/Pd, while only 85% and 1.41% of MO were removed using nZVI/Pd and bentonite after 10 min, respectively. The new findings include that the presence of bentonite decreased the aggregation of nZVI/Pd and nZVI in the composite played its role as a reductant, while Pd0acted as the catalyst to enhance the degradation of MO, which were confirmed by scanning electronmicroscopy (SEM), X-ray diffraction (XRD), UV–vis analysis and the batch experiments. The increase in B/nZVI/Pd loading led to greater removal efficiency, while decolorization efficiency declined in the presence of anions such as nitrate, sulfite and carbonate, especially nitrate, which decreased the apparent rate constant kobs almost 17.06-fold. The kinetics study indicated that the degradation of MO fitted well to the pseudo-first-order model, where the kobs was 0.0721 min⁻¹. Finally, the reactivity of aged B/nZVI/Pd was investigated, and the application of B/nZVI/Pd in wastewater indicated a removal efficiency higher than 93.75%. This provided a new environmental pollution management option for dyes-contaminated sites. Refereed/Peer-reviewed

In this study, a newly isolated TNT-degrading bacterium, Bacillus mycoides, was immobilized on a carrier contain- ing 2.5% kaolin, 10% polyvinyl alcohol (PVA), 0.3% sodium alginate (SA) and 10% cell suspension. A batch experiment demonstrated that only 20.6% TNT was removed using gel beads without immobilized cells. In contrast, 92.63% and 71.94% TNT were degraded using the beads with immobilized cells and freely suspended cells, respectively. Kinetic studies showed that adsorption of TNT on the beads followed the pseudo-second order model, while biodegradation of TNT was well fitted to the first-order degrading model where the initial concentrations of TNT ranged from 20 mg/L to 120 mg/L.In this study, a newly isolated TNT-degrading bacterium, Bacillusmycoides,was immobilized on a carrier containing 2.5% kaolin, 10% polyvinyl alcohol (PVA), 0.3% sodium alginate (SA) and 10% cell suspension. A batch experiment demonstrated that only 20.6% TNT was removed using gel beads without immobilized cells. In contrast,92.63% and 71.94% TNT were degraded using the beads with immobilized cells and freely suspended cells, respectively.Kinetic studies showed that adsorption of TNT on the beads followed the pseudo-second order model,while biodegradation of TNT was well fitted to the first-order degrading model where the initial concentrations of TNT ranged from 20 mg/L to 120 mg/L. These new findings suggest that removal of TNT should employ the beads with immobilized cells where adsorption and biodegradation are combined. Immobilized cells were reused 12 times and removed more than 99.5% TNT, and when stored at 4 °C for 42 days, they removed more than 91.3% TNT. This demonstrates that immobilized cells can potentially be applied in a waste water treatment system to remove TNT. Refereed/Peer-reviewed

Organoclays have wide spread application in environmental remediation and nanocomposites synthesis. Some of the quaternary ammonium compounds (QACs) commonly used to prepare organoclays are toxic to biota. However, information on the toxicity of organoclays is rarely available in the literature. This study assessed the toxicity of three laboratory prepared bentonite organoclays on the soil microbially mediated processes (such as dehydrogenase activity and potential nitrification) and soil inhabiting animals, such as earthworms. Toxicity to both microbial processes and earthworm followed the order: hexadecyltrimethyl ammonium modified bentonite > octadecyltrimethyl ammonium modified bentonite > arquad modified bentonite > unmodified bentonite. The organoclays were able to cause slight improvement (up to 25%) in the potential nitrification in some soils when they were added at low application rates up to 5%, but caused reduction (3-86%) in the dehydrogenase activity in all the soils irrespective of loading rates. The organoclays were extremely toxic to the survival and vigour of the earthworms. The average body weight loss of the worms reached as high as 62% in hexadecyltrimethyl ammonium modified bentonite treated soil even at 1% loading. This study holds utmost importance in assessing the toxicity of organoclays to soil microbially mediated processes and earthworms. Refereed/Peer-reviewed

The Bacillus fusiformis (BFN) strain and its biodegradation of phenol when iron-based nanoparticles such as nanoscale zero-valent iron (nZVI) and Ni/Fe nanoparticles (Ni/Fe) were present at different pH values (6.0, 8.0, and 3.0) were investigated. The growth of BFN and its biodegradation of phenol accelerated in the presence of nZVI and Ni/Fe both at pH 8.0 and pH 6.0. The H2 generated by the corrosion of iron can be used as an electron donor and source of energy for growing BFN. However, only nZVI improved the bio-degradation of phenol at pH 3.0, which is most likely due to the increasing medium pH value resulting from the generation of OH- as a result of iron corrosion. The images from scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) demonstrated that these iron-based nanoparticles adhered to the surface of BFN, but no significant change in the morphology of BFN was observed. Refereed/Peer-reviewed

While it is possible to dechlorinate p-chlorophenol (p-CP) into phenol using iron-based nanoparticles, phenol is still a toxic contaminant. This study examines the complete degradation of p-CP using a combination of dechlorinating p-CP with bentonite-supported Fe/Pd nanoparticles (B/Fe/Pd), and the subsequent oxidation of phenol into non-toxic compounds via the Bacillus fusiformis (BFN) strain. Batch experiments showed that 98.7% of p-CP was dechlorinated and 92.3% of phenol was formed using 5 g/L of B/Fe/Pd in 120 min. With regard to biodegradation, the Bacillus fusiformis (BFN) strain grew well in the presence of B/Fe/Pd up to 2 g/L in medium. A high concentration of B/Fe/Pd added to the cell resulted in inhibited cell growth and SEM indicated that Fe/Pd nanoparticles adhered to cell membranes. However, 94.7% of phenol was removed using BFN in 12 h at pH 6.7, 30°C and 0.2% of inoculum concentration in the presence of 2 g/L B/Fe/Pd. Furthermore, biodegradation kinetics fitted well to the pseudo first-order model. Finally, the method proposed here demonstrated the possibility of removing p-CP from wastewaters. Refereed/Peer-reviewed

In this study, lead (Pb) bioaccessibility was assessed in peri-urban contaminated soils using a variety of established in vitro assays. Bioaccessibility data was then used to predict Pb relative bioavailability (RBA) using published in vivo-in vitro regression models in order to compare calculated estimates and measured values. Lead bioaccessibility varied depending on the in vitro methodology employed with the relative bioavailability leaching procedure (RBALP) and in vitro gastrointestinal (IVG) assays providing more conservative Pb bioaccessibility values compared to those determined using PBET, UBM and Rel-SBRC-I assays. When Pb RBA was calculated, predicted values using PBET-G and UBM-G data were similar to measured Pb RBA values. However, Pb RBA was over-estimated by 1.6-5.5- and 2.6-6.6-fold when data and regression models from RBALP and IVG-G assays were employed. Refereed/Peer-reviewed

Kaolinite-supported nanoscale zero-valent iron (K-nZVI) was successfully synthesized as a multifunctional composite and used for the degradation of crystal violet (CV). The presence of kaolinite not only decreased the aggregation of zero-valent iron nanoparticles (nZVI) with maintenance of reactivity, but also facilitated reaction by increasing the local concentration of CV in the vicinity of nZVI as an adsorbent. This was confirmed by scanning electron microscopy (SEM) and batch experiments, which showed that 97.23% of CV was removed using K-nZVI, while only 78.72% and 39.22% of CV were removed using nZVI and kaolinite after 30 min, respectively. Different factors impacting on degradation of CV were investigated as well. On the basis of these results, a removal mechanism was proposed including: (i) prompt adsorption of CV to the K-nZVI phase, and (ii) reduction of CV by Fe(0) on K-nZVI. Furthermore, different adsorption and reduction kinetics were employed to examine the removal process of CV, where a better fit with the pseudo-second-order model for adsorption and pseudo-first-order model for reduction process was observed, and reduction was the rate limiting step. In addition, isotherm and thermodynamic parameters were evaluated for a specific study of the important adsorption step. Finally, the application of K-nZVI to treat wastewater showed the removal efficiency higher than 99.9%.

The surface electrochemical properties of red mud (bauxite residue) from different alumina refineries in Australia and China were studied by electrophoresis and measuring surface charge density obtained from acid/base potentiometric titrations. The electrophoretic properties were measured from zeta potentials obtained in the presence of 0.01 and 0.001 M KNO3 over a wide pH range (3.5–10) by titration. The isoelectric point (IEP) values were found to vary from 6.35 to 8.70 for the red mud samples. Further investigation into the surface charge density of one sample (RRM) by acid/base potentiometric titration showed similar results for pHPZC with pHIEP obtained from electrokinetic measurements. The pHIEP determined from zeta potential measurements can be used as a characteristic property of red mud. The minerals contained in red mud contributed to the different values of pHIEP of samples obtained from different refineries. Different relationships of pHIEP with Al/Fe and Al/Si ratios (molar basis) were also found for different red mud samples. Refereed/Peer-reviewed

Arsenic speciation and cycling in the natural environment are highly impacted via biological processes. Since arsenic is ubiquitous in the environment, microorganisms have developed resistance mechanisms and detoxification pathways to overcome the arsenic toxicity. This study has evaluated the toxicity, transformation and accumulation of arsenic in a soil microalga Scenedesmus sp. The alga showed high tolerance to arsenite. The 72-h 50 % growth inhibitory concentrations (IC50 values) of the alga exposed to arsenite and arsenate in low-phosphate growth medium were 196.5 and 20.6 mg L−1, respectively. When treated with up to 7.5 mg L−1 arsenite, Scenedesmus sp. oxidised all arsenite to arsenate in solution. However, only 50 % of the total arsenic remained in the solution while the rest was accumulated in the cells. Thus, this alga has accumulated arsenic as much as 606 and 761 μg g−1 dry weight when exposed to 750 μg L−1 arsenite and arsenate, respectively, for 8 days. To our knowledge, this is the first report of biotransformation of arsenic by a soil alga. The ability of this alga to oxidise arsenite and accumulate arsenic could be used in bioremediation of arsenic from contaminated water and soil. Refereed/Peer-reviewed

The co-occurrence of polyaromatic hydrocarbons (PAHs) with heavy metals and their effect on soil microbial activity have not been systematically investigated. In this study a holistic approach was employed by combining physico-chemical, biological and advanced molecular methods to determine the soil microbial activities of long-term mixed contaminated soils collected from a former manufactured gas plant (MGP) site. Concentrations of PAHs in MGP soils ranged from 335 to 8645 mg/kg. Of the potentially toxic metals, concentrations of lead were found to be highest, ranging from 88 to 671 mg/kg, cadmium 8 to 112 mg/kg, while zinc varied from 64 to 488 mg/kg. The enzyme activities were severely inhibited in soils that were contaminated with both PAHs and heavy metals. The presence of heavy metals in PAH-contaminated soils not only reduced the diversity of microbial population but also showed a few distinctive species by exerting selective pressure. The multivariate analysis revealed that there is an association between PAHs and heavy metals which influenced biological properties in mixed contaminated soils. The findings of this study have major implications for the bioremediation of organic pollutants in metal-organic mixed contaminated sites. Refereed/Peer-reviewed

Cadmium (Cd) is an environmental pollutant that can be readily taken up by plants and may enter the food chain, causing risk to human health. It can also affect soil quality and, if easily leached, has the potential to pollute surface and ground waters. Sorption and desorption are critical processes controlling the phytoavailability and mobility of Cd in soils. The authors present the present knowledge on the mechanisms and hysteresis of Cd sorption and desorption in soils and factors such as pH, ionic strength, index cation, other heavy metal cations, inorganic anions, organic ligands, Cd loading rate, and the type and amounts of organic matter and inorganic colloids influencing these processes. The methods used to determine the nature and magnitude of Cd sorption and desorption are also critically reviewed. © 2012 Taylor & Francis Group, LLC.

Modified palygorskite is a clay mineral with highly promising potential for remediation of specific organic and inorganic pollutants. In this study we report on some of its special adsorption characteristics as a basis for the design of more effective remediation materials. The surface charge properties of organo-palygorskites prepared from dioctadecyl dimethylammonium bromide (DODMA) were studied by measuring the zeta potential values (ζ) at variable pH conditions. The effect of pH, ζ and temperature on the kinetics of p-nitrophenol adsorption on organo-palygorskite clay minerals was also investigated using a flow-through reactor system. There was a consistent decrease in ζ values with increasing pH resulting in a decrease in the amount of p-nitrophenol adsorbed. The amount adsorbed was high at high initial adsorbate concentration at 23 °C. However, at higher temperature the amount of adsorbed p-nitrophenol reduced significantly. The adsorption data was best fitted to the pseudo-second order kinetic model and was controlled by a complex mechanism of physio-sorption and chemisorption. Desorption of adsorbed p-nitrophenol from the adsorbents was negligible, demonstrating that the adsorption was largely specific in nature. This study has significant implications for developing adsorptive remediation materials for ionisable organic pollutants in waste waters. Refereed/Peer-reviewed

Microbial metabolites are of huge biotechnological potential and their production can be coupled with detoxification of environmental pollutants and wastewater treatment mediated by the versatile microorganisms. The consortia of cyanobacteria/microalgae and bacteria can be efficient in detoxification of organic and inorganic pollutants, and removal of nutrients from wastewaters, compared to the individual microorganisms. Cyanobacterial/algal photosynthesis provides oxygen, a key electron acceptor to the pollutant-degrading heterotrophic bacteria. In turn, bacteria support photoautotrophic growth of the partners by providing carbon dioxide and other stimulatory means. Competition for resources and cooperation for pollutant abatement between these two guilds of microorganisms will determine the success of consortium engineering while harnessing the biotechnological potential of the partners. Relative to the introduction of gene(s) in a single organism wherein the genes depend on the regulatory- and metabolic network for proper expression, microbial consortium engineering is easier and achievable. The currently available biotechnological tools such as metabolic profiling and functional genomics can aid in the consortium engineering. The present review examines the current status of research on the consortia, and emphasizes the construction of consortia with desired partners to serve a dual mission of pollutant removal and commercial production of microbial metabolites. Refereed/Peer-reviewed

To increase the dispersion of nanoparticles and enhance their reactivity, bentonite-supported Fe/Pd nanoparticles (B/Fe/Pd) were synthesized and used for the dechlorination of P-chlorophenol (p-CP) from aqueous solution. The B/Fe/Pd was characterized with a scanning electron microscope (SEM), X-ray energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), and specific surface area (BET). The results showed that the presence of bentonite led to a decrease in aggregation of Fe/Pd nanoparticles and enhanced their reactivity. More specifically, B/Fe/Pd indicated the highest p-CP dechlorination of 100%, while only 25.0% and 15.0% were obtained using B/Fe and bentonite (the conditions: C.sub.0 =5.0mg/L and dose: 10.0g/L), respectively. In addition, kinetic studies show that the dechlorination rate of p-CP was described by pseudo first-order reaction kinetics, and the dechlorination rate increased with rising temperature and Pd loading. The apparent activation energy for dechlorination p-CP using B/Fe/Pd was 40.1kJ/mol, which is characteristic of a chemically surface-controlled reaction. Finally, a potential mechanism for degradation of p-CP is proposed, which is based on Fe acting as the reducing agent, while Pd acts as a catalyst with hydrogen generated from water and bentonite as a support. Refereed/Peer-reviewed

Despite its pivotal role in determining the risks and time frames associated with contaminant release, metal speciation remains a poorly understood aspect of biosolids chemistry. The work reported here used synchrotron-based spectroscopy techniques to investigate the speciation of copper and zinc in a range of Australian biosolids. High resolution element mapping of biosolids samples using micro X-ray fluorescence spectroscopy revealed considerable heterogeneity in key element associations, and a combination of both organic and inorganic copper and zinc binding environments. Linear combination fitting of K-edge X-ray absorption spectra indicated consistent differences in metal speciation between freshly produced and stockpiled biosolids. While sulfide minerals play a dominant role in metal binding in freshly dewatered biosolids, they are of lesser importance in dried biosolids that have been stockpiled. A degree of metal binding with iron oxide minerals was apparent but the results did not support the hypothesis that biosolids metals are chiefly associated with iron minerals. This work has potential implications for the long-term stability of metals in biosolids and their eventual fate following land application. Refereed/Peer-reviewed

In this study, a rapid, sensitive, and fully automated on-line solid phase extraction (SPE)-liquid chromatography (LC)-mass spectrometry (MS) method for the analysis of explosive residues in water, was systematically investigated. First, separation of explosive residues was achieved by reverse-phase chromatography using an XDB-C18 column in 30 min with an eluent containing 0.1% acetic acid, 5 mM ammonium acetate, and methanol. Secondly, atmospheric pressures chemical ionization (APCI) and electrospray ionization (ESI) interfaced with the MS detector were used to examine the explosive residues, indicating that APCI-MS was more suitable than ESI-MS for the detection of explosives. Thirdly, the conditions for on-line SPE, including solvent pH and sample injected volume, were optimized. The calibration curves obtained for all explosives studied were linear in the concentration range 0.5-50 μg L -1. The detection limits of this method ranged from 0.05 to 0.5 μg L-1 when 4000 μL of sample was on-line pre-concentrated on C18 enrichment column. The recoveries from lake waters spiked with explosive standard solution ranged from 90.5 to 108.0%. The proposed method is simple, fast, and could be applied successfully to the analysis of explosive residues in contaminated water without any further pretreatment. Refereed/Peer-reviewed

Organopalygorskites were synthesised by using dimethyldioctadecylammonium bromide (DMDOA) and cetylpyridinium chloride (CP) with surfactant loadings equivalent to 100% and 200% CEC of the palygorskite. The four organopalygorskites, thus produced, were characterised by Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and zeta potential measurement. FTIR and TGA data demonstrated that higher surfactant loadings as well as long branched chain DMDOA produced highly ordered surfactant conformation. SEM morphological results showed that the organopalygorskites had less entangled fibres than the unmodified palygorskite. The zeta potential values showed positive charge formation on the organopalygorskites surface when they were synthesised with surfactant loadings equivalent to 200% CEC of the palygorskite. The organopalygorskites were tested for adsorption of p-nitrophenol (PNP) with a special focus on the adsorption isotherms. The adsorption data could be fitted with multiple isothermal models indicating that the adsorption was controlled by multiple mechanisms. Sorbent loading rate, initial pH, temperature and ionic strength might all affect the adsorption process. Also, DMDOA modified organopalygorskites reduced desorption/redispersal of adsorbed PNP back into the environment to a great extent. This study will be helpful in designing palygorskite-based organoclay adsorbents for remediating organic environmental contaminants which are ionic in nature. Refereed/Peer-reviewed

It is increasingly recognized that metal bioavailability is a better indicator of the potential for phytoremediation than the total metal concentration in soils; therefore, an understanding of the influence of phytoremediation plants on metal dynamics at the soil-root interface is increasingly vital for the successful implementation of this remediation technique. In this study, we investigated the heavy metal and soil solution chemical changes at field moisture, after growth of either Indian mustard ( Brassica juncea ) or sunflower ( Helianthus annuus L.), in long-term contaminated soils and the subsequent metal uptake by the selected plants. In addition, the fractions of free metal ions in soil solution were determined using the Donnan membrane technique. After plant growth soil solution pH increased by 0.2–1.4 units and dissolved organic carbon (DOC) increased by 1–99 mg L −1 in all soils examined. Soluble Cd and Zn decreased after Indian mustard growth in all soils examined, and this was attributed to increases in soil solution pH (by 0.9 units) after plant growth. Concentrations of soluble Cu and Pb decreased in acidic soils but increased in alkaline soils. This discrepancy was likely due to a competitive effect between plant-induced pH and DOC changes on the magnitude of metal solubility. The fractions of free Cd and Zn ranged from 7.2% to 32% and 6.4% to 73%, respectively, and they generally decreased as pH and DOC increased after plant growth. Metal uptake by plants was dependant on the soil solution metal concentration, which was governed by changes in pH and DOC induced by plant exudates, rather than on the total metal concentrations. Although plant uptake also varied with metal and soil types, overall soluble metal concentrations in the rhizosphere were mainly influenced by root-induced changes in pH and DOC which subsequently affected the metal uptake by plants.

A comprehensive review is presented addressing recent trends in the speciation and determination of selenium in biological sample matrices, including important analytical aspects such as sample clean up, pre-concentration, method development, and removal of instrumental interferences. A brief outline of analytical principles, together with an overview of the recent developments and applications of selenium speciation determination is included. The newer methods for detecting selenium, including preparation schemes are also discussed together with speciation methodology based on ion chromatography hyphenated with inductively coupled plasma mass spectrometric techniques. Refereed/Peer-reviewed

We examined arsenic (As) uptake by vegetable crops (amaranth, Amaranthus gangeticus, and silverbeet, Beta vulgaris) as affected by As speciation (AsIII and AsV) and their concentrations in nutrient solution. Amaranth and silverbeet were grown in a nutrient solution containing four levels of arsenate (AsV): 0, 1, 5, and 25 mg As/l and three levels of arsenite (AsIII): 0, 5, 10 mg As/l. Both AsV and AsIII are phytotoxic to these crops with the latter being five times more toxic. Amaranth treated with AsIII exhibited As toxicity symptoms within 48 h of exposure and was close to death within 1 week. However, AsV treatment did not show clear toxicity symptoms other than wilting and yield reduction at the highest dose rate of 25 mg AsV/l. The main mechanism used by vegetable crops to tolerate AsV is probably avoidance—limiting As transport to shoots and increasing As accumulation in the root system. When AsV was added to the nutrient solution, the uptake of As in shoots increased and, at the highest dose (25 mg AsV/l), 60 μg As/g DW (3.6 mg/kg FW) accumulated in the edible portion, which exceeds the WHO recommended limit for food stuffs (2 mg/kg FW) as the water contents of the crops were 94%. It is therefore important to determine the nature of the As species and their bio-accessibility. Iron treatment with 0.5 mg NaFe(III)EDTA/l dose decreased silverbeet As uptake by 45% given its affinity to bind As at the root surface or root rhizosphere and so restrict As translocation to the shoots.

IntroductionIncidences of arsenic (As) poisoning in the Indiansubcontinent—where thousands of people areaffected by arsenicosis, and millions are potentiallyat risk—have led to renewed interest in the problemof As throughout the world. Consequently manyfunding bodies have provided significant support tolocal and international research teams to assess theextent of the problem and the strategies that areneeded to minimise the poisoning of people. This hasled to the publication of several articles that give aholistic overview of the dynamics of As in the soiland water environment. There has also been signif-icant interest in the human health risk associated withthe presence of As in the soil and water. Conse-quently, researchers have been focussing on theexposure pathways associated with As in groundwa-ter. Unfortunately, papers published on the status ofAs in the soil and water environments and exposurepathways have almost always used a limited numberof soil, crop and groundwater samples—often thesample size hardly exceeds 20. Despite this, reputablejournals have continued to publish papers that haveled to generalisation of the associated risks based onlimited sampling. For this reason, we have focussedour research on sample sizes greater than 100.This special issue, entitled ‘‘Arsenic in the Envi-ronment—Risks and Management Strategies’’,comprises a wide range of contributions with anaim to present a multi-disciplinary coverage ofthemes related to the problem of natural As contam-ination in the environment. These themes include: (1)an overview of the extent of As contamination insoutheast Asian perspective; (2) hydrogeochemicalconstraints of As in groundwater and monitoring withexamples from Bangladesh; (3) chemistry and bio-availability of inorganic As in soils; (4) extraction ofAs species from soils and plants; (5) arsenic speci-ation and uptake mechanisms of As by plants and (6)assessment of chronic As exposure, associated humanhealth and ecological risks.The articles included in this special supplementaddress many of these issues and pave the waythrough recent findings on the environmental behav-iour of As in soil and groundwater systems, in terms

Chronic exposure to arsenic (As) causes significant human health effects, including various cancers and skin disorders. Naturally elevated concentrations of As have been detected in the groundwater of Bangladesh. Dietary intake and drinking water are the major routes of As exposure for humans. The objectives of this study were to measure As concentrations in rice grain collected from households in As-affected villages of Bangladesh where groundwater is used for agricultural irrigation and to estimate the daily intake of As consumed by the villagers from rice. The median and mean total As contents in 214 rice grain samples were 131 and 143 microg/kg, respectively, with a range of 2-557 microg/kg (dry weight, dw). Arsenic concentrations in control rice samples imported from Pakistan and India and on sale in Australian supermarkets were significantly lower (p0.001) than in rice from contaminated areas. Daily dietary intake of As from rice was 56.4 microg for adults (males and females) while the total daily intake of As from rice and from drinking water was 888.4 and 706.4 microg for adult males and adult females, respectively. From our study, it appears that the villagers are consuming a significant amount of As from rice and drinking water. The results suggest that the communities in the villages studied are potentially at risk of suffering from arsenic-related diseases.

A comparative study of arsenic enrichment in the Bengal Delta (BD) was carried out in three alluvial aquifers in south-central Bangladesh. Investigated sites included Sonargaon in Narayanganj, Chandina in Comilla and Sirajdikhan in Munshiganj districts. At all sites samples from different depths were collected, and water chemistry and redox status vs. depth trends were determined. The concentrations of DOC and HCO3 − were highest at Sirajdikhan site, while at the Sonargaon and Chandina sites the concentrations were lower. On the contrary, the NH4 + concentration was high at the Chandina site as compared to the other sites. There was a good match between dissolved As and Fe at the Sirajdikhan and Sonargaon sites, but not at the Chandina site. The dissolved aqueous concentration of Mn was low at the Chandina site, which suggested that the Mn(IV) redox buffering step was missing. Speciation modeling indicated a possibility of siderite precipitation at all sites, but precipitation of rhodochrosite only at the Sonargaon and Sirajdikhan sites. At the Sirajdikhan site, the log $$ {\text{P}}_{{{\text{CO}}_{ 2} }} $$ values were very high (−1.37), which revealed the production of CO2 in redox processes. Principal component analysis (PCA) indicated an impact of sea water and redox status of different samples. These results suggest that the dissolved As is de-coupled from dissolved Mn because when released, As is re-adsorbed onto the Fe(III) minerals in solid phase, as well as from dissolved Fe when precipitation of Fe(II) minerals controls the aqueous concentrations of Fe. In addition, several other concurrent redox processes may exert kinetic constraints depending on refractory characteristics of Fe(III) minerals.

We have developed a novel microwave-assisted extraction method for determining the arsenic (As) speciation in soils that is based on extraction with phosphate solutions, including orthophosphoric acid, ammonium dihydrogen orthophosphate, and ammonium hydrogen orthophosphate. The highest extracting efficiency was obtained with 1 M ortho-phosphoric acid solution as the extractant, and this efficiency is associated with the pH of the extractant. Total As content and As species in the soil extracts were determined by inductively coupled plasma mass spectrometry (ICP-MS) alone and by the combined ion chromatography (IC) with ICP-MS, respectively. The proposed extraction procedure was applied to National Institute of Standards and Technology (NIST) standard reference material (SRM) 2711 (Montana soil) as well as to environmental soil samples collected from the agricultural lands of Bangladesh. As(V) was detected in all the soil samples, and As(III) was detected in nine soils of the 20. These results of extractable As testing indicate that the extraction of As species mainly depends on the composition of the soils. The As speciation results also indicate that As adsorption is highly dependent on the iron, aluminum, and manganese concentrations in the soil. The stability of As species in the extracts was also studied.

This report describes the extraction of selenium species contained in pharmaceutical tablets using either enzymatic hydrolysis or sodium dodecyl sulphate extraction (SDS). The selenium species were determined by ion chromatography coupled to inductively coupled plasma mass spectrometry. In the enzymatic extraction approach, proteolytic enzymes (protease/lipase) were used in a buffer containing 75 mM Tris-HCl at pH 7.5. It was found that the extraction efficiency was significantly improved relative to the use of the SDS approach. For example, the extraction recovery was more than 80% of total Se, where selenocystine Se-methyl-selenocysteine (SeMC) and selenomethionine (SeMet) in the samples were extracted. In contrast, chemical extraction of Se using SDS gave only 60% of total Se, while only two species, SeMC and SeMet, were found. In addition, SeMC was found to be unstable and degraded through oxidation in the extraction solution. Finally, the two enzyme methods were applied to commercial pharmaceutical tablets. Refereed/Peer-reviewed

Anion-exchange chromatography (Hamilton, PRP-X100) with inductively coupled plasma mass spectrometry (ICP-MS) is commonly used for the speciation of arsenic in environmental and biological samples. However, retentions for As species are frequently different because of the use of widely different mobile phases. In addition, chloride in matrices interferes with arsenic determination. In this study, we systematically investigated various mobile phases based on ammonium salts affecting arsenic retention to eliminate chloride interference chromatographically. Hence, various mobile phases based on ammonium salts, including NH4H2PO4, NH4HPO4, NH4Ac, NH4HCO3 and NH4NO3, were examined for reasonable resolution and to separate chloride from arsenic species. The best result was obtained with a mobile phase containing 30 mM NH4H2PO4 at pH 5.6, where the separation of arsenic species, including arsenite [As(III)], arsenate [As(V)], dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA)], was achieved within 9 minutes with reasonable resolution and free of chloride interference at its high level (500 mg L− 1). The detection limits for the arsenic species were in the range of 0.1–0.3 μg L− 1 with a direct injection of sample without removing matrix. Finally, the proposed method was used for the determination of arsenic species in contaminated soil and plant tissues.

Inductively coupled plasma mass spectrometry (ICP-MS) and electrospray ionization mass spectrometry (ESI-MS) were used as complementary techniques to provide element and molecular information for aminocarboxylic lead species including [Pb(NTA)]1−, [Pb(HEDTA)]1−, [Pb(EDTA)]2− and [Pb(DTPA)]3−. ESI-MS was used to initially confirm the formation of lead aminocarboxylic complexes in solution and subsequently anion-change chromatography coupled with ICP-MS was used to speciate these complexes using a mobile phase containing 30 mM NH4H2PO4 at pH of 8.0. However, [Pb(NTA)]1− was not observed during chromatographic separation due to its poor stability. The species [Pb(HEDTA)]1−, [Pb(EDTA)]2− and [Pb(DTPA)]3− were separated within 15 min with reasonable resolution and detection limits ranging from 0.05 to 0.2 μg L−1 with simple direct injection of sample. The proposed method was used to speciate aminocarboxylic lead complexes in soil solution.

Arsenic (As) bioaccessibility in contaminated soils (n=50) was assessed using the simplified bioaccessibility extraction test (SBET). Soils used in the study were collected from sites where As was used as an herbicide (railway corridor) or pesticide (cattle dip sites), from former gold mines and from highly mineralised locations containing geogenic As sources (gossans). In all but three soils, As bioaccessibility was less than 50% indicating that a significant proportion of the total As concentration may not be available for absorption in the gastrointestinal tract following incidental soil ingestion. When regression models were developed based on soil properties, the descriptive variables best able to describe As bioaccessibility in railway corridor, dip site and mine site soils were total As and total or dithionite-citrate extractable (free) iron (Fe). While As bioaccessibility could be predicted (r(2)=0.955, n=50) in these contaminated soils, As bioaccessibility for gossan soils was a poor fit using linear or multivariate regression analysis.

The use of capillary electrophoresis (CE) and UV detection for the determination of metal speciation is based on the standards via matching migration time. Consequently, it requires that the metal species are stable during electrophoresis. Migration time of the metal species is dependent on the electrolyte composition. However, the stability for such metal complexes is also dependent on electrolyte composition and electrolyte-specific stability is not always well known. In this paper, the stability of iron (Fe) polycarboxylate complex formation was determined using electrospray ionization mass spectrometry (ESI-MS). Mass spectra indicates that Fe[DTPA] 2− , Fe[EDTA] − , Fe[HEDTA] and Fe[NTA] were present in solution but the mass spectrum for Fe[NTA] was found to be weak. An electrolyte containing 25 mM NaH 2 PO 4 and 0.25 mM tetradecyltrimethylammonium bromide (TTAB) at pH 6.0 was used to successfully separate Fe[DTPA] 2− , Fe[EDTA] 1− and Fe[HEDTA]. The instability of Fe[NTA] meant it was not observed due to its instability during electrophoresis. To improve UV detection limits sample stacking techniques, such as large volume sample stacking (LVSS) without polarity switching and filed-amplified sample injection (FASI), were investigated. The results show that less than 0.01 μM detection limits for the Fe complexes were obtained using FASI. The calibration plots were linear from 0.05–3.0 with good reproducibility (peak area: 6.5–8.1%) when a water plug was used. Finally, the proposed method was demonstrated for the determination of trace Fe complexes in river waters.

Ion chromatography (IC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) was systematically investigated for determining the speciation of chromium in environmental samples. Firstly, the stability of complexes formed by Cr(III) with various aminopolycarboxylic acids was studied by electrospray ionization mass spectrometry (ESI-MS). The results showed that [Cr(EDTA)](-) was stable in solution. Secondly, various mobile phases were examined to separate Cl(-) from chromium species by IC to avoid Cl(-) interference. The separation of [Cr(EDTA)](-) and Cr(VI) was achieved on a new anion-exchange column (G3154A/102) using a mobile phase containing 20mM NH(4)NO(3) and 10mM NH(4)H(2)PO(4) at pH 7.0 without Cl(-) interference. Detection limits for chromium species were below 0.2 microg/L with a direct injection of sample and without prior removal of interferences from the matrix. Finally, the proposed method was used for the determination of chromium species in contaminated waters.

To investigate the effect of nanoscale zero-valent iron (nZVI) on the growth of Paracoccus sp. strain and biodenitrification under aerobic conditions, specific factors were studied, pH, concentration of nitrate, Fe (II) and carbon dioxide. Low concentration of nZVI (50mg/L) promoted both cell growth and biodegradation of nitrate which rose from 69.91% to 76.16%, while nitrate removal fell to 67.10% in the presence of high nZVI concentration (1000mg/L). This may be attributed to the ions produced in nZVI corrosion being used as an electron source for the biodegradation of nitrate. However, the excess uptake of Fe (II) causes oxidative damage to the cells. To confirm this, nitrate was completely removed after 20h when 100mg/L Fe (II) was added to the solution, which is much faster than the control (86.05%, without adding Fe (II)). However, nitrate removal reached only 45.64% after 20h, with low cell density (OD600=0.62) in the presence of 300mg/L Fe (II). Characterization techniques indicated that nZVI adhered to microorganism cell membranes. These findings confirmed that nZVI could affect the activity of the strain and consequently change the biodenitrification. Refereed/Peer-reviewed

A method has been developed for determination of bromate and bromide in water containing high concentrations of chloride (e.g. seawater). Separation of bromate and bromide on an anion-exchange column was followed by ICP–MS detection. To reduce interference of chloride with determination of bromate and bromide, and to avoid clogging, ammonium salts, for example NH4H2PO4, (NH4)2HPO4, (NH4)2CO3, and NH4NO3 were examined as mobile-phase components. It was found that mobile phase containing 20 mM NH4NO3 at pH 5.80 was compatible with the anion-exchange column and enabled reasonable resolution and separation of bromate and bromide within 7 min. Detection limits for bromate and bromide ranged from 2.0 to 3.0 μg L−1 for direct injection of 50 μL sample without matrix elimination. The proposed method was used for analysis of bromate and bromide in seawater.

It is generally considered that cadmium bioavailability shows a considerable dependence on chemical speciation of Cd in solution, correlates best with the activity of free metal ion (Cd2+) in solution, and is largely indifferent to soluble metal complexes. The role of soluble organic matter (DOM) and soluble metal-organic complexes in metal bioavailability and toxicity, however, is not clear. Growth studies with a soil alga (Chlorococcum sp.) were conducted on a growth medium and pore water of Cookes Plain soil (Paleuxeralf), spiked with Cd as Cd(NO3)2. Speciation of the Cd in pore water, and in growth medium with and without citrate, was performed using the MINTEQA2 computer model incorporating updated values of the stability constants of Cd-DOM complexes, as well as using anode stripping voltammetry. Analysis of the toxicity data showed that Cd-citrate, as well as the Cd-DOM complexes, is bioavailable and contributes toward the toxicity to alga. These data contradict the long-held notion that Cd-DOM complexes are not bioavailable to soil biota although they may increase the mobility of Cd.

DDT [1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane] is a major environmental pollutant and economical methods to remove DDT from the environment are required. In this work we used seaweed (dried and ground) to enhance DDT transformation in waterlogged soils. Initial daily rates of DDT biodegradation increased in the following order relating to the percentage by weight of added seaweed to soil 0.5 > 1 > 0 > 3 > 5 > 13 (w/w). The actual percentages of DDT biodegradation occurring within 6 weeks were 80, 64, 60, 50, 40 and 34 respectively. During soil incubation DDD [1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane] was the major metabolite found with small amounts of DDE [1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane] produced. The maximum amount of 4,4′-dichlorobenzophenone (DBP) (2.5%) produced was found in soil amended with 0.5% (w/w) seaweed, indicating that further degradation of DDD occurred. High levels of dissolved organic carbon (DOC), between 309 and 509 mg kg−1 soil, were present in soil amended with 3–13% (w/w) seaweed immediately after seaweed addition. It is possible that the high levels of DOC in soils amended with larger amounts of seaweed significantly retarded DDT biodegradation, possibly due to binding of DDT to DOC and subsequently decreasing the bioavailability of DDT to soil microbes. Copyright © 2004 Society of Chemical Industry

This study was conducted to assess whether the addition of exogenous nutrients and bioaugmentation by arsenic (As) methylating fungi could accelerate the rate of As volatilisation in cattle dip soils containing mixed As and DDT contamination. Increasing levels of manure application resulted in a greater loss of As from contaminated soils [30% (w/w) > 15% (w/w) > 5% (w/w) manure]. Loss of As was more pronounced at 75% of field capacity than at 35% of field capacity. The supplement of 30% (w/w) manure at 75% field capacity exerted the greatest reduction of As (8.3% loss of total As) in a contaminated dip soil containing 1390 mg As kg −1 and 194 mg DDT kg −1 over a 5-month incubation. The rates of As loss and microbial respiration (CO 2 production) were correlated with the levels of manure amendment ( P ≤0.05). Augmentation by As methylating fungi ( Penicillium sp. and Ulocladium sp.) was able to enhance arsine evolution rates in field contaminated soils and in freshly spiked soils. The amounts of arsine dissipated in augmented long-term contaminated soils and soils spiked with As alone were 3.7 and 8.3 orders of magnitude greater than uninoculated soils, respectively. DDT appears to inhibit the rates of microbial formation of arsine in the contaminated dip soils.

1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (p,p′-DDT) is a recalcitrant organic compound that is difficult to remove from contaminated soil due to its low solubility. In this study we investigated the effectiveness of both cosolvents and surfactants in enhancing the solubility of p,p′-DDT from a soil that has been contaminated with DDT for nearly 40 yr. The presence of selected surfactants removed less than 1 to 11% of p,p′-DDT compared to cosolvents, which removed less than 1 to 77% of p,p′-DDT from the same soil. The low solubility of p,p′-DDT in the presence of surfactants was attributed to the decreased surfactant concentration to below critical micelle concentrationfollowing sorption by soil surfaces. Enhanced solubility of p,p′-DDT was achieved with the use of cosolvents that releasedup to 77% of p,p′-DDT from a contaminated soil. Increasing the solution concentration and hydrophobicity of the cosolvent increased the amount of p,p′-DDT desorbed. For example, the amount of p,p′-DDT desorbed increased in the order 5% 1-propanol << 50% ethanol << 50% 1-propanol. Repeated washing of the soil with various cosolvents, in all but two cases, markedly increased the total amount of p,p′-DDT desorbed from the soil. For example, repeated washing of the soil with 50% ethanol increased the amount of p,p′-DDT removed by 42% while repeated washings of the soil with 50% 1-propanol had little effect on the amount of p,p′-DDT desorbed. Increasing the soil-solution ratio from 1:2 to 1:10 in the presence of 40% 1-propanol increased the amount of p,p′-DDT desorbed by 100%; suggesting that the soil-solution ratio was an important parameterin controlling the amount of p,p′-DDT desorbed.

On-column complexation of Fe2+ and Fe3+ with 2,6-pyridinedicarboxylic acid (2,6-PDCA) formed anionic complexes, which were then separated by capillary zone electrophoresis with direct UV detection at 214 nm. To achieve reasonable separation selectivity and on-column complexation, the conditions such as pH, the concentration of 2,6-PCDA and the EOF modifiers in the electrolyte were examined. The electrolyte contained 5.0 mM 2,6-PDCA, 0.25 mM tetradecyltrimethlammonium bromide (TTAB) and 5% (v/v) acetonitrile at pH 4.0 was optimised for on-column complexation and the separation of Fe[PCDA]2(2-) and Fe[PCDA]2(-). To enhance the detection sensitivity, large-volume sample stacking (LVSS) was used for the on-line preconcentration of Fe[PCDA]2(2-) and Fe[PCDA]2(-). Under the optimised conditions, satisfactory working ranges (0.5-50 microM), lower detection limits (less than 0.1 microM) and good repeatability of the peak areas (R.S.D.: 5.2-7.8%, n = 5) was achieved using LVSS (300 s). With LVSS, the detection sensitivity was enhanced more than 50-fold compared to conventional hydrodynamic injection. The proposed method was used successfully for the determination of Fe2+ and Fe3+ in water samples.