Dual-effects of adsorption and photodegradation over titania, silica embedded titania, silica and commercial Degussa P-25 samples were studied for the decolourization of methylene blue in aqueous medium. Silica embedded titania and silica were prepared using inexpensive polymeric version of ethyl silicate as a source of silica. Catalysts were characterized by X-ray diffraction, scanning electron microscopy, UV-Vis spectroscopy and low temperature (77 K) nitrogen adsorption measurements. Among all the catalysts, silica embedded titania has exhibited faster decolourization of methylene blue solution on account of the enhancement of adsorption followed by degradation. An amount of the catalyst and the initial dye concentration of MB solution were found to influence the decolourization activity. Compared to titania catalyst, silica embedded titania and Degussa P-25 have shown the red shift in their UV-Vis spectrum. The experimental data of the reaction fitted well to the pseudo first order kinetic model. In present studies, the adsorption mechanism for the decolourization of MB solution was found to be applicable for an intra particle diffusion model. © 2013 Springer Science+Business Media Dordrecht.

Water and sediment samples were collected along river transects at three artisanal gold mining areas in southern Ecuador: Nambija, Portovelo-Zaruma, and Ponce Enriquez. Samples were analyzed for a suite of major and trace elements, including filtered/unfiltered water samples and stream flow measurements to determine dissolved/particulate loads. Results show that the Q. Calixto, Calera, and Siete rivers (corresponding to Nambija, Portovelo-Zaruma, and Ponce Enriquez mining areas, respectively) have substantial trace element contamination due to mining inputs. Dissolved concentrations were elevated at Calera and Siete relative to Q. Calixto, possibly reflecting the input of soluble cyano-metal complexes in mining zones where cyanidation is used in ore processing. A negative correlation was found between MeHg:THg ratios and pH, indicating an inverse relationship of mercury methylation with cyanidation (since cyanidation increases water pH). This was the first comprehensive study to examine an extensive suite of trace elements in both water and sediment at the three main gold mining areas of southern Ecuador, including dissolved and particulate loads, and the first study to report MeHg concentrations in the mercury-contaminated rivers.

Acid mine drainage (AMD) generated by some coal mines in New Zealand is currently treated by the addition of alkaline reagents which neutralize acidity, triggering the precipitation of dissolved metals as insoluble hydroxides. Some trace metals (Ni, Zn, Cu, Cd, and Pb) are discharged into receiving water bodies due to incomplete hydroxide precipitation at circum-neutral pH. This study investigated the incorporation of lignite-derived humic substances (HS) for metal complexation and removal during AMD treatment by Ca(OH)₂ and CaCO₃ neutralization. For Ca(OH)₂ neutralization, addition of HS (regardless of dosing sequence) enhanced the removal of Zn, Cu, and Cd, probably due to the incorporation of metal–humate complex into settling flocs (via aggregation, co-precipitation, and adsorption) that were subsequently removed by sedimentation. However, additional removal of Ni and Pb was statistically indeterminate, which was ascribed to the low complexation affinity of Ni and high removal of Pb by adsorption onto Fe/Al hydroxides. Conversely, for CaCO₃ neutralization, addition of HS only marginally enhanced Cd removal, with the removal of metals probably dominated by adsorption onto the abundant undissolved calcite. Equilibrium speciation modelling showed that about 25% and 38% of the remaining Cu and Pb in the treated AMD were complexed with HS, while only 5% of remaining Cd and less than 1 wt% of remaining Ni and Zn were organically complexed. In the AMD-receiving water bodies, about 20 mg l⁻¹ of HS would be required for complete complexation (>95%) of Cu and Pb and 50 mg l⁻¹ for Cd, whereas Zn and Ni complexation would not occur at natural stream HS concentrations.

The ubiquitous presence of chlorophenols (CPs) continues to be a cause of concern, owing to their recalcitrant nature. In this context, the present work investigated the degradation of model compounds, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol, by an organic oxidant, methyl ethyl ketone peroxide (MEKP) coupled with ultraviolet irradiation in basic media. Chemical analysis was followed by high-performance liquid chromatography and gas chromatography–mass spectrometry. Despite exhibiting varied patterns of decline, chemical oxygen demand was eventually noted to decrease to the extent of up to 70 %. Simultaneous increase/decrease in the release of chloride ions and decrease in pH indicated that parallel reactions were occurring, which led to the formation of acidic reaction products. First-order dynamics was approximated for all CP congener degradation. The degraded compounds showed absolutely no presence of chlorine atoms, which was a noteworthy feature testifying to the fact that MEKP action was capable of detoxification of CP congeners.

The flux of metals at the tidal limits of major rivers are an important metric of freshwater contaminant transfer to marine habitats, reported in Northeast Atlantic bordering countries under the 1992 Oslo-Paris (OSPAR) Convention. This paper presents an assessment of long-term OSPAR data for four trace metals (Cd, Cu, Pb, and Zn) using a range of spatial datasets to assess the broad distribution of metal flux and yield across England and Wales. Mine site records and geological and land use data are used to classify river basins into six classes. The bulk of metal flux to seas around England and Wales occurs from catchments containing extensive mineralization and a legacy of metal mining (52 % of the total Zn flux, 47 % of Pb, 39 % of Cu, and 48 % of Cd were associated with mined catchments). Catchment area, metal flux from point mine discharges at source, and extent of mineralization typically accounted most for variation in catchment outlet metal flux in stepwise multiple linear regression (SMLR). There are a number of small mining-impacted rural catchments contributing significant fluxes of metals to coastal waters. Of particular prominence are Restronguet Creek (drainage area 87 km²) in southwest England that discharges 176 t Zn/year and 18 t Cu/year and the Afon Goch Dulas (27 km²) in north Wales, which releases 20 t Zn/year and 9 t Cu/year. Although such exercises cannot directly determine the provenance of metals, comparison with metal release data and a review of catchment-scale studies suggest a critical role of mining-related contaminants in contributing to catchment metal export.

The aim of the present study was to verify if cocaine, at environmental concentrations, influences the endocrine system of the European eel. Silver eels (a stage of the eel life cycle preparing the fish for the oceanic reproductive migration) were exposed to a nominal cocaine concentration of 20 ng/l during 30 days; at the same time, control, carrier, and postexposure recovery groups were made. The effects of cocaine were observed in (1) brain dopamine content, (2) plasma catecholamine levels (dopamine, norepinephrine, and epinephrine), (3) pituitary–adrenal axis activity [plasma adrenocorticotropic hormone (ACTH), corticosterone, cortisol, and aldosterone levels], and (4) pituitary–thyroid axis activity [plasma thyroid-stimulating hormone (TSH), triiodothyronine, and thyroxine levels]. In the treated group, brain dopamine, plasma catecholamines, cortisol, and TSH levels were higher, whereas ACTH, corticosterone, and triiodothyronine levels were lower than controls. In the postexposure recovery group, brain dopamine, plasma dopamine and epinephrine, and thyroxine levels further increased, whereas plasma norepinephrine, cortisol, and corticosterone levels were similar to treated values. Finally, ACTH and TSH were similar, whereas triiodothyronine levels were lower than controls. Aldosterone levels were unaffected by cocaine exposure. The results of the present study show that cocaine, at environmental concentrations, behaves like an endocrine disruptor changing brain dopamine and plasma catecholamine levels and the activity of pituitary–adrenal/thyroid axes. Since the endocrine system plays a key role in the metabolic and reproductive processes of the eel, our results suggest that environmental cocaine could be considered another cause for the decline in the European eel.

Palm oil mill effluent (POME) is an organic waste material produced at the oil palm mills. In its raw form, POME is highly polluting due to its high content of biological and chemical oxygen demand. In the present paper, POME was treated using double chamber microbial fuel cell with simultaneous generation of electricity. Polyacrylonitrile carbon felt (PACF), a new electrode material was used as electrode throughout the MFC experiments. Various dilutions of raw POME were used to analyze the effect of initial chemical oxygen demand (COD) on MFC power generation, COD removal efficiency and coulombic efficiency. Anaerobic sludge was used as inoculum for all the MFC experiments. Since this inoculum originated from POME, it showed higher potential to generate bioenergy from complex POME. Anaerobic sludge enhanced the power production due to better utilization of substrates by various types of microorganisms present in it. Among the raw POME and different concentrations of POME used, the PACF with raw POME showed the maximum power density and volumetric power density of about 45 mW/m² and 304 mW/m³, respectively, but it showed low coulombic efficiency and low COD removal efficiency of about 0.8 % and 45 %, respectively. The MFC PACF with 1:50 dilution showed higher COD removal efficiency and coulombic efficiency of about 70 % and 24 % but showed low power density and low volumetric power density of about 22 mW/m² and 149 mW/m³, respectively. The formation of biofilm onto the electrode surface has been confirmed from scanning electron microscopy (SEM) experiments. The results confirm that MFC possesses great potential for the simultaneous treatment of POME and power generation using PACF as electrode and also shows that initial COD has great influence on coulombic efficiency, COD removal efficiency and power generation.

Recently, metal nanoparticles have attracted attention as promising peroxygen activators for the rapid and effective remediation of organic contaminants. In this work, a one-dimensional physical model experiment was designed to investigate the mobility of the metal nanoparticles in porous media and the potential use of metal nanoparticles as peroxygen activators for in situ treatment of source zones. We found that our synthesized nano-Pd-Fe0 particles were mobile in a non-geological porous medium and relatively immobile in a geological porous medium. In addition, we observed that iron-based bimetallic nanoparticles were able to remain in suspension in an ideal aqueous system much longer (>6 weeks) than iron-based monometallic nanoparticles (<1 h). To overcome the nano-Pd-Fe0 particle delivery issue in geological porous media, an activation zone approach was adopted. Nano-Pd-Fe0 particles were injected in order to create a zone to activate persulfate for the treatment of a trichloroethylene source zone. Trichloroethylene mass destruction was only 9 % higher in the nano-Pd-Fe 0 activated persulfate system compared to the non-activated persulfate system as revealed by a short-duration chloride concentration spike in the effluent. In addition, the nano-Pd-Fe0 activation zone was rapidly deactivated after being exposed to persulfate as visually observed by a color change, indicating that the longevity of the activation zone is limited. © 2013 Springer Science+Business Media Dordrecht.

Heavy metals occur naturally in soil, at concentrations that depend on the parent material from which the soil was formed, the processes of formation, and the composition and the proportion of the components of its solid phase. Quantifying these concentrations is important for environmental studies of soil contamination and pollution, and choosing the methods for doing so is a key step in establishing heavy metal contents in soil samples. We evaluated two digestion methods (aqua regia and EPA 3051, both microwave oven-assisted) for assessing pseudo-total concentrations of Cd, Co, Cr, Cu, Ni, Pb and Zn in the surface layer (0–20 cm) of soil samples from the Brazilian agricultural frontier in the southwestern Amazon. Nineteen composite samples of the most representative soil classes for the states of Mato Grosso and Rondônia were collected under native vegetation undisturbed by human intervention. Canonical discriminant analysis and principal component analysis were used for multivariate exploration of the data. Aqua regia extracted higher amounts of Co, Ni, Pb, and Zn than EPA 3051, while levels of Cr and Cu did not differ between methods. In general, aqua regia recovered more of the metals when compared to reference soil samples.

We studied the effects of N deposition (0, 10, 20 and 50 kg N ha⁻¹ year⁻¹) on cover and physiology of Pleurochaete squarrosa, a terricolous moss from semiarid Mediterranean ecosystems. We also investigated the effects of N fertilization under competition with vascular plants or under water stress. Under greenhouse conditions, vascular plant competition reduced moss cover, and there was a significant interaction between N and competition. Water stress reduced moss cover under high and low competition conditions. Nitrogen fertilization increased moss cover irrespectively of the N dose supplied at low competition conditions. Under field conditions, N deposition affected moss physiology but not cover. Most of the physiological variables analyzed responded to N deposition, although the response of some of them was saturated with only 10 kg N ha⁻¹ year⁻¹ over the background (nitrate reductase; phosphomonoesterase; tissue N and K⁺). The response of indicators such as chlorophyll a and lutein contents did not show any evidence of saturation, which probably makes them the best candidates in monitoring programs. Based on the data provided, the applicability of the phosphomonoesterase can also be considered. In addition, the importance of taking into account the existence of superimposed environmental gradients (such as those in soil mineral N content) interacting with the response of P. squarrosa to predict impacts of N deposition has been demonstrated. Therefore, detailed soil surveys and integrative physiological evaluations will be required to produce a significantly better picture of the effects of N deposition on Mediterranean ecosystems along extant N deposition gradients.