Selenium (Se) contamination of aquatic habitats is a global environmental issue. Although organic forms of Se are thought to represent the most bioavailable forms of Se, elevated concentrations of inorganic Se can cause toxicity in aquatic organisms such as benthic invertebrates. To assess the potential role of Se in mortalities observed during previous in situ invertebrate exposures, laboratory experiments on toxicity of inorganic Se (selenate) to Hyalella azteca were performed. Both a laboratory-reared and a field-collected H. azteca population were exposed to Se concentrations ranging from near 0 (control) to 21.79 mg/L, and survival of exposed individuals was monitored over 10 days. In the laboratory-reared H. azteca, significant changes in mortality pattern and reductions in mean survival time (MST) were noted in the test groups exposed to ≥0.164 mg/L Se. In the field-collected animals however, significant changes in mortality pattern and reductions in MST were measured in H. azteca exposed to ≥1.43 mg/L Se. The 10-day LC50s were 0.086 and 0.574 mg Se/L for the laboratory and field-collected H. azteca populations, respectively. The laboratory-reared group thus was about one order of magnitude more sensitive to Se exposure than the field-collected amphipods. Our results suggest that Se toxicity was likely not a major contributor to amphipod mortalities observed in earlier field studies. Furthermore, population-specific tolerances of the test organisms may need to be considered when extrapolating laboratory-generated data to field situations.

Nanoparticles (NPs) are emerging as a new type of contaminant in water and wastewater. The fate of titanium dioxide nanoparticles (TiO₂NPs) in a granular activated carbon (GAC) adsorber and their impact on the removal of trichloroethylene (TCE) was investigated. Key parameters governing the TiO₂NP–GAC interaction such as specific surface area (SSA), zeta potential, and the TiO₂NP particle size distribution (PSD) were determined. The impact of TiO₂NPs on TCE adsorption on GAC was tested by conducting TCE adsorption isotherm, kinetic, and column breakthrough studies in the presence and absence of TiO₂NPs. SSA and pore size distribution of the virgin and spent GAC were obtained. The fate and transport of the TiO₂NPs in the GAC fixed bed and their impact on TCE adsorption were found to be a function of their zeta potential, concentration, PSD, and the nature of their aggregation. The TiO₂NPs under investigation are not stable in water and rapidly form larger aggregates. Due to the fast adsorption kinetics of TCE, the isotherm and kinetic studies found no effect from TiO₂NPs. However, TiO₂NPs attached to GAC and led to a reduction in the amount of TCE adsorbed during the breakthrough experiments suggesting a preloading pore blockage phenomenon. The analysis of the used GAC confirmed the pore blockage and SSA reduction.

The total concentration and size distribution of bioaerosols in three different types of housing (single room in shared accommodation [type I], single bedroom flat in three-storey building [type II] and two- or three-bedroom detached houses [type III]) was assessed during the winter. This research was an extension of a previous study carried out in the summer. The measurement campaign was undertaken in winter 2008 and 30 houses were sampled. Samples were taken from kitchens, living rooms, corridors (only in housing type I) and outdoors with an Anderson 6 stage viable impactor. In housing type I, the total geometric mean concentration was highest in the corridor for both bacteria and fungi (3,171 and 1,281 CFU/m³, respectively). In type II residences, both culturable bacteria and fungi were greatest in the living rooms (3,487 and 833 CFU/m³, respectively). The living rooms in type III residences had largest number of culturable bacteria (1,361 CFU/m³) while fungi were highest in kitchens (280 CFU/m³). The concentrations of culturable bacteria and fungi were greater in mouldy houses than non-mouldy houses. A considerable variation was seen in the size distribution of culturable bacteria in type I residences compared to types II and III. For all housing types more than half of culturable bacterial and fungal aerosol were respirable (<4.7 μm) and so have the potential to penetrate into lower respiratory system. Considerable variation in concentration and size distribution within different housing types in the same geographical region highlights the impact of differences in design, construction, use and management of residential built environment on bioaerosols levels and consequent varied risk of population exposure to airborne biological agents.

Chlorophyll fluorescence spectral analysis permits detection, monitoring, and evaluation of abiotic stresses upon healthy plants using illumination of a light source in the UV–VIS spectral range. This technique indirectly assesses the amount of physiological stress caused by photosynthetic damage, specifically damage to photosystem II, in plants. The objective of this study was to detect the toxicity of cadmium in maize plants via spectral analysis of chlorophyll fluorescence. The analysis is noninvasive and nondestructive and is used to follow the temporal evolution of changes in the chlorophyll content and physiological state of Zea mays L. seedlings under cadmium stress. Conventional techniques were also used to evaluate the dry matter production and Cd accumulation in plant leaves. Plants exhibited a notable reduction in dry matter production and chlorophyll levels with the administration of increasing doses of Cd in the nutrient solution. The fluorescence analysis was sensitive to changes caused by Cd in maize plants, detecting damage caused by different treatments before visual symptoms were observed. This technique has a practical application and produces rapid results that can be used in the evaluation of Cd-induced stress in plants and the detection of areas contaminated by this element.

A directly amine-functionalized mesoporous silica (AMS) was prepared via an anionic surfactant-mediated synthesis method and used as adsorbents for deep removal of Cu ions from aqueous solution at room temperature. The synthesized AMS had been characterized by X-ray diffraction, nitrogen physisorption measurement, and thermogravimetric analysis. The amine groups prefer to position to the surface of AMS material due to the SN ∼ I mechanism. Copper adsorption process had been studied from both kinetic and equilibrium points of view for AMS material. Experiments proved that the aqueous Cu adsorption rates were fast and adsorption capacity was about 53.3 mg/g.

Many of the environmental problems related to agriculture will still be serious over the next 30 years. However, the seriousness of some of those problems may increase more slowly than in the past or even diminish in other cases (FAO 2002). Agriculture plays two different roles in climate change; on one hand, it suffers from the impact of climate change, on the other hand, it is responsible for 14 % of total greenhouse gases (MMA 2008). Nevertheless, agriculture is also part of the solution, as it is capable of mitigating a significant amount of global emissions, according to the FAO (2001). This paper aims to study the influence of edapho-climate conditions on soil CO2 emissions into the atmosphere. In order to do so, we conducted three field trials in different areas in southern Spain, which have different soil textures and different climate conditions. The results show how interaction between the temperature and rainfall recorded has a greater influence on emissions than each of the factors separately. However, at the same time, the texture of the soil at each of the locations was also found to be the most dominant variable in the gas emission process.

Studies concerning competitive sorption of anions on oxidic materials eligible to be used as soil amendments are crucial for a better understanding of the adsorbent’s effectiveness and ion mobility/availability in the environment. This study evaluated mono-/multi-element adsorption of phosphate and arsenate on aluminum (AMB) and iron mining by-products (IMB; used for comparison) and measured the effect of pH and thermal pretreatments on P and As adsorption on AMB and IMB. We also evaluated whether the desorption of As previously adsorbed on AMB and IMB increases with the addition of increasing doses of P. For adsorption, each adsorbent was reacted at selected pHs with solutions containing As and P individually or in combination. Non-competitive desorption was performed with 30 mmol L⁻¹ NaCl. Arsenate displacement was evaluated by reaction of the adsorbents containing previously adsorbed As with P-containing solutions. The competition between P and As decreased the adsorption of these anions by 2.7 and 23.2 %, respectively. Increasing pH decreased adsorption of both As and P, whereas the thermal pretreatment increased P adsorption by 40 % and As adsorption by 15 %. Phosphate in solution increased As desorption, with each millimoles per kilogram of adsorbed P desorbing as much as 2.3 ± 1.1 mmol kg⁻¹ of As.

Leachable chromium in the incineration fly ash and wastewater sludge has been thermally stabilized by plasma melting at the temperature of 1,773 K. To better understand how chromium is stabilized with the high-temperature treatment, chemical structure of the slags sampled at temperature zones of 1,100–1,700 K has been studied by synchrotron X-ray absorption spectroscopy. The component-fitted X-ray absorption near edge structure spectra of chromium indicate that the main chromium compounds in the sludge and fly ash are Cr(OH)₃, Cr₂O₃, and CrCl₃. A small amount of toxic CrO₃ is also observed in the fly ash. In the plasma melting chamber under the reducing environment, the high-oxidation state chromium is not found. The slags in the plasma melting chamber have much less leachable chromium, which is due to chemical interactions between chromium and SiO₂ in the slags. The existence of the interconnected Cr-O-Si species is observed by refined extended X-ray absorption fine structure spectroscopy. In the Cr₂O₃ phase of the slags, their bond distances, and coordination numbers for the first (Cr-O) and second (Cr-(O)-Cr) shells have insignificant perturbation when experienced with different melting temperatures between 1,300 and 1,700 K. It seems that Cr₂O₃ and chromium encapsulated in the silicate matrix of the slags have relatively much lower leachability. With this concept, to obtain a low chromium leachability slag from the plasma melting process, the residence time of the melting chamber may be decreased, and the slag discharge temperatures may be increased to 1,300 K. This work also exemplifies utilization of molecule-scale data obtained from synchrotron X-ray absorption spectroscopy to reveal how chromium is thermally stabilized in a commercial scale plasma melting process.

Plant growth-promoting rhizobacteria (PGPR) play an important role in the biodegradation of natural and xenobiotic organic compounds in soil. They can also alter heavy metal bioavailability and contribute to phytoremediation in the presence or absence of synthetic metal chelating agents. In this study, the inhibitory effect of Cd2+ and Ni2+ at different concentrations of Ca2+ and Mg2+, and the influence of the widely used chelator EDTA on growth of the PGPR Pseudomonas brassicacearum in a mineral salt medium with a mixture of four main plant exudates (glucose, fructose, citrate, succinate) was investigated. Therefore, the bacteriostatic effect of Cd2+, Ni2+ and EDTA on the maximum specific growth rate and the determination of EC50 values was used to quantify inhibitory impact. At high concentrations of Ca2+ (800 μmol L-1) and Mg2+ (1,250 μmol L-1), only a small inhibitory effect of Cd2+ and Ni2+ on growth of P. brassicacearum was observed (EC50 Cd2+, 18,849 ±â€‰80 μmol L−1; EC50 Ni2+, 3,578 ±â€‰1,002 μmol L−1). The inhibition was much greater at low concentrations of Ca2+ (25 μmol L−1) and Mg2+ (100 μmol L−1) (EC50 Cd2+, 85 ±â€‰0.5 μmol L−1 and EC Ni2+, 62 ±â€‰1.8 μmol L−1). For the chosen model system, a competitive effect of the ions Cd2+ and Ca2+ on the one hand and Ni2+ and Mg2+ on the other hand can be deduced. However, the toxicity of both, Cd2+ and Ni2+, could be significantly reduced by addition of EDTA, but if this chelating agent was added in stoichiometric excess to the cations, it also exhibited an inhibitory effect on growth of P. brassicacearum.

Solution pH is among the most important parameters that influence heavy metal biosorption. This work presents a kinetic study of the effects of pH on chromium biosorption onto Cupressus lusitanica Mill bark from aqueous Cr(VI) or Cr(III) solutions and proposes a mechanism of adsorption. At all assayed contact times, the optimum pH for chromium biosorption from the Cr(III) solution was 5.0; in contrast, optimum pH for chromium biosorption from the Cr(VI) solution varied depending on contact time. The kinetic models that satisfactorily described the chromium biosorption processes from the Cr(III) and Cr(VI) solutions were the Elovich and pseudo second-order models, respectively. Diffuse reflectance infrared Fourier transform spectroscopy studies suggest that phenolic compounds present on C. lusitanica Mill bark play an important role in chromium biosorption from the Cr(III) solution. On the other hand, chromium biosorption from the Cr(VI) solution involved carboxyl groups produced on the bark by redox reactions between oxygen-containing groups and Cr(VI), and these were in turn responsible for the biosorption of Cr(III) produced by Cr(VI) reduction.