Single and combined effects of aluminum (Al<Subscript>2</Subscript>O<Subscript>3</Subscript>) and zinc (ZnO) oxide nanoparticles in a freshwater fish, <Emphasis Type="Italic">Carassius auratus</Emphasis>

The increasing use of nanoparticles (NPs) worldwide has raised some concerns about their impact on the environment. The aim of the study was to assess the toxicity of metal oxide nanoparticles, singly or combined, in a freshwater fish (Carassius auratus). The fish were exposed for 7, 14, and 21 days to different concentrations of NPs (10 μg Al₂O₃.L^?1, 10 μg ZnO.L^?1, 10 μg Al₂O₃.L^?1 plus 10 μg ZnO.L^?1, 100 μg Al₂O₃.L^?1, 100 μg ZnO.L^?1, and 100 μg Al₂O₃.L^?1 plus 100 μg ZnO.L^?1). At the end of each exposure period, antioxidant enzyme activity (catalase, glutathione-S-transferase, and superoxide dismutase), lipid peroxidation, and histopathology were assessed in the gills and livers of C. auratus. The results show an increase in catalase (CAT) and superoxide dismutase (SOD) activity in the gills and livers of fish, especially after 14 days of exposure to single and combined NPs, followed by a reduction at 21 days. An increase in glutathione S-transferase (GST) was observed in gills after 7 days for all tested NP concentrations (single and combined); while in livers, a significant increase was determined after 14 days of exposure to 100 μg.L^?1 of both single ZnO and Al₂O₃ NPs. Lipid peroxidation (LPO) significantly increased in gills after 7 days of exposure to 100 μg.L^?1 Al₂O₃ NPs (single or combined). In livers, LPO increased significantly after 7 days of exposure to all tested concentrations of both single ZnO and Al₂O₃ (except for 10 μg Al₂O₃.L^?1), and after 14 days of exposure to ZnO (10 and 100 μg.L^?1) and Al₂O₃ (100 μg.L^?1)_. The results from histological observations suggest that exposure to metal oxide NPs affected both livers and gills, presenting alterations such as gill hyperplasia and liver degeneration. However, the most pronounced effects were found in gills. In general, this study shows that the tested NPs, single or combined, are capable of causing sub-lethal effects on C. auratus, but when combined, NPs seem to be slightly more toxic than when added alone.     

Behavior of nine selected emerging trace organic contaminants in an artificial recharge system supplemented with a reactive barrier

Artificial recharge improves several water quality parameters, but has only minor effects on recalcitrant pollutants. To improve the removal of these pollutants, we added a reactive barrier at the bottom of an infiltration basin. This barrier contained aquifer sand, vegetable compost, and clay and was covered with iron oxide dust. The goal of the compost was to sorb neutral compounds and release dissolved organic carbon. The release of dissolved organic carbon should generate a broad range of redox conditions to promote the transformation of emerging trace organic contaminants (EOCs). Iron oxides and clay increase the range of sorption site types. In the present study, we examined the effectiveness of this barrier by analyzing the fate of nine EOCs. Water quality was monitored before and after constructing the reactive barrier. Installation of the reactive barrier led to nitrate-, iron-, and manganese-reducing conditions in the unsaturated zone below the basin and within the first few meters of the saturated zone. Thus, the behavior of most EOCs changed after installing the reactive barrier. The reactive barrier enhanced the removal of some EOCs, either markedly (sulfamethoxazole, caffeine, benzoylecgonine) or slightly (trimethoprim) and decreased the removal rates of compounds that are easily degradable under aerobic conditions (ibuprofen, paracetamol). The barrier had no remarkable effect on 1H-benzotriazole and tolyltriazole.     

Emissions Variability Processor (EMVAP): Design,evaluation, and application

Emissions of pollutants such as SO₂ and NOx from external combustion sources can vary widely depending on fuel sulfur content, load, and transient conditions such as startup, shutdown, and maintenance/malfunction. While monitoring will automatically reflect variability from both emissions and meteorological influences, dispersion modeling has been typically conducted with a single constant peak emission rate. To respond to the need to account for emissions variability in addressing probabilistic 1-hr ambient air quality standards for SO₂ and NO₂, we have developed a statistical technique, the Emissions Variability Processor (EMVAP), which can account for emissions variability in dispersion modeling through Monte Carlo sampling from a specified frequency distribution of emission rates. Based upon initial AERMOD modeling of from 1 to 5 years of actual meteorological conditions, EMVAP is used as a postprocessor to AERMOD to simulate hundreds or even thousands of years of concentration predictions. This procedure uses emissions varied hourly with a Monte Carlo sampling process that is based upon the user-specified emissions distribution, from which a probabilistic estimate can be obtained of the controlling concentration. EMVAP can also accommodate an advanced Tier 2 NO₂ modeling technique that uses a varying ambient ratio method approach to determine the fraction of total oxides of nitrogen that are in the form of nitrogen dioxide. For the case of the 1-hr National Ambient Air Quality Standards (NAAQS, established for SO₂ and NO₂), a “critical value” can be defined as the highest hourly emission rate that would be simulated to satisfy the standard using air dispersion models assuming constant emissions throughout the simulation. The critical value can be used as the starting point for a procedure like EMVAP that evaluates the impact of emissions variability and uses this information to determine an appropriate value to use for a longer term (e.g., 30-day) average emission rate that would still provide protection for the NAAQS under consideration. This paper reports on the design of EMVAP and its evaluation on several field databases that demonstrate that EMVAP produces a suitably modest overestimation of design concentrations. We also provide an example of an EMVAP application that involves a case in which a new emission limitation needs to be considered for a hypothetical emission unit that has infrequent higher-than-normal SO₂ emissions.

ImplicationsEmissions of pollutants from combustion sources can vary widely depending on fuel sulfur content, load, and transient conditions such as startup and shutdown. While monitoring will automatically reflect this variability on measured concentrations, dispersion modeling is typically conducted with a single peak emission rate assumed to occur continuously. To realistically account for emissions variability in addressing probabilistic 1-hr ambient air quality standards for SO₂ and NO₂, the authors have developed a statistical technique, the Emissions Variability Processor (EMVAP), which can account for emissions variability in dispersion modeling through Monte Carlo sampling from a specified frequency distribution of emission rates.     

Comparative Toxicity of Prymnesium parvum in Inland Waters1

Brooks, Bryan W., Susan V. James, Theodore W. Valenti, Jr., Fabiola Urena-Boeck, Carlos Serrano, Jason P. Berninger, Leslie Schwierzke, Laura D. Mydlarz, James P. Grover, and Daniel L. Roelke, 2010. Comparative Toxicity of Prymnesium parvum in Inland Waters. Journal of the American Water Resources Association (JAWRA) 46(1):45-62. DOI: 10.1111/j.1752-1688.2009.00390.x Abstract: Numerous studies have examined the impacts of Prymnesium parvum to aquatic life, but the majority of information available is from experiments or field studies performed at salinities of marine and coastal ecosystems. Ambient toxicity of P. parvum has been characterized with in vitro and in vivo models because reliable quantitation of P. parvum toxins in environmental matrices is often precluded by a lack of available analytical standards. Hemolytic activity and fish mortality assays have been used most frequently to characterize toxic conditions; however, relatively few in vivo studies employed standardized methods. Because the relative sensitivities of different taxa to P. parvum toxins in inland waters were undefined, we assessed the comparative toxicity of P. parvum filtrate from a laboratory study (20°C, 12:12 light:dark cycle, f/8 media, 2.4 psu) to several common standardized in vitro and in vivo models. After exposure to cell-free filtrate hemolytic activity (1 h EC₅₀ = 13,712 cells/ml) and juvenile fish (Pimephales promelas) survival (48 h LC₅₀ = 21,754 cells/ml) were the most sensitive assay responses examined, followed by rotifer (Brachionus calyciflorus) population growth rate [48 h no observable adverse effect levels (NOAEL) = 19,072 cells/ml] and cladoceran (Daphnia magna) reproduction (10-day NOAEL = 47,680 cells/ml). Green algae (Pseudokirchneriella subcapitata) growth (96 h) was not adversely affected but was instead significantly stimulated by P. parvum toxins. We further propose an initial species sensitivity distribution approach for P. parvum, which may be used to support future environmental management decisions. Our findings from these laboratory studies indicate that although fish kills are increasingly associated with P. parvum blooms occurring in inland waters, further study is required to define the influences of toxin sensitivities of phytoplankton, zooplankton, and fish communities on P. parvum bloom initiation and termination.     

Passive treatment of acid mine drainage with high metal concentrations using dispersed alkaline substrate

Passive treatment systems based on the dissolution of coarse calcite grains are widely used to remediate acid mine drainage (AMD). Unfortunately, they tolerate only low metal concentrations or acidity loads, because they are prone to passivation (loss of reactivity due to coating) and/or clogging (loss of permeability) by precipitates. To overcome these problems, a dispersed alkaline substrate (DAS) composed of a fine-grained alkaline reagent (calcite sand) mixed with a coarse inert matrix (wood chips) was developed. The small grains provide a large reactive surface and dissolve almost completely before the growing layer of precipitates passivates the substrate, whereas the dispersion of nuclei for precipitation on the inert surfaces retards clogging. Chemical and hydraulic performance of DAS was investigated in two laboratory columns fed at different flow rates with natural AMD of pH 2.3 to 3.5 and inflow net acidity 1350 to 2300 mg/L as CaCO(3). The DAS columns removed 900 to 1600 mg/L net acidity, 3 to 4.5 times more than conventional passive treatment systems. Regardless of the flow rate employed, Al, Fe(III), Cu, and Pb were virtually eliminated. Minor Zn, Ni, and Cd were removed at low flow rates. High acidity removal is possible because these metals accumulate intentionally in DAS, and their precipitation promotes further calcite dissolution. During 15 mo, DAS operated without clogging at 120 g acidity/m(2).d, four times the loading rate recommended for conventional passive systems; DAS may therefore be capable of treating AMD at sites where influent chemistry precludes the use of other passive systems.     

Environmental strategy and performance in small firms: a resource-based perspective

In spite of the widespread recognition of the important roles that small and medium sized enterprises (SMEs) play in most economies, limited research has focused on their impacts on the natural environment and the strategies such enterprises adopt to reduce these impacts. It is usually assumed that SMEs lack the resources to implement proactive environmental strategies that go beyond minimum regulatory compliance. In this study of 108 SMEs in the automotive repair sector in Southern Spain, we found that SMEs undertake a range of environmental strategies from reactive regulatory compliance to proactive pollution prevention and environmental leadership. These strategies are associated with three organizational capabilities: shared vision, stakeholder management, and strategic proactivity, hypothesized based on the unique strategic characteristics of SMEs--shorter lines of communication and closer interaction within the SMEs, the presence of a founder's vision, flexibility in managing external relationships, and an entrepreneurial orientation. We also found that firms with the most proactive practices exhibited a significantly positive financial performance.     

A method for measuring the anoxic biodegradability under denitrifying conditions

A test for assessing the anoxic biodegradability of organic compounds under denitrifying conditions is proposed. The method is based on the recovery and quantification of the CO2 produced, which is evidence of complete biodegradation of the test compound (added as the sole carbon source). The tests were carried out in a mineral medium, with nitrate as electron acceptor. Whole lake sediments, sediment extracts and a commercial inoculum were assayed as a possible inoculum source by means of glucose biodegradability tests. It was found that the sediment extracts constitute a suitable and environmentally-relevant inoculum source, since they add non-significant amounts of carbon to the tests. Two xenobiotic compounds, namely, aniline and phenol, were tested in the aforementioned conditions as well as in a standard aerobic biodegradability test. Both aniline and phenol attained a biodegradation level higher than 60% in a short time period (<28 days) and thus can be considered as readily biodegradable in denitrifying environments. Nevertheless, the kinetics obtained in the anoxic test were slower than in aerobic conditions, and even suggested the accumulation of intermediate metabolites in the case of phenol. The results of this study indicate that the fate of xenobiotic compounds under anoxic conditions differs from that observed in an oxic environment, and therefore it should be considered by standard biodegradability testing procedures.     

Natural organic matter quantification in the waters of a semiarid freshwater wetland (Tablas de Daimiel, Spain)

Dissolved organic matter (DOM) concentrations have been measured in the waters of a semiarid freshwater wetland, the Tablas de Daimiel, Spain, when the system-characterised by variable hydroperiodicity conditions, was completely flooded (February 2011). Fluxes of DOM from the wetland soils to the overlying waters were measured by using a passive diffusion sampler (peeper). Not only dissolved organic carbon (DOC) concentrations were measured but refractory organic matter (ROM, usually known as humic substances) was also quantified using a novel voltammetric method. Fluorescence spectra were recorded to help in selecting the appropriate standard for ROM quantification, test the homogeneity of DOM in the waters and get an indication of their source. The results obtained show a 7-fold increase in measured ROM concentrations from the Gigu¨ela River to the outlet, which points to a net exportation of ROM from the wetland and to the existence of an internal source of ROM in the system, probably diffusion from the wetland soils. This hypothesis is confirmed by the flux of ROM from the soils to the water column measured with the peeper and by the common fluorescence characteristics of column and interstitial waters. The smaller increase in DOC concentrations along the wetland, in spite of the higher DOC fluxes from soils, suggests that there is significant turnover of organic carbon (OC) in the water column. The system acts as a major carbon sink but, when flooded, exports OC as DOM.     

An inhibitor of urease activity effectively reduces ammonia emissions from soil treated with urea under Mediterranean conditions

Urea is an important source of ammonia (NH₃) emissions to the atmosphere from agricultural soils. Abatement strategies are necessary in order to achieve NH₃ emission targets by reducing those emissions. In this context, a field experiment was carried out on a sunflower crop in spring 2006 with the aim of evaluating the effect of the N-(n-butyl) thiophosphoric triamide (NBPT) in the mitigation of volatilized NH₃ from a urea-fertilised soil. Ammonia emission was quantified, using the integrated horizontal flux (IHF) method, following application of urea with and without the urease inhibitor NBPT. Urea and a mixture of urea and NBPT (0.14%, w/w) were surface-applied at a rate of 170 kg N ha⁻¹ to circular plots (diameter 40 m). The soil was irrigated with 10 mm of water just after the application of urea to dissolve and incorporate it into the upper layer of soil. Over the duration of the measurement period (36 days) three peaks of NH₃ were observed. The first peak was associated with hydrolysis of urea after irrigation and the others with the increase of ammonia in soil solution after changes in atmospheric variables such as wind speed and rainfall. The total NH₃ emission during the whole experiment was 17.3 ± 0.5 kg NH₃–N ha⁻¹ in the case of urea treated soils and 10.0 ± 2.2 kg NH₃–N ha⁻¹ where NBPT was included with the urea (10.1 and 5.9%, respectively, of the applied urea–N). The lower NH₃ emissions from plots fertilised with urea + NBPT, compared with urea alone, were associated with a reduction in urease activity during the first 9 days after inhibitor application. This reduction in enzymatic activity promoted a decrease in the exchangeable NH₄⁺ pool.     

Use of multicriteria decision aid methods in the context of sustainable innovations: bibliometrics,applications and trends

Environment Systems and Decisions - Sustainable innovation has gained prominence in recent years, due to the demands imposed by global competition, social pressures and the needs of consumers and...