The problem of air pollution is a frequently recurring situation and its management has social and economic considerable effects. Given the interaction of the numerous factors involved in the raising of the atmospheric pollution rates, it should be considered that the relation between the intensity of emission produced by the polluting source and the resulting pollution is not immediate. The aim of this study was to realise and to compare two support decision system (neural networks and multivariate regression model) that, correlating the air quality data with the meteorological information, are able to predict the critical pollution events. The development of a back-propagation neural network is presented to predict the daily PM₁₀ concentration 1, 2 and 3 days early. The measurements obtained by the territorial monitoring stations are one of the primary data sources; the forecasting of the major weather parameters available on the website and the forecasting of the Saharan dust obtained by the “Centro Nacional de Supercomputaciòn” website, satellite images and back trajectories analysis are used for the weather input data. The results obtained with the neural network were compared with those obtained by a multivariate linear regression model for 1 and 2 days forecasting. The relative root mean square error for both methods shows that the artificial neural networks (ANN) gives more accurate results than the multivariate linear regression model mostly for 1 day forecasting; moreover, the regression model used, in spite of ANN, failed when it had to fit spiked high values of PM₁₀ concentration.

Nanoparticles derived from natural materials are promising compounds in the field of environmental remediation. The present study produces and characterizes Na-zeolitic tuff in the nanorange, stabilizes the nanotuff in suspension, and investigates the effect of Na-zeolitic nanotuff on sorption of Cd. Breakdown of raw zeolitic tuff with a mean particle size of 109 μm to the nanorange was achieved by attrition milling. In the first stage of grinding, a mixture of Al-oxide beads of 1 to 2.6 mm diameter was used. The milling process lasted 4 h. In the second stage, the dried powder was milled again using a mixture of a fine zirconia beads (0.1 mm) and Al-oxide beads (1.0 mm). The powder was treated with 1 M NaCl solution. Finally, the powder was sonicated in water. After this procedure, the mean and median particle diameters were 47.6 and 41.8 nm, respectively. The nanoparticulate zeolitic tuff had a surface area of 82 m² g⁻¹. The estimated zero charge point of the nanoparticle suspension was 3.2. The surface zeta potential was pH dependent. The Na-zeolitic nanotuff increased Cd sorption by a factor of up to 3 compared to the raw zeolitic tuff. Our results indicate that zeolitic nanoparticles can be produced by grinding using a mixture of fine beads in an attrition mill and that this procedure increases their metal immobilizing potential.

Quantitative structural activity relationship (QSAR) models are receiving wide use because of new regulations and public scrutiny regarding new compounds entered into commerce. Accordingly, the US Department of Defense (DoD) supported this study to evaluate QSAR modeling for energetic compounds. Four compounds proposed to replace ammonium perchlorate were examined: ammonium di(nitramido)amine (ADNA); 1,3,5,5-tetranitrohexahydropyrimidine (DNNC); 1,3,3,5,7,7-hexanitro-1,5-diazacyclooctane (HCO); and diammonium di(nitramido)dinitroethylene (ADNDNE). Currently used compounds were evaluated as analogues for those under development. Ammonium dinitramide (ADN) was the analogue for ADNA; hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) for DNNC; octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) for HCO; and 1,1-diamino-2,2-dinitroethene (FOX-7) for ADNDNE. QSAR analysis was performed with the US Environmental Protection Agency's Estimation Program Interface (EPI) Suite[trade mark sign]. The comparison of model estimates to literature values ranged from good-to-poor. Results suggested the proposed replacement compounds have low aquatic toxicities and little potential to bioaccummulate, but the uncertainty in the predictions indicates QSAR modeling with EPI Suite[trade mark sign] is only useful for qualitative assessments of these proposed energetic compounds.

Organic waste, as a main constituent of municipal solid waste, has as well as solid biomass a high potential for biogas generation. Despite the importance of biogas generation from these materials, the availability of large-scale biogas processes lacks behind the demand. A newly developed double-stage solid-liquid biogas process, consisting of an open hydrolysis stage and a fixed-bed methane reactor, allows the biogas production from almost all biodegradable solid waste and renewable resources like maize, grass, sugar cane, etc. Furthermore, residues from industrial processes, like the glycerine waste water from biodiesel production, can also be converted into biogas successfully. Due to the strong separation of hydrolysis and methanation, the process is extremely stable. No malfunction has been detected so far. The open hydrolysis releases CO₂ and allows oxidation of sulfur. Consequently, the biogas has a high methane (>72%) and low H₂S concentration (<100 ppm). Stirrers or other agitation equipment are not necessary; only liquids are pumped. The biogas generation becomes controllable for the first time; thus, the actual generation can be easily adapted to the consumption.

Air quality in the Mexican cities of Monterrey, Nuevo Leon, and Mexicali, Baja California, has suffered great detriment in recent years. It is well known that meteorology is one of the main factors affecting the dynamics of pollutants in the atmosphere. Here, the Penn State/NCAR Meteorological Mesoscale Model (MM5) meteorological system was applied to identify meteorological conditions conducive to high-ozone concentrations in such regions. Two summer 2001 ozone episodes for each geographical domain were selected with the aid of a classification and regression tree analysis technique. Model response to changes in its physical parameterization, horizontal grid resolution, and data assimilation schemes were assessed. Once a suitable configuration was selected, performance statistics were computed for model validation. MM5 simulated satisfactorily the meteorology of such episodes, yielding indexes of agreement of 0.4-0.8 for wind speed and 0.67-0.95 for temperature, on average. However, MM5 tended to underestimated temperature and overestimated wind speed. Froude numbers were calculated to analyze the impact of the terrain complexity on wind circulation. It was concluded that in both cities, wind convergence zones might enhance high-ozone concentrations. These results improve our understanding of the atmospheric processes exerting effect on air pollution within these airsheds.

Nonpoint source pollution is the leading remaining cause of water quality problems. The extent of NPS pollution is often more difficult or expensive to monitor at the point(s) of origin, as compared to monitoring of point sources. This study evaluated the hypothesis that animal manure (chicken, cow, horse, and pig) applied to pasture contribute fecal sterols and bile acids to runoff. The study also assessed the potential benefit of fecal sterols and bile acids as biomarkers in distinguishing fecal pollution and its sources. Fecal sterol and bile acid concentrations were determined in flow-weighted composite runoff samples collected from 2.4 x 6.1 m plots (n = 3) amended with manure. Runoff was generated from simulated rainfall (152 mm.h⁻¹). Runoff samples from manure-amended plots showed high concentrations of fecal sterol (ranged from 13 ± 1 to 1,287 ± 183) and bile acid (ranged from 24 ± 1 to 2,251 ± 248) biomarkers. The profiles of fecal sterols and bile acids in runoff samples were similar to those of fresh manure for all selected animals. For runoff and fresh manure, chenodeoxycholic acid, deoxycholic acid, epicoprostanol, and hyodeoxycholic acid were consistent biomarkers for chicken, cow, horse, and pig, respectively, suggesting that sterols and bile acids can be used to identify sources and occurrence of fecal matter in water and sediments.

The presence of polylcyclic aromatic hydrocarbons (PAHs) in surface sediments of Barigui River was investigated. PAHs are considered highly toxic and persistent compounds because of their structure. They originate from incomplete combustion of fossil fuels or biomass. The Barigui River crosses the metropolitan region of Curitiba, and some regions are highly polluted and located near the possible sources of pollution. The results showed that concentrations of total PAHs ranged from 44.6 to 880.2 ng g⁻¹, and the highest values were found at the sites previously investigated and identified as critically polluted. At sites located away from the traffic and possible pollution sources, the total PAHs was lower, 44.6 ng g⁻¹. Due to their hydrophobic character, sediments with high silt and clay content retain greater amounts of PAHs. The granulometric composition of the sediments revealed that most of them are composed basically by silt and clay, and those samples showed high concentration of PAHs. The organic carbon content also confirms this observation. The other sites investigated showed a high capacity to adsorb hydrophobic compounds mainly due to the granulometric composition and organic matter that adsorb poorly water soluble compounds. Finally, we found that the main sources of PAHs are petrogenic; however, at some sites, it is hard to confirm this pattern, and possibly, a mixture of the source would be more appropriate.

Naphthenic acids (NAs) are a complex group of naturally occurring oil sands constituents that constitute a significant portion of the dissolved organic carbon (DOC) pool available for microbial degradation in the process-related waste water associated with oil sands mine sites. One approach to understanding the biological fate of oil sands process-derived carbon and nitrogen in aquatic reclamation of the mine sites involves the use of stable isotope analyses. However, for stable isotope analyses to be useful in such field-based assessments, there is a need to determine how microbial degradation of a complex mixture of NAs might change the stable isotope values (δ ¹³C, δ ¹⁵N). In batch cultures and semi-continuous laboratory microcosms, utilization of a commercial mixture of NAs by oil sands-derived microbial cultures resulted in microbial biomass that was similar or slightly ¹³C enriched (1.4[per thousand] to 3.0[per thousand]) relative to the DOC source, depending on the length of incubation. Utilization of a NA-containing extract of oil sands processed water resulted in greater ¹³C enrichment of microbial biomass (8.5[per thousand]) relative to the DOC source. Overall, the δ ¹³C of the DOC comprised of complex mixtures of NAs showed minimal change (-0.5[per thousand] to -0.1[per thousand]) during the incubation period whereas the δ ¹³C of the dissolved inorganic carbon (DIC) was more variable (-5.0[per thousand] to +5.4[per thousand]). In tests where the concentration of available nitrogen was increased, the final biomass values were ¹⁵N enriched (3.8[per thousand] to 8.4[per thousand]) relative to the initial biomass. The isotope trends established in this study should enhance our ability to interpret field-based data from sites with hydrocarbon contamination, particularly in terms of carbon source utilization and ¹⁵N enrichment.

Natural lignite from South Moravia was tested for the sorption of fluoride anion in concentration range from 5·10⁻⁵ to 8·10⁻⁴ mol/l. The lignite removes majority of fluorides and only about 13% of sorption is reversible upon leaching in pure water. Sorption data can be fitted by both Freundlich and Langmuir equations and both isotherms indicate presence of two principal sorption sites or steps. The sorption is fast, at least 90% of final sorbed amount is removed during the first 10 min but kinetic data show a complex pattern with temporary increase of fluoride concentration. This is attributed to complexity of lignite-water interactions, lignite soaking and swelling in aqueous media. Foreign ions and pH showed only slight influence on the sorbed amount. Natural lignite can be considered as a potential low-cost defluoridation agent that is effective at various solution chemistries and also at low, but still over-limit, fluoride concentrations.

This paper examines the historical change in the pH of natural rainwater due to increased atmospheric CO₂ from 1800 until 2007, giving predicted change in 2100. During 1800-2007, the rainwater pH at 25°C and 1 atm is calculated to decrease by 0.06 units, from 5.68 to 5.62. In 2100, the predicted rainwater pH is calculated at 5.49 using the projected pCO₂ (700 ppmv; IS92a) at 25°C and 1 atm. Equilibrium calculations were made in an attempt to elucidate the calcium carbonate (calcite) dissolution by rainwater. From 1800 to 2007, the dissolution of calcite with pCO₂ of those time at 25°C and 1 atm increase the dissolved calcium concentration from 466 to 516 μmol kg⁻¹. This value is calculated to reach 633 μmol kg⁻¹ in the year 2100. Rainwater is found to become more acidic with decreasing temperature. In the year 2007 (pCO₂ = 384 ppmv), a total difference of 0.08 units in rainwater pH is calculated between areas at 0°C and 30°C. The equilibrium pH with respect to calcite was found to increase with decreasing temperature. At lower temperatures, rainwater pH is found to decrease, whilst CaCO₃ dissolution increases. Limestone landmarks and buildings might be affected through the dissolution of calcium carbonate by rainwater acidification. The effects of rainwater acidification on overall chemical weathering may result in influences on agriculture, forestry, landslides and flooding.