The study of atmospheric concentration levels at a local scale is one of the most important topics in environmental sciences. Multivariate analysis, fuzzy logic, and neural networks have been introduced in forecasting procedures in order to elaborate operational techniques for level characterization of specific atmospheric pollutants at different spatial and temporal scales. Particularly, approaches based on artificial neural networks (ANNs) have been proposed and successfully applied for forecasting concentration levels of PM, NO, SO, CO, and O. The present study explores the development and application of ANN models for forecasting, 24 h ahead, not only the daily concentration levels of PM but also the number of hours exceeding the PM concentration threshold during the day in five different regions within the greater Athens area (GAA). The ANN modeling was based on measurements and estimates of the mean daily PM concentration, the maximum hourly NO concentration, air temperature, relative humidity, wind speed, and the mode daily value of wind direction from five different monitoring stations for the period 2001-2005. The evaluation of the model performance showed the risk of daily PM concentration levels exceeding certain thresholds as well as the duration of the exceedances can be successfully predicted. Despite the limitations of the model, the results indicate that ANNs, when adequately trained, have considerable potential to be used for 1 day ahead PM concentration forecasting and the duration within the GAA.

In this study, chemical oxidation was applied to treat three contaminated sediments. All the sediments were contaminated with mineral oil, polycyclic aromatic hydrocarbons and heavy metals and had an organic matter content ranging from 2.4 to 7.6 %. The natural oxidant demand of the sediments was determined during treatment with two different types of oxidants (potassium permanganate and sodium persulfate), and the effect of these oxidants on the heavy metal release and on the microbial community was investigated. The natural oxidant demands of the sediments under persulfate treatment were lower (30–100 g kg⁻¹) than the ones treated with permanganate (50–450 g kg⁻¹). Cr was released during the application of permanganate whereas Zn and Pb were released under persulfate treatment. qPCR results showed that permanganate and persulfate, both at a concentration of 150 g kg⁻¹, caused a decrease (2 log units) in the number of 16S rRNA gene of total bacteria in the sediment having the lowest organic matter content. However, the total ATP, considered as a biomarker for microbial activity, was below detection limit in all sediments in the presence of at least 150 g kg⁻¹ oxidant. Only permanganate induced a shift in the structure of the microbial community.

The fate and behaviour of tributyltin (TBT) at two wastewater treatment works was examined. Both sites had two inlet streams, and each utilised high rate biological filters (biofilters) on one the streams, before treatment of the combined flows on trickling filters, with one having additional tertiary processes, installed to remove ammonia and solids. The study was designed to determine if these processes enhanced the removal of TBT. Degradation of TBT was observed in one of the biofilters, possibly as a result of temperature and hydraulic loading. At the treatment works with tertiary processes, the mass flux showed the overall removal of TBT was 68 %, predominantly due to removal with solids in the primary settlement processes. However, overall removal of 95 % was observed in the conventional trickling filter works with 94 % of this due to biodegradation in the trickling filter. The two works both removed TBT, but at different treatment stages and by different processes. Differences in the form (solubility) of TBT in the influent may have attributed to this, although further understanding of factors controlling degradation would allow for a more complete assessment of the potential of biological processes to remove hazardous compounds from wastewaters.

In this paper, preliminary investigation was conducted to evaluate the potential ecological risk of heavy metals contamination in cemetery soils. Necrosol samples were collected from within and around the vicinity of the largest mass grave in Rwanda and analyzed for heavy metal concentrations using total digestion–inductively coupled plasma mass spectrometry and instrumental neutron activation analysis. Based on the concentrations of As, Cu, Cr, Pb, and Zn, the overall contamination degree (C dₑg) and potential ecological risks status (RI) of the necrosols were determined. The preliminary results revealed that the associated cemetery soils are only contaminated to a low degree. On the other hand, assessment of the potential ecological risk index (RI) revealed that cumulative heavy metal content of the soil do not pose any significant ecological risks. These findings, therefore, suggest that, while cemetery soils may be toxic due to the accumulation of certain heavy metals, their overall ecological risks may be minimal and insignificant.

The comparative and competitive adsorption of Cr(VI) and Ni(II) in single and binary systems using coconut shell activated carbon (CSAC) was investigated. The CSAC was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM). The effects of pH, initial metal concentration, and temperature on the adsorption of metal ions were studied. Cr(VI) removal was found to be maximum (94.5 %) at pH = 2.0. While, Ni(II) removal was found to be maximum at pH = 9.0 (58.92 %). The adsorption capacity of Cr(VI) was greater than that of Ni(II) in single component system. Parameters of adsorption isotherm model, kinetics, and thermodynamics were calculated. The single ion equilibrium adsorption data were fitted to the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. The Langmuir and Freundlich models represented the equilibrium data better than the D-R model. The result of the fitting of D-R isotherm model indicated a physical adsorption process. The adsorption kinetic data of Cr(VI) and Ni(II) were found fitting well in pseudo second-order equation both in single and binary system (r 2 > 0.99) and intraparticle diffusion was the rate controlling step. The negative ΔG and the positive ΔH indicated the spontaneous and endothermic nature of the adsorption process. The extended Langmuir isotherm model fitted well with the competitive adsorption data of Cr(VI) and Ni(II). For the desorption experiments, EDTA showed the maximum desorption efficiency of 69 % for Cr(VI) and 81 % for Ni(II). © 2013 Springer Science+Business Media Dordrecht.

Removal of petroleum hydrocarbon (PHC) contamination that is hazardous and often prevalent in soils would benefit from a rapid detection technique. Visible and near-infrared spectroscopy (VIS-NIRS) has a large potential as a rapid detection technique for PHC in soils. Nevertheless, the combined influence of oil concentration, moisture content and clay content on soil reflectance spectra and the accuracy of the technique have yet received little attention. The objective of this study was to investigate the combined influence of oil concentration and moisture and clay contents on the spectral characteristics of diesel-contaminated soils and the quality of calibration models developed for polycyclic aromatic hydrocarbons (PAH) in soils using VIS-NIRS. With partial least-squares regression data from a systematic experimental design using 150 artificially contaminated soil samples, results showed that soil diffuse reflectance decreased with increasing oil concentration, clay and moisture contents. The trend was less defined in relation to moisture and clay due mainly to the interaction effects of the soil matrices as mediated by the oil. The PAH partial least squares cross-validation showed best performance with the lowest oil concentration and clay content at 20 % moisture with r ² of 0.89, root mean square error of prediction of 0.201 mg/kg and ratio of the standard error of prediction to the standard deviation of the reference data in the validation set of 2.75. Analysis of variance showed that the interaction effects of oil concentration, moisture and/or clay content significantly (p < 0.05) affected the quality of the PAH models.

Ammonia emission from broiler houses is a major concern because of its impacts on the environment. To reduce ammonia emissions, it is necessary to understand the fate of ammonia/um in the broiler waste. In broiler waste, uric acid and urea hydrolyze to ammonia (NH₃) and a fraction of NH₃ converts to ammonium (NH₄ ⁺) depending on pH and temperature. Further, NH₄ ⁺ undergoes solid–liquid partitioning and the ammonia fraction is partitioned among the solid, liquid, and gas phases in the waste. Ammonium partitioning between solid and liquid phases in broiler cake and litter were measured at pH of 4, 6, and 7. Ammonium adsorption increased with pH in both broiler litter and cake. Adsorption capacity of the litter was much lower than broiler cake. Six NH₄ ⁺ adsorption/desorption isotherms (linear, Langmuir, Freundlich, Temkin, Redlich–Peterson, and Toth) were evaluated. The isotherm that provided the best fit for partitioning NH₄ ⁺ in litter or cake for each pH value was selected by comparing up to six sets of parameters modeled using linear and nonlinear (with five error functions) regressions. Despite high R ² values obtained using linear regression, linearizing the models introduced an offset into the model reducing their accuracy. The sum of normalized error was used to select the most suitable parameter set for each isotherm. While the nonlinear error functions were the more suitable for developing parameter sets in broiler litter, for cake, linear regression generally provided the most optimum parameter sets. Whereas the Freundlich, linear, and Temkin isotherms were the most suitable for broiler litter for pH of 4, 6, and 7, respectively, for the cake, the linear isotherm was the most suitable for the entire range of pH evaluated. Overall, due to its simplicity, the linear isotherm seems suitable for partitioning NH₄ ⁺ in the adsorbed and dissolved phases for simulating nitrogen fate and dynamics in broiler waste more accurately.

The sorption behaviors of brilliant blue FCF dye by natural clay and modified with iron chloride were determined. The materials were characterized by X-ray diffraction and scanning electron microscopy, and the zero point charges were also determined. The effects of pH, contact time, dye concentration, and temperature were considered. The results showed that clay does not suffer any important change in its structure after the chemical treatments. The pH influences the sorption of the dye in the unmodified clay, but this effect was not observed in the iron-modified clay. The equilibrium time and the sorption capacity for the unmodified clay were 48 h and 6.16 mg/g, while for the iron-modified clay, 24 h and 14.22 mg/g, respectively. The sorption kinetics results were best adjusted to the pseudo-first-order and pseudo-second-order models. Sorption isotherms were best adjusted to the Langmuir model, indicating that both clays have a homogeneous surface. Thermodynamic parameters (E, ΔS, ΔG and ΔH) were calculated for the natural clay from the data of the sorption kinetics at temperatures between 20 and 50 °C, indicating that the sorption process is exothermic. For the case of the iron-modified clay, it was not possible to calculate these thermodynamic parameters because the sorption capacities were similar in the temperature range selected.

Spatial and temporal trends in nutrient concentrations and loads were analyzed for three rivers in the Red River watershed, Manitoba, Canada to determine changes in nutrient export across hydrologic seasons and along river continua in the Great Plains. Annual patterns in all three rivers were strongly influenced by the snowmelt period: 25-89 % of the total annual river volume, 42-92 % of the total annual TP load, and 41-81 % of the total annual TN load were delivered during snowmelt. Concentrations of TP and TN varied among the hydrologic seasons (snowmelt, summer, fall, and winter), but showed more variability and larger values during winter and snowmelt, with peak values reaching 1.960 mg TP L-1 and 16.07 mg TN L-1. Although the flat topography and semi-arid climate of the Red River watershed results in hydrological disconnects along river continua, discharge and nutrient export increased along the three river gradients. In contrast, TP or TN concentrations showed no significant longitudinal change for the two agriculturally dominated watersheds yet increased along the forested stream. Our finding that TP and TN exports from northern Great Plains rivers are strongly influenced by seasonal hydrology, with snowmelt being a critical period for nutrient export has implications for design and implementation of appropriate management practices to minimize nutrient export to proximal and downstream aquatic ecosystems. © 2013 Her Majesty the Queen in Right of Canada.

Colistin is a peptide antibiotic widely used as a food additive in animal farming, specially swine and poultry, and also has recently been applied in human medicine to treat infections caused by multiresistant gram-negative bacteria strains. When orally administered, colistin is eliminated in feces virtually unaltered; thus, it may reach water bodies and wastewater treatment facilities in its active form. Apart from the risks associated with development of antimicrobial resistance and environmental toxicity issues, the presence of antimicrobials in wastewater can, additionally, interfere in biological processes commonly used to treat them. Nitrifying bacteria are among the most sensitive microorganisms to inhibitory compounds, including pharmaceuticals, and are useful as biosensors to access contaminant toxicity information in wastewater treatment plants. Therefore, in order to assess the colistin acute toxicity to the microorganisms involved in the nitrification processes, the nitritation and nitratation kinetics were monitored under different colistin concentrations. The results showed that only ammonia-oxidizing bacteria are sensitive to the antibiotic, presenting an IC50 of 10.8 mg L⁻¹ of colistin when used as a commercial formulation and 67.0 mg L⁻¹ when used as raw colistin sulfate. For nitrite-oxidizing bacteria, even the highest colistin concentration used in the assays (316 mg L⁻¹) was not sufficient to inhibit the process. According to these results, the colistin concentrations expected in animal farming wastewater, when its dosage is used as a growth promoter, would not be enough to keep nitrification from taking place. Nevertheless, when used in higher concentrations, such as for therapeutic purposes, it could endanger the maintenance of the process.