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.

The subalpine and alpine areas in North-Western Italy and Southern Switzerland (Canton Ticino) receive high deposition of atmospheric pollutants transported from emission sources in the Po Valley. Long-term studies on high-altitude lakes in these areas indicate widespread recovery from acidification, even though most of them are still substantially affected, especially by deposition of nitrogen compounds. We analysed long-term trends of the major chemical compounds in a sample (n = 41) of high-altitude lakes, both at the site and regional levels, with the aim to assess the response of water chemistry to changes in atmospheric deposition and climate. These lakes have been studied since the early 1980s in the context of research programmes on acidification and atmospheric pollution. The significant decrease of sulfate and acidity in atmospheric deposition led to acidification recovery in the majority of the lakes. However, some lakes are still acidic or show a high sensitivity to acidification. This sensitivity is particularly evident at the snowmelt, when alkalinity is still fully depleted in some lakes. At present, nitrate is the dominant acidifying agent in the studied lakes, due to the high input of nitrogen compounds from atmospheric deposition. Our study also demonstrated that climatic factors interact with atmospheric deposition affecting the long-term changes in lake water.

The adsorption mechanism of Ni(II) and Zn(II) onto activated carbon fiber (ACF) cloth and felt plain and oxidized was investigated in this work. The adsorption equilibrium data were obtained in a batch adsorber. The concentration of acidic and basic sites on the ACFS was determined by an acid-base titration method. The experimental adsorption equilibrium data were interpreted with the Redlich-Peterson isotherm, which fitted the data reasonably well. The ACF was oxidized with HNO3 solution and the concentration of acidic sites increased during oxidation, whereas that of the basic sites diminished. The adsorption capacity of the oxidized ACF was higher than that of the plain ACF because the oxidation of ACF formed more acidic sites on the surface where the metal cations can be adsorbed. The adsorption capacity of the plain and oxidized ACFs was linearly dependent upon the concentration of carboxylic sites. The adsorption of Ni(II) and Zn(II) on the ACFs was due to both electrostatic interactions and cation-π interactions. The contribution of ion exchange to the overall adsorption of Zn(II) and Ni(II) on ACFs was less than 3.3 % and can be considered negligible. © 2013 Springer Science+Business Media Dordrecht.

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.

Graphene oxide (GO) prepared by modified hummers method was used as adsorbent for removal of heavy metal ions. The oxygenous functional groups on the surface of GO were primarily responsible for the sorption of metal ions. The effects of the parameters of pH value, contact time, Cu(II) concentration, and adsorbent dosage on adsorption were examined. The sorption process conformed to the Freundlich isotherm, and the maximum sorption capacity of 117.5 mg g⁻¹ was observed at an initial pH value of 5.3 after agitating for 150 min. It was also found that Cu-pretreated GO could be desorbed by HCl and the reusability of GO could still maintain above 90 % of its initial capability after ten cycles. The results suggest that GO is an effective adsorbent for copper ions removal in water treatment.

Papaya seed was used as biosorbent for removal of tannery dye (Direct Black 38) from aqueous solution. The papaya seed was characterized, and it posseses macro/mesoporous texture, large pore size, and a surface containing various organic functional groups. The initial dye concentration, contact time, and pH significantly influenced the adsorption capacity. Equilibrium data were analyzed by the Langmuir and Freundlich isotherm models. The equilibrium data were best represented by the Langmuir isotherm, with a high adsorption capacity of 440 mg g⁻¹. Adsorption kinetic data were fitted using the pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Boyd models. The adsorption kinetics for the dye onto papaya seed was best described by second-order kinetic equation. The adsorption process mechanism was found to be controlled by both external mass transfer and pore diffusion, but the external diffusion was the dominating process. Papaya seeds showed to be a promising material for adsorption of Direct Black 38 dye from aqueous solution.

The speciation of mercury (Hg) is a major determinant of its methylation rate by sulfate-reducing bacteria (SRB), considered the primary methylators. Under anoxic conditions, sulfur (S) cycling may have a significant influence on Hg complexation and methylation, by influencing both SRB activity and the pool of available reduced S ligands, as the presence of zero-valent sulfur (S(0)) in sulfidic water results in the formation of polysulfides. While SRB frequently coexist with S-oxidizing bacteria in natural environments, the effect that these organisms may have on methylation by SRB is not understood. In this study, we investigate the role of S(0) in methylation by SRB monocultures and cocultures with phototrophic green or purple S-oxidizing bacteria. In the coculture experiments, the presence of S-oxidizers was found to increase Hg methylation rates, apparently by maintaining favorable chemical speciation in the environment. The measured Hg methylation rates were in accord with predictions based on geochemical modeling of speciation. In SRB monoculture experiments conducted in the presence and absence of S(0), the data showed that at limited total Hg, the presence of polysulfides resulted in decreased Hg methylation, presumably by causing a decrease in the most bioavailable Hg–sulfide complexes. These results indicate that models of Hg speciation and methylation in the environment should include a detailed investigation of S redox speciation.

The objectives of this study were to assess susceptibility to acidification and nitrogen (N) saturation caused by atmospheric deposition to northeastern US forests, evaluate the benefits and shortcomings of making critical load assessments using regional data, and assess the relationship between expected risk (exceedance) and forest health. We calculated the critical loads of nutrient N and of sulfur (S) + N using the steady-state mass balance method at >4,000 regional and national vegetation and soil monitoring network plots in the northeastern USA. Regional calculations of critical loads necessitate use of soil maps which provide a range for each soil characteristic resulting in a broad range of critical load of S + N and exceedance values. For the scenario most representative of regional conditions, over 80 % of the critical loads fell into the range of 850–2050 eq ha⁻¹ yr⁻¹; at 45 % of the plots, deposition exceeded the critical load. In contrast, the critical load for nutrient N, 200–300 eq ha⁻¹ yr⁻¹, was lower. Site measurements, especially to estimate soil weathering, would increase the certainty of the critical load. We observed significant negative correlations between critical load exceedance and growth (17 species) and crown density (4 species); we observed significant positive correlations of exceedance with declining vigor (four species), with crown dieback (six species) and crown transparency (seven species). Among the species which demonstrate the most significant detrimental responses to atmospheric deposition are balsam fir, red spruce, quaking aspen, and paper birch. These results indicate that significant detrimental responses to atmospheric deposition are being observed across the northeastern USA.

The present work tested effects of a revegetation pattern conducted using Paulownia fortunei (Seem.) Hemsl. (Scrophulariaceae) on soil chemical properties and actinomycete community structure identified by terminal restriction fragment length polymorphism (T-RFLP) technology of 16S rDNA. The results indicated that P. fortunei planting with time effectively improved organic carbon and total nitrogen contents, as well as pH in heavy metal-contaminated soils and, at the same time, enhanced the retention of heavy metals such as Pb, Zn, Cu and Cd in soils. T-RFLP profiles of soil actinomycete communities digested from two restriction enzymes (HhaI and RsaI) showed different specific TRF patterns across four sites with different revegetation time. Nonetheless, number and diversity of terminal restriction fragments for soil actinomycete community increased gradually with P. fortunei planting time and followed consistent patterns with soil organic carbon, total nitrogen, pH and heavy metal contents. Our results revealed a great potential of P. fortunei to remediate heavy metal-contaminated soils.

Humic acids (HA) are known as the precursors of carcinogenic compounds formed by the disinfection of drinking water. While conventional treatments were found to be inefficient HA removal processes in drinking water, advanced oxidation processes have been proven to have a significant effect in the treatment of HA. The degradation of HA was investigated using nano-sized zinc oxide (ZnO)/laponite composite (NZLC). The reactions occurred in a UVC reactor by considering following variables: pH, initial HA concentration, catalyst loading, addition of hydrogen peroxide (H2O2), and catalyst reuse. Water samples containing HA were analysed by ultraviolet/visible spectrophotometer and high-performance size-exclusion chromatography. Initial HA concentrations were tested by the Langmuir-Hinshelwood model with k and K ads values, determined to be 0.126 mg/L.min and 0.0257 L/mg, respectively. The change in pH affected the HA degradation efficiency by the photocatalytic activity where it was higher under acidic conditions rather than alkaline ones. Optimal catalyst loading was proved to be a constrained factor in influencing the photocatalytic efficiency: the increase of catalyst concentration enhanced the HA decomposition efficiency up to an optimum value of 20 g/L, where there was no further degradation with excess loading. The addition of H2O2 was investigated through homogenous and heterogeneous photocatalysis, and, heterogeneous photocatalysis showed higher removal efficiency due to the combined effect of both catalysts and H 2O2. Finally, NZLC was effective for reuse and exhibited an excellent stability after six times of usage. © 2013 Springer Science+Business Media Dordrecht.