The catalytic removal of Hg⁰ was investigated to ascertain whether the catalysts could simultaneously possess both thermo- and photo-catalytic reactivity. The immobilized V₂O₅/TiO₂ and WO₃/TiO₂ catalysts were synthesized by sol-gel method and then coated on the surface of glass beads for catalytic removal of Hg⁰. They were also characterized by SEM, BET, XRD, UV-visible, and XPS analysis, and their catalytic reactivity was tested under 100–160 °C under the near-UV irradiation. The results indicated that V₂O₅/TiO₂ solely possessed the thermo-catalytic reactivity while WO₃/TiO₂ only had photo-catalytic reactivity. Although the synthesis catalytic reactivity has not been found for these catalysts up to date, but compared with TiO₂, the removal efficiencies of Hg⁰ at 140 and 160 °C were enhanced; particularly, the efficiency was improved from 20 % at 160 °C by TiO₂ to nearly 90 % by WO₃/TiO₂ under the same operating conditions. The effects of doping amount of V₂O₅ and WO₃ were also investigated, and the results showed that 10 % V₂O₅ and 5 % WO₃/TiO₂ were the best immobilized catalysts for thermo- and photo-catalytic reactivity, respectively. The effect of different influent concentrations of Hg⁰ was demonstrated that the highest concentration of Hg⁰ led to the best removal efficiencies for V₂O₅/TiO₂ and WO₃/TiO₂ at 140 and 160 °C, because high Hg⁰ concentration increased the mass transfer rate of Hg⁰ toward the surface of catalysts and drove the reaction to proceed. At last, the effect of single gas component on the removal of Hg⁰ was also investigated.

Geothermal energy is known to be a clean and renewable energy resource. However, geothermal fluid has significant impacts on surface water quality when disposed in an uncontrolled manner due to the high concentrations of numerous dissolved constituents and the elevated thermal content. The geothermal fluid in western Anatolia typically contains high concentrations of arsenic, boron, and lithium that are toxic to human and plant life. A river system in western Anatolia, Turkey, receives uncontrolled waste geothermal fluid discharge from three fields and is thermally and chemically contaminated. A one-dimensional water quality model is developed to assess the extent and strength of geothermal pollution in the river system. The calibrated and verified model results revealed that although both the point and nonpoint sources of contamination are influential in the water quality degradation, point discharges of waste geothermal fluid were responsible for dramatic increases in the contaminant concentrations and water temperature in the river. The model was later used to analyze the potential measures to improve the degraded water quality and compare the effectiveness of structural and non-structural mitigation scenarios.

The adsorption of ethyl acetate, a volatile organic compound, on activated carbons, synthesized from various precursors based on by-products and waste materials—polymer, biomass, coal tar pitch—was studied. The activated carbons were prepared by thermochemical treatment of the precursors, carbonization, and subsequent activation with water vapor. Surface and textural properties of obtained carbon adsorbents were characterized by low-temperature N₂ adsorption, Boehm’s method, etc. The activated carbons are distinguished by relatively high surface area and developed pore structure. The adsorption investigations were performed with water solutions of ethyl acetate, and the obtained results fit well the Langmuir model, as well as the Freundlich model. All activated carbons demonstrated considerably high adsorption capacity in the range 160–450 mg/g. The obtained data indicate that the adsorption ability of activated carbon toward ethyl acetate depends on the surface area, and it increases with increasing the content of mesopores, where ethyl acetate molecules are preferably adsorbed.

Seven full-scale wastewater treatment plants were investigated to highlight the effectiveness of each treatment stage on removing Escherichia coli. The primary sedimentation achieved an average E. coli removal efficiency of 30.5% which was much lower than the suspended solids (58%), thus, revealing the absence of a linear relationship between the two parameters. Biological processes proved to be very important in the removal of E. coli through adsorption inside the sludge flocs and complex decay (mortality). In biological processes with a long retention time, such as activated sludge denitrification-nitrification, the decay was very important, whereas in the more traditional activated sludge process, without nitrification, the contribution of adsorption and mortality was quite balanced. Overall, the mechanical-biological treatment achieved a removal efficiency of 91.8–96.5% depending on the process. Additional removal can be achieved by disinfection. The effectiveness of E. coli removal with sodium hypochlorite was strictly depended on the product of residual chlorine (C R) with the contact time (t). The experimental curve fitted the Collins model well, with a standard deviation of less than 7%.

A new procedure for the determination of chromium species in polluted environmental samples by flame atomic absorption spectrometry was developed in this work. A new material containing 1,5-diphenylcarbazone included in a polymeric matrix was prepared and employed as a solid-phase extraction material for selective separation of Cr(III) ions under dynamic conditions. Chromium(III) ions were retained on this sorbent with high efficiency and repeatability (95 %, RSD = 1 %) from solutions with pH 9.0. The quantitative recovery of analyte was obtained with 0.1 mol L⁻¹ EDTA. The concentration of Cr(VI) ions was calculated from the difference between the concentration of total chromium and Cr(III) ions. The prepared sorbent exhibits good chemical and mechanical stability, sorption capacity and selectivity towards Cr(III) ions in the presence of Cu(II), Ni(II), Mn(II) and Ca(II) ions. The accuracy of the separation method was proved by analysis of reference material of wastewater RES 10.2. The developed procedure was applied for chromium speciation analysis in municipal sewage samples.

Along the southeastern coast of Costa Rica, a variety of pesticides are intensively applied to produce export-quality plantains and bananas. In this region, and in other agricultural areas, fish kills are often documented by local residents and/or in the national news. This study examines principal exposure pathways, measured environmental concentrations, and selected toxicity thresholds of the three most prevalent pesticides (chlorpyrifos, terbufos, and difenoconazole) to construct a deterministic risk assessment for fish mortality. Comparisons of observed pesticide concentrations, along with estimated biological effects and observations during actual fish kills, highlight gaps in knowledge in correlating pesticide environmental concentration and toxicity in tropical environments. Observations of fish kill events and measured pesticide concentrations in the field, along with other water quality indicators, suggest that a number of environmental conditions can interact to cause fish mortality and that current species toxicity datasets may not be applicable for estimating toxicological or other synergistic effects, especially in tropical environments.

Cr(VI) adsorption onto a novel fibrous ethylenediamine-functionalized polyethylene/polypropylene (PE/PP-g-PGMA-EDA) nonwoven fabric was investigated in aqueous solutions. The ethylenediamine functionalities were immobilized on the PE/PP nonwoven fabric through the epoxy groups of poly(glycidyl methacrylate) (PGMA) grafted to the fibers via radiation-induced emulsion graft polymerization in aqueous solution. Optimum conditions for grafting and subsequent modification steps were determined. The adsorbents were characterized by FTIR, XPS, and SEM techniques. Cr(VI) adsorption was studied in batch mode as a function of pH, feed concentration, contact time, ionic strength, and coexisting anions. The nonwoven adsorbent exhibited efficient, rapid Cr(VI) removal; high adsorption capacity; and insignificant interference from coexisting ions. Adsorbed Cr(VI) ions were desorbed using 2 M HNO₃ solution, and the adsorption capacity of the nonwoven fabric was retained for four adsorption–desorption cycles. The data for Cr(VI) adsorption on the nonwoven fabric fitted to the Langmuir isotherm model well. The maximum adsorption capacity for the Langmuir isotherm was 178.9 mg Cr(VI)/g polymer at pH 3.00. Graphical Abstract ᅟ

Catalytic destruction of PCDD/Fs (polychlorinated dibenzo-p-dioxins and furans) over V₂O₅-CeO₂/TiO₂ catalyst was investigated at a low temperature range of 140–180 °C, in the absence and presence of ozone (200 ppm). Nano-TiO₂ support was used to prepare the catalyst by step impregnation method. A stable PCDD/Fs-generating system was established to support the catalytic destruction tests. In the presence of ozone alone, destruction efficiencies of PCDD/Fs are between 32.2 and 43.1 % with temperature increasing from 140 to 180 °C. The activity of V₂O₅-CeO₂/TiO₂ catalyst alone on PCDD/Fs destruction is also studied. The increase of temperature from 140 to 180 °C enhances the activity of catalyst with destruction efficiencies increasing from 54.7 to 73.4 %. However, ozone addition greatly enhances the catalytic activity of V₂O₅-CeO₂/TiO₂ catalyst on PCDD/Fs decomposition. At 180 °C, the destruction efficiency of PCDD/Fs achieved with V₂O₅-CeO₂/TiO₂ catalyst and ozone is above 86.0 %. It indicates that the combined use of ozone and catalyst reduces the reaction temperature of PCDD/Fs oxidation and offers a new method to destroy PCDD/Fs with high destruction efficiency at a low temperature. Furthermore, the destruction efficiencies of 17 toxic PCDD/F congeners, achieved with ozone alone, catalyst alone, and catalyst/ozone are analyzed.

The drastic desiccation of the Aral Sea has led to severe desertification of the former lake areas. Dust storms occur frequently, causing regional environmental degradation of the Aral basin and a serious ecological disaster. Knowledge of the temporal variability in dust emissions and the potential diffusion characteristics of dust aerosol originating from the Aral Sea basin in recent years are, however, lacking. To address this knowledge gap, we studied the interannual and intraannual changes in dust aerosol from the Aral Sea basin and its potentially seasonal diffusion characteristics from 2005 to 2013 using Ozone Monitoring Instrument (OMI) aerosol data (2005–2013) and the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. Results show that the OMI aerosol index (AI) annual mean, standard deviation, median, and maximum values exhibit a strong increasing trend because of the continuous decrease in the water level since 2005. The annually mean OMI AI increases to 1.47 by 2013. Peak AI values are recorded in spring (March–May) and early winter (November–January of the following year), indicating notifying seasonal differences. The potential distance and height of air parcel trajectories to the northeast are greater than those to the west and south, whereas the air parcel trajectory proportion of the former is lower than that of the latter. The potential transport distance of dust aerosol to the northeast is greatest in spring and winter. This transport distance is less in autumn, with the minimum observed in summer. Dust transport distance to the west and south in different seasons is not significantly different. The present results may help in further understanding the emission, long-range transport, and deposition of dust from the dry lake bed of the Aral Sea as well as providing a motivation for the sensible use and protection of these tail-end lakes.

Soil–air partitioning is an important diffusive process affecting the environmental fate of organic compounds. In this study, the soil–air partition coefficients (K SA) for dichloro-diphenyl-trichloroethane and its metabolites (designated as DDTs, the sum of p, p′- and o, p′-isomers of DDT, DDD, and DDE) over a temperature range from 5 to 50 °C in artificial solid media were determined by a solid–fugacity meter. The results showed that log K SA gradually increased with soil organic carbon content (f OC). A reversed relationship was observed between log K SA values and the environmental temperatures (T). The enthalpy changes (ΔH SA) indicated that o, p′-isomers required more energy to release from artificial solid media to the gas phase. Moreover, with increasing temperature, the slope of the regression line of log K SA vs. log K OA (octanol–air partition coefficient) was approaching to 1. Based on factors influencing soil–air partitioning and the experimental data, a multiple parameter (T, f OC, and K OA) model was used to predict the K SA values for DDTs.