In recent years, much attention has been devoted in developing inexpensive or alternative systems for treating acid mine drainage (AMD). Manganese is a common component of AMD, and it is traditionally removed by precipitation. However, in order to meet the standard limits for discharging, usually <1 mg L, it is necessary to raise the pH above 10 which implies in high consumption of reagents and a final pH that does not meet the required value for discharging. This study investigated the removal of manganese from an acid mine effluent and laboratory solutions by using an industrial residue consisted of manganese dioxide (MnO). The pH of the acid effluent is around 2.7, and the manganese concentration is approximately 140 mg L. Batch experiments assessed the influence of pH and the efficiency of manganese dioxide (MnO) in the Mn removal. In the presence of MnO, the metal concentration meets the discharging limit at pH range of 6.8 to 7.2. Experiments carried out with columns packed with MnO assessed the influence of the flow rate on the process. Best results were obtained for columns fed with mine water neutralized with limestone at pH 7.0 and a residence time of 3.3 h. The maximum manganese loading capacity for MnO was around 14 mg g. RAMAN spectroscopy showed that the MnO is essentially constituted of pyrolusite. In addition, the solid hausmannite (MnO) was observed on the surface of the MnO residue after its contact with the Mn solution.

The impacts of dissolved organic matter (DOM) on the removal of 17β-estradiol (E2) in horseradish peroxidase (HRP)-mediated oxidative coupling systems were investigated in this study. The results showed that the removal rate of E2 and the affinity of HRP to E2 had been significantly decreased in the presence of DOM. Compared with urban sludge DOM (USDOM), river sediment DOM (RSDOM), which features relatively low aromaticity and molecular weight and a large number of O-containing groups, more strongly inhibited the E2–HRP–H₂O₂ reactions than USDOM. The products were analyzed with electrospray ionization mass spectrometry. The results suggested that the self-coupling of E2 was suppressed in the presence of DOM, likely resulting from cross-coupling between DOM and E2 or self-coupling of DOM in the HRP system. The results are useful in understanding the fate of estrogens in natural systems.

The work reported here demonstrates that zero valent iron (ZVI), a material used in permeable reactive barriers, yields degradation rate constants for trichloroethylene (TCE) that are considerably different depending on whether they are determined in deionised water or in groundwater. Batch studies using ZVI and TCE-spiked deionised (DI) water and TCE-contaminated groundwater revealed that within 50 h, 80 % of the TCE present in groundwater was mineralised, compared to TCE-spiked deionised water in which only 50 % of TCE was demineralised by ZVI in 50 h. In both TCE-spiked groundwater and DI water, cis-dichloroethylene was the major by-product, and it was reduced together with TCE after 96 h of treatment. Along with changes in concentrations of TCE and its metabolites, increased levels of chloride confirmed TCE degradation. TCE-spiked groundwater gave a higher rate constant (k) under similar conditions. The elevated chloride (830 mg/l) concentrations of the groundwater could be a possible reason for this higher rate constant, in spite of the fact that groundwater also contains higher inorganic carbon (132 mg/l) and calcium (26 mg/l) and has a pH of 7.9. The rate constant (0.017-0.03223 h-1) and half-life of TCE (21.5 to 40 h) are within the reported ranges in the literature. The implications of the results for the performance of ZVI in permeable reactive barriers are that not only groundwater chemistry, but also groundwater flow conditions, plays a key role in TCE degradation. © 2013 Springer Science+Business Media Dordrecht.

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.

Geochemical characterization of two landfills, one closed and the other still active, both located near Komotini (Thrace, Greece), has been carried out. The aim was to provide an integrated and reliable methodology for a rapid assessment of the real impact of a municipal solid waste landfill, in the main environmental matrices (air and water) of the surrounding areas. The chemical (CO₂, CH₄, CO, H₂, N₂, and O₂ + Ar) and isotopic characterization (δ¹³C₍CO₂₎ and δ¹³C₍CH₄₎) of landfill gas and chemical (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, SO₄ ²⁻, HCO₃ ⁻, NH₄ ⁺, NO₃ ⁻, NO₂ ⁻, B, COD, Fe, Mn, As, Cr, Ni, Cu, Zn, Cd, Pb, and Hg) and isotopic analysis (δD, δ¹⁸O, tritium content, and δ¹³CDIC) of leachate, stream waters and groundwaters, and flux survey on the air–soil interface has been carried out. Combined chemical and isotopic analysis of the fluids collected inside and in the surroundings of the Komotini landfills supply a detailed picture of biogas emission and composition as well as of leachate chemistry and interaction with local waters. The results arising in this case study demonstrate that it is possible to propose a quick and reliable geochemical protocol to get a detailed picture of the state of health of the environment around a landfill.

A neutrophilic, autotrophic bacterium that couples iron oxidation to nitrate reduction (iron-oxidizing bacteria [IOB]) under anoxic conditions was isolated from a working bioremediation site in Trail, British Columbia. The site was designed and developed primarily to treat high concentrations of Zn and As that originate from capped industrial landfill sites. The system consisted of two upflow biochemical reactor cells (BCR) followed by three vegetated wetland polishing cells with sub-surface flow and a holding pond. During a 5-year period (2003–2007), the system treated more than 19,100 m³ of contaminated water, removing and sequestering more than 10,700 kg of As, Zn and sulfate at average input water concentrations of: As, 58.6 mg l⁻¹ (±39.9 mg l⁻¹); Zn, 51.9 mg l⁻¹ (±35.4 mg l⁻¹) and SO₄ ²⁻, 781.5 mg l⁻¹ (±287.8 mg l⁻¹). The bacterium was isolated in order to better understand the mechanisms underlying the consistent As removal that took place in the system. Analysis using Basic Local Alignment Search Tool (BLAST) database showed that the closest homologies are to Candidatus accumulibacterphosphatis (95 % homology), Dechloromonas aromatica (94 %), and Sideroxydans lithotrophicus ES-1 (92 %) Within the BCR cells, the IOB oxidized Fe²⁺ generated by iron-reducing bacteria (IRB); the source of the iron was most likely biosolids and coatings of iron oxide on locally available sand used in the matrix. We have provisionally designated the novel bacterium as TR1.

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 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.

Emissions of volatile organic compounds (VOCs) were studied from three heavily polluted rivers (Huijiang, Nancun, and Zengbian Rivers) in Guangzhou, South China. A total of 49 species of VOCs were identified. Nancun River had the highest concentration of total VOCs (TVOCs), which ranged from 1,467 to 5,522 μg m⁻³. Trichloroethene, benzene, toluene, ethylbenzene, m/p-xylene, o-xylene, styrene, and 1,3,5-trimethylbenzene were the main pollutants. The levels of VOCs evaporated from the three rivers exhibited different patterns. Correlations between the concentrations of major VOCs were established and found to be statistically significant, except for o-xylene. The ratios of toluene/benzene, ethylbenzene/benzene, and xylene/benzene were estimated and found to be higher than widely reported in the literature. TVOC fluxes in the three rivers were calculated to be the range from 24.8 to 765 μg m⁻² h⁻¹. This study provides a regional background for the emission inventories of VOCs from heavily polluted rivers in southern China and provides resource managers with important information to guide remediation and policy concerning VOC emissions to the environment.

As a polycyclic aromatic hydrocarbon (PAH), pyrene is one of hazardous persistent organic pollutants in the aquatic environment. The aim of this study was to investigate the influence of denitrifying conditions on pyrene degradation in a pure culture. With a strain isolated from petrol-contaminated river sediment, treatments of pyrene biodegradations were set up using various ratios of nitrate to nitrite (NO₃ ⁻/NO₂ ⁻). Results showed that various NO₃ ⁻/NO₂ ⁻ conditions significantly influenced the anaerobic pyrene degradation efficiency. Nitrite could induce the complete denitrification process so that NO₂ ⁻ acted as a key factor to promote high degradation efficiency. The low N treatment of NO₃ ⁻ and NO₂ ⁻ concentrations made the denitrifying-pyrene-degradation process more effective. Additionally, high C/N value stimulated high degradation rates. High concentrations of NO₃ ⁻ and NO₂ ⁻ as well as toxic intermediate product accumulation might inhibit the bacterial growth and biodegradation process. The information from this study should be useful to design bioremediation strategies of PAH.