Three commercial electrodes, Ta-Ir/TiO₂, Rh-Ir/TiO₂, and PbO₂/TiO₂, were used as electrochemical anodes, and their performance was evaluated by the electrochemical oxidation of ammonia at neutral pH in a continuous electrochemical quadrangular reactor. Based on the cyclic voltammetry scans and volt-ampere relation analysis, in direct oxidation, the oxygen evolution from H₂O₂decomposition was completely inhibited, and more•OH radicals could be then generated over PbO₂/TiO₂and in the presence of powder activated carbon (PAC). PbO₂/TiO₂can be indicated as an appropriate for the direct electrooxidation of ammonia in an unpacked bed reactor. While the efficiency for direct oxidation of ammonia was similar for the three anodes in a PAC packed reactor due to the presence of PAC could avoid short circuit and enhance electric efficiency. In indirect oxidation mediated by active free chlorine, Rh-Ir/TiO₂was the most effective in ammonia removal when chloride was present in the reaction system, and the disappeared ammonia was mainly transferred to N₂, and only a small part was converted into nitrate (there was no nitrite detected during the reaction). The results indicated that Rh-Ir/TiO₂had the highest oxidation capability for ammonia compared with Ta-Ir/TiO₂and PbO₂/TiO₂. Hence, Rh-Ir/TiO₂based on a PAC packed bed reactor provides an alternative for the treatment of ammonia wastewater with high chloride concentration.

Mercury (Hg) in aquatic ecosystems is of great concern due to its toxicity, bioaccumulation, and magnification in the food web. The Tibetan Plateau (TP) is endowed with the highest and largest lakes on earth, whereas Hg distribution and behavior in lake waters are least known. In this study, surface water samples from 38 lakes over the TP were collected and determined for the total Hg (THg) concentrations. Results revealed a wide range of THg concentrations from <1 ng to 40.3 ng L⁻¹. THg in lake waters exhibited an increasing trend along the southeast to northwest transect over the TP. Strong positive correlations were observed between THg concentrations and salinity and salinity-related environmental variables, especially for total dissolved solids (TDS) and some of the major ions such as Na⁺, K⁺, and Cl⁻, suggesting the enrichment of Hg in saline lakes. The large-scale geographical pattern of climatic and environmental factors shows a decreasing precipitation and an increasing evaporation northwards and westwards and thereby induces gradient-enhanced enrichment of soluble substances in lake waters, which are likely to complex more Hg in northwestern TP. Our study provides the first comprehensive baseline data set of Hg in Tibetan lake waters and highlights the concurrent high Hg and salinity, representing valuable references and fundamental rules in further understanding the behavior and fate of Hg in lakes over the TP and perhaps high-altitude regions beyond.

Groundwater samples collected from an unconfined shallow aquifer were analysed for major and trace element (TE) concentrations with the aim to investigate small-scale variations possibly linked to fertilizer residual products applied until 2004. The field site, located near Ferrara (Northern Italy), covers an area of 200 m²and was a former agricultural field then converted into a park and equipped with a grid of 13 monitoring wells. Three monitoring campaigns were carried out in June 2007, March and June 2009 in order to detect spatial and temporal variations in water quality. Groundwater nitrate, chloride, bromide and sulphate concentrations decreased with time indicating that the fertilizer plume was slowly replaced by unpolluted groundwater. However, the groundwater composition showed values of TEs (Fe, Mn, Al, As and Hg) above the recommended international and national guideline values. Dissolved TE concentrations varied randomly in the three campaigns, while TEs in the solid matrix did not show particular enrichment factors induced by fertilizer use. The data indicated that the dominant factor involved in determining small-scale spatial variability of TE concentrations in this shallow aquifer was the sediment-water interaction, while the temporal variation of TEs was driven by the organic matter leaching from the topsoil and by water table oscillations, which in turn drove the groundwater redox status. This study emphasizes the need of small-scale TE spatial resolution to discriminate between anthropogenic non-point sources of pollution (like fertilizers) and background concentrations.

Since the last century, humanity has sought ways to minimize the impact of the industrial growth in the environment. The textile industry, as one of the major contributors to water pollution, has been dumping coloured effluents which cause great impact in water bodies. The electrolytic process not only degrades the colour of the effluent but also transforms recalcitrant substances by direct or indirect oxidation. The ecotoxicological tests are used nowadays as a way to verify the toxicity degree of water bodies polluted by industrial and farming activities. The ecotoxicological tests consist in exposing determined organisms to the samples with the intention to evaluate their toxicity by observing the organisms’ responses. This study had the objective to degrade, by electrolytic process, a simulated textile effluent containing a mixture of Acid Blue 40 and Acid Red 151 dyes and the toxicity evaluation of the treated effluent by ecotoxicological tests. The bioassays used were tests with seeds of Lactuca sativa (lettuce), Eruca sativa (rocket), and Cucumis sativus (cucumber). Tests with the micro crustaceous Artemia salina and the yeast Saccharomyces cerevisiae were also conducted. The electrolytic treatment degraded the initial colour of the textile effluent, and the ecotoxicological tests indicated low toxicity to the treatment.

Long-term impacts of acidic deposition on the Great Smoky Mountains National Park (GRSM) include elevated inputs of sulfate, nitrate, and ammonium; the depletion of available nutrient cations from soil; and acidification of high-elevation streams. Critical loads and target loads (CLs/TLs) are useful tools to help guide future air quality management. We evaluated past and potential future effects of nitrate and sulfate deposition for 12 watersheds in the GRSM, USA, using the hydrochemical model, photosynthesis evapotranspiration biogeochemical (PnET-BGC). Two of the streams studied were listed by the state of Tennessee as impaired due to low stream pH. We reconstructed historical meteorological, atmospheric deposition, and land disturbance data for study watersheds for the period 1850 to present for model hindcasts. As future emissions are expected to decline, the model was run under a range of future scenarios from 2008 to 2200 of decreases in sulfate, nitrate, and ammonium and combinations of sulfate and nitrate deposition to estimate CLs and TLs of how watersheds might respond to emission control strategies. Model simulations of stream chemistry generally agreed with long-term (>10 years) observations. Model hindcasts indicate that watersheds in the GRSM are inherently sensitive to acidic deposition. Simulated mean projected stream ANC of 71 μeq/L (range 32 to 107 μeq/L) prior to industrial development (~1850) decreases in response to historical acidic deposition to 33 μeq/L (−13 to 88 μeq/L) in 2007. Future model projections show that decreases in sulfate deposition result in smaller increases in stream ANC compared with equivalent decreases in nitrate deposition; simultaneous controls on nitrate and sulfate deposition are more effective in ANC increases than individual control of nitrate or sulfate. Although there are no current programs in the USA to control ammonia emissions, model simulations suggest that decreases in ammonium deposition could also help mitigate acidification to a greater extent than equivalent controls on nitrate deposition.

The soils found in urban remnant patches may be considered anthropogenic inner urban soils—soils within the administrative boundaries of a municipalities influenced by activities adding artefacts into the soils. Such activities include housing, trading, traffic, production, and disposing. The objective of this study is to determine the scope to which field spectroscopy methods can be used to extend the knowledge of urban soils features and components. The spectroscopy techniques are used broadly for determining specific components or for differentiating between known ones. Moreover, this technique is able to determine low concentration in various phases and to trace hazardous material, and most studies are keen on quantification of those hazardous. In this paper, a top–down analysis for detecting the presence of minerals, organic matter, and pollutants in mixed soil samples is developed and presented. The developed method applies spectral activity (SA) detection in a structured hierarchical approach to quickly and, more importantly, accurately identify dominant spectral features. The developed method is adopted by multiple in-production tools including continuum removal normalization, guided by polynomial generalization, and spectral-likelihood algorithms: orthogonal subspace projection (OSP) and iterative spectral mixture analysis (ISMA).

Pig farms have achieved importance in the last few decades from the perspective of environment protection as a consequence of the intensive rearing systems in livestock production. Ammonia (NH₃) and greenhouse gases (GHG), such as methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O), are emitted from slurry storage at farm prior to land application, but little is known about these losses under on-farm conditions in Spain. This study assessed the influence of management and environmental parameters on NH₃ and GHG emissions from slurry storage in spring and autumn. Gas emissions were measured in a commercial pig-fattening farm from two lagoons (1000 and 768 m³ capacity, respectively) during 30 days by the floating dynamic chamber system in spring and autumn 2011 (average temperature 19 and 9 °C, respectively). Low NH₃ and CH₄ emissions were registered in spring (range 10–406 and 3–17 mg m⁻² min⁻¹, respectively) probably as a result of low pH values of stored slurry (6.5 to 7.0) and rainfall. High variability on NH₃, CH₄, and CO₂ emissions was observed as a result of differences in temperature and rainfall. No NH₃ emission and low CH₄ and CO₂ emissions were observed in autumn (average 1.2 ± 0.9 and 27 ± 22 mg m⁻² min⁻¹, respectively). Slurry loading operations increased NH₃ losses from storage.

Removal of p-nitrophenol (PNP) from aqueous solutions using fibrous peat has been investigated in this study by batch adsorption experiments. Factors that can affect the adsorption process, such as pH, temperature, initial PNP concentration and contact time, have been investigated. Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) measurements have also been obtained in order to study the adsorption mechanism of PNP by peat. The Langmuir and Freundlich equations have been applied to investigate the equilibrium. The data fitted the Langmuir isotherm well, with the maximum adsorption capacity decreasing with temperature from 23.4 to 16.1 mg g⁻¹. In general, the adsorption equilibrium was attained within 100 min. For the kinetics study, the best fit was obtained by the pseudo-second-order model instead of the pseudo-first-order model, both of which applied to the experimental data, whereas the results of intraparticle diffusion show a two-step adsorption process. The activation energy value of 70.31 kJ mol⁻¹, calculated from the Arrhenius equation, indicated a predominantly chemical adsorption, whereas the thermodynamic parameters, obtained by the van’t Hoff equation, were exothermic and spontaneous in nature.

Bioflocculation occurs in both engineered and natural systems and plays an important role in several water treatment processes as well as in pathogen transport and survival. In this study, bioflocculation was simulated in the laboratory to allow for well-controlled experiments. Escherichia coli and latex particles of varying sizes (3.2, 11 and 25 μm) were spiked into a buffer solution and were bioflocculated by adding alginate and varying amounts of calcium (0, 5, 10 and 15 mM). The extent of flocculation was determined by the calcium concentration, and the floc structure was modified by varying the particle size. The bioflocculation process was monitored with a dynamic particle analyzer, and the flocs formed were analyzed with respect to size, shape and porosity parameters. Larger flocs were observed to have a more heterogeneous structure with higher variation in shape and porosity compared to smaller flocs. Circularity and porosity parameters were shown to be strongly correlated with the calcium concentration. In addition, ultraviolet (UV) irradiation experiments were performed on flocculated and non-flocculated samples, and the inactivation data were assessed in light of floc characteristics determined with the particle analyzer.

The disposal of potentially toxic element (PTE)-loaded sludge that is produced during industrial or commercial wastewater treatments evoke concerns because of the probability of hazardous environmental consequences. In the current work, we proposed a chelant-assisted decontamination technique of the laboratory-produced PTE-loaded (As, Cd, Pb) polymeric-Fe-coated sludge and subsequent recovery of the chelants and PTEs. The chelant options include both biodegradable (EDDS, GLDA, and HIDS) and non-biodegradable (EDTA) alternatives. The washing performance was compared and discussed in terms of the solution pH and relative stabilities of the complexes of PTEs and chelants in solution. The changes in solution pH or chelants have no significant effect on the chelant-induced removal efficiency of Cd, and the same result was observed for Pb at extreme and moderate acidic pH. The As-extraction rate is also improved with chelant in the solution despite a limited interaction between the chelant and the arsenic species in the solution. The column-packed solid-phase extraction (SPE) system, which was equipped with macrocycle, chelating resin, or ion-exchange resin, was used to explore the corresponding separation performance of the PTEs and chelant. The macrocycle-equipped SPE system shows better selectivity than other SPEs in terms of extraction and recovery performance of the PTEs regardless of the chelants. Some unique points of the proposed process are minimum environmental burden due to the use of biodegradable materials in the washing solution and cost minimization by recycling the ingredients.