The adsorption of methylene blue cationic dye by water hyacinth root was studied in a batch system. The experimental data isotherms were analyzed using the Langmuir and Freundlich equations. The monolayer adsorption capacity for methylene blue dye was found as 0.187 kg kg−1. Three kinetic models (the pseudo-first order, the pseudo-second order, and the unified approach) were used to calculate the adsorption rate constants. The kinetic data along with equilibrium constants (maximum monolayer capacity and Langmuir constant) fitted well with unified approach model for different initial concentrations, and the rate constants were determined. Laboratory column experiments were conducted to evaluate the performance of water hyacinth root for methylene blue sorption under dynamic flow conditions. Breakthrough curves were plotted for the methylene blue adsorption on the adsorbent using continuous flow column operation by varying the bed height (0.06–0.12 m) and the feed concentrations (0.1–0.2 kg m−3). Different column design parameters, such as depth of exchange zone, adsorption rate, and adsorption capacity, were calculated. At the end, an attempt has also been made to model the data generated from column studies using the empirical relationship based on Bohart–Adams model.

Principal component analysis has been used as a tool for the detection of potentially outlying observations in multivariate data sets of polycyclic aromatic hydrocarbon concentrations (PAHs) in ambient air. The outlier statistic developed is the vector distance of each observation at a given site from the origin of principal component space. It is shown that the success of this technique relies on the usually very strong correlation of concentrations of different PAHs in ambient air, such that any deviation from this correlation is noteworthy. Indeed, it is so strong that the first principal component has been omitted from the technique since it is related mostly to absolute concentration. The method has been successful in detecting observations with unusually high concentrations of one or more PAHs. Moreover, it has been possible to identify periods where the UK pollution climate was abnormal during periods of extreme weather. Advice and guidance for the practical use of the technique is also given.

The adsorption and desorption of copper (II) ions from aqueous solutions were investigated using polydopamine (PD) nanoparticles. The nanoscale PD nanoparticles with mean diameter of 75 nm as adsorbent were synthesized from alkaline solution of dopamine and confirmed using scanning electron microscopy and X-ray diffraction analysis. The effects of pH (2–6), adsorbent dosage (0.2–0.8 g L−1), temperature (298–323 K), initial concentration (20–100 mg L−1), foreign ions (Zn2+, Ni2+, Cd2+, Fe2+, and Ag+), and contact time (0–360 min) on adsorption of copper ions were investigated through batch experiments. The isotherm adsorption data were well described by the Langmuir isotherm model. The maximum uptake capacity of Cu2+ ions onto PD nanoparticles was found to 34.4 mg/g. The kinetic data were fitted well to pseudo-second-order model. Moreover, the thermodynamic parameters of the adsorption (the Gibbs free energy, entropy, and enthalpy) were studied.

Waste stabilization pond (WSP) technology has been an active area of research for the last three decades. In spite of its relative simplicity of design, operation and maintenance, the various processes taking place in WSP have not been entirely quantified. Lately, modelling has served as an important, low-cost tool for a better description and an improved understanding of the system. Although several papers on individual pond models have been published, there is no specific review on different models developed so far. This paper aims at filling this gap. Models are compared by focussing on their key features like the presence and comprehensiveness of a water quality sub-model in terms of aerobic/anoxic and anaerobic carbon removal and nutrient removal; the type of hydraulic sub-model used (0D, 1D, 2D or 3D); the software used for implementation and simulation; and whether or not sensitivity analysis, calibration and validation were done. This paper also recommends future directions of research in this area. In-depth study of the published models reveals a clear evolution over time in the concept of modelling, from just hydraulic empirical models to 3D ones and from simple first-order water quality models to complex ones which describe key biochemical processes as a set of mathematical equations. Due to the inherent complexity, models tend to focus only on specific aspects whilst ignoring or simplifying others. For instance, many models have been developed that either focus solely on hydrodynamics or solely on biochemical processes. Models which integrate both aspects in detail are still rare. Furthermore, it is evident from the review of the different models that calibration and validation with full-scale WSP data is also scarce. Hence, we believe that there is a need for the development of a comprehensive, calibrated model for waste stabilization ponds that can reliably serve as a support tool for the improvement and optimization of pond design and performance.

As chemicals are widely used for snow and ice control of highway and airfield pavements or aircrafts, recent years have seen increased concerns over their potentially detrimental effects on the surrounding environment. The abrasives used for winter operations on pavements are also a cause of environmental concerns. After some background information, this paper presents a review of the environmental impacts of chemicals used for snow and ice control, including those on: surface, ground, and drinking waters; soil; flora; and fauna. The paper provides a state-of-the-art survey of published work (with a focus on those in the last two decades) and examines mainly the impacts of abrasives, chlorides, acetates and formates, urea, glycols, and agro-based deicers. Finally, we conclude with a brief discussion of public perception of such impacts and best management practices (BMPs) to mitigate them.

The magnetic-poly(divinylbenzene-1-vinylimidazole) [m-poly(DVB-VIM)] microbeads (average diameter 53–212 μm) were synthesized and characterized; their use as adsorbent in removal of Cr(VI) ions from aqueous solutions was investigated. The m-poly(DVB-VIM) microbeads were prepared by copolymerizing of divinylbenzene (DVB) with 1-vinylimidazole (VIM). The m-poly(DVB-VIM) microbeads were characterized by N2 adsorption/desorption isotherms, ESR, elemental analysis, scanning electron microscope (SEM) and swelling studies. At fixed solid/solution ratio the various factors affecting adsorption of Cr(VI) ions from aqueous solutions such as pH, initial concentration, contact time and temperature were analyzed. Langmuir, Freundlich and Dubinin–Radushkvich isotherms were used as the model adsorption equilibrium data. Langmuir isotherm model was the most adequate. The pseudo-first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models were used to describe the adsorption kinetics. The apparent activation energy was found to be 5.024 kJ mol−1, which is characteristic of a chemically controlled reaction. The experimental data fitted to pseudo-second-order kinetic. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes. The thermodynamic parameters obtained indicated the endothermic nature of adsorption of Cr(VI) ions. Morever, after the use in adsorption, the m-poly(DVB-VIM) microbeads with paramagnetic property were separeted via the applied magnetic force. The magnetic beads could be desorbed up to about 97% by treating with 1.0 M NaOH. These features make the m-poly(DVB-VIM) microbeads a potential candidate for support of Cr(VI) ions removal under magnetic field.

Wastewater samples originating from an explosives production plant (3,000 mg N l−1 nitrate, 4.8 mg l−1 nitroglycerin, 1.9 mg l−1 nitroglycol and 1,200 mg l−1 chemical oxygen demand) were subjected to biological purification. An attempt to completely remove nitrate and to decrease the chemical oxygen demand was carried out under anaerobic conditions. A soil isolated microbial consortium capable of biodegrading various organic compounds and reduce nitrate to atmospheric nitrogen under anaerobic conditions was used. Complete removal of nitrates with simultaneous elimination of nitroglycerin and ethylene glycol dinitrate (nitroglycol) was achieved as a result of the conducted research. Specific nitrate reduction rate was estimated at 12.3 mg N g−1 VSS h−1. Toxicity of wastewater samples during the denitrification process was studied by measuring the activity of dehydrogenases in the activated sludge. Mutagenicity was determined by employing the Ames test. The maximum mutagenic activity did not exceed 0.5. The obtained results suggest that the studied wastewater samples did not exhibit mutagenic properties.

Contamination from tank installations in the Arctic is an important issue, since tanks are a necessary feature of all communities, and may be a source of local pollution. Soil samples from below and around three tank installations and one reference site in the Northwest Greenlandic village of Tasiusaq were analysed for the total content of hydrocarbons (THC), lead, cadmium and organic content in the soil. Concentrations up to 77,000 mg/kg DW THC were found, mainly as weathered oil products. Elevated levels of lead and cadmium were also found in many of the samples, with concentrations up to 300 and 2 mg/kg DW, respectively. The tank installation areas were contaminated by THC, lead and cadmium compared to the reference site, and parts of the areas were highly contaminated, exceeding the Danish environmental quality criteria. The correlation between lead and cadmium concentrations was significant (p < 0.01), while no correlation existed between THC and organic matter. Small spills from daily use of the tank installations are suggested to be the source of the THC contamination, whereas the lead and cadmium contamination is suggested to originate primarily from the plume of smoke from waste incineration.

Novel adsorption materials—Fe–Ni nanostructures and C/Fe–Ni composites—with the carbonaceous material coming from sewage sludge, have been developed and evaluated to remove indigo carmine from aqueous solution. The adsorbents were characterized by transmission and scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and Brunauer–Emmett–Teller analysis. Sorption kinetics and isotherms were determined and the adsorption behaviours analysed. All adsorbents here studied have exhibited good efficiency to remove indigo carmine from aqueous solution. Pseudo-second-order kinetic and Langmuir–Freundlich isotherm models were successfully applied to the experimental data. Fe–Ni nanostructures adsorption capacity was 977.18 mg/g, followed by C/Fe–Ni 75/25% composite with 654.33 mg/g, and a lowest value, 486.41 mg/g, was obtained for C/Fe–Ni 95/5% composite. It can be suggested that the sorption mechanism of the dye is chemisorption on these heterogeneous novel, cheap and efficient functional materials. All materials provide the highest adsorption capacities in pH between 4 and 10. In addition, three sorption–desorption cycles using 30% H2O2 solution and distilled water were performed; sorption efficiencies of both composites (C/FeNi 75/25% and C/FeNi 95/5%) decreases in each cycle, but this behaviour is not observed for FeNi nanoscale oxides.

Arbuscular mycorrhizal fungi (AMF) hold a crucial role in ecosystems because they are involved in nutrient cycling between soil and plants. This work aimed at evaluating the impacts that atmospheric pollution by polycyclic aromatic hydrocarbons may have on infectivity of indigenous AMF in soils. Two agricultural soils (Maconcourt, La Bouzule) were exposed for 2 weeks to ambient air (control, C) or to atmospheric phenanthrene (PHE) deposition (180 μg m−3 air). After exposure, soils were divided into a top (0–1 cm) and a bottom (1–15 cm) layer fraction. AMF infectivities of soils were determined after 2 weeks of atmospheric exposition using leek (Allium porum) as bioassay plant. Atmospheric PHE was mainly recovered in the top layer of soil (500–1,350 μg kg−1) of both soils and did not readily diffuse into the depth. Atmospheric contamination led to decreases in AMF infectivities of the top layer in both soils and affected the growth of leeks. Our results not only report evidence that infectivity of indigenous AMF is sensitive to PHE in soils but also emphasize that AMF are primary affected by the soil layer regardless to the pollution level.