Pyrite, FeS₂, is the most common sulfide mineral. The aim of this work was to assess the oxidative ability of H₂O₂ in presence of natural pyrite by employing reactive black 5, acid red GR, and cationic red X-GRL as model pollutants. The effects of H₂O₂ dosage, pyrite loading, and initial pH on reaction were investigated. The results reveal that natural pyrite-promoted H₂O₂ has a great activity in the decoloration of azo dyes. About 85 % of reactive black 5 and acid red GR can be removed within 10 min when 0.3 mM H₂O₂ and 0.3 g/L pyrite are used with initial pH values ranging from 6.32 to 6.96. The discoloration efficiencies are demonstrated to be less sensitive to the initial solution pH value. Approximately 90 % of discoloration for reactive black 5 and acid red GR can be achieved when initial pH value ranges from 2 to 10. Ion leaching experiments show that high levels of ferrous iron and sulfate can be detected when natural pyrite is added to dye solution alone. To gain an understanding of the reaction mechanism and the role of natural pyrite takes in these processes, techniques including scanning electron microscope, X-ray diffraction, and X-ray photoelectron were employed to characterize the solid sample and ion leaching experiments were also carried out. Results indicate that the determined high levels of ions have resulted from the dissolution of FeSO₄·H₂O formed on the surface of pyrite and the homogeneous Fenton reaction initiated by ferrous iron in presence of H₂O₂ is mainly responsible for the observed fast color removal rate.

Sorption characteristics of phenanthrene were studied in batch equilibrium experiments with 32 Australian soils that varied widely in physicochemical properties. Sorption of phenanthrene varied widely among the soils and was generally nonlinear, with the nonlinearity index (n) of the Freundlich isotherm varying from 0.62 to 1.01. Simple regression analyses revealed that total organic carbon (TOC) accounts for about 68 % of the variation in the partition coefficient (K′ f ) for sorption among the soils at an equilibrium concentration (C e ) of 0.05 mg/L. The organic carbon normalized distribution coefficient (K OC ), varied considerably between soils with >70 % of the variance of logK OC being accounted for by logTOC, clay and log dissolved organic carbon (DOC). These results show that the phenanthrene C e is influenced by both TOC as well as the DOC in soil suspensions. The effects of ionic strength (IS) and index cation were investigated using four contrasting soils. Results show that with an increase in IS from 0.03 to 0.15 M sorption of phenanthrene generally increased in CaCl2 background solutions, whereas the effect was less significant and variable in NaCl background solutions. Sorption of phenanthrene was slightly higher at low IS (0.03 M) with Na+ as index cation compared with that of Ca2+, whereas an opposite trend was observed at higher IS (0.15 M). For two soils high in TOC, the flocculation of endogenous DOC in the presence of Ca2+ reduced the influence of background electrolyte and resulted in a more linear sorption isotherm as well as higher sorption capacity. This trend was more significant with Ca2+ relative to Na+. © 2013 Springer Science+Business Media Dordrecht.

Rural non-point source (RNPS) water pollution control is problematic in Hubei Province, which is a typical agricultural region with abundant rainfall and a developed natural surface water network. The concept of best management practices (BMP) originating from the USA has already been introduced with the aim to reduce the application of chemical fertilizers and pesticides, and water and soil loss. However, a comprehensive evaluation of rural wastewater and nutrient reutilization to benefit the rural communities and the environment has not been attempted. To fill this gap, this review paper explores the major contributors of RNPS water pollution in Hubei Province, assesses the status of watercourses and discusses the prevalent ecological engineering techniques including vegetated filter strips (VFS), ecological ditches (ED), constructed wetlands (CW), and biogas plants (BP) with respect to aspects such as water purification, energy generation, and nutrient reduction and recirculation. Findings indicate that RNPS water pollution continuously increased for the past 10 years. Chemical fertilizers, poultry and livestock breeding, aquaculture, and rural living are the major sources of elevated chemical oxygen demand, ammonia–nitrogen, total nitrogen, and total phosphorus loads discharged to receiving watercourses. Finally, ecological engineering technologies such as VFS, ED, CW, and BP are proposed for villages and communities to combat RNPS water pollution. BMP are a promising approach to create a sustainable agricultural system, improve the rural energy consumption structure and living conditions, decrease wastewater discharges, and reduce chemical fertilizer application rate.

Organoclays possess unique adsorption behaviour towards hydrophobic organic contaminants. They can also remediate ionic contaminants such as heavy metals and metalloids. The objective of the present study was to prepare organoclay and organoclay mixtures efficient to adsorb both cationic and anionic contaminants. The adsorbents were characterised by X-ray diffraction and infrared spectroscopy. Trivalent (Cr3+) and hexavalent (Cr2O 7 2-) chromium were selected as the model contaminants representing cationic and anionic properties. Bentonite modified with cationic surfactant hexadecyl trimethylammonium bromide at double the cation exchange capacity of the clay remarkably improved Cr2O7 2- adsorption capacity (as high as 0.49 mmol g-1). Similarly, its modification with anionic surfactant sodium dodecyl sulphate at the same dosage improved Cr3+ adsorption (as high as 0.36 mmol g -1). When these two organoclays were physically mixed in equal proportions (1:1), the resultant organoclay mixture efficiently adsorbed both Cr3+ (as high as 0.21 mmol g-1) and Cr2O 7 2- (as high as 0.32 mmol g-1) implying that the mixture could remediate both anionic and cationic contaminants simultaneously. The adsorption of Cr3+ by the organoclay and organoclay mixture fitted well to the Langmuir isothermal model whereas the adsorption of Cr2O7 2- fitted well to the Freundlich model. © 2013 Springer Science+Business Media Dordrecht.

Spatial and temporal trends in nutrient concentrations and loads were analyzed for three rivers in the Red River watershed, Manitoba, Canada to determine changes in nutrient export across hydrologic seasons and along river continua in the Great Plains. Annual patterns in all three rivers were strongly influenced by the snowmelt period: 25-89 % of the total annual river volume, 42-92 % of the total annual TP load, and 41-81 % of the total annual TN load were delivered during snowmelt. Concentrations of TP and TN varied among the hydrologic seasons (snowmelt, summer, fall, and winter), but showed more variability and larger values during winter and snowmelt, with peak values reaching 1.960 mg TP L-1 and 16.07 mg TN L-1. Although the flat topography and semi-arid climate of the Red River watershed results in hydrological disconnects along river continua, discharge and nutrient export increased along the three river gradients. In contrast, TP or TN concentrations showed no significant longitudinal change for the two agriculturally dominated watersheds yet increased along the forested stream. Our finding that TP and TN exports from northern Great Plains rivers are strongly influenced by seasonal hydrology, with snowmelt being a critical period for nutrient export has implications for design and implementation of appropriate management practices to minimize nutrient export to proximal and downstream aquatic ecosystems. © 2013 Her Majesty the Queen in Right of Canada.

Mining creates large amounts of processed waste in the form of mine tailings. Sulfide mine tailings are of particular concern due to the biotic and abiotic oxidation of sulfide minerals that release acidity and metals into the environment. Revegetation can be employed to mitigate the spread of tailings in the environment. Revegetation often involves ameliorating tailings with organic materials to promote plant growth and improve tailings physicochemical structure. We amended plots in the Central Manitoba Mine tailings pond with humic substances applied at rates up to 4 g C kg-1 through roto-tilling and seeded with Medicago sativa and Elymus trachycaulus in 2003 and 2004. The humic substances improved tailings fertility by increasing macro aggregation, organic carbon, and macronutrients but also resulted in a short-term increase in electrical conductivity levels. In the first growing season the humic amendment had little effect on plant yield, except in the 2003 experiment where the yield of E. trachycaulus decreased by 84 % with 4 g C kg-1 amendment. After 7 years, the addition of humic amendment resulted in a cover of over 38 % for M. sativa, compared to less than 2 % in control plots. In addition, non-seeded species cover increased with amendment rate in the 2003 experiment but not the 2004 experiment, most likely due to lower pH in the latter. Our results suggest that short-term patterns of plant performance do not reflect longer-term performance or invasion by volunteer plant species. Our long-term data suggest that humic amendments can be effective in establishing plant invasion of mine tailings, although the effects vary depending on the pH of the tailings. © 2013 Springer Science+Business Media Dordrecht.

The concentration of a range of endocrine disruptors: 17-β-estradiol, estrone, 17-α-ethinylestradiol, bisphenol-A, pentachlorophenol, triclosan, and butylbenzylphthalate, was analyzed by gas chromatography/mass spectrometry in the Wetland zone of Xochimilco, a periurban area of Mexico City, during an annual cycle. Samples were taken based on their level of use and by selecting sampling points related with activities such as agriculture, livestock, and urban, as well as their potential presence in water at the Cerro de la Estrella Wastewater Treatment Plant (WWTP) which supplies the majority of water (>90 %) to the study area. The compounds analyzed are present in a wide range of products from cosmetics to home care, pharmaceuticals, and subproducts of the food industry. The importance of identifying these compounds lies in the fact that they can disrupt the endocrine system of vertebrates, in particular reproductive gland function, affecting the development of organisms and their offspring. Pentachlorophenol, triclosan, bisphenol-A, butylbenzylphthalate, estrone, and 17-β-estradiol were detected in concentrations in nanogram-per-liter levels; 17-α-ethinylestradiol was always below the detection limit. The compounds showed a trend toward greater concentrations in the rainy season, probably due to the runoff that carries these compounds into the system.

The connection between hydrocarbon biodegradation and surface-active substance production has attracted great interest in recent years. Pseudomonas fluorescens PT, isolated from a biotrickling filter, was not only able to degrade α-pinene but also to use it as a carbon source to produce a surface-active substance. Response surface methodology analysis showed that the optimal medium composition was K⁺, 69.8; Mn²⁺, 65.1; and NH₄ ⁺, 482.5 mg L⁻¹, at which the surface tension of the medium was reduced to 40.7 mN m⁻¹ after 36 h. Based on compositional analysis and information on α-pinene metabolism, the purified compound was identified as perilla acid. The surface-active properties of the purified compound were more stable than those of a synthetic surfactant, and it had lower ecological toxicity to Chlorella vulgaris. The naphthalene solubility and mass transfer of α-pinene were enhanced almost twofold by the surface-active substance (at its critical micelle concentration). The results suggested that the PT strain may be promising for generating surface-active substances with improved physiochemical properties for a wide range of applications in environmental remediation.

The environmental impact assessment of mining sites represents nowadays a large interest topic in Romania. Historical pollution in the Rosia Montana mining area of Romania caused extensive damage to environmental media. This paper has two goals: to investigate the environmental pollution induced by mining activities in the Rosia Montana area and to quantify the environmental impacts and associated risks by means of an integrated approach. Thus, a new method was developed and applied for quantifying the impact of mining activities, taking account of the quality of environmental media in the mining area, and used as case study in the present paper. The associated risks are a function of the environmental impacts and the probability of their occurrence. The results show that the environmental impacts and quantified risks, based on quality indicators to characterize the environmental quality, are of a higher order, and thus measures for pollution remediation and control need to be considered in the investigated area. The conclusion drawn is that an integrated approach for the assessment of environmental impact and associated risks is a valuable and more objective method, and is an important tool that can be applied in the decision-making process for national authorities in the prioritization of emergency action.