The potential risk of surface and groundwater contamination by the heavy metals and radionuclides leached from uranium waste-rock piles (UWRP) is a major environmental concern in the uranium-mining district of Northern Saskatchewan, Canada. The main objective of this study was to evaluate the nickel and uranium leaching behaviour in the UWRP lithological materials. In addition to the chemical characterization, these selected UWRP geomedia samples were also subjected to the sequential extraction procedure, availability test to quantify leaching potential and cumulative leaching test (CLT). Sequential extractions results demonstrated substantial observed differences in the Ni and U distribution patterns among various operationally defined geochemical fractions. A large fraction of total Ni concentration was associated with non-labile residual fraction while U was mainly present in the labile fractions. The observed labile Ni and U concentrations also remained relatively high in the gneissic basement materials and underlying organic-rich lake sediment. In case of basement materials, both Ni and U concentrations in solution with the first CLT fraction exceeds their maximum permissible levels in both surface and groundwater. Leaching test results confirmed that Ni and U leachability depends on their total content distribution in various solid phase fractions, and several geochemical processes are controlling the solubility of Ni and U geochemical phases in the UWRP. Our experimental data suggest the potential for a long-term risk to surface and groundwater contamination from these UWRP.

A laboratory-scale study was conducted to determine the removal efficiencies of nine contaminants from a tannery wastewater using a number of physicochemical processes. Coagulation–flocculation using bittern as coagulant, oxidation-utilizing ozone, and adsorption using activated carbon were applied separately and in different sequences. Jar tests were utilized to conduct the experimental work. Except for arsenic, the highest removal efficiencies were recorded when coagulation/flocculation was conducted on the alkalized samples using a bittern dose of 5 mL/L. Activated carbon adsorption improved removal efficiencies of several contaminants. The coagulation/flocculation–adsorption sequence using the optimum dose of 5 mL/L of bittern resulted in high removal efficiencies for total suspended solids (TSS) (97 % ± 1), apparent color (100 % ± 0), turbidity (97 % ± 1), total nitrogen (86 % ± 1), and chromium (100 % ± 0). On the other hand, the same sequence resulted in moderate removal efficiencies for chemical oxygen demand (COD) (72 % ± 7) and total phosphorus (74 % ± 5) and relatively low removals for biochemical oxygen demand (BOD) (55 % ± 10) and arsenic (42 % ± 14). The removal efficiencies for the different tested sequences demonstrated that each sequence did improve the removal efficiencies for most of the parameters tested and consequently, the quality of tannery effluent. However, no single optimum sequence was capable of attaining high removal efficiencies for all nine parameters.

Static granular bed reactor (SGBR) and upflow anaerobic sludge blanket (UASB) reactor were demonstrated at mesophilic condition for the treatment of pulp and paper mill wastewater. The hydraulic retention times (HRTs) were varied from 4 to 24 h following 29-day start-up period. The overall chemical oxygen demand (COD) removal efficiency of the SGBR was higher than the UASB during this study. At 4 h HRT, the COD removal was greater than 70 % for the SGBR and 60 % for the UASB. Biomass yield and volatile fatty acids concentration of SGBR were slightly less than UASB at organic loading rates ranging from 1.2 to 5.1 kg/m³/day. The results indicated that the SGBR system can be considered a viable alternative system for anaerobic treatment for pulp and paper wastewater.

Recent research on potential carcinogens in recreational waters has spawned public concerns about the long-term public health impacts of disinfectants used in pools. However, no attention has been given to the ecological and public health impacts of metal oxides in cosmetics and sunscreens within swimming pools where leisure activities occur. The discussion in this perspective focuses on the interaction between metal oxide nanoparticles released from swimmers into pools where algae is present, and the synergistic toxicological effects of pool algae adsorbed by metal oxide nanoparticles in the presence of disinfection byproducts in comparison to the absence of contaminants. This perspective will address research approaches to evaluating metal oxide nanoparticle impacts on pool algae, and the challenge of identifying the potential mechanisms leading to transformed algae.

A post-harvest experiment was conducted further to our previous greenhouse pot study on upland kangkong (Ipomoea aquatica Forsk.) and Alfred stonecrop (Sedum alfredii Hance) intercropping system in Cd-contaminated soil inoculated with arbuscular mycorrhizal (AM) fungi. Previously, four treatments were established in the intercropping experiment, including monoculture of kangkong (control), intercropping with stonecrop (IS), and IS plus inoculation with Glomus caledonium (IS+Gc) or Glomus versiforme (IS+Gv). Both kangkong and stonecrop plants were harvested after growing for 8 weeks. Then, the tested soils were reclaimed for growing post-harvest kangkong for 6 weeks. In the post-harvest experiment, there were no significant differences between the IS and control treatments, except for a significantly decreased (p<0.05) soil available P concentration with IS treatment. Compared with IS, both IS+Gc and IS+Gv significantly decreased (p<0.05) soil DTPA-extractable (phytoavailable) Cd concentrations, but not total Cd, by elevating soil pH, causing significantly lower (p<0.05) Cd concentrations in both the root and shoot of kangkong. In addition, both Gc and Gv significantly increased (p<0.05) soil acid phosphatase activities and available P concentrations and hence resulted in significantly higher (p<0.05) plant P acquisitions. However, only Gv significantly increased (p<0.05) kangkong yield, while Gc only significantly elevated (p<0.05) the shoot P concentration. It suggested that AM fungi have played key roles in Cd stabilization and P mobilization in the intercropping system, and such positive responses seemed to be sustainable and valuable in post-harvest soils.

Zamioculcas zamiifolia has the potential to reduce the concentration of benzene, toluene, ethylbenzene, and xylene (BTEX) from contaminated indoor air. It can remove all four pollutant gases. Benzene, toluene, ethylbenzene, and xylene uptake per unit area of Z. zamiifolia leaf were about 0.96 ± 0.01, 0.93 ± 0.02, 0.92 ± 0.02, and 0.86 ± 0.07 mmol m -2 at 72 h of exposure, respectively. The physicochemical properties of each BTEX may affect its removal. Benzene, a smaller molecule, is taken up by plants faster than toluene, ethylbenzene, and xylene. The toxicity of BTEX on plant leaves and roots was not found. The chlorophyll fluorescence measurement (F v/F m) showed no significantly difference between controlled and treated plants, indicating that a concentration of 20 ppm of each gas is not high enough to affect the photosynthesis of the plants. The ratio of stomata and cuticles showed that 80 % of benzene, 76 % of toluene, 75 % of ethylbenzene, and 73 % of xylene were removed by stomata pathways, while 20, 23, 25, and 26 % of them were removed by cuticles. The BTEX removal efficiency by well-watered Z. zamiifolia was involved with day stomata opening and night closing, while the BTEX removal efficiency by water-stressed Z. zamiifolia can occur both day and night at a slightly lower rate than well-watered plants. © 2013 Springer Science+Business Media Dordrecht.

Centrifugal mother liquid (CML) is one of the main sources of wastewater produced during the production of polyvinyl chloride in chlor-alkali industry. CML is a typical poorly biodegradable organic wastewater, containing many kinds of refractory pollutants. Specifically, it contains dissolved refractory polymers, especially polyvinyl alcohol (PVA), which can pass though the biotreatment processes and clog the membranes used for further treatment. In this study, to ensure the CML applicable to biotreatment and membrane treatment, a novel efficient and mild technique, air-Fenton treatment, was employed as a pretreatment technique to improve biodegradability of the CML and to break down the polymers in the CML. Firstly, the technique was optimized for the CML treatment by optimizing the main parameters, including the dosage of ferrous sulfate, initial pH of the wastewater, [H2O2]/[Fe(2+)], aeration rate, reaction time, and temperature, based on removal efficiency of COD and PVA from the CML. Then, the optimized technique was tested and evaluated. The results indicated that under the optimized conditions, the air-Fenton treatment could remove 66, 98, and 55 % of the COD, PVA, and TOC, respectively, from the CML. After the treatment, biodegradability of the wastewater increased significantly (BOD/COD increased from 0.31 to 0.68), and almost all of the PVA polymers were removed or broken down. Meanwhile, concentration of the remaining iron ions, which were added during the treatment, was also quite low (only 2.9 mg/L). Furthermore, most of the suspended materials and ammonia nitrogen, and some of the phosphorus in the wastewater were removed simultaneously.

Soil vapor extraction (SVE) is one of the most effective remediation technologies for soil and groundwater contamination. Soil particles can be mobilized by air perturbation during SVE, resulting in the differentiation of porous media, which has not been well addressed. This paper developed a numerical method to study the flow pattern and quantify the change of porous media for the first time. Based on the mass equilibrium and Darcy’s law, a two-phase water–air flow model was constructed with integration of saturation, relative permeability, and capillary pressure during SVE. Relationship between porosity and saturation was deduced and coupled with the two-phase flow model for quantifying change of porous media in real time. Results reveal that both porosity and permeability increase sharply in the early stage of SVE then gradually to a quasi-steady state. These increases in vadose zone tapered off with distance from the SVE screen and the steady period occurred later as well. The influence radius of a single SVE well and the change degree in porosity and permeability of media were proportional to the extraction vacuum and the driving coefficient C, which is more sensitive than extraction vacuum according to the simulation results. Knowledge from this modeling exercise provides a useful tool to estimate the change of remediated zone and assess the environmental risk of remedial activities at real-world contamination sites.

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.