Pentachlorophenol (PCP) has been used worldwide as a wood treatment agent and biocide. Its toxicity and extensive use have placed it among the most hazardous environmental pollutants. The response of a PCP-contaminated agricultural soil to the addition of solid urban waste compost and two exogenous Ascomycota fungal strains Byssochlamys nivea and Scopulariopsis brumptii was evaluated. The experiments were conducted in soil microcosms incubated for 28 days at 25 °C and 60 % moisture content. The depletion of PCP and the changes in biochemical soil properties (i.e. microbial biomass, soil respiration, dehydrogenase and fluorescein diacetate hydrolysis activities) were detected. The addition of PCP severely depressed some of the tested biochemical properties such as microbial biomass, dehydrogenase and fluorescein diacetate hydrolysis activities. By contrast, compost limited the negative effect of PCP on the dehydrogenase activity and soil respiration. When compost and fungal strains were contemporary present, a synergistic effect was observed with a reduction of more than 95 % of the extractable PCP after 28 days of incubation. No differences in PCP depletion resulted when fungi or compost were individually used. Our results indicate that many processes (i.e. microbial degradation and sorption to organic matter) likely occurred when PCP was added to the soil. The compost and the fungal strains, B. nivea and S. brumptii, showed good capability to tolerate and degrade PCP so that they could be successfully used in synergistic effect to treat PCP polluted soils.

Long-term fire retardant (LTR) use for forest fire suppression and/or prevention purposes can result in chemical leaching, from soil to the drainage water, during the annual rainfall period. Also, wildland fires can have an impact on the leaching of various chemicals from treated forest soils. Large quantities of ions in leachates, mainly due to ammonium (one of the major LTR components) soil deposition, could affect the groundwater quality. The alteration of pH, total hardness (TH), and electrical conductivity (EC) values in leachates mainly due to nitrogen-based LTR application (Fire Trol 931) was investigated in this laboratory study. The values of pH, TH, and EC were measured in the resulting leachates from pots with forest soil and pine trees alone and in combination with fire after a simulated rainfall period. pH, TH, and EC values in leachates from all treated pots were significantly greater than those from control pots.

Soil metal contamination represents serious threats to plant ecosystem sustainability. Knowledge of metal distribution in plants and the effects of long-term exposure to high levels of metals on cytological stability in Deschampsia cespitosa and Populus tremuloides population is limited. The objective of the present study was to determine how D. cespitosa and P. tremuloides plants cope with soil metal contamination. The effects of high copper (Cu) and nickel (Ni) soil concentrations on cytological stability were also analyzed. The results provide strong evidence that D. cespitosa plants cope with metal contaminations by accumulating them in their root system with limited translocation to their aerial plant parts. Metal bioaccumulation factors were high with values of 5.53 (Cu), 35.19 (Fe), 151.21 (Mg), 24.38 (Ni), and 27.42 (Zn). On the other hand, the bioaccumulation factors in P. tremuloides were 0.42 (Cu), 1.67 (Fe), 4.77 (Mg), 0.94 (Ni), and 5.53 (Zn). The translocation factors (TFs) from roots to leaves for poplar (P. tremuloides) were high for Ni (8.38) and low for Cu (0.71). Cytological analysis clearly showed that long exposure of roots to high levels of metal contamination lead to significant mitotic disruption. Overall, 100 % of the plants from metal-contaminated sites showed a high level of mixoploidy compared to 17 % from the reference sites. Lagging chromosomes in mitotic anaphase were observed in most of the plants from metal-contaminated sites. These mitotic abnormalities appear to have no detectable effects on plant growth and survival.

Malathion is an organophosphate insecticide registered for use in cities throughout North America to control adult mosquitoes. The objective of this study was to determine the impact of urban malathion applications on the levels of malathion detected in bulk deposition. In 2010, malathion was applied by the City of Winnipeg’s Insect Control Branch for a total amount of 6632 kg in the city, as well as by the general public in relatively small amounts. In 2011, no malathion was applied by the city. Malathion was detected in 41 % of the samples in 2010 with deposition rates ranging from 0.5 to 107.7 μg/m²/week. Only 9 % of the samples contained malathion in 2011 with deposition rates always being <0.4 μg/m²/week. Between 6 and 25 % of the samples in 2010 exceeded the toxicological threshold levels of malathion to a range of freshwater amphipods, water fleas, and stoneflies, including Daphnia magna which is a bioindicator of good environmental health. The weekly maximum malathion concentration detected in this study (5.2 μg/L for a week in June 2010) was at least 26 times greater than the maximum concentration of malathion reported in other atmospheric deposition studies. For the two insect management areas (7.4 and 37.6 km²) where the bulk deposition samplers had been placed, calculations suggested that between 1.2 and 5.1 % of the malathion applied by the city became bulk deposition. Percutaneous absorption by humans of malathion in rainfall is unknown.

The performance of a laboratory-scale biofilter packed with a mixture of compost and woodchip on formaldehyde removal from polluted air streams was investigated. The reactor was inoculated with aerobic sludge as a source of bacteria, obtained from a municipal wastewater treatment plant. A nutrient solution was daily added to the reactor media. An airflow containing different concentrations of formaldehyde (from 20 ± 2 to 276 ± 5 mg m⁻³) was introduced into the reactor. In inlet formaldehyde concentration, an average removal efficiency and elimination capacity of 91 % and 0.36 g m⁻³ h⁻¹were attained, respectively, at180 s empty bed residence time (EBRT). After acclimatization of the system for increased formaldehyde concentrations of up to 276 ± 5 mg m⁻³and for EBRT of 180 s, those values were stabilized at around 72 % and 3.98g⁻³ h⁻¹, respectively. The experimental results showed that the system was effective for a high loading rate of formaldehyde with an acceptable EBRT. Compared to the application of compost alone as a media, a mixture of compost and woodchip (50/50 v/v%) enhanced the performance of the biofilter. The most predominant microorganism involved in the biodegradation of formaldehyde was a species of citrobacter called Citrobacter freundii, an aerobic gram-negative bacillus. Pressure drop of the reactor over the entire operations was about 1 mmH₂O m⁻¹.

Soil salinization is a worldwide problem of which secondary salinization is increasingly more frequent, threatening agricultural production. Salt accumulation affects not only plants but also the physio-chemical characteristics of the soil, limiting its potential use. Climate change will further increase the rate of salinization of soil and groundwater as it leads to increased evaporation, promotes capillary rise of saline groundwater as well as increased irrigation with brackish water. Episodic seawater inundation of coastal areas is likely to increase in frequency as well. This work analyzed three types of salinization: seawater inundation (by irrigating soils with a 54 dS m⁻¹NaCl solution), saline groundwater capillary rise (soil contact with a 27 dS m⁻¹NaCl solution), and irrigation with two types of brackish water with different residual sodium carbonate (RSC). Two soils were used: a mineral soil (7.0 % clay; 0.7 % organic matter) and an organic soil (2.7 % clay; 7.4 % organic matter). The tested soils had different resilience to salinization: The mineral soil had higher sodium adsorption ratio (SAR) due to low levels of calcium + magnesium but had higher leaching efficiency and more limited effects of RSC. The organic soil however was more prone to capillary rise but seemingly more structurally stable. Our results suggest that short-term inundation with seawater can be mitigated by leaching although soil structure may be affected and that capillary rise of brackish groundwater should be carefully monitored. Also, the impact of irrigation with brackish water with high RSC can be inferior in soils with higher exchangeable acidity.

Before and after an intense wildfire in a forested area of Colorado in June 2012, river water and sediment samples were collected to study temporal and spatial trends related to the event. Water quality and soil properties were disturbed by the fire, but the magnitude was relatively small without precipitation. After precipitation, in-stream total nitrogen and total phosphorus (TP) concentrations significantly increased in the upstream section located within 10 km of the burned area. Large amounts of particulate P associated with highly correlated total suspended solids were introduced to the upstream section. Along with significantly increased in-stream concentrations of soluble reactive P (SRP) and dissolved organic P (DOP) after rain events, SRP dominated dissolved P in the river replacing DOP that was the main dissolved species before the fire event. In the riverbank, TP load increased significantly after the fire, and silt-clay and organic matter mass concentrations increased after precipitation. Riverbed TP mass concentrations decreased due to a reduced sorption capacity leading to a considerable P release from the sediments. The results indicate that fire-released P species will impact the downstream area of the watershed for a considerable time period as the bank erosion-sorption-desorption cycles in the watershed adjust to the fire-related loading.

Metalaxyl, an important phenylamide fungicide, is widely used for controlling fungal diseases caused by pathogens of the orders Peronosporales and Pythiales. Under laboratory conditions, metalaxyl was applied to soil samples at the recommended field rate (1×FR) and double of recommended field rate (2×FR) for two and three times. Soil subsamples were taken at 0, 1, 3, 7, 14, 28, and 45 days after the last application of metalaxyl for determination of metalaxyl residues and 7, 14, 28, and 56 days for enumeration of cultivable microorganisms and DGGE profile of soil microbial community. Soil incubation experiments revealed that metalaxyl was degraded faster in the third application than in the second application of the fungicide, half-lives of metalaxyl decreasing from 16.2 to 9.9 days for recommended field rate and 22.1 to 20.0 days for double of recommended field rate. Soil bacterial and fungal populations decreased in the first 14 days and then recovered to the control levels; population of actinomycetes did not alter in the first 28 days but increased at the end of the experiment after the second application. However, after the third treatment, temporary increase in soil bacteria population, nonsignificant inhibition effect on fungal population, and obvious stimulation effect on actinomycetes number were observed. DGGE results showed that successive inputs of metalaxyl altered the bacterial community structure. There were differences in the persistence and effects of metalaxyl on microbial community between the second and the third metalaxyl treatments.

The current work reports on the degradation of glycerol aqueous solution via photocatalytic-Fenton technique. The CuFe₂O₄ photocatalyst was synthesized via sol-gel method and its physicochemical properties were characterized. The as-synthesized photocatalyst possessed Brunauer-Emmett-Teller (BET)-specific surface area of 104 m²/g. The large BET-specific surface area was also corroborated by the field-emission scanning electron microscopy (FESEM) images which showed porous morphology. In addition, the XRD pattern showed that the visible light-active component, CuFe₂O₄, was successfully formed with band gap energy of 1.58 eV determined from the UV-Vis diffuse reflectance spectroscopy. Significantly, it was determined from the blank run study that the visible light was an integral part of the photoreaction. Without the visible light irradiation, glycerol degradation was low (<4.0 %). In contrast, when visible light was present, the glycerol degradation improved markedly to attain 17.7 % after 4 h of visible light irradiation, even in the absence of CuFe₂O₄ photocatalyst. This can be attributed to splitting of H₂O₂ into hydroxyl (●OH) radical. In the presence of CuFe₂O₄ photocatalyst, the photocatalytic Fenton degradation of glycerol has further enhanced to record nearly 40.0 % degradation at a catalyst loading of 5.0 g/l. This has demonstrated that the CuFe₂O₄ was capable of generating additional hydroxyl radicals to attack the glycerol molecule. Moreover, this degradation kinetics can be captured by Langmuir-Hinshelwood model from which it was found that the adsorption constant related to H₂O₂ was significantly weaker compared to the adsorption constant of glycerol.

Calcium nitrate and a lanthanum-modified bentonite (Phoslock®) were investigated for their ability to control the release of phosphorus from contaminated sediment. Their effectiveness and mode of action were assessed using microcosm experiments by monitoring the variation of physiochemical parameters and phosphorus and nitrogen species over time following the treatment for 66 days. Phoslock® was more effective reducing phosphorus in overlaying water and controlling its release from sediment. Calcium nitrate improved redox condition at the sediment-water interface and temporally reduce phosphorus in overlaying water but phosphorus level returned back in a long run. Phosphorus fractionation suggested that Phoslock® converted mobile phosphorus to more stable species while calcium nitrate increased the fractions of mobile phosphorus species. Phoslock® generally showed no effect on nitrogen species. Whereas calcium nitrate temporally increased nitrate, nitrite, and ammonium concentrations but their concentrations quickly reduced likely due to the denitrification process. Results suggested that Phoslock® can be more effective in controlling the release of phosphorus from sediment than calcium nitrate. However, calcium nitrate can improve the redox condition at the sediment-water interface, which may provide other benefits such as stimulating biodegradation.