Over a century of metal processing activity has resulted in widespread metal contamination of soils in Sudbury, ON, Canada. To assess the potential for recovery from the large reductions in metal deposition, critical loads were estimated for metals at 415 sites in Sudbury using an ‘effects based’ approach that is based on exceedance of provincial soil guidelines using multiple independent estimates of metal partitioning (Kd) for each metal. Sudbury soils are heavily contaminated with copper (Cu) and nickel (Ni), with 74 % of samples currently exceeding the provincial soil guideline for Cu and 87 % of samples exceeding the guideline for Ni. Both metals are strongly correlated with other metals (zinc (Zn), cadmium (Cd), lead (Pb)), although they rarely exceed provincial guidelines Copper and Ni are also strongly correlated with organic matter but not soil pH. Based on the most recent Cu and Ni deposition estimates (mid-1990s), it is estimated that between 20 % and 51 % of the sites receive deposition in excess of the ‘effects based’ critical load for Cu and between 5 % and 97 % of sites receive atmospheric deposition in excess of the ‘effects based’ critical load for Ni. These results suggest that Cu and Ni concentrations in soil will generally decrease resulting in slightly fewer sites that exceed the provincial soil guideline, but that the timeframe of this response will be very slow, with relatively little change occurring over the next 100 years. Even assuming a best case deposition scenario whereby Cu and Ni deposition were to immediately fall to background levels, the percentage of sites with Cu and Ni levels in excess of the OMOE guideline would still be between 69 % and 72 %, and 56 % and 86 %, respectively, demonstrating that while recovery of the Sudbury soils is possible, greater reductions in metal deposition are needed and even so, it will be a process that takes several centuries.

Titanium dioxide (TiO2)–silicon dioxide (SiO2) thin films were synthesized using the peroxo titanic acid approach (PTA) combined with the sol–gel method at low temperature around 100°C. The effects of type and amount of dopants of ferric (Fe3+) or thiourea (N-S) and co-dopants of Fe3+ and N-S on the films physicochemical properties and on the photocatalytic degradation of the methylene blue and formaldehyde under UV and visible light irradiation were investigated. Physicochemical properties of photocatalysts were characterized by X-ray diffraction, transmission electron microscopy, wavelength-dispersive X-ray fluorescence spectrometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and UV–Vis spectroscopy. The results showed that the TiO2 crystal phases obtained from this method were exclusively anatase and the needle-like crystals have an average diameter of 10–25 nm. Compared with the single dopant of 1.0 wt.% Fe3+ or 0.125 wt.% N-S that was the optimal concentration for photocatalytic degradation of methylene blue and formaldehyde, the co-dopants of 0.125 wt.% N-S + 1.0 wt.% Fe3+ furthermore increased the degradation efficiency. Co-dopants of 0.125 wt.% N-S + 1.0 wt.% Fe3+ in TiO2–SiO2 films were considered to play synergistic roles in narrowing TiO2 band gap resulting in the higher methylene blue and formaldehyde degradation efficiency. Since the crystal grain size of TiO2–SiO2 films synthesized by the PTA method is small, in the visible light region, the high transmittance was attainable to 80% with no-doped and dropped to 50–60% with doped thin films.

Bacterial cells that enter the groundwater system commonly experience desiccation stresses (i.e., bacterial cells are directly exposed to air) when traveling through the unsaturated layer of soil. Little is known about the effects of desiccation on the transport of bacterial cells in the groundwater system. In this research, we investigated the transport of desiccated and non-desiccated Escherichia coli K12 (ATCC 10798) cells through saturated sand packs using laboratory column transport experiments. Cell desiccation was performed at 25°C under relative humidity (RH) levels of 22%, 53%, 75%, and 97%, respectively, and the desiccation duration was 22 h. Our results showed that desiccation reduced the viability of E. coli cells under all RH levels and increased the transport of E. coli cells under ≥75% RH levels. The increase in the transport of the desiccated E. coli cells was not related to changes in cell size or cell zeta potential. Desiccation under high (i.e., ≥75%) RH levels, however, led to lower cell hydrophobicity, which was found to be positively correlated with cell transport.

The upper limit of fluoride concentration in water for human consumption is 1.5 ppm. Many studies have been carried out concerning the water fluoride concentration in wide areas around the world, but none have studied the change of fluoride concentration as a function of geographical coordinates and through time. This paper describes ‘microvariation’ of fluoride concentration among wells separated by less than 500 m in a month. On the other hand, ‘macrovariation’ is also studied describing changes among cities that are separated by more than 10 km and compared with fluoride concentrations measured 65 years ago. Fluoride concentration was measured in a wide geographical area of Argentina, which is 133,000 km². Samples of water were collected from different regions. Macrovariation: Differences in fluoride concentration in well water among regions were found, as well as an increase in water fluoride concentration during seven decades. Microvariation: Daily water fluoride concentration in a specific area displayed a great variation in the measurements through time. In addition, wells with no more than 500 m of separation were measured at the same time and were significantly different. These results indicate that in order to determine the fluoride concentration of a region, different samples of the same area should be obtained and a sampling through time should also be done.

In domestic wastewater, bacterial physiology controls cell production (growth, replication) and cell maintenance, determining how energy is allocated between these two processes. The aim here was to develop a method to quantify these cellular processes so that the bacterial physiological state could be manipulated to lower this source of pollution. We simultaneously used the incorporation of radiolabelled thymidine into DNA (a measure of new cell synthesis) and leucine into protein in wastewater to quantitatively distinguish bacterial growth from maintenance processes. We found that DNA and protein syntheses were coupled in wastewater after substrate enrichment (with glucose or acetate)—balanced growth. Once the substrate was depleted, the two processes became uncoupled—unbalanced growth. In this physiological state, the bacteria were synthesising protein, but fewer bacteria were replicating. More energy was allocated to cell maintenance than replication. A mean Leu/TdR ratio of 7.4 was determined for wastewater and was similar to natural aquatic ecosystems. As the bacterial growth rate decreased, the Leu/TdR ratios increased. We show how the simultaneous measurement of [³H]Leu and [³H]TdR quantitatively distinguishes balanced from unbalanced growth. Low [³H]Leu/[³H]TdR ratios indicated bacteria were physiologically stressed, an ideal state for biological wastewater treatment processes (WWTP) as the bacteria divert more energy to maintenance activities instead of growth. Leu/TdR ratios of 70 have been recorded in natural aquatic ecosystems which suggests WWTP have potential to be manipulated to achieve much higher Leu/TdR ratios than we report here. Changes to plant operation to improve operation efficiency include finding the optimum rate of substrate (pollution supply) or alternating aerobic and anaerobic periods to maximise the Leu/TdR ratio to achieve less biomass production for land disposal and more cost-effective operation that generates less pollution in the effluent.

Alberta’s oil sands are located in the boreal forest where surface mining requires reconstruction of these landscapes using waste saline and sodic overburden (SSOB) piles. The impact of these SSOB materials, however, on root development of planted boreal species is unknown. The objective of this study was to examine the effect of SSOB material on the root distributions of planted boreal species. Root distributions for planted mixedwood stands were measured using soil cores and compared with soil physical and chemical properties on three reclaimed sites. Soil pH ranged from 6.1 to 7.5 across all three reclaimed sites. Sodium adsorption ratio ranged from <30 in the SSOB at the youngest site to <4 at the oldest site while soil electrical conductivity ranged from <12 and <4 dS m−1 in the SSOB at the youngest and oldest site, respectively. Root length distributions were concentrated in the upper 30 cm of the soil profile and ranged from 0.96 to 7.99 cm cm−3. The roots were observed in the SSOB and accounted for 1.3% to 2.2% of the total root length in the profile. The root length density was also negatively correlated with Na and EC at all sites. The root distributions on these young reclaimed sites were similar to those from undisturbed boreal forest stands overlying saline soils, suggesting that root distributions on these reclaimed sites appear to be unaffected by the SSOB; however, further monitoring will be required as the stand matures to determine future impacts of the SSOB on forest productivity.

Selenium (Se) contamination of aquatic habitats is a global environmental issue. Although organic forms of Se are thought to represent the most bioavailable forms of Se, elevated concentrations of inorganic Se can cause toxicity in aquatic organisms such as benthic invertebrates. To assess the potential role of Se in mortalities observed during previous in situ invertebrate exposures, laboratory experiments on toxicity of inorganic Se (selenate) to Hyalella azteca were performed. Both a laboratory-reared and a field-collected H. azteca population were exposed to Se concentrations ranging from near 0 (control) to 21.79 mg/L, and survival of exposed individuals was monitored over 10 days. In the laboratory-reared H. azteca, significant changes in mortality pattern and reductions in mean survival time (MST) were noted in the test groups exposed to ≥0.164 mg/L Se. In the field-collected animals however, significant changes in mortality pattern and reductions in MST were measured in H. azteca exposed to ≥1.43 mg/L Se. The 10-day LC50s were 0.086 and 0.574 mg Se/L for the laboratory and field-collected H. azteca populations, respectively. The laboratory-reared group thus was about one order of magnitude more sensitive to Se exposure than the field-collected amphipods. Our results suggest that Se toxicity was likely not a major contributor to amphipod mortalities observed in earlier field studies. Furthermore, population-specific tolerances of the test organisms may need to be considered when extrapolating laboratory-generated data to field situations.

The number of Enterobacteriaceae, with particular attention given to the presence of Escherichia coli and Klebsiella pneumoniae, was determined in hospital effluents and municipal wastewater after various stages of purification. The emission of these microorganisms to the ambient air near wastewater treatment plant (WWTP) facilities and to the river water, which is a receiver of the WWTP effluent, was also studied using fluorescence in situ hybridization (FISH) and cultivation methods. The number of Enterobacteriaceae determined by cultivation and fluorescence methods in different kinds of sewage sample ranged from 0.5 × 10³ to 2.9 × 10⁶ CFU/ml and from 2.2 × 10⁵ to 1.3 × 10⁸ cells/ml, respectively. Their removal rates during treatment processes were close to 99 %, but the number of these bacteria in the WWTP outflow was quite high and ranged from 5.9 × 10³ to 3.5 × 10⁴ CFU/ml and from 1.1 × 10⁵ to 6.1 × 10⁵ cells/ml, respectively. In the river water and the air samples, the number of Enterobacteriaceae was also high and ranged from 4.1 × 10³ to 7.9 × 10³ CFU/ml and from 3 to 458 CFU/m³, respectively. The numbers of these microorganisms obtained from fluorescence and cultivation methods were statistically and significantly correlated; however, the analysis of the studied samples indicated that the FISH method gave values up to 10³-fold times greater than those obtained by the cultivation method. From a sanitary point of view, this means that the number of viable fecal bacteria is systematically underestimated by traditional culture-based methods. Thus, the FISH proves to be a method that could be used to estimate bacterial load, particularly in air samples and less contaminated river water.

The aim of this study is to assess the premature mortality risks caused by exposure to particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5) and ozone elevated concentrations for the years 2000, 2005, and 2020 in East Asia. The spatial distributions and temporal variations of PM2.5 and ozone concentrations are simulated using the Models-3 Community Multiscale Air Quality Modeling System coupled with the Regional Emission Inventory in Asia. The premature mortality risks caused by exposure to PM2.5 and ozone are calculated based on a relative risk (RR) value of 1.04 (95 % confidence interval (CI): 1.01–1.08) for PM2.5 concentrations above the annual mean limit of 10 μg m−3 taken from the World Health Organization–Air Quality Guideline and based on a RR value of 1.003 (95 % CI: 1.001–1.004) for ozone concentration above 35 ppb of the SOMO35 index (the sum of ozone daily maximum 8-h mean concentrations above 35 ppb). We demonstrate one of the implications of the policy making in the area of environmental atmospheric management in East Asia by highlighting the annual premature mortalities associated with exposure to PM2.5 concentrations that just meet an annual mean concentration of 10 μg m−3, as well as ozone concentrations that have a daily zero SOMO35 index in vulnerable places. Our results point to a growing health risk that may endanger human life in East Asia. We find that the effect of PM2.5 on human health is greater than the effect of ozone for the age group of 30 years and above. We estimate the corresponding premature mortality due to the effects of both ozone and PM2.5 in East Asia for the years 2000 and 2005 to be around 316,000 and 520,000 cases, respectively. For future scenarios of the year 2020, policy succeed case, reference, and policy failed case, the estimated annual premature mortality rates are 451,000, 649,000, and 1,035,000 respectively.

Electrical resistivity tomography (2D ERT) is a powerful tool for the diagnosis of the subsoil state and to pursue an environmental monitoring in time to detect and follow a temporal evolution of plumes in hydrocarbon-contaminated soils. In situ, 2D ERT was conducted to investigate the electrical properties of the subsoil in three petrol stations in Murcia semiarid Region (SE Spain), which have been active for many years, in order to look for anomalous areas that could be related to the presence of a non-aqueous phase liquid (NAPL) contaminant plume in the subsoil. A total of 18 ERT profiles in wet and dry season were conducted to study the seasonal effects in the resistivity values of the subsoil. Dipole–dipole array was set up to make the soil diagnosis, achieving a good vertical and lateral resistivity distributions for the sites investigated. Interpretations obtained from ERT pseudo-sections, after a processing and inversion data process with PROSYS II and RES2DINV software, show delimited highly resistive regions above 2,000 Ω·m at 2 m deep related to the underground storage tanks (USTs) position and the filling ports and anomalous resistivity areas where boreholes and further GC–FID determination in soil samples have been done. No significant differences have been found between results obtained in dry and wet seasons. Thus, the geo-electrical non-destructive technique ERT is presented as a tool to delineate the USTs positions and to point out anomaly in the subsoil that could contain NAPL, helping to design sampling strategies, saving cost and time.