1,721,021 research outputs found
Remote sensing-derived land surface temperature trends over South Asia
Full text linkSpatiotemporal changes in land surface temperature (LST) over South Asia were estimated using MODIS (moderate resolution imaging spectroradiometer) data from 2000 to 2021. We calculated the monthly and annual LST trends and magnitudes by applying the Mann–Kendall test and Sen's slope estimator at both ecoregion and pixel level. More ecoregions experienced daytime cooling than warming. Central and west South Asia showed the highest daytime cooling in December compared to the nighttime warming in the central and northwest in July and September. Nineteen ecoregions demonstrated monthly daytime cooling trends at the 99% confidence level (CL), with the highest record observed in ecoregion ‘Indus Valley desert’ in March with the magnitudes of −0.26 °C/yr. While the monthly and annual nighttime warming magnitude was the maximum in ‘Gissaro-Alai open woodlands’ in December (0.19 °C/yr at 95% CL), and ‘Indus River Delta-Arabian Sea mangroves’ at annual scale (0.06 °C/yr at 99% CL). To understand the influence of large-scale atmospheric oscillations on the trends, we also correlated the estimated LST trends with the selected oscillation indices. Sea surface temperature (SST) Niño 3.4 showed the most significant influence on the trends, where it was positively correlated with 38 ecoregions during nighttime over the year. A better understanding of temperature trends and impacts on South Asia would guide sustainable development and ensures the excessive demands on food, water, and energy supplies coping with the growing population
A Decision Support System for Risk Management of Contaminated Sites
No full textBibliography: p. 240-26
An investigation of a photochemical approach for the remediation of PCB-contaminated soils
No full textBibliography: p. 248-26
Pulsed Injection System for Enhanced Treatment Delivery of In Situ Soil and Groundwater Remediation Systems
No full textAn area within in situ remediation technologies that continues to present challenges is the method used for delivery of chemical treatments (e.g. oxidants). This study observes the effects of combining the methods of two different delivery systems under similar geological conditions in both field and laboratory settings. The objective of this study is the comparison of the effects of a direct push liquid injection treatment with a pulsing injection system.
The results of both the field-level and laboratory testing suggested that the pulsed injection technology was more effective in delivering treatments into the subsurface and enabling a longer horizontal transport distance
Evaluating Emerging Municipal Wastewater Treatment Technologies
No full textMunicipal wastewater treatment plants (WWTPs) are among the most energy-intensive systems and contributors to greenhouse gas (GHG) emissions, making them a critical focus for Canada’s net-zero transition. This study evaluates three emerging technologies: Anaerobic Membrane Bioreactors (AnMBR), Anaerobic Ammonium Oxidation (Anammox), and Thermal Hydrolysis with Anaerobic Digestion (THP + AD), in comparison to conventional systems. Using a comparative framework, energy balances, GHG emissions modeling, and policy alignment analysis were conducted to assess their potential for reducing carbon footprints, optimizing energy use, and supporting Canada’s climate goals. Results show while some emerging systems have higher operational energy demands, they achieve net energy recovery and significantly lower emissions when resource recovery pathways are considered. Policy analysis highlights the importance of financial incentives, regulatory amendments, and technical capacity support to accelerate adoption. The findings provide policymakers, utilities, and industry stakeholders with practical insights on advancing low-carbon wastewater treatment solutions aligned with Canada’s 2050 net-zero targets
Disinfection and Self-Sensitized Degradation of Natural Organic Matter (NOM) by TiO2 Photocatalysis with Visible light
No full textThe reaction of natural organic matter (NOM) with chlorine results in formation of disinfection by products (DBPs), known carcinogens. Fulvic acid (FA), a key component of NOM is likely a precursor to DBPs. Photocatalytic advanced oxidation using TiO2 is efficient under UV irradiation and known to degrade humics with reduction of DBPs. However, TiO2 may be dye “sensitized” for visible light, where the dye excited state transfers an electron to TiO2 conduction band. NOM adsorbs on the surface of TiO2 and sensitizes (“self-sensitization”). NOM undergoes an initial oxidative step upon visible light absorption and transfers an electron to the TiO2 conduction band. Oxygen captures the electron, forming superoxide which can aid in degradation of NOM. Model studies with Suwannee river fulvic acid are reported and then extended to “real water samples” from Southern Alberta. The humic model shows different degradation behavior from ‘real’ samples. In addition to reduction of NOM by “self-sensitization”, the active species also achieve reduction of Total coliform and Escherichia coli. The objective of this research is to treat NOM and simultaneously enhance disinfection
Light Emitting Diode Based Photochemical Treatment of Contaminants in Aqueous Phase
No full textIn this research, photochemical treatment of pesticides and polychlorinated biphenyls (PCBs) in aqueous medium were investigated. The studies on photochemical treatment of these two groups of compounds, along with radiation field modelling, further, led to the design of an efficient light emitting diode (LED) based flow-through photocatalytic reactor.
Sensitized photodechlorination of PCBs in surfactant solutions was studied. Three types of surfactants at different concentrations were investigated. The neutral and cationic surfactants were found to be more effective than the anionic one. In each case the surfactant concentration was found to play a significant role in the rate of dechlorination.
LED based photocatalytic degradation of pesticides and chlorophenols, namely 2,4-dichlorophenoxyacetic acid (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA) , 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) was studied. Further, the impact of photocatalyst loading and light intensity on the degradation rate was evaluated. The degradation of 2,4-D under LED irradiation was compared to that with mercury discharge lamp irradiation. The results show these compounds can be efficiently degraded using LED based TiO2 photocatalysis. They are completely mineralized upon prolonged irradiation. Our results indicate that LEDs are a better light source than the mercury lamps.
To design an efficient LED based photocatalytic reactor, a radiation field model was developed in this research. The model was tested with experimental data and good agreement between two was noted. The model can be used to optimize the photoreactor and chose the optimal gap between adjacent LEDs, the irradiated distance and the light output of LEDs for a homogenous radiation field.
Finally, an LED based photocatalytic reactor was designed and fabricated. The reactor uses anodized TiO2 nanostructure as a photocatalyst. The performance of reactor was evaluated and optimized by studying the degradation of 2,4-D. The effect of different operational parameters on the reactor performance were investigated, including light intensity, distance between the LED module and photocatalytic plate (DL-P), the flow rate through the reactor, presence of external electron scavengers and photocatalyst configuration. A power law relationship was observed between the light intensity (2.2 mW cm-2~17.3 mW cm-2) and the first order degradation rate constant for 2,4-D. A suitable flow rate and D(L-P) was determined for the reactor. Enhanced performance of the reactor was observed where electron scavengers were introduced.2 year
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