Oxygenated gasoline release in the unsaturated zone, Part 2: Downgradient transport of ethanol and hydrocarbons

In the event of a gasoline spill containing oxygenated compounds such as ethanol and MTBE, it is important to consider the impacts these compounds might have on subsurface contamination. One of the main concerns commonly associated with ethanol is that it might decrease the biodegradation of aromatic hydrocarbon compounds, leading to an increase in the hydrocarbon dissolved plume lengths. The first part of this study (Part 1) showed that when gasoline containing ethanol infiltrates the unsaturated zone, ethanol is likely to partition to and be retained in the unsaturated zone pore water. In this study (Part 2), a controlled field test is combined with a two-dimensional laboratory test and three-dimensional numerical modelling to investigate how ethanol retention in the unsaturated zone affects the downgradient behaviour of ethanol and aromatic hydrocarbon compounds. Ethanol transport downgradient was extremely limited. The appearance of ethanol in downgradient wells was delayed and the concentrations were lower than would be expected based on equilibrium dissolution. Oscillations in the water table resulted in minor flushing of ethanol, but its effect could still be perceived as an increase in the groundwater concentrations downgradient from the source zone. Ethanol partitioning to the unsaturated zone pore water reduced its mass fraction within the NAPL thus reducing its anticipated impact on the fate of the hydrocarbon compounds. A conceptual numerical simulation indicated that the potential ethanol-induced increase in benzene plume length after 20 years could decrease from 136% to 40% when ethanol retention in the unsaturated zone is considered.     

Youth and sustainable waste management: a SEM approach and extended theory of planned behavior

The present study aims to develop the Theory of Planned Behavior (TPB) to explain comprehensively the establishment of intention and behavior toward source separation of waste. The extended TPB involves the significant structures affecting the behavior along with the original variables of TPB model. Data were gathered from 420 students in Ferdowsi University, Iran, using questionnaires, and analyzed by cluster analysis, discriminant analysis and structural equation modelling techniques (SEM). The cluster analysis identified three distinct grouping according to TPB constructs, and it was validated by discriminant analysis. SEM results displays that motivation had the most important impact on intention, followed by moral obligation, perceived behavior control, subjective norm, situational factor and attitude. Fit statistic of the extended TPB model was good and had better explanatory power compared to the original TPB. It describes 81 and 57% of the variance for intention and behavior toward source separation waste, respectively.     

Health risk assessment of inhalation exposure to dry fogging of hydrogen peroxide in a dental clinic during the COVID-19 pandemic

Environmental Science and Pollution Research - After the outbreak of COVID-19, many dental clinics use dry fogging of hydrogen peroxide (H2O2) to disinfect the air and surfaces. Inhalation of...     

Porous materials for the recovery of rare earth elements,platinum group metals,and other valuable metals: a review

Environmental Chemistry Letters - The demand for valuable metals such as rare earth elements and platinum group metals is rising fast in the context of the depletion of natural resources...