Modeling the natural attenuation of benzene in groundwater impacted by ethanol-blended fuels: Effect of ethanol content on the lifespan and maximum length of benzene plumes

© 2009 American Geophysical Union (AGU)A numerical model was used to evaluate how the concentration of ethanol in reformulated gasoline affects the length and longevity of benzene plumes in fuel-contaminated groundwater. Simulations considered a decaying light nonaqueous phase liquid source with a total mass of ∼85 kg and a groundwater seepage velocity of 9 cm d−1 and corroborated previous laboratory, field, and modeling studies showing benzene plume elongation due to the presence of ethanol. Benzene plume elongation reached a maximum of 59% for 20% ethanol content (E20) relative to regular gasoline without ethanol. Elongation was due to accelerated depletion of dissolved oxygen during ethanol degradation and to a lower specific rate of benzene utilization caused by metabolic flux dilution and catabolite repression. The lifespan of benzene plumes was shorter for all ethanol blends compared to regular gasoline (e.g., 17 years for regular gasoline, 15 years for E10, 9 years for E50, and 3 years for E85), indicating greater natural attenuation potential for higher-ethanol blends. This was attributed to a lower mass of benzene released for higher-ethanol blends and increased microbial activity associated with fortuitous growth of benzene degraders on ethanol. Whereas site-specific conditions will determine actual benzene plume length and longevity, these decaying-source simulations imply that high-ethanol blends (e.g., E85) pose a lower risk of benzene reaching a receptor via groundwater migration than low-ethanol blends such as E10

Degradation of a benzene–toluene mixture by hydrocarbon-adapted bacterial communities

We examined the rate of degradation of a benzene–toluene mixture in aerobic microcosms prepared with samples of an aquifer that lies below a petrochemical plant (SIReN, UK). Five samples exposed to different concentrations of benzene (from 0.6 to 317 mg l−1) were used. Fast degradation (approx. 1–6 mg l−1 day−1) of both contaminants was observed in all groundwater samples and complete degradation was recorded by the seventh day except for one sample. We also identified the microbial community in each of the samples by culture-independent techniques. Two of the less impacted samples harbour the aerobic benzene degrader Pseudomonas fluorescens, while Acidovorax and Arthrobacter spp. were found in the most polluted sample and are consistent with the population observed in situ. Hydrogenophaga was found in the deepest sample while Rhodoferax spp. were recovered in an alkaline sample (pH 8.4) and may also be implicated in benzene degradation. Time series analysis shows that each of the samples has a different community but they remain stable over the degradation period. This study provides new information on a well not previously studied (no. 309s) and confirms that adapted communities have the ability to degrade hydrocarbon mixtures and could be used in further bioaugmentation approaches in contaminated sites

Toward a comprehensive strategy to mitigate dissemination of environmental sources of antibiotic resistance

202205 bckwAccepted ManuscriptRGCOthersU.S. National Science Foundation; Overseas Environmental Antibiotic Resistance Surveillance - OVERSEAS, FLAD/NSFPublishe

C-60 aminofullerene-magnetite nanocomposite designed for efficient visible light photocatalysis and magnetic recovery

A magnetically recyclable photosensitizing system for harnessing solar energy for water treatment and disinfection is reported. This system comprises C-60 aminofullerene as a sensitizer for singlet oxygenation and functionalized mesoporous silica (msu-f SiO2) encapsulating magnetite nanoparticles (msu-SiO2/mag) as a magnetically separable host. Rapid degradation of furfuryl alcohol (FFA) (a singlet oxygen (O-1(2)) probe) under visible-light irradiation along with the kinetic retardation of FFA decomposition in the presence of O-1(2) quenchers suggests that the visible-light activity of C-60 aminofullerene-derivatized msu-SiO2/mag (C-60/msu-SiO2/mag) is related to the photosensitization of O-1(2). On the other hand, the use of SiO2 gel and fumed SiO2 as magnetic supports drastically reduced the photosensitized generation of O-1(2), which is ascribed to the absence of an ordered pore structure in the alternative silica support, resulting in an uncontrolled growth of Fe3O4 and an aggregation of the fullerenes on the SiO2 gel and fumed SiO2. Significant O-1(2) production using C-60/msu-SiO2/mag led to the effective oxidation of emerging pharmaceutical contaminants and inactivation of MS-2 bacteriophage under visible-light irradiation. Magnetic recovery and the subsequent reuse of the composite did not cause any significant loss in the photosensitizing activity of C-60/msu-SiO2/mag, demonstrating its potential for catalytic applications. (C) 2013 Elsevier Ltd. All rights reserved.X111312sciescopu

Selective Oxidative Degradation of Organic Pollutants by Singlet Oxygen-Mediated Photosensitization: Tin Porphyrin versus C-60 Aminofullerene Systems

This study evaluates the potential application of tin porphyrin- and C-60 aminofullerene-derivatized silica (SnP/silica and aminoC(60)/silica) as O-1(2) generating systems for photochemical degradation of organic pollutants. Photosensitized O-1(2) production with SnP/silica, which was faster than with aminoC(60)/silica, effectively oxidized a variety of pharmaceuticals. Significant degradation of pharmaceuticals in the presence of the 400-nm UV cutoff filter corroborated visible light activation of both photosensitizers. Whereas the efficacy of aminoC(60)/silica for O-1(2) production drastically decreased under irradiation with lambda > 550 nm, Q-band absorption caused negligible loss of the photosensitizing activity of SnP/silica in the long wavelength region. Faster destruction of phenolates by SnP/silica and aminoC60/silica under alkaline pH conditions further implicated O-1(2) involvement in the oxidative degradation. Direct charge transfer mediated by SO, which was inferred from nanosecond laser flash photolysis, induced significant degradation of neutral phenols under high power light irradiation. Self-sensitized destruction caused gradual activity loss of SnP/silica in reuse tests unlike aminoC(60)/silica. The kinetic comparison of SnP/silica and TiO2 photocatalyst in real wastewater effluents showed that photosensitized singlet oxygenation of pharmaceuticals was still efficiently achieved in the presence of background organic matters, while significant interference was observed for photocatalyzed oxidation involving non-selective OH radical.X117460sciescopu