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Pedro J. J. Alvarez

Bio: Pedro J. J. Alvarez is an academic researcher from Rice University. The author has contributed to research in topics: Bioremediation & Medicine. The author has an hindex of 89, co-authored 378 publications receiving 34837 citations. Previous affiliations of Pedro J. J. Alvarez include University of Minnesota & University of Michigan.


Papers
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Journal ArticleDOI
TL;DR: In this article, a mathematical model was developed to evaluate the effect of the common fuel additive ethanol on benzene fate and transport in fuel-contaminated groundwater and to discern the most influential benzene plume elongation mechanisms.
Abstract: [1] A mathematical model was developed to evaluate the effect of the common fuel additive ethanol on benzene fate and transport in fuel-contaminated groundwater and to discern the most influential benzene plume elongation mechanisms. The model, developed as a module for the Reactive Transport in 3 Dimensions (RT3D) model, includes commonly considered fate and transport processes (advection, dispersion, adsorption, biodegradation, and depletion of molecular oxygen during biodegradation) and substrate interactions previously not considered (e.g., a decrease in the specific benzene utilization rate due to metabolic flux dilution and/or catabolite repression) as well as microbial population shifts. Benzene plume elongation predictions, based on literature model parameters, were on the order of 40% for a constant source of E10 gasoline (10% vol/vol ethanol), which compares favorably to field observations. For low benzene concentrations (<1 mg/L), oxygen depletion during ethanol degradation was the principal mechanism hindering benzene natural attenuation. For higher benzene concentrations (exerting an oxygen demand higher than the available dissolved oxygen), metabolic flux dilution was the dominant plume elongation process. If oxygen were not limiting, as might be the case in zones undergoing aerobic biostimulation, model simulations showed that microbial growth on ethanol could offset negative substrate interactions and enhance benzene degradation, resulting in shorter plumes than baseline conditions without ethanol.

34 citations

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TL;DR: In this paper, real-time quantitative PCR (qPCR) was used to target the catabolic bssA gene and a 16S rDNA phylogenetic gene (for total Bacteria) as potential biomarkers to infer on anaerobic toluene degradation rates.
Abstract: The assessment of biodegradation activity in contaminated aquifers is critical to demonstrate the performance of bioremediation and natural attenuation and to parameterize models of contaminant plume dynamics. Real time quantitative PCR (qPCR) was used to target the catabolic bssA gene (coding for benzylsuccinate synthase) and a 16S rDNA phylogenetic gene (for total Bacteria) as potential biomarkers to infer on anaerobic toluene degradation rates. A significant correlation (P = 0.0003) was found over a wide range of initial toluene concentrations (1–100 mg/l) between toluene degradation rates and bssA concentrations in anaerobic microcosms prepared with aquifer material from a hydrocarbon contaminated site. In contrast, the correlation between toluene degradation activity and total Bacteria concentrations was not significant (P = 0.1125). This suggests that qPCR targeting of functional genes might offer a simple approach to estimate in situ biodegradation activity, which would enhance site investigation and modeling of natural attenuation at hydrocarbon-contaminated sites.

34 citations

01 Apr 2002
TL;DR: This literature review concludes that the proposed replacement of the gasoline oxygenate MTBE with ethanol represents potential economic and environmental quality benefits, but these benefits may be offset to some extent by potential detrimental effects on groundwater quality and natural attenuation of released petroleum products.
Abstract: The proposed replacement of the gasoline oxygenate MTBE with ethanol represents potential economic and environmental quality benefits. However, these benefits may be offset to some extent by potential detrimental effects on groundwater quality and natural attenuation of released petroleum products. The objectives of this literature review are to bound the extent to which these impacts may occur, summarize the available information on the biodegradation of ethanol in the environment, assess the potential effect that biodegradation processes may have on the fate and transport of BTEX compounds, and provide recommendations for research to enhance related risk assessment and management decisions. Ethanol that reaches groundwater aquifers is likely to be degraded at much faster rates than other gasoline constituents. If the carbon source is not limiting, a preferential degradation of ethanol over BTEX may be observed under both aerobic and anaerobic conditions. Depending on the extent of the release, ethanol may exert a high biochemical oxygen demand that would contribute to the rapid depletion of dissolved oxygen in the groundwater. Thus, ethanol will likely be degraded predominantly under anaerobic conditions. None of the potential ethanol metabolites that could accumulate in groundwater are toxic, although some potential biodegradation by-products such as butyrate could adversely affect the taste and odor of drinking water sources. In addition, acetate and other volatile fatty acids could accumulate at high concentrations, causing a pH decrease in poorly buffered systems. It is unknown, however, whether the pH would decrease to a point that inhibits natural degradative processes. Inhibition of microbial, activity near the source is likely to occur as a result of exposure to high alcohol concentrations, and bactericidal effects are likely to occur when cells are exposed to ethanol concentrations exceeding 10,000 mg/L. However, the maximum allowable ethanol content in gasoline is 10% by volume in the United States. Thus, such high ethanol concentrations are unlikely to be encountered at sites contaminated with ethanol-gasoline blends, except near the fuel/water interfaces or in the case of neat ethanol releases. Downgradient of the source area, biodegradation is unlikely to be inhibited by alcohol toxicity as concentrations decrease exponentially with distance. The preferential degradation of fuel alcohols by indigenous microorganisms and the accompanying depletion of oxygen and other electron acceptors suggest that ethanol could hinder BTEX bioremediation. This is particularly important for the fate of benzene, which is the most toxic BTEX compound and the most recalcitrant under anaerobic conditions. Alternatively, ethanol represents a carbon and energy source that is likely to stimulate the growth of a variety of aerobic and anaerobic microbial populations, including those that can degrade BTEX compounds. A higher concentration of BTEX degraders would be conducive to faster BTEX degradation rates under carbon-limiting conditions. Nevertheless, controlled studies that assess the overall effect of ethanol on BTEX bioremediation are lacking. In theory, ethanol could also contribute to longer BTEX plumes by enhancing BTEX solubilization from the fuel phase and by decreasing sorption-related retardation during transport. The overall effect of ethanol on BTEX plume length and treatment end points is likely to be system specific, and will depend largely on the release scenario and on the buffering and dilution capacity of the aquifer. Additional research is needed to understand the effect of ethanol on the stability and dimensions of co-occurring and pre-existing BTEX plumes. Future laboratory and field studies should also address response variability as a function of release scenario and site specificity, to facilitate risk assessment and remedial action decisions.

33 citations

Journal ArticleDOI
TL;DR: In this article, the binding energy of the C60−OH adduct as a function of C60 clustering degree was analyzed and the results imply that ordered clustering of C 60 in the aqueous phase significantly hinders C60s fundamental reactivity with radical species.
Abstract: Reactions of water-stable C60 clusters (nC60) in water with OH radicals (•OH) and hydrated electrons (eaq−), generated by steady-state γ-radiation, were observed and characterized. Ordered C60 clusters were relatively recalcitrant to highly reactive •OH and eaq− species, with only a fraction of carbons oxidized and reduced, respectively. Pulse radiolysis suggested that the reactions of nC60 with OH• and eaq− were diffusion limited, with rate constants of (7.34 ± 0.31) × 109 M−1 s−1 and (2.34 ± 0.02) × 1010 M−1 s−1, respectively. Quantum mechanical calculations of binding energy of the C60−OH adduct as a function of C60 clustering degree indicate, despite an initial fast reaction, a slower overall conversion due to thermodynamic instability of C60−OH intermediates. The results imply that ordered clustering of C60 in the aqueous phase significantly hinders C60’s fundamental reactivity with radical species.

33 citations

25 Sep 2018
TL;DR: This paper aims to demonstrate the efforts towards in-situ applicability of EMMARM, as to provide real-time information about the response of the immune system to EMTs.
Abstract: Bioremediation and Natural Attenuation , Bioremediation and Natural Attenuation , کتابخانه مرکزی دانشگاه علوم پزشکی ایران

32 citations


Cited by
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TL;DR: It is anticipated that this review can stimulate a new research doorway to facilitate the next generation of g-C3N4-based photocatalysts with ameliorated performances by harnessing the outstanding structural, electronic, and optical properties for the development of a sustainable future without environmental detriment.
Abstract: As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

5,054 citations

Journal ArticleDOI
TL;DR: The mechanisms of generation and potential impacts of microplastics in the ocean environment are discussed, and the increasing levels of plastic pollution of the oceans are understood, it is important to better understand the impact of microPlastic in the Ocean food web.

4,706 citations

Journal ArticleDOI
TL;DR: In this paper, the complex mechanisms of Fenton and Fenton-like reactions and the important factors influencing these reactions, from both a fundamental and practical perspective, in applications to water and soil treatment, are discussed.
Abstract: Fenton chemistry encompasses reactions of hydrogen peroxide in the presence of iron to generate highly reactive species such as the hydroxyl radical and possibly others. In this review, the complex mechanisms of Fenton and Fenton-like reactions and the important factors influencing these reactions, from both a fundamental and practical perspective, in applications to water and soil treatment, are discussed. The review covers modified versions including the photoassisted Fenton reaction, use of chelated iron, electro-Fenton reactions, and Fenton reactions using heterogeneous catalysts. Sections are devoted to nonclassical pathways, by-products, kinetics and process modeling, experimental design methodology, soil and aquifer treatment, use of Fenton in combination with other advanced oxidation processes or biodegradation, economic comparison with other advanced oxidation processes, and case studies.

3,218 citations

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TL;DR: Due to complexity of soil-water system in nature, the effectiveness of biochars on remediation of various organic/inorganic contaminants is still uncertain.

3,163 citations

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TL;DR: The technical feasibility of various low-cost adsorbents for heavy metal removal from contaminated water has been reviewed and it is evident from the literature survey of about 100 papers that low- cost adsorbent have demonstrated outstanding removal capabilities for certain metal ions as compared to activated carbon.

3,072 citations