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.

Perfluorooctanoic acid Degradation by UV/Chlorine

Abstract: While per- and polyfluoroalkyl substances (PFAS) are recalcitrant to chemical reactions traditionally used in water treatment, we report the novel finding that combining ultraviolet (UV, 254 nm) light and chlorine can promote perfluorooctanoic acid (PFOA) degradation. About 12% removal of 100 μg/L PFOA was observed after 30 min of irradiation (6.5 × 10–6 Einstein L–1 s–1) in the presence of 1.4 mM (106 mg/L) NaOCl, compared to only 1% removal by UV photolysis and no removal by NaOCl alone. UV/chlorine with 0.02 mM NaOCl (1.5 mg/L, a more common dose for water treatment) removed 6 μg/L PFOA within 30 min. To better detect defluorination, 50 mg/L PFOA was used, and UV/chlorine released significantly more fluoride (382 μg/L) than UV photolysis (0 μg/L) and dark controls (0 μg/L) over 30 min. By 60 min, this represents 32% of the maximum possible defluorination for the amount of PFOA removed by UV/chlorine versus 2% for UV photolysis. Radical scavenger tests indicated that Cl• and Cl2•– play a crucial role in PFOA degradation, which we postulate is initiated by electron abstraction leading to a decarboxylation–hydroxylation–elimination–hydrolysis pathway. Whereas reaction rates were relatively slow for practical application in water treatment plants, these results underscore overlooked reactions with common water treatment constituents that may influence the fate of PFAS.

Beta-lactam-Induced Outer Membrane Alteration Confers E. coli a Fortuitous Competitive Advantage through Cross-Resistance to Bacteriophages

Abstract: Bacteriophages play an important role in controlling bacteria populations; yet, little is known about their differential effects on antibiotic resistant bacteria (ARB) proliferation. Here, we repor...

Guest Comment: Nanoscale Metal-Organic Matter Interactions

Abstract: T Focus Issue of Environmental Science & Technology, “Nanoscale Metal Organic Matter Interactions”, evolved as a response to recent developments in two areas of the aquatic sciences. First, advances in the study of metal biogeochemistry at the biological interface are improving our understanding of the processes governing the geochemistry and bioavailability of trace metals in aquatic systems. Second, there has been a wave of interest in the reactivity, fate, and transport of nanosized particles. By virtue of their small size and large relative surface area, nanomaterials exhibit different properties and reactivities than do larger size materials of the same composition, and they present new challenges in assessing their environmental and ecological chemistries. In natural waters, the interactions of naturally occurring dissolved organic matter (DOM) with both metals and metal-based nanomaterials are key to understanding the geochemistry, bioavailability, and transport of metals, colloids, and engineered nanoparticles. The significance of DOM in controlling the aqueous chemistry of metals and colloids has been recognized for some time. Dissolved organicmatter derived from a variety of sources (e.g., plant biomass) is a moderator of reactivity at the molecular and nanoparticle scales in aquatic systems.Ubiquitous inwater, soil, and sediment environments, DOM frequently controls metal speciation and the surface charge of particles, influences sorption interactions with mineral surfaces and mineral dissolution/precipitation reactions, and drives important transformations such as redox and photochemical reactions. These interactions shape the behavior ofmetals, colloids, andnanoparticles in aquatic systems. Despite years of study, however, defining the roles played by DOM beyond this general understanding has not come easily. Difficulties stem from a number of factors: DOM itself is composed of thousands of different molecules; the metals or metalbased nanoparticles of interest are often present in the environment at low concentrations; and natural systems are inherently complex due to the integration of chemical, geological, and biological processes. Despite these obstacles, environmental scientists and engineers have long placed emphasis on understanding geochemical and ecological roles of DOM in aquatic systems. In only the fourth issue of Environmental Science & Technology (1967), Russ Christman published the first paper to appear in the journal describing the potential influences of DOM on metal binding (in this case its influence on metal binding in lakes) (Environ. Sci. Technol. DOI 10.1021/es60004a603). Since then, ES&T has published many seminal papers describingDOMchemistry. Collectively, theseworks have greatly advanced our understanding of DOM in environmental processes including its role in the reactivity and transport of metals and anthropogenic organic molecules, its ability to control oxidation reduction and photochemical reactions in natural waters, and its effects on engineeredprocesses such aswater treatment.Given the steady attention investigators have paid to DOM over the years, it would be a stretch to describe recent studies related to DOM reactivity as a “resurgence” of interest in the field. Still, a number of exciting advances related to DOM chemistry have recently taken place in almost all areas of the aquatic sciences, including ecology, geochemistry, and ecosystem modeling. In particular, advances in the analyses of DOM itself are leading to new insights into its composition and the development of better tools for assessing its reactivity and for monitoring its movement throughout the hydrologic system. More sophisticated and sensitive analytical approaches, such as high-resolutionmass spectrometry and nuclear magnetic resonance spectroscopy, are yielding much more detailed compositional information than was available just a few years ago. In addition, DOM optical properties, such as UV/visible absorbance and fluorescence spectroscopy, are being utilized to infer information related to DOM composition and reactivity. The links between the nature and reactivity of DOM and its optical properties are being exploited as powerful monitoring tools to assess the impacts of climate change and management practices on overall water quality, on DOM transport and transformation, and on the transport of other chemical constituents of interest, such as mercury. Furthermore, recent developments from the nanosciences have brought about new tools and novel applications of conventional methods that can be used to investigate metal DOM interactions at the nanoscale. These are exciting times across the aquatic sciences for those interested in DOM dynamics. The papers in this special issue describe the effects exerted by DOM on metals and nanomaterials and deal with a range of topics including computer-based modeling of metal DOM binding interactions, the role of DOM on metal/mineral transformations (aggregation, precipitation, and sorption reactions), and subsequent implications for bioavailability and transport. These contributions improve our understanding of the influences of DOM in the environment. Ultimately, this improved understanding will enhance our ability to predict the environmental fate and biological uptake of metals, and the unique interactions nanomaterials may have with aquatic organisms.

U.S.-China Collaboration is Vital to Global Plans for a Healthy Environment and Sustainable Development.

Abstract: Author(s): Xu, Ming; Daigger, Glen T; Xi, Chuanwu; Liu, Jianguo; Qu, Jiuhui; Alvarez, Pedro J; Biswas, Pratim; Chen, Yongsheng; Dolinoy, Dana; Fan, Ying; Gao, Huaizhu Oliver; Hao, Jiming; He, Hong; Kammen, Daniel M; Lemos, Maria Carmen; Liu, Fudong; Love, Nancy G; Lu, Yonglong; Mauzerall, Denise L; Miller, Shelie A; Ouyang, Zhiyun; Overpeck, Jonathan T; Peng, Wei; Ramaswami, Anu; Ren, Zhiyong; Wang, Aijie; Wu, Brian; Wu, Ye; Zhang, Junfeng; Zheng, Chunmiao; Zhu, Bing; Zhu, Tong; Chen, Wei-Qiang; Liu, Gang; Qu, Shen; Wang, Chunyan; Wang, Yutao; Yu, Xueying; Zhang, Chao; Zhang, Hongliang

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

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...

Advanced Oxidation Processes for Organic Contaminant Destruction Based on the Fenton Reaction and Related Chemistry

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.