Photochemical formation of hydrogen peroxide in surface and ground waters exposed to sunlight.
13 May 1983-Science (American Association for the Advancement of Science)-Vol. 220, Iss: 4598, pp 711-712
TL;DR: A rapid increase in the concentration of hydrogen peroxide was observed when samples of natural surface and ground water from various locations in the United States were exposed to sunlight.
Abstract: A rapid increase in the concentration of hydrogen peroxide was observed when samples of natural surface and ground water from various locations in the United States were exposed to sunlight. The hydrogen peroxide is photochemically generated from organic constituents present in the water; humic materials are believed to be the primary agent producing the peroxide. Studies with superoxide dismutase suggest that the superoxide anion is the precursor of the peroxide.
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Book•
01 Jun 1989
TL;DR: The chemical composition of natural water is derived from many different sources of solutes, including gases and aerosols from the atmosphere, weathering and erosion of rocks and soil, solution or precipitation reactions occurring below the land surface, and cultural effects resulting from human activities.
Abstract: The chemical composition of natural water is derived from many different sources of solutes, including gases and aerosols from the atmosphere, weathering and erosion of rocks and soil, solution or precipitation reactions occurring below the land surface, and cultural effects resulting from human activities. Broad interrelationships among these processes and their effects can be discerned by application of principles of chemical thermodynamics. Some of the processes of solution or precipitation of minerals can be closely evaluated by means of principles of chemical equilibrium, including the law of mass action and the Nernst equation. Other processes are irreversible and require consideration of reaction mechanisms and rates. The chemical composition of the crustal rocks of the Earth and the composition of the ocean and the atmosphere are significant in evaluating sources of solutes in natural freshwater. The ways in which solutes are taken up or precipitated and the amounts present in solution are influenced by many environmental factors, especially climate, structure and position of rock strata, and biochemical effects associated with life cycles of plants and animals, both microscopic and macroscopic. Taken together and in application with the further influence of the general circulation of all water in the hydrologic cycle, the chemical principles and environmental factors form a basis for the developing science of natural-water chemistry. Fundamental data used in the determination of water quality are obtained by the chemical analysis of water samples in the laboratory or onsite sensing of chemical properties in the field. Sampling is complicated by changes in the composition of moving water and by the effects of particulate suspended material. Some constituents are unstable and require onsite determination or sample preservation. Most of the constituents determined are reported in gravimetric units, usually milligrams per liter or milliequivalents
6,271 citations
Cites background or result from "Photochemical formation of hydrogen..."
...According to Cooper and Zika (1983), hydrogen peroxide (HaOa) is present in aerated natural waters exposed to sunlight, and these investigators believed its presence is related to photochemical processes mediated by organic solutes (humic material)....
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...The literature on the geochemistry of bromine was reviewed by Correns (1956), and a more recent summary of bromine geochemistry in relation to the atmosphere and natural waters was written by Fuge (1973)....
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...According to Cooper and Zika (1983), hydrogen peroxide (HaOa) is present in aerated natural waters exposed to sunlight, and these investigators believed its presence is related to photochemical processes mediated by organic solutes (humic material). Concentrations greater than 100 pg/L of Ha02 were observed in surfacewater samples exposed to sunlight (1.0 watt-hour/m’). The samples contained from 12 to 18 mg/L TOC. Similar results were obtained using ground-water samples. Thermodynamic data of Wagman and others (1968, p. 11-13) indicate that the equilibrium concentration of Hz02 in aerated water is about 12 orders of magnitude smaller than the concentrations reported by Cooper and Zika (1983). However, other investigators referenced in Cooper and Zika’s paper have found Ha02 in rainwater and seawater....
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...The literature on the geochemistry of bromine was reviewed by Correns (1956), and a more recent summary of bromine geochemistry in relation to the atmosphere and natural waters was written by Fuge (1973). Bromide is present in major concentrations in some brines....
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Book•
01 Jan 1985
TL;DR: The first part of the book as mentioned in this paper is a general overview of the amount and general nature of dissolved organic carbon in natural waters, and the second part is a summary of the data that has accumulated from many disciplines over the last decade.
Abstract: This book is written as a reference on organic substances in natural waters and as a supplementary text for graduate students in water chemistry. The chapters address five topics: amount, origin, nature, geochemistry, and characterization of organic carbon. Of these topics, the main themes are the amount and nature of dissolved organic carbon in natural waters (mainly fresh water, although seawater is briefly discussed). It is hoped that the reader is familiar with organic chemistry, but it is not necessary. The first part of the book is a general overview of the amount and general nature of dissolved organic carbon. Over the past 10 years there has been an exponential increase in knowledge on organic substances in water, which is the result of money directed toward the research of organic compounds, of new methods of analysis (such as gas chromatography and mass spectrometry), and most importantly, the result of more people working in this field. Because of this exponential increase in knowledge, there is a need to pull together and summarize the data that has accumulated from many disciplines over the last decade.
2,803 citations
Cites background or methods from "Photochemical formation of hydrogen..."
...Seawater has been studied extensively for dissolved hydrocarbons (Jeffrey and others, 1964-; Garrett, 1967; Blumer 1970; Copin and Barbier, 1971; Duce and others, 1972; Parker and others, 1972; Barbier and others, 1973; Brown and others, 1973; Levy and Walton, 1973; Zsolnay, 1973a,b; Iliffe and Calder, 1974-; Ledet and Laseter, 1974-; Wade and Quinn, 1975; Marty and Saliot, 1976; Morris and others, 1976; Hardy and others, 1977; Keizer and others, 1977; Paradis and Ackman, 1977; Saliot and Tissier, 1977; Schultz and Quinn, 1977; Simoneit and others, 1977; Zsolnay, 1977a,b; Marty and others, 1978; Sauer, 1978; Schwarzenbach and others, 1978; Gschwend and others, 1980; Sauer, 1980; Law, 1981; Sauer, 1981a,b; Gschwend and others, 1982; and Mantoura and others, 1982)....
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...For example, the work of Cowie and Hedges (1984) has been the most interesting research in this area....
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TL;DR: In this article, the reactions of nanomolar concentrations of Cu(I) and Cu(II) with H 2 O 2 have been investigated in 2.0mM NaHCO 3 and 0.7m NaCl at pH 8.0.
475 citations
TL;DR: In short, solar radiation can provide the energy to initiate reactions while atmospherically available surfaces or condensed phases may act to reduce the required energy for a given photochemical pathway, for instance, by allowing a longer wavelength for reaction of species associated with a surface or bulk phase environment.
Abstract: Atmospheric aerosols can be categorized into primary particles, which are directly emitted by their sources, and secondary particles, generated in the atmosphere from gaseous inorganic and organic precursors. For example, atmospheric oxidation of sulfur containing compounds leads to sulfuric acid and its salts, which represent a major secondary inorganic component of atmospheric aerosols. Likewise, oxidation of nitrogen oxides leads to nitric acid or its salts, which are also abundant in aerosols. The ocean surface, which covers three-quarters of the planet, offers a remarkably dynamic and chemically complex surface for interfacial reactions in the marine boundary layer. The porous nature of permanent or perennial snowpacks adds a tremendous amount of surface area, with which the atmosphere interacts. In short, solar radiation can provide the energy to initiate reactions while atmospherically available surfaces or condensed phases may act to reduce the required energy for a given photochemical pathway, for instance, by allowing a longer wavelength for reaction of species associated with a surface or bulk phase environment.
465 citations
TL;DR: It is proposed that the superoxide is the main oxidant of arsenite in the TiO2/UV process and both Fe3+ and HA that were often found with the arsenic in groundwater were beneficial to the photocatalytic oxidation of arsenites, which could be a viable pretreatment method.
Abstract: Arsenite [As(III)] and arsenate [As(V)] are highly toxic aquatic contaminants. Since arsenite is more mobile in natural waters and less efficiently removed in adsorption/coagulation processes than arsenate, the oxidation of arsenite to arsenate is desirable in water treatment. We performed the photocatalytic oxidation of arsenite in aqueous TiO2 suspension and investigated the effects of pH, dissolved oxygen, humic acid (HA), and ferric ions on the kinetics and mechanisms of arsenite oxidation. Arsenite oxidation in UV-illuminated TiO2 suspension was highly efficient in the presence of dissolved oxygen. Homogeneous photooxidation of arsenite in the absence of TiO2 was negligibly slow. Since the addition of excess tert-butyl alcohol (OH radical scavenger) did not reduce the rate of arsenite oxidation, the OH radicals should not be responsible for As(III) oxidation. The addition of HA increased both arsenite oxidation and H2O2 production at pH 3 under illumination, which could be ascribed to the enhanced superoxide generation through sensitization. We propose that the superoxide is the main oxidant of arsenite in the TiO2/UV process. The addition of ferric ions also significantly enhanced the arsenite photooxidation. In this case, the addition of tert-butyl alcohol reduced the arsenite oxidation rate, which implied thatthe OH radical-mediated oxidation path was operative in the presence of ferric ions. Since both Fe3+ and HA that were often found with the arsenic in groundwater were beneficial to the photocatalytic oxidation of arsenite, the TiO2/UV process could be a viable pretreatment method. This can be as simple as exposing the arsenic-polluted water in a TiO2-coated trough to sunlight.
367 citations
References
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TL;DR: The reactive superoxide radical, O2-, formerly of concern only to radiation chemists and radiobiologists, is now understood to be a normal product of the biological reduction of molecular oxygen.
Abstract: The reactive superoxide radical, O2-, formerly of concern only to radiation chemists and radiobiologists, is now understood to be a normal product of the biological reduction of molecular oxygen. An unusual family of enzymes, the superoxide dismutases, protect against the deleterious actions of this radical by catalyzing its dismutation to hydrogen peroxide plus oxygen.
3,273 citations
TL;DR: EDTA had no effect on the enzyme-catalyzed dismutation of superoxide radicals, but did eliminate catalysis by Cu++, and Boiling the enzyme or reversibly removing its copper prosthetic group caused loss of catalytic activity.
470 citations
TL;DR: In this article, the authors simulate the free radical chemistries of the gas phase and aqueous phase within a warm cloud during midday solar fluxes and demonstrate that the scavenging of OH and HO2 from cloud droplets can represent a major source of free radicals to cloud water provided the accommodation or sticking coefficient for these species impinging upon water droplets is not less than 0.0001.
Abstract: Calculations are presented that simulate the free radical chemistries of the gas phase and aqueous phase within a warm cloud during midday. It is demonstrated that in the presence of midday solar fluxes, the heterogeneous scavenging of OH and HO2 from the gas phase by cloud droplets can represent a major source of free radicals to cloud water, provided the accommodation or sticking coefficient for these species impinging upon water droplets is not less than 0.0001. The aqueous-phase of HO2 radicals are found to be converted to H2O2 by aqueous-phase chemical reactions at a rate that suggests that this mechanism could produce a significant fraction of the H2O2 found in cloud droplets. The rapid oxidation of sulfur species dissolved in cloudwater by this free-radical-produced H2O2 as well as by aqueous-phase OH radicals could conceivably have a significant impact upon the chemical composition of rain.
342 citations
TL;DR: H2O2 has been shown to account for the biological activities of near-ultraviolet irradiation of saturated, oxygenated solutions of tryptophan in the absence of added sensitizer.
Abstract: Near-ultraviolet (300 to 400 nanometers) irradiation of saturated, oxygenated solutions of tryptophan in the absence of added sensitizer gives rise to substances that have various biological effects on isolated cells, including mutagenicity and selective lethality to recombination-deficient bacterial mutants. One of these biologically active products has been identified as H2O2, on the basis of spectrometric, chromatographic, chemical, and biological properties. Now H2O2 has been shown to account for the biological activities mentioned above.
187 citations
TL;DR: In this article, measurements of H2O2 in rainwater collected in Miami, Florida, and the Bahama Islands area indicate the presence of aqueous phase reactions within the cloudwater rather than via rainout and washout of gaseous H 2O2.
Abstract: Measurements of H2O2 in rainwater collected in Miami, Florida, and the Bahama Islands area indicate the presence of H2O2 concentration levels ranging from 100,000 to 700,000 M No systematic trends in H2O2 concentration were observed during an individual storm, in marked contrast to the behavior of other anions for example, NO3(-), SO4(-2), and Cl(-) The data suggest that a substantial fraction of the H2O2 found in precipitation is generated by aqueous-phase reactions within the cloudwater rather than via rainout and washout of gaseous H2O2
132 citations