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Showing papers in "Environmental Science & Technology in 1992"


Journal ArticleDOI
TL;DR: In this paper, the herbicides 2,4-dichlorophenoxyacetic acid (2,4D) and 2, 4-5-trichlor-pharmoxyacetics acid(2, 4,5-T) were degraded in acidic aerated solutions of H 2 O 2 and Fe 2+ or Fe 3+.
Abstract: The herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were degraded in acidic aerated solutions of H 2 O 2 and Fe 2+ or Fe 3+ . Conditions leading to complete mineralization could be achieved using Fe 3+ /H 2 O 2 , which thereby became the focus of the study. Herbicide transformation by Fe 3+ /H 2 O 2 , was sensitive to pH (optimum, 2.7-2.8) and was inhibited by methanol or chloride due to scavenging of the active oxidant, and by sulfate due to complexation of Fe 3+

1,177 citations


Journal ArticleDOI
TL;DR: The relationship between bacterial sulfate reduction and mercury methylation, as well as the in situ distribution of methylmercury in sediments, was studied in Quabbin Reservoir, MA as mentioned in this paper.
Abstract: The relationship between bacterial sulfate reduction and mercury methylation, as well as the in situ distribution of methylmercury in sediments, was studied in Quabbin Reservoir, MA. Fish methylmercury levels in Quabbin and other lakes affected by acid deposition are often elevated. However, the cause of acceleration of net methylmercury production or bioaccumulation in these lakes is poorly understood. Experimental additions of sulfate to either anoxic sediment slurries or lake water above intact sediment cores resulted in increased microbial production of methylmercury from added inorganic mercury

1,115 citations



Journal ArticleDOI
TL;DR: In this article, indirect photooxidation of trace hydroxyl radical (. OH) probes in aqueous solutions was used to evaluate the nature and formation efficiency of the transient oxidants that are generated when hydrogen peroxide reacts with Fe(II) that is produced from photoreduction of Fe(III) (λ=436 nm)
Abstract: Kinetics studies of the indirect photooxidation of trace hydroxyl radical ( . OH) probes in aqueous solutions were used to evaluate the nature and formation efficiency of the transient oxidants that are generated when hydrogen peroxide reacts with Fe(II) that is produced from photoreduction of Fe(III) (λ=436 nm)

847 citations


Journal ArticleDOI
TL;DR: In this article, rate constants for reactions of the hydroxyl radical with 25 potential organic drinking water contaminants, including solvents, haloalkanes, esters, aromatics, and pesticides (for example, aldicarb, atrazine, 1,2-dibromo-3-chloropropane, endrin, glyphosate, lindane, picloram, etc.), have been measured in mater using relative rate methods.
Abstract: Rate constants for reactions of the hydroxyl radical with 25 potential organic drinking water contaminants, including solvents, haloalkanes, esters, aromatics, and pesticides (for example, aldicarb, atrazine, 1,2-dibromo-3-chloropropane, endrin, glyphosate, haloforms, lindane, picloram, etc.), have been measured in mater using relative rate methods. A variety of HO . -generating techniques mere used, including ozone decomposition, Fenton's reaction, and a convenient new method employing photo-Fenton's chemistry. In addition, rate constants for 19 other compounds mere estimated using structure-activity relationships

764 citations


Journal ArticleDOI
TL;DR: In this article, the generation of hydrogen peroxide (H 2 O 2,) and the depletion of oxalic acid by photochemical/chemical cycling of Fe(III)/Fe(II)-oxalato complexes in sunlight has been studied under the conditions typical for acidified atmospheric water.
Abstract: The generation of hydrogen peroxide (H 2 O 2 ,) and the depletion of oxalic acid by photochemical/chemical cycling of Fe(III)/Fe(II)-oxalato complexes in sunlight has been studied under the conditions typical for acidified atmospheric water. H 2 O 2 is produced though the reduction of oxygen by intermediates formed from photoreactions of Fe(III)-oxalato complexes. The rate of H 2 O 2 formation increases with sunlight intensity, and with oxalate and Fe(III) concentration within the concentration range used

751 citations


Journal ArticleDOI
TL;DR: In this article, the molar concentration of acid volatile sulfide (AVS) in the sediment is defined as the threshold below which these metals cease to exhibit an acute toxicity in freshwater and marine sediments.
Abstract: Laboratory toxicity tests using amphipods, oligochaetes, and snails with spiked freshwater and marine sediments and with contaminated sediments collected from an EPA Superfund site demonstrate that no significant mortality occurs relative to controls if the molar concentration of acid volatile sulfide (AVS) in the sediment is greater than the molar concentration of simultaneously extracted cadmium and/or nickel. Although it is well-known that these metals can form insoluble sulfides, it apparently has not been realized that AVS is a reactive pool of solid-phase sulfide that is available to bind metals and render that portion unavailable and nontoxic to biota. Thus, the AVS concentration of a sediment establishes the boundary below which these metals cease to exhibit an acute toxicity in freshwater and marine sediments.

642 citations


Journal ArticleDOI
TL;DR: In this paper, a composite model, the distributed reactivity model (DRM), is introduced to characterize intrinsic heterogeneities in the properties and behaviors of soils and sediments and to capture the resulting nonlinearities of sorption isotherms.
Abstract: Contaminant sorption by soils and sediments is characterized as a multiple reaction phenomenon. The approach is predicated on the observation that most natural soils and sediments are intrinsically heterogeneous even at the microscopic scale; that is, variable in composition and structure at both interparticle and intraparticle scales. Heterogeneity is demonstrated for a number of soils which, on the basis of conventional macroscopic properties, would be considered homogeneous. That such heterogeneities are reflected in sorption reactions which differ between soils and between different fractions of soil is also demonstrated. A composite model, the distributed reactivity model (DRM), is introduced to characterize intrinsic heterogeneities in the properties and behaviors of soils and sediments and to capture the resulting nonlinearities of sorption isotherms. Finally, the significance of particle-scale heterogeneity and distributed reactivity is illustrated by using measured parameters and DRM calculations to characterize differences in the relative sorption behavior of soils comprising different mass fractions of differently reactive components. 31 refs., 9 figs., 2 tabs.

617 citations


Journal ArticleDOI
TL;DR: In this paper, the authors found that milkweed fiber and cotton fiber sorbed significantly higher amounts of crude oil than polypropylene fiber and polyethylene web from the surface of an artificial sea water bath containing crude oil and from a crude oil bath.
Abstract: Milkweed (Asclepias) fiber and cotton fiber sorbed significantly higher amounts of crude oil than polypropylene fiber and polypropylene web from the surface of an artificial sea water bath containing crude oil and from a crude oil bath. Milkweed sorbed approximately 40 g of crude oil/g of fiber at room temperature. The oil sorption capacity of kenaf core material was comparable with that of polypropylene web with high-viscosity Bunker C oil. Only a slight variation was observed in the oil sorption of the natural fiber sorbent by Soxhlet extraction and water-soaking treatments before the sorption process

539 citations


Journal ArticleDOI
TL;DR: In this article, the feasibility of surfactant use for in situ aquifer remediation with respect to nonaqueous phase liquids has been discussed, and the feasibility and feasibility of using surfactants in the subsurface environment has been evaluated.
Abstract: Because of the limitations of pump-and-treat technology, attention is now focused on the feasibility of surfactant use to increase its efficiency. Surfactants have been studied for use in soil washing and enhanced oil recovery. Although similarities exist between the applications, there are significant differences in the objectives of the technologies and the limitations placed on surfactant use. In this article we review environmental studies concerned with the fate and transport of surface-active compounds in the subsurface environment and discuss key issues related to their successful use for in situ aquifer remediation, particularly with respect to nonaqueous-phase liquids.

492 citations



Journal ArticleDOI
TL;DR: In this paper, a kinetic model of the reacting aqueous chlorine-ammonia system is proposed which describes equally well the rapid "breakpoint" oxidation of ammonia, where the applied chlorine dose (CI 2 ) to ammonia-nitrogen molar ratio (Cl/N) is greater than approximately 1.6.
Abstract: A kinetic model of the reacting aqueous chlorine-ammonia system is proposed which describes equally well the rapid «breakpoint» oxidation of ammonia, where the applied chlorine dose (CI 2 ) to ammonia-nitrogen molar ratio (Cl/N) is greater than approximately 1.6; the slow oxidation of ammonia in aqueous chloramine solutions (Cl/N<1); and the transition region of 1

Journal ArticleDOI
TL;DR: In this paper, an organic carbon (DOC) was removed from solution by sorption onto aluminum and iron oxides, which precipitate as the two streamwaters mix, and upstream DOC concentrations, which increase during snowmelt, were identified as the most significant variables in a multiple regression for determining the DOC concentration below the confluence.
Abstract: Organic solute sorption by hydrous iron and aluminum oxides was studied in an acidic, metal-enriched stream (the Snake River) at its confluence with a pristine stream (Deer Creek). From 1979 to 1986, typically 40% of the dissolved organic carbon (DOC) was removed from solution by sorption onto aluminum and iron oxides, which precipitate as the two streamwaters mix. Upstream DOC concentrations, which increase during snowmelt, were identified as the most significant variables in a multiple regression for determining the DOC concentration below the confluence, and the extent of Al and Fe precipitation was much less significant

Journal ArticleDOI
TL;DR: Preemergent herbicides and their metabolites, particularly atrazine, deethylatrazine and metolachlor, persisted from 1989 to 1990 in the majority of rivers and streams in the mid-western United States as mentioned in this paper.
Abstract: Preemergent herbicides and their metabolites, particularly atrazine, deethylatrazine, and metolachlor, persisted from 1989 to 1990 in the majority of rivers and streams in the midweatern United States. In spring, after the application of herbicides, the concentrations of atrazine, alachlor, and simazine were frequently 3-10 times greater than the U.S. Environmental Protection Agency maximum cortaminant level (MCL).

Journal ArticleDOI
TL;DR: In this paper, the oxidation of Cr(III) by a common naturally occurring form of manganese oxide, δ-MnO 2, was characterized over a range of Cr (III) concentrations and pH values.
Abstract: The oxidation of Cr(III) by a common naturally occurring form of manganese oxide, δ-MnO 2 , was characterized over a range of Cr(III) concentrations and pH values. Cr(III) oxidation was limited as pH and Cr(III) concentrations increased. Reaction products, Mn(II) and Cr(VI), did not limit Cr(III) oxidation. Initial Cr(III) oxidation rates were very rapid at pH=5, but were subsequently followed by a dramatic rate decline. Thermodynamic calculations using solution species indicated the reaction should proceed under conditions where the reaction had terminated


Journal ArticleDOI
TL;DR: In this paper, the complexation of organic xenobiotics with humic material in aquatic or terrestrial environments was studied and the mechanism by which halogenated phenols and anilines were bound to humic materials and the chemical nature of these bound residues was also presented.
Abstract: Xenobiotics are manmade compounds often introduced into the environment at concentrations that cause undesirable effects. They can be transformed as a result of biotic and abiotic processes, leading to changes in their chemical state and ultimately in their toxicity and reactivity. Ideally, xenobiotics are transformed into carbon dioxide, water, and mineral elements. However, many of them are converted to intermediate products that can be as toxic as or more so than their parent compounds. This article focuses on the complexation of organic xenobiotics with humic material in aquatic or terrestrial environments. The information presented here focuses on the mechanism by which halogenated phenols and anilines are bound to humic material and the chemical nature of these bound residues. Data on the toxicity and ultimate stability of bound chemicals is also presented. Studies indicate that enzymatic coupling is a promising method for detoxification of environments contaminated with xenobiotics. 33 refs., 2 figs., 2 tabs.

Journal ArticleDOI
TL;DR: A review of the existing methods available for assessing sediment quality, an analysis of the complexity and uncertainty of the sediment assessment methodologies, and a proposed approach that utilizes the unique attributes of many of these methods in a tiered sediment assessment strategy are presented in this paper.
Abstract: The protection of aquatic resources has assumed national and global prominence. Oil spills, medical wastes, and plastic debris presence on beaches, ocean incineration, ocean disposal of garbage and dredged materials, pesticide and fertilizer runoff, contaminated harbors, and diminishing fisheries have focused public attention on the need to adequately protect marine and freshwater resources-including sediments. Sediments are repositories for physical debris and [open quotes]sinks[close quotes] for a wide variety of chemicals. The concern associated with the chemicals sorbed to sediments is that many commercial species and food chain organisms spend a major portion of their life-cycle living in or on aquatic sediments. This provides a pathway for these chemicals to be consumed by higher aquatic life and wildlife, including avian species as well as humans. Direct transfer of chemicals from sediments to organisms is now considered to be a major route of exposure for many species. Concern has increased over the number of incidences of tumors being observed in many species of fish, especially those that have direct contact with sediments. These issues are focusing attention on sediment contamination and highlight the fact that sediments are an important resource. The purposes of this article are to provide background information on themore » status of sediment assessment in the United States, a review of the existing methods available for assessing sediment quality, an analysis of the complexity and uncertainty of the sediment assessment methodologies, and a proposed approach that utilizes the unique attributes of many of these methods in a tiered sediment assessment strategy. The authors hope that this sediment assessment strategy will help provide a mechanism for achieving cleaner sediments and wate rin the nation's aquatic ecosystems.« less

Journal ArticleDOI
TL;DR: In this paper, roadside soils were sampled from areas that receive heavy traffic and deicing salts, and they were leached in columns at 6 degrees C with solutions of NaCl, calcium magnesium acetate (CMA), or deionized water to simulate the runoff of salty water from a roadway followed by snowmelt or rainwater.
Abstract: Roadside soils were sampled from areas that receive heavy traffic and deicing salts. These soils were leached in columns at 6 degrees C with solutions of NaCl, calcium magnesium acetate (CMA), or deionized water to simulate the runoff of salty water from a roadway followed by snowmelt or rainwater. In the salt solution leachates, the concentrations of Cr, Pb, Ni, Fe, Cd, and Cu tended to increase with increasing salt concentration, suggesting that ligand complexation and competitive exchange affected mobilization. In the soils leached initially with NaCl, followed by deionised water, extensive mobilization of organic matter and elevated concentrations of Cr, Pb, Ni, Fe, and Cu were observed. The dominant mechanism controlling metal mobilization was dispersion of organic matter under conditions of high exchangeable Na and low electrolyte concentration. (A)

Journal ArticleDOI
TL;DR: In this paper, the reduction of substituted nitrobenzenes in aqueous solution containing hydrogen sulfide was investigated and the rate constants were proportional to NOM concentrations and increased with increasing pH and decreasing reduction potential.
Abstract: Natural organic matter (NOM) from a variety of sources has been shown to mediate the reduction of substituted nitrobenzenes in aqueous solution containing hydrogen sulfide. Pseudo-first-order rate constants were proportional to NOM concentrations and increased with increasing pH and decreasing reduction potential (E h ) of the solution. At fixed pH and E h , the carbon-normalized rateconstants (k NOM ) of a given compound varied less than 1 order of magnitude among NOMs derived from various natural waters

Journal ArticleDOI
TL;DR: In this paper, Desulfovibrio desulfuricans readily removed uranium from solution in a batch system or when D. desufuricans was separated from the bulk of the uranium-containing water by a semipermeable membrane.
Abstract: Enzymatic uranium reduction by Desulfovibrio desulfuricans readily removed uranium from solution in a batch system or when D. desufuricans was separated from the bulk of the uranium-containing water by a semipermeable membrane. Uranium reduction continued at concentrations as high as 24 mM. Of a variety of potentially inhibiting anions and metals evaluated, only high concentrations of copper inhibited uranium reduction

Journal ArticleDOI
TL;DR: In this paper, the sorption at room temperature of benzene and carbon tetrachloride from water on three high-organic-content soils (muck, peat, and extracted peat) and on cellulose was determined in order to evaluate the effect of sorbent polarity on the solute partition coefficients.
Abstract: The sorption at room temperature of benzene and carbon tetrachloride from water on three high-organic-content soils (muck, peat, and extracted peat) and on cellulose was determined in order to evaluate the effect of sorbent polarity on the solute partition coefficients. The isotherms are highly linear for both solutes on all the organic matter samples, which is consistent with a partition model. For both solutes, the extracted peat shows the greatest sorption capacity while the cellulose shows the lowest capacity; the difference correlates with the polar-to-nonpolar group ratio [(O+N)/C] of the sorbent samples

Journal ArticleDOI
TL;DR: Particulate organo-Se was assimilated with 86% efficiency by the deposit feeding bivalve Macoma balthica, when the clam was fed 75 Se-labeled diatoms as discussed by the authors.
Abstract: Particulate organo-Se was assimilated with 86% efficiency by the deposit feeding bivalve Macoma balthica, when the clam was fed 75 Se-labeled diatoms. Absorption efficiencies of particulate elemental Se were 22%, when the animals were fed 75 Se-labeled sediments in which elemental Se was precipitated by microbial dissimilatory reduction. Precipitation of elemental Se did not eliminate biological availability of the element. Selenite was taken up from solution slowly by M. balthica (mean concentration factor was 712)

Journal ArticleDOI
TL;DR: In this paper, Solid Phase Microextraction (SPME) was applied to the analysis of benzene, toluene, ethyl benzene and xylenes in groundwater.
Abstract: rn Solid-phase microextraction (SPME) is applied to the analysis of benzene, toluene, ethyl benzene, and xylenes in groundwater. The inexpensive SPME method reduced the sample preparation time by 3-7-fold when compared to purge and trap methods. The relative standard deviation ranged from 3 to 5% for the single-operator relative standard deviation using a methyl silicone fiber. Limits of detection of 1-3 ppb (w/v) were obtained when using a fiber coated with 56-pm methyl silicone film and FID detection. The linear range extended from 15 to 3000 ppb (w/v). Solvents have been completely removed from the sample preparation step.


Journal ArticleDOI
TL;DR: Gas-solid heterogeneous photocatalytic oxidation of trichloroethylene (TCE) in humid airstreams is achieved at high conversion levels in a bench-scale flat-plate fluidized-bed photoreactor, which provides efficient continuous contact of near-ultraviolet photons, silica-supported titania photocatalyst, and gaseous reactants as mentioned in this paper.
Abstract: Gas-solid heterogeneous photocatalytic oxidation of trichloroethylene (TCE) in humid airstreams is achieved at high conversion levels in a bench-scale flat-plate fluidized- bed photoreactor, which provides efficient continuous contact of near-ultraviolet photons, silica-supported titania photocatalyst, and gaseous reactants. Silica-supported titania catalysts prepared through sol-gel methods require ∼1 h on stream time to develop their maximum photocatalytic oxidation activity

Journal ArticleDOI
TL;DR: In this article, the authors measured the presence and absence of ozone in a freshly carpeted 20m stainless-steel room in both the absence and presence of ozone (ozone concentrations ranging from 30 to 50 ppb, with one experiment conducted at 400 ppb).
Abstract: Volatile organic compounds (VOCs) have been measured in a freshly carpeted 20-m[sup 3] stainless-steel room in both the absence and presence of ozone (ozone concentrations ranging from 30 to 50 ppb, with one experiment conducted at 400 ppb). Four different types of carpeting were exposed, and in each set of experiments, the room was ventilated at 1 air exchange/h. The gas-phase concentrations of selected carpet emissions (e.g., 4-phenylcyclohexene, 4-vinylcyclohexene, and styrene) significantly decreased in the presence of ozone. Conversely, the concentrations of other compounds (e.g., formaldehyde, acetaldehyde, and aldehydes with between 5 and 10 carbons) significantly increased. Furthermore, the total concentration of VOCs increased markedly in the presence of ozone. The additional VOCs appear to have been generated by reactions between ozone and relatively nonvolatile compounds associated with the carpets. These studies suggest that VOCs measured within a building at elevated ozone levels (>30 ppb) may differ from those measured at lower ozone levels (<10 ppb). 12 refs., 2 figs., 6 tabs.

Journal ArticleDOI
TL;DR: In this article, the Gibbs free energies of various classes of halogenated aromatic compounds were estimated with Benson's method and the data were used to evaluate the potential of these compounds to serve as electron acceptors in anaerobic environments.
Abstract: The Gibbs free energies of formation of various classes of halogenated aromatic compounds were estimated with Benson's method. The data were used to evaluate the potential of these compounds to serve as electron acceptors in anaerobic environments. The results indicate that for (chloro) benzenes, benzoates, and phenols, the redox potentials of the couples Ar-X/Ar-H are in the range of 266-478 mV. This implies that microorganisms can potentially conserve energy for growth by routing electrons in the form of H2 from anaerobic environments to halogenated aromatic compounds as electron acceptors. This theoretical prediction has been corroborated for 3-chlorobenzoate. The existence of enrichment cultures, obtained from anaerobic sediments and sewage sludges, that dechlorinate other halogenated aromatic compounds suggests the existence of more microorganisms that can benefit from the use of halogenated aromatic compounds as electron acceptors.

Journal ArticleDOI
TL;DR: In this article, the effects of pH and sediment surface characteristics on sorption of indigenous groundwater bacteria were determined using contaminated and uncontaminated aquifer material from Cape Cod, MA.
Abstract: The effects of pH and sediment surface characteristics on sorption of indigenous groundwater bacteria were determined using contaminated and uncontaminated aquifer material from Cape Cod, MA. Over the pH range of the aquifer (5 -7), the extent of bacterial sorption onto sediment in uncontaminated gro undwater was strongly pH-dependent, but relatively pH -insensitive in contaminated groundwater from the site. Bacterial sorption was also affected by the presence of oxyhydroxide coatings (iron, aluminum, and manganese). Surface coating effects were most pronounced in uncontaminated groundwater (pH 6.4 at 10 oC. Desorption of attached bacteria (up to 14% of the total number of labeled cells added) occurred in both field and laboratory experiments upon adjustment of groundwater to pH 8. The dependence of bact erial sorption upon environmental conditions suggests that bacterial immobilization could change substantially over relatively short distances in contaminated, sandy aquifers and that effects caused by changes in groundwater geochemistry can be significant .

Journal ArticleDOI
TL;DR: The first high-temporal resolution PCB data set was obtained over an annual cycle in North America and has obvious use for determining processes of deposition, transport, and atmospheric transformation of these important chemicals as mentioned in this paper.
Abstract: From July 1988 to September 1989, 143 air samples, obtained at Egbert, ON, Canada, were analyzed for vapor-phase polychlorinated biphenyls (PCBs) and organohalogen pesticides. This data set is believed to be the first high temporal resolution PCB data set obtained over an annual cycle in North America and has obvious use for determining processes of deposition, transport, and atmospheric transformation of these important chemicals. Concentrations of the sum of 91 PCB congeners (ΣPCB) of IUPAC No. 16 or higher ranged from a subpicogram per cubic meter detection level to over 2 ng m -3