Showing papers in "Environmental Science & Technology in 1990"

Chlorination of humic materials: byproduct formation and chemical interpretations

Abstract: Ten aquatic humic and fulvic acids were isolated and studied with respect to their reaction with chlorine. Yields of TOX, chloroform, trichloroacetic acid, dichloroacetic acid, dichloroacetonitrile, and 1,1,1-trichloropropanone were measured at pH 7 and 12. Humic acids produced higher concentrations than their corresponding fulvic acids of all byproducts except 1,1,1-trichloropropanone. Chlorine consumption and byproduct formation were related to fundamental chemical characteristics of the humic materials. A statistical model was proposed for activated aromatic content based on {sup 13}C NMR and base titration data. The values estimated from this model were found to be well correlated with chlorine consumption. Specific by-product formation was related to UV absorbance, nitrogen content, or the activated aromatic content.

Less than obvious - statistical treatment of data below the detection limit

Abstract: As researchers increasingly investigate grace substances in the world's soil, air, and water, they frequently find concentrations that are lower than limits deemed reliable enough to report as numerical values. These so-called less-than values - values stated only as

Kinetics of deposition of colloidal particles in porous media

Abstract: A theoretical framework for chemical-colloidal effects on the kinetics of deposition of Brownian particles in porous media has been presented. The theory was tested rigorously by conducting deposition experiments with model colloids and collectors under controlled chemical conditions in a well-defined experimental system

Influence of organic matter from soils and sediments from various origins on the sorption of some chlorinated aliphatic hydrocarbons: implications on KOC correlations.

Abstract: Sorption of nonionic compounds is strongly dependent on the content as well as the nature of the organic matter in soils and sediments. The composition and the structure of organic matter varies due to its origin and geological history and strongly influences the sorption affinity for nonionic organic compounds. Organic matter in unweathered shales and high-grade coals shows enhanced sorption (> 1 order of magnitude) compared to organic matter in recent soils or geologically young material and low-grade coals. The results obtained indicate a decrease in sorption with increasing proportions of oxygen-containing functional groups in natural organic substances. A first approximation to estimate sorption coefficients for various organic matter is provided by an empirical correlation between the hydrogen/oxygen (H/O) atomic ratio as an index of the oxidation of the organic matter and the organic carbon normalized sorption coefficients (K{sub OC}). This approximation also permits adjustment of K{sub OC} values derived from K{sub OW} data.

Influence of mineral-bound humic substances on the sorption of hydrophobic organic compounds

Abstract: The sorption of three hydrophobic organic compounds (HOC) was investigated on hematite and kaolinite that had been coated with natural humic substances over a mass percent carbon range of 0.01-0.5%. Increasing quantities of sorbed humic substances increased the sorption of HOC. Anthracene, the most hydrophobic HOC, showed the greatest sorption enhancement, while the most aromatic coating, peat humic acid, was the strongest sorbent. Depending on the type of humic acid coating and the mineral substrate, the experimental K{sub oc} values were either higher or lower than those predicted by the K{sub ow}. The sorptivity of a given humic acid for HOC was not the same on kaolinite and hematite, suggesting that the orientation and structure of the humic substance on the mineral may affect the surface area of the organic phase and the accessibility of hydrophobic domains that control HOC sorptivity. Sorption isotherms for HOC on the humic-coated mineral substrates were nonlinear, implying that the sorption phenomenon was adsorption onto rather than partitioning into the surface organic phase.

Photocatalytic degradation of atrazine and other s-triazine herbicides.

Abstract: The photocatalytic degradation of s-triazine herbicides (atrazine, simazine, trietazine, prometon, and prometryn) has been investigated by using particulate TiO 2 as photocatalyst under simulated solar light. The herbicides are rapidly degraded. Several intermediates have been identified, and cyanuric acid has been recognized as the final product of the degradation process for all the investigated herbicides. A proposal mechanism of the process is presented

Assessment of fecal sterols and ketones as indicators of urban sewage inputs to coastal waters

Abstract: L'etude montre que la mesure de la concentration en coprostanone apporte un parametre supplementaire pour controler les rejets d'eau usee urbaine en zone cotiere, specialement dans le cas de pollution moderee ou faible

Woodburning as a source of atmospheric polycyclic aromatic hydrocarbons

Abstract: Airborne particulate matter containing polycyclic aromatic hydrocarbons derived from burning natural vegetation and paper products in a variety of ways was collected and analyzed by HPLC. Similar profiles of compounds resulted from most of the combustion sources that do not involve fossil fuels and that are likely to contribute to Sydney's atmospheric particulates. In addition, the profiles did not change markedly as a result of reactions occurring in the atmosphere or from reactions occurring on the filter after collection. Concentrations of benzo(a)pyrene and coronene were higher in the polycyclic aromatic hydrocarbons derived from bush fires than from other sources. Bush fires are likely to be a significant source of exposure of the Sydney population to polycyclic aromatic hydrocarbons.

Photodegradation of 2- and 3-chlorophenol in titanium dioxide aqueous suspensions

Abstract: The photocatalytic degradations of 2-chlorophenol (2CP) and 3-chlorophenol (3CP) in TiO{sub 2} aqueous suspensions at {lambda} > 340 nm have been studied. They are faster than direct photolysis at {lambda} > 290 nm despite the additional number of photons available in this wavelength region and produce lower maximal concentrations of intermediates. Complete mineralization is achieved eventually; however, it requires a much longer time than dechlorination and dearomatization. Effects of radiant flux, wavelength, initial concentrations, and pH are examined. Para hydroxylation is the main pathway, so that 2CP and 3CP both give rise to chlorohydroquinone (CHQ), whereas formation of catechol (CT) is a very minor pathway in the degradation of 2CP. Further hydroxylation of CHQ and CT forms hydroxyhydroquinone, which rapidly decomposes to carboxylic acids and carbonyl compounds not identified yet.

Oxidation of aniline and other primary aromatic amines by manganese dioxide

Abstract: This investigation evaluated the redox reaction between a manganese dioxide, {sigma}-MnO{sub 2}, and anilines and other aromatic reductants in aqueous suspensions at pH values ranging from 3.7 to 6.5. The reaction with manganese dioxide may represent a pathway for transformation of aniline and other primary aromatic amines in acidic mineralogical and soil/water environments in the absence of oxygen and substantial microbial activity. The reaction rate with aniline is pH-dependent, increasing with decreasing pH, and first order with respect to {sigma}-MnO{sub 2} and organic solute. Aniline and p-toluidine are demonstrated to be 2-equiv reductants, as is believed to be the case for the other aromatic solutes considered in this study, including the substituted anilines, and hydroquinone and catechol and their alkyl substituents. Ring-bound nitrogen-containing aromatic solutes (methylimidazole, quinoline, and 5,5-dimethylhydantion) were unreactive with manganese dioxide at pH 6.4. The order of the reactivity of para-substituted anilines was methoxy >> methyl > chloro > carboxy >> nitro; the relative reactivity of these compounds correlated with the solute's half-wave potential and Hammett constant.

Concentrations and fluxes of polycyclic aromatic hydrocarbons and polychlorinated biphenyls across the air-water interface of Lake Superior

Abstract: Concentrations of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were measured in the atmosphere and surface waters of Lake Superior to estimate the direction and magnitude of their fluxes across the air-water interface. Atmospheric PAH concentrations ({Sigma}(PAH) = 3.8 {plus minus} 1.7 mg/m{sup 3}, 13 PAHs) were typical of levels found in continental background air. Atmospheric PCB concentrations (x = 1.2 ng/m{sup 3}) have remained relatively constant over the Great Lakes during the past 10 years despite lower PCB loadings. PCB congener fugacity gradients suggest PCB volatilization from Lake Superior's surface waters in August 1986. Mean volatilization fluxes of total PCBs (19 ng/m{sup 2}{center dot}day) are similar to estimates of gross atmospheric deposition to the lake, supporting the hypothesis of nonequilibrium, steady-state PCB exchange across the air-water interface. PAH fluxes could not be calculated due to uncertainties in PAH Henry's law constants.

Transformations of selenium as affected by sediment oxidation-reduction potential and pH.

Abstract: Etude en laboratoire de l'influence du potentiel redox et du pH des sediments sur la solubilite, la speciation et la volatilisation du selenium

Effect of ten quaternary ammonium cations on tetrachloromethane sorption to clay from water

Abstract: The mineral surface of Wyoming bentonite (clay) was modified by replacing inorganic ions by each of 10 quaternary ammonium compounds, and tetrachloromethane sorption to the modified sorbents from water was studied. Tetrachloromethane sorption from solution to clay modified with tetramethyl-, tetraethyl-, benzyltrimethyl-, or benzyltriethylammonium cations generally is characterized by relatively high solute uptake, isotherm nonlinearity, and competitive sorption (with trichloroethene as the competing sorbate). For these sorbents, the ethyl functional groups yield reduced sorptive capacity relative to methyl groups, whereas the benzyl group appears to have a similar effect on sorbent capacity as the methyl group. Sorption of tetrachloromethane to clay modified with dodecyldimethyl(2-phenoxyethyl)-, dodecyltrimethyl-, tetradecyltrimethyl-, hexadecyltrimethyl-, or benzyldimethylhexadecylammonium bromide is characterized by relatively low solute uptake, isotherm linearity, and noncompetitive sorption. For these sorbents, an increase in the size of the nonpolar functional group(s) causes an increase in the organic carbon normalized sorption coefficient (K{sub oc}).

Hazardous wastes from large-scale metal extraction. A case study

Abstract: Caracterisation des types de pollution (primaire, secondaire et tertiaire) resultant de l'extraction de minerais a grande echelle. Discussion des impacts sur la geochimie, l'hydrologie, l'environnement et la sante humaine

Mobility of plutonium and americium through a shallow aquifer in a semiarid region

Abstract: Treated liquid wastes containing traces of plutonium and americium are released into Mortandad Canyon, within the site of Los Alamos National Laboratory, NM. The wastes infiltrate a small aquifer within the canyon. Although laboratory studies have predicted that the movement of actinides in subsurface environments will be limited to less than a few meters, both plutonium and americium are detectable in monitoring wells as far as 3,390 m downgradient from the discharge. Between the first and last monitoring wells (1.8 and 3.4 km from the discharge), plutonium concentrations decreased exponentially from 1,400 to 0.55 mBq/L. Americium concentrations ranged between 94 and 1,240 mBq/L, but did not appear to vary in a systematic way with distance. Investigation of the properties of the mobile actinides indicates that the plutonium and part of the americium are tightly or irreversibly associated with colloidal material between 25 and 450 nm in size. The colloidally bound actinides are removed only gradually from the groundwater. The fraction of the americium not associated with colloids exists in a low molecular weight form (diameter, {<=} 2 nm) and appears to be a stable, anionic complex of unknown composition. The mobile forms of these actinides defeat the forces that normallymore » act to retard their movement through groundwater systems.« less

Kinetics of selenate and selenite adsorption/desorption at the goethite/water interface

Abstract: Kinetics and mechanisms of selenate and selenite adsorption/desorption at the goethite/water interface were studied by using pressure-jump (p-jump) relaxation with conductivity detection at 298.15 K. A single relaxation was ascribed to SeO{sub 4}{sup 2{minus}} on a surface site through electrostatic attraction accompanied simultaneously by a protonation process. The intrinsic rate constant for adsorption (log k{sub 1}{sup int} = 8.55) was much larger than that for desorption (log k{sub 1{minus}}{sup int} = 0.52). The intrinsic equilibrium constant obtained from the kinetic study (log K{sub kinetic}{sup int} = 8.02) was of the same order of magnitude as that obtained from the equilibrium study (log K{sub model}{sup int} = 8.65). Unlike SeO{sub 4}{sup 2{minus}}, selenite adsorption on goethite produced two types of complexes, XHSeO{sub 3}{sup 0} and XSeO{sub 3}{sup {minus}}, via a ligand-exchange mechanism. Double relaxations were attributed to two reaction steps. The first step was the formation of an outer-sphere surface complex through electrostatic attraction. In the second step, the adsorbed selenite ion replaced a H{sub 2}O from the protonated surface hydroxyl group and formed an inner-sphere surface complex.

Effect of pH, temperature, and concentration on the adsorption of cadmium on goethite

Abstract: L'adsorption des ions cadmium sur FeOOH est etudiee en fonction de la temperature, du PH de la solution et de la concentration en ion. Les isothermes d'adsorption et la chaleur d'adsorption sont mesurees

Determination of polycyclic aromatic hydrocarbons in urban street dusts and their source materials by capillary gas chromatography

Abstract: Molecular distributions of polycyclic aromatic hydrocarbons (PAHs) in street dust samples collected from the Tokyo metropolitan area were determined by capillary gas chromatography following HPLC fractionation. Sixty-four compounds including three- to six-ring PAHs and sulfur heterocyclics were identified by capillary GC/MS. Total PAH concentrations were in the range of a few micrograms per gram of dust. The source materials (automobile exhaust, asphalt, fuel-oil combustion products) were also analyzed. The PAH profile, especially relative abundance of alkyl-PAHs and sulfur-containing heterocyclics, indicated that PAHs in the street dusts on the heavily trafficked streets are strongly affected by automobile exhaust and those in the residential area have a somewhat more significant contribution from combustion products in stationary sources. With both types of dusts, asphalt is through to contribute only a minor part of their PAHs.

Mercury speciation in surface freshwater systems in California and other areas

Abstract: Mercury concentrations and speciation were determined in surface water samples from lakes and rivers in California and other areas. The freshwater systems studied ranged from a pristine alpine lake to a system with Hg-contaminated sediments. Dissolved organo-Hg compounds accounted for a majority (up to 89%) of the dissolved Hg in some lakes. Mercury concentration and speciation patterns in rivers were similar to that for lakes. The total Hg levels obtained in this present work, using clean sampling and analytical technologies, were considerably lower than most historical reports

Binding of metal ions by particulate biomass derived from Chlorella vulgaris and Scenedesmus quadricauda

Abstract: Cette propriete de lier les metaux tels que l'argent, le cuivre, le cadmium et le zinc permet leur elimination des eaux usees industrielles

Occurrence, distributions, and transport of herbicides and their degradation products in the Lower Mississippi River and its tributaries

Abstract: Les resultats de cette etude montrent que plusieurs herbicides derives de la triazine et chloroacetanilide ainsi que leurs produits de degradation contaminent les eaux du bas Mississipi et de ses affluents

Atrazine and other s-triazine herbicides in lakes and in rain in Switzerland

Abstract: Les resultats de cette etude montrent que la totalite des 18 lacs suisses controles contiennent des quantites detectables de certains herbicides derives de la s-triazine

Estimating Partitioning and Transport of Organic Chemicals in the Foliage/Atmosphere System: Discussion of a Fugacity-Based Model

Abstract: The air-to-vegetation pathway may substantially contribute to human and food-chain exposure to organic chemicals since the surface area of the above-ground parts of vegetation by far exceeds the area the plants are growing on. A model for assessing the atmosphere-to-vegetation transfer of persistent organic chemicals is discussed. It is based on the fugacity concept and uses the 1-octanol/ water and cuticle/water partition coefficients, aqueous solubility, and the saturation vapor pressure of the chemicals as input data. Equilibrium concentrations in plant tissues and air-to-vegetation bioconcentration factors can be estimated. Further, the model permits prediction of the compartment(s) in vegetation where a given chemical will preferentially accumulate. An approach for assessing semiquantitatively the potential for (re)volatilization of organics from leaves is also suggested. Various applications of the model are shown for reference compounds of widely differing physicochemical properties.

Assessing total human exposure to contaminants. A multidisciplinary approach

Abstract: Through multidisciplinary approaches, the science of exposure has the potential to link environmental measurements and model predictions for sources transport and fate with the results of dose calculations made from toxicological data and environmental science health effects studies. Integrated models for assessing exposure and dose appear to require seven basic steps: (1) identify agents; media and routes of exposure; (2) identify target tissue and routes of entry; (3) identify the uncertainty in each data base; (4) develop a toxicokinetic model for the agent and the target tissues; (5) develop a quantitative pharmacodynamic model of the effects caused by the agent in the target tissue; (6) design a strategy to collect the appropriate exposure data; and (7) apply and validate models to estimate tissue concentration and exposure index and analyze epidemiological data. Continued research will improve the scientific basis required for conducting human exposure measurement and modeling studies and for making judgments on what contaminants in what settings require exposure reduction strategies. 60 refs., 1 fig., 1 tab.

Apparent partition coefficients of 15 carbonyl compounds between air and seawater and between air and freshwater ; implications for air-sea exchange

Abstract: Apparent partition coefficients (K*, in M/atm) of 15 carbonyl compounds between water and air were determined as a function of temperature, salinity, and pH, using a bubble column technique. Values for K* decrease with increasing carbon number of alkanals; e.g., at 25{degree}C apparent partition coefficients between air and seawater range from 3,710 for formaldehyde and 13.1 for acetaldehyde to 0.181 for decanal. Where overlap exists, their data are in good agreement with literature values. Log K* was found to be highly temperature dependent, varying linearly with 1/T for all compounds studied. The salinity effect on K* increases with increasing molecular weight; K*(seawater)/K*(freshwater) ratios range from close to 1 for formaldehyde and acetaldehyde to less than 0.3 for nonanal and decanal. The effect of pH in the range of 4-8 on K* was found to be negligible. This study presents the most complete data set of carbonyl partition coefficients to date and should facilitate modeling of exchange of these compounds between gas and aqueous phases. Some implications of their results for air-sea exchange of carbonyl compounds are discussed.