Showing papers in "Environmental Science & Technology in 1987"
TL;DR: This article summarizes and systematizes the current understanding of abiotic and biotic chemistry of halogenated aliphatic compounds and reveals broad patterns of transformation in biological systems in general.
Abstract: This article summarizes and systematizes the current understanding of abiotic and biotic chemistry of halogenated aliphatic compounds. Knowledge of abiotic transformations can provide a conceptual framework for understanding biologically mediated transformations. Most abiotic transformations are slow, but they can still be significant within the time scales commonly associated with ground water movement. In contrast, biotic transformations typically proceed much faster, provided that there are sufficient substrate and nutrients and a microbial population that can mediate such transformation. Recent studies, which describe transformations of halogenated aliphatic compounds in microbial and mammalian systems, are also discussed. These studies reveal broad patterns of transformation in biological systems in general. 114 references, 8 figures, 12 tables.
975 citations
TL;DR: In this paper, a modified EPICS procedure for measuring Henry's constants is proposed, wherein the original assumption of equal solute mass additions to bottle pairs has been eliminated via a gravimetric accounting, resulting in increased precision.
Abstract: A modification to the EPICS procedure for measuring Henry's constants is proposed, wherein the original assumption of equal solute mass additions to bottle pairs has been eliminated via a gravimetric accounting, resulting in increased precision. The modified procedure was applied to 13 volatile C/sub 1/ and C/sub 2/ chlorinated hydrocarbons at temperatures from 10 to 35/sup 0/C, representing a range in dimensionless Henry's constant (H/sub c/) of from 0.05 to 1.8. The mean coefficient of variation (CV) in Henry's constant was 3-4%; however, by employment of greater differentials in liquid volumes within bottle pairs, CV may be reduced to an estimated 2.5-3.5%. Precision deteriorates markedly at very low Henry's constants (i.e., H/sub c/ < 0.1). Dilute aqueous mixtures of volatile solutes (with methanol also present) were employed in these measurements of Henry's constant. Comparison with previous results from single-solute assays supports the use of mixtures - at least within the range explored here. The effects of ionic strength on apparent Henry's constants were evaluated for six of the compounds, with KCl concentrations up to 1.0 M. The practical impact of ionic strength appears to be minimal. Salting-out coefficients (k) ranged from 0.107 to 0.213 L mol/sup -1/ at 20/sup 0/C.more » 8 references, 5 figures, 3 tables.« less
785 citations
TL;DR: In this paper, low molecular weight dicarboxylic acids (C/sub 2/-c/sub 10/) were analyzed in Los Angeles air and auto exhaust, as well as greenhouse air, soil, dust, and bog sediment samples, as dibutyl esters by gas chromatography and gas chromalysis-mass spectrometry with fused silica capillary columns.
Abstract: Low molecular weight dicarboxylic acids (C/sub 2/-C/sub 10/) were analyzed in Los Angeles air and auto exhaust, as well as greenhouse air, soil, dust, and bog sediment samples, as dibutyl esters by gas chromatography and gas chromatography-mass spectrometry with fused silica capillary columns. In the Los Angeles ambient atmosphere, 19 dicarboxylic acids in the range C/sub 2/-C/sub 10/ were identified, including straight-chain, branched-chain, cis- and transunsaturated, and aromatic acids. Oxalic acid is the dominant species, followed by succinic, malonic, maleic, glutaric, adipic, and phthalic acids. Total concentration of C/sub 2/-C/sub 10/ diacids detected in the ambient atmosphere ranged from 5.5 to 21.2 nmol/m/sup 3/ (average 12.2 +/- 6.1 nmol/m/sub 3/). By contrast, gasoline and diesel exhaust samples, collected under idling conditions, showed that distributions of the diacids are similar to those of air samples, but their concentrations are 28 (gasoline) and 144 (diesel) times higher than the average concentration of atmospheric diacids. These results indicate that engine exhaust is an important source of diaids in the urban atmosphere. 13 references, 3 figures. 1 table.
576 citations
TL;DR: The oxidation kinetics of butyl chloride, nitrobenzene, anisole, and methylmercury in the presence of hydroxyl radical (OH) scavengers were used to determine the rate and quantum efficiency for production of OH from irradiated nitrate ions in water.
Abstract: The oxidation kinetics of butyl chloride, nitrobenzene, anisole, and methylmercury in the presence of hydroxyl radical (OH) scavengers were used to determine the rate and quantum efficiency for production of OH from irradiated nitrate ions in water. The experiments were conducted under steady-state irradiations with monochromatic radiation (313 nm) and with sunlight. The mean quantum efficiency for OH production at 313 nm rises from 0.013 +/- 0.002 at 20 /sup 0/C to 0.017 +/- 0.003 at 30 /sup 0/C in the pH range 6.2-8.2. Results of this study are used to estimate nitrate-induced photooxidation rates of trace organic chemicals under a variety of environmental conditions. 27 references, 6 figures, 2 tables.
530 citations
TL;DR: The binding of pyrene to dissolved humic and fulvic acids is modified to a significant extent by the degree of aromaticity in the humic material, which suggests that the structure and composition of the humics material should be considered in any attempts to model the transport and fate of hydrophobic organic pollutants in aquatic environment.
Abstract: Partition coefficients for the binding of pyrene to 14 different humic and fulvic acids were determined. Each of the humic materials was characterized by infrared and ultraviolet absorbance, elemental analysis, and, for four samples, /sup 13/C solid-state NMR. Partition coefficients normalized to the fraction of organic carbon in the humic material (K/sub oc/'s) varied by as much as a factor of 10 depending upon the humic material. The magnitude of the K/sub oc/ values correlated strongly with three independent measures of the degree of aromaticity in the humic material. Thus, the binding of pyrene to dissolved humic and fulvic acids is modified to a significant extent by the degree of aromaticity in the humic material. This also suggests that the structure and composition of the humic material should be considered in any attempts to model the transport and fate of hydrophobic organic pollutants in aquatic environment. 32 references, 6 figures, 2 tables.
511 citations
TL;DR: Evidence indicates that the fraction of oxide surface sites occupied by substituted phenols is quite low, and a mechanism for the surface chemical reaction has been postulated to account for these effects.
Abstract: Kinetics of the reaction of manganese(III/IV) oxides with 11 substituted phenols were examined in order to assess the importance of manganese oxides in the abiotic degradation of phenolic pollutants. At pH 4.4, 10/sup -4/ M solutions of substituted phenols reduced and dissolved synthetic manganese oxide particles in the following order: p-methylphenol > p-ethylphenol > m-methylphenol > p-chlorophenol > phenol > m-chlorophenol > p-hydroxybenzoate > o-hydroxybenzoate > 4'-hydroxyacetophenone > p-nitrophenol. Rates of reductive dissolution generally decrease as the Hammett constants of ring substituents become more positive, reflecting trends in the basicity, nucleophilicity, and half-wave potential of substituted phenols. Evidence indicates that the fraction of oxide surface sites occupied by substituted phenols is quite low. The apparent reaction order with respect to (H/sup +/) is not a constant but varies between 0.45 and 1.30 as the pH range, phenol concentration, and phenol structure are varied. A mechanism for the surface chemical reaction has been postulated to account for these effects.
486 citations
TL;DR: The residual 1,2-dibromoethane (EDB) was found in agricultural topsoils up to 19 years after its last known application as mentioned in this paper, and the residual EDB was highly resistant to both mobilization (desorption into air and water) and microbial degradation in contrast to freshly added EDB.
Abstract: The soil fumigant 1,2-dibromoethane (EDB) was found in agricultural topsoils up to 19 years after its last known application. This residual EDB was highly resistant to both mobilization (desorption into air and water) and microbial degradation in contrast to freshly added EDB. Release of the residual EDB into aqueous solution was extremely slow at 25/sup 0/C but highly temperature dependent. Treatment of release as a radial diffusion process yielded effective intraparticle diffusivities of (2-8) x 10/sup -7/ cm/sup 2//s and half-equilibration times in a 1:2 soil-water suspension of 2-3 decades at 25/sup 0/C. Aerobic degradation of residual EDB by indigenous microbes was negligible after 38 days compared to rapid removal and mineralization of added (/sup 14/C)EDB. The release of residual EDB was greatly enhanced by pulverization of the soil. The results show that the residual EDB is trapped in soil micropores other than the interlayers of expandable clays where release is influenced by extreme tortuosity or steric restriction. 27 references, 7 figures, 2 tables.
480 citations
TL;DR: In this article, the authors studied the kinetics of aqueous Cr(III) to Cr(VI) by reaction with pyrolusite (..beta..-MnO/sub 2/(s)) were studied in aerated and deaerated solutions at 27/sup 0/C for pH 3.0-10.1, for 10/sup -4.7/-10/sup-3.0 where k = 2.0 (+- 1.8) for f/sub Cr/ less than or equal to 1.
Abstract: The kinetics of oxidation of aqueous Cr(III) to Cr(VI) by reaction with pyrolusite (..beta..-MnO/sub 2/(s)) were studied in aerated and deaerated solutions at 27/sup 0/C for pH 3.0-10.1, for 10/sup -4.7/-10/sup -3.4/ M Cr(III), and as a function of ..beta..-MnO/sub 2/(s) surface area to assess the possible effects on Cr transport in industrial waste materials. The oxidation of aqueous Cr(III) is not appreciably affected by dissolved oxygen, indicating that Cr(III) reacts directly with ..beta..-MnO/sub 2/(s) to produce Cr(VI) and not by catalyzed reactions with oxygen at the ..beta..-MnO/sub 2/(s) surface. In acidic solutions, the oxidation of aqueous Cr(III) is highly nonlinear with time, possibly because strong adsorption of the produced anionic Cr(VI) species limits the amount of Cr(III) species able to contact active oxidizing sites on the ..beta..-MnO/sub 2/(s) surface. The following expression is derived from the rate data for pH 3.0-4.7 that empirically account for the nonlinear rate by describing the reaction rate in terms of the fraction of Cr(VI) to total Cr, f/sub Cr/, remaining in solution: df/sub Cr/dt (s/sup -1/) = k(AV)(Cr/sub t/)/sup -1/(1.0 - f/sub Cr/)/sup 3.2 (+/- 0.8) for f/sub Cr/ less than or equal to 1.0 where k = 2.0 (+- 1.6) x 10/supmore » -3/ mol x m/sup -2/ x s/sup -1/, AV is the ..beta..-MnO/sub 2/(s) surface area to solution volume ratio in m/sup 2/ x L/sup -1/, and (Cr/sub t/) is the molar concentration of total dissolved Cr. In slightly acidic to basic solutions, the oxidation of aqueous Cr(III) is very slow and is limited by the low solubility of Cr(OH)/sub 3/(s). 19 references, 6 figures, 4 tables.« less
459 citations
TL;DR: The model calculations are in good agreement with the CrO 4S adsorption data for paired- and multiple-solute systems, however, the model calculations underestimate CrO4S advertisersorption when surface site saturation is approached.
Abstract: Chromate adsorption on amorphous iron oxyhydroxide was investigated in dilute iron suspensions as a single solute and in solutions of increasing complexity containing CO2(g), SO4S (aq), H4SiO4(aq), and cations (K , MgS , CaS (aq)). In paired-solute systems (e.g., CrO4S -H2CO3*), anionic cosolutes markedly reduce CrO4S adsorption through a combination of competitive and electrostatic effects, but cations exert no appreciable influence. Additionally, H4SiO4 exhibits a strong time-dependent effect: CrO4S adsorption is greatly decreased with increasing H4SiO4 contact time. In multiple-ion mixtures, each anion added to the mixture decreases CrO4S adsorption further. Adsorption constants for the individual reactive solutes were used in the triple-layer model. The model calculations are in good agreement with the CrO4S adsorption data for paired- and multiple-solute systems. However, the model calculations underestimate CrO4S adsorption when surface site saturation is approached. Questions remain regarding the surface interactions of both CO2(aq) and H4SiO4. The results have major implications for the adsorption behavior of CrO4S and other oxyanions in subsurface waters.
427 citations
TL;DR: L'ozone, utilise comme desinfectant ou comme oxydant, genere des sous-produits differents selon le procede de traitement employe selon l'habitat de traitation employe.
Abstract: L'ozone, utilise comme desinfectant ou comme oxydant, genere des sous-produits differents selon le procede de traitement employe
414 citations
TL;DR: Calculations indicate that CU(I) oxidation and FE(II) oxidation by H/ sub 2/O/sub 2/ are at least as important as nitrite photolysis as a source of OH radicals in the ocean.
Abstract: The oxidation of Fe(II) and Cu(I) and the reduction of Fe(III) and Cu(II) by hydrogen peroxide in sea water have been studied to understand their mechanisms and probable significance in the upper marine water column. At 10/sup -7/ M H/sub 2/O/sub 2/, a level commonly found in surface sea water, reaction with H/sub 2/O/sub 2/ is the dominant oxidation pathway for Fe(II). Reduction of Fe(III) by peroxide was not observed in the pH range 7-8. Reduction of Cu(II) and oxidation of Cu(I) by H/sub 2/O/sub 2/ contribute to a dynamic redox cycling of that element in the upper water column. Calculations based on these data indicate that CU(I) oxidation and FE(II) oxidation by H/sub 2/O/sub 2/ are at least as important as nitrite photolysis as a source of OH radicals in the ocean. 47 references, 6 figures, 2 tables.
TL;DR: In this paper, the authors investigated the effect of dissolved organic matter on the solubility enhancement of organic solutes on the basis of the use of commercial humic acids and showed that the effect varies with the molecular composition of the aquatic humic materials.
Abstract: Water solubility enhancements of 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (p,p'-DDT), 2,4,5,2',5'-pentachlorobiphenyl (2,4,5,2',5'-PCB), and 2,4,4'-trichlorobiphenyl (2,4,4'-PCB) by dissolved organic matter have been studied with the following samples: (1) acidic water samples from the Suwannee River, Georgia, and the Sopchoppy River, Florida; (2) a humic extract of a nearly neutral pH water from the Calcasieu River, Louisiana; (3) commercial humic acids from the Aldrich Chemical Co and Fluka-Tridom Chemical Corp The calculated partition coefficients on a dissolved organic carbon basis (K/sub doc/) for organic solutes with water samples and aquatic humic extracts from this and earlier studies indicate that the enhancement effect varies with the molecular composition of the aquatic humic materials, The K/sub doc/ values with water and aquatic humic samples are, however, far less than the observed K/sub doc/ values obtained with the two commercial samples, by factors of about 4-20 In view of this finding, one should be cautious in interpreting the effects of the dissolved organic matter on solubility enhancement of organic solutes on the basis of the use of commercial humic acids 14 references, 3 figures, 2 tables
TL;DR: The new technique of flow FFF is capable of yielding detailed molecular weight information and appears to have considerable potential for investigating these important yet complex compounds.
Abstract: Flow field-flow fractionation (flow FFF) has been used to determine molecular weight distributions of extracted fulvic and humic acids from a variety of freshwater and terrestrial environments. Both number and weight molecular weight averages have been estimated. Some pronounced trends have emerged. Thus, fulvic acids are smaller than humic acids, and the order of increasing size and polydispersity of humates from different sources was aquatic < soil < peat bog < lignite coal. In addition, two highly colored natural waters were run by direct injection without the need for any sample pretreatment. Their molecular weight distributions were closest to that of the soil humate. The new technique of flow FFF is capable of yielding detailed molecular weight information and appears to have considerable potential for investigating these important yet complex compounds.
TL;DR: In this paper, the thermal behavior of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorined dibenzofurans (PC-DF) on fly ash from waste incinerators was studied at 300/sup 0/C under oxygen deficient and oxygen surplus conditions.
Abstract: The thermal behavior of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PC-DF) on electrostatic precipitator ash (fly ash) from waste incinerators was studied at 300/sup 0/C under oxygen deficient and oxygen surplus conditions. Under oxygen deficient conditions a dechlorination/hydrogenation reaction is observed that is catalyzed by fly ash. The addition of octaCDD and octaCDF to fly ash and subsequent heat treatment lead to the formation of mono- to heptaCDD/CDF. Under oxygen surplus conditions as increase in PCDD and PCDF is obtained as first described by Vogg and Stieglitz. On the basis of evidence presented, a mechanism for this fly ash catalyzed reaction is proposed, which starts with the formation of chlorine from metal chlorides and leads finally to a de novo synthesis of PCDD and PCDF. The findings reported will have consequences for the interpretation of PCDD/PCDF formation and decomposition in waste incineration facilities and will aid in minimizing PCDD and PCDF emission from such facilities.
TL;DR: The atmospheric chemistry and transport of nitrogen oxides and peroxyacetyl nitrate are explained and the role of PAN as a carrier and reservoir of nitrogen Oxides has received considerable attention.
Abstract: The atmospheric chemistry and transport of nitrogen oxides and peroxyacetyl nitrate are explained. Although most of the emissions of reactive nitrogen occur as nitric oxide, it is typically converted to nitrogen dioxide in minutes by reaction with ozone. Nitrogen dioxide in turn absorbs ultraviolet light at relatively long wavelengths and photolyzes rapidly, eventually reforming ozone. In recent years, the role of PAN as a carrier and reservoir of nitrogen oxides has received considerable attention. This possibility arose from the understanding that PAN exists in equilibrium with nitrogen dioxide.
TL;DR: It is clear that a variety of reactive atmospheric hydrocarbons (toluene, propylene, acetaldehyde, allyl chloride) can be converted into products that are potentially much more mutagenic than the reactants themselves.
Abstract: typical ambient allyl chloride concentrations are roughly 1000 times lower (18) than propylene concentrations. It is clear a t this point, however, that a variety of reactive atmospheric hydrocarbons (toluene, propylene, acetaldehyde, allyl chloride) can be converted into products that are potentially much more mutagenic than the reactants themselves. Much more work is necessary, however, to fully establish the potential human health effects brought about by exposure to atmospheric photooxidation products.
TL;DR: Data is presented on the oxidation of H/sub 2/S in water, seawater, and NaCl solutions as a function of temperature, pH, and ionic strength.
Abstract: The formation of H/sub 2/S occurs in a number of areas in natural waters.The production in pore waters and anoxic basins is due to biological processes while the production in hydrothermal systems is due to geochemical processes. At the interface between anoxic and oxic waters, large changes occur in the state of metals and nonmetals (1,2). This is due to the changes in the redox conditions, solubility conditions, and bacterial activity. Although one can question the importance of abiotic thermodynamic and kinetic processes at this interface, it is useful to use simple inorganic models to approximate the real system. Recently, researchers (3) have examined the thermodynamics and kinetics of the H/sub 2/S system in natural waters. From this review, it became apparent that large discrepancies existed in the rates of oxidation of H/sub 2/S in natural waters from various studies. Studies on the effect of various parameters such as temperature, salinity, and pH for seawater were nonexistent. In this paper data is presented on the oxidation of H/sub 2/S in water, seawater, and NaCl solutions as a function of temperature (5-65 /sup 0/C), pH (1-12), and ionic strength (I = 0-6 M). These results will hopefully fill some of themore » gaps and yield equations valid for most natural waters. 21 references, 8 figures, 4 tables.« less
TL;DR: In this paper, the fate of TCA in ground water is complicated by the different possible abiotic and biotic transformations that it may undergo, such as reductive dehalogenation to 1,1-dichloro-ethylene and chloroethane under methanogenic conditions.
Abstract: A common industrial solvent, 1,1,1-trichloroethane (TCA), is one of the most frequently found contaminants in ground water. The fate of TCA in ground water is complicated by the different possible abiotic and biotic transformations that it may undergo. Abiotic transformation of TCA can result in a mixture of 1,1-dichloro-ethylene (1,1-DCE) and acetic acid, as shown by others. This study confirms that TCA can be biotransformed by reductive dehalogenation to 1,1-dichloroethane (1,1-DCA) and chloroethane (CA) under methanogenic conditions. Also, reductive dehalogenation of 1,1-DCE to vinyl chloride (VC) is confirmed. This study demonstrates that these transformations can occur stoichiometrically. In addition, (/sup 14/C)TCA, (/sup 14/C)-1,1-DCA, (/sup 14/C)-1,1-DCE, (/sup 14/C)CA, and (/sup 14/C)VC were at least partially mineralized to /sup 14/CO/sub 2/ under similar methanogenic conditions.23 references, 3 figures, 4 tables.
TL;DR: In this article, the chemical species of dissolved selenium were examined in surface waters from three sites in the San Joaquin and Imperial Valleys of California, and the inorganic species selenate and selenite; nonvolatile organic selenides, including seleno amino acids and a dimethylselenonium ion; and the volatile methylated forms dimethyl selenide and dimethyl diselenide.
Abstract: The chemical species of dissolved selenium were examined in surface waters from three sites in the San Joaquin and Imperial Valleys of California. Six dissolved selenium species were identified: the inorganic species selenate and selenite; nonvolatile organic selenides, including seleno amino acids and a dimethylselenonium ion; and the volatile methylated forms dimethyl selenide and dimethyl diselenide. The occurrences of methylated selenium species in the aquatic environment has important implications regarding the biogeochemical behavior of selenium in natural aqueous systems. Laboratory studies indicate that the nonvolatile dimethylselenonium ion can be transformed into volatile dimethyl selenide at neutral pH, providing a pathway for the in situ production of dimethyl selenide in natural waters. Geochemical flux calculations indicate that outgassing of dimethyl selenide may be an important removal mechanism for dissolved selenium from aqueous systems. 22 references, 7 figures, 1 table.
TL;DR: The results of these tests demonstrate that the molecular connectivity model is a very accurate predictive tool for the soil sorption coefficients of a wide range of organic chemicals and that it can be confidently used to rank potentially hazardous chemicals and thus to create a priority testing list.
Abstract: This study was undertaken to test the ability of the molecular connectivity model to predict the soil sorption coefficients of polycyclic aromatic hydrocarbons (PAHs), alkylbenzenes, chlorobenzenes, chlorinated alkanes and alkenes, heterocyclic and substituted PAHs, and halogenated phenols. Tests performed on 31 such compounds clearly demonstrate that this simple nonempirical model accurately predicts the soil sorption coefficients for the above classes of compounds. Moreover, the model out performs the traditional empirical models based on 1-octanol/water partition coefficients or water solubilities in accuracy, speed, and range of applicability. Additional tests on approximately 160 polar and ionic compounds show that the above topological model plus a single semiempirical variable is capable of accounting for the soil sorption properties of nearly 95% of all organic chemicals whose soil sorption coefficients have been measured. The results of these tests demonstrate that the molecular connectivity model is a very accurate predictive tool for the soil sorption coefficients of a wide range of organic chemicals and that it can be confidently used to rank potentially hazardous chemicals and thus to create a priority testing list. 55 references, 5 figures, 7 tables.
TL;DR: Etude de l'effet d'une photolyse UV eclair laser sur des composes organiques dissous dans l'eau ou contenus dans le sol montre que l'electron hydrate joue un role important dans the persistance de polluants electronegatifs mais n'a pas d'effets notable sur the production of peroxyde d'hydrogene.
Abstract: Etude de l'effet d'une photolyse UV eclair laser sur des composes organiques dissous dans l'eau ou contenus dans le sol. Les resultats de cette etude montre que l'electron hydrate joue un role important dans la persistance de polluants electronegatifs mais n'a pas d'effet notable sur la production de peroxyde d'hydrogene
TL;DR: Arsenic added to sediment became associated with relatively immobile iron and aluminum compounds and was mobilized from sediment over both the short and long term.
Abstract: Fixation, speciation, and mobilization of sediment arsenic (As) during sediment-water interactions were studied. Emphasis was placed on transformation and fixation of As(V) in anaerobic sediment, long-term (6 months) release of naturally occurring and added As, and sediment properties affecting the mobilization of As(V), As(III), and organic As. Arsenic added to sediment became associated with relatively immobile iron and aluminum compounds. Addition of As(V) to sediments prior to anaerobic incubation also resulted in accumulation of As(III) and organic As in the interstitial water and exchangeable phases of anaerobic sediments. Arsenic was mobilized from sediment over both the short and long term. Short-tern releases were related to As concentrations in the interstitial water and exchangeable phases. Long-term net mass releases were related to sediment total iron, extractable iron, or CaCO/sub 3/ equivalent concentration. 52 references, 3 figures, 11 tables.
TL;DR: Overall composition was quite consistent among cycles and years, with some changes occurring in the 1981 and 1982 models, but mass emissions decreased with model year, showing the most significant decreases in latter years as the standards became more stringent.
Abstract: Emissions from automobiles have long been considered a prime source of pollutants involved in smog formation and ozone production. The reactive potential of the species emitted has been studied extensively, and many reactivity schemes have been proposed. Most of the data on the detailed composition of the emissions from automobiles were taken from new or prototype vehicles. This study was undertaken to ascertain the mass and the detailed hydrocarbon and aldehyde composition of emissions from vehicles actually driven by the public. Forty-six vehicles, 1975 through 1982 models, were tested by using the Federal Test Procedure driving cycle, the Hot Soak Evaporative Test, the New York City driving cycle, and the Crowded Urban Expressway driving cycle, also known as the Sulfate Cycle. Overall composition was quite consistent among cycles and years, with some changes occurring in the 1981 and 1982 models. Mass emissions decreased with model year, showing the most significant decreases in latter years as the standards became more stringent. Eighty-two individual hydrocarbons and 10 aldehydes are reported for each test condition. The ratio of hydrocarbons to oxides of nitrogen increased dramatically on the lower speed cycles.
TL;DR: In this article, a methodologie d'echantillonnage was proposed for determiner la teneur en nicotine de l'air, which was used in le cadre d'une etude epidemiologique du tabac.
Abstract: Methodologie d'echantillonnage pour determiner la teneur en nicotine de l'air. Celle-ci sera utilisee dans le cadre d'une etude epidemiologique du tabac
TL;DR: Adsorption is a fundamental process for separating inorganic and organic contaminants from waters and waste-waters Mathematical process models can facilitate the design of full-scale systems simply by reducing the number of pilot-scale tests required to evaluate various operating conditions and design parameters as mentioned in this paper.
Abstract: Adsorption is a fundamental process for separating inorganic and organic contaminants from waters and waste-waters Mathematical process models can facilitate the design of full-scale systems simply by reducing the number of pilot-scale tests required to evaluate various operating conditions and design parameters This paper provides an overview and analysis of certain contemporary elements and applications of adsorption process modeling Included is a discussion that expands upon considerations that described processes for removing dissolved organic contaminants from water In addition, this paper lays a foundation for more detailed descriptions of research developments in adsorber modeling
TL;DR: In this paper, a 3 compartiments utilisable for quantifier l'exposition des hommes aux composes volatiles organiques provenant du transfert de masse de l'eau de distribution vers l'air interieur.
Abstract: Presentation d'un modele a 3 compartiments utilisable pour quantifier l'exposition des hommes aux composes volatiles organiques provenant du transfert de masse de l'eau de distribution vers l'air interieur
TL;DR: The feasibility of recycling ferrihydrite in a metal adsorption process was investigated in this article, where the retention of metals in the solid does not interfere with sorption in subsequent cycles, within the range of concentrations investigated.
Abstract: The feasibility of recycling ferrihydrite in a metal adsorption process was investigated. In this process, metal ions are removed from dilute solution by sorption onto ferrihydrite and are then desorbed into a more concentrated solution at lower pH. The ferrihydrite thus becomes available for reuse in subsequent sorption operations. Copper, lead, nickel, zinc, cadmium, and chromium(III) can be quantitatively sorbed onto ferrihydrite at pH 9.5. Lowering the pH to 4.5 substantially desorbs the metals. However, for all metals except cadmium, a measurable fraction of the bound metal is not easily desorbed. This fraction increases with increasing pH and duration of the high-pH stage and increases more or less continuously in sequential cycles. The retention of metals in the solid does not interfere with sorption in subsequent cycles, within the range of concentrations investigated. This included retention of up to 0.7 mol of Cr(III)/mol of Fe in the adsorbent. This process has the potential to provide the advantages of sorption processes, including low residual soluble metal concentrations, moderate pH requirements, and simultaneous removal of several metals, without excessive sludge production.
TL;DR: The authors retrospectively reviewed the use of cancer risk estimates in prevailing federal standards and in withdrawn regulatory initiatives to determine whether any simple patterns emerge to correlate risk level with regulatory action, and show that there are definite patterns and a surprising degree of consistency in the federal regulator process.
Abstract: Various federal agencies are responsible for promulgating regulations and standards to protect the public from exposure to environmental carcinogens. Although many factors are considered in the decision to regulate a carcinogen, one important issue concerns the probability that individuals in an exposed population will develop cancer. What has not been clear, however, is the level of cancer risk that triggers regulation, or whether there is consistency within and between agencies in arriving at the risk decisions that underpin regulatory action. The authors retrospectively reviewed the use of cancer risk estimates in prevailing federal standards and in withdrawn regulatory initiatives to determine whether any simple patterns emerge to correlate risk level with regulatory action. The results show that there are definite patterns and a surprising degree of consistency in the federal regulator process.
TL;DR: For sewage sludge, which contains metals with similar chemical and physical properties such as Cr, Ni, Cu, Zn, Cd, and Pb, pyrolysis at 500-600/sup 0/C might prove suitable since no metals are released to the atmosphere and a char is produced that is well suited for disposal in an inorganic sanitary landfill.
Abstract: Raw and digested sewage sludge samples were pyrolyzed in order to investigate the partitioning of selected heavy metals during anoxic thermal treatment. Cr, Ni, Cu, Zn, and Pb were retained quantitatively in the char at temperatures up to 750 /sup 0/C. Cd compounds were reduced to Cd/sup 0/, which was volatilized at T > 600 /sup 0/C. Hg was completely evaporated at the lowest investigated pyrolysis temperature of 350 /sup 0/C. The metals contained in the char are highly immobile due to the well-buffered neutral to alkaline properties of the char. Thus for sewage sludge, which contains metals with similar chemical and physical properties such as Cr, Ni, Cu, Zn, Cd, and Pb, pyrolysis at 500-600/sup 0/C might prove suitable since no metals are released to the atmosphere and a char is produced that is well suited for disposal in an inorganic sanitary landfill. 6 figures, 5 tables.
TL;DR: An amorphous orange precipitate was ubiquitous in the acid stream beds and was intimately associated with algae at the most acid sites and relative sorption of cations decreased with decreasing water pH, but arsenic was almost completely scavenged from solution within a short distance from the sulfide sources.
Abstract: Acid mine drainage has acidified large volumes of water and added high concentrations of dissolved heavy metals to West Squaw Creek, a California stream draining igneous rocks of low-acid-neutralizing capacity. During mixing of the acid sulfate streams waters in the South Fork of West Squaw Creek with an almost equal volume of dilute uncontaminated water, Cu, Zn, Mn, and Al remained in solution rather than precipitating or adsorbing on solid phases. Changes in the concentration of these generally conservative metals could be used to determine relative flow volumes of acid tributaries and the main stream. An amorphous orange precipitate (probably ferric hydroxides or a mixture of ferric hydroxides and jarosite) was ubiquitous in the acid stream beds and was intimately associated with algae at the most acid sites. Relative sorption of cations decreased with decreasing water pH. However, arsenic was almost completely scavenged from solution within a short distance from the sulfide sources. 25 references, 5 figures, 4 tables.