ISSN:0730-7268    

DOI:10.1002/etc.5620101101

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe degradation of aromatic hydrocarbons (benzene, toluene, ethylbenzene,p‐xylene,o‐xylene, 1,3,5‐trimethylbenzene, and naphthalene) under anaerobic conditions was studied in column microcosms developed with aquifer material from the vicinity of a gasoline spill at Seal Beach, California. In one column, which did not receive any electron acceptors other than those naturally present (sulfate and carbon dioxide), more than 60% of the toluene was oxidized to CO2. The other six added substrates were not degraded when the toluene supply was constant. In another column, the addition of toluene was discontinued after 126 d, which coincided with the onset ofp‐xylene degradation. Addition of sulfate, the only electron acceptor that was detected, stimulated the transformation of toluene in batch expe

ISSN:0730-7268    

DOI:10.1002/etc.5620101102

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractGas chromatography with electrolytic conductivity detection and electron capture detection in combination with gas chromatography‐mass spectrometry, operated in the electron capture negative chemical ionization mode, were evaluated as techniques for the analysis of polychlorinated biphenyls in wastewater from an industrial facility. The specificity of the electrolytic conductivity detector reduced sample turnaround time because extracts could be analyzed without fractionation or cleanup Using a 2 L sample, this methodology had a quantification limit, based on Aroclor 1260, of 0.1 μg/L and a detection limit of approximately 0.03 μg/L The electron capture detector was subject to interferences from nonhalogenated compounds and required additional sample cleanup Electron capture negative chemical ionization gas chromatography‐mass spectrometry was highly specific and provided full mass spectra of polychlorinated biphenyl congeners at the same quantification limit. Effluents from the facility had polychlorinated biphenyl concentrations of 0.1 to 1

ISSN:0730-7268    

DOI:10.1002/etc.5620101103

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractDesorption of tetrachloroethene (TeCE) or 1,2‐dibromo‐3‐chloropropane (DBCP) from aquifer sediment (0.19% organic carbon) was monitored following sorption for 6 or 30 d in 100 μM aqueous solutions. The compounds were desorbed by a previously developed purge technique in which a third phase of Tenax GC® polymeric adsorbent beads provided a sink for desorbed chemical, thereby simulating desorption to infinite dilution. Sorbed concentrations in the sediments were quantified by hot acetone extraction of sacrificed replicates. More than 95% of the initial sorbed compound was desorbed within the first 4 d, but a persistent fraction (8–15 μg/kg, 0.4 to 1%) remained associated with the sediments for at least 35 d. The desorption curves were little affected by the prepurge sorption time. The results may rationalize the unexpectedly high sediment‐associated concentrations of a similar compound (1,2‐dibromoethane) in a long‐cont

ISSN:0730-7268    

DOI:10.1002/etc.5620101104

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractMathematical models for predicting the fate of pollutants in the environment require reactivity parameter values —that is, the physical and chemical constants that govern reactivity. Although empirical structure‐activity relationships have been developed that allow estimation of some constants, such relationships generally hold only within limited families of chemicals. Computer programs are under development that predict chemical reactivity strictly from molecular structure for a broad range of molecular structures. A prototype computer system called SPARC (SPARC Performs Automated Reasoning in Chemistry) uses computational algorithms based on fundamental chemical structure theory to estimate a variety of reactivity parameters (e.g., equilibrium/rate constants, UV‐visible absorption spectra, etc.). This capability crosses chemical family boundaries to cover a broad range of organic compounds. SPARC does not do “first principles” computation, but seeks to analyze chemical structure relative to a specific reactivity query in much the same manner in which an expert chemist would do so. Molecular structures are broken into functional units with known intrinsic reactivity. This intrinsic behavior is modified for a specific molecule in question with mechanistic perturbation models. To date, computational procedures have been developed for UV‐visible light absorption spectra, ionization pKa, hydrolysis rate constants, and numerous physical properties. This paper describes the logic of the approach to chemistry prediction and provides an overview of the computational procedures. Additional papers are in preparation describing in detail the chemical models and specific a

ISSN:0730-7268    

DOI:10.1002/etc.5620101105

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractAn active sampling method based on a solid‐phase collection medium was used to determine ammonia concentrations in indoor air. A weak cation exchange cartridge was used to collect ammonia, which was then eluted from the cartridge with 0.02MHCl and determined by cation exchange chromatography (CEC) with conductivity detection. The method was applied to quantify the ammonia in environmental tobacco smoke (ETS) and is compared to an impinger collection technique. The method was reproducible with a relative standard deviation of 2.0%. Percent recovery is about 98%. Analyses of samples collected in a variety of situations showed that ammonia concentrations vary. With a relatively short sampling time of 0.5 to 1 h, this procedure was capable of detecting ammonia above 5 μg m−3under the sampling condit

ISSN:0730-7268    

DOI:10.1002/etc.5620101106

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractAn analytical method was developed using C8solid‐phase extraction columns to extract carbaryl and malathion from well and pond water. Mean percent recovery over a concentration range of 1 μg/L to 10,000 μg/L was consistently between 80 and 100. Well‐water samples fortified with carbaryl and malathion were solid‐phase extracted, and analytes were stored on solid‐phase extraction columns at —4°C for 30 d without significant decomposition. The method was field‐tested by collecting pond water before and after an application of malathion. It provided significantly higher recovery of malathion than a liquid‐liquid extr

ISSN:0730-7268    

DOI:10.1002/etc.5620101107

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractCurrent environmental models use organism lipid concentrations to estimate maximum pollutant bioaccumulation potentials. This collaborative study has shown that significantly different lipid concentrations (3.5X) are found when using common, but different, extraction solvents and methods. Based on these variable lipid values, models that estimate tissue pollutant concentrations normalized to lipid will give significantly different bioaccumulation estimates. To reduce that variability, a standard lipid method needs to be developed or adopted.

ISSN:0730-7268    

DOI:10.1002/etc.5620101108

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractLaboratory tests were conducted to determine optimum conditions for benzene, toluene, ethylbenzene, and xylene (collectively known as BTEX) biodegradation by aquifer microorganisms under denitrifying conditions. Microcosms, constructed with aquifer samples from Traverse City, Michigan, were amended with selected concentrations of nutrients and one or more hydrocarbons. Toluene, ethylbenzene,m‐xylene, andp‐xylene were degraded to below 5 μg/L when present as sole source substrates; stoichiometric calculations indicated that nitrate removal was sufficient to account for 70 to 80% of the compounds being mineralized.o‐Xylene was recalcitrant when present as a sole source substrate, but was slowly degraded in the presence of the other hydrocarbons. Benzene was not degraded within one year, regardless of whether it was available as a sole source substrate or in combination with toluene, phenol, or catechol. Pre‐exposure to low levels of BTEX and nutrients had variable effects, as did the addition of different concentrations of ammonia and phosphate. Nitrate concentrations as high as 500 mg/L NO3‐N were slightly inhibitory. These data indicate that nitrate‐mediated biodegradation of BTEX at Traverse City can occur under a variety of environmental conditions with rates relatively independent of nutrient concentrations. However, the data reaffirm that benzene is recalcitrant under strictly anaerobic conditions in t

ISSN:0730-7268    

DOI:10.1002/etc.5620101109

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe toxicity of uranium to the tropical freshwater fishes —black‐banded rainbowfish (Melanotaenia nigrans), chequered rainbowfish (Melanotaenia splendida inornata), Mariana's hardy‐head (Craterocephalus marianae), delicate blue‐eye (Pseudomugil tenellus), reticulated perchlet (Ambassis macleayi), and purple‐spotted gudgeon (Mogurnda mogurnda) — and the cladocerans —Diaphanosoma excisum, Latonopsis fasciculata, Dadaya macrops, andMoinodaphnia macleayi— was measured under standard conditions in natural creek water. The fishes' 96‐h LC50s for uranium were 1.7 and 1.9 mg/L for 7‐ and 90‐d‐old black‐banded rainbowfishes, 2.66 and 3.46 mg/L for 7‐ and 90‐d‐old chequered rainbowfishes, 1.22 mg/L for Mariana's hardyhead, 0.73 mg/L for delicate blue‐eyes, 0.8 mg/L for reticulated perchlet, and 1.11 and 1.46 mg/L for 7‐ and 90‐d‐old purple‐spotted gudgeon. The cladocerans' 24‐h LC50s for uranium were 1.0 mg/L forDiaphanosoma excisum, 0.41 mg/L forLatonopsis fasciculata, 1.10 mg/L forDadaya macrops, and 1.29 mg/L forMoinodaphnia macleayi.Larval purple‐spotted gudgeon, reticulated perchlets, andMoinodaphnia macleayiwere identified as t

ISSN:0730-7268    

DOI:10.1002/etc.5620101110

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY