摘要:

The determination of nitrate as nitrite in seawater remains the method of choice. The widely differing conditions recommended hitherto for the reduction of nitrate to nitrite with hydrazine sulphate (HS), and the consequent erratic results, are shown to be due primarily to the sensitivity of the reduction to uncontrolled non-equilibrium fluctuations in the concentration of oxygen in samples, standards and dilution water. Ca2+and Mg2+ions, also responsible for complete suppression of the reduction, were precipitated and further inactivated by pyrophosphate. Reduction by HS compares well with the cadmium reduction column and avoids the generation of cadmium-rich column effluent.

ISSN:0306-7319    

DOI:10.1080/03067319208027014

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Some polychlorinated and polymethylated dibenzothiophenes have been synthesized to serve as model compounds in environmental analysis. In order to obtain pure isomers, the synthesis mixtures have been fractionated with reversed-phase high performance liquid chromatography. In spite of a high sensitivity, mass spectrometry does not provide any reliable way to determine the precise structures of different isomers. Therefore,1H NMR spectroscopy has been utilized as an aid in their analysis. The structures for two isomeric tetramethyldibenzothiophenes could be suggested on the basis of their1H NMR spectra. Also some proposals for possible structures of two isomeric trimethyldibenzothiophenes and two fractions of chlorinated dibenzothiophenes are given. More structural isomers, however, need to be prepared for their unique structure determinations.

ISSN:0306-7319    

DOI:10.1080/03067319208027015

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Laboratory experiments are reported, aimed at monitoring the degradation of ionic alkyllead compounds in water in the dark, in daylight and with UV irradiation. A stepwise dealkylation in aqueous media is not supported by the simulations. It appears that trialkyllead (triAL) degradation does not give rise to appreciable formation of dialkyllead (diAL) but directly yields inorganic lead; on the other hand, dialkyllead species appear too stable to be involved as short-lived intermediates. Generally ethyllead compounds are observed to be more sensitive towards degradation than the corresponding methyllead compounds. The results are consistent with existing literature evidence.

ISSN:0306-7319    

DOI:10.1080/03067319208027016

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The stable nitrogen isotope composition of ammonium (NH+4) and nitrate (NO−3) ions in bulk precipitation and forest throughfall was determined at Walker Branch watershed, a low elevation site (340 m) in northeastern Tennessee, and in cloud water from Whitetop Mountain, a high elevation site (1680 m) in southwestern Virginia. Tests of the method used indicated that sample processing did not introduce significant isotopic fractionation in measurements of nitrogen isotope composition. Mean δ15N values for NH+4and NO−3in solutions of artificial rain were within 0.3%oof the mean δ15N values of nitrogen compounds used to make the solutions. Over a one-year period on Walker Branch watershed, the measured mean (± SD) δ15N value for NH+4in bulk precipitation and throughfall (− 3.4 ± 2.1%o) was significantly less than that for NO−3(+ 2.3 ± 2.4%o). The same relative pattern was observed in cloud water from Whitetop Mountain: mean (± SD) δ15N in cloud water NH+4was −5.5 ± 3.2%o; i.e., isotopically lighter than NO−3(+ 1.4±4.8%o). The isotopic composition of NH+4in bulk precipitation and throughfall on Walker Branch watershed and in cloud water at Whitetop Mountain was consistent with origination through the washout of atmospheric NH3. However, the origins of NO−3(gaseous versus aerosol precursors) could not be clearly established from δ15N measurements.

ISSN:0306-7319    

DOI:10.1080/03067319208027017

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The separation of 140 chlorobiphenyl (CB) congeners from technical polychlorinated biphenyl (PCB) mixtures was investigated on five narrow-bore (0.22–0.25 mm I.D.) gas chromatography (GC) columns with stationary phases representing a broad range of polarities: dimethylsiloxane (0.15 μm SIL-5, 50 m), 5% diphenyl dimethylsiloxane (0.26 μm SIL-8, 50 m), 14% cyanopropylphenyl 1% vinyl dimethylsiloxane (0.26 μm SIL-19, 50 m), bis-cyanopropyl phenylsiloxane (0.20 μm SIL-88, 50 m) and 1,2-dicarba-closo-dodecarborane dimethylsiloxane (0.1 μm HT-5, 25 m). Technical PCB mixtures (Aroclors) and authentic standards (totally 66 CBs) were injected on the narrow-bore columns and analyzed by GC-ECD and GC-MS. Peak assignments were based on experimental data together with published retention data and data on the quantitative composition of Aroclors.

ISSN:0306-7319    

DOI:10.1080/03067319208027018

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A recently introduced technique based on differential optical absorption spectroscopy (DOAS) was compared with conventional adsorption sampling and gas chromatography for the determination of aromatic hydrocarbons in air. Measurements were made in Switzerland and Sweden, at sites with benzene and toluene concentrations up to 20 and 40 μg m−3, respectively. The hydrocarbons determined originated mainly from traffic exhaust.

ISSN:0306-7319    

DOI:10.1080/03067319208027019

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0306-7319    

DOI:10.1080/03067319208027013

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor