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Uptake of carbonyl sulfide by silver nitrate impregnated filters: implications for the analysis of low level atmospheric H 2 S
| Content Provider | Semantic Scholar |
|---|---|
| Author | David Cooper |
| Copyright Year | 2007 |
| Abstract | Measurements of atmospheric hydrogen exposure to elevated SO2 and 03, but concluded sulfide are often made by first collecting H2S on that these losses would not be significant at a paper filter impregnated with silver nitrate. ambient oxidant concentrations. No interference Using this technique on a recent shipboard study, has been found from the reduced sulfur compounds we observed anomalous breakthrough characteristics dimethyl sulfide, methane thiol, and carbon of sulfide, which caused us to suspect the disulfide (Jaeschke et al., 1980). To our presence of an artifact. We have investigated the knowledge, no one has tested œor interference from interaction of various sulfur species with these carbonyl sulfide, despite the fact that OCS is the filters as precursors for the artifact sulfide. most abundant sulfur gas in marine air, with Laboratory experiments indicate that OCS generates concentrations in the marine boundary layer ot 500 sulfide on the •ilters with an efficiency of 1-2% + 50 pptv (Khalil and Rasmussen, 1984). _ under conditions comparable to those used for In this paper we present our anomalous field field sampling in the marine boundary layer. The data and the results of laboratory ext•riments magnitude of the artifact increases with designed to study the interaction of OCS with increasing temperature and is insensitive to silver nitrate impregnated filters. The humidity and insolation. It appears likely that implications of these results for the analysis of OCS is responsible for our shipboard results. trace concentrations of atmospheric H2S are Since much of the data on H2S concentrations in discussed. marine air have been omtained with this technique, they are most likely in error, producing Methods overestimates of background H2S concentrations. Shipboard and laboratory measurements of H2S Introduction were made by a method essentially identical to that of Natusch et al. (1972). An air stream was A balance of the global sulfur cycle requires drawn through a silver nitrate impregnated filter knowledge of the contribution of both natural and (Whatman 41, 47 mm diameter), held in a Teflon PFA anthropogenic fluxes of sulfur compounds to the filter holder. The H2S is fixed on the filter as atmosphere. Hydrogen sulfide is a major component silver sulfide, which was extracted from the of biogenic sulœur emissions •rom both coastal and filter using 20 ml of 0.1 M sodium hydroxide/ terrestrial environments, primarily as a result of sodium cyanide solution. The sulfide was microbial suifate reduction in anoxic envir. ondetermined by the fluorescence quenching of dilute ments. Measurements of H2S in marine air (Slatt fluorescein mercuric acetate (FMA), using 100 ul et ai., 1978; Delmas and Servant, 1982; Herrmann of 20 uM •iA in 0.1 M NaOH in each analysis. A and Jaeschke, 1984) yielded concentrations which Turner Designs model 10-853 fluorometer was used suggest that there are substantial sources of H2S with a blue lamp and 10 nm bandpass filters at 500 in remote oceanic regions, and that these sources nm excitation and 520 nm emission wavelengths. may be important in the sulfur budget oœ the Routine sampling of background marine air at marine boundary layer. our maximum flow rate of 8 liter min -! required a All the reported measurements of low level sampling time of approximately one hour to give a concentrations of atmospheric hydrogen sulfide detection limit of 3 pptv. For the laboratory have relied on variations of the method of Natusch work, we increased the sampling times to give et al. (1972), which owes its popularity to its better precision at low sulfide concentrations. A high sensitivity and to the purported absence of detection limit of lower than one pptv was any known atmospheric interferents. Results of our achieved by sampling for several hours. field work, however, led us to believe that a low level positive interference was present. Axelro• •t al. (1969) had previously• reporte• no interference by 2 C1-, SO• 2-, PO• 3-, NO3, C2M302 -, CHO2-, CO3' , methyl acetate, ethano.1, acetone, acetamide, mercaptoethanoi, NH•OH, Mn 2+, .•.2+ • 2+ • 2+ .... 2+ •,-2+ • 2+ o 3+ K + IN1 , t•O , L,U , L,(/ , •' D , ]3e , •e , , a , In the laboratory experiments, screw cap test tubes (45 ml) sealed with Mininert Teflon valves were filled with an atmosphere of nitrogen, containing approximately 1 ppm OCS from a permeation tube. For these studies, measurements of carbonyl sulfide were made gas chromatographically using a 5' x 1/8" Teflon Tenax GC column (Alltech Assocslight fluoresence nhancement by Iand slight iates, Deerfield, IL) held isothermal at 40øC. N 2 quenching by Br-, SO• 2NO2cysteine and was used as the carrier gas at a flow rate of 20 cystine at elevated concentrations. Natusch et cm B min -1 Aliquots of gas were injected onto the . al. (1972) •ound no loss of H.S from •ilters column through a septum. A sulfur specific flame exposed toelevated NO2, and s•ight loss from photometric detector was used, which as a detection limit of approximately 2 picomoles S. Copyright 1987 by the American Geophysical Union. Calibration was performed by injecting microliter aliquots of a standard gas mixture (Scott Paper number 6L6463. Specialty Gases, Plumsteadville, PA) and using a 0094-8276/87/006L-6463503.00 permeation tube/mass tlow controller system. |
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| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
