Unexpectedly high concentrations of molecular chlorine in coastal air

Abstract

Nature © Macmillan Publishers Ltd 1998 8 letters to nature NATURE | VOL 394 | 23 JULY 1998 353sites. Clearly, differences in catalyst loading must also be taken into account when assessing the relative activities of the catalytic sites.The technique described here could be extended to monitor multiple reaction products, and thus could also be used to acquire information on catalyst selectivity. This could be accomplished by using different laser frequencies to sequentially generate the REMPI signals of different products. The REMPI signals could then be converted into absolute concentrations, using calibration standards, for the determination of selectivities. In addition, the technique developed should be useful in the study of issues related to the operational lifetimes of catalysts, their resistance to poisoning, their regeneration and their loss during operation. Ⅺ

Reactive chlorine in the marine boundary layer in the outflow of polluted continental air: A model study

“…[10] In the BASE run, Cl 2 reaches nighttime mixing ratios of 50 pmol mol À1 after one day, and even higher values after two and three days (90 and 60 pmol mol À1 ), values that are similar in magnitude to those measured by Spicer et al [1998]. For a model start at noon, Cl 2 mixing ratios reach a maximum of 20 pmol mol À1 during the first night (i.e.…”

“…Another possibility for the production of Cl 2 would be the reaction between OH and Cl À on aerosol surfaces [Knipping et al, 2000;Knipping and Dabdub, 2002], in addition to the autocatalytic mechanism involving oxidation of Cl À by HOCl/HOBr in acidified sea salt aerosol [e.g., Sander and Crutzen, 1996;Vogt et al, 1996]. Using a similar method as Spicer et al [1998], Finley and Saltzman [2006] measured Cl 2 in coastal urban air in Irvine, California, reporting mixing ratios up to 20 pmol mol À1 with a 2-month average of 3.5 pmol mol À1 .…”

“…[3] Spicer et al [1998] reported the first direct detection of Cl 2 in the MBL by ionization tandem mass spectrometry. They measured nighttime Cl 2 levels below 10 pmol mol À1 up to 150 pmol mol À1 at a coastal site on Long Island in marine air masses.…”

A kinetics and mechanistic study of the atmospherically relevant reaction between molecular chlorine and dimethyl sulfide (DMS)

“…Also it was important to check the range of partial pressures of the gases in the flow tube over which the photoelectron signal, as measured with this set-up, was linear. The minimum detection limits for Ar, DMS and Cl 2 were estimated as 1x10 11 , 3.5x10 11 and 4x10 11 molecules cm -3 respectively. Also for these three gases the pressure range over which the photoelectron signal was linear with pressure in the flow tube was 1x10 11 -1.1x10 14 , 3.5x10 11 -1.6x10 13 and 4x10 11 -1x10 14 molecules cm -3 respectively.…”

“…This is produced at night, as well as during the day, from heterogeneous reactions of ozone with wet sea-salt and is enhanced by the presence of ferric ions (10). Employing a high-pressure chemical ionization mass spectrometry technique, Spicer et al (11) measured Cl 2 levels ranging from <15 to 150 pptv. Nighttime Cl 2 mixing ratios were in the range 40-150 pptv, with the highest value being observed near mid-night, which dropped to 15 pptv in day-light.…”