Iodine

Other distribution data

Administrative data

Endpoint:

other distribution data

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Short-lived alkyl iodides and bromides at Mace Head, Ireland: Links to biogenic sources and halogen oxide production

Author:

Carpenter LJ, Sturges WT et al.

Year:

1999

Bibliographic source:

J Geophys Res, 104(D1), 1679–1689, doi:10.1029/98JD02746

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Automated in situ gas chromatograph/mass spectrometer (GC/MS) measurements of a range of predominantly biogenic alkyl halides in air, including CHBr3, CHBr2Cl, CH3Br, C2H5Br, CH3I, C2H5I, CH2ICI, CH2I2, and the hitherto unreported CH2IBr were made at MaceHead during a 3-week period in May 1997.

GLP compliance:

not specified

Results and discussion

Any other information on results incl. tables

CHBr3 and CHBr2Cl were detected in the ranges 1.9-16.3 pptv and 0.3-1.8 pptv, with mean mixing ratios of 6.27 and 0.83 pptv, respectively.CH3I, C2H5I, CH2ICI, CH2IBr, and CH2I2were all observed at Mace Head, although only CH3I mixing ratios were alwaysabove the detection limit (~0.02 pptv). C3H7I and CH3CHICH3 were monitored but not detected.

 

CH3I comprised on average 60% of the collective organic iodine mixing ratio but contributed to less than 3% of the total iodine atom flux into the surface layer at Mace Head. CH2I2, and to a lesser extent CH2IBr, was calculated to be the most important species controlling I atom input and on average CH2I2 and CH2IBr were present at 10-20% of the CH3I concentration. These compounds were a source of the IO radicals detected during the campaign. The data collected at Mace Head strongly suggest that macroalgae play an important role in the production of polyhalomethanes such as CHBr3, CH2IBr, CH2ICl, and CH2I2, which reached their highest concentrations in air masses influenced by the local shoreline. These short-lived compounds appeared to be rapidly destroyed in sunlit hours and generally exhibited maxima when low water occured at night. The link arises from coproduction of CHBr3 and CH2I2 by macroalgae fllowed by substitution of bromide into CH2I2 in seawater.

Applicant's summary and conclusion

Conclusions:

CH3I comprised on average 60% of the collective organic iodine mixing ratio but contributed to less than 3% of the total iodine atom flux into the surface layer at Mace Head. CH2I2, and to a lesser extent CH2IBr, was calculated to be the most important species controlling I atom input and on average CH2I2 and CH2IBr were present at 10-20% of the CH3I concentration. These compounds were a source of the IO radicals detected during the campaign. The data collected at Mace Head strongly suggest that macroalgae play an important role in the production of polyhalomethanes such as CHBr3, CH2IBr, CH2ICl, and CH2I2, which reached their highest concentrations in air masses influenced by the local shoreline. These short-lived compounds appeared to be rapidly destroyed in sunlit hours and generally exhibited maxima when low water occured at night.

Executive summary:

Automated in situ gas chromatograph/mass spectrometer (GC/MS) measurements of a range of predominantly biogenic alkyl halides in air, including CHBr3, CHBr2Cl, CH3Br, C2H5Br, CH3I, C2H5I, CH2ICI, CH2I2, and the hitherto unreported CH2IBr were made at MaceHead during a 3-week period in May 1997.

CH3I comprised on average 60% of the collective organic iodine mixing ratio but contributed to less than 3% of the total iodine atom flux into the surface layer at Mace Head. CH2I2, and to a lesser extent CH2IBr, was calculated to be the most important species controlling I atom input and on average CH2I2 and CH2IBr were present at 10-20% of the CH3I concentration. These compounds were a source of the IO radicals detected during the campaign. The data collected at Mace Head strongly suggest that macroalgae play an important role in the production of polyhalomethanes such as CHBr3, CH2IBr, CH2ICl, and CH2I2, which reached their highest concentrations in air masses influenced by the local shoreline. These short-lived compounds appeared to be rapidly destroyed in sunlit hours and generally exhibited maxima when low water occured at night. The link arises from coproduction of CHBr3 and CH2I2 by macroalgae fllowed by substitution of bromide into CH2I2 in seawater.