1. Simultaneous Airborne Measurements of BrO, HOBr, BrCl and Br 2 in the Tropics: Inorganic Halogens and Subsequent O 3 Depletion Michael Le Breton, Jennifer Muller, Kimberley Leather, Thomas Bannan, Steve Andrews, Shallcross, Asan Bacak & Carl Percival

2. Outline Instrumental setup - CIMS Data coverage Data results Modelling vs measured SS O 3 depletion

3. Data coverage FlightdurationCIMS dataQCL dataSP-2Notes B82303:05 Data still needs to be worked up B82403:17 QCL Calibration needs to be worked on B82502:42 B82603:3704:3703:37 B82703:1304:1303:13 B82803:0500:0003:05 Power failure pre flight so no CIMS B82903:2004:2003:20 B83004:2305:2304:23 B83104:1005:1004:10 B83203:4504:4503:45 B83304:00 B83404:00 B83502:00 QCL Calibration needs to be worked on B83603:55 QCL Calibration needs to be worked on B83703:45 B83802:2000:0002:20 Overheating has affected CIMS data - being worked on B83903:4900:0003:49 Overheating has affected CIMS data - being worked on B84004:00 QCL Calibration needs to be worked on B84103:42 B84203:46 B84303:40 B84403:35 B84503:45 B84604:00 TOTAL84:1573:0283:0084:15 10 minute segments of QCL flights lost where software crashed %100%87%96%100%

4. Chemical Ionisation A - + B  B - + A reagent ion molecule to detect I - + HCOOH → [HCOOH].I - Soft ionisation High sensitivity Flexible ionization Detect both + and – ions ppt, LODs Soft ionisation High sensitivity Flexible ionization Detect both + and – ions ppt, LODs

5. Manchester CIMS 22 Torr0.24Torr10 -3 Torr10 -4 Torr

6. CIMS measurements speciesseen asmasssensitivity (ion counts per ppt)LOD (ppt) Formic acidI.HCOOH1733525 Nitric acidI.HNO31902536 Hydrogen chlorideI.HCl1621.84 Butanoic acidI.C3H7COOH2151525 Nitrogen pentoxideNO362271.9 Nitryl chlorideI.ClNO22083433 Hydrogen cyanideI.HCN154330.4 Bromine monoxideI.BrO222/224160.8 Hypobromous acidI.HOBr.H2O241500.1 Bromine monochlorideBrCl113500.1 BromineI.Br22871000.1 I -.HOBr.H 2 O BrCl -

7. BrO calibration NO HOBr, BrCl and Br 2 all calibrated on FT 1. BrCl – Cl 2 and Br 2 gas mixture equilibrate 2. HOBr – AgNO 3 (liberates Br) Mix with CCl 4 (Removes Br 2 ) Quantify with H + and Br - 3. Br 2 – gas mixture and perm tube

8. Time series example

9. B823 transit

10. BrO and O 3 data

11. Altitude profiles

12. Model

13. O 3 loss reactions 1.Br + O 3 → BrO + O 3 2.Br + DMS → products 3.BrO + HO 2 → HOBr 4.BrO + DMS → Br + DMSO 5. HOBr + hν → OH + Br 6.Br 2 + hν → Br + Br 7. BrCl + hν → Br + Cl 8.HOBr (wet deposition)→ 9.BrCl (wet deposition)→ 10.Br 2 (wet deposition)→ 11.O 3 + HO 2 → OH + 2O 2 12O 3 + hν → O( 1 D) + O 2 13aO( 1 D) + N 2 → O( 3 P) + N 2 13bO( 1 D) + O 2 → O( 3 P) + O 2 13cO( 1 D) + H 2 O → OH + OH 14BrO + CH 3 O 2 → HOBr + CH 2 OO 15aCH 2 OO → OH + HO 2 15bCH 2 OO + H 2 O → HCOOH + H 2 O

14. O 3 loss reactions Consider the four loss reactions 11. O 3 + HO 2 → OH + 2O 2 16. O 3 + OH → HO 2 + O 2 12O 3 + hν → O( 1 D) + O 2 13cO( 1 D) + H 2 O → OH + OH 1.Br + O 3 → BrO + O 3 O 3 HO2+O3 = k 11 [HO 2 ][O 3 ] O 3 OH+O3 = k 16 [OH][O 3 ] O 3 Br+O3 = k 1 [Br][O 3 ] F1 =k 13C[H2O] / k 13a[N2] + k 13b[O2] + k 13C[H2O] O 3O1D = F1*J 12 [O 3 ]

15. SS approx for HO 2 We don’t know the wet deposition rate underestimate of HO 2 or lower limit. [HO 2 ] = J 5 [HOBr] / K 3 [BrO] SS3 [HOBr] = k 3 [BrO][HO 2 ] / J 5 + J 8 ] SS1 [HO 2 ] = J 5 [HOBr] / K 3 [BrO] SS2

16. BrO Altitude profiles

17. CIMS case studies

18. Summary and further work A suite of inorganics simultaneously measured in tropics on aircraft Also have measurements of formic, butanoic, nitric, HCN, ClNO 2 and N 2 O 5 CIMS measurements indicate model underestimates BrO by a factor of 3/4 Other inorganic halogens underestimated by similar factor Free Br dominated by inorganic photolysis Inorganic halogen photolysis responsible for up to 20% O 3 loss in TMBL