Reactive Halogens in the Marine Boundary Layer (RHaMBLe)
RHaMBLe sampling site location about 500 km off the coast of West Africa.
RHaMBLe – Reactive Halogens in the Marine Boundary Layer – is an integrated program sponsored mainly by the UK SOLAS program that aims to quantify impacts of marine halogen emissions on atmospheric composition by the direct observation of a range reactive halogen species (RHS) in the marine atmosphere. Emphasis is placed on the roles of halogens in oxidative processes and on secondary aerosol formation and transformations resulting from the cycling of RHS. RHaMBLe consists of two campaigns, one held in Roscoff, Brittany in July-August 2006 and the second in and around Cape Verde between 18th May and the 15th June 2007. The Observatory participated in the second campaign with funding provided by the National Science Foundation's Atmospheric Chemistry Program. This project is collaborative with the University of Virginia.
Space Grant intern and UNH undergrad Elena Crete changes a filter pack sample at the top of the tower. (click photo to enlarge)
University of Virginia grad student Mike Long services the mist chamber samplers on the tower. (click photo to enlarge)
The overall goal of the RHaMBLe – Cape Verde campaign is to characterize reactive halogen cycling in the eastern tropical North Atlantic marine boundary layer and its impact on oxidation processes through in situ intensive measurements and related modeling of all major participating species. The campaign was conducted at the Cape Verde Atmospheric Observatory on São Vicente island.
Staff Scientist Bob Deegan and UVA grad student Mike Long in the mobile RHaMBLe lab processing mist chamber samples for analysis by ion chromatography. UNH/MWO's two ion chromatography systems are to the left and two brought by UVA are in the back. (click photo to enlarge)
The specific research objectives of our component of the experiment are:
- Measure/calculate diel variability of principal reactant and product species relevant to inorganic halogen cycling in the MBL.
- Quantify source strengths and turnover rates of volatile and size-resolved particulate halogens.
- Evaluate potential influences of mineral aerosol on halogen cycling via modification of aerosol pH, possible activation reactions involving transition metals, and contributions of crustal-derived Cl, Br, and I to the pool of reactive halogens.
- Collaborate with other participating scientists in assessing details of halogen activation chemistry and related influences on the cycling, lifetimes, and environmental implications of tropospheric O3, hydrocarbons, and S(IV)
We deployed two types of sampling systems. One type was the same mist chamber systems that we used on the Polarstern cruise in 2003. The other type was filter packs containing a cellulose filter to collect aerosols followed by tandem rayon membranes saturated with lithium hydroxide to trap inorganic bromine and iodine gases. The filter pack samples are now (July 2007) being analyzed by neutron activation. Preliminary results will be presented at a RHaMBLe data workshop in the UK in early 2008.
The UNH/MWO and UVA RHaMBLe field team. From left to right: Bill Keene (UVA), Mike Long (UVA), Bob Deegan (MWO), Elena Crete (UNH/MWO), John Maben (UVA), Alex Pszenny (UNH/MWO) and Rolf Sander from the Max-Planck-Institute for Chemistry in Mainz, Germany, who volunteered his time to the project.