Observations of isoprene, monoterpenes and glyoxal in the remote tropical Atlantic atmosphere

Abstract:

Oceanic emissions of reactive organic carbon alter marine background chemistry and have the potential to contribute to marine aerosol distributions, with implications for climate. Highly reactive compounds such as isoprene, monoterpenes and glyoxal have been observed in the marine atmosphere and/or ocean, yet their atmospheric impact is extremely uncertain. This is largely due to the limited observational dataset, and thus a high level of uncertainty in global sources and spatial distributions of these compounds. The Oceanic Reactive Carbon: chemistry-climate impacts (ORC3) project aims to improve our knowledge of the sources and impacts of these reactive species in the remote marine atmosphere, through two 1-month field campaigns in the tropical Atlantic Ocean, and dedicated modelling activities.

We will present preliminary results from the two campaigns which took place during summer 2014 at the NCAS Cape Verde atmospheric observatory (16° 51' 49 N, 24° 52' 02 W), off the West African Atlantic coast. New datasets on the abundances of monoterpenes, isoprene and glyoxal have been obtained, spanning several weeks. Speciated monoterpene and isoprene observations have been obtained using a bespoke thermal desorption system hyphenated with portable GC-MS instrumentation. Glyoxal has been measured using a sensitive laser-induced phosphorescence (LIP) in-situ technique, which complements the limited database of remote-sensed glyoxal concentration measurements made in the remote marine atmosphere to date. We will describe the preliminary datasets obtained, and discuss implications for the atmospheric oxidising capacity and aerosol budget in the remote marine regions.