Sampling and analysis of the sea surface microlayer for dissolved and particulate trace elements

The air-sea interface, or sea surface microlayer (1-1000 μm), is a unique environment with different physical, chemical, and biological properties compared to the underlying water column. It is an important, yet often ignored component in the biogeochemical cycling of trace elements in the marine environment due to the lack of trace element clean sampling and analytical methods. A novel technique, a hollow cylinder of ultra-pure SiO2 (quartz glass) with a plastic handle, was developed to sample the microlayer for trace elements. This research also developed and optimized clean trace element techniques to accurately measure nine trace metals (Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) in the dissolved and particulate fractions of the microlayer and underlying water column. Preliminary data from a study in the Western Mediterranean Sea involving a mesocosm (in situ all plastic bag) showed consistent measurements in the trace element concentrations over the course of several days. Microlayer samples that were collected outside the mesocosm showed increased dissolved and particulate trace element concentrations resulting from a wet deposition event.