Classical Odd-hydrogen Reservoir Species in the Marine Boundary Layer During the California Nexus Program

Hydrogen peroxide, methylhydroperoxide and formaldehyde were measured in the marine boundary layer from on board the R/V Atlantis during the CalNex program along with a suite of other photochemically active gas and aerosol species. The CalNex R/V Atlantis sub-program was focused on improving our understanding of aerosol and gas photochemistry under a variety of mixed maritime and urban air mass conditions. The cruise occurred between May 14 and June 8, 2010, and the ship's track was along the California coast from San Diego, to the Los Angeles bight, to San Francisco and inland up the Sacramento River to the 'turn-around basin'. Hydrogen peroxide mixing ratios ranged from below the detection limit (0.02 ppb) to 2.1 ppb. Methylhydroperoxide mixing ratios ranged from below the detection limit (0.04 ppb) to 1.2 ppb. Measurements of peracetic were attempted, however, mixing ratios above the detection limit (0.2 ppb), were not encountered. Formaldehyde was measured using a wet chemical derivatization fluorescence method and by a quantum cascade laser spectral absorption method. The measurements ranged from below the detection limit, nominally 0.020 ppb (QCL) and 50 (WetChem), to greater than 15 ppb; with values typically between 0.2 and 2.0 ppb. A formaldehyde measurement comparison will be presented; the two systems agreed well. Hydrogen peroxide, methylhydroperoxide and formaldehyde will be presented and interpreted in terms of photochemistry, air quality, and meteorological conditions.