AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Observations of Sharp Oxalate Reductions in Stratocumulus Cloud Water at Variable Altitudes
Armin Sorooshian, ZHEN WANG, Matthew Coggon, Haflidi Jonsson, Barbara Ervens, University of Arizona
Abstract Number: 596 Working Group: Aerosols, Clouds, and Climate
Abstract This work examines organic acid and metal concentrations in northeastern Pacific Ocean stratocumulus cloud water samples collected by the CIRPAS Twin Otter between July-August 2011. Correlations between a suite of various monocarboxylic and dicarboxylic acid concentrations are consistent with documented aqueous-phase mechanistic relationships leading up to oxalic acid production. Monocarboxylic and dicarboxylic acids exhibited contrasting spatial profiles reflecting their different sources; the former were higher in concentration near the continent due to fresh organic emissions. Concentrations of sea salt crustal tracer species, oxalate, and malonate were positively correlated with low-level wind speeds suggesting that an important route for oxalate and malonate entry in cloud water is via some combination of association with coarse particles and gaseous precursors emitted from the ocean surface. Three case flights show that oxalate (and no other organic acid) concentrations drop by nearly an order of magnitude relative to samples in the same vicinity. A consistent feature in these cases was an inverse relationship between oxalate and several metals (Fe, Mn, K, Na, Mg, Ca), especially Fe. By means of box model studies we show that the loss of oxalate due to the photolysis of iron oxalato complexes is likely a significant oxalate sink in the study region due to the ubiquity of oxalate precursors, clouds, and metal emissions from ships, the ocean, and continental sources.