As a result of controls on NOx emissions from cars, trucks, and electricity production, NOx levels (sum on NO and NO2) have decreased rapidly across North America over the past decades. The reductions in NO alter the photochemical pathways in the oxidation of numerous chemicals emitted from the biosphere and from anthropogenic activities. The gas phase chemistry in the low NO regime has received significantly less attention from atmospheric chemists. Here, I describe new analytical methods to probe the low NOx chemistry in the field and in the laboratory. New chemical pathways are identified illustrating that great care must be taken in extrapolating of existing photochemical models to the low NOx atmosphere.















Paul Wennberg (California Institute of Technology)