Gaseous reactive nitrogen compounds play an important role in the atmospheric chemistry defining climate and air quality. Our current understanding of the production of trace N gases at the soil surface is based on microbial processing of soil N. However, measurements in the Mojave Desert indicate that emissions of trace N gases show diurnal fluctuations that are unlikely to be completely biological in origin. Emissions patterns of trace N gases appear to match daily changes in the intensity of solar radiation and not temperature, suggesting abiotic processes driven by photolytic reactions contribute to N gas loss. We used natural variation in solar radiation and seasonal changes in biological activity and temperature to explore the role of light in describing patterns of trace N gas efflux. Diurnal measurements of trace N gas efflux were made in three distinct seasons. Winter trace N gas efflux was minimal, average NO, NOy and NH3 fluxes were <0.01 mmol m-2 s-1 and only NOy emissions showed diurnal flux patterns. In contrast, trace N gas fluxes during the summer months, when biological activity is also minimal, were 2 – 4 times higher than those in the winter and showed strong diurnal patterns. Fluxes exceeded 0.1 mmol m-2 s-1 at midday and precipitately crashed at sundown, despite continued high soil temperatures. Some diurnal patterning of trace N gas fluxes is also evident in the spring, however, consistently high NO fluxes, 0.1 mmol m-2 s-1, suggest that biotic production dominates during the growing season.
