Atmospheric N concentrations in Central Asia

Biogeosciences Discussions This discussion paper is/has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG if available. Abstract Atmospheric concentrations of reactive nitrogen species (Nr) from 2009 to 2011 are reported for ten sites in Xinjiang, an arid region in Northwest China. Concentrations of NH 3 , NO 2 , particulate ammonium and nitrate (pNH + 4 and pNO − 3) showed large spatial and seasonal variation and averaged 7.71, 9.68, 1.81 and 1.13 µg N m −3 , and PM 10 5 concentrations averaged 249.2 µg m −3 across all sites. Lower NH 3 concentrations and higher NO 2 , pNH + 4 and pNO − 3 concentrations were found in winter, reflecting serious air pollution due to domestic heating in winter and other anthropogenic sources such as increased emissions from motor traffic and industry. The order of increasing total concentrations of Nr species was alpine grassland < desert, desert-oasis ecotone < desert 10 in an oasis < farmland < suburban and urban ecosystems. Lower ratios of secondary particles (NH + 4 and NO − 3) were found in the desert and desert-oasis ecotone, while urban and suburban areas had higher ratios, which implies that anthropogenic activities have greatly influenced local air quality and must be controlled.