The response of methane and nitrous oxide fluxes to forest change in Europe

Atmospheric concentrations of reactive nitrogen (Nr) species from 2009 to 2011 are reported for ten sites in Xinjiang, China, an arid region of central Asia. Concentrations of NH3, NO2, particulate ammonium and nitrate (pNH4+ and pNO3 ) showed large spatial and seasonal variation and averaged 7.71, 9.68, 1.81 and 1.13 μg N m 3, and PM10 concentrations averaged 249.2 μg m 3 across all sites. Lower NH3 concentrations and higher NO2, pNH4+ and pNO3 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 increasing order of total concentrations of Nr species was alpine grassland; desert, desert-oasis ecotone; desert in an oasis; farmland; suburban and urban ecosystems. Lower ratios of secondary particles (NH4+ and NO3 ) were found in the desert and desert-oasis ecotone, while urban and suburban areas had higher ratios, which implied that anthropogenic activities have greatly influenced local air quality and must be controlled.