Nitrogen isotopic composition and source of nitrate in precipitation at Guiyang
贵阳地区大气降水中δ15N-NO3-组成及来源分析

This study analyzed the concentrations of NO-3 and values of δ15N-NO-3 in precipitation taken at Guiyang throughout one year from October 1, 2008 to September 30, 2009. The results indicated that the volume-weighted average concentration of NO-3 was 0.45 mg·L-1, and the value of δ15N-NO-3 ranges from -8.0‰ to 28.7‰ with the annual average of 2.3‰ This implied that the source of NO-3 was mainly from coal combustion. Significantly higher NO-3 concentration in winter than summer suggested that NO-3 concentration was mainly affected by precipitation. Seasonal variation of nitrogen isotopic composition was a bit different, with positive in autumn and winter and negative in spring and summer. This suggested that δ15N-NO-3 was mainly affected by biologically-released N, atmospheric nitrogen fixation and NOx behavior in the atmosphere.