Observation of nitrate radical in the nocturnal boundary layer during a summer field campaign in pearl river delta China

Abstract

From July 4 to 11, 2006 at Back Garden site (23°28'86''N; 113°02'91"E), nighttime nitrate radical (NO 3) was measured with a long path differential optical absorption spectroscopy (DOAS) during an intensive field campaign in the Pearl River Delta of China. The NO 3 concentration in polluted air masses varied from 3.6 to 82.5 ppt with an average level of 21.8 ± 1.8 ppt. NO 3 at these levels can play a significant role in oxidation of volatile organic compounds (VOCs). The calculated production rate of nitrate radical ranged from 8 × 10 5 to 2.98 × 10 7 cm -3 S -1, while its lifetimes spanned from between just several seconds to 650 seconds, with an average of 89 seconds. N 2O 5 levels were calculated with the average of 620 ± 93 ppt during this campaign. The possible scavenging processes for the nitrate radical were obtained by using a statistical analysis of the correlation between NO 3 and NO levels, NO 3 concentration and its production rate, and the NO 3 lifetime and NO 2 levels, respectively. Results showed that the direct losses were of importance at Back Garden in summer Pearl River Delta,.