2013 Volume 62 Issue 9 Pages 775-783
Nitrophenols (NPs), having effects on human health, are produced in the atmosphere via several pathways. However, the behavior details of atmospheric NPs are not well understood. In this work, daily variations of NPs were investigated by repeating 2-h collection using silica-gel columns followed by HPLC/MS analysis. The collection method was optimized and large-volume injection and in-line preconcentration was automated for the HPLC analysis. The quantification limits by atmospheric-pressure chemical ionization mass analysis for each atmospheric NP ranged between 0.08 and 0.67 ng m−3 with a time resolution of 2 h. Clear daily variations were obtained by this method. Whereas NP concentrations were high around noon in the summer, they were maxima before midnight in the winter. This was likely due to a difference in the main mechanism for NP formations: mainly the OH radical and the NO3 radical initiated the formation reaction in the summer and winter, respectively. In the winter, the total NP concentration was higher than that in the summer especially 2-nitrophenol which accounted for half of all NPs measured. On the contrary, formation of dinitrophenol from mononitrophenol seemed to proceed abundantly in the summer. Also, a seasonal variation was detected from rain water analysis and filter sampling. The concentrations and partition of NPs were different, alowing differences in the polarity and reactivity. It was considered that the NP concentrations changed dynamically in the atmosphere via secondary production, and reactions to disappear.
