九州大学筑紫キャンパスにおけるアンモニア態窒素と無機硝酸態窒素のガス・粒径別エアロゾル濃度の季節変化

抄録

Gaseous compounds (NH₃ and HNO₃) and size-segregated aerosol particles (NH₄^＋ and NO₃^-) were measured at Chikushi Campus, Kyusyu University from July 31, 2014 to October 19, 2015. NH₃ and fine NH₄^＋ concentrations were semi-continuously (34 min interval) measured by using a micro flow analytical system. HNO₃ and size-segregated aerosol particles were collected for 1 to 3 days intervals by using an annular denuder with a multiple filter set (Nuclepore, PTFE, and Nylon). Intensive sampling (ca. 8 hours interval) was conducted twice from September 24 to October 9, 2014 and from January 7 to 17, 2015. NH₃ and HNO₃ concentrations were high in warm season, whereas NH₄^＋ and NO₃^- concentrations in fine particles were high in cold season. NH₃ concentrations were low after rain in the ensuing days and were higher after days without rain. HNO₃ concentration during fall experiment was periodically high in daytime under sunny and sea breeze wind conditions, suggesting contribution of local NO₂ oxidation to high HNO₃ during daytime. Seasonal variations of gas-particle phase relationships of NH₃ and HNO₃ were discussed in terms of temperature dependence of NH₄NO₃ equilibrium. Concentration products between NH₃ and HNO₃ were mostly below equilibrium of NH₄NO₃ estimated from air temperature during sample collection, suggesting that formation of NH₄NO₃ was limited during late winter to early spring.