Performance Evaluation of an In Situ Nitrous Acid Measurement System and Continuous Measurement of Nitrous Acid in an Indoor Environment

摘要

Nitrous acid (HONO) may cause adverse effects to mucous membranes and lung function when people are exposed to higher HONO concentrations than those present in typical indoor residential environments. Therefore, deter-mination of HONO concentration in indoor environ-ments is required to investigate occurrences of high HONO levels. In this work, a high-time-resolution mea-surement system was utilized to better understand the levels and dynamic behavior of HONO in an indoor en-vironment. The performance of the in situ HONO ana-lyzer applied to this work was evaluated using a 12-hr integrated annular denuder technique under ambient conditions. Both methods for the measurements of HONO were in good agreement, with a regression slope of 0.84, an intercept of 0.09, and correlation coefficient (r~2) of 0.67. Indoor HONO and nitrogen oxide concentrations were also observed for approximately 5 days in winter in the living room of an apartment that had a gas range for cooking in the kitchen. Investigation of the relationships among nitric oxide (NO), nitrite (NO_2), and HONO con-centrations suggests that HONO production during com-bustion could be the result of direct emission, whereas the heterogeneous NO_2 chemistry during the background pe-riod and after combustion was the possible pathway of HONO production. Controlled combustion experiments, performed at a burning rate of 50% valve setting, show peak HONO concentrations during the unvented com-bustion to be approximately 8-10 times higher than background levels depending on the time of day. At a burning rate setting of 50%, the peak concentration of HONO during unvented combustion was found to be 33-37% higher than those from "weak" (airflow = 340 m~3/hr) and "strong" (airflow = 540 m~3/hr) vented com-bustions. The decay rate of the HONO concentrations for the unvented combustion conditions was approximately 2-fold higher in the daytime than in the nighttime and significantly less than those of NO and NO_2.