Measurement System for Particulate Nitrate Based on the Scrubber Difference NO-O_(3) Chemiluminescence Method in Remote Areas

摘要

A particulate nitrate analyzer based on a scrubber difference/NO-O_(3) chemiluminescence method (SD-CL method) has been developed for measuring nitrate concentrations in remote areas. Particulate nitrate concentrations (NO_(3)~(-)(p)) were analyzed by the difference between the concentrations of NO_(y) - gaseous nitric acid (HNO_(3)) and NO_(y) - HNO_(3) - NO_(3)-(p). Annular denuders coated with NaCl and PTFE filter were used as the scrubbers for HNO_(3) and NO_(3)-(p), respectively. The transmission efficiency of coarse particles in the denuder was found to be 93.4 +- 5.8percent, so the loss of NO_(3)-(p) to the denuder was within the uncertainty of the particulate nitrate analyzer (+-20percent). The measurements of NO_(y), HNO_(3), and NO_(3)~(-)(p) were conducted from March 15 to April 31, 2008, at Cape Hedo, Okinawa, Japan. Over 99.5percent of the observed concentrations of NO_(3)~(-)(p) for 10 min integration times were higher than the detection limit of the SD-CL method (0.18 (mu)g m~(-3)). The least-squares fit of the R&P nitrate monitor against the SD-CL method yielded a slope of 0.67 +- 0.02 and a correlation coefficient of R velence 0.73. This result indicates that this method could also measure NO_(3)~(-)(p) when the diameter of aerosols was larger than 10 (mu)m. The SD-CL method was found to be useful as a measurement system for NO_(3)~(-)(p) in remote areas where coarse NO_(3)~(-)(p) dominates.