| Popis: |
As part of the Nitrogen Species Methods Comparison Study at Claremont, CA, two triple filter packs and two tuneable diode laser systems were used to measure atmospheric HNO 3 ; the filters also measured total suspended particulate compounds and gaseous NH 3 . The filter packs sampled for 1- and 2-h and 4- and 6-h periods and the lasers operated on 5-min averaging periods. Filter samples from the 4- and 6-h periods yielded, on average, about 16% higher HNO 3 than those from the 1- and 2-h periods. Linear least squares regressions of the 1- and 2-h filter HNO 3 concentrations with the average of the two lasers were highly significant, yielding slopes of 1.22 for daytime and 0.76 for night-time periods. Similar regressions of the 4- and 6-h filter HNO 3 with the laser, annular denuder and denuder difference methods yielded slopes in the range 1.14–1.81. For measurement of atmospheric NH 3 , the 4- and 6-h filter results were about 16 % lower than those from the Fourier transform infrared method. |
