In Situ Measurements of Hydrogen Peroxide, Nitric Acid and Reactive Nitrogen to Assess the Ozone Sensitivity in Pingtung County, Taiwan

This study was aimed to investigate the concentration of hydrogen peroxide (H 2 O 2 ), nitric acid (HNO 3 ) and reactive nitrogen (NO y ) at three sites in Southern Taiwan during 2003–2004. The mean H 2 O 2 concentrations were 1.0–2.7 ppbv, 1.6–2.8 ppbv and 1.0–2.6 ppbv at Pingtung, Chao-Chou and Kenting, respectively. Meanwhile, the mean HNO 3 concentrations were 2.7–5.5 ppbv at Pingtung, 1.9–4.6 ppbv at Chao-Chou and 1.2–3.0 ppbv at Kenting. The NO y mean concentrations were 61.0–85.0 ppbv, 16.0–75.0 ppbv and 4.2–12.0 ppbv at Pingtung, Chao-Chou and Kenting, respectively. The hourly data of H 2 O 2 , HNO 3 , NO y and O 3 were then used to determine the ratio of H 2 O 2 to HNO 3 , O 3 to HNO 3 , O 3 to NO y and the extent of reaction ( E ) in Smog Production Model (SPM) to evaluate the NO x and VOC sensitivity of ozone formation in Southern Taiwan. The results show that Pingtung city was primarily VOC-sensitive regime in four seasons. At Chao-Chou, the percentages of VOC-sensitive regime exceed those in NO x -sensitive regime in H 2 O 2 /HNO 3 and O 3 /NO y in four seasons; but O 3 /HNO 3 indicates NO x -sensitive regime in autumn, winter and spring. Kenting was mainly dominated by NO x -sensitive by use of three indicators in four seasons. The SPM results are consistent with those determined by the photochemical indicator ratios although the percentages of dominance may vary among these analyses.