Dataset Information

Comparison of the RADM2 and RACM chemical mechanisms in O₃ simulations: effect of the photolysis rate constant.

ABSTRACT: Since the photolysis rate plays an important role in any photoreaction leading to compound sink and radical formation/destruction and eventually O₃ formation, its impact on the simulated O₃ concentration was evaluated in the present study. Both RADM2 and RACM were adopted with and without updated photolysis rate constants. The newly developed photolysis rates were determined based on two major absorption cross-section and quantum yield data sources. CMAQ in conjunction with meteorological MM5 and emission data retrieved from Taiwan and East Asia were employed to provide spatial and temporal O₃ predictions over a one-week period in a three-level nested domain [from 81 km?×?81 km in Domain 1 (East Asia) to 9 km?×?9 km in Domain 3 (Taiwan)]. Four cases were analyzed, namely, RADM2, with the original photolysis rates applied in Case 1 as a reference case, RADM2, with the updated photolysis rates applied in Case 2, and RACM, with and without the updated photolysis rates applied in Cases 3 and 4, respectively. A comparison of the simulation and observed results indicates that both the application of updated photolysis rate constants and RACM instead of RADM2 enhanced all three error analysis indicators (unpaired peak prediction accuracy, mean normalized bias error and mean absolute normalized gross error). Specifically, RADM2 with the updated photolysis rates resulted in an increase of 12 ppb (10%) in the daily maximum O₃ concentration in southwestern Taiwan, while RACM without the updated photolysis rates resulted in an increase of 20 ppb (17%) in the daily maximum O₃ concentration in the same area. When RACM with the updated photolysis rate constants was applied in the air quality model, the difference in the daily maximum O₃ concentration reached up to 30 ppb (25%). The implication of Case 4 (RACM with the updated photolysis rates) for the formation and degradation of ?-pinene and d-limonene was examined.

SUBMITTER: Chen CH

PROVIDER: S-EPMC7930097 | biostudies-literature | 2021 Mar

REPOSITORIES: biostudies-literature

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Publications

Comparison of the RADM2 and RACM chemical mechanisms in O3 simulations: effect of the photolysis rate constant.

Chen Chien-Hung CH Chen Tu-Fu TF Huang Shang-Ping SP Chang Ken-Hui KH

Scientific reports 20210303 1

Since the photolysis rate plays an important role in any photoreaction leading to compound sink and radical formation/destruction and eventually O3 formation, its impact on the simulated O3 concentration was evaluated in the present study. Both RADM2 and RACM were adopted with and without updated photolysis rate constants. The newly developed photolysis rates were determined based on two major absorption cross-section and quantum yield data sources. CMAQ in conjunction with ...[more]

PMID: 33658633

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Project description:The dissociation between constant work rate of O2 uptake (V?o2) and ramp V?o2 at a given work rate might be mitigated during slowly increasing ramp protocols. This study characterized the V?o2 dynamics in response to five different ramp protocols and constant-work-rate trials at the maximal metabolic steady state (MMSS) to characterize 1) the V?o2 gain (G) in the moderate, heavy, and severe domains, 2) the mean response time of V?o2 (MRT), and 3) the work rates at lactate threshold (LT) and respiratory compensation point (RCP). Eleven young individuals performed five ramp tests (5, 10, 15, 25, and 30 W/min), four to five time-to-exhaustions for critical power estimation, and two to three constant-work-rate trials for confirmation of the work rate at MMSS. G was greatest during the slowest ramp and progressively decreased with increasing ramp slopes (from ~12 to ~8 ml·min-1·W-1, P < 0.05). The MRT was smallest during the slowest ramp slopes and progressively increased with faster ramp slopes (1?±?1, 2?±?1, 5?±?3, and 10?±?4, 15?±?6 W, P < 0.05). After "left shifting" the ramp V?o2 by the MRT, the work rate at LT was constant regardless of the ramp slope (~150 W, P > 0.05). The work rate at MMSS was 215?±?55 W and was similar and highly correlated with the work rate at RCP during the 5 W/min ramp (P > 0.05, r?=?0.99; Lin's concordance coefficient?=?0.99; bias?=?-3 W; root mean square error?=?6 W). Findings showed that the dynamics of V?o2 (i.e., G) during ramp exercise explain the apparent dichotomy existing with constant-work-rate exercise. When these dynamics are appropriately "resolved", LT is constant regardless of the ramp slope of choice, and RCP and MMSS display minimal variations between each other.NEW & NOTEWORTHY This study demonstrates that the dynamics of V?o2 during ramp-incremental exercise are dependent on the characteristics of the increments in work rate, such that during slow-incrementing ramp protocols the magnitude of the dissociation between ramp V?o2 and constant V?o2 at a given work rate is reduced. Accurately accounting for these dynamics ensures correct characterizations of the V?o2 kinetics at ramp onset and allows appropriate comparisons between ramp and constant-work-rate exercise-derived indexes of exercise intensity.

Dataset Information

Comparison of the RADM2 and RACM chemical mechanisms in O₃ simulations: effect of the photolysis rate constant.

Publications

Comparison of the RADM2 and RACM chemical mechanisms in O<sub>3</sub> simulations: effect of the photolysis rate constant.

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