Near-ground ozone source attributions and outflow in central eastern China during MTX2006

[摘要] A 3-D regional chemical transport model, the Nested Air Quality PredictionModel System (NAQPMS), with an on-line tracer tagging module was used tostudy the source of the near-ground (<1.5 km above ground level) ozone atMt. Tai (36.25° N, 117.10° E, 1534 m a.s.l.) in Central EasternChina (CEC) during the Mount Tai eXperiment 2006 (MTX2006). The modelreproduced the temporal and spatial variations of near-ground ozone andother pollutants, and it captured highly polluted and clean cases well. Thesimulated near-ground ozone level over CEC was 60–85 ppbv (parts perbillion by volume), which was higher than values in Japan and over the NorthPacific (20–50 ppbv). The simulated tagged tracer data indicated that theregional-scale transport of chemically produced ozone over other areas inCEC contributed to the greatest fraction (49%) of the near-ground meanozone at Mt. Tai in June; in situ photochemistry contributed only 12%.Due to high anthropogenic and biomass burning emissions that occurred in thesouthern part of the CEC, the contribution to ground ozone levels from thisarea played the most important role (32.4 ppbv, 37.9% of total ozone) inthe monthly mean ozone concentration at Mt. Tai; values reached 59 ppbv(62%) on 6–7 June 2006. The monthly mean horizontal distribution ofchemically produced ozone from various ozone production regions indicatedthat photochemical reactions controlled the spatial distribution of O₃over CEC. The regional-scale transport of pollutants also played animportant role in the spatial and temporal distribution of ozone over CEC.Chemically produced ozone from the southern part of the study region can betransported northeastwardly to the northern rim of CEC; the meancontribution was 5–10 ppbv, and it reached 25 ppbv during high ozoneevents. Studies of the outflow of CEC ozone and its precursors, as well astheir influences and contributions to the ozone level over adjacentregions/countries, revealed that the contribution of CEC ozone to mean ozonemixing ratios over the Korean Peninsula and Japan was 5–15 ppbv, of whichabout half was due to the direct transport of ozone from CEC and half wasproduced locally by ozone precursors transported from CEC.

[学科分类] 大气科学