Near-ground ozone source attributions and outflow in central eastern China during MTX2006
A 3-D regional chemical transport model, the Nested Air Quality\nPrediction Model System (NAQPMS), with an on-line tracer tagging module\nwas used to study the source of the near-ground (<1.5 km above ground\nlevel) ozone at Mt. Tai (36.25 degrees N, 117.10 degrees E, 1534 m\na.s.l.) in Central Eastern China (CEC) during the Mount Tai eXperiment\n2006 (MTX2006). The model reproduced the temporal and spatial variations\nof near-ground ozone and other pollutants, and it captured highly\npolluted and clean cases well. The simulated near-ground ozone level\nover CEC was 60-85 ppbv ( parts per billion by volume), which was higher\nthan values in Japan and over the North Pacific (20-50 ppbv). The\nsimulated tagged tracer data indicated that the regional-scale transport\nof chemically produced ozone over other areas in CEC contributed to the\ngreatest fraction (49%) of the near-ground mean ozone at Mt. Tai in\nJune; in situ photochemistry contributed only 12%. Due to high\nanthropogenic and biomass burning emissions that occurred in the\nsouthern part of the CEC, the contribution to ground ozone levels from\nthis area played the most important role (32.4 ppbv, 37.9% of total\nozone) in the monthly mean ozone concentration at Mt. Tai; values\nreached 59 ppbv (62%) on 6-7 June 2006. The monthly mean horizontal\ndistribution of chemically produced ozone from various ozone production\nregions indicated that photochemical reactions controlled the spatial\ndistribution of O-3 over CEC. The regional-scale transport of pollutants\nalso played an important role in the spatial and temporal distribution\nof ozone over CEC. Chemically produced ozone from the southern part of\nthe study region can be transported northeastwardly to the northern rim\nof CEC; the mean contribution was 5-10 ppbv, and it reached 25 ppbv\nduring high ozone events. Studies of the outflow of CEC ozone and its\nprecursors, as well as their influences and contributions to the ozone\nlevel over adjacent regions/countries, revealed that the contribution of\nCEC ozone to mean ozone mixing ratios over the Korean Peninsula and\nJapan was 5-15 ppbv, of which about half was due to the direct transport\nof ozone from CEC and half was produced locally by ozone precursors\ntransported from CEC.