资源环境科技发展态势分析平台

Triple oxygen isotopic compositions (Delta O-17 = delta O-17-0.52 x delta O-18) of atmospheric sulfate (SO42-) and nitrate (NO3-) in the atmosphere reflect the relative contribution of oxidation pathways involved in their formation processes, which potentially provides information to reveal missing reactions in atmospheric chemistry models. However, there remain many theoretical assumptions for the controlling factors of Delta O-17(SO42-) and Delta O-17(NO3-) values in those model estimations. To test one of those assumption that Delta O-17 values of ozone (O-3) have a flat value and do not influence the seasonality of Delta O-17(SO42-) and Delta O-17(NO3-) values, we performed the first simultaneous measurement of Delta O-17 values of atmospheric sulfate, nitrate, and ozone collected at Dumont d'Urville (DDU) Station (66 degrees 40 ' S, 140 degrees 01 ' E) throughout 2011. Delta O-17 values of sulfate and nitrate exhibited seasonal variation characterized by minima in the austral summer and maxima in winter, within the ranges of 0.9-3.4 and 23.0-41.9 %, respectively. In contrast, Delta O-17 values of ozone showed no significant seasonal variation, with values of 26 +/- 1% throughout the year. These contrasting seasonal trends suggest that seasonality in Delta O-17(SO42-) and Delta O-17(NO3-) values is not the result of changes in Delta O-17(O-3), but of the changes in oxidation chemistry. The trends with summer minima and are caused by sunlight-driven changes in the relative contribution of O3 oxidation to the oxidation by HOx, ROx, and H2O2. In addition to that general trend, by comparing Delta O-17(SO42-) and Delta O-17(NO3-) values to ozone mixing ratios, we found that Delta O-17(SO42-) values observed in spring (September to November) were lower than in fall (March to May), while there was no significant spring and fall difference in Delta O-17(NO3-) values. The relatively lower sensitivity of Delta O-17(SO42-) values to the ozone mixing ratio in spring compared to fall is possibly explained by (i) the increased contribution of SO2 oxidations by OH and H2O2 caused by NOx emission from snowpack and/ or (ii) SO2 oxidation by hypohalous acids (HOX = HOCl + HOBr) in the aqueous phase.