南极威德尔海周边雪冰和大气气溶胶中的MSA,nssSO_4^(2-)浓度及其比率研究

STUDY OF THE MSA,nssSO 2- 4 CONCENTRATION AND MSA TO nssSO 2- 4 RATIO IN THE SNOW/ICE AND ATMOSPHERIC AEROSOLS OF THE REGION SURROUNDING WEDDELL SEA

分析了威德尔海周边雪冰和大气中ＭＳＡ和ｎｓｓＳＯ２－４浓度资料。结果表明，威德尔海是造成这一地区大气中高含量生物硫化物的“源”，其周边岛屿及冰架表层雪冰记载和反映了大气中生物硫化物的空间分布和季节变化特点。源区产出硫化物的强度存在显著差异：靠近南极半岛一侧高于靠近Ｆｉｌｃｈｎｅｒ－Ｒｏｎｎｅ冰架一侧。尽管诸多因素对输运和沉降过程发生影响，表层积雪ＭＳＡ和ｎｓＳＯ２－４浓度仍呈现出很有规律性的空间分布：随沉降地点离海距离和海拔高度的增加，浓度值递减；但在一定海拔之下，“高程效应”不显著。冰芯中ＭＳＡ浓度垂向分布显示出季节分配“滞后”现象，在表层表现为受天气条件制约的输运过程造成的相位差，在深层则归因于有待验证的“迁移”机制作用的结果。大气和雪冰样品对比研究结果表明，在类似威德尔海这样的高纬地区，大气中的ＳＯ２－４和ＭＳＡ“信号”在雪冰样品中会遭到不同程度的减弱。但就空间变化趋势和季节分布而言，表层雪冰仍是大气中组分（在本文是ＳＯ２－４和ＭＳＡ）的良好载体。十分接近的大气和雪冰ＭＳＡ对ｎｓｓＳＯ２－４（或ＳＯ２－４）比率证实，这两种大气组分在由大气洗净和沉降到冰雪过程中只发生微弱的分离作用。这也就是大气和雪冰中?

The MSA and nssSO 2- 4 concentration data from the ice cores and from atmospheric aerosols of the region surrounding Weddell Sea have been analyzed by present paper. The results suggest that the high concentration of biogenic sulphur in the snow and ice as well as in the atmosphric aerosols reflects the proximity of the Weddell Sea even though a distinct strength discrepancy exists in the productivity among areas. It seems higher in the middle of Antarctic Peninsula than near the Filchner Ronne ice shelf as evidenced by the snow/ice analysis. Despite factors impacting on the transport and deposition process of biogenic surlphur, the concentration of MSA and nssSO 2- 4 in snow and ice shows a regular spatial distribution: decreasing with the distance from the open sea and the altitude above sea level. Nevertheless, below a certain height, the “altitude effect” is no longer significant. The “displacement” of seasonality for MSA concentration observed in ice cores of the region has been discussed. The “out of phase” pattern in surface layer is attributed to the modification by prevailing meteorological condition to the transport and deposition process; while “relocation” in the deep layers may be caused by migration, a mechanism which is to be further investigated.The comparative study of the atmospheric and snow/ice samples indicates that at high latitude like Weddell Sea the atmospheric signal of SO 2- 4 and MSA could be somewhat muted in the snow. But the seasonal variation in the airborn sulfate and MSA are reasonably well reproduced in the surface snow, for timing and spacial distribution. The very close ratio of MSA to nssSO 2- 4 (or to SO 2- 4) of atmospheric aerosol and snow/ice sample is indicative of weak, if any, fraction between the two species during the scavenging and deposition process. This could serve as the inner reason to explain the relative stable MSA/nssSO 2- 4 ratio, both for atmosphere and snow, an important regional index for the study of marine biogenic sulfur.