摘要
生物有机酸的研究有助于认识C、H、O等生源元素的生物地球化学循环 ,有助于认识大气酸雨的形成及其防治 .雪冰是记录大气中生物有机酸过去信息的良好载体 ,对其中生物有机酸记录的研究是认识过去大气中相应化合物的含量及其变化 ,认识有机酸的生物地球化学循环 ,进而恢复过去区域生态、环境乃至气候变化的有效途径 ,也是雪冰化学研究的前沿课题之一 .雪冰中常见的有机酸有甲酸、乙酸、丙酸、丙酮酸、草酸和羟基乙酸等 ,其中甲酸和乙酸是最主要的两种有机酸类 .过去十多年来 ,雪冰中生物有机酸的研究多集中在格陵兰地区 ,其次是南极 ,最近两年开始向中低纬度的山地冰川转移 .格陵兰冰芯中甲酸、乙酸的平均含量均不足 10ng·g-1,草酸含量则更低 .其有机酸主要来自北半球的森林大火和植物生长过程中的释放 ;南极洲雪冰中的甲酸平均含量不足 2ng·g-1,乙酸含量在 0 .15ng·g-1以下 ,它们主要源于不饱和有机物的大气氧化 ;格陵兰冰芯中MSA平均在 5ng·g-1以下 ,而南极洲的MSA平均不低于 7ng·g-1.它们的来源都与海洋浮游生物释放的不饱和有机物有关 .气候的变化影响两极地区生物有机酸的来源 ,进而影响冰芯中有机酸的记录 .我国天山乌鲁木齐河源 1号冰川为中纬度的山地冰川 ,其冰芯中的甲酸、乙酸分别是格陵?
The study of organic acids recorded in snow and ice provides a unique way to obtain information on a variety of the species in response topast climate change,past environment and past ecosystem, and represents one of the main fields in glaciochemistry. It also provides insight into biogeochemical cycles of carbon, hydrogen and oxygen and other major biological elements. In August 1987, a special session on organic acids and related compounds in the atmosphere was held at the Sixth International Symposium of the Commission on Atmospheric Chemistry and Global Pollution in Peterborough, Canada, which symbolized that studies of organic acids had drawn attention of researchers around the world. The organic acids detected in snow and ice are formic, acetic, propionic, pyruvic, oxalic and glycolic. The former two represent the most abundant ones. In some places, their concentrations are even higher than inorganic acids such as sulfate, nitrate and chloride. For the past decade, the study of the organic acids mainly focused on Greenland and Antarctica. Recent two years, however, the study turns to alpine glaciers in the middle and low latitude areas because organic acids recorded in alpine glaciers are much closer to the sources than those in polar areas. Studies show that formic and acetic in Greenland ice cores reached up to 10ng·g -1 in their average concentrations with the former higher than the latter, while the oxalic and glycolic are below 1 ng·g -1 . They mainly came from biomass burning, which accounts for about 20 %, and vegetation emissions in the north hemisphere that contribute to the background of the organic acids. In even lower concentrations, the formic acids recorded in Antarctic ice cores are below 2 ng·g -1 , whereas the acetic below 0.15ng·g -1 . They are considered as from the atmospheric oxidation of numerous hydrocarbons such as methane and alkenes. MSA in Greenland ice cores is below 5ng·g -1 on an average, whereas that in Antarctica up 7ng·g -1 . They all came from the oceanic emission of DMS. In sharp contrast, formic and acetic acids in the Glacier No.1 at the headwaters of the rümqi River, a middle latitude alpine glacier in the Tianshan Mountains, West China, are several ten-fold higher than those in Greenland, and a few thousands times more than those in Antarctica. Moreover, resolution of organic acid records in middle latitude alpine glaciers is also higher than those in polar areas. This demonstrates that the organic records in alpine glaciers are more conducive to understanding the biogeochemical cycles of the organic acids. Climate changes affect the terrestrial vegetation, the source for the carboxylic acids, and the oceanic production of DMS, the precursor of MSA, thus the secular trends of the organic acid records in ice cores. It is interested to note that MSA connects the climate change in different ways for the two hemispheres. Greenland ice cores demonstrate the MSA correlates positively with climate change, while it does somewhat negatively in Antarctica. ENSO affects the production of DMS in the southern hemisphere and it probably causes the disparity. The change of the formic/acetic ratio in the Greenland ice core from 1945 suggests the anthropogenic impact from the northern hemisphere, which caused an increase of acetic acid while a decrease of formic.
出处
《冰川冻土》
CSCD
北大核心
2001年第4期442-449,共8页
Journal of Glaciology and Geocryology
基金
国家自然科学基金项目 ( 4 0 0 730 35
498710 2 2 )
中国科学院"九五"重大项目 (KZ95 1 A1 40 2 0 3)
中国科学院天山冰川观测试验站站长基金
中国博士后基金资助
