Collaborative Research: Multiple Isotope Analyses of Soil Sulfate and Nitrate in the Antarctic Dry Valleys

合作研究：南极干谷土壤硫酸盐和硝酸盐的多种同位素分析

• 批准号: 0125842
• 负责人: Huiming Bao
• 金额: $ 21.08万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-01 至 2006-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0125842&HistoricalAwards=false
• 关键词: Collaborative; Research; Multiple; Isotope; Analyses

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, provides funds for a study sulfate and nitrate in soils of the McMurdo Dry Valleys region of Antarctica. This goal is to quantify atmospheric deposition of sulfate and nitrate and to generate the first quantitative model for the origin, distribution, and post-depositional alteration of atmospheric sulfate and nitrate in Dry Valley soils. In addition to testing the hypothesis that landforms in the Dry Valleys have been stable for millions of years, results from this work will provide a valuable reference for quantitative soil development in hyper-arid deserts elsewhere on Earth and on Mars. The approach involves isotopic analyses of sulfur, oxygen, and nitrogen in the water-soluble oxy-anions, sulfate and nitrate, in soils of differing ages and parent materials. The breakthrough that makes this proposal possible is the recent discovery of mass-independent oxygen-isotopic composition for sulfate and nitrate in Dry Valley soils that shows that atmospheric deposition has contributed a significant amount of sulfate and nitrate to the cold-desert soils over time.Recent work by the PI's identified spatial patterns in the oxygen-isotopic composition of sulfate in Dry Valleys soils and requires the existence of two sulfate end members, sea-salt sulfate and biogenic sulfate. Here, the biogenic sulfate refers to those sulfates formed by the oxidation of reduced biogenic sulfur gases (e.g., dimethylsulfide) in the atmosphere. Biogenic sulfate, due to its long residence time can travel greater distances relative to sea-salt sulfate. The isotopic analyses of oxygen and sulfur that will be done within this project will differentiate between biogenic sulfate and sea-salt sulfate in Dry Valley soils. In addition, preliminary data on the oxygen-isotopic composition of nitrate from these soils reveal exceptionally large nitrate oxygen-17 anomalies and a spatial pattern that reflects a single nitrate source rather than two sources as for sulfate. To quantify long-term atmospheric input of sulfate and nitrate and their subsequent mobility in soils of this unique environment, this project will (1) sample vertical soil profiles at centimeter-to-sub-centimeter-scale resolution, (2) systematically analyze oxygen and sulfur isotopes in sulfate and oxygen and nitrogen isotopes in nitrate, (3) examine soils of a wide range of radiometric ages and parent materials, including ancient volcanic ashes, colluvium, lodgment tills, and ice-sublimation tills, and (4) construct a simple one-dimensional transport model for sulfate and nitrate in vertical soil profiles.This project represents collaboration between a low temperature isotope geochemist and a geomorphologist who has extensive experience in the Dry Valleys region. When combined with existing radiometric isotope chronology of Dry Valley soils developed over the last 15 years, the proposed stable isotopic analyses will, for the first time, quantify the rate and style of soil development and patterned ground evolution in the Dry Valleys region. These quantitative data are of paramount importance for achieving a thorough understanding of the Dry Valleys ecosystem and for establishing baseline data for comparison with anticipated analyses on Martian regolith following a sample return mission to Mars.

该奖项由极地计划办公室的南极地质与地球物理学计划提供，为研究硫酸盐和硝酸盐的资金提供了南极洲麦克默尔多干谷地区土壤的资金。该目标是量化硫酸盐和硝酸盐的大气沉积，并为干谷土壤中大气硫酸盐和硝酸盐的起源，分布和沉积后改变生成第一个定量模型。除了测试以下假设：干山谷中的地形已经稳定了数百万年之际，这项工作的结果还将为地球其他地方和火星上其他地方的沙漠中的定量土壤发育提供宝贵的参考。该方法涉及在不同年龄和母体材料的土壤中，水溶性氧，硫酸盐和硝酸盐中硫，氧和氮的同位素分析。使该提案成为可能的突破是最近在干山谷土壤中发现了硫酸盐和硝酸盐的质量非依赖性氧成分，这表明大气沉积随着时间的推移贡献了大量的硫酸盐和硝酸盐，并随着时间的推移贡献了硝酸盐。 PI的最新工作确定了在干山谷土壤中硫酸盐的氧 - 异位素组成中的空间模式，并且需要存在两个硫酸盐最终成员，硫酸盐硫酸盐和生物硫酸盐。在这里，生物硫酸盐是指通过在大气中氧化的生物生物硫气（例如二甲基硫化物）氧化而形成的硫酸盐。生物硫酸盐由于其长期停留时间可以相对于硫酸盐的距离更大的距离。该项目中将进行的氧气和硫的同位素分析将在干谷土壤中区分生物硫酸盐和硫酸盐。此外，这些土壤中硝酸盐的氧氧组成的初步数据显示出极大的硝酸盐氧气17异常和空间模式，该空间模式反映了单个硝酸盐来源，而不是两个来源，而不是硫酸盐。为了量化硫酸盐和硝酸盐的长期大气输入及其随后在这种独特环境的土壤中的迁移率，该项目将（1）以厘米至sub-centimcale的分辨率进行样品垂直土壤剖面，（2）系统地分析氧气的氧气。以及硝酸盐中硫酸盐，氧和氮同位素中的硫同位素，（3）检查各种辐射年龄和母材料的土壤，包括古代火山灰，岩石，colluvium，lodgment tills和Ice-ublinimation tills，以及（4）结构的构造耕种一个简单的一维运输模型，用于垂直土壤剖面中的硫酸盐和硝酸盐。该项目代表了低温同位素地球化学家与在干山谷地区具有丰富经验的地貌学家之间的协作。当与过去15年中干谷土壤的现有辐射同位素年表结合使用时，拟议的稳定同位素分析将首次量化土壤发育的速率和样式，以及干谷地区的土壤发展的速度和样式。这些定量数据对于实现对干山谷生态系统的透彻了解和建立基线数据以与对火星的预期分析进行比较至关重要。