Carbon Dioxide Generation in the Soil-Vadose Continuum: Substrate Characteristics and Residence Times

土壤渗流连续体中二氧化碳的生成：基质特性和停留时间

• 批准号: 9219788
• 负责人: C. Kent Keller
• 金额: --
• 依托单位: Washington State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-03-01 至 1996-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9219788&HistoricalAwards=false
• 关键词: Carbon; Dioxide; Generation; Soil; Vadose

Fixation of atmospheric CO2 by plants and mineralization of the fixed C (CO2 production) by respiring biological communities link the soil and atmospheric C reservoirs in a dynamic equilibrium. Resent hydrogeological research has shown that CO2 production also occurs in subsoil vadose zones and that its short-term and long- term impacts on the terrestrial-atmospheric C balance can be substantial. Therefore the effort to predict the consequences of perturbations to the soil C reservoir must now be extended to subsoil vadose zones. This means that controls on CO2 production in the entire soil-vadose continuum must be identified the understood. One key control on subsurface CO2 production is the availability of organic C to support respiration. Here we will study characteristics and mean residence times (MRT) of this C, and how these parameters vary in two contrasting geologic settings beneath temperate grasslands. Determination of the 14C age of the CO2 produced at various depths will identify modern, pedogenic, and ancient C sources, provide estimates of depth variation of MRT of the C sources, and thereby also provide estimates of the time required production in the soil-vadose continuum. We hypothesize that it if possible to isolate and characterize a fraction of C in soil-vadose geologic material which can be identified as respiration substrate by its C isotope signature. Such identification would yield new insight into the types of organic C serving as respiration substrates and their evolution with depth. It may also provide methodological basis for construction of substrate MRT-vs-depth functions using a relatively simple isolation procedure.

植物对大气CO2的固定和生物群落对固定C的矿化（CO2生产）使土壤和大气碳库处于动态平衡状态。最近的水文地质研究表明，二氧化碳的产生也发生在地下渗透带，其对陆地-大气碳平衡的短期和长期影响可能是巨大的。因此，预测扰动对土壤C库的影响的努力现在必须扩展到地下渗透带。这意味着必须确定整个土壤-水汽连续体中对二氧化碳产生的控制。控制地下二氧化碳产生的一个关键因素是支持呼吸作用的有机碳的可用性。在这里，我们将研究这种碳的特征和平均停留时间（MRT），以及这些参数在温带草原下两种不同地质环境下的变化情况。测定不同深度产生的二氧化碳的14C年龄将确定现代的、成土的和古代的碳源，提供对碳源MRT深度变化的估计，从而也提供对土壤-渗透连续体中所需生产时间的估计。我们假设，如果有可能从土壤渗透地质物质中分离和表征一部分C，这些C可以通过其C同位素特征识别为呼吸底物。这种鉴定将对作为呼吸底物的有机碳的类型及其随深度的演变产生新的见解。它还可以为使用相对简单的分离程序构建基质MRT-vs-depth函数提供方法学基础。