Using novel genetic and isotopic techniques to understanding how microbial activity affects rates of dissolution of the mineral olivine.

使用新颖的遗传和同位素技术来了解微生物活动如何影响矿物橄榄石的溶解速率。

• 批准号: 1324929
• 负责人: A Joshua West
• 金额: $ 12.46万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-06-01 至 2019-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1324929&HistoricalAwards=false
• 关键词: Using; novel; genetic; isotopic; techniques

The results of this research will advance basic understanding in the Earth sciences and will have practical implications for understanding Earth's carbon cycle and the potential for carbon sequestration in mineral substrates. The chemical breakdown of minerals ("mineral dissolution") regulates the availability of carbon and other nutrient elements across a range of scales in space and time. This means that understanding mineral dissolution is fundamental to the study of the Earth system, and particularly to the study of Earth's climate and biosphere. The rate at which minerals dissolve is known to depend on a number of factors. Of these, the roles of biological activity and the approach to thermodynamic equilibrium remain particularly poorly understood. This knowledge gap stands in the way of efforts to develop models that scale laboratory observations to field conditions and makes it difficult to use the results from experimental studies to address large-scale Earth system problems. Meanwhile studies of weathering in natural systems are often confounded by multiple variables. The project proposed here will use novel experimental methods to take a major step forward in understanding how microbial activity and the approach to equilibrium affect the dissolution rate of the silicate mineral olivine. Olivine plays a key role in the carbon cycle as a primary constituent of highly weatherable rocks, and has been proposed as a substrate for carbon dioxide sequestration, making it a noteworthy mineral for focused investigation.Numerous field observations have shown that biological activity drives higher increased silicate weathering rates, but a mechanistic understanding is lacking because prior experimental efforts have been complicated by variations in the activity and phenotypic expression of organisms within and between experiments. To minimize this variability, experiments in the proposed study will be preformed using microorganisms with targeted genetic mutations. With this approach, the effects of a single microbial process can be isolated and quantified over a range of environmental conditions, allowing for a more robust determination of the effects of biological activity on olivine dissolution rates than have previously been possible. The dependence of mineral dissolution rates on the departure from thermodynamic equilibrium is a critical factor that controls dissolution rates in natural environments. Theoretical predictions vary significantly in both the functional form of the thermodynamic equilibrium dependence as well as the value of the thermodynamic equilibrium at which a significant change in rate is observed. For olivine, near-equilibrium experiments are complicated because solutions become supersaturated with respect to secondary magnesium silicate minerals that precipitate at non-negligible rates, making it impossible to quantify dissolution rates using standard methodologies. To circumvent this problem, a novel method of determining dissolution rates by isotope dilution will be used to study the near equilibrium dissolution kinetics of olivine.The project will support the training of a doctoral student, who will supervise high school students from traditionally underrepresented backgrounds. The doctoral student will also lead the development of a laboratory exercise that demonstrates the carbon dioxide sequestration potential of the mineral olivine while teaching basic science concepts. This exercise will be incorporated into a display at the University of Southern California and will be provided free of charge over the Internet for educational use at other institutions.

这项研究的结果将促进对地球科学的基本了解，并将对了解地球的碳循环和矿物基质中碳固定的潜力具有实际意义。矿物的化学分解(“矿物溶解”)调节着碳和其他营养元素在空间和时间尺度上的可用性。这意味着了解矿物溶解对研究地球系统，特别是研究地球气候和生物圈是基本的。众所周知，矿物的溶解速度取决于许多因素。其中，生物活动的作用和达到热力学平衡的方法仍然知之甚少。这一知识差距阻碍了开发按现场条件进行实验室观测的模型的努力，并使其难以利用实验研究的结果来解决大规模的地球系统问题。同时，自然系统中风化作用的研究常常被多个变量混淆。这里提出的项目将使用新颖的实验方法，在了解微生物活动和达到平衡的方法如何影响硅酸盐矿物橄榄石的溶解速度方面向前迈进一大步。橄榄石作为高度风化岩石的主要成分，在碳循环中起着关键作用，已被提议作为二氧化碳封存的基质，使其成为值得重点研究的矿物。大量的野外观察表明，生物活动推动了更高的硅酸盐风化速率，但缺乏机理了解，因为先前的实验工作因实验内和实验之间生物体的活动和表型表达的变化而变得复杂。为了最大限度地减少这种变异性，拟议研究中的实验将使用具有靶向基因突变的微生物进行。通过这种方法，可以在一系列环境条件下分离和量化单个微生物过程的影响，从而能够比以前更可靠地确定生物活性对橄榄石溶解速度的影响。矿物溶解速率与偏离热力学平衡的关系是控制自然环境中矿物溶解速率的关键因素。无论是热力学平衡依赖的函数形式，还是观察到速率发生显著变化的热力学平衡值，理论预测都有很大的不同。对于橄榄石，近平衡实验是复杂的，因为溶液相对于以不可忽略的速度沉淀的次生硅酸镁矿物变得过饱和，使得无法使用标准方法来量化溶解速度。为了绕过这个问题，将使用一种通过同位素稀释法确定溶解速度的新方法来研究橄榄的近平衡溶解动力学。该项目将支持一名博士生的培训，该博士生将指导来自传统上代表性较低的背景的高中生。这位博士生还将领导开展一项实验室练习，在教授基础科学概念的同时，展示矿物橄榄石的二氧化碳固定潜力。这项活动将被纳入南加州大学的展示中，并将通过互联网免费提供，供其他机构教育使用。