Additions of Physical and Biogeochemical Tracers to Wetland Soils Can Reveal Mechanisms Underlying the Productivity-Methane Emission Relationship

甲烷是一种重要的温室气体，主要从湿地排放。气候变化科学中最大的不确定性之一是，全球变暖可能会在多大程度上改变导致甲烷排放的土壤过程。由于直接观察控制甲烷排放速率的植物和微生物过程本身就很困难，科学家们依赖间接证据(实验室或其他高度干扰样本的快照措施)来预测未来的甲烷排放。我们将首次对甲烷生产、消费和运输这三个直接控制甲烷排放的过程进行直接、长期的实地测量，并将这些过程与更广泛的控制联系起来。我们工作的新颖性来自于使用一套惰性和生物示踪剂来测量几周或几个月的土壤过程，而不会干扰系统。我们将通过将已标记的甲烷(作为非放射性同位素)释放到湿地土壤中并随后监测该标记的相对丰度来测量甲烷的生产和消费。为了解决由于传输到大气或湿地中的流水稀释而造成的标签的非生物损失，我们共同添加了惰性气体和水文示踪剂。有趣的是，我们将是第一个使用康奈尔大学纳米制造设施建造的单独标记的纳米球来测量水流的人。

Methane is an important greenhouse gas that is primarily emitted from wetlands. Among the greatest uncertainties in climate change science is the degree to which global warming may alter the soil processes that lead to methane emission. Because it is inherently difficult to directly observe the plant and microbial processes that govern methane emission rates, scientists have depended on indirect evidence (laboratory or other snapshot measures on highly disturbed samples) to predict future methane emissions. We will, for the first time, make direct, long-term field measurements of methane production, consumption and transport, the three processes that proximately regulate methane emission, and relate those processes to their broader-scale controls. The novelty of our work derives from use of a suite of inert and biological tracers to measure soil processes over weeks or months without disturbing the system. We will measure methane production and consumption by releasing methane that has been labeled (as a non-radioactive isotope) into wetland soils and subsequently monitoring the relative abundance of that label. To account for non-biological loss of the label due to transport to the atmosphere or dilution by flowing water in the wetland, we co-add an inert gas and a hydrologic tracer. Interestingly, we will be the first to measure water flow using individually-labeled nanospheres, constructed at Cornell University's nanofabrication facility.