EAGER SitS:Multimodal gas sensor for in situ methane and carbon dioxide detection in Arctic soils

北极冻土带含有大量的土壤有机质(SOM)，地球上大约一半的SOM与高纬度生态系统中的永久冻土有关。随着气温的升高，北极土壤有机质一直在解冻和加速微生物降解，产生大量的活性有机碳和温室气体(如二氧化碳和甲烷)。准确测量冻土带这些气体排放的当前水平至关重要，这是未来测量和更准确地模拟北极SOM变暖可能产生的影响的基线。然而，北极冻土带是一个复杂的多相系统，每年土壤温度可能会保持在冰点以下8个月甚至更长时间，这使得野外条件下土壤气体排放的检测变得极其困难。目前的传感器技术不足以准确测量北极土壤中的温室气体。该项目将开发一种低成本、低功率的多模式传感器，可以在空间和时间上扩展、连续地原位测量整个北极地区土壤二氧化碳和甲烷随时间的动态变化。设想中的传感器将体积小、价格便宜，并且运行所需的电力很少。它可以部署在广泛的地区，以获取自然条件下的土壤气体数据，并将能够全年近乎实时地报告现场测量数据。来自这些传感器的数据将有助于促进几个学科的知识，例如了解永久冻土变暖对北极土壤碳释放的影响，以及北极生态系统中基本的生物地球化学或碳循环过程。这一新知识将有助于开发管理寒冷环境中土壤和自然资源的新方法。该项目将由一个具有互补专业知识的现有跨学科团队实施，以开发新的传感器技术，以应对北极土壤气体分析方面的挑战。关键的创新是使用离子液体(ILS)作为选择性溶剂和电解液，开发出小型化的多模式电化学和压电石英晶体微天平(E-QCM)传感器，用于土壤气体的现场测量。ILS具有独特的溶剂和电解质特性，使其适合在北极条件下使用，因为在北极条件下，传统的传感材料会同时受到物理和化学变化的影响。该项目将(1)开发用于北极条件下甲烷和二氧化碳检测的多模式E-QCM传感器和传感器阵列；(2)使用已知成分的合成北极土壤来表征和验证这些传感器阵列；以及(3)开发用于在北极天然土壤中进行现场测试的坚固耐用的传感器包。新传感器预计将在北极条件下工作，同时监测土壤甲烷和二氧化碳的电化学和压电信号，并具有现场测量北极冻土地带土壤气体所需的冗余性、灵敏度和选择性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Arctic tundra contains a large amount of soil organic matter (SOM), and approximately half of Earth's SOM is associated with permafrost in high-latitude ecosystems. Arctic SOM has been undergoing thawing and accelerated microbial degradation as temperatures increase, producing large amounts of active organic carbon and greenhouse gases (e.g., carbon dioxide and methane). It is vital to measure current levels of these gas emissions from the tundra accurately, as a baseline for future measurements and for more accurate modeling of likely effects from the increased warming of Arctic SOM. However, the Arctic tundra is a complicated multi-phase system, and soil temperatures may stay below freezing for eight months or more every year, making the detection of soil gas emissions extremely difficult under field conditions. Current sensor technologies are inadequate for making accurate measurements of greenhouse gases in Arctic soils. This project will develop a low-cost, low-power multimodal sensor that can provide spatially and temporally expansive, continuous in situ measurements of dynamic changes of soil carbon dioxide and methane across the Arctic over time. The envisioned sensor will be small, inexpensive, and will need little power for operation. It can be deployed across wide areas to obtain soil gas data in natural conditions and will enable near-real-time reporting of field measurement data year-round. Data from these sensors will help advance knowledge in several disciplines, such as understanding the influence of permafrost warming on Arctic soil carbon release, and the fundamental biogeochemical or carbon cycling processes in the Arctic ecosystem. That new knowledge will help facilitate the development of new ways of managing soils and natural resources in cold environments.This project will be carried out by an established interdisciplinary team with complementary expertise to develop the new sensor technology to address challenges in Arctic soil gas analysis. The key innovation is the use of ionic liquids (ILs) as a selective solvent and electrolyte for the development of miniaturized multimodal electrochemical and piezoelectric quartz crystal microbalance (E-QCM) sensors to measure soil gases in situ. ILs possess unique solvent and electrolyte properties that make them suitable for use under Arctic conditions where conventional sensing materials would be subject to both physical and chemical changes. The project will (1) Develop a multimodal E-QCM sensor and sensor array for methane and carbon dioxide detection under Arctic conditions; (2) Characterize and validate these sensor arrays using synthetic Arctic soils with known composition; and (3) Develop a rugged sensor package for in situ field tests in natural Arctic soils. The new sensors are expected to operate under Arctic conditions, simultaneously monitoring both electrochemical and piezoelectric signals of soil methane and carbon dioxide with the redundancy, sensitivity, and selectivity required for in situ measurement of soil gases in Arctic tundra.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.