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），其中大约一半的土壤有机质与高纬度生态系统中的永久冻土有关。随着温度的升高，北极表层沉积物正在融化，微生物降解加速，产生大量的活性有机碳和温室气体（如二氧化碳和甲烷）。准确测量冻原目前的这些气体排放水平是至关重要的，这可以作为未来测量的基线，也可以更准确地模拟北极SOM升温可能产生的影响。然而，北极苔原是一个复杂的多相系统，土壤温度每年可能保持在冰点以下8个月或更长时间，这使得在野外条件下检测土壤气体排放极其困难。目前的传感器技术不足以精确测量北极土壤中的温室气体。该项目将开发一种低成本、低功耗的多模态传感器，该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。设想的传感器将是小的，便宜的，并且将需要很少的电力来操作。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，并将实现全年近实时的现场测量数据报告。来自这些传感器的数据将有助于推进几个学科的知识，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。这些新知识将有助于开发在寒冷环境中管理土壤和自然资源的新方法。该项目将由一个已建立的跨学科团队进行，并具有互补的专业知识，以开发新的传感器技术，以应对北极土壤气体分析中的挑战。关键的创新是使用离子液体（ILs）作为选择性溶剂和电解质，用于开发小型化多模态电化学和压电石英晶体微平衡（E-QCM）传感器，以原位测量土壤气体。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，在北极条件下，传统传感材料将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探测的多模态E-QCM传感器和传感器阵列；(2)利用已知成分的北极合成土壤对这些传感器阵列进行表征和验证；(3)开发一种坚固耐用的传感器包，用于在北极自然土壤中进行现场测试。新的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，具有北极冻土带土壤气体原位测量所需的冗余、灵敏度和选择性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.