"Particle Radio-sensor": Development of in situ particulate radioactivity sensor

海洋自养生物的碳固定代表了水泥工业和化石燃料燃烧释放到大气中的碳的显著(~26%)汇。通过浮游生物的光合作用吸收，无机碳(CO2)被吸收成生物物质。这种生物材料絮凝并下沉，然后在海洋混合层中重新矿化，或者被输出到海洋更深的层进行长期的封存(生物碳泵)。了解有多少这种颗粒物质被转移到深海，对于量化海洋将在改善人为大气二氧化碳排放方面发挥的作用，从而减少气候变化具有重要意义。这些颗粒输出通量可使用包括放射化学示踪剂和沉积物捕集在内的多种方法进行量化。在现有的放射化学技术中，第234次的使用是最常用的。234很容易附着在粒子上，再加上它的半衰期很短(24.1天)，使它成为通过海柱下沉的粒子的理想示踪剂。传统上，使用大容量(由于海洋中通常发现的低颗粒物第234活动)原位泵来收集颗粒，这使得这种方法非常劳动密集型，而且在过滤期间还需要长时间的静止船舶。这导致该变量在海洋中的严重抽样不足，导致报告的生物碳泵的大小不一致。现场传感器，如用于Argo浮标和滑翔机的传感器，已经对海洋物理和化学产生了变革，但类似的颗粒传感器和采样器并不存在。这项技术提案试图通过将现场颗粒通量仪器的概念引入TRL 4来解决这一数据差距。这将通过开发现场过滤系统并将其与新的可部署的贝塔检测模块相结合来实现，以测量颗粒234的活度。这将为进一步提高该装置的TRL并将创新技术原理应用于其他海洋变量(即溶解相放射性核素；其他放射性核素)奠定基础。使用自动飞行器以高空间和时间分辨率轻松采样公海通量的能力，将使我们在不断变化的海洋中测量碳输出(脱氧、酸化)的能力发生阶段性变化，并帮助科学家评估大气二氧化碳浓度增加的长期影响。

Carbon fixation by marine autotrophs represents a significant (~26%) sink of the carbon released to the atmosphere from the cement industry and burning of fossil fuels. Inorganic carbon (CO2) is assimilated into biological material via photosynthetic uptake by plankton. This biological material flocculates and sinks, and is either remineralised within the ocean mixed layer or exported to deeper layers of the ocean for long term sequestration (the 'biological carbon pump'). Understanding how much of this particulate material is transferred to the deep ocean is important in quantifying the role the oceans will play in ameliorating anthropogenic atmospheric emissions of CO2, and hence climate change. These particulate export fluxes can be quantified using a number of approaches including radiochemical tracers and sediment trapping. Of the radiochemical techniques available, the use of 234Th is the most commonly applied. The 234Th readily adheres to particles, and combined with its short half-life (24.1 days) make it an ideal tracer of particles sinking through the ocean column. Traditionally, large volume (owing to the low particulate 234Th activities typically found in the oceans) in situ pumps are employed to collect particles making this method very labour intensive, and also requiring long periods of static ship during filtration periods. This leads to gross under-sampling in the oceans of this variable, leading to inconsistencies reported for the magnitude of the biological carbon pump. In situ sensors such as those used on Argo floats and gliders have been transformative for marine physics and chemistry, but analogous particulate sensors and samplers do not exist. This technology proposal seeks to address this data gap by taking the concept of an in situ particulate flux instrument to TRL 4. This will be achieved by developing an in situ filtration system and coupling this with a novel deployable beta detection module to measure particulate 234Th activity. This will provide the foundations for further work to raise the TRL of this device and to apply the innovative technology principles to other oceanic variables (i.e. dissolved phase radionuclides; other radionuclides). The ability to easily sample open ocean fluxes using autonomous vehicles at high spatial and temporal resolution would constitute a step-change in our ability to measure carbon export in a changing ocean (deoxygenation, acidification) and help scientists assess the long term effect of increasing atmospheric CO2 concentration.