Development of a High-throughput, Temperature-controlled LED-based Instrument to Characterize the Wavelength Dependence of Photochemical Reactions in Aquatic Ecosystems

水生光化学是一个跨学科领域，研究阳光驱动的反应如何影响地表水中各种物质的命运和组成，包括主要和次要元素，无机和有机污染物以及生物分子。可以说，水生光化学学科中最大的知识差距是阳光驱动反应的波长依赖性。也就是说，虽然人们对一系列可能的反应已经相当了解，但对反应效率和速率如何随波长变化的了解是有限的，这主要是由于当前仪器的主要缺点。该项目旨在通过设计、开发和验证一种基于发光二极管（LED）的仪器来克服这些缺点，该仪器可以提高样品吞吐量，提供更宽的太阳光波长范围来探测，可以控制温度，并且是现场便携式的。研究人员期望，这种新仪器将使人们对自然和工程系统中各种光化学反应的波长依赖性的认识迅速增长，从而提高对光化学反应速率的时空估计。这些研究人员将在伍兹霍尔海洋研究所的社区大学研究经验项目中担任导师，该项目旨在促进社区大学学生的海洋科学、技术和工程技能以及能力建设，而社区大学学生是一种被低估和未充分利用的有才华和多样化的本科生资源。准确评估地表水的光化学反应动力学需要了解整个水柱中不同波长的可用光以及光化学反应效率，或在这些波长下的表观量子产率（AQY； mol-1光吸收的摩尔产物）。然而，目前表征AQY光谱的方法有许多缺点，包括成本、样品吞吐量、易用性和便携性。研究人员已经开发并验证了一个原型反应器组件，可以直接探测水生光化学反应的AQY光谱。该原型使用紫外线和可见led来产生高功率，窄带状和空间均匀的辐照度。在这个项目中，研究人员将通过设计、开发和验证一种新的电子控制仪器来扩大和改进原型，该仪器的样品容量增加了四倍，光功率至少增加了十倍，波长范围从UV-C扩展到可见光区域，温度控制，并且可在现场携带。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。

Aquatic photochemistry is an interdisciplinary field that examines how sunlight-driven reactions impact the fate and composition of diverse materials in surface waters, including major and minor elements, inorganic and organic pollutants, and biomolecules. Arguably the largest knowledge gap in the aquatic photochemistry discipline is the wavelength dependence of sunlight-driven reactions. That is, while the suite of possible reactions is reasonably well understood, knowledge of how the reaction efficiencies and rates vary by wavelength is limited, largely owing to key shortcomings of current instrumentation. This project aims to overcome these shortcomings by designing, developing, and validating a light-emitting diode (LED) based instrument that improves sample throughput, offers a wider range of sunlight wavelengths to probe, is temperature-controlled, and is field portable. The researchers expect that this new instrument will permit rapid growth in knowledge about the wavelength dependence of a wide variety of photochemical reactions in natural and engineered systems, and, consequently, improve estimates of photochemical reaction rates across space and time. The researchers will serve as a mentor in the Community College Research Experiences at Woods Hole Oceanographic Institution, a program focused on promoting ocean science, technology, and engineering skills and capacity building among community college students, an underappreciated and underutilized resource of talented and diverse undergraduates. Accurate assessment of photochemical reaction kinetics in surface waters requires knowledge about the light available at different wavelengths throughout the water column and the photochemical reaction efficiency, or apparent quantum yield (AQY; mol product mol-1 light absorbed) at those wavelengths. However, current approaches to characterize AQY spectra have many disadvantages, including costs, sample throughput, ease of use, and portability. The researchers have developed and validated a prototype reactor assembly to directly probe AQY spectra of aquatic photochemical reactions. The prototype uses ultraviolet (UV) and visible LEDs to generate high power, narrow banded, and spatially uniform irradiance. In this project, the researchers will scale-up and improve upon the prototype by designing, developing, and validating a new instrument that is electronically-controlled, has upward of a four-fold greater sample capacity, has at least ten-fold higher optical power, has an extended wavelength range from the UV-C to the visible light region, is temperature-controlled, and is field portable.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.