CAREER: Unlocking Recalcitrant Carbon to Enhance Denitrification of Nonpoint Source Nitrogen in Woodchip Bioreactors

来自农业和雨水径流的硝酸盐等非点源氮(N)是美国污染和水质损害的最难处理的驱动因素之一，导致富营养化、有害藻华和缺氧，对国家地表水系的生态健康、经济和娱乐价值产生不利影响，包括湖泊、河流和切萨皮克湾和墨西哥湾等大型河口。木片生物反应器(WBRs)已成为去除农业径流和雨水中硝酸盐的一种很有前途的可扩展的生物过滤系统。大多数WBR由地下沟渠组成，沟内填充碳源(木屑)，旨在刺激微生物反硝化作用(DN)，以便在径流排放到接收地表水系统之前从流动的径流中去除硝酸盐。目前的WBR的有效性受到木片介质中生物可用碳(C)缓慢释放的限制，这些C是支持DN细菌生长和代谢所需的。这个职业项目的首要目标是探索、阐明和利用氧化还原生物地球化学反应，这些反应控制着木片介质中生物可用C的释放和动员，以刺激WBR中的糖尿病肾病。为了推进这一目标，首席研究员建议检验这样一种假设，即木片生物反应器运行期间的缺氧-缺氧循环通过在好氧期加速顽固的木质纤维素木屑生物质分解为活性C来促进反硝化作用，从而在随后的缺氧期刺激DN微生物的生长和代谢活动。该项目的成功完成将使社会受益，因为它将产生新的基础知识，以支持开发和部署更有效和可持续的解决方案，以管理和减轻硝酸盐污染的非点源。还将通过学生教育和培训，包括指导康奈尔大学的一名研究生，为社会带来更多好处。铁(Fe)和锰(Mn)矿物在氧化还原界面上的生物地球化学反应在环境中木质纤维生物质的分解中起着重要的作用，对这些有机-矿物相互作用的机理认识正在迅速发展。这个职业项目将研究和揭示控制木片介质降解过程中不稳定碳(C)释放的氧化还原活性生物地球化学反应，目的是利用这一新知识来改善木片生物反应器(WBR)的性能，该装置利用LB作为碳源来刺激反硝化(DN)微生物的生长，从而从农业和雨水径流中去除硝酸盐。这项研究的具体目标是：1)利用最先进的表征技术，包括基于同步辐射的光谱和显微镜(如Micro-XANES和Micro-XRF)和先进的质谱学(如FT-ICR MS)，探索和阐明控制模型WBR中木片介质中溶解有机碳(DOC)释放的锰和铁驱动的氧化还原反应；2)评估和评价酶和非酶转化对模型WBR中木片介质中DOC释放的数量和质量的影响；3)开发和验证基于过程的模型，模拟氧化还原波动和循环对流通式WBR中DOC和DN效率的影响。该项目的成功完成有可能产生变革性的影响，通过产生新的基本知识来推动设计和实施更有效的水资源回收利用系统，以去除农业和雨水径流中的硝酸盐。为了实施这一职业项目的教育和外展活动，首席调查员(PI)建议利用康奈尔大学现有的课程和资源，为来自代表性不足群体的学生开发和提供新的环境工程(EE)实践体验学习机会。拟议的活动将包括i)面向纽约州中部农村地区的高中生和教师的外展计划，以及ii)面向本科生和社区大学学生的暑期培训和辅导计划。此外，PI建议利用项目资源和研究成果，开发新的课程模块，并将其整合到康奈尔大学EE本科课程中，内容涉及用于去除氮污染的水基础设施系统的传感和控制。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。

Nonpoint sources of nitrogen (N) such as nitrate from agricultural and stormwater runoff are among the most intractable drivers of pollution and water quality impairments in the United States, contributing to eutrophication, harmful algal blooms, and hypoxia, which adversely impact the ecological health, economic, and recreational values of the Nation’s surface water systems including lakes, rivers, and large estuaries such as the Chesapeake Bay and the Gulf of Mexico. Woodchip bioreactors (WBRs) have emerged as promising and scalable biofiltration systems for removing nitrate from agricultural and stormwater runoff. Most WBRs consist of subsurface trenches filled with a carbon source (woodchip) designed to stimulate microbial denitrification (DN) to remove nitrate from a flowing runoff stream prior to its discharge into a receiving surface water system. The effectiveness of current WBRs is limited by the slow release of the bioavailable carbon (C) from the woodchip media required to support the growth and metabolism of DN bacteria. The overarching goal of this CAREER project is to probe, elucidate, and leverage the redox biogeochemical reactions that control the release and mobilization of bioavailable C from woodchip media to stimulate DN in WBRs. To advance this goal, the Principal Investigator proposes to test the hypothesis that oxic-anoxic cycling during the operation of a woodchip bioreactor enhances denitrification by accelerating the decomposition of recalcitrant, lignocellulosic woodchip biomass into labile C during oxic periods to stimulate the growth and metabolic activity of DN microorganisms during subsequent anoxic periods. The successful completion of this project will benefit society through the generation of new fundamental knowledge to support the development and deployment of more efficient and sustainable solutions to manage and mitigate nonpoint sources of nitrate pollution. Additional benefits to society will be achieved through student education and training including the mentoring of a graduate student at Cornell University. Biogeochemical reactions of iron (Fe) and manganese (Mn) minerals at redox interfaces play an important role in the decomposition of lignocellulosic biomass (LB) in the environment, and mechanistic understanding of these organo-mineral interactions is rapidly evolving. This CAREER project will investigate and unravel the redox active biogeochemical reactions that control the release of labile carbon (C) from the degradation of woodchip media with the goal of leveraging this new knowledge to improve the performance of woodchip bioreactors (WBRs) that utilize LB as C source to stimulate the growth of denitrifying (DN) microorganisms to remove nitrate from agricultural and stormwater runoff. The specific objectives of the research are to 1) probe and elucidate Mn- and Fe- driven redox reactions that control the release of dissolved organic carbon (DOC) from woodchip media in model WBRs using state-of-the-art characterization techniques including synchrotron-based spectroscopy and microscopy (e.g., micro-XANES and micro-XRF) and advanced mass spectrometry (e.g., FT-ICR MS); 2) assess and evaluate the effects of enzymatic vs. nonenzymatic transformations on the quantity and quality of DOC released from woodchip media in model WBRs; and 3) develop and validate process-based models to simulate the effects of redox fluctuations and cycling on the release of DOC and DN efficiency in flow-through WBRs. The successful completion of this project has the potential for transformative impact through the generation of new fundamental knowledge to advance the design and implementation of more efficient WBRs for the removal of nitrate from agricultural and stormwater runoff. To implement the educational and outreach activities of this CAREER project, the Principal Investigator (PI) proposes to leverage existing programs and resources at Cornell University to develop and deliver new hands-on experiential learning opportunities in environmental engineering (EE) for students from underrepresented groups. The proposed activities will include i) an outreach program to high school students and teachers from rural areas of Central New York State and ii) a summer training and mentorship program for undergraduate and community college students. In addition, the PI proposes to leverage the project resources and research findings to develop and integrate new course modules on sensing and control of water infrastructure systems for nitrogen pollution removal into the EE undergraduate curriculum at Cornell University.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.