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

氮（N）的非点源（例如来自农业和雨水径流的硝酸盐）是美国污染和水质损害的最棘手的驱动因素之一，导致富营养化、有害藻类大量繁殖和缺氧，这对国家地表水系统（包括湖泊、河流、湖泊、湖泊、河流、湖泊和湖泊）的生态健康、经济和娱乐价值产生不利影响。以及大型河口，如切萨皮克湾和墨西哥湾。木屑生物反应器（WBR）已成为有前途的和可扩展的生物过滤系统，用于去除农业和雨水径流中的硝酸盐。大多数WBR由填充碳源（木屑）的地下沟渠组成，旨在刺激微生物反硝化作用（DN），以在将其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WBR的有效性受到支持DN细菌生长和代谢所需的木屑培养基中生物可利用碳（C）缓慢释放的限制。这个CAREER项目的总体目标是探索，阐明和利用氧化还原生物化学反应，控制木片介质中生物可利用C的释放和动员，以刺激WBR中的DN。为了推进这一目标，主要研究者提出了测试的假设，即在木片生物反应器的操作过程中，缺氧-缺氧循环，通过加速分解柠檬酸，木质纤维素木片生物质到不稳定的碳在好氧期间，以刺激DN微生物在随后的缺氧期间的生长和代谢活动，增强反硝化作用。该项目的成功完成将通过产生新的基础知识来支持开发和部署更有效和可持续的解决方案来管理和减轻硝酸盐污染的非点源，从而使社会受益。通过学生教育和培训，包括康奈尔大学一名研究生的辅导，将为社会带来更多好处。铁（Fe）和锰（Mn）矿物在氧化还原界面处的生物地球化学反应在环境中木质纤维素生物质（LB）的分解中起着重要作用，并且对这些有机矿物相互作用的机理理解正在迅速发展。这个CAREER项目将调查和解开控制不稳定碳（C）从木片介质降解释放的氧化还原活性生物化学反应，目的是利用这一新知识来提高木片生物反应器（WBR）的性能，利用LB作为C源来刺激微生物的生长，以去除农业和雨水径流中的硝酸盐。该研究的具体目标是：1）探测和阐明Mn和Fe驱动的氧化还原反应，该反应使用最先进的表征技术，包括基于同步加速器的光谱学和显微镜（例如，微XANES和微XRF）和高级质谱（例如，FT-ICR MS）; 2）评估和评价酶与非酶转化对模型WBR中木片介质释放DOC的数量和质量的影响; 3）开发和验证基于过程的模型，以模拟氧化还原波动和循环对流通式WBR中DOC释放和DN效率的影响。该项目的成功完成有可能通过产生新的基础知识来推动更有效的WBR的设计和实施，从而产生变革性的影响，以去除农业和雨水径流中的硝酸盐。为了实施这个职业项目的教育和推广活动，主要研究者（PI）建议利用康奈尔大学现有的项目和资源，为代表性不足的群体的学生开发和提供环境工程（EE）的新实践体验式学习机会。拟议的活动将包括：i）一个面向纽约州中部农村地区高中生和教师的外联方案; ii）一个面向本科生和社区学院学生的暑期培训和辅导方案。此外，PI建议利用项目资源和研究成果，开发和整合新的课程模块，对水基础设施系统的传感和控制，以去除氮污染到康奈尔大学的环境工程本科课程。该奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

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.