CAREER: Acid Rain to Agriculture: An Integrated Research and Education Platform to Understand Human Manipulation of the Sulfur Cycle

人类对硫（S）循环的改变正在从采矿和化石燃料排放到农田中的硫添加。现在，与氮和磷类似，大量的硫也被用作肥料或其他土壤添加剂。由于空气质量政策，在大气硫沉积减少的地方，农民现在添加硫肥以满足植物的需求。在《清洁空气法》颁布之前，雨水中的硫含量通常是前者的两到十倍，农田中的硫可能会对下游地区产生负面影响。特别是，运输过量的S进入湿地可能会导致重金属进入食物链，这对动物和人类都是危险的。农业硫添加剂在环境中的行为及其使用后果尚未得到深入研究。该项目将通过解决三个主要目标来填补这一知识空白。第一是发展科学方法来测量作物系统中关键的S循环过程和化学形态。第二是创造练习，为中学生和本科生提供环境研究的经验。最终目标是为农民举办研讨会，讨论研究结果并为作物S管理提供信息。总之，这些活动将提高理解和促进互动，以解决人类如何改变S循环。拟议的研究解决了地球化学领域的一个主要知识缺口：量化反应性S添加到农业系统中在环境中的行为，并调查控制其最终命运和生态后果的过程。PI的早期职业生涯将建立在她在纳帕河流域（美国加州）的研究基础上-这是一个完美的区域农业系统，酿酒葡萄只种植，S的平均施用量为150 kg ha-1 yr-1。她设计了一个重点领域和实验室为基础的调查，依赖于她在地球化学的背景，并利用她不断增长的学术和利益相关者合作者网络，以建立她的研究小组，研究领域和农业部门的能力。具体而言，PI将增加三个主要领域的科学知识：（1）开发方法来量化土壤微团聚体中的硫酸盐还原;（2）确定农业系统输出的有机S的化学和S稳定同位素组成;（3）确定土壤和溶解沃茨中S的形态和S稳定同位素组成的变化，（纳帕河流域），但也在其他农田在美国，S是使用严重。与研究活动相结合，PI将领导以下教育和外展工作：（1）为西尔维拉多中学的280名7年级学生创建基于工作的学习实地考察和数据探索练习，其中约60%的学生是西班牙裔，许多是当地农业工人的子女;（2）设计一个公开的案例研究模块，为本科环境研究学生建立定量和批判性思维能力;以及（3）利用与科罗拉多可持续创新实验室和加州大学扩展部的合作，举办利益相关者研讨会，交流项目发现并为可持续的S管理提供解决方案。此外，PI将继续致力于从代表性不足的群体中招募学生参与该项目，并培养他们成为下一代跨学科学者。最终，这一努力将产生一个广泛的理解，在哪里，何时，以及如何S在环境中的反应，推进人类如何改变一个基本的元素循环的知识，并告知如何做它。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Humans’ changes to the sulfur (S) cycle are changing from mining and fossil fuel emissions to sulfur additions in croplands. Now, similar to nitrogen and phosphorus, large amounts of S are also applied to some crops as fertilizers or other soil additives. In locations where atmospheric S deposition is down due to air quality policies, farmers now add S fertilizers to meet plant requirements. Often two-to-ten times the amount of S that was in rain before the Clean Air Act, S applications to croplands may have negative consequences for areas downstream. In particular, transport of excess S into wetlands can cause movement of heavy metals into the food chain, which is dangerous for animals and people. There has not been thorough study of how agricultural S additions behave in the environment and the consequences of their use. This project will fill that knowledge gap by addressing three primary objectives. The first is to develop scientific methods to measure key S cycling processes and chemical forms in crop systems. The second is to create exercises that provide middle school and undergraduate students with experience doing environmental research. The final objective is to hold workshops for farmers to discuss research findings and inform crop S management. Together, these activities will improve understanding and promote interaction to address how humans are changing the S cycle.The proposed research addresses a major knowledge gap in the field of biogeochemistry: quantifying how reactive S additions to agricultural systems behave in the environment and investigating the processes that control their ultimate fates and ecological consequences. The early career PI will build on her body of research in the Napa River Watershed (California, USA)—a perfect regional agricultural system where wine grapes are grown exclusively and S is applied ubiquitously at 150 kg ha-1 yr-1, on average. She has designed a focused field- and laboratory-based investigation that relies on her background in biogeochemistry and leverages her growing network of academic and stakeholder collaborators to build capacity within her research group, field of study, and the agricultural sector. Specifically, the PI will increase scientific knowledge in three main areas: (1) developing methods to quantify sulfate reduction in soil microaggregates; (2) determining chemical and S stable isotopic composition of organic S exported from agricultural systems; and (3) identifying how the forms of S and S stable isotopic composition of soils and solution waters vary not only across one agricultural area (the Napa River Watershed) but also across other croplands in the U.S. where S is used heavily. Integrated with the research activities, the PI will lead the following education and outreach efforts: (1) creating work-based learning field trips and data exploration exercises for 280 7th grade students at the Silverado Middle School where ~60% of the students are Hispanic and many are the children of workers in the local agricultural industry; (2) designing a publicly-available case study module that builds quantitative and critical thinking skills for undergraduate environmental studies students; and (3) leveraging collaborations with the Sustainability Innovation Lab at Colorado and University of California Extension to hold stakeholder workshops that communicate project findings and inform solutions for sustainable S management. In addition, the PI will continue her commitment to recruiting students from underrepresented groups to participate in this project and train them to become the next generation of interdisciplinary scholars. Ultimately, this effort will yield a broad understanding of where, when, and how S reacts in the environment—advancing knowledge of how humans are changing a fundamental element cycle and informing what to do about it.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.