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转变为农田的硫添加。现在，像氮和磷一样，大量的S也作为肥料或其他土壤添加剂施用于某些作物。在空气质量政策导致大气中S含量下降的地区，农民现在添加S肥料以满足植物的需求。通常是《清洁空气法》颁布前降雨中S含量的2到10倍，在农田中施用S可能对下游地区产生负面影响。特别是，过量的S进入湿地会导致重金属进入食物链，这对动物和人类都是危险的。目前还没有关于农业添加物在环境中的表现及其使用后果的深入研究。本项目将通过解决三个主要目标来填补这一知识空白。首先是发展科学的方法来测量作物系统中关键的S循环过程和化学形式。第二是创造练习，为中学生和大学生提供做环境研究的经验。最后的目标是为农民举办研讨会，讨论研究成果并为作物管理提供信息。总之，这些活动将增进理解，促进互动，以解决人类如何改变S周期。拟议的研究解决了生物地球化学领域的一个主要知识缺口：量化农业系统中活性S添加物在环境中的行为，并调查控制其最终命运和生态后果的过程。早期的职业生涯PI将建立在她在纳帕河流域（美国加利福尼亚州）的研究基础上，这是一个完美的区域农业系统，专门种植酿酒葡萄，S被普遍应用，平均每年150公斤。她设计了一个重点领域和实验室为基础的调查，依靠她在生物地球化学方面的背景，并利用她不断增长的学术和利益相关者合作者网络，在她的研究小组、研究领域和农业部门内建立能力。具体而言，该项目将在三个主要领域增加科学知识：(1)开发量化土壤微团聚体硫酸盐还原的方法；(2)测定农业系统输出有机S的化学和S稳定同位素组成；(3)确定土壤和溶液中S和S稳定同位素组成的形式是如何变化的，不仅在一个农业区（纳帕河流域），而且在美国其他大量使用S的农田。结合研究活动，PI将领导以下教育和推广工作：(1)为Silverado中学的280名七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孩子；(2)设计一个公开可用的案例研究模块，为环境专业的本科生培养定量和批判性思维技能；(3)利用与科罗拉多可持续发展创新实验室和加州大学推广部的合作，举办利益相关者研讨会，交流项目成果，并为可持续管理提供解决方案。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，这一努力将产生对S在何处、何时以及如何在环境中起作用的广泛理解——推进人类如何改变基本元素循环的知识，并告知如何应对。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。

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.