Combine sensors, geophysical survey and geochemical tools to investigate pedogenic carbonate precipitation and carbon dioxide emission in irrigated soils of aridlands

边缘旱地已被改造成农田，以支持日益增长的粮食生产需求。在这些地区，密集的灌溉加上高蒸散量和有限的地下水补给，导致了农业用地上成土碳酸盐的积累和非生物二氧化碳的产生。这个项目将是首批量化这种非生物二氧化碳外流的项目之一，并确定沙漠农业土壤中洪水灌溉、盐分负荷和土壤-大气二氧化碳交换之间的关键联系。这个项目具有变革性，因为它研究了灌溉农业系统中成土碳酸盐的形成是如何影响地球上最大的生物群落之一的碳循环的，这是一个尚未得到充分研究但不断被人类活动放大的过程。更重要的是，该项目在全球范围内具有重要的社会经济意义，因为灌溉引起的盐积累和二氧化碳排放增加需要通过改进农业实践和管理来补救。该项目也与向美国西南部代表性人群推进STEM教育高度相关。它将为德克萨斯大学埃尔帕索分校（UTEP）的研究生和本科生提供关键区域科学、环境地球物理和同位素地球化学以及先进传感器技术的跨学科培训机会，该大学80%的学生是西班牙裔。该项目将直接资助两名博士和四名本科生，并为环境科学和地质学专业的学生提供实地体验和学习机会，包括为期两周的夏季实地考察。为了教育和推广，UTEP将在每年的“地球科学日”上进行实践活动，该活动通常会吸引约2000名公众参观。沿着里约热内卢格兰德山谷的三个农业遗址和一个自然遗址将在研究中进行检查，这些遗址是全球干旱地区的典型和代表性。地球化学、地球物理和同位素工具将与新设计的二氧化碳传感器相结合，以验证“灌溉沙漠土壤中形成的碳酸盐岩积聚向大气排放了一种重要的人为诱导的二氧化碳通量”这一总体假设。该项目将确定农业土壤中“自然形成”和“灌溉诱导”的成土碳酸盐，分离土壤气体中的“非生物”和“石油呼吸”二氧化碳，并在田间尺度上监测从陆地向大气排放的非生物二氧化碳的时空变化。通过确定主要控制因素（包括灌溉强度和化学成分、土壤质地和作物类型），本实地研究的预期数据集可以外推到更大的区域尺度，并提供关于灌溉农业改变陆地-大气碳交换潜力的第一个基本评估。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。

Marginal aridlands have been converted to farmlands to support increasing demand of food production. In these areas, intensive irrigation, coupled with high evapotranspiration and limited groundwater recharge, has led to accumulation of pedogenic carbonate and production of abiotic CO2 in agricultural lands. This project will be among the first to quantify such an abiotic CO2 efflux, and to define key linkages between flood irrigation, salt loading and soil-atmosphere CO2 exchange in desert agricultural soils. This project is transformative in that it examines how pedogenic carbonate formation in irrigated agricultural systems, an under-studied process but continuously magnified by human activities, impacts C cycling in one of the largest biomes on Earth. More importantly, this project has significant socioeconomic relevance at global scales, because irrigation-induced salt accumulation and elevated CO2 efflux need to be remediated through improved agricultural practice and management. This project is also highly relevant for advancing STEM education to representative population of the southwestern U.S. It will provide interdisciplinary training opportunities in Critical Zone Science, environmental geophysics and isotope geochemistry, and advanced sensor technology for both graduate and undergraduate students from primarily under-represented groups at the University of Texas at El Paso (UTEP) where 80% of student body is Hispanic. This project will directly support two Ph.D. and four undergraduate students, and provide field experience and learning opportunities to environmental science and geology majors, including two-week summer field trips. For education and outreach, hands-on activities will be presented at the annual "Earth Science Day" at UTEP, which generally attracts ~2000 visitors from the general public.Three agricultural sites and one natural site along the Rio Grande valley, that are typical and representative of aridland settings worldwide, will be examined in the study. Geochemical, geophysical and isotopic tools will be combined with newly designed CO2 sensors to test the overarching hypothesis that "pedogenic carbonate accumulation in irrigated desert soils emits an important anthropogenically induced flux of CO2 to the atmosphere." The project will identify "naturally formed" versus "irrigation-induced" pedogenic carbonate in agricultural soils, separate "abiotic" and "oil respired" CO2 in soil gases, and monitor the spatiotemporal variation of abiotic CO2 efflux from land to atmosphere at field scales. By identifying the major controls (including irrigation intensity and chemistry, soil texture, and type of crops), expected datasets from this field-based study can be extrapolated to large regional scales and provide the first essential assessment on the potential of irrigated agriculture to modify the land-atmosphere carbon exchange.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.