Organic Acid Promoted Dissolution of Phosphate as Affected by its Solid State Speciation in Single and Mixed Fe, Al, Ca Mineral Systems: Implications for Phosphorus Bioavailability

有机酸促进磷酸盐溶解，受单一和混合 Fe、Al、Ca 矿物系统中固态形态的影响：对磷生物利用率的影响

• 批准号: 0819962
• 负责人: Nadia Adam
• 金额: $ 22.24万
• 依托单位: University of Wyoming
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-01 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0819962&HistoricalAwards=false
• 关键词: Organic; Acid; Promoted; Dissolution; Phosphate

Intellectual Merit: The current understanding of organic acid mediated phosphate dissolution is limited by the lack of a molecular scale characterization of its solid state speciation. Furthermore, phosphate dissolution has not been studied in context of its uptake without the complicating influence of metabolism as in microbial cells or plants. Our current knowledge can mainly be attributed to wet chemical studies in soils whose inherent complexity makes it difficult to characterize the effect of primary environmental variables (pH, concentration of phosphate, type of organic acid and its concentration). In addition, phosphate dissolution in binary and tertiary mixtures of iron, aluminum and Ca minerals (main sorbents of phosphate) that can serve as an effective analog for soils has not been investigated. Based on a molecular scale XANES based investigation of phosphate sorption in 1:1 (by mass) binary mixtures of Fe-oxide and Aloxide minerals or Ca containing minerals, we can now: 1) quantify the distribution of phosphate between individual mineral phases in binary and ternary mixtures (Khare et al., 2004; Beauchemin et al., 2003); 2) distinguish between adsorption and surface precipitation in single mineral and binary mixtures (Khare et al., 2005); and 3) determine phosphate bonding configuration and differentiate between surface complexes (Khare et al., 2007). Thus, we are now in a position to exploit these XANES based tools in uncovering molecular mechanisms of phosphate dissolution. This research will include a high affinity transporter for yeast cells reconstituted into proteoliposomes as a sink for dissolved phosphate to understand and realistically predict phosphate dissolution in natural systems.The proposed research will take place over two years and will address two main hypotheses:Hypothesis 1: Phosphate dissolution in single mineral, binary and tertiary mixtures is controlled by the solid state speciation (mode of phosphate bonding, adsorption vs. surface precipitation and the partitioning of phosphate in individual mineral phases), of phosphate in these minerals.Hypothesis 2: Phosphate uptake will be adversely affected by Al3+ in binary mixtures of Fe and Al containing minerals however in ternary mineral systems the presence of Ca2+ will ameliorate Al toxicity. Broader Impacts: Phosphorus is an essential plant macronutrient and also a potential water pollutant. Most terrestrial and marine ecosystems are P limited because phosphate minerals are sparingly soluble. Because organic acids citrate, malate released by plants roots or microbes are considered the main mode of P solubilisation in soils and other natural systems, this basic geochemical research is pertinent to improving soil fertility. This is particularly significant because food production needs to double in the next 20 years to sustain increasing world population. Characterizing organic acid mediated phosphate dissolution at the nano scale will also help with better predictions of phosphorus bioavailability and release. Recently phosphate release from heavily fertilized P enriched soils has degraded surface water quality, causing eutrophication. Furthermore, better estimates of phosphate bioavailability will help predict CO2 uptake rates critical to predicting global warming. This project will contribute to a graduate student's dissertation, to be supervised by the PI and co-PI jointly. An integrated wet chemical, spectroscopic (XANES), microscopic (TEM) and geochemical modeling approach will be used.

知识价值：目前对有机酸介导的磷酸盐溶解的理解受到缺乏其固态形态的分子尺度表征的限制。此外，磷酸盐溶解尚未在其摄取的背景下进行研究，而不像在微生物细胞或植物中那样受到代谢的复杂影响。我们目前的知识主要可以归功于土壤的湿化学研究，其固有的复杂性使得难以表征主要环境变量（pH值，磷酸盐浓度，有机酸类型及其浓度）的影响。此外，磷酸盐溶解在铁、铝和钙矿物（磷酸盐的主要吸附剂）的二元和三级混合物中，可以作为土壤的有效模拟物，但尚未进行研究。基于基于XANES的分子尺度对铁氧化物和氧氧化物矿物或含钙矿物1:1（质量）二元混合物中磷酸盐吸附的研究，我们现在可以：1)量化二元和三元混合物中单个矿物相之间磷酸盐的分布（Khare等人，2004；Beauchemin等人，2003）；2)区分单一矿物和二元混合物中的吸附和表面沉淀（Khare等，2005）；3)确定磷酸键构型并区分表面配合物（Khare et al., 2007）。因此，我们现在能够利用这些基于XANES的工具来揭示磷酸盐溶解的分子机制。这项研究将包括酵母细胞的高亲和力转运体重组为蛋白质脂质体，作为溶解磷酸盐的汇，以了解和现实地预测自然系统中磷酸盐的溶解。拟议的研究将在两年多的时间内进行，并将解决两个主要假设：假设1：磷酸盐在单一矿物，二元和三级混合物中的溶解受这些矿物中磷酸盐的固态形态（磷酸盐结合模式，吸附与表面沉淀以及磷酸盐在单个矿物相中的分配）的控制。假设2：在含铁和含铝矿物的二元混合物中，磷酸盐的摄取将受到Al3+的不利影响，然而在三元矿物系统中，Ca2+的存在将改善铝的毒性。广泛影响：磷是一种必需的植物常量营养素，也是一种潜在的水污染物。大多数陆地和海洋生态系统都是磷有限的，因为磷矿物很少可溶。植物根系或微生物释放的有机酸柠檬酸盐、苹果酸盐被认为是土壤和其他自然系统中磷溶解的主要方式，这一基础地球化学研究与提高土壤肥力有关。这一点尤其重要，因为粮食产量需要在未来20年翻一番，才能维持不断增长的世界人口。在纳米尺度上表征有机酸介导的磷酸盐溶解也将有助于更好地预测磷的生物利用度和释放。近年来，磷从富磷土壤中大量释放，使地表水水质恶化，造成富营养化。此外，更好地估计磷酸盐的生物利用度将有助于预测二氧化碳吸收率，这对预测全球变暖至关重要。该项目将作为研究生论文的一部分，由PI和co-PI共同指导。将使用综合湿化学、光谱（XANES）、微观（TEM）和地球化学建模方法。