Collaborative Research: From Global to Local: Geochemistry of Global Phosphate Ores and Implications for Tracing the Environmental Impacts of Fertilizers Utilization

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Phosphorus (P) is one of the primary macronutrients essential for plant growth and crop production, and thus its availability is important for sustainable agriculture development and food security. Approximately 47 million tons of P-fertilizers are annually generated from phosphate rocks and applied worldwide. Intensification of P-fertilizer utilization over the last few decades has caused widespread eutrophication and degradation of the quality of freshwater resources and coastal areas. Yet elevated levels of metals in phosphate rocks and P-fertilizers such as cadmium, chromium, and uranium pose less recognized but significant potential risks to soil and water quality. Although pollution of soils and water from P-fertilizer applications has been documented in a few case studies, no systematic evaluation on the occurrence of metals in global phosphate ores and the ability to detect their impact in the environment have been conducted. The results of this study will have important and critical information on levels of metals in global phosphate rocks as well as in various fertilizers utilized in the U.S., the long-term impact on soil and water quality in agricultural areas, and the possible risks for rural communities in areas of extensive P-fertilizers utilization.The project will characterize the geochemistry of global phosphate ores and associated P-fertilizers, as well assess the environmental impact of the metals they contain. The project is based on developing novel geochemical methods for tracing the origin of the phosphate rocks and the impact of P-fertilizers in the environment. The objectives of the study are to: (1) generate a systematic chemical dataset of major global phosphate ores, including major and trace elements, rare-earth elements, strontium and lead isotopes, and radionuclides (uranium, radium) for evaluating the origin of the phosphate ores (geological setting, age, diagenetic modification), and the relationships between the geological settings and the occurrence of metals in global phosphate ores; (2) evaluate the differential incorporation of metals from dissolution of phosphate rocks in P-fertilizers and waste byproducts (gypsum); (3) evaluate the potential of using the geochemical and isotope variations as tracers to delineate the impact of P-fertilizers in the environment; and (4) evaluate the environmental impact of P-fertilizers application through laboratory experiments and a field-scale investigation in an agricultural research station in North Carolina, where different rates of P-fertilizers have been applied for several decades. The field study will include systematic monitoring of soils, plants, unsaturated zone, agriculture runoff, shallow groundwater underlying experimental agriculture fields, and regional groundwater in vicinity of extensive agricultural activities.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.