Phosphate mineral accumulation in lake sediment to form a secondary phosphate source: A case study in lake sediment around Eppawala Phosphate Deposit (EPD) in Sri Lanka

Abstract

Global phosphorus scarcity will result in significant consequences for future food security with the depletion of current phosphate reserves. Therefore, exploration of new phosphorus sources is essential to address future phosphorus scarcity. The current study investigated the geochemical potential of lake sediment around the Eppawala Phosphate Deposit (EPD) in Sri Lanka to be used as a low-grade phosphorus source for agricultural purposes. Jaya-Ganga is a man-made water canal that drains through the EPD feeding three lakes, namely, upstream Ihalahalmilla Lake and Koon Lake, and downstream Kiralogama Lake with respect to the EPD. Three cores (cores A, B, and C) were collected from the above three lakes and major oxides and minerals distributions along the cores were analyzed. Notable high enrichment of phosphorus pentoxide (P2O5) content and high P2O5 solubility values were measured in the top 60 cm sediment layer in Core B and throughout the Core C compared to the Core A. This high enrichment of P2O5 content in the same sediment columns were confirmed by the comparison with the Upper Continental Crust (UCC) values and literature survey. According to the X-ray Diffraction (XRD) results, phosphate minerals, such as fluorapatite, crandallite, and millisite were abundantly found in the same sediment columns. Therefore, these phosphate minerals can be considered as pathfinding minerals for soluble phosphates in sediment cores. Thus, sediment with high P2O5 content and high solubility in downstream Kiralogama Lake showed the potential for application of these sediments as a direct phosphate source in agricultural purposes. Furthermore, the current study has introduced a new area of interest, i.e., soil and sediments around major phosphate deposits, for the exploration of new phosphate sources to meet future phosphorus demand.