Investigation of the fertilizing capacity of bottom sediments in the Anuradhapura region

Abstract

Abstract (150-300 words), covering: Para I - Introduction to and Significance of Research (50-100words), Para 2 - Objectives and Methodology (50-100 words), and Para 3 - Key results and conclusions (50-100 words) Jaya-Ganga is a water canal constructed bisecting the phosphate deposit in Eppawala, Sri Lanka. It nourishes three lakes around the vicinity of Eppawala Phosphate Deposit (EPD). With a view to prospect for unconventional phosphate sources, surface and core sediment samples from three lakes were evaluated, especially to determine the P2O5 concentrations and phosphate solubility. Additionally, surface sediments were analyzed by X-ray fluorescence, X-ray diffraction and laser particle analyzer to evaluate geochemical, mineralogical and textural variations, respectively. p20s% in the surface lake sediments varied from 0.12 to 1.91 and from 0.33 to 1.24 in upstream and downstream, respectively. In upstream core sediment samples, p20s% varied between 0.03 and 1.S9, however, in downstream core samples, P205% varied from 0.01 to 2.22. The solubility of phosphates in lake sediments is typically assessed with respect to 2% citric acid solubility (by P2O5). Aligning with aforesaid, the performed solubility analysis upstream showed 14% to 37% in surface samples and from 4% to 71% in core samples. The corresponding values for the downstream samples fluctuated from 8% to 58% and from 1% to 50%, respectively. Moreover, geochemical analyses of the surface sediments in both upstream and downstream lakes revealed higher contents of P2O5, TiO*, AhO.*, FcjOa and MnO and, low levels of SiO?, MgO, Na?0, K2O and CaO compared with the norms of Upper Continental Crust (UCC) values. The significantly positive anomaly of P2O5 in downstream sediments against UCC comparison is noteworthy.Mineralogical analyses revealed the presence of phosphate-bearing minerals such as fluorapatite, crandallite and millisite in downstream surface sediments, which are the weathered products of the EPD. Textural studies of surface sediments delineated the nature of material deposition through solid suspensions and favorable dcpositional condition, in downstream lake. Overall, results of the study reflected the contribution of the EPD as a phosphate source to the downstream lake and the potential of secondary phosphate mineralization in downstream sediments. High solubility values facilitated the applicability of downstream lake sediments as a low-grade phosphate additivc/fertilizer. Continuous nourishment of phosphate-bearing materials via Jaya-Ganga, into the downstream lake sediments, steadily increase the quantity of the phosphate content in downstream sediments and the minable quality of the lake sediments as an economically viable phosphate source in the future.