Development of diffusive gradient in thin film as a new method for prediction of phosphate release from marine sediment

The diffusive gradient in the thin-film (DGT) technique can be used to predict phosphate release from sediment. The phosphate concentration was determined from the dissolved phosphate in the overlying water. The phosphate in overlying water diffused and accumulated in the DGT device. The study of phosphate released from sediment including the effect of temperature, pH, agitation, and phosphate concentration in the overlying water. The sediment was used in this experiment collected from the marine sediment of Jakarta Bay with speciation of phosphate in sediment as water-soluble P (H₂O-P), loosely bound-P (NH₄Cl-P), exchangeable fraction-P (NaHCO₃-P), P bound to iron (NaOH-P), and P bound to calcium (HCl-P). The fraction of H₂O -P, NH₄Cl-P, NaHCO3-P, HCl-P, and NaOHP was 0.16, 0.60, 2.68, 19.23, 1.63, and 0.20 μg/g, respectively. The maximum temperature of phosphate released at 35oC with the concentration of phosphate was 99.88 μg/L, the phosphate accumulation in the DGT device was 8.2569 μg and CDGT was 131.21 μg/L. The range of pH 5-10 resulted in the phosphate released was 59.33-100.16 μg/L, MDGT range 1.8331-2.9734 μg and C DGT range 13.21-22.82 μg/L. The agitation did not influence the phosphate released from the sediment. The phosphate accumulated in the DGT unit for deployment in the overlying water indicated the phosphate release from the sediment. It shows the ability of the DGT unit to absorb phosphate released from sediment to water. It can be inferred from this study that the DGT unit can predict phosphate release from the sediment based on the increase of phosphate accumulation in the DGT unit.