SM “Five-step extraction method for P in sediments”
The middle layer (-3~-5 cm) of the fresh wet sediment was used for P fractionation/TP analyses according to references (Psenneret al., 1988; Hieltjes and Lijklema, 1990).The sediment samples were transferred to the freeze drier machine for lyophilization. Thereafter, they were homogenized through grinding and finally passed through a 63 μm-sieve and preserved. Sediment was sequentially extracted and five fractions were obtained. For each fraction, phosphorus was determinedusing the molybdenum blue/ascorbic acid method(APHA, AWWA, WEF, 1995).
Total phosphorus (TP) in sediments was determined usingthe molybdenum-blue-colorimetric method after pre-treating the powderedsample with K2S2O8 and digesting the mixture in an autoclave at 120°C, for 30 min (Murphy and Riley, 1962; Nelson, 1987).TP and P fractionation in nine sediment samples are listed in Table 2. TP, P fraction and labile P pool in sediments (NH4Cl–P+BD–P) are indicated in Fig. S4. The analytical quality control (QC) is listed inTable S3.
Five P fractions: (1) NH4Cl–P (Loosely bound or sorbed P); (2) BD–P (reducible metal hydroxides andassociated P, primarily Fe–P); (3) NaOH25°C–P(organic material, Al(OH)3and associated P, primarily Al-P); (4)HCl–P (Soluble reactive P associated with any calcite and apatite, primarilyCa–P); (5) NaOH85°C–P (Residual-P).
References
Psenner, R. and Pucsko, R., 1988. Phosphorus fractionation: advantages andlimits of the method for the study of sediment P origins andinteractions, Arch Hydrobiol Beih Ergebn Limnol30, 43–59.
Hieltjes, A.H.M. and Lijklema, L., 1980. Fractionation of inorganic phosphates incalcareous sediments, J Environ Qual 9, 405–407.
APHA, AWWA, WEF, 1995. Standard methods for theexamination of water and wastewater, 19th edn.America Public Health Association, American WaterWorks Association, Water and Environment Federation,Washington DC, USA.
Murphy, J. and Riley, J.P., 1962. A modified single solution methodfor the determination of phosphate in natural waters, Anal. Chim. Acta 27, 31–36.
Nelson, N.S., 1987. An acid-persulfate digestion procedure fordetermination of phosphorus in sediments, Commun SoilSci Plant Anal 18(4), 359–369.