SM “The procedure for physicochemical parameters in sediment and water and for DIFS simulation”

(1)The sediment samples were digested with HNO3–HF–HClO4 and

concentrations of Al, Fe and Ca in the extracts were measured using HR-ICP-MS (high-resolution inductively coupled plasma mass spectrometry) (Lin et al., 2008). Total organic content (TOC) was determined using potassium bichromate-dilution heat colorimetric method (Bao, 1999). ORION STAR instrument (Thermo Electron Corporation, USA) was operated for the determination of Eh and pH (Ave.±SD) in the surface sediments/water. Conductivity and dissolved oxygen in water were determined using the electrode probe (sensION 156, Hach, USA). SRP (Soluble reactive P) in water was determined according to the method in reference (Li et al., 2010).

(2)Physicochemical parameters for sediments and P-DIFS were also

determined and calculated by the methods recommended in references (Ernstberger et al., 2002; Monbet et al., 2008). Particle density (Pc), sediment porosity (s) and effective diffusion coefficient in the sediment (Ds) are listed in Table 1-1. Co-labile P (soluble reactive P) in porewater in sediment zone of DGT deployment (at depths between -3 and -5 cm) was determined by the centrifugation (Hamilton-Taylor and Morris, 1985) and molybdenum blue methods (SEPA, 2002). This procedure for labile P in sediment porewater was conducted in a specially designed glove box purged with nitrogen (O2 concentration 1%) at all times during the process. Pc and s were measured and calculated according to the recommended method (Ernstberger et al., 2002). Effective diffusion coefficient in the sedimentporewater (Ds) can be calculated using the SM Eq (2) (Ernstberger et al., 2002). Ds is indicated in Table 1-1.

Reference in SM

Bao,S.D., 1999. Measurement of organic matter content in soil. In: S.D.Bao, R.F.Jiang, C.G.Yang (Eds.), Analysis of agri-chemistry in soil, 3rd edn. Chinese Agricultural Science and Technology Press, Beijing, pp 34–35.

Ernstberger, H., Davison, W., Zhang, H.,Tye, A., Young, S., 2002. Measurement and dynamic modelling of trace metal mobilization in soils using DGT and DIFS, Environ. Sci. Technol. 36, 349-354.

Hamilton-Taylor, Morris, J., E. B.,1985. The dynamics of iron and manganese in surface sediments of a seasonally anoxic lake, Archiv Für Hydrobiologie-Supplement 72, 135-165.

Li, Y. Z., Xia, B.C., Zhang, J.Y., Li, C.H., Zhu, W. Z., 2010. Assessing high resolution oxidation-reduction potential and soluble reactive phosphorus variation across vertical sediments and water layers in Xinghu Lake: A novel laboratory approach,J. Environ. Sci. 22, 982–990.

Lin, J., Liu, C.Q., Zhu, Z.Z., 2008. Historical eutrophication in Lake Taihu: evidence from biogenic silica and total phosphorus accumulation in sediments from northern part of Lake Taihu, Environ. Geol.55, 1493–1500.

Monbet, P., Mckelvie, I., Worsfold, D., P. J., 2008. Combined gel probes for the in situ determination of dissolved reactive phosphorus in porewaters and characterization of sediment reactivity, Environ. Sci. Technol.42, 5112–5117.

SEPA (State Environmental Protection Administration ofChina), 2002.Monitor and analysis method of waterand wastewater, Chinese EnvironmentalScience, Beijing.