Hou,L.J., Liu,M., Yang,Y., Ou,D.N., Lin,X., Chen,H. and Xu,S.Y.(2009): Phosphorus speciation and availability in intertidal sediments of the Yangtze Estuary, China. Applied Geochemistry, 24, 120-128.


 In order to better understand P cycling and bioavailability in the intertidal system of the Yangtze Estuary, both surface (0-5 cm) and core (30 cm long) sediments were collected and sequentially extracted to analyze the solid-phase reservoirs of sedimentary P: loosely sorbed P; Fe-bound P; authigenic P; detrital P; and organic P. The total sedimentary P in surface and core sediments ranged from 14.58-36.81μmol g-1and 17.11-24.55μmol g-1, respectively, and was dominated by inorganic P. The average percentage of each fraction of P in surface sediments followed the sequence: detrital P (54.9%)>Fe-bound P (23.7%)>organic P (14.3%)>authigenic P (6.3%)>loosely sorbed P (0.8%), whereas in core sediments it followed the sequence: detrital P (61.7%)>Fe-bound P (17.0%)>authigenic P (13.1%)>organic P (7.5%)>loosely sorbed P (0.7%). Post-depositional reorganization of P was observed in both surface and core sediments, converting organic P and Fe-bound P to authigenic P. The accumulation rates and burial efficiencies of the total P in the intertidal area ranged from 118.70-904.98μmol cm-2 a-1 and 80.29-88.11%, respectively. High burial efficiency of the total P is likely related to the high percentage of detrital P and the high sediment accumulation rate. In addition, the bioavailable P represented a significant proportion of the sedimentary P pool, which on average accounted for 37.4% and 25.1% of the total P in surface and core sediments, respectively. This result indicates that the tidal sediment is a potential internal source of P for this P-limiting estuarine ecosystem.』

1. Introduction
2. Materials and methods
 2.1. Study area
 2.2. Sample collection and pretreatment
 2.3. Sequential extraction of phosphorus
 2.4. Analytical methods
 2.5. Data analysis
3. Results
 3.1. Sediment characteristics
 3.2. Phosphorus fractions in sediments
4. Data analysis and interpretation
 4.1. Phosphorus speciation in surface sediments
 4.2. Phosphorus speciation in core sediments
 4.3. Factor analysis
 4.4. Sedimentation and burial of phosphorus
 4.5. Bioavailable phosphorus
5. Summary and conclusions

Table 1 SEDEX technique with reaction mechanisms (Ruttenberg, 1992)
Step Extractant Phase extracted Reaction
I 1 M MgCl2 (pH 8) Exchangeable or loosely sorbed P Formation of MgPO4-1 complex and (or) mass action displacement by Cl-1
II 0.30 M Na3-citrate 1.0 M NaHCO3 (pH 7.6) 1.125 g Na-dithionite in 45 ml of citrate bicarbonate Easily reducible or reactive ferric Fe-bound Reduction of Fe3+ by dithionite and subsequent chelation by citrate
III 1 M Na-acetate buffered to pH 4 with acetic acid Authigenic P (CFAP + biogenic hydroxyapatite + CaCO3-bound) Acid dissolution at moderately low pH and (or) chelation of Ca2+ by acetate
IV 1 M HCl Detrital P (FAP) Acid dissolution
V Ash at 550℃ 1 M HCl Organic P Dry oxidation at 550℃ 1 M HCl extraction of ashed residue

堆積物表面:(IV)砕屑P (54.9%)>(II)鉄に結合したP (23.7%)>(V)有機P (14.3%)>(III)自生P (6.3%)>(I)吸着P (0.8%)
堆積物コア試料:砕屑P (61.7%)>鉄に結合したP (17.0%)>自生P (13.1%)>有機P (7.5%)>l吸着P (0.7%).