『Abstract
Suspended particulate matter (SPM) collected in the Changjiang
(Yangtze River) estuary in June 2006 was separated into five fractions
via water elutriation: clay-very fine silt (＜8μm), fine silt (8-16μm),
medium silt (16-32μm), coarse silt (32-63μm) and sand (＞63μm).
The SPM and fractionated particles were sequentially analyzed
by a modified SEDEX sequential extraction method to obtain six
species of phosphorus: exchangeable or loosely-sorbed P, organic
P, Fe-bound P, authigenic P, detrital P and refractory P. The
results indicated that all particulate phosphorus species except
for detrital P were negatively correlated to particle size; a
high detrital P content was found in coarse silt and very coarse
silt. From the inside of the river mouth to the gate of the river
mouth, organic P, Fe-bound P and refractory P in the suspended
particles decreased and a higher amount of exchangeable P appeared
around the gate of the river mouth. From the gate of the river
mouth to the sea, exchangeable P and organic P in suspended particles
increased distinctly. The total particulate P flux in to the estuary
from the Changjiang River was about 45.45×108μmol/s
during sampling. Of this, about 8.27×108μmol/s was
associated with the “truly suspended” fraction. The bio-available
particulate P flux was about 13.58×108μmol/s. Of this,
about 4.24×108μmol/s was transported by “truly suspended”
particles.
Keywords: Changjiang estuary; particle size fractions; particulate
phosphorus species』
1. Introduction
2. Study areas
3. Materials and methods
3.1. Sampling
3.2. SPM, Chl-a, DIP and DOP
3.3. Particle size fractions
3.4. Sequential extraction of particulate P
4. Results
4.1. Salinity, SPM, Chl-a and suspended particle size distribution
4.2. Dissolved phosphorus
4.3. Particulate P species in suspended particles
4.4. Particulate P species in various particle size classes
5. Discussion
5.1. Effect of particle size on particulate P species
5.2. Behavior of particulate P in the Changjiang estuary
5.3. Riverine fluxes of particulate P to the Changjiang estuary
6. Conclusion
References