『Abstract
Phosphorus (P) is often a key limiting nutrient in freshwater
systems, and excessive P can result in algal blooms, with flow-on
effects to aquatic food webs. P sorption is an important process
in aquatic and terrestrial ecosystems whereby phosphate (PO43-) is exchanged between liquid and
solid phases. This study shows that differences in the concentration
of PO43- in a subtropical river
system during high and low flow can be attributed to differences
in P sorption characterises of its catchment soils and sediments.
The sediments have lower Equilibrium Phosphate Concentrations
(EPCo) and higher binding energy (Kd); the surface soils have higher EPCo
and higher easily desorbed P (NH4Cl-P). A
comparison of filterable reactive phosphorus (frP) in water samples
collected at high and low flows, with soil and sediment EPCo, suggested that during event flows, the high
EPCo and NH4Cl-P of
surface soils is producing a net movement of PO43-
from the soil/sediment system into runoff and stream flow. At
baseflow, there is more likely a net movement of PO43-
into the riverbed sediments. This has important implications for
management actions aimed at reducing P loads to river systems
and downstream water storages, namely the need to increase the
infiltration of rainfall to decrease the amount of PO43-
being flushed from the surface soil.
Keywords: Equilibrium phosphate concentration; Phosphorus; Rivers;
Sediment; Soil』
Introduction
Methods
Study area
Study sites and sampling
Sediment characteristics
Sequential extraction
Phosphorus sorption
Statistical analysis
Results
Phosphorus fractionation of sediments and soils
Phosphorus sorption in sediment and soil
Comparison of the EPCo of soils and sediments
with water column frP under event flow and baseflow conditions
Comparison of NH4Cl-P pools, P sorption
capacity and annual frP loads in the UBR catchment
Discussion
Conclusion
Acknowledgments
References