『(Abstract)
Sediments can be both a source and a sink of dissolved phosphorus
(P) in surface water and shallow groundwater. Using laboratory
mesocosms, we studied the influence of flooding with deionized
water and simulated river water on P release to solution using
sediment columns taken from a riparian wetland. The mesocosm incubation
results showed that rather than retaining nutrients, sediments
in the riparian zone may be a significant source of P. Concentrations
of dissolved P in porewater reached more than 3 mg L-1
and in surface water over 0.8 mg L-1 within a month
of sediment inundation. The reductive dissolution of P-bearing
iron (Fe ) oxides was the likely mechanism responsible for P release.
Dissolved P to Fe molar ratios in anaerobic samples were approximately
0.45 when columns were flooded with water that simulated the chemistry
of the adjacent river. This suggests there was insufficient Fe
in the anaerobic samples to precipitate all P if the solutions
were oxygenated or transported to an aerobic environment. If the
anaerobic wetland solutions were delivered to oxygenated rivers
and streams adjacent to the riparian zone, the equilibrium concentration
of P in these systems could rise. The limiting of P release was
inversely related to the nitrate (NO3-)
concentration in floodwater. This indicates that in riparian zones
receiving low nitrate loads, or where NO3-
loads are being progressively reduced, the risk of dissolved P
release may increase. These findings present particular challenges
for restoration and management in riparian areas.』
Abbreviations
(Introduction)
Materials and methods
Mesocosm collection and pretreatment
Flooding of cores and water sample collection
Porewater and surface water analysis
Sediment-bound phosphorus
Data analysis
Results
Sediment-bound phosphorus fractionation under drained conditions
and the release of phosphorus after flooding
Changes in sediment-bound phosphorus during flooding
Release of solutes other than molybdate reactive phosphorus
Discussion
Release of phosphorus and potential for changes in phosphorus
concentration in aerobic receiving waters
Factors controlling phosphorus release during the incubations
Nitrate as a redox buffer delaying phosphorus release
Conclusions
Acknowledgments
References
※堆積物のリン分別法は、有機土壌に対するReddy et al.（1998）による方法を用いた。