『Abstract
Northwest Arkansas, similar to many regions around the world,
is home to intensive poultry production, which concentrates large
amounts of nutrients in localized areas. Concerns over phosphorus
(P) continue in these regions despite extensive conservation management
efforts. Part of the concerns relates to the legacy effect of
P in streams and the role of fluvial sediments in confounding
land conservation measures. Sediment substrate was collected from
five streams containing a variety of land uses in the Upper Illinois
River Watershed (UIRW) to assess the buffering capacity of sediments
on water column P. A purpose built fluvarium was used to determine
sediment-P relationships during three flow phases: (I) baseflow
(<0.005 mgPL-1), (II) uptake-enriched (1.8 mgPL-1),
and (III) re-equilibration (<0.005 mgPL-1) where water
was circulated over the sediment for 48 h at 0.001 m3s-1
(1 Ls-1). During each phase, flow was monitored and
water sampled for determination of dissolved reactive P (DRP).
In phase 1, DRP reached equilibrium concentrations, which closely
mimicked stream DRP at the time of sediment collection (R2
= 0.77), and the highest concentration measured was 0.080 mgPL-1
and the lowest 0.016 mgPL-1. Sediments rapidly bound
P (40% within 1 h) during phase II. During phase II, 84 to 96
% of added P was removed from solution. Of this bound P, 1 to
7 % was released during phase III. Results indicate that fluvial
sediments in the UIRW act as transient storage sites for P during
high P events. Finally, streams that bound the most P during nutrient-rich
flow released the least when returned to low P flow, indicating
a greater ability to buffer P in streams.
Keywords: Phosphorus; Streams; Nutrient management; Runoff』
1. Introduction
2. Methods
2.1. Study sites
2.2. Sediment and water sampling
2.3. Fluvarium operation
2.3.1. Phase I - “Baseflow”
2.3.2. Phase II - “P-Enriched uptake”
2.3.3. Phase III - “Re-equilibration”
2.4. Sediment and water analysis
2.5. Statistical analysis
3. Results and discussion
3.1. Stream sediment properties
3.2. Fluvarium
3.2.1. Phase I
3.2.2. Phase II
3.2.3. Phase III
4. Conclusions
Acknowledgments
References