『Abstract
The role of sediment-bound or particulate P in agricultural runoff
in accelerating the biological productivity of surface water can
be assessed if the biological availability of particulate P (PP)
is known. Previous research has indicated amounts of P extracted
from deposited river and lake sediments by 0.1 M NaOH to be correlated
with P uptake by the alga Selenastrum capricornutum. This
study investigates a modification of this extraction to allow
routine quantification of potentially bioavailable particulate
P (BPP) content of agricultural runoff from the Reddish Prairies
and Rolling Red Plains land resource areas. In the proposed method,
20 mL of unfiltered runoff is shaken with 180 mL of 0.11 M NaOH
for 17 h and BPP concentration calculated by substruction of the
soluble P (SP) concentration of the runoff sample. Total bioavailable
P concentration (TBP) of runoff can be represented by BPP plus
SP concentration. Growth of P-starved S. capricornutum,
incubated for up to 29 d with runoff sediment from nine watersheds,
as the sole P source, was correlated (r2 = 0.76 to
0.95) with potentially BPP content of the added sediment. Sample
dilution had no effect on the amount of P extracted from runoff
sediment by NaOH across a range in sediment concentration of the
extraction medium, equivalent to that observed for 95% of the
runoff events. If the sediment concentration of runoff exceeds
20 g L-1, a smaller runoff sample is used in the extraction.
The results indicate the applicability of the proposed extraction
method to quantify the bioavailability of P transported in agricultural
runoff.
(Introduction)
Materials and methods
Runoff collection
Analysis
Algal assay
Proposed method
Results and discussion
Acknowledgments
References