TY - JOUR
T1 - Phosphorus speciation in stream bed sediments from an agricultural watershed
T2 - Solid-phase associations and sorption behavior
AU - Machesky, Michael L.
AU - Holm, Thomas R.
AU - Slowikowski, James A.
N1 - Funding Information:
Acknowledgments Project funding was provided by the Illinois Council of Food and Agricultural Research (CFAR) and the Illinois Environmental Protection Agency. Joshua Stevens, Kip Stevenson and Ted Snider aided in the collection of sediment and water samples. ICP analyses were performed by Kaye Suratt at the Illinois State Water Survey, XRD at the State Geological Survey, and N2-BET analyses at the University of Illinois Materials Characterization Laboratory. Walt Kelly and George Roadcap of the State Water Survey provided valuable comments on an earlier draft of this manuscript. Also, the comments of two anonymous reviewers resulted in a much improved final manuscript.
PY - 2010
Y1 - 2010
N2 - The sorption behavior and solid-phase associations of phosphorus (P) in fine-grained sediments (<63 μm) from two upstream tributaries and one downstream main stem site of the Spoon River in west-central Illinois were characterized to better understand phosphorus bioavailability in this agriculturally dominated watershed. The P sorption affinities, as indicated by linear distribution coefficients (Kd), of all sediments were 330-5,150 L/kg, and negatively correlated with equilibrium phosphorus concentration (EPCo) values, which ranged between 0.2 and 2.2 μM. pH values measured at the conclusion of the sorption experiments varied only slightly (7.45-8.10) but were nonetheless strongly positively correlated to EPCo values, and negatively correlated to Kd values, suggesting the importance of pH to the observed sorption behavior. Kd values were generally lower and EPCo values higher at the main stem site than at the upstream tributary sites, suggesting dissolved reactive P (DRP) bioavailability (specifically orthophosphate) increased downstream. The solid phase associations of P were operationally assessed with the streamlined SEDEX (sedimentary extraction) procedure, and most sediment P (≥50%) was released during the step designed to determine iron oxide-associated P. On average, 70-90% of the total sediment P pool was potentially bioavailable, as estimated by the sum of the iron oxide-, authigenic carbonate-, and organic-associated P fractions. Considerable calcium was also extracted from some sediments during the step designed to specifically remove iron oxide-associated P. It is hypothesized that the severe drought conditions that persisted between April and October, 2005 allowed authigenic carbonates (perhaps partly amorphous) to accumulate, and that these carbonates dissolved during the iron oxide extraction step. The extensive benthic algal populations also present may have aided carbonate precipitation, which under more normal hydrologic conditions would be periodically flushed downstream and replaced by fresh sediment. This suggests antecedent hydrologic conditions played a dominant role in the P sorption and solid phase associations identified.
AB - The sorption behavior and solid-phase associations of phosphorus (P) in fine-grained sediments (<63 μm) from two upstream tributaries and one downstream main stem site of the Spoon River in west-central Illinois were characterized to better understand phosphorus bioavailability in this agriculturally dominated watershed. The P sorption affinities, as indicated by linear distribution coefficients (Kd), of all sediments were 330-5,150 L/kg, and negatively correlated with equilibrium phosphorus concentration (EPCo) values, which ranged between 0.2 and 2.2 μM. pH values measured at the conclusion of the sorption experiments varied only slightly (7.45-8.10) but were nonetheless strongly positively correlated to EPCo values, and negatively correlated to Kd values, suggesting the importance of pH to the observed sorption behavior. Kd values were generally lower and EPCo values higher at the main stem site than at the upstream tributary sites, suggesting dissolved reactive P (DRP) bioavailability (specifically orthophosphate) increased downstream. The solid phase associations of P were operationally assessed with the streamlined SEDEX (sedimentary extraction) procedure, and most sediment P (≥50%) was released during the step designed to determine iron oxide-associated P. On average, 70-90% of the total sediment P pool was potentially bioavailable, as estimated by the sum of the iron oxide-, authigenic carbonate-, and organic-associated P fractions. Considerable calcium was also extracted from some sediments during the step designed to specifically remove iron oxide-associated P. It is hypothesized that the severe drought conditions that persisted between April and October, 2005 allowed authigenic carbonates (perhaps partly amorphous) to accumulate, and that these carbonates dissolved during the iron oxide extraction step. The extensive benthic algal populations also present may have aided carbonate precipitation, which under more normal hydrologic conditions would be periodically flushed downstream and replaced by fresh sediment. This suggests antecedent hydrologic conditions played a dominant role in the P sorption and solid phase associations identified.
KW - Equilibrium phosphorus concentration
KW - Phosphorus
KW - Sequential extraction
KW - Sorption
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U2 - 10.1007/s10498-010-9103-2
DO - 10.1007/s10498-010-9103-2
M3 - Article
AN - SCOPUS:77954219133
SN - 1380-6165
VL - 16
SP - 639
EP - 662
JO - Aquatic Geochemistry
JF - Aquatic Geochemistry
IS - 4
ER -