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Uptake and Release of Phosphorus from Overland Flow in a Stream Environment
Author(s) -
McDowell R. W.,
Sharpley A. N.
Publication year - 2003
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2003.9370
Subject(s) - eutrophication , phosphorus , sediment , environmental chemistry , surface runoff , soil water , sorption , hydrology (agriculture) , manure , benthic zone , nutrient , chemistry , environmental science , agronomy , soil science , ecology , geology , adsorption , biology , paleontology , geotechnical engineering , organic chemistry
Phosphorus runoff from agricultural fields has been linked to freshwater eutrophication. However, edge‐of‐field P losses can be modified by benthic sediments during stream flow by physiochemical processes associated with Al, Fe, and Ca, and by biological assimilation. We investigated fluvial P when exposed to stream‐bed sediments (top 3 cm) collected from seven sites representing forested and agricultural areas (pasture and cultivated), in a mixed‐land‐use watershed. Sediment was placed in a 10‐m‐long, 0.2‐m‐wide fluvarium to a 3‐cm depth and water was recirculated over the sediment at 2 L s −1 and 5% slope. When overland flow (4 mg dissolved reactive phosphorus [DRP] and 9 mg total phosphorus [TP] L −1 ) from manured soils was first recirculated, P uptake was associated with Al and Fe hydrous oxides for sediments from forested areas (pH 5.2–5.4) and by Ca for sediments from agricultural areas (pH 6.5–7.2). A large increase (up to 200%) in readily available P NH 4 Cl fraction was noted. After 24 h, DRP concentration in channel flow was related to sediment solution P concentration at which no net sorption or desorption of P occurs (EPC 0 ) ( r 2 = 0.77), indicating quasi‐equilibrium. When fresh water (approximately 0.005 mg P L −1 ; mean base flow DRP at seven sites) was recirculated over the sediments for 24 h, P release kinetics followed an exponential function. Microbial biomass P accounted for 34 to 43% of sediment P uptake from manure‐rich overland flow. Although abiotic sediment processes played a dominant role in determining P uptake, biotic process are clearly important and both should be considered along with the location and management of landscape inputs for remedial strategies to be effective.