Abstract
Particle size is one factor affecting phosphorus (P) dynamics in soils and sediments. This study investigated how flow facilitated by hydraulic pumps and aquatic vegetation species water lettuce (Pistia stratiotes) and water hyacinth (Eichhornia crassipes) affected particle size and P-dynamics in organic sediments in agricultural drainage ditches. Sediments with finer particle size (>0.002 mm) were hypothesized to contain greater total P (TP) and less labile P than sediments with coarser particle size. Particle size was determined using a LS 13 320 Laser Diffraction Particle Size Analyzer. Sediments were tested for pH, TP, and organic matter. Fractions of P were determined using a sequential fractionation experiment and 31P Nuclear Magnetic Resonance (NMR) Spectroscopy. Larger average particle size and lower average total P concentrations were found in the inflows of the field ditches compared to the outflows. Presence of flow and aquatic vegetation did not have a significant impact on particle size, TP, or labile P fractions. Median (p = 0.10) particle size was not significantly correlated to TP. Overall, there was an average trend of coarser particle size and lower P concentrations in the inflow compared to the outflow. The presence of inorganic limerock could have affected results due to increased P adsorption capacity and larger average particle size compared to the organic fraction of the sediment.
Highlights
Phosphorus (P) from non-point sources such as agriculture increase eutrophication, potentially causing algal blooms, fish kills, and subsequent environmental and economic harm [1]
This study investigated how flow, facilitated by hydraulic pumps, and the introduction of floating aquatic vegetation affected sediment texture and P dynamics in agricultural drainage ditches in the Everglades Agricultural Area (EAA)
Lower P concentrations were found in the inflow compared to the outflow, and larger particle size in the inflow compared to the outflow
Summary
Phosphorus (P) from non-point sources such as agriculture increase eutrophication, potentially causing algal blooms, fish kills, and subsequent environmental and economic harm [1]. The Everglades Agricultural Area (EAA) sits upstream from the Florida Everglades, a traditionally P limited environment. Additions of P to the Everglades have been found to cause eutrophication and changes in vegetation communities, such as when the naturally dominant sawgrass (Cladium jamaicense) is replaced by cattail (Typha) [2,3]. Phosphorus-dynamics and particle size in agricultural sediments and analysis, decision to publish, or preparation of the manuscript
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