Effects of dredging an agricultural drainage ditch on water column herbicide concentration, as predicted by fluvarium
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In the study reported in this paper, sediments were collected from ditches draining agricultural, forested, and mixed agriculture and forest areas to determine which sediment properties influenced the release and uptake of P using an indoor stream channel fluvarium.
For the release phase, two replicates of each sediment were placed into two troughs of the fluvarium to a depth of approximately 5 cm (2 in), and the troughs were set at an angle of 5% (estimated mean slope of the three sampled sites).
1] total P (TP), was introduced into the fluvarium reservoir.
The quasi-equilibrium DRP concentration of fluvarium water was related to the mean [EPC.
Pre-dredge and dredged bed materials were placed in separate troughs of a fluvarium, built based on the fluvarium described by McDowell and Sharpley (2003).
Sediments were placed in the fluvarium troughs, and contaminated water was used for 120 hours, removed, and then was replaced with contaminant-free water for 24 hours.
The nutrient concentrations were regressed against the estimated distance the fluvarium water had been conveyed at the sampling times for the initial and final 24 h periods of the adsorption studies.
Ditch bed material was collected from the 0 to 5 cm (0 to 2 in) depth, immediately before dredging (hereafter referred to as pre-dredge) and immediately after dredging (hereafter referred to as dredged) for fluvarium experimental procedures described by Smith and Pappas (2007).
For the first set of experiments, hereafter referred to as "herbicide-spiked" experiments, fluvarium water was spiked to initial concentrations of 30 [micro]g [L.
All data represent the average of two fluvarium runs as in experiments by Smith et al.