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Analysis of Loss of Ignition of Root Zone of Bioretention Units at the Edison Environmental Center
Citation:
OConnor, T. Analysis of Loss of Ignition of Root Zone of Bioretention Units at the Edison Environmental Center. In Proceedings, EWRI World Environmental & Water Resources Congress 2018 in Minneapolis, Minnesota, Minneapolis, Minnesota, June 03 - 07, 2018. Environmental & Water Resources Institute (EWRI) of ASCE, Reston, VA, 207-214, (2018).
Impact/Purpose:
This proceedings paper is for a presentation on sampling and analysis in bioretention units at the Edison Environmental Center. It addresses design considerations of green infrastructure.
Description:
Six bioretention units (widths 7.1 m) at USEPA’s Edison Environmental Center were constructed to evaluate sizing of surface area to watershed area. Three sizes were tested in duplicate with changes in aspect ratio of length from inlet (northern) wall by doubling successive length from smallest (3.7 m) to largest (14.9 m). Each is instrumented for continuous monitoring with water content reflectometers (WCR) and thermistors with monitoring data since November 2009. In late 2012, a survey of shrubs planted in these bioretention units was performed. The combined analyses of moisture content and plant size indicated the smallest units had superior shrub growth due to the more frequent saturation of the root zone as measured by WCR. In 2017, sediment samples for loss on ignition (LOI) analysis were collected to determine available carbon in the near surface root zone as a secondary proxy for plant health. It was hypothesized that observations of LOI would support the 2012 survey conclusions of shrub sizes in these units. Samples were taken at a depth of 0.15 m and at 0.3 m intervals along the centerline and starting at the north wall of each bioretention unit. Initial results of three units indicate differences between the northern and southern section of individual units, as well as differences between three unit sizes. The largest LOI values were observed in the smallest unit indicating highest plant density. Although this observation seems to support the stated hypothesis, further sampling and analysis for all six bioretention units is planned.