Biological Nitrate Removal With Emerald Ash Borer-Killed Ash and High-Tannin Oak Woodchips

Abstract

Two common tree species, ash (Fraxinus sp.) and oak (Quercus sp.), could provide readily available media for denitrifying bioreactors that use wood-based carbon for biological nitrate treatment. However, it is not known if the wood from Emerald Ash Borer-killed (EAB-killed) ash trees is an effective carbon source for nitrate removal compared to other wood species or if the high-tannin nature of oak inhibits denitrification potential. This lab-scale study showed that EAB-killed ash woodchips did not significantly differ in nitrate removal or denitrification potential compared to a commercially available blend of hardwood chips. However, neither treatment performed as well as oak woodchips in these metrics. Use of high-tannin oak in bioreactors is currently restricted by a federal standard in the United States. Ash woodchips beneficially exhibited the lowest nitrous oxide production potential, and their dissolved phosphorus leaching fell within the range of other woodchip types. Emerald ash borer-killed ash wood could be an effective source for denitrifying bioreactors located within affected regions and oak woodchips merit additional investigation for the application of denitrifying bioreactors.

Nitrate Removal and Woodchip Properties across a Paired Denitrifying Bioreactor Treating Centralized Agricultural Ditch Flows

“…Denitrification potential of the in-ditch woodchips (2950 ± 580 ng N g −1 dry media h −1 ) was significantly higher than all other sediment or woodchip samples, including the diversion bioreactor woodchips (620 ± 310 ng N g −1 dry media h −1 , Figure 4). Values were within the range reported in the literature (100-11,000 ng N g −1 h −1 ) [20,30,31]. The inditch woodchip's high potential to provide denitrification was consistent with low nitrate observed within the pore water (Supplemental Figure S6).…”

“…Woodchips from each of the four diversion bioreactor sampling ports were similarly aggregated into one sample. The assays were conducted using methods previously described for woodchip [20] and soil samples [21]. Briefly, in each 150 mL assay jar, a 15-25 g woodchip or soil sample was treated with 25 mL of nutrient solution.…”

Structure and diversity in a periurban forest of Bucharest, Romania

“…Tree species can absorb these pollutants differently (Han et al 2022). For example, oaks and maples are efficient in removing nitrogen oxides (Wickramarathne et al 2021), while pines and other conifers are efficient in absorbing sulfur dioxide (Liu et al 2023). Similarly, top O 3 -reducing species include common beech, small-and large-leaved lime, London plane, sycamore maple, Norway maple, tulip tree, horse chestnut, and turkey oak (De Marco et al 2017).…”

Phosphorus removal in denitrifying woodchip bioreactors varies by wood type and water chemistry

“…The use of oak woodchips in denitrifying bioreactors is restricted by the USDA NRCS Conservation Practice Standard due to this wood’s high tannin content which was assumed to negatively impact the denitrifying community and/or the downstream aquatic environment (USDA NRCS 2020 ). Despite this concern, oak wood may inherently support greater denitrification potential than other woods (Wickramarathne et al 2021 ). Under the scanning electron microscope, the white oak presented a distinctive case of fungal colonization as nearly all the images showed large masses of hyphae (Fig.…”