Impact of wood-derived biochar on the hydrologic performance of bioretention media: Effects on aggregation, root growth, and water retention. (1st August 2023)

• Record Type: Journal Article
• Authors: Akpinar, Derya; Tian, Jing; Shepherd, Elizabeth; Imhoff, Paul T.
• Is Part Of: Journal of environmental management. Volume 339(2023)
• Publication Date: 2023-08-01
• Subjects: Bioretention soil media -- Stormwater management -- Biochar -- Hydraulic conductivity -- Water retention -- Aggregation; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2023.117864
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Bioretention systems are one example of green stormwater infrastructure that may mitigate the hydrologic impact of stormwater runoff. To improve water retention while maintaining rapid stormwater infiltration, conventional bioretention soil media (BSM) might be augmented with biochar. Biochar may improve the BSM's structure by increasing soil aggregation, which might improve water retention and increase stormwater infiltration while also improving root growth. Pots with BSMs representing high and moderate sand content media were amended with a wood-derived biochar, planted with switchgrass, and subjected to weekly storms for 20 weeks, followed by a 10-week drought. In the high sand content medium (NC mix), biochar amendment increased hydraulic conductivity ( K sat ), and this effect increased with time. At 0 weeks, 2% and 4% (w/w) biochar increased K sat by 4 ± 2% and 10 ± 4%, respectively, while at 30 weeks the increase was 30 ± 10 and 70 ± 20%, respectively, above biochar-free media. Similar improvements were seen in plant available water ( PAW ) in NC mix. However, minimal improvements in K sat and PAW from biochar amendment were found in the moderate sand content BSM that contained compost and mulch (DE mix). Where biochar promoted K sat, this was correlated with increased water-stable aggregate size (r = 0.86), fine root volume (r = 0.88), and below ground biomass (r = 0.83). Important factors affecting K sat and aggregation in the NC mix were biochar's influence on organo-mineral association, fungal hyphae length, and plant roots. Wood-derived biochar amendment to BSM may obviate the need for compost/mulch since biochar has similar effects on improving BSM hydrology and root growth without the risk of undesired nutrient leaching. Graphical abstract: Image 1 Highlights: Wood biochar improved stormwater retention and transmission in bioretention media. Improvements were time-dependent and associated with aggregation and root growth. Biochar improved fungal hyphae and organo-mineral association - causing aggregation. Biochar also increased fine roots and root biomass. Biochar may obviate the need for organics like compost/mulch in bioretention media.