CSBE-SCGAB

Bioretention systems in montreal tree pits

Authors: Kargar, M, Og Clark, P Jutras, W Hendershot, S Prasher
Description: Montreal urban trees currently have a short life span because of soil compaction caused by sidewalk and road construction, and pedestrian traffic, and runoff polluted with heavy metals and deicing salts. Runoff from roads and sidewalks also carries pollutants to adjacent green areas and cause plant damage. Bioretention systems are a best management practice (BMP) for managing runoff. These vegetated soil systems reduce suspended solids, nutrients, and heavy metals by filtration, adsorption to soil particles, and biological uptake. A collaborative study between McGill University and the City of Montreal has as its objective the specification of a soil mixture for bioretention in urban tree pits. Bench studies using soil column extraction and biological toxicity tests will be used to measure heavy metal mobility and nutrient availability in the presence of deicing salt, in soil mixtures with various fractions of loam, compost and biochar. The soil mixtures, spiked with known quantities of heavy metals and salt, will be used in a 14-day phytotoxicity test based on the emergence and growth of barley (Hordeum vulgare). Based on the results of this study, an optimum soil mixture will be recommended for use as a bioretention medium in tree pits. A two-year study will monitor the actual function of the recommended soil in 48 tree pits in the Hochelaga-Maisonneuve neighbourhood of Montreal by sampling from zero-tension lysimeters and logging environmental data. The results of the monitoring study will be used in planning large-scale deployment of soils for bioretention in Montreal tree pits.
Keywords: bioretention systems, heavy metals, salt, tree pits, compost, biochar , optimum soil mixture
Technical field: technical_fields_app3
Session name: Ecological engineering
Date: 2012
Identifier: CSBE12098
Coverage: Canada

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