NATURAL GEO-FILTER BED AND HALOPHYTE WETLAND: AN ECOENGINEERING SYSTEM TO MITIGATE SALINE HIGHWAY RUNOFF IMPACTS

摘要

Snow fall and ice storm events are major problems forrnroad security in Canada. As a consequence provinces andrnterritories spread salt and other de-icing products on roadrnand motorway networks in order to protect drivers andrntransporters. Ecosystems located close to transportrnnetworks are affected by salt contamination, in particularrnsmall lakes and ponds suffer from contamination due torntheir low water renewal rates. The Saint-Augustin lakern(0.60 km~2) and its watershed (7.46 km~2) near Old QuebecrnCity are subject of these impacts as every spring highrnamount of salts are carried with highway runoff.rnPreliminary studies have shown that water conductivityrnhas increase rapidly from the construction of motorway inrn1974 (from 350 to 1300 uS/cm) and saline algae havernbeen identified in the sediments of the lake. The goal ofrnthis research project is to evaluate a two-step treatmentrnsystem that will be used to treat saline highway runoffrnwhich contains typically: Na and Ca chlorides,rnPhosphorus (P), Heavy metals and hydrocarbons. Thernsystem includes two unit processes; one is an active filterrnbed packed with an adsorbent geomaterial and an adaptedrnconstructed wetland which uses halophytes plants fromrnthe Saint-Lawrence estuary (Kamouraska, Québec). Thisrnarticle presents the preliminary results on the choice ofrngeomaterial and halophyte plants. The article alsornpresents adsorption (by the geomaterial) and absorptionrn(by halophytes) to retain salt and the other targetedrncontaminants.