Spatial Variability of Heavy Metal Contamination in Alluvial Soils in Relation to Flood Risk Zones in Southern Québec, Canada

Abstract

The contamination of rivers and riparian soils is a growing problem for several catchments in southern Quebec due to agricultural pollutants and other sources of pollution. This study deals with the concentration of heavy metals in alluvial soils and their spatial variability following the various flood return periods (0-20 years and 20-100 years) and outside flood zones. The heavy metal concentration of some soils exceeds levels in government standards. The elements with the highest concentrations are mainly Ni, Pb and Zn. For instance, the levels of Zn and Pb can be as high as 310 and 490 mg kg-1. In general, heavy metal concentrations are highest in active sedimentation zones (0-20 yrs). In this instance, the ANOVA test was conducted to determine whether the differences in heavy-metal concentrations in the soils could be significant between the three zones (Frequent Flood (FF), Moderate Flood (MF), and No Flood (NF)). With the increase in the flood return rate and current hydroclimatic changes, a downstream remobilization of contaminants can be expected, leading to a larger riparian area of contamination.