Soils contaminated with hydrocarbons (C10–C50), PAHS, lead and other heavy metals were recently found in the banks of two major rivers in southern Québec. Alluvial soils are contaminated over a distance of 100 kilometers. Eight sampling sites, including some located in agriculture areas (farm woodlots) have been selected to compare air pollution (aerosol fallout and rainout) and river pollution values. The concentrations detected in soil profiles for As, Cd and Pb vary between 3.01 to 37.88 mg kg−1 (As), 0.11 to 0.81 mg kg−1 (Cd) 12.32 to 149.13 mg kg−1 (Pb). These metallic elements are considered highly toxic and can harm wildlife and human health at high levels. The maximum concentration of Pb (149.13 mg kg−1) in soils of the riparian zone is twelve times higher than the average Pb concentration found in a natural state evaluated at 15.3 mg kg−1 (SD 17.5). Pb concentrations in soils of agricultural areas (woodland control sites) range between 12 and 22 mg kg−1, and given that these values are recorded in surrounding cultivated land, the issue of the quality of agricultural products (crops and forage) to feed livestock or destined for human consumption must be further addressed in detail.

Hydrocarbon-contaminated layers found over 100 kilometers of riverbanks (southern Québec) were investigated. Analytical results for hydrocarbons, trace metals, Pb concentrations, and Pb isotopic signatures ( 206 Pb/ 207 Pb, 208 Pb/ 206 Pb, 204 Pb/ 206 Pb) of contaminated soil are presented. Soil samples show hydrocarbon concentrations (C 10 -C 50 ) ranging from <60 to 660 mg kg −1 . Higher concentrations were found in the Richmond site (southern Québec). The values for Pb-concentrations ranged between 7 and 149 mg kg −1 with median value of 23 mg kg −1 . For the Pb isotope ratios, the values obtained in the hydrocarbon layer range from 1.124 to 1.175 ± 0.011 ( 206 Pb/ 207 Pb), 2.085 to 2.126 ± 0.011 ( 208 Pb/ 206 Pb), and 0.054 to 0.057 ± 0.000 ( 204 Pb/ 206 Pb). The combination of various techniques used allows us to distinguish the various sources of contaminants.The study also reveals that Pb and other trace metal elements continue to be found in the fluvial environment, even after many years, and this soil pollution could affect the quality of streams and living organisms.

Outilsetméthodes (3)Laboratoire dedendrochronologie etdedendrogéochimie,C ommission géologiqueduCanada (CGC-Québec).

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 heavymetal 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.

ABSTRACT:This research combines a hydrological and pedological approach to better understand the spatial distribution of contaminated soils along the Massawippi River (southern Québec, Canada). This river crosses through former mines, which were some of the largest copper mining areas in North America from 1865 to 1939. To determine the spatial distribution and concentration of the metal elements, soil samples were taken in each flood recurrence zone appearing on official flood zone maps. The maximum values obtained for Cu and Pb are 380 and 200 mg kg −1 , respectively, for the soils in the frequent flood zones (FFzs), while the values for soils in the moderate flood zones (MFzs) range from 700 to 540 (Cu) and 580 to 460 mg kg −1 (Pb). Contamination extends through several kilometers of the former mining sites (Eustis and Capleton), and concentration of metals in alluvial soils is slightly higher near the mine sites.