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The derailment of an unmanned train carrying crude oil and subsequent fire in the town of Lac-Mégantic, Quebec, led to the use of 33 000 L of aqueous film forming foam (AFFF) concentrate. While it is known that per- and polyfluoroalkyl substances (PFASs) contained in AFFFs pose a potential environmental and health risk, critical knowledge gaps remain as regards to their environmental fate after release. The accident in Lac-Mégantic provided valuable information regarding the identity and concentration of PFASs present in the soil after the AFFF deployment, as well as their possible transformation over time. The current study analyzed four sets of samples from Lac-Mégantic: soil collected days after the accident from a heavily impacted area, soil sampled two years later from the treatment biopiles, soil collected two years after the accident from downtown Lac-Mégantic, and nonimpacted soil from a nearby area. A total of 33 PFASs were quantified in the soils. The highest observed concentrations correspond to those of 6:2 fluorotelomer sulfonamidoalkyl betaine, 6:2 and 8:2 fluorotelomer sulfonates, and short chain perfluorocarboxylic acids. The soils collected in Lac-Mégantic two years after the accident show a total PFAS concentration that is ∼50 times lower than soils collected in 2013, while the proportion of perfluoroalkyl acids in those samples shows an increase. Qualitative analysis revealed the presence in soil of 55 additional PFASs that had been previously identified in AFFF formulations. The present study highlights the need to perform detailed analysis of AFFF impacted sites, instead of focusing solely on perfluoroalkyl acids.

Tamarack (Larix laricina [DuRoi] K. Koch) was severely defoliated by the larch casebearer (Coleophora laricella) in most areas of Quebec during 1979 and 1980. Increment core samples were taken in late September 1982 from 20 tamaracks in each of two stands to determine the effect of defoliation on radial growth. In one stand, the trees were 80% defoliated in 1980 and during this year radial growth was reduced by 52%. Growth returned to predefoliation level the following year when the trees were not defoliated. In the other stand, trees were 60% defoliated in 1979 and 70% in 1980. During these years, radial growth was reduced by 48 and 70% respectively. Growth in this stand had not fully returned to predefoliation level two years after the collapse of the infestation. In both stands, variations in defoliation among trees did not exceed 10% of the average. Key Words: Coleophora laricella, larch casebearer, tamarack, larch, defoliation.

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