Interactions of polychlorinated biphenyls and organochlorine pesticides with sedimentary organic matter of retrogressive thaw slump‐affected lakes in the tundra uplands adjacent to the Mackenzie Delta, NT, Canada

Abstract

Using a comparative spatial analysis of sediment cores from eight lakes in tundra uplands adjacent to the Mackenzie Delta, NT, we examined how the presence of retrogressive thaw slumps on lake shores affected persistent organic pollutant (POPs, including polychlorinated biphenyls and organochlorine pesticides) accumulation in lake sediments. Sediments of slump‐affected lakes contained higher total organic carbon (TOC)‐normalized POP concentrations than nearby reference lakes that were unaffected by thaw slumps. Mean focus‐corrected inorganic sedimentation rates were positively related to TOC‐normalized contaminant concentrations, explaining 58–94% of the variation in POP concentrations in sediment, suggesting that reduced organic carbon in slump‐affected lake water results in higher concentrations of POPs on sedimentary organic matter. This explanation was corroborated by an inverse relationship between sedimentary POP concentrations and TOC content of the lake water. Inferred chlorophyll a, S2, and S3 carbon fluxes to sediment were not significantly correlated to POP fluxes. Higher POP concentrations observed in sediment of slump‐affected lakes are best explained by simple solvent switching processes of hydrophobic organic contaminants onto a smaller pool of available organic carbon when compared to neighboring lakes unaffected by thaw slump development.

Thermokarst Disturbance Drives Concentration and Composition of Metals and Polycyclic Aromatic Compounds in Lakes of the Western Canadian Arctic

“…The smaller pool of DOC in lakes impacted by thaw slumping would facilitate each unit of OC to scavenge a relatively greater concentration of PACs from the water column, resulting in the higher concentration of PACs per unit of sedimentary OC (MacDonald et al, 2002). A similar process was inferred as driving elevated TOC-normalized persistent organic pollutant concentrations in the same lakes, as persistent organic pollutants are also highly hydrophobic (Eickmeyer et al, 2016). The increase in OC-normalized PAC concentrations could potentially impact benthic organisms that ingest these contaminants and subsequently enter the food web and biomagnify in slump-impacted lakes.…”

“…Sediment cores were collected in 2006 and 2007 from a number of lakes in the region. Results of radiometric dating and core chronology development have been published previously for these same cores (Deison et al, 2012;Eickmeyer et al, 2016;Thienpont et al, 2013). Following the naming established by , lakes impacted by thaw slump activity are indicated as "b" lakes, while reference lakes, similar in size and location but lacking slump activity, are called "a" lakes.…”

“…Sedimentary metals were analyzed for 14 lakes, 7 "reference" lakes (4a, 5a, 6a, 7a, 9a, 14a, and 36a) and their paired slump-affected lakes (4b, 5b, 6b, 7b, 9b, 14b, and 36b) ( Figure 1). Analysis of PACs was conducted on sediment cores from eight of these lakes, 2a, 9a, 14a, 36a, 2b, 9b, 14b, and 36b, the same cores analyzed for PCBs and organochlorine pesticides by Eickmeyer et al (2016). For PAC analysis, samples extracted and analyzed for PCBs and pesticides by Eickmeyer et al (2016) were reanalyzed using Gas Chromatography/Mass Spectrometry.…”

Spatial Distributions and Seasonal Changes of Current‐Use Pesticides from the North Pacific to the Arctic Oceans

“…The present study involved a large-scale investigation of the temporal and spatial distributions of CUPs in surface seawater and atmosphere. Previous studies have focused mainly on CUPs at specific regions or locations (Eickmeyer et al, 2016;Li et al, 2016;Ruggirello et al, 2010;Yeo et al, 2004), with few having largescale profiles (Ma et al, 2015). Zhong, Xie, Cai, et al (2012) studied CUPs during the 4th Chinese National Arctic Research Expedition (CHINARE) in a similar region of the North Pacific Ocean.…”

Paleolimnology of thermokarst lakes: a window into permafrost landscape evolution

“…However, Deison et al (2012) showed that total and methyl mercury were lower in lakes with retrogressive thaw slumping, due to dilution with inorganic material, and concluded that thaw slumps were not a significant source of mercury to lakes of the Mackenzie Delta Uplands. On the other hand, polychlorinated biphenyls (PCBs), a banned class of persistent organic pollutant, as well as organochlorine pesticides were found in greater concentrations in sediment cores taken from lakes with retrogressive thaw slump activity in their catchments (Eickmeyer et al 2016). The dilution by inorganic matter was implicated by the elevated PCB concentrations observed in sediments, as these hydrophobic organic contaminants were associated with and concentrated on the smaller pool of available organic carbon in slump-impacted lakes (Eickmeyer et al 2016).…”