Sub-bottom acoustic profiling as a remediation assessment tool for contaminated lakes

Abstract

Frame Lake, a small (88.4 ha), shallow (< 6.5 m maximum depth), high-latitude lake found within the city limits of Yellowknife, Northwest Territories, Canada was selected due to the known legacy contamination of the lake's sediments to test the feasibility of using seismic sub-bottom profiling to estimate total volumes of heavy metal contaminated sediments in lacustrine environments. To ground-truth the sub-bottom profiling results, physical and ICP-MS analyses were carried out on freeze cores collected from Frame Lake's southern basin, and sedimentological marker beds and 14 C dating was used to chronologically constrain the lake depositional history. ICP-MS results showed high levels of arsenic contamination (up to 1538 µg g −1) in late twentieth-century lake sediments, which contrasts sharply with measured Holocene values that averaged only 16 µg g −1 (n = 41, ± 5.4 SD). The high arsenic content in lakebed sediments, which tends to be concentrated within specific horizons, results in distinct seismic reflectors within the acquired Sonar data. Stratigraphic horizons where arsenic was concentrated do not necessarily correlate with actual depositional events as changes in lake hydrology and redox conditions have resulted in remobilization and migration of arsenic in lake sediments. Direct GIS software comparison of core data against the sub-bottom profiler transect results permitted an interpolated lateral and vertical reconstruction of the distribution of variously contaminated sediments throughout the entire lake basin. Based on our analysis, a minimum of ~ 230,000 m 3 of contaminated sediments would need to be dredged from Frame Lake to achieve a minimum residual sediment arsenic concentration of < 150 µg g −1 .

A novel protocol for mapping the spatial distribution of storm derived sediment in lakes

“…Spatial and nonspatial statistical methods, such as kriging, have played an important role in geochemical pattern recognition in lakes [49]. Results displayed in a spatial manner facilitate the identification of depositional areas and catchment influences, which is important for designing subsequent sampling plans for future field work (e.g., [50]). Ordinary kriging, which is the most widely used form of spatial interpolation among the various kriging methodologies [51], was used to generate continuous maps of the results throughout the entirety of the Harvey Lake basin.…”

Lacustrine Arcellinida (Testate Lobose Amoebae) as Bioindicators of Arsenic Contamination: A new tool for Environmental Risk Assessment

“…Of the controls on arcellinidan distribution identified in Frame Lake, Ca (9.5%; pvalue < 0.004), Olsen P (10.5%; p-value < 0.005), and especially As (15.8%; pvalue < 0.003) contributed the most toward explaining the variance in the arcellinidan distribution. The observation that As is the most significant control in Frame Lake is not surprising given the results of previous studies that have identified the impact of As contamination on the lake's ecology and sediment quality (Drizawsky andWilson, 2013, 2016;Menard et al, 2019).…”

“…Frame Lake has a relatively small surface area (88.4 ha) with a maximum length and width of 1.75 km and ~ 1 km, respectively (Healey, 1973;Dirszowsky and Wilson, 2016). The lake has a maximum depth of 4.5m in the southern basin and 5.5m in the northern basin (Menard et al, 2019). In terms of morphology, Frame Lake is of an elongate shape (southwest-northeast trend) that widens toward the northeastern end of the lake (Figure 3.1B).…”

“…Concentrations of Olsen P are generally low in Frame Lake (median Olsen P concentrations = of 44 mg.kg -1 ; n = 25) and are highest in samples from the southern part of the lake (median Olsen P range = 49.5-60 mg.kg -1 ; n = 14; Supplementary Table 5.1). Elevated levels of Olsen P in and around the southern basin may be attributed to inputs from nearby residential and private facilities as well as municipal storm water drainage outflow Menard et al, 2019). Olsen P is a good indicator of bioavailable phosphorus in soils and lakes, with higher concentrations indicating nutrient rich, productive, and eutrophic conditions (Zhou et al, 2001).…”

“…In this study, we examine Arcellinida species and strains in 40 surfacesediment samples from two lakes in the central NT with the aim of quantifying their response to intra-lake variability of As concentrations and other controls. The studied lakes are Frame Lake (62.454°N, -114.390°E; n = 25; Figure 1B) Mine, and suspected illegal dumping of sediments Menard et al 2019). Elevated As levels in Hambone Lake are derived from the operations of the nearby Tundra Mine, and are the result of weathering of mine tailings and seepage from tailings containment ponds near the lakes western shore Miller et al, in 2019).…”