Contrasting arsenic cycling in strongly and weakly stratified contaminated lakes: Evidence for temperature control on sediment–water arsenic fluxes

Abstract

Arsenic contamination of lakebed sediments is widespread due to a range of human activities, including herbicide application, waste disposal, mining, and smelter operations. The threat to aquatic ecosystems and human health is dependent on the degree of mobilization from sediments into overlying water columns and exposure of aquatic organisms. We undertook a mechanistic investigation of arsenic cycling in two impacted lakes within the Puget Sound region, a shallow weakly stratified lake and a deep seasonally stratified lake, with similar levels of lakebed arsenic contamination. We found that the processes that cycle arsenic between sediments and the water column differed greatly in shallow and deep lakes. In the shallow lake, seasonal temperature increases at the lakebed surface resulted in high porewater arsenic concentrations that drove larger diffusive fluxes of arsenic across the sediment-water interface compared to the deep, stratified lake where the lakebed remained~10 C cooler. Plankton in the shallow lake accumulated up to an order of magnitude more arsenic than plankton in the deep lake due to elevated aqueous arsenic concentrations in oxygenated waters and low phosphate : arsenate ratios in the shallow lake. As a result, strong arsenic mobilization from sediments in the shallow lake was countered by large arsenic sedimentation rates out of the water column driven by plankton settling.

Hydrologic control on winter dissolved oxygen mediates arsenic cycling in a small subarctic lake

“…The mobility of arsenic (As) in aquatic systems is largely controlled by the biogeochemical cycling of iron (Fe), sulfur (S), and organic matter (OM) (Kneebone et al 2002; Bauer and Blodau 2006; Root et al 2007; Couture et al 2010). The influence of biogeochemical processes on lake water As can vary seasonally due to changes in lake physical properties, such as sediment temperature (Barrett et al 2019), thermal stratification of the water column (Hollibaugh et al 2005; Senn et al 2007), and in cold regions, development of an ice cover (Schroth et al 2015; Joung et al 2017; Palmer et al 2019), leading to complex trajectories of recovery for As impacted systems. Despite recognition of the seasonality in As mobility, there has been little investigation of As cycling in cold regions, where the development of an ice cover can strongly affect oxygen and temperature conditions in lakes.…”

Contaminated aquatic sediments

“…However, slight adverse effects, that is, growth repression, loss of biomass, and gut malfunction due to ingested material, were noticed on above-mentioned invertebrates after ACC-G application and severe effects were minimized compared to the adverse effects of GAC, PAC and clay particles. Barrett et al (2019) explored the temperature effects on As cycle in contaminated deep, seasonally stratified, oligotrophic lakes (DL, average depth 7.5 m) and shallow, well-mixed, eutrophic water bodies (SL, average depth 2.6 m) to understand As flux in water-sediment interphase as As remobilization from sediment was varied from 11 to 127 µg m −2 d −1 and 15-1,302 µg m −2 d −1 in DL and SL, respectively, while As removal by sedimentation on lakebed was varied from 5.1 to 51 µg m −2 d −1 and 174-964 µg m −2 d −1 in DL and SL, respectively; and maximum bottom water As concentration was measured about 3.5-56.3 µg/L and 29.6-70.6 µg/L in DL and SL, respectively. Although a number of mechanisms, that is, sorption, desorption, co-precipitation, ion exchange, biotransformation, and bioaccumulation, as well as factors, for example, Fe or OC or PO 3− 4 concentration, oxygen concentration, biotic uptake rate, turbulence, mixing, wind speed, advection, molecular diffusion, phytoplankton or zooplankton density, and sedimentation, can control fate and transport of As in aquatic ecosystem; temperature (4-20°C) can significantly influence the microbial respiration and kinetics, OC availability and As mobility in DL rather than the influencing parameters in SL.…”

Grain-Scale Analysis of Solid-Phase Organic Matter and Arsenic Mobility in Mining-Impacted 1 Sediment from Sub‐Arctic Lakes, Northwest Territories, Canada

“…Lakes affected by gold mining activities already have elevated concentrations of As in sediments due to input from tailings, waste rock, effluent, airborne emissions, windblown dusts, and/or mineralized bedrock (DeSisto et al, 2011;Craw and Bowell, 2014;Galloway et al, 2015Galloway et al, , 2018Miller et al, 2019;Palmer et al, 2019). Changing redox conditions in the water column and near-surface sediments driven by seasonal variations and longer-term changes associated with increased OM flux can cause the release of As from sediments to overlying surface waters (Martin and Pedersen, 2002;Bauer and Blodau, 2006;Couture and Van Cappellen, 2011;Anawar et al, 2013;Barrett et al, 2019;Palmer et al, 2019;Schuh et al, 2019). The influence of dissolved OM (DOM) and changing redox conditions on the geochemical cycling of As is well documented (e.g., Redman et al, 2002;Bauer and Blodau, 2006;Mladenov et al, 2015;Lawson et al, 2016); however, the role of solid-phase OM (i.e., OM > 0.22 to 0.45 µm) is not as well understood (Langner et al, 2011;Anawar et al, 2013;Biswas et al, 2019), especially in lakes (Galloway et al, 2018).…”