Biogeochemical changes at the sediment–water interface during redox transitions in an acidic reservoir: exchange of protons, acidity and electron donors and acceptors

Abstract

Redox transitions induced by seasonal changes in water column O 2 concentration can have important effects on solutes exchange across the sediment-water interface in systems polluted with acid mine drainage (AMD), thus influencing natural attenuation and bioremediation processes. The effect of such transitions was studied in a mesocosm experiment with water and sediment cores from an acidic reservoir (El Sancho, SW Spain). Rates of aerobic organic matter mineralization and oxidation of reduced inorganic compounds increased under oxic conditions (OX). Anaerobic process, like Fe(III) and sulfate reduction, also increased due to higher O 2 availability and penetration depth in the sediment, resulting in higher regeneration rates of their corresponding anaerobic eacceptors. The contribution of the different processes to oxygen uptake changed considerably over time. pH decreased due to the precipitation of schwertmannite and the release of H ? from the sediment, favouring the dissolution of Alhydroxides and hydroxysulfates at the sediment surface. The increase in dissolved Al was the main contributor to water column acidity during OX. Changes in organic matter degradation rates and coprecipitation and dissolution of dissolved organic carbon and nitrogen with redox-sensitive Fe(III)

What supports the deep chlorophyll maximum in acidic lakes? The role of the bacterial CO2 production in the hypolimnion

“…Values of this flux were estimated by inverse modeling considering a range between the zero‐flux of CO 2 from the sediment as the “minimum flux” and the flux of CO 2 in the hypolimnion as the “maximum flux,” which was determined for each sampling. Sediment CO 2 fluxes were similar to the experimentally determined CO 2 efflux obtained on the September 25 th and to previous studies (Torres et al ; Corzo et al ).…”

“…The values of the half‐saturation constant for aerobic respiration K S and the half‐inhibitory constant for anaerobic respiration K I and the profiles of the bacterial respiration rates extracted from the model (results not shown) suggest that in the hypoxic conditions prevailing at the bottom of the metalimnion and in the hypolimnion, both aerobic and anaerobic metabolism occur at the same time (Gerritse et al ). Closer to the sediment, the O 2 availability decreases, and a higher fraction of the OM is probably mineralized by anaerobic respiration pathways (Torres et al ; Corzo et al ).…”

Geochemical Characteristics of Sediment in Tropical Lake Sentani, Indonesia, Are Influenced by Spatial Differences in Catchment Geology and Water Column Stratification

“…1 and 4). Even in highly oligotrophic lake systems with low sediment organic carbon concentrations and fully oxygenated bottom waters, oxygen penetrates at most only a few mm into the sediment (Corzo et al, 2018). Therefore, reducing conditions and hence anaerobic processes are prevalent in the sediment at all locations (Figure 3).…”

Diel patterns of microphytobenthic primary production in intertidal sediments: the role of photoperiod on the vertical migration circadian rhythm

“…Most likely, the availability of organic substrate will follow a daily dynamic similar to P N affecting the activity of the microbial heterotrophic community 11,56–58 . In addition, the changes in O 2 availability during the light period, both in terms of Max O 2 and z ox (Figs 1, 2 and 4), can largely alter the availability of alternative electron donors and acceptors and consequently the relative contribution of oxic and anoxic mineralization near the sediment surface 4,59–61 and the net exchange of solutes across the sediment-water interface 55 . Evidently, larger differences are expected between day and night.…”