Natural levels of hydrogen peroxide (H2O2) in deep clear South temperate lakes: Field and laboratory evidence of photo- and biotic production

GARCIA, PATRICIA E.; GEREA, MARINA; DIÉGUEZ, MARÍA C.

THE SCIENCE OF TOTAL ENVIRONMENT

Elsevier

Año: 2020 vol. 727

0048-9697

Hydrogen peroxide (H2O2) is a ubiquitousreactive oxygen species (ROS) in aquatic systems and is produced mainly insurface water by the interaction of ultraviolet radiation (UVR) and naturaldissolved organic carbon (DOC). Andean Patagonian lakes are ultraoligotrophic,clear systems with extended photic zones (~40 m), and are exposed tochallenging UVR levels due to their lati-altitudinal situation and extremelylow DOC levels. This investigation describes the seasonal levels ofH2O2 inrelation to DOC quality in the water column of lakes Moreno East (ME) andMoreno West (MW), two deep (ca. 100 m), ultraoligotrophic, low-DOC (b0.7 mg L−1)systems of Andean Patagonia. H2O2 concentrations recordedin the lakes were below 60 nM, ranging from ~3 to ~60 nM in Lake ME and from ~5to ~35 nMin LakeMW. In most of the samples of both lakes, the H2O2 levels werehigher in the photic zone (surface to 30?40 m) than the aphotic zone (from30?40mto90?100 m), particularly in summer samples. Laboratory experiments evaluated theabiotic (photochemical) and biotic (microbial) production of H2O2 in seasonal(summer, autumn) samples which varied DOM quality due to lake(ME,MW) and depth(photic and aphotic lake layers) provenance. Abiotic and biotic production of H2O2attained higher levels in summer samples from the photic zones of both lakes.Humic DOM from deep layers (particularly from summer samples) was moresusceptible to both photo- and bio-degradation than DOM from upper lake layers,which was characterized by stronger signs of degradation and progress indiagenesis.