Abrasion of sedimentary rocks as a source of hydrogen peroxide and nutrients to subglacial ecosystems

[摘要] Glaciers and ice sheets are renowned for their abrasive power, yet little is known of the mechanochemical reactions which are initiated by abrasionin these environments and their effect on subglacial biogeochemistry. Here, we use sedimentary rocks representative of different subglacialenvironments and from a previously glaciated terrain, along with subglacial sediments, to investigate the potential for subglacial erosion togenerate H 2 O 2 and to release bio-utilisable organic carbon and nutrients ( N , Fe ). Samples were crushed using a ball mill,water was added to rock powders within gastight vials, and samples were incubated in the dark at 4  ∘ C . Headspace and water samples were takenimmediately after the addition of water and then again after 5 and 25  h . Samples generated up to1.5  µmol H 2 O 2  g −1 . The total sulfur content, a proxy for the sulfide content, did not correlate with H 2 O 2  generation, suggesting that the pyrite content was not the sole determinant of net H 2 O 2  production. Other factorsincluding the presence of carbonates, Fe -driven Fenton reactions and the pH of the solution were also likely to be important in controllingboth the initial rate of production and subsequent rates of destruction of H 2 O 2 . Further, we found that erosion can provide previouslyunaccounted sources of bio-utilisable energy substrates and nutrients, including up to 880  nmol CH 4  g −1 ,680  nmol H 2  g −1 , volatile fatty acids (up to 1.7  µmol acetate g −1 ) and 8.2  µ mol NH 4 + g - 1 to subglacial ecosystems. These results highlight the potentially important role that abrasion plays in providing nutrient and energy sources tosubglacial microbial ecosystems underlain by sedimentary rocks.

[学科分类] 大气科学