Impacts of a massive release of methane and hydrogen sulfide on oxygen and ozone during the late Permian mass extinction

摘要

The largest mass extinction of animals and plants in both the ocean and on land occurred in the late Permian (252 Ma), largely coinciding with the largest flood basalt volcanism event in Siberia and an oceanic anoxic/ euxinic event. We investigated the impacts of a massive release of methane (CH_4) from the Siberian igneous province and the ocean and/or hydrogen sulfide (H_2S) from the euxinic ocean on oxygen and ozone using photochemical model calculations. Our calculations indicated that an approximate of 14% decrease in atmospheric O_2 levels would have occurred in the case of a large combined CH_4 and H_2S flux to the atmosphere, whereas an approximate of 8 to 10% decrease would have occurred from the CH_4 flux and oxidation of all H_2S in the ocean. The slight decrease in atmospheric O_2 levels may have contributed to the extinction event. We demonstrate for the first time that a massive release of CH_4 from the Siberian igneous province and a coincident massive release of CH_4 and H_2S did not cause ozone collapse. A collapse of stratospheric ozone leading to an increase in UV is not supported by the maximum model input levels for CH_4 and H_2S. These conclusions on O_2 and O_3 are correspondent to every H_2S release percentages from the ocean to the atmosphere.