Rapid enhancement of chemical weathering recorded by extremely light seawater lithium isotopes at the Permian-Triassic boundary.

Lithium (Li) isotope analyses of sedimentary rocks from the Meishan section in South China reveal extremely light seawater Li isotopic signatures at the Permian-Triassic boundary (PTB), which coincide with the most severe mass extinction in the history of animal life. Using a dynamic seawater lithium box model, we show that the light seawater Li isotopic signatures can be best explained by a significant influx of riverine [Li] with light δ7Li to the ocean realm. The seawater Li isotope excursion started ≥300 Ky before and persisted up to the main extinction event, which is consistent with the eruption time of the Siberian Traps. The eruption of the Siberian Traps exposed an enormous amount of fresh basalt and triggered CO2 release, rapid global warming, and acid rains, which in turn led to a rapid enhancement of continental weathering. The enhanced continental weathering delivered excessive nutrients to the oceans that could lead to marine eutrophication, anoxia, acidification, and ecological perturbation, ultimately resulting in the end-Permian mass extinction.

Persistent acid and bile reflux in asymptomatic patients with Barrett esophagus receiving proton pump inhibitor therapy.

HYPOTHESIS: Symptom control does not reflect elimination of abnormal acid reflux or abnormal bile reflux in patients with long-segment Barrett esophagus receiving proton pump inhibitors (PPIs). DESIGN: Prospective survey. SETTING: University hospital. PATIENTS: Thirty-two patients with long-segment Barrett esophagus who were asymptomatic with PPIs. MAIN OUTCOME MEASURES: Twenty-four-hour ambulatory pH and bile reflux monitoring while continuing PPIs. RESULTS: Abnormal acid reflux (pH <4 for 11.9% [interquartile range, 6.8%-19.6%) of 24 hours] persisted in 15 patients (47%) who could not be distinguished from those with normal acid reflux (pH <4 for <4.5% of 24 hours) by any endoscopic, manometric, or therapeutic characteristic. Abnormal bile reflux (absorbance >0.14 for 8.7% [interquartile range, 3.9%-8.7%] of 24 hours) was detected in 11 (48%) of 23 patients, such that both normal bile reflux (absorbance >0.14 for <1.8% of 24 hours) and normal acid reflux were observed in only 8 patients (35%). There was no association between abnormal acid reflux and abnormal bile reflux. CONCLUSIONS: Despite symptom control with PPIs, both acid reflux and bile reflux were controlled in only one third of patients. Posttherapeutic monitoring of acid and bile reflux is recommended in future clinical trials of PPI treatment vs laparoscopic antireflux surgery.