• Yuhong Wang

Articles written in Journal of Earth System Science

• Anaerobic oxidation of methane in coastal sediment from Guishan Island (Pearl River Estuary), South China Sea

The concentrations of CH4, SO$^{2−}_{4}$, 𝛴 CO2 and the carbon isotope compositions of 𝛴 CO2 and CH4 in the pore-water of the GS sedimentary core collected from Guishan Island (Pearl River Estuary), South China Sea,were determined. The methane concentration in the pore-water shows dramatic changes and sulfate concentration gradients are linear at the base of the sulfate reduction zone for the station. The carbon isotope of methane becomes heavier at the sulfate-methane transition (SMT)likely because of the Raleigh distillation effect; 12CH4 was oxidized faster than 13CH4 and this caused the enrichment of residual methane 𝛿13C and 𝛿13C-𝛿 CO2 minimum. The geochemical proﬁles of the pore-water support the existence of anaerobic oxidation of methane (AOM), which is mainly controlled by the quality and quantity of the sedimentary organic matter. As inferred from the index of 𝛿13C-TOC value and TOC/TN ratio, the organic matter is a mix of mainly refractory terrestrial component plus some labile alga marine-derived in the study area. A large amount of labile organic matter (mainly labile alga marine-derived) is consumed via the process of sedimentary organic matter diagenesis, and this reduces the amount of labile organic matter incorporated into the base of the sulfate reduction zone. Due to the scarcity of labile organic matter, the sulfate will in turn be consumed by its reaction with methane and therefore AOM takes place.Based on a diffussion model, the portion of pore-water sulfate reduction via AOM is 58.6%,and the percentage of 𝛴 CO2 in the pore-water derived from AOM is 41.4%. Thus, AOM plays an important role in the carbon and sulfur cycling in the marine sediments of Pearl River Estuary.

• A great volcanic eruption around AD 1300 recorded in lacustrine sediment from Dongdao Island, South China Sea

The contents of Ti, Al and Fe₂O₃ in a lacustrine sediment core (DY6) collected from Dongdao Island, South China Sea (SCS), were determined to be much higher than those in the three major sediment endmembers (coral sand, guano and plants), and their likely sources include terrigenous dust and volcanic ash. At 61 cm (~AD 1300), the contents of Ti, Al and Fe₂O₃ have an abnormally high spike, which cannot be explained by terrigenous dust. The Sr and Nd isotope compositions at 61 cm are in excellent agreement with those in volcanic materials, but they are significantly different from those in terrigenous dust, implying a possible material input from historical volcanic eruptions in the lacustrine sediment DY6. The documented great Samalas volcanic eruption at AD 1257 in Indonesia is likely the candidate for this volcanic eruption.

• Mid-to-late Holocene climate change record in palaeo-notch sediment from London Island, Svalbard

The Arctic region is very sensitive to climate change and important in the Earth’s climate system. However, proxy datasets for Arctic climate are unevenly distributed and especially scarce for Svalbard because glaciers during the Little Ice Age, the most extensive in the Holocene, destroyed large quantities of sediment records in Svalbard. Fortunately, palaeo-notch sediments could withstand glaciers and bewell-preserved after deposition. In this study, we reconstructed a mid-to-late Holocene record of climate changes in a palaeo-notch sediment sequence from London Island. Multiple weathering indices were determined, they all showed consistent weathering conditions in the study area, and they were closelylinked to climate changes. Total organic carbon (TOC) and total nitrogen (TN) were also determined, and their variation profiles were similar to those of weathering indices. The climate change record in our sediment sequence is consistent with ice rafting record from North Atlantic and glacier activity from Greenland, Iceland and Svalbard, and four cold periods are clearly present. Our study provides arelatively long-term climate change record for climate conditions from mid-to-late Holocene in Svalbard.

• # Journal of Earth System Science

Current Issue
Volume 128 | Issue 8
December 2019

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019