Abstract
The burning of trees and grasses produces charred particles, such as charcoal and soot, that can be transported over long distances via winds and rivers to coastal, deltaic, and ocean environments, where they are preserved in sediments. Charcoal contained in sediments has been widely used as a proxy for biomass burning and human activities as well as climate change. Charcoal and soot in Cenozoic marine sediments at Integrated Ocean Drilling Program (IODP) Expedition (Exp.) 346 Site U1423 were measured to examine the regional history of biomass burning in East Asia. Charcoal and soot were measured as elemental carbon (EC) in coarse (> 2 μm) and fine (< 2 μm) fractions using grain size separation by repeated settling followed by application of a thermal optical transmittance (TOT) method. Organic carbon (OC) was also quantified during the process. EC and OC in both coarse and fine fractions are higher from 0 to 1.8 Ma and lower from 1.8 to 4.3 Ma but have large variations, which suggest more frequent or intense biomass burning since 1.8 Ma. Terrestrial biomass and precipitation could be major controls on the EC supply. Fine EC varies independently from coarse EC, which suggests a remote origin of fine EC. Large increases in terrestrial vegetation cover have led to high-temperature burning, which is associated with interglacial stages.
Highlights
Elemental carbon (EC) is a combustion residue defined as “combustion produced black particulate carbon having a graphitic microstructure” (Novakov 1984)
To understand the relationship between organic carbon (OC)/ elemental carbon (EC) supply to Site U1423 and paleoclimate, we examine the proportion of broadleaf (Tw) and the sum of broadleaf (Tw) and conifer (Tc), which is defined as The pollen temperature index (Tp)% (= [The sum of broadleaf (Tw) / (Tw + the sum of conifer (Tc))] × 100); Fig. 5e)
A wet climate was preferable for coarse EC supplies to Integrated Ocean Drilling Program (IODP) Site U1423
Summary
Elemental carbon (EC) is a combustion residue defined as “combustion produced black particulate carbon having a graphitic microstructure” (Novakov 1984). Thermal optical analyses have been widely used as analytical methods that could provide reasonable estimates of EC contents in marine sediments (Buseck et al 2014). Referring to the previous research results, EC could be defined as the high-temperature component of thermal optical analyses, whereas organic carbon (OC) was the low-temperature component of the analyses. EC generally originates from the residues of fossil fuel or biomass burning, and the color is dark, mostly nearly black or brown (Andreae and Gelencsér 2006). The color of EC allows them to absorb a large amount of radiation energy in the atmosphere, which has a significant impact on climate (Buseck et al 2014; Oshima et al 2012)
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