Atmospheric Particles\nAre Major Sources of Aged Anthropogenic\nOrganic Carbon in Marginal Seas

Abstract

Deposition of atmospheric particulates is a major pathway\nfor transporting\nmaterials from land to the ocean, with important implications for\nclimate and nutrient cycling in the ocean. Here, we report the results\nof year-round measurements of particulate organic carbon (POC) and\nblack carbon (BC) in atmospheric aerosols collected on Tuoji Island\nin the coastal Bohai-Yellow Sea of China (2019–2020) and during\na cruise in the western North Pacific. Aerosol POC contents ranged\nfrom 1.9 to 11.9%; isotope values ranged from −18.8 to −29.0‰\nfor δ¹³C and −150 to −892‰ for\nΔ¹⁴C, corresponding to ¹⁴C ages of 1,235\nto 17,780 years before present (BP). Mass balance calculations indicated\nthat fossil carbon contributed 19–66% of the POC, with highest\nvalues in winter. BC produced from fossil fuel combustion accounted\nfor 18–54% of the POC. “Old” BC (mean 6,238 ±\n740 yr BP) was the major contributor to POC, and the old ages of aerosol\nPOC were consistent with the ¹⁴C ages of total OC preserved\nin surface sediments of the Bohai-Yellow Sea and East China Sea. We\nconclude that atmospheric deposition is an important source of aged\nOC sequestered in marginal sea sediments and thus represents an important\nsink for carbon dioxide from the atmosphere.