Spatiotemporal Trends of Elemental Carbon and Char/Soot Ratios in Five Sediment Cores from Eastern China Marginal Seas: Indicators of Anthropogenic Activities and Transport Patterns

Elemental carbon (EC), the highly recalcitrant carbonaceous material released exclusively from fossil fuel combustion and biomass burning, is a preferred geochemical agent for evaluating anthropogenic activities. We investigated the spatiotemporal trends of EC and char/soot ratios (char and soot, the two subtypes of EC, differ in formation mechanisms and physicochemical characteristics) in five sediment cores from eastern China marginal seas, spatially spanning from inshore coastal mud areas to offshore remote mud areas. The temporal profiles of EC depositional fluxes closely tracked socioeconomic development in China over the past ∼150 years, with the most pronounced increasing trend beginning in the early 1980s, commensurate with the implementation of national policy of Reform and Open in 1978. The temporal EC profiles in China differed significantly from those in European/American countries, reflecting their different socioeconomic development stages. The spatiotemporal trends of char/soot ratios were also highly informative. Temporally, they decreased from bottom to subsurface layers, indicating the switch of China from an agricultural economy to an industrial economy during the 20th century. Spatially, they decreased from inshore to offshore areas, suggesting the differential transport patterns of EC among these sampling regimes.