Sediment Records of Polycyclic Aromatic Hydrocarbons (PAHs) in the Continental Shelf of China: Implications for Evolving Anthropogenic Impacts

Sources, compositions, and historical records of polycyclic aromatic hydrocarbons (PAHs) in sediment cores collected from the Yellow Sea and the South China Sea were analyzed to investigate the influence of anthropogenic activities. The occurrence of PAHs was mainly derived from various combustion sources, especially the combustion of biomass and domestic coal. Uniform composition of sedimentary PAHs (52-62% of phenanthrene, benzo[b]fluoranthene, indeno[1,2,3-cd]pyrene, and benzo[g,h,i]perylene) suggested air-borne mixtures intractable to degradation. The concentrations of the sum of 15 PAHs (16 priority pollutants designed by the United States Environmental Protection Agency minus naphthalene; designed as Σ(15)PAH) in Yellow Sea sediment cores were generally higher than those in the South China Sea. The profiles of Σ(15)PAH concentrations recorded in the sediment cores closely followed historical socioeconomic development in China. In general, Σ(15)PAH concentrations started to increase from the background pollution level posed by agricultural economy at the turn of 20th century. In addition, a Σ(15)PAH concentration reduction was observed during the Chinese Civil War (1946-1949) and Great Cultural Revolution (1966-1976), suggesting them as setbacks for economic development in Chinese history. Increasing PAH emissions as a result of increasing coal combustion associated with the rapid urbanization and industrialization since the implementation of the Reform and Open Policy (since 1978) accounted for the fast growth of Σ(15)PAH concentrations in sediment cores. The decline of Σ(15)PAH concentrations from subsurface maximum until sampling time was inconsistent with current-day economic development in China, and may possibly suggest emission reductions due to decreasing proportional use of domestic coal and increasing consumption of cleaner energies (natural gas and liquefied petroleum gas).