Study Of Black Carbon And Polycyclic Aromatic Hydrocarbons In Sediments Of The China's Marginal Seas

Black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) are both combustion-derived organic pollutants that are widely dispersed in soils and marine sediments worldwide. Due to the different influence pathways and impacts to the environment and ecosystems, both contaminants have received considerable environmental attention. Black carbon particles with strong absorbing capacity, usually carry high PAHs and transporting to soil and marine sediments. It was the goal of this study to investigate the distribution of BC and PAHs in surface sediments of China's different coastal regions and to examine the correlation of BC and PAHs in the sediments.Results from this study indicate that the distribution of BC in the surface sediments showed a large spatial variation. Bohai Bay sediments had the highest BC contents (average 2.18 mg/gdw) that comprised a significant fraction (27 - 41%) of the total organic carbon preserved in the sediments. In comparison, BC in the surface sediments of the North Yellow Sea, Jiaozhou Bay and the South China Sea was less abundant and accounted for an average of 6%, 8% and 5% of the sedimentary organic carbon pool, respectively. The distribution of BC in the sediments was mainly affected by its sources input. It appeared that anthropogenic influence and river discharge are the main pathways distributing BC to China's coastal sediments. This study suggests that the preservation of BC in the sediment represents an important sink for carbon cycling in China's marginal seas. Concentration of the total PAHs in the surface sediments of China's marginal seas also showed large spatial variations ranging from 47.5 to 3673.5 ng/gdw. Again, Bohai Bay had the highest PAHs concentrations ranging from 82.9 to 3673.5 ng/gdw, reflecting the highly anthropogenic contaminated nature of the region. The distribution of individual PAHs in the sediments also exhibited different patterns among the three coastal regions with Bohai Bay being predominated by the 5 to 6 ring PAHs, while the North Yellow Sea and Pearl River Estuary had relatively higher abundance of 3 to 4 ring compounds. Based on the distribution patterns and by examining the special ratio parameters, it appears that pyrolytic sources (mainly biomass, coal combustion) contributed PAHs to the surface sediments of Bohai Bay, while both petroleum comustion and biomass, coal combustion source contributed PAHs to the sediments of the North Yellow Sea and Pearl River Estuary .A positive linear correlation between BC and PAHs was not found in the surface sediments of the study regions suggesting that the BC and PAHs preserved in the sediments were not all derived from the same combustion sources and their preservation in sediments was controlled by different biogeochemical processes.