||Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are persistent, ubiquitous, and toxic organic contaminants in coastal sediments. Being hydrophobic in water column, PAHs and PCBs tend to sorb rapidly on particles and eventually accumulate in sediments. Re-suspension of fine or low-density particles from the surface sediment would lead to release of the pollutants bound in sediment particles into water column. This study was to evaluate the potential of remobilization of sediment-bound pollutants into harbor water column by measuring the concentrations and compositions of PAHs and PCBs in different particle size (size fraction: 1000, 500, 250, 125 and 63 μm) and the different density fractions (density: > 2.15, < 2.15 g/cm3) in the Kaohsiung Harbor area. |
The total PAH concentrations obtained from the sediments of Kaohsiung sub-channel (KH1) is higher than those of Shang-Zhu-Li fishing ferry (KH2), but it presents the opposite situation in total PCB concentrations. Total PAH concentrations are 3400 and 1700 (ng/g dw) and total PCB concentrations are 103 and 141 (ng/g dw) at sites of KH1 and KH2. PAH and PCB concentrations in the low-density fraction sediment made up more than 91% and 87% of the total concentration of the bulk sediment, respectively; while low-density fraction sediment made up only 4.3 to 7.7% of the bulk sediment in dry weight.
According to the chemical fingerprinting, PAH source of Kaohsiung sub-channel (KH1) is from pyrogenic which might be from the diesel oil burning of shipping activities and containerized traffic. But the PAH sources in Shang-Zhu-Li fishing ferry (KH2) were from the combustion of coal and petroleum, which is possibly from iron and steel plant and the power plant nearby.
The Toxic equivalents (TEQ) of dioxin-like PCBs in low and high-density fraction
sediments were ranged from 1.1-7.6 pg-TEQ/g and 8.9-1500 pg-TEQ/g, respectively. Based on the Sediment Quality Guidelines (SQGs), only few PAH concentrations in the high-density fraction sediments were higher than the TEL value, while most of PAH concentrations in the low-density fraction sediments ranged between ERL and ERM values. This suggests the low-density sediment particles possessed higher potential of adverse effects to organisms in the aquatic environment.