Distribution and Origin of Organic Carbon, Nitrogen and Phosphorus in Kaohsiung Harbor Sediments

Abstract

This study, through on-site sampling, performs a content analysis of total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) contained in Kaohsiung Harbor surface sediments, and accordingly evaluates their temporal-spatial distribution and sources. The results indicate that the TOC content of Kaohsiung Harbor sediments ranges from 1.0 to 7.0% (average 2.3±0.3%) with the highest level of 6.8±0.2% in the Salt River estuary. The TN content ranges from 990 to 10,582 mg/kg (average 2,665±1,800 mg/kg) and the TP values are between 178 and 784 mg/kg (average 363±147 mg/kg). The content distribution of TOC, TN and TP demonstrates a high-to-low sequence: estuary, channel and Harbor, indicating that the organics in the sediments are mainly from the upstream inflow of rivers. The TOC, TN and TP contents in the wet season are obviously higher than those in the dry season, which might result from the terrestrial organics flushed into the Harbor by the seasonal abundant and concentrated precipitation. The C/N ratio of Kaohsiung Harbor sediments is between 4.6 and 26.9, with an average value of 11.9±6.6. Through further estimation, 76.5% of the TOC is identified as terrestrial, and the TN is dominated by marine autogenetic sources.