PRESENT AND HISTORICAL DISTRIBUTIONS OF HEAVY METALS IN COASTAL SEDIMENTS OFF SOUTHWESTERN TAIWAN

Jia-Jang Hung and Jin-Lung Sheu

Institute of Marine Geology and Chemistry

National Sun Yat-Sen University

Kaohsiung, Taiwan, ROC

Fax: 886-7-5255130

E-mail: hungjj@mail.nsysu.edu.tw

Riverine fluxes and sedimentary distributions of heavy metals were investigated to understand the sources, transports and sinks of heavy metals in the coastal zone off southwestern Taiwan. The major sources of heavy metals in the coastal zone came from polluted rivers and harbors in southwestern Taiwan, even though significant fractions of most metals were retained in estuaries. Anomalous distributions of most metals were generally found in the areas near polluted estuaries and harbors. More than 65% of heavy metals accumulated in surface sediments of the studied area may derive from riverine fluxes. The remaining sources (35%) were derived from atmospheric inputs (5.3 – 31.5%) and marine sewage discharges (0.6 – 6.9%), respectively. Historical records of metal pollution in the coastal zone were constructed from 210Pb-derived sedimentation rates and metal distributions in sediments. Significant enrichments of most metals apparently began from 1976 when was identical to the time of industrial boom in Taiwan. This notion was also supported by the vertical distributions of stable lead isotopic ratios in sediments. The metal enrichment hierarchy was (Cd, Pb > Cu > Zn > Mn, Fe) which may reflect various degrees of anthropogenic inputs in the studied area.