Geochemical speciation and risk assessment of heavy metals in southwestern Taiwan coastal sediments

Numerous investigations on aquatic heavy metal distributions in Asia reveal that the riverine and coastal sediments are the major heavy metal carriers responsible for anthropogenic activities. The mobility and accumulation of heavy metals in those sediments are therefore the fundamental knowledge for risk assessment on biotic species. To better constrain the essential parameters influencing the heavy metal distributions, a large-scale systematic investigation is demanded. Hence more than 11 studies were included to re-analyze the heavy metal distribution for their risk assessments in southwestern Taiwan marine sediments. Literature data on the six heavy metals, i.e., Hg, Cd, Cr, Cu, Pb, and Zn, as well as basic characteristics of sediments, in the estuaries, harbors, coast, offshore, and dumping sites were cited. On the other hand, sequential extraction procedure (SEP), isolating metal species among different geochemical forms, was applied on sediments to provide information regarding metal geochemical behavior in details. Although the related literature data is limited, there are already a few papers that have reported geochemical forms of separated heavy metal distribution in the sediment cores. By using statistical analyses on the collected dataset coupled with the SEP data, this study sheds lights on: (1) spatial distribution of heavy metals in the marine sediments of southwestern Taiwan; (2) the essential driving factors influencing the heavy metal distribution; and (3) ecological risk assessment of heavy metal in the Taiwan coastal environments.