The Geochemical and Environmental Characteristics of Trace Metals in Coastal Sediment Discharge off the Mailiao Industrial Zone of Central Western Taiwan

The geochemical fractions of trace metals in the coastal sediments of the central western Taiwan were examined, employing the Tessier sequential extraction method, and the metals contamination status of the analyzed sediments were also evaluated in the present study. Based on the metal fraction present in sediments, trace metals can be divided into three groups: (1) Al, Cr, Fe, Ni and Zn; (2) Cu and Pb and (3) Mn. In group (1) metal, the metals' total concentrations were chiefly dominated by the residual fraction, exceeding 80% of the total concentration pool. In group (2) metal, the metals' total concentrations were dominated by three labile fractions, carbonate, Fe-Mn oxides and organic, accounting for nearly 65% of the total pool, and the residual fraction contributed 35% of the total concentrations. Over 90% of Mn total concentrations were shared by three fractions, carbonate, Fe-Mn oxides and the residual fraction. The statistic results indicated that the total organic carbon contents in sediments played a more important role in influencing the metals contents in sediments. The contamination assessment results suggested that the Mailiao coastal sediments were minorly contaminated by trace metals. Lead should be paid more concerns because Pb total concentrations at some sediments exceeded the value (46.7 mg/kg) of effect range low, USA, and Pb was mainly present in the labile fraction.

Automated summary

The geochemical fractions and contamination status of trace metals in coastal sediments of central western Taiwan were investigated using the Tessier sequential extraction method. The trace metals were classified into three groups based on their fractions in sediments. The study found that the total concentrations of metals in group 1 were mainly dominated by the residual fraction, whereas group 2 metals had significant contributions from labile fractions such as carbonate, Fe-Mn oxides, and organic matter. The results also highlighted the importance of organic carbon content in sediments in influencing the metals' concentration. The contamination assessment showed minor contamination by trace metals in the Mailiao coastal sediments, with particular concern on lead due to its presence in the labile fraction.