Metal distribution and speciation in the surface sediments from Kaohsiung ocean disposal site

• Main Authors: Jhih-Syue Lin, 林治學
• Other Authors: Chiu-Wen Chen
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/41151112986902652932

碩士 === 國立高雄海洋科技大學 === 海洋環境工程研究所 === 103 === This study was performed with dredged sediments in Kaohsiung area in order to assess the impact of heavy meatals in sediments on the disposal zone. Sediment samples were collected at 12 stations, including estuaries, waterways and ports and other areas; marine disposal areas included 12 stations, namely four vertices stations, a center stations, four wheel throwing district point disposal area outside the station and three reference points stations. The dredged sediments was evaluated by a five-step sequential extraction procedure(exchangeable E1, carbonate E2, Fe-Mn oxides E3, organic matter E4, and residual E5) and total heavy metals were analysis. The results showed that total metal content in the sediments from Kaohsiung Harbor. The average concentration of each metal was displayed copper, 120 ± 146 mg / kg, zinc, 403 ± 292 mg / kg, nickel, 33 ± 14 mg / kg, cadmium 0.46 ± 0.33 mg / kg, chromium 112 ± 82 mg / kg and lead 40 ± 15 mg / kg. The concentration of heavy metals followed the order: estuary> channel> harbor, which was caused by pollutants from urban and industrial waste water upstream of the river. The sequential extraction analysis showed that, the highest percentages of Cd and Zn were found in the carbonate fractions (31-37%), Cu, Cr and Pb was found in the organic matter fractions (45-85%), Ni was mainly bound to resudials fractions (56%). Considering the percentage of metals extracted in the non-resdiual fractions (E1+E2+E3+E4) of the sediments, the order of decreasing mobility was: Cd (96%) > Cu (91%) > Pb (86%) > Zn (76%) > Cr (57%) > Ni (43%), these results showed that, the heavy metals had potential mobility in sediments from Kaohsiung harbor, and mainly from anthropogenic pollution. The results showed that total metal content in the sediments from disposal area, except that Cd less than the MDL. The average concentration of each metal was displayed Cu (25±10 mg/kg), Zn (83±28 mg/kg), Ni (23±8 mg/kg), Cd (<0.01 mg/kg), Cr (54±27 mg/kg) and Pb (22±5 mg/kg) in disposal areas vertex and round of throwing district center. The metals content significant less then the harbor sediments., the Cu, Zn, Ni, Cr and Pb low approximately 4.8, 1.8, 4.9, 1.8 and 1.4 times. The sequential extraction analysis showed that, the highest percentages of Cu were found in the organic metter fractions (44-57%), Pb was mainly bound to Fe-Mn oxides fractions (36-53%), Zn, Ni and Cr is consistent with strong fractions by residual (34-82%). The order of decreasing mobility was: Pb (87%) > Cu (82%) > Zn (66%) > Ni (53%) > Cr (46%)；and reference point was: Pb (85%) > Cu (79%) > Zn (54%) > Ni (47%) > Cr (23%). These results showed that, disposal area were similar to the reference point, after dredging sludge disposal may be due to their heavy metal has shown a trend of stability of the phase distribution. The assess degree of pollution with Individual Contamination Factors (ICFs) and Global Contamination Factors (GCFs) in sediments. The results showed that, the highest level of ICFs for Zn, Cd and Pb, the aquatic environment having a relatively high potential risk；Disposal areas With respect to the lower harbor. The GCFs displayed metals higher impact on the marine environment and biological potential risks in sediments of the Kaohsiung Harbor than disposal area. The Risk Assessment Code (Risk Assessment Code, RAC) showed that cadmium metal Kaohsiung area, although low environmental concentrations, but its high toxicity and high mobility (high proportion of non-residual state), resulting in the highest risk assessment of the RAC, may cause harm the ecosystem, the remaining metal was no risk assessment results and low risk level. The findings will help future elaboration management and control strategy of Kaohsiung marine dredging mud disposal areas, to assess whether the cause secondary environmental pollution.