Evaluation of heavy metal bonding in sediments using sequential extraction analysis: A case study of Kaohsiung Harbor

• Main Authors: Huang min song, 黃閔松
• Other Authors: Dong Cheng Dong
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/84120520799527394890

碩士 === 國立高雄海洋科技大學 === 海洋環境工程研究所 === 96 === Abstract This research, through field sampling and monitoring, conducted analysis on the bonding form of heavy metals in sediments at Kaohsiung Harbor, and took 20 sampling points at Kaohsiung Harbor area as well as the estuary areas of the rivers entering the harbor area (estuary, and 200m and 400m upstream). The items for analysis included particle size, water content, fixed solid substance, total organic matter, total amount of heavy metal (Hg、Pb、Cr、Cd、Cu、Zn、Ni、Mn), mobile phase (exchangeable form, carbonate bonding form, iron and manganese oxide bonding form, organic bonding form) of the bonding form of heavy metals, and immobile phase (residual form). Finally, this research, based on the monitor results, evaluated the impacts of heavy metals in sediments on the ecological environment at the harbor area. According to the result of the analysis on the bonding form of heavy metal in sediment at the harbor area, Hg in residual form had the highest content percentage (86±5%), which indicated that Hg stayed firmly in the sediment, without mobility, and possibly came from the metal existing in the crystal lattice of primary mineral and secondary mineral, while the percent contents of other metals in mobile phase was between 100±0% (Cd) ~ 53±14% (Ni), which indicated the heavy metals in sediment were contributed by artificial pollution, without relatively high mobility and bioavailability. The relative mobility of each metal was as follows, Cd > Cu > Pb > Mn > Cr > Zn > Ni > Hg. Bonding metals in mobile phase would be released due to environmental changes, and sediment in Kaohsiung Harbor could cause environmental changes when dredged. However, since no acid environment (pH<5.0) would be engendered during the dredging environment, the metals released could only exist in exchangeable form with relatively weak bonding strength. Moreover, because the contents was between 0.1 mg/kg (Ni)~17 mg/kg (Mn) (there was no such bonding content with Hg, Pb, Cd, and Cr), the content of heavy metal released from the sediments during the digging process was relatively low. Compared with the total amount of heavy metal, analysis on the bonding form of heavy metal in sediments would provide more information regarding the environment. The easily mobile phase (exchangeable form, carbonate bonding form) of sediment heavy metal with high mobility were likely to move towards the estuary along the river; but in this research, there was not any certain trend could be found in the space distribution in the estuary area, which was probably owing to the fact that the estuary area was located at tidal section, and thus was easy to affected by the rising and falling tide of the sea. The content of mobile phase of sediment heavy metal (Pb、Cr、Cd、Cu、Zn、Ni、Mn) at the rivulet mouth area of brine harbor was higher than those in other river areas. Except for brine harbor rivulet, all the other rivers were treated by river closure. Therefore, it could cause the content of mobile phase of sediment heavy metal at the brine harbor rivulet mouth area higher than those in other estuaries, which possibly had bigger impacts on the environment. In addition, this research utilized multi-variable clustering analysis to conduct statistics on the monitor data, in the hope of searching the characteristics of heavy metal pollution in each area and the spatial clustering relation between estuary area and harbor area, in order to estimate the possible source of the heavy metals in the harbor area. The clustering analysis results showed that clusters appeared at Love River estuary area, the Fifth Ship Canal estuary area, Qianzhen River estuary area, and brine harbor rivulet mouth area, which indicated each estuary area had different pollutant source characteristic. The clusters in Love River and Qianzhen River were close to each other, probably because the pollutant source was mainly urban wastewater, while the major pollutant source at the Fifth Ship Canal was industrial pollution, which resulted in the longest distance between its cluster and other estuaries.