This study investigates the distributions of trace metals and their controlling mechanisms in the Kaoping coastal zone. Concentrations of most dissolved metals were generally lower in the wet season than in the dry season in the Kaoping Estuary, showing clearly the effects of river discharge rate and water residence time on metal distributions. Dissolved trace metals (Fe, Mn, Zn, Cu, Cd and Pb) behaved non-conservatively with addition in the estuary. Nevertheless, dissolved Pb was apparently removed from the estuary in the wet season. Particulate Al and Fe were derived mainly from continental weathering and their transports through the estuary depend highly on the distribution of total suspended matter (TSM). During the dry season, the occurrence oxygen-deficit condition in the low salinity region and possible pollution from the San-Wei fishery harbor likely determined the distributions and solid-solution partitions of Mn, Zn, Cu, Cd and Pb in the estuary.
Distributions of dissolved trace metals in the Kaoping coastal zone were significantly influenced by terrestrial inputs from the Kaoping River. Seasonal variations were attributed largely from the mixing between river water and sea water in the mixing layer and sediment resuspension from canyon bed. The column integrated dissolved and particulate metals were generally higher in the summer season than in other seasons. The difference was especially pronounced in nearshore stations. Concentrations of dissolved Mn, Zn, Cu and Pb increased generally with depth, reflecting the effects of resuspension and lateral transport of bottom sediment. Dissolved Zn and Cu concentrations correlated well with dissolved Mn concentration, but particulate Zn and Cu correlated poorly with particulate Al, implying that distributions of Zn and Cu were controlled by terrestrial inputs and biogeochemical processes in the Kaoping Canyon. Positive and negative correlations are found between dissolved Cd and nutrients (N+N¡Aorthophosphate) and between dissolved Cd and dissolved organic carbon (DOC), respectively, indicating that Cd is a nutrient-type metal and controlled biogeochemically in the Kaoping Canyon.
Specific events such as typhoon and earthquake influenced significantly the distributions of trace metals in the Kaoping coastal zone. The integrated suspended-matter and suspended-metal concentrations showed an order magnitude higher during the typhoon season than in the normal summer season. Under the influence of earthquake, the TSM values of the bottom waters were much higher (2-7 folds) during the post- earthquake cruise (Jan/2007) than in the normal season (Jan/2006). Meanwhile, particulate Al, Fe, and Mn can increase up to 2- to 10-folds after earthquake in the bottom layer of canyon.
Metal enrichment factor (EF) is an indicator of metal pollution. The EFs show an order magnitude higher in the dry season than in the wet season both in the estuary and canyon. Such seasonal patterns clearly indicate the impacts of local and river inputs on metal distributions in the estuary and canyon.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0724108-170725 |
| Date | 24 July 2008 |
| Creators | Ho, Chuang-yi |
| Contributors | Jia-Jang Hung, Yung-Chi Chen, Yu-Chia Chung, James T. Liu |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0724108-170725 |
| Rights | unrestricted, Copyright information available at source archive |
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