A study of trace metal contamination of the sediments and the aquatic organisms in the Pearl River estuary and the surrounding coastal regions

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A study of trace metal contamination of the sediments and the aquatic organisms in the Pearl River estuary and the surrounding coastal regions


Author: Ip, Ching-man
Title: A study of trace metal contamination of the sediments and the aquatic organisms in the Pearl River estuary and the surrounding coastal regions
Degree: M.Phil.
Year: 2004
Subject: Hong Kong Polytechnic University -- Dissertations
Metals -- Environmental aspects -- China -- Pearl River Delta
Soil pollution -- China -- Pearl River Delta
Department: Dept. of Civil and Structural Engineering
Pages: xvii, 194 leaves : ill. (some col.) ; 30 cm. + 1 computer optical disc
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1772673
URI: http://theses.lib.polyu.edu.hk/handle/200/1897
Abstract: The main aim of this research project is to study the trace metal contamination in the Pearl River Estuary (PRE) and the surrounding coastal regions. Sediment samples were collected in the PRE and the surrounding coastal areas. Some aquatic organisms were also sampled in the PRE. The trace metal contamination in the PRE and the surrounding coastal regions were studied in terms of the degree of metal contamination, sources of contaminants and metal influx rates. Sediment cores from the PRE were analysed for trace and major element concentrations, Pb isotopic composition and 210Pb dating. The analytical results showed that relatively higher sedimentation rates were recorded starting from the 1970s, which reflected the increased surface runoff into the PRE arisen from the rapid economic development in the PRD region. The Pb isotopic compositions showed that the sediments in the PRE started to receive large anthropogenic inputs of trace metals from the 1970s. In addition, the synchronous temporal changes of Pb concentration, 206Pb/207Pb ratios and normalised influx of Pb in the PRE sediments showed that the Pb enrichment in the surface sediments was mainly caused by increased anthropogenic inputs in recent decades. Trace metal concentrations at the surrounding coastal regions of the PRE showed a typical concentration gradient from land to sea direction. The spatial distribution of trace metal concentrations reflected the major contamination sources, including the direct effluent discharges from the west coast of the PRE. The results of spatial distribution and statistical analysis showed that the trace metal distribution patterns at the coastal regions can be categorised in terms of five major areas, (1) the delta, (2) the inner shelf, (3) the northwest inner shelf, (4) the middle shelf, and (5) the outer shelf base. The chemical partitioning of Cu, Fe and Zn indicated that these metals remained in relatively stable forms in the sediments. Based upon the Pb isotopic composition of selected sediment samples and of the different chemical fractions, the Pb from anthropogenic sources was generally associated in the non-residual fractions of the sediments. Four groups of aquatic organisms, including fish, crab, shrimp and shellfish, were collected in the PRE for trace metal and Pb isotopic analysis. Elevated amounts of trace metals were found in shellfish compare to other species, suggesting that shellfish tend to accumulate more trace metals. In comparison with the baseline reference values in Norway, the highest enrichment factor of trace element concentrations was found in fish. The results of Pb isotopic compositions indicated that the Pb accumulated in the aquatic organisms was mainly attributed to anthropogenic Pb inputs. The hazard index (HI) calculated with Pb concentration in fish showed that potential health impacts were associated with the fish species containing high metal concentrations in the PRE.

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