SUMMARY
Distribution
and current status of heavy metal contamination in bottom sediments
in the Cửa Ông Harbour,
Hạ Long Bay
Hồ Hữu Hiếu, Phạm Việt Hà
The distribution,
controlling geochemical factors and contamination current status of heavy
metals in bottom sediments near Cửa
Ông Harbour,
Hạ Long Bay have been investigated. 36 surface sediment samples were collected
and analyzed for major elements (Al, Ca, Fe, K, Mg and S), heavy metals (As,
Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn), organic matter, loss
of ignition (LOI), grain size composition and pH. Spatial distribution patterns
of heavy metals as well as their controlling factors have been elucidated based
on geochemical mapping and statistical methods, such as the Pearson
product-moment linear correlation and
factor analysis. The results have been showing that the distribution patterns
of As, Cd, Cr, Cu, Ni, Pb and Zn are mainly controlled by organic matter and
clay minerals and determined by the distribution of the fine-grained fraction (Φ < 63 µm) in sediments. In contrast, Fe and Mn
compounds seem to exert some control on the distribution of Co.
Carbonates partly control the distribution of Mn, but are not important with
respect to the other studied heavy metals. The contamination state by heavy
metals has been assessed based on comparison with Canadian, Wisconsin
(United States)
and Flemish numerical Sediment Quality Guidelines, and calculation of
geo-accumulation index (Igeo) and enrichment factor (EF). The
results have been indicating that natural processes, such as weathering and
erosion of bedrocks, are main supply sources of heavy metals in sediments in
the Cửa Ông Harbour.
Among the studied heavy metals, only As is of concern,
whereas Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn seem to reflect their background
concentration in sediments of the Hạ Long Bay.
Người biên tập: Nguyễn Đại Trung.