Sains Malaysiana 31: 49-56 (2002)                                                                                                                Sains bumi /

Earth Science

 

The Determination of 230Th in the Sediments: Sediment Accretion

in the Mangrove Forests of Tanjung Piai, Johore, Malaysia

 

 

Kamaruzzaman B. Y., Leong H. F., Moho Lokman H.,

Sulong I. & Chong K. Y.

Mangrove Research Unit (MARU)

Institute of Oceanography (INOS)

Kolej Universiti Sains & Teknologi Malaysia

21030 Kuala Terengganu, Malaysia

 

 

 

ABSTRACT

 

Accumulation of element Th with depth was determined in a 150 em core sediment obtained from the mangrove forest of Tanjung Piai, Johore, Malay­sia. In this study, a 230Thexcess method was used where the element relies on a constant production rate of 230Th from the radioactive decay of dissolved 234U in the water column. Applying the 230Thexcess and 230Thexcess/232Th method, average sedimentation rates of 0.84 cmyr-1 and 0.88 cmyrl were obtained, respectively. If this sedimentation rate is applicable to the core, the mangrove forest in the study sites was probably in immature stage with an estimated age of about 120 years. This finding suggests that the mangrove forests are not just passive colonizers of mud banks, but actively capture mud to create their own environments. Mangroves are thus an important sink for the fine sediment from rivers and coastal waters.

 

 

ABSTRAK

 

Akumulasi elemen Th terhadap kedalaman telah ditentukan ke atas 150 cm teras sedimen yang diperolehi di hutan bakau Tanjung Piai, Johor, Malaysia. Dalam kajian ini, kaedah 230Th excess digunakan di mana elemen ini banyak bergantung kepada kadar penghasilan malar 230Th daripada pereputan bahan radioaktif 234U terlarut di dalam air laut. Dengan menggunakan kaedah 230Thexcess and 230Thexcess/232Th, purata sedimentasi masing-masing diperolehi sebanyak 0.84 cmyr-1 and 0.88 cmyr-l. Sekiranya kadar sedimentasi melalui sampel teras diambil kira, hutan paya bakau di Tanjung Piai, Johor berkemungkinan berada dalam peringkat tidak matang dengan anggaran usia lebih kurang 120 tahun. Penemuan ini mensyorkan bahawa persekitaran hutan bakau bukan sahaja dilihat sebagai penghuni pasif dataran lumpur, tetapi bertindak sebagai perangkap sedimen yang aktif. Oleh itu hutan bakau adalah penting dan berperanan bagi memerangkap sedimen halus daripada air sungai dan laut.

 

 

RUJUKAN/REFERENCES

 

Anderson, R.F. 1982. Concentration, vertical flux and remineralization of particulate uranium in seawater. Geochimica Cosmochimica Acta Journal 46: 1293-1299.

Goldberg, E.D. & Koide, M. 1962. Geochonological studies of deep sea sediments by the ionium-thorium method. Geochimica Cosmochimica Acta Journal 26: 417-450.

Harada, K. & Tsunogai, S. 1985. A practical method for the simultaneous determinations of 234Th, 226Ra, 210Pb and 210Po in seawater. Journal of Oceanography Society Japan 41: 98-104.

Kamaruzzaman, B.Y. 1999. Geochemistry of the marine sediments: Its paleoceanographic significance. Doctor of Science dissertation, Hokkaido University.

Kamaruzzaman, B.Y., Suhaimi, H., Teh, E.K., Leong, H.F., Soon, K.H. & Chong, K.Y. 2001a.  The determination of 230Th in the sediments: Sedimentation in the mangrove Forests of Pulau Sekeping, Kemaman, Terengganu. Ultra Scientist of Physical Sciences 13(2): 239-245.

Kamaruzzaman, B. Y., Soon, K. H., Mohd Lokman, H., Sulong, I. & Teh, E. K. 2001b. The Sedimentary Process in the Mangrove Forests of Pulau Che Wan Dagang, Kemaman, Terengganu, Malaysia. Journal of BioScience 12(1): 73-80.

Kominz, M. A., Healt, G. R., Ku, T. & Pisias, N. G. 1982. Brunhes time scales and the interpretation of climate change. Earth Planet & Science Letter 45: 394- ­410.

Ku, T. L. 1976. The uranium-series methods of age detennination. Earth Planet & Science Letter 4: 347-379.

Ku, T. L. & Broecker, W. S. 1966. Atlantic deep-sea stratigraphy, extension of absolute chronology to 320,000 years. Science 151: 448-450.

Mangini, A. & Stoffers, P. 1990. A high resolution 230Th depth profile in a piston core from the Southern Lau Basin. Geology Journal of Reihe 92: 255 -261.

McCabe, W. J., R. G. Ditchbum and N. E. Whitehead 1979. The quantitative separation, electrode position and alpha spectrometry of Uranium, Thorium and Protactinium in silicates and carbonates. Institute of Nuclear Science (NZ) Report 262: 1-29.

Noriki, S., Nakanishi, K., Fukawa, T., Uematsu, M., Uchida, T. & Tsunogai, S. 1980. Use of a teflon vessel for the decomposition followed by the determina­tion of chemical contituents of various marine samples. Bulletin of Faculty of Fishieries, Hokkaido University 31: 354 - 465.

Osmond, J. K. 1979. Accumulation models of 230Th and 231Pa in  deep-sea sediments. Earth Planet & Science Letter 15: 95 - 150.

Scholten, J. C., Botz, R., Mangini, A., Paetsch, H., Stoffers, P., and Vogelsang, E. 1990. High resolution 230Thexcess stratigraphy of sediments from high latitude areas (Norwegian Sea, Fram Strait). Earth Planet & Science Letter 101: 54-62.

Scholten, J. C., Botz, R., Paetsch, H., Stoffers, P. & Weinelt, M. 1994. High ­resolution uranium-series dating of Norwegian Greenland Sea sediments: 23lTh vs._180 stratigraphy. Marine Geology Journal 121: 77-85.

Sen Gupta, J. G. & Bertrand, N. B. 1995. Direct ICP-MS determination of trace and ultratrace elements in geological materials after decomposition in a microwave oven, Quantitation of Y, Th, U and the lanthanides. Talanta 42: 1595-1607.

Suman, D. O. & Bacon, M. P. 1989. Variations in Holocene sedimentation in the Northern American basin determined from the 230Th measurements. Deep-Sea Research Journal 36: 869 - 878.

Tsunogai, S. & Yamada, M. 1979. 226Ra in Bering Sea sediment and its application as a Geochronometer.geochemical Journal 13: 231-238.

Wolanski, E. 1994. Physical Oceanography processes of the Great Barrier Reef Boca Raton, Florida: CRC Press

Wolanski, E., Mazda, Y. & Ridd, P. 1992. Mangrove hydrodynamics. In Robertson, A. I. & Alongi, D. M. (eds.), Tropical mangrove ecosystems. Washington D. C.: American Geophysical Union.

 

 

 

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