Recent Sedimentation Rates in Yangpu Harbour on Hainan Island

Pan Shaoming; Waug Xueyu; John N.Smith

Four sediment cores, collected in Yangpu Harbour on Hainan Island,were analyzed for textural parameters and Pb- 210, Cs-137 activities,Yangpu Harbour is tidally flushed and has sediment distribution pattern which is related primarily to the tidal current pattern. Sandy(fine and coarse sllty sand ) material is distributed along the tracts of relatively high speed tidal currents underlying the shallower regions of the harbour while finer-grained,silty muds tend to accumulate in the deeper parts of the tidal channel itself. Measurements of textural paramenters have indicated that sedimentation is episodic in many sections of the harbour with successive cycles of particle erosion and deposition leading to the variable accumulation of material,particularly in the tidal channel. Because of complex stratigraphy of interbedded layers of sand and mud,Pb-210 profiles in Yangpu Harbour reveal abnormal distributions. Since the Pb-210 activity was almost exclusively associated with the finegrained,clay,component of the sediment load,the nomalization of these data to the%clay content of the sediment permitted the determination of depositional rates,despite instances of variability in the Pb- 210 activities. The distributions of Cs- 137 in two cores were measured,both the position of the horizon (corresponding to the first appearance of Cs-137 in the environment )and the peak (corresponding to the period of maximum deposition ) have been used to determine sedimentation rates. Rates based on the position of peak of Cs- 137 profile are in good agreement with that based on Pb-210 dating,and rates based on the occurrence of the horizon are slightly larger than that based on Pb-210 dating. Sedimentation rates,determined using P1i-210 and Cs-137 dating methods,were 0. 5-2cm/y in the sediments underlying the tidal channel,and were 1~2cm/y in the sediments on the swash platform area("block gate shoal") during past 100 years.

1 State Pilot Laboratory of Cost & Island Exploitation. Nanjing University;

Publish Date: 1994-06-10

Abstract: Four sediment cores, collected in Yangpu Harbour on Hainan Island,were analyzed for textural parameters and Pb- 210, Cs-137 activities,Yangpu Harbour is tidally flushed and has sediment distribution pattern which is related primarily to the tidal current pattern. Sandy(fine and coarse sllty sand ) material is distributed along the tracts of relatively high speed tidal currents underlying the shallower regions of the harbour while finer-grained,silty muds tend to accumulate in the deeper parts of the tidal channel itself. Measurements of textural paramenters have indicated that sedimentation is episodic in many sections of the harbour with successive cycles of particle erosion and deposition leading to the variable accumulation of material,particularly in the tidal channel. Because of complex stratigraphy of interbedded layers of sand and mud,Pb-210 profiles in Yangpu Harbour reveal abnormal distributions. Since the Pb-210 activity was almost exclusively associated with the finegrained,clay,component of the sediment load,the nomalization of these data to the%clay content of the sediment permitted the determination of depositional rates,despite instances of variability in the Pb- 210 activities. The distributions of Cs- 137 in two cores were measured,both the position of the horizon (corresponding to the first appearance of Cs-137 in the environment )and the peak (corresponding to the period of maximum deposition ) have been used to determine sedimentation rates. Rates based on the position of peak of Cs- 137 profile are in good agreement with that based on Pb-210 dating,and rates based on the occurrence of the horizon are slightly larger than that based on Pb-210 dating. Sedimentation rates,determined using P1i-210 and Cs-137 dating methods,were 0. 5-2cm/y in the sediments underlying the tidal channel,and were 1~2cm/y in the sediments on the swash platform area("block gate shoal") during past 100 years.

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[1]	王颖，朱大奎，1990，洋浦港海岸地貌与海岸工程间题，南京大学学报(地理版),11,1-13.
[2]	李树庆，1987，中国近海放射性水平，海洋出版社，163-169,
[3]	陈绍勇等，1988,泪洲湾沉积物的混合速率和沉积速率的研究，海洋学报，10, 566-579.
[4]	Chanton. J. P.，et al, 1983, Lead-210 sediment geochronology in a changing coastal environment,l3eochim.Geochim. Acts，47, 1791-1804.
[5]	Flynn, W. W.，1968, The determination of low levels of Polonium-210 in environmental mterials. Anal.Chim. Acts.，43, 221-227.
[6]	Koide,，M.，et al.，1972, Th-228/Th-232 and Pb-210 geochronologies in marine and lake sediments.Geochim. Coemochim. Acts, 37, 1171-1187.
[7]	Mccall, P. L.，et al.，1984, Cs-137 and Pb-210 transport and geochronologies in urbanized reservoir withrapidly increasing sedimentation rates. Chemical Geology，99，151-185.
[8]	Megumi, K.，1978, A problem in Pb-210 geochronologies of sediments, Nature, 274,885-887.
[9]	Nittouer, C. A.，et al.，1979, The use of Pb-210 geochronology as a sedimentological tool: Application to the eashington continental shelf, Marine Geology, 31，297-316.
[10]	Olsen, C. R.，et al.，1978, A geochemical analysis of the sediments and sedimentation in the Hudson estuary, J. Sedi. Petro.，48,401-418.
[11]	Robbins, J. A. and Edgington, D. N.，1975, Determination of recent sedimentation events in Lake Michigan using Pb-210 and Cs-137, Geochim. Cosmochim. Acts, 39,285-304.
[12]	Robbins, J. A.，et al.，1978, Compattive Pb-210,Cs-137 and Pollen geochronologies of sediments from Iakes Ontario and Erie,Quat. Res.，10, 256-278.
[13]	Smith, J. N.,et al.，1987, Time-dependent modelling of fallout radionuclide transport in a drainage basin significance of `slow"erosional and "fast" hyrological components, Chem. Geol.,63,157-180.
[14]	Smith, J. N.，and Walton, A.，1980, Sediment accmulation rates and geochtonologies mjasured in the Saguenay Fjord using the Pb-210 dating method, Geochim. Cosmochim. Acta, 44,225-240.
[15]	Smith, J. N. and Ellis, K. M.，1982, Transport mechanism for Pb-210, Cs-u37 and Pu fllout radionuclides through fluvial-marine systems，Geochim. Cosmochim. Acta, 46,941-959.

Recent Sedimentation Rates in Yangpu Harbour on Hainan Island

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