http://hdl.handle.net/20.500.12066/4364 2026-04-06T19:34:24Z http://hdl.handle.net/20.500.12066/4386 Oil pollution in the Vietnamese waters Ha, Dang Thi Cam; Phuong, Nguyen Thanh; Huu, Nguyen Ba; Huy, Nguyen Quang; Hoa, Tran Nhu; Nga, Cu Viet; Dung, Vu Thi; De, Nguyen Thi Enumeration of hydrocarbon-degrading microorganisms (HDM) and their degradative capacity studies were carried out in area IV of South China Sea (Vietnamese water). Microbial most probable number (MPN) varied from 10¹ to 10⁵ cell/ ml of surface seawater or gram of sediment. Some microbial communities and bacterial strains isolated from 97 collected samples show high hydrocarbon degradation and surfactant producing abilities. Preliminary results of our microbial study indicated that oil pollution in IV area was not found in 30 research stations. Slight oil contamination was observed in 28 survey stations. 2001-01-01T00:00:00Z http://hdl.handle.net/20.500.12066/4385 Sedimentological characteristic of bottom sediment of Vietnamese coastline Mien, Dao Thi; Lam, Doan Dinh During survey of SEAFDEC vessel in May, 1999, 39 samples of bottom sediments of Vietnamese coastline were collected. The samples were analyzed for their sedimentological, micropaleontological characteristics as well as for their total organic matter and mineralogical composition of sediments. The study area can be divided into three parts: northern, central and southern part. Northern and southern parts are characterized by a wide, shallow continental shelf, while central part has very narrow continental shelf. Generally, in the southern part sand is more spread, especially in the front of the Maekong river mouth (25.64% of total sediments), sediments is coarser than in others (average mean size is 0.162mm), better sorted, less skewed. In the northern part, clayish silts, clayish, sandy silts are most spread, sediments are poor sorted, moderate skewed. Average mean size is 0.088mm. In the central part, clayish, silty sand is dominant. Average mean size is 0.1507mm. Sediments are poor sorted. Result of study revealed an occurrence of 98 foraminifers species in the bottom sediments, 19 of them are plankton and 79 are benthos. A content of total organic matter in the study area varies from 0.125% to 1.344%. High content of TOM is observed in the central part, as well as in the south western part. A study on mineralogical composition has pointed out a presence of 35 minerals in bottom sediment. 2001-01-01T00:00:00Z http://hdl.handle.net/20.500.12066/4384 Analysis and estimation of trace metals in seawater and sediment in the South China Sea, Area IV: Vietnamese waters Gian, Trinh Xuan Water samples from off shore of Vietnam from latitude 6°N to 21°N and longitude 103°C to 112°E were collected on 30 April 1999 to 29 May 1999 and analyzed for copper (Cu), lead (Pb), cadmium (Cd), zinc (Zn), nickel (Ni), chromium (Cr), arsenic (As) and mercury (Hg). The concentration of metals Cu, Pb, Cd, Zn, Ni and Cr was measure using flameless atomic absorption spectroscopy. The total concentration of all eight metals was in concentration ranges of unpolluted coastal water. The results indicated that the concentration of metals in bottom layer higher than in surface layer. Also, trace metal contents in the surface sediment were studied in off shore of Vietnam during this cruise. Total metals content were measured. The range of concentration of metals were 10.3 - 71.0 mg.g^-1 for Cu, 12.9 - 33.7 mg.g^-1 for Pb, 1.29 - 18.72 mg.g^-1 for Cd, 45.8 - 164.8 mg.g^-1 for Zn, 21.2 - 93.6 mg.g^-1 for Cr, 5.7 - 45.8 mg.g^-1 for Ni, 1.64 - 3.80 mg.g^-1 for As, and 0.104 - 0.493 mg.g^-1 for Hg. The levels found in the present study are similar to data from other marine. 2001-01-01T00:00:00Z http://hdl.handle.net/20.500.12066/4383 Geotrophic and drift current in the South China Sea, Area IV: Vietnamese waters Van Ninh, Pham; Quynh, Do Ngoc; Van Lanh, Vo; Lien, Nguyen Thi Viet The water circulation in area IV was calculated by 2 methods. The circulation for the area where water depth exceeded 600m was calculated by the geostrophic balance method. In a shallow water area effect of wind absolutely surpasses geostrophic balance, so wind induced drift current is greater than geostrophic current many times. So, for the whole area (shallow deep) the drift current was calculated by two-dimensional nonlinear shallow water equation based on typical monsoon fields. The results of 2 methods showed common picture of the circulation with divergence and convergence changing by season. 2001-01-01T00:00:00Z