World-Wide Delivery of River Sediment to the Oceans
New data and new estimates from old data show that rivers with large sediment loads (annual discharges greater than about tons) contribute about tons of suspended sediment to the ocean yearly. Extrapolating available data for all drainage basins, the total suspended sediment delivered by all rivers to the oceans is about tons annually; bedload and flood discharges may account for an additional tons. About 70% of this total is derived from southern Asia and the larger islands in the Pacific and Indian Oceans, where sediment yields are much greater than for other drainage basins. [1]
River-Sediment Inputs to Major Deltas
River sediments are distributed unevenly in space and time, and they are markedly susceptible to human influences. Half the world’s river sediment is derived from the Himalayan region and its environs. Most of the remainder is derived from other tectonically active regions such as the western Pacific islands, the Andes, and southern Alaska. River-sediment loads are variable at many time scales: seasonal, annual, decadal, and longer. The storage of sediment in river systems confounds our ability to predict the delivery of sediment to coastal zones. Natural river-sediment loads are increased by deforestation and crop farming, and decreased by dams and reservoirs. [2]
Transport and deposition of river sediment in the Changjiang estuary and adjacent continental shelf
Hydrographic observations, suspended-sediment measurements, and historical data indicate transport paths and sinks for sediment within the Changjiang estuary and adjacent shelf. Most of the sediment transported by the Changjiang to the ocean is carried through the North Channel of the South Branch. Sediment transport is directly related to river stage, but tidal phase (spring vs neap tides) also plays an important role. An estimated 40% of the sediment load in the river is deposited in the estuary, mostly in and seaward of the South Channel. The remaining sediment is deposited directly offshore during flood seasons, but much is resuspended and carried southward by subsequent winter storms. [3]
Speciation of Some Heavy Metals in Sediments of the Pennington River, Bayelsa State, Nigeria
The total heavy metal concentrations of some environmentally toxic metals in sediments of the Pennington River System, Bayelsa state, Nigeria was examined. The concentrations of heavy metals in each fraction were determined using a ANALYST 400 Perkin-Elmer AAS. The mean concentrations (mg/kg) for the six metals in dry season sediment samples were: 0.14±0.17(As), 0.39±0.55(Co), 2.43±5.06(Cu), 26.82±22.19(Fe), 0.69±1.10(Pb), and 1.22±1.19(Zn), while the mean metal concentrations (mg/kg) in wet season samples were:0.11±0.18(As),0.37±0.6(Co), 2.07±4.35(Cu), 26.65±24.79(Fe), 0.61±1.08(Pb), and 1.11±1.00(Zn) respectively. Speciation study applying the five-stage sequential extraction scheme revealed that As, Co, and Pb in sediment prevails mostly in exchangeable fraction. Cu and Zn were more prevalent in residual fraction, while Fe was found more in residual and Fe/Mn-Oxide fractions. In an attempt to infer anthropogenic input from natural input, comparison with sediment quality guideline (SQGs) and ecotoxicological sense of heavy metal contamination was employed. The concentration of the studied heavy metals in Pennington River System does not pose a threat to the sediment dwelling fauna and anyone who consumes aquatic animals, particularly fish, from the Pennington River. According to SQGs, the studied heavy metals of the Pennington River sediments were under the category of non-polluted. [4]
Characterization and Sources of Aliphatic Hydrocarbons of the Sediments of River Oluwa at Agbabu Bitumen Deposit Area, Western Nigeria
Aims: This research is aimed at determination of the distribution, concentrations, sources and origins of petroleum hydrocarbon in sediment. Study Design: River sediment samples were collected from five sampling sites from the sediments of River Oluwa at Agbabu bitumen deposit area and analyzed for n-alkanes content. Place and Duration of Study: Samples were collected from Agbabu bitumen deposit area, Western Nigeria, in years 2008 and 2009. Methodology: Analysis was carried out using gas-chromatography flame ionization detector. Diagnostic parameters used in identifying and estimating the origins of n- alkanes in the study area included Carbon Preference Index (CPI), Average Carbon Chain (ACL) and %Plant Wax Contribution. [5]
Reference
[1] Milliman, J.D. and Meade, R.H., 1983. World-wide delivery of river sediment to the oceans. The Journal of Geology, 91(1), pp.1-21.
[2] Meade, R.H., 1996. River-sediment inputs to major deltas. In Sea-level rise and coastal subsidence (pp. 63-85). Springer, Dordrecht.
[3] Milliman, J.D., Huang-Ting, S., Zuo-Sheng, Y. and Mead, R.H., 1985. Transport and deposition of river sediment in the Changjiang estuary and adjacent continental shelf. Continental Shelf Research, 4(1-2), pp.37-45.
[4] Elijah, L.K., Junior, H.M. and Ibuteme, S.A., 2015. Speciation of some heavy metals in sediments of the Pennington River, Bayelsa State, Nigeria. Chemical Science International Journal, pp.238-246.
[5] Fagbote, O.E. and Olanipekun, E.O., 2013. Characterization and sources of aliphatic hydrocarbons of the sediments of River Oluwa at Agbabu Bitumen deposit area, Western Nigeria. Journal of Scientific Research and Reports, pp.228-248.