Tropical sediments

One aspect of sedimentary 7 8 chlorite formation which is particularly interesting is the fact that these minerals are never found forming at depths greater than 80 meters in recent sediments. Porrenga (1967b) thinks that they are characteristic of tropical sediments and their formation is thus temperature dependent. This appears invalid since they are known to form in recent sediments in a Scottish loch (Rohrlich, e al.. 1969). Nevertheless there does seem to be a bathymetric control on their occurrence. This is probably not a pressure effect but more likely some sort of factor related to organic activity in the sediments which is controlled by the biotic factors of sea depth, temperature, nutrients, etc. 

Isomarinone (1679), an isomer of the previously known marinone (7), was isolated from the same tropical sediment bacterium (1638). Another marine-derived bacterium related to the genus Streptomyces has yielded the novel azamerone (1680) (1639). The British Columbian medicinal plant Moneses uniflora contains the antibiotic 8-chlorochimaphilin (1681), which is more active than chimaphilin (1640). Sesame roots (Sesamum indicum) have yielded the red chlorinated naphthoquinone chlorosesamone (1682) (1641). Cultures of Streptomyces strain LL-A9227 produce chloroquinocin (1683), which has some antibacterial activity against Gram-positive bacteria (1642). The two xestoquinones 1684 and 1685 were characterized from the Philippino sponge Xestospongia sp., and display topoisomerase II activity (1643). 

Peck, M.R., Klessa, D.A. and Baird, D.J. (2002) A tropical sediment toxicity test using the dipteran Chironomus crassiforceps to test metal bioavailability with sediment pH change in tropical acid-sulfate sediments, Environmental Toxicology and Chemistry 21 (4), 720-728. 

Dunne, T. (1979). Sediment yield and land use in tropical catchments. /. Hydrol. 42, 281-300. 

Earth (Li, 1976). The high denudation rate is a reflection of the poorly lithifled, highly tecton-ized nature of the sedimentary rocks that compose the island. Sediment-yield data compiled by Milliman and Meade (1983) and Milliman and Syvitski (1992) indicate that island arcs and mountain belts in the tropical and subtropical west Pacific may contribute as more than 22% of all solid material discharged by rivers into the ocean. Furthermore, the tropical mountainous areas in southeast Asia and India may contribute another 33%. 

Irion, G. (1984). Sedimentation and sediments of Amazonian rivers and evolution of the Amazonian landscape since Pliocene times. In "The Amazon, Limnology and Landscape Ecology of a Mighty Tropical River and its Basin" (H. Sioli, ed.), pp. 201-214. Dr. W. Junk Publishers, The Hague, The Netherlands. 

Koehnken, L. (1990). The composition of fine-grained weathering products in a large tropical river system, and the transport of metals in fine-grained sediments in a temperate estuary, Ph.D. thesis, Princeton University, Department of Geological and Geophysical Sciences. 

Martin JM, Nijampurkar V, Salvation F (1978b) Uranium anti Thorium isotope behavior in estuarine systems. In Biogeochemistry of estuarine sediments. UNESCO, p 111-127 Mathieu D, Bemat M, Nahon D (1995) Short-lived U and Th isotope distribution in a tropical laterite derived from Granite (Pitinga river basin, Amazoitia, Brazil) application to assessment of weathering rate. Earth Planet Sci Lett 136 703-714... 

Guimaraes, J.R.D., Meili, M., Hylander, L.D., Castro e Silva, E., Roulet, M., Mauro, J.B.N., and Lemos, R.M.A., Mercury net methylation in five tropical flood plain regions of Brazil High in the root zone of floating macrophyte mats but low in surface sediments and flooded soils, Science of the Total Environment, 261 (1-3), 99-107, 2000. 

The EUSES environment is represented as a set of nested scales. The local scale is nested into the regional scale which is nested in the continental scale. The continental scale is nested into the moderate climate zone, which has two adjacent zones, an arctic and a tropic zone, respectively. All the scales are divided into boxes (environmental compartments). The boxes of all scales include at least air, soil, water, and sediment compartments. 

Despite problems with its use, DDT has saved countless lives in regions where malaria is endemic. Tropical Asian countries, which have discontinued its use, have seen malaria incidence increase India and some other countries still cling to use of DDT because it is cheap and effective. Tissue levels in wildlife of the regions where DDT was banned began to decline about 10 years after DDT was banned however, DDT and its metabolites may routinely be detected in soil and bottom sediments even today (Galiulin and Bashkin, 1996). Over a long time, DDT is subject to atmospheric migration, for example from India to the Asian polar zone, to contribute to the contamination of local ecosystems as well. 

Rummasak, T., Towprayoon, S., Bashin, V. (2002). Chemical Properties of Mangrove Sediments in Relation to Sulfur Dynamics. Tropics, 12(1), 43-57. 

Fig. 9.6 Climate records from the Vostok Antarctic ice core and the tropical carbonate seafloor sediment core V19-30 (Shakleton, N. J. and Pisais, N. Am. Geophys. Union, Geophys. Mon. 3, 303 (1985))...

Of particular concern are the impacts of seawater acidification on biocalcification and the burial rates of sedimentary carbon. Carbonate ion concentrations in the surface waters have already declined by 16%. Thus, it is not surprising that the abundance of tropical/subtropic planktonic foraminiferan species appears to have declined since the 1960s. This information was obtained by studying the rapidly accumulating sediments of the Santa Barbara Basins off the coast of California. 

Calcitic ooids Nodules of calcite that are less than 2 mm in diameter. They are commonly found in and on the sediments of shallow tropical seas. 

Oolite A hydrogenous precipitate commonly found in carbonate sediments of continental shelves located in the tropics. They are composed primarily of calcium carbonate and are thought to be an abiogenic precipitate formed from warm seawater supersaturated with respect to calcite and aragonite. 

Many submerged soils are developed in recent in alluvium and are often young or only weakly weathered (Section 1.3). The overall composition of the clay fraction is therefore often close to that of the parent sediment. Hence the following generalizations can be made for rice soils in the humid tropical lowlands (Kyuma, 1978 Binkman, 1985)... 

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