Fluviale

For example, the many deepwater fields located in the Gulf of Mexico are of Tertiary age and are comprised of complex sand bodies which were deposited in a deepwater turbidite sequence. The BP Prudhoe Bay sandstone reservoir in Alaska is of Triassic/ Cretaceous age and was deposited by a large shallow water fluvial-alluvial fan delta system. The Saudi Arabian Ghawar limestone reservoir is of Jurassic age and was deposited in a warm, shallow marine sea. Although these reservoirs were deposited in very different depositional environments they all contain producible accumulations of hydrocarbons, though the fraction of recoverable oil varies. In fact, these three fields are some of the largest in the world, containing over 12 billion barrels of oil each ... 

Surface water enrichment is the result of aeolian and fluvial inputs, which are thought to be the most important sources of Th to the ocean. Thorinm-232 has been proposed as a link between the radiogenic thorium isotopes and trace metals and anthropogenic pollutants. " While the pathways are very different for the radiogenic thorium isotopes, Th is delivered to the ocean in a fashion similar to many pollutants and trace metals. For example, Guo et found Th distributions in the Gulf of Mexico and off Cape Hatteras in the North Atlantic Ocean agreed well with the general distribution pattern of aluminum. 

Schumm, S. A. (1977). "The Fluvial System." Wiley Sons, New York. 

DeCelles, P. G. and Hertel, F. (1989). Petrology of fluvial sands from the Amazonian foreland basin. 

Edmond, J. M., Palmer, M. R., Measures, C. I. Grant, B., and Stallard, R. F. (1995). The fluvial geochemistry and denudation rate of the Guayana Shield in Venezuela, Colombia, and Brazil. Geochim. Cosmochim. Acta 59,3301-3325. 

Johnsson, M. J., Stallard, R. F., and Lundberg, N. (1991). Controls on the composition of fluvial sands from a tropical weathering environment Sands of the Orinoco River drainage basin, Venezuela and Colombia. Geol. Soc. Am. Bull. 103,1622-1647. 

Abstract In most of the world s watercourses, dramatic modifications have occurred as a consequence of intensive use by human societies. The simplification of the channel network and the alteration of water fluxes have an impact upon the capacity of fluvial systems to recover from disturbances, because of their irreversible consequences. However, human impacts on river hydrology, such as those that derive from regulating their flow or by affecting their channel geomorphology, affect the functional organisation of streams, as well as the ecosystem services that derive from them, and lead to the simplification and impoverishment of these ecosystems. 

Pinay G, Clement JC, Naiman RJ (2002) Basic principles and ecological consequences of changing water regimes on nitrogen cycling in fluvial systems. Environ Manage 30 481 91... 

Pinay G, Decamps H, Chauvet E et al (1990) Eunctions of ecotones in fluvial systems. In Naiman RJ, Decamps H (eds) The ecology and management of aquatic-terrestrial ecotones. Parthenon, Camforth, UK, pp 141-169... 

Metal Ecotoxicology in Fluvial Biofilms Potential Influence of Water Scarcity... 

Keywords Community ecotoxicology, Fluvial biofilm. Metal pollution. Nutrients,... 

Fluvial biofilms (also known as phytobenthos or periphyton) are attached communities consisting of bacteria, algae and fungi embedded within a polysaccharide matrix [20]. In rivers, these communities are the first to interact with... 

Several factors can influence metal uptake by stream autotrophic biofllms in fluvial systems. These include chemical factors (pH, saUnity, phosphate concentration) which affect metal bioavailabiHty by either altering the speciation of the metal or by complexing it at the biotilm s matrix and cell surfaces [18, 40], and also other biological and physical factors. 

Table 1 Summary of metal concentrations (in )ig of total metal concentration) causing toxicity on fluvial biofilms (in terms of effective concentrations EC50) after acute exposure (of few hours of exposure) and chronic exposure (of several weeks of exposure)...

Cu Acute toxicity on biofilms EC50 ( C) 20-50 (spring) 100-350 (summer) EC50 (Y) 230 (low P) 718 (highP) EC50 (Fo) 56-92 (low P) 196-206 (high P) Field samples Ter river" Fluvial microcosms Field samples"... 

Chronic effects on biofilms EC50 6-25 indirect effects EC50 50-2500 direct effects Changed algal species >50 Fluvial microcosms (low P) " Experimental stream ... 

Chronic effects on biofilms 10 effects on settlement 100 biomass, change spp. Fluvial microcosms (high P)" °... 

Table 2 Fate and effects of metals in a stream receiving a point-source of metals (upper part of the table) or diffuse input via urban runoff (lower part of the table). Summary of the expected influence of four different hydrological situations base-flow in a rainy period a flood after a rainy period low-flow after a long period of low rainfall (water scarcity) and a flood produced after this drought. Metal concentration (M) metal retention efficiency (measured on the basis of the nutrient spiraling concept) exposure (dose and duration) bioaccumulation (in fluvial biofilms) and metal sensitivity (of biofihns)...

Highlights the worst scenario in terms of metal pollution effects on fluvial biofilms... 

The first case is based on a hypothetical stream receiving a metal-poUuted source (for instance the outlet of a metal factory). In this case, metal concentration is expected to be driven by dilution, being higher under low-flow than under base-flow conditions and minimum during floods. Metal accumulation is expected to be maximum under low-flow conditions and proportional to the duration of this water scarcity situation. Chronic exposure will lead to community adaptation, which is often related to changes in species composition. Metals will therefore be bioaccumulated in fluvial biofihns and transferred to higher trophic levels in the fluvial food web. 

Serra A, Guasch H, Corcoll N (2009) Copper accumulation and toxicity in fluvial periphyton the influence of exposure history. Chemosphere 74 633... 

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