Environment floodplain

The travel time for suspended load is controlled by the flow velocity and the distance to the basin outlet. Flow velocities do not change much downstream in a typical river system (Leopold, 1953) and typically range from 0.1 to several m/s. Hence, suspended load should be able to travel at least 10 to 100 km per day and the travel time for suspended sediment to traverse even the longest rivers in the world should be less than a season. Although some of the suspended load will be deposited in floodplains, the component of the suspended load that does not get sequestered in terrestrial depositional environments is delivered almost as fast as the water that it flows in. Bedload travels much more slowly. In mountain drainage basins, the velocity of individual bedload clasts is on the... 

Electricity is a fundamental requirement for economic growth, and hydro-electric power is often thought to be environmentally benign. However, the constraction and operation of many hydro-power dams have had significant negative impacts on the environment and raral economies. Reduced downstream flooding has destroyed fisheries and starved the floodplain soils of moisture and nutrients (Acreman, 1996). 

Field Studies. We have attempted to compare the relative availability of actinides to small mammals living in contaminated environments near ORNL. Shrews, rats and mice have been collected from a 30 year old contaminated floodplain forest ecosystem ( ). Cotton rats (Sigmodon hispidus) have been collected from the banks of a former liquid radioactive waste pond which contains Pu, Am and Cu in sediments and shoreline vegetation. Analyses were performed by isotope dilution mass spectrometry (U, Th and Pu) or by alpha spectrometry (Pu, Am and Cm). 

De Vivo, B., Somma, R., Ayuso, R. A., Calderoni, G., Lima, A., Pagliuca, S., and Sava, A. (2001). Pb isotopes and toxic metals in floodplain and stream sediments from the Volturno basin, Italy. Environ. Geol. 41, 101-112. 

More than 1 million square kilometers of the Amazon basin may be classified as floodplain, wetland, or lake. These environments range from narrow, sporadically flooded lowlands bordering streams to massive, regularly flooded plains bordering the basin s largest rivers. Nearly 9000 lakes,... 

Junk, W. J., and K. Furch. 1991. Nutrient dynamics in Amazonian floodplains decomposition of herbaceous plants in aquatic and terrestrial environments. Verhandlungen Intemation2tl Vereinigen Limnologie 24 2080-2084. 

Roosevelt, A. C. 1999. Twelve thousand years of human-environment interaaion in the Amazon floodplain. Advances in Economic Botany 13 371-392. 

Organic carbon is lost from Amazon flood-plain lakes by permanent burial, emission as CO2 and CH4 to the atmosphere or export to the river. Sufficient data are now available to estimate most of these losses. Methane is produced predominantly in anoxic environments associated with flooded habitats. Methane emission rates have been estimated in a variety of habitats and sites along the central Amazon floodplain (Devol et al. 1988, 1990, 1994, Crill et al. 1988, Bartlett et al. 1988, 1990, Wassmann et al. 1992, Wassmann and Thein 1994, Engle and Melack 2000). The average emission rates encountered in aquatic macrophyte beds, flooded forest and open water, including... 

As is evident throughout our review, a much wider diversity of lakes and floodplain environments must receive the attention of limnologists. Additional measurements of periphyton productivity, of burial of C, N, and P in sediments, of nitrogen fixation and denitrification, and of carbon dioxide emissions, especially, are needed. A further challenge is to investigate biogeochemical processes in the ATTZ, and to link these processes with the whole floodplain ecosystem. 

Melack, J. M., S. J. Sippel, D. M. Valeriano, and T. R. Fisher. 1992. Environmental conditions and change on the Amazon floodplain analysis with remotely sensed imagery, pp 377-387. 24th International Symposium on Renxrte Sensing of the Environment. ERIM, Ann Arbor, Michigan. 

There is already in progress a rise of sea-level (see Revelle s chapter) due to glacial melting and the warming and hence expansion of the ocean water column. The rise over the past century is believed to be about 15 cm, with some uncertainty. A further rise of 70-100 cm is probable in the next century from the same processes. Much larger rises are possible over the next few centuries if the effect persists. In this paper emphasis is placed on the next century, and the sea-level rise is hence not stressed, though its effects may well be serious in estuarine, deltaic and floodplain environments. 

Garten, C.T. Jr., Bondietti, E.A. and Walker, R.L., Comparative uptake of uranium, thorium, and plutonium by biota inhabiting a contaminated Tennessee floodplain, J. Environ. Qual. 10 (1981) 207-210. 

A) Horizontal beds forming a transition from floodplain deposits to a palustro-lacustrine environment and lacustrine limestones. (B) Lacustrine deposits with stromatolitic bioherms (C) Palustrine limestone with abundant root traces. (D) Lacustrine bottom-set sediments enriched in organic matter and showing thin turbiditic layers. (E) Palustrine limestone with a well developed palaeosol at the top. (F) Various types of crushed shell fragments in a lacustrine mud. (G) Lacustrine bioclastic and oolitic sand deposited near a shore. 

The results of Table V illustrate that only a small fraction of Pu from the floodplain site is assimilated by native and cultured plants. The large majority (>99%) still remains assoc-ciated with soil. Concentration ratios of 10-3 indicate that plants are not able to extract Pu effectively from soil of this contaminated environment. 

From new data and from evaluation of published information, it appears that the magnitudes of uptake of actinide elements by plants from contaminated soil generally are less than the value used in the assessment of radiological impact for the LMFBR environmental assessment. The CR value of approximately 10-1 used in the impact assessment exceeds most observed values for Pu (Fig. 3), and appears conservative for incorporation into foods by the root pathway. Even after 30 years of residence time in the biologically active environment of the Oak Ridge floodplain, greater than 99% of the Pu in this ecosystem remains associated with the soil. The observed CR value is 10-3. For this time frame, there is no evidence that ecological or soil processes will cause the soil-to-plant transfer of Pu to approach the 10-1 value used in the LMFBR... 

Availability of actinide elements to biota may be related to certain chemical species of the elements, and the environmental behavior of these species is not understood. Based on studies of chemical species of Pu in typical environmental media, and considering the magnitude of Pu uptake by vegetation growing in a floodplain contaminated 30 years ago, one would not expect to see great increases in availability to biota after extended residence times in the environment. 

---