Wetlands water source

Nixon, S.W. and Lee, V., in press. Wetlands and water quality. A regional review of recent research in the United States on the role of fresh and saltwater wetlands as sources, sinks, and transformers of Nitrogen, Phosphorus and various heavy metals. Report to the Waterways Experiment Station, U.S. Army Corps of Engineers, Vicksburg, MS. 

While atrazine degradation to hydroxyatrazine was enhanced by the addition of ammonium sulfate in anaerobic wetland sediments (Chung et al., 1995), the addition of 2.0g/L of ammonium nitrate into aerobic wetland water sample reactors clearly inhibited atrazine degradation (Ro and Chung, 1995). In 15N tracer studies done with Pseudomonas strain ADP (which can use all five N atoms of atrazine as a sole N source), Bichat et al. (1997) indicated that while organic N sources had little effect on atrazine degradation, nitrate and ammonium delayed atrazine degradation. 

FIGURE 3.2 Relationship between water source and wetland vegetation. (Modified from Brinson, 1993.)... 

The hydrologic cycle governs the rate of water transfer and movement in wetlands. Water transfer also governs the removal of toxic organics from wetlands. Water enters wetlands primarily from rainfall and surface runoff from the adjacent watersheds or upland areas. Tidal waters are a major water source in coastal wetlands. Generally, over time the quantity of water leaving a wetland is compensated by water entering the system, especially in lakes, streams, and estuaries. 

The two sources of usable water are surface water, such as rivers, lakes, and wetland waters, and groundwater, which is beneath Earth s surface. Figure 11.4 shows our water resources and the flow of groundwater. About 90 billion gallons of the total water withdrawn every day is groundwater drawn from wells... 

Contaminated bed sediments exist at numerous locations in the United States and around the world. These result mainly from past indiscriminate pollution of our aquatic environments and consist of freshwater and marine bodies including streams, lakes, wetlands, and estuaries. The bed sediments contain many hydrophobic organic compounds and metal ions that in the course of time act as sources of pollutants of the overlying aqueous phase. There are a number of transport pathways by which pollutants are transferred to the aqueous phase from contaminated sediments. One of the lesser known, but potentially important, modes of transport of pollutants from bed sediments is by diffusion and advection of contaminants associated with colloidal-size dissolved macromolecules in pore water. These colloids are measured in the aqueous phase as dissolved organic compounds (DOCs). (These are defined operationally as particles with a diameter smaller than 0.45 micrometer.)... 

At whole lake scales, littoral zones are a major component of autochthonous DOM production and important sources of labile organic matter for aquatic bacteria. Of the approximately one billion lakes in the world, the littoral zone accounts for more than 95% of lake surface area in nearly 99.8% of all lakes (Wetzel, 1983 Fig. 3a). The importance of shallow waters is even more marked when the bounds of lakes are expanded to include wetlands. With such an expanded view, the littoral zone and wetlands comprise more than 95% of the area in 99.999% of all lakes (Fig. 3a). Clearly, shallow waters are a dominant feature of lentic ecosystems. 

DOM from the leaching of soils and vegetation in their catchments, fulvic acid is typically 45-65% of the DOM in wetlands fulvic acid is typically 80-90% of the DOM and in groundwaters and surface waters with mainly autochthonous microbial sources of DOM fulvic acid is typically 10-30% of the DOM (Thurman, 1985). 

Hemond, H. F. 1990. Wetlands as the source of dissolved organic carbon to surface waters. In Organic Acids in Aquatic Ecosystems (E. M. Perdue and E. T. Gjessing, Eds.), pp. 301-313. Wiley, New York, NY. 

In freshwater ecosystems, particularly streams and wetlands, biofilms account for a large portion of heterotrophic metabolism, as well as primary production (Edwards etal., 1990 see Chapter 12), acting as both sources and sinks for DOM. As the depth of the overlying water in the system increases, attached communities account for a declining share of system metabolism. 

Direction 2. A large portion, usually >90%, of the organic matter imported from allochthonous and littoral/wetland sources to these aquatic ecosystems is predominantly in dissolved or colloidal form. Although a portion of the dissolved organic compounds may aggregate and shift to a particulate and hence gravitoidal form that may sediment out of the water, most of the imported dissolved organic matter is dispersed within the water... 

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