Wetland

Wetlands have the potential to remove metals from AD by metal adsorption on ferric oxyhydroxides, metal uptake by plant and algae, metal complexation by organic materials, and metal precipitation as oxides, oxyhydroxides, or sulfides. However, only metal precipitation as either oxides or sulfides has long-term metal-removal potential (Evangelou, 1995b). 

The data in Table 12.4 provide a summary of chemical and physical characteristics of influent and effluent water from constructed wetlands at Tennessee Valley Authority (TVA) facilities. Water quality generally improved in all cases, and most met the state effluent guidelines for total Fe 3.0 mg L 1, total Mn 2.0 mg L-1, pH 6.0-9.0, and nonfilterable residues (NFR) 35.0 mg L 1. These data also indicate that wetlands are more effective in the removal of Fe2+ than Mn2+. 

Wetlands, at times, may be a poor environment for the formation of metal oxides and/or oxyhydroxides because of the typically low redox potential (Eh). Optimizing the activity of sulfate-reducing bacteria (e.g., desulfovibrio) in the anaerobic zone would be a more effective way of removing metals and sulfates from AD (Kleinmann, 1989). These sulfate-reducing bacteria consume acidity and most of the hydrogen sulfide they produce reacts with heavy metals to create insoluble precipitates. The reactions are shown below  

Laboratory studies have shown that trace metals such as Co, Cu, Cd, Ni, Pb, and Zn can be removed as sulfides (Staub and Cohen, 1992 Eger, 1992 Hammock and Edenborn, 1991). 

Coastal estuary wetlands are susceptible to arsenic contamination because of hurricanes or other storms. Sediments deposited in 2005 by Hurricane Katrina in New Orleans, Louisiana, USA, were often contaminated with arsenic that exceeded human health standards (Cobb et al., 2006). The arsenic may have originated from runoff containing lawn herbicide residues and the leachates of wood treated with CCA preservatives (Cobb et al, 2006), 4576. 

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Can the contaminant be brought to a reactor or constmcted wetland where biological systems, microbial or plant, can extract and immobilize the contaminant ... 

R. H. Kadlec and R. L. Knight, Treatment Wetlands, Lewis PubUshers, Boca Raton, Fla., 1996. 

R. W. Howarth, J. W. Stewart, and M. V. Ivanov, Sulfur Cjcling on the Continents Wetlands, Terrestrial Ecosjstems and Associated WaterBodies, Scientific Committee on Problems of the Environment Series, John Wiley Sons, Inc., New York, 1992. 

Landfills in wet areas. Because of the problems associated with contamination of local groundwaters, the development of odors, and structural stabihty, landfills must be avoided in wetlands. If wet areas such as ponds, pits, or quarries must be used as landfill sites, special provisions must be made to contain or ehminate the movement of leachate and gases from completed cells. Usually this is accomplished by first draining the site and then lining the bottom with a clay liner or other appropriate sealants. If a clay uner is used, it is important to continue operation of the drainage facility until the site is filled to avoid the creation of uplift pressures that could cause the liner to rupture from heaving. 

In addition to the use of techniques to reduce nutrient run-off at source, entry of nutrients to lakes can be reduced by using pre-lake techniques. These include the use of artificial wetlands on inflow streams, the use of iron salt treatment in pre-lake lagoons or by installing treatment plants to remove phosphorus. 

Sensitive ecological areas, wetlands, floodplains, wildlife refuges... 

Minimize impact upon adjacent surface waters and wetlands... 

Ecological impact of operations. This includes the loss of biodiversity, loss of species, loss of wetlands and restoration of land and waters to environmentally beneficial use. This requires setting a base inventory and then periodically updating it. 

Dredging or filling of wetlands improperly and/or witliout a permit... 

Manage the Adirondack and Catskill forest preserves and recreational facilities, including campsites and the Belleayre Mountain ski center Protect tidal and freshwater wetlands and flood plains... 

Sources of tliis information include site descriptions mid data from the preliminary assessment (PA), site inspection (SI), and remedial investigation (RI) reports. Other sources include local soil sur eys, wetland maps, aerial photographs, and reports by the National Oceanograpliic and Atmospheric Association (NOAA) and tlie U.S. Geological Sur ey (USGS). One cmi also consult with appropriate tecluiical e.xperts (e.g., hydrogeologists, air modelers) as needed to cluuacterize tlie site. 

Born in 1907 to Robert and Maria Carson, Rachel developed her admiration for nature in the woods and wetlands of her home in the Allegheny hills of western Pennsylvania, Her mother nurtured this interest with nature-study books. Simultaneously, Rachel cultivated her desire to write, publishing her first piece at eleven in the children s magazine St. Nicholas. 

Controlling methane release from wetland, rice paddies and gaseous emissions from animals is more problematic. The release from rice paddies and wet lands is slow, intermittent and takes place over a wide geographic area, and thus very difficult to control. Gaseous emissions from agricultural animals contribute to atmospheric accumulation of methane due to fermentative digestion that produces methane in... 

A balanced landscape needs waterbodies. These should be designed to have shallow margins to provide the appropriate conditions for wetland planting which, in turn, provide the balanced habitats for a rich wetland ecosystem. 

Dead vegetation also afreets the global carbon cycle. Dead organic matter decomposes, releasing carbon dioxide to the atmosphere. Rates of decomposition vary with material, location, and climate. Non-woody organic matter decomposes rapidly woody organic matter slowly. Decomposition tends to occur faster at the soil surface than below. Decomposition is relatively fast in warm moist climates. In cold climates and in wetlands, decomposition is so slow that there is a net increase of stored carbon in the soil and organic soils called, "histosols, are formed. 

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