Wetlands modeling

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. 

Rousseau, D.P.L., Vanrolleghem, P.A., and De Pauw, N., Model-based design of horizontal subsurface flow constructed treatment wetlands A review, Water Research, 38, 1484-1493, 2004. 

Zhang, X., Liu, P., Yang, Y., and Chen, W., Phytoremediation of urban wastewater by model wetlands with ornamental hydrophytes, Journal of Environmental Sciences, 19, 902-909, 2007. 

Alvord, H.H. and R.H. Kadlec. 1996. Atrazine fate and transport in the Des Plaines wetlands. Ecol. Model. 90 97-107. 

Meng, F., Arp, P., Sangster, A., Brun, G.I., Rencz, A., Hall, G., Holmes, J., Lean, D., Clair, T. 2005. Modeling dissolved organic carbon, total and methyl mercury in Kejimkujik freshwaters. In Mercury Cycling in a Wetland Dominated Ecosystem A Multidisciplinary Study. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 267-284. 

As we have seen in Section 6.4, wetland rice is particularly efficient at absorbing N03. Kirk and Kronzucker (2000) developed a model to calculate the extent to which rice growing in submerged soil can capture NOs formed in the rhizosphere before it diffuses away and is denitrified in the soil bulk. The model allows for the following processes. 

This chapter has shown the complexity of the chemical and biological processes around wetland plant roots and the effects of the extreme electrochemical gradient between the root surface and surrounding soil. Models of nutrient uptake by plants in aerobic soil, which treat the root as a simple sink to which nutrients are delivered by mass flow and diffusion but the root not otherwise influencing the surrounding soil, work reasonably well for the more soluble nutrient ions. However, the complexity of the wetland root environment is such that such models are inadequate and more elaborate treatments are necessary. Many of the mechanisms involved are still poorly defined and speculative, but their potential significance is clear. 

Table 8.3 Global distributions of CH4 emissions (Tg CH4year ) calculated using inverse modelling. In Scenario A rice contributes 50-80Tg year and in B 15-30Tg year the net contribution of natural wetlands and ricelands is constant...

Armstrong W, Armstrong J, Beckett PM. 1990. Measurement and modelling of oxygen release from roots of Phragmites australis. In Cooper SC, Findlater BC, eds. The Use of Constructed Wetlands in Water Pollution Control. Oxford Pergamon, 41-52. 

Armstrong W, Cousins D, Armstrong J, Turner DW, Beckett PM. 2000. Oxygen distribution in wetland plant roots and permeability barriers to gas-exchange with the rhizosphere a microelectrode and modelling study with Phragmites australis. Annals of Botany 86 687-703. 

Tremaine et al. (1994) conducted pilot-scale studies to compare the effect of a suspended-growth reactor and a fixed-film bioreactor with a constructed wetland environment in removing creosote-PAHs from contaminated water recovered from a wood-preserving facility. Mass balanced chemical analysis of 5 PAHs used as model constituents of creosote showed that the wetland yielded between 20 and 84% removal, whereas the fixed-film reactor yielded 90 to 99% PAH removal. Biodegradation accounted for >99% of the losses observed in the fixed-film reactor, but only 1-55% of the compounds removed in the artificial wetland was attributable to biodegradation. Again, physical sorption of PAHs, especially HMW PAHs, was found to be significant. 

Buddhawong, S., Kuschk, P Mattusch, J. et al. (2005) Removal of arsenic and zinc using different laboratory model wetland systems. Engineering in Life Sciences, 5(3), 247-52. 

Because exposure occurs where receptors co-occur with or contact stressors in the environment, characterizing the spatial and temporal distribution of a stressor is a necessary precursor to estimating exposure. The stressor s spatial and temporal distribution in the environment is described by evaluating the pathways that stressors take from the source as well as the formation and subsequent distribution of secondary stressors. For chemical stressors, the evaluation of pathways usually follows the type of transport and fate modeling described in Chapter 27. Some physical stressors such as sedimentation also can be modeled, but other physical stressors require no modeling because they eliminate entire ecosystems or portions of them, such as when a wetland is filled, a resource is harvested, or an area is flooded. 

FIGURE 3 Proportion of lake area accounted for by littoral zones for the world s lakes (a), and the proportion of extracellular (ER) dissolved organic matter inputs derived from littoral zones (b see text for description of the model). The solid lines illustrate relationships in which lake boundaries are restricted to littoral and pelagic zones and the dotted lines illustrate patterns in which lake boundaries are expanded to include adjacent wetlands. In (b), the two sets of lines illustrate the range in the contribution of littoral zones to total lake ER with variation in rates of primary production for phytoplankton (0.1-2.0 kg organic matter m-2 yr 1) and macrophytes (0.6-3.8 kg organic matter nT2 yr 1). The relationship between littoral zone area and number of lakes is from Wetzel (1983). 

In many instances, the materials or plant substances that prove to be allelopathic in laboratory or pot culture experiments may not elucidate similar magnitude of allelopathic response on aquatic weeds in aquatic environments, watersheds, or wetlands. Hence, it is imperative to confirm plant products for their allelopathic potential on weeds in their own natural habitat. A search was made on allelopathic plant products for use in water hyacinth control programs at Department of Agronomy, Annamalai University. Ten of 55 different plant products that showed allelopathic suppression of water hyacinth within 48 h of treatment were selected and tested for their efficacy in natural habitats. The field testing was done in a two tier model. First, the ten plant products were tested in microponds (simulated natural habitat). Second, the plant products that confirmed to be allelopathic in microponds were further evaluated in natural watersheds. 

Officer, C.B. (1980) Box models revisted. In Estuarine and Wetland Processes with Emphasis on Modeling (Hamilton, P., and MacDonald, K.B., eds.), pp. 65-114, Plenum Press, New York. 

Chimner, R. A., Cooper, D. J. Parton, W. J. (2002). Modelling carbon accumulation in Rocky Mountain fens. Wetlands, 22, 100-10. 

Rybczyk, J., Garson, G., and Day, J. (1996). Nutrient enrichment and decomposition in wetland ecosystems Models analyses and effects. Curr. Top. Wetland Biogeochem. 2, 52—72. 

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