Terrestrial model

Data Structures. Inspection of the unit simulation equation (Equation 7) indicates the kinds of input data required by aquatic fate codes. These data can be classified as chemical, environmental, and loading data sets. The chemical data set , which are composed of the chemical reactivity and speciation data, can be developed from laboratory investigations. The environmental data, representing the driving forces that constrain the expression of chemical properties in real systems, can be obtained from site-specific limnological field investigations or as summary data sets developed from literature surveys. Allochthonous chemical loadings can be developed as worst-case estimates, via the outputs of terrestrial models, or, when appropriate, via direct field measurement. 

An ecosystem can be thought of as a representative segment or model of the environment in which one is interested. Three such model ecosystems will be discussed (Figures 1 and 2). A terrestrial model, a model pond, and a model ecosystem, which combines the first two models, are described in terms of equilibrium schemes and compartmental parameters. The selection of a particular model will depend on the questions asked regarding the chemical. For example, if one is interested in the partitioning behavior of a soil-applied pesticide the terrestrial model would be employed. The model pond would be selected for aquatic partitioning questions and the model ecosystem would be employed if overall environmental distribution is considered. 

Therefore, the percent of chemical in the water can be solved for, and having this value the percent of chemical in each compartment can be subsequently calculated. Equations for the terrestrial model and the model pond are solved similarly. Also, the sizes of the compartments can be changed to represent different types of environmental conditions. 

Migliore, L., G. Brambilla, P. Casoria, C. Civitareale, S. Cozzolino, and L. Gaudio (1996). Effect of sulphadimethoxine on barley Hordeum distichum L., Poaceae, LiUopsida) in laboratory terrestrial models. Agriculture, Ecosystem, and Environment 60 121-128. 

Virtanen, M., Hattula, M.L., Arstila, A.U. (1979) Behavior and fate of 4-chloro-2-methylphenoxyacetic acid (MCPA) and 2,6-dichloro-o-cresol as studied in an aquatic-terrestrial model ecosystem. Chemosphere 8, 431. 

Semifield tests, sensu stricto, are experimental ecosystems that run under fieldlike outdoor conditions. Aquatic micro- and mesocosms have been widely used in assessing effects of substances under semilield conditions (Stephenson et al. 1986 Arnold et al. 1991 Hill et al. 1994 van den Brink et al. 1996 Kennedy et al. 1999 van den Brink and Ter Braak 1999 Culp et al. 2000a, 2000b Sibley et al. 2001a, 2001b, and many others). Also, terrestrial model ecosystems (TMEs) have been developed that are, in contrast to the use of field plots, separated from their source site and run under laboratory conditions (Knacker et al. 2004). Because experience is limited, they will be considered here only marginally. 

Knacker T, van Gestel CAM, Jones SE, Soares AMVM, SchallnaB H-J, Forster B, Edwards CA. 2004. Ring-testing and field-validation of a terrestrial model ecosystem (TME) an instrument for testing potentially harmful substances conceptual approach and study design. Ecotoxicol 13 9-27. 

The advantage of such models is that they allow the effects of different mechanisms to be distinguished. However, they may not include all of the important processes affecting changes in carbon stocks. To date, e.g., few process-based terrestrial models have included changes in land use. 

In contrast to Earth, Martian Xe apparently did not evolve from a U-Xe progenitor. Modeling derivation of primordial Xe composition on Mars is based on analyses of atmospheric gases trapped in glassy phases of SNC meteorites (Swindle 2002, this volume). Present ambiguities in this data base are such that two different solar-system Xe compositions, carbonaceous chondrite (Cl)-Xe and SW-Xe, are possible candidates—but not U-Xe. Exclusion of U-Xe as the dominant primordial atmospheric inventory on Mars, despite the implication of the terrestrial modeling that it was a major component of the nebular gas phase, requires that accretion of Cl- or SW-Xe-rich materials from sources more localized in space or time has overwhelmed the isotopic signature of its presence. 

Romashka, as a terrestrial model, was the first NPS with a thermoelectric converter turning nuclear reactor heat into electric power. It was brought to electric power in August 1964 at the terrestrial facility of Kurchatov Institute and operated successfully about 15,000 h producing 6,100 kWh of electric power. Its basic characteristics are summarized in O Table 59.1 (Gverdtsiteli et al. 1969 Kukharkin et al. 2008). 

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