Models ecosystem

Cole LK, Metcalf RL. 1977. Distribution of pesticides and their derivatives in the air, soil, water, and biota of physical model ecosystems. Air Pollut Control Assoc 70th Ann Meet Proc 4 1-15. 

Gile JD, Gillett JW. 1981. Transport and fate of organophosphate insecticides in a laboratory model ecosystem. J Agric Food Chem 2 616-621. 

An approach that has gained attention recently is the use of model ecosystems microcosms, mesocosms, and macrocosms for testing chemicals (Chapter 4,... 

Field experiments in model ecosystems—pools or steams... 

Santschi PH, Li YH, Adler DM, Amdurer M, Bell J, Nyffeler UP (1983) The relative mobility of natural (Th, Pb and Po) and fallout (Pu, Am, Cs) radionuclides in the coastal marine-enviromnent - results from model-ecosystems (MERL) and Narragansett Bay. Geochim Cosmochim Acta 47 201-210... 

In Mackay s development of an equilibrium model a slice of the earth is selected as a unit world or model ecosystem. Fugac-ities are calculated for each compartment of the ecosystem and the overall distribution patterns of a given chemical are predicted. 

In a similar approach McCall et al.(5) have defined a model ecosystem which represents a unit world, however, this development incorporates standard chemical equilibrium expressions into a... 

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. 

Consider the model ecosystem in Figure 2, chosen to represent a slice of the environment. The dimensions have been selected to represent a 1000 m x 1000 m square surface which contains a 10 km... 

The following expression calculates the half-life of the chemical in the model ecosystem. 

Some disadvantages have already been mentioned. These primarily appear as the model is made more complex. When degradation processes are considered at the next highest level (level II) care must be taken with interpretation of the data, in particular with less persistent compounds. 2,4-D for example, when applied to soil or a terrestrial system degrades very rapidly, much more rapidly than in water. If the half-life of the chemical was evaluated in the model ecosystem, it would be overestimated since the majority of the chemical tends to equilibrate in the water compartment. Relatively stable compounds for which transfer rates will be faster than dissipative rates can be evaluated more realistically. 

Lu, P.Y., Metcalf, R.L., Carlson, E.M. (1978) Environmental fate of five radiolabelled coal conversion by-products evaluated in a laboratory model ecosystems. Environ Health Perspect. 24, 201. 

Yu, C-C., G.M. Booth, DJ. Hansen, and J.R. Larsen. 1974. Fate of carbofuran in a model ecosystem. Jour. Agric. Food Chem. 22 431-434. 

Isensee, A.R. and G.E. Jones. 1975. Distribution of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in aquatic model ecosystem. Environ. Sci. Technol. 9 668-672. 

Ohkawa, H., R. Kikuchi, and J.S. Miyamoto. 1980. Bioaccumulation and biodegradation of the (S)-acid isomer of fenvalerate (Sumicidin ) in an aquatic model ecosystem. Jour. Pestic. Sci. 5 11-22. 

Lu, P Y., R.L. Metcalf, and L.K. Cole. 1978. The environmental fate of 14C pentachlorophenol in laboratory model ecosystems. Pages 53-63 in K.R. Rao (ed.). Pentachlorophenol Chemistry, Pharmacology, and Environmental Toxicology. Plenum Press, New York. 

Millard, E.S., E. Halfon, C.K. Minns, and C.C. Charlton. 1993. Effect of primary productivity and vertical mixing on PCB dynamics in planktonic model ecosystems. Environ. Toxicol. Chem. 12 931-946. 

Lu, P.-Y., R.L. Metcalf, N. Plummer, and D. Mandrel. 1977. The environmental fate of three carcinogens benzo-(a)-pyrene, benzidine, and vinyl chloride evaluated in laboratory model ecosystems. Arch. Environ. Contam. Toxicol. 6 129-142. 

Isensee, A.R., G.E. Jones, J.A. McCann, and F.G. Pitcher. 1979. Toxicity and fate of nine toxaphene fractions in an aquatic model ecosystem. Jour. Agric. Food Chem. 27 1041-1046. 

Nassos, P.A., J.R. Coats, R.L. Metcalf, D.D. Brown, and L.G. Hansen. 1980. Model ecosystem, toxicity, and uptake evaluation of 75Se-selenite. Bull. Environ. Contam. Toxicol. 24 752-758. 

The methodology for conducting aquatic model ecosystem studies was well established by the late 1990s. However, the use of the data in risk assessments raised a number of uncertainties regarding their interpretation and implementation [32]. Four of the uncertainties that were identified were the extent to which aquatic model ecosystem data generated in one location could be applied to another situation, the potential influence of mixtures of chemicals or stressors, whether the timing (season) of application would influence the outcome of the study, and whether differences in ecosystem properties (e.g., trophic status) might influence the results. 

Maund SJ, Van Wijngaarden R, Roessink I et al (2008) Aquatic fate and effects of lambda-cyhalothrin in model ecosystem experiments. In Gan J, Spurlock F, Hendley P et al (eds) Synthetic pyrethroids occurrence and behavior in aquatic environments. ACS Symposium Series 991, American Chemical Society, Washington DC... 

EPA. 1987a. Exposure analysis modeling system (EXAMSII). Center for Exposure Assessment Modeling, Ecosystems Research Division, National Exposure Research Laboratory, Office of Research and Development. U. S. Environmental Protection Agency. Athens, GA. 

Metcalf RL, Kapoor IP, Lu P-Y, et al. 1973. Model ecosystem studies of the environmental fate of six organochlorine pesticides. Environ Health Perspect June 35-44. 

ECETOC, The Value of Model Ecosystem Studies in Ecotoxicology. Technical Report, Brussel, 1997. 

Application of radiolabeled mirex to plants grown in a terrestrial/aquatic laboratory model ecosystem indicated that when the plant leaves were eaten by caterpillars, the aquatic system became contaminated. Mirex was detected in all segments of two aquatic food chains (alga > snail and plankton > daphnia > mosquito > fish) within 33 days. Undegraded mirex contributed to over 98.6, 99.4, 99.6, and 97.9% of the radiolabel in fish, snails, mosquitoes, and algae, respectively. No metabolites of mirex were found in any of the organisms (Francis and Metcalf 1984 Metcalf et al. 1973). 

Francis BM, Metcalf RL. 1984. Evaluation of mirex, photomirex and chlordecone in the terrestrial aquatic laboratory model ecosystem. Environ Health Perspect 54 341-346. 

Sanborn JR, Metcalf RL, Yu CC, et al. 1975. Plasticizers in the environment The fate of di-n-octyl phthalate (DOP) in two model ecosystems and uptake and metabolism of DOP by aquatic organisms. Arch Environ Contam Toxicol 3 244-255. 

Tomizawa L. 1980. Biological accumulation of pesticides in an ecosystem-evaluation of biodegradability and ecological magnification of rice pesticides by a model ecosystem. Japanese Agricultural Research Quarterly 14 143-149. 

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