Lake environment model

We illustrate these concepts by applying various fugacity models to PCB behavior in evaluative and real lake environments. The evaluative models are similar to those presented earlier (3, 4). The real model has been developed recently to provide a relatively simple fugacity model for real situations such as an already contaminated lake or river, or in assessing the likely impact of new or changed industrial emissions into aquatic environments. This model is called the Quantitative Water Air Sediment Interactive (or QWASI) fugacity model. Mathematical details are given elsewhere (15). 

Model ecosystems have been used for about 8 years to measure the distribution and fate of pesticides in the aquatic environment. Over that period of time numerous design changes have evolved that have increased the versatility of the ecosystem and improved simulation of environmental conditions. In our laboratory, we have used the static model ecosystem primarily to model the pond or small lake environment, and to simulate the likely rates and modes of pesticide entry (1). More recently, we have developed larger systems capable of providing sufficient biomass for accumulation and dissipation rate determinations (2) and for metabolic studies (3). 

Ulrich, M. M., D. M. Imboden, and R. P. Schwarzenbach, MASAS - A user-friendly simulation tool for modeling the fate of anthropogenic substances in lakes , Environ. Software, 10, 177-198 (1995). 

Macleod M, Mackay D (2004) Modeling transport and deposition of contaminants to ecosystems of concern a case study for the Laurentian Great Lakes. Environ Pollut 128 241-250... 

Dean, W. E., 1981. Carbonate minerals and organic matter in sediments of modern north temperate hard-water lakes. In Ethridge, F. G. R. M. Flores (eds.) Recent and Ancient Nonmarine Depositional Environments Models for Exploration. SEPM Spec. Pub. No. 31 213-231. 

Sobecky PA, MA Schell, MA Moran, RE Hodson (1992) Adaptation of model genetically engineered microorganisms to lake water growth rate enhancements and plasmid loss. Appl Environ Microbiol 58 3630-3637. 

Wolfe M, Norman D. 1998a. Effects of waterborne mercury on terrestrial wildlife at Clear Lake Evaluation and testing of a predictive model. Environ Toxicol Chem 17 214-227. 

The QUASI fugacity model was then run for a trichlorobiphenyl in a lake the size of Lake Michigan, being approximately 60,000 times the size of the evaluative environment. A detailed justification for the selection of D values is beyond our scope here but in selecting values, we have relied on recent reports by Neely (11), Rogers (15), Armstrong and Swackhamer (16), Thomann (17), and Andren (18). 

Progress can best be made by applying these models to new and existing chemicals at all scales, i.e. to real environments such as Lake Michigan, to rivers, or small ponds, to microcosms and ultimately to laboratory flasks in which one process is isolated for study. The fugacity models described here will, it is hoped, contribute to the integration of such disparate data into more accurate profiles of chemical behavior in the environment. 

This gives an example of fate modeling in which the risks of an insect growth inhibitor, CGA-72662, in aquatic environments were assessed using a combination of the SWRRB and EXAMS mathematical models.. Runoff of CGA-72662 from agricultural watersheds was estimated using the SWRRB model. The runoff data were then used to estimate the loading of CGA-72662 into the EXAMS model for aquatic environments. EXAMS was used to estimate the maximum concentrations of CGA-72662 that would occur in various compartments of the defined ponds and lakes. The maximum expected environmental concentrations of CGA-72662 in water were then compared with acute and chronic toxicity data for CGA-72662 in fish and aquatic invertebrates in order to establish a safety factor for CGA-72662 in aquatic environments. 

Formica, S.J., Baron, J.A., Thibodeaux, L.J., Valsaraj, K.T. (1988) PCB transport into lake sediments. Conceptual model and laboratory simulation. Environ. Sci. Technol. 22, 1435-1440. 

Aggett, J. and G.A. O Brien. 1985. Detailed model for the mobility of arsenic in lacustrine sediments based on measurements in Lake Ohakuri. Environ. Sci. Technol. 19 231-238. 

The environmental impact of a new product needs to be assessed before it can be released for general use. Chemicals released into the environment can enter the food chain and be concentrated in plants and animals. Aquatic ecosystems are particularly sensitive, in this respect, since chemicals, when applied to agricultural land, can be transported in the ground water to rivers and then to the lakes, where they can accumulate in fish and plant life. The ecokinetic model presented here is based on a simple compartmental analysis and is based on laboratory ecosystem studies (Blau et ah, 1975). The model is useful in simulating the results of events, such as the accidental spillage of an agrochemical into a pond, where it is not ethical to perform actual experimental studies. 

Thomann, R. V., and J. P. Connolly, Model of PCB in the Lake-Michigan lake trout food-chain , Environ. Sci. Technol., 18, 65-71 (1984). 

Li, A., Jang, K., Scheff, P., 2003. Application of EPA CMB8.2 model source apportionment of Sediment PAHs in Lake Calumet, Chicago. Environ. Sci. Technol. 37(13), 2598-2965. 

It shall be remarked that the application of PLS modeling for other case studies in the aquatic environment is also described in the literature. SEIP et al. [1994] applied PLS calibration to determine which physical factors determine the phytoplankton mass in lakes. 

In this chapter, we examine biogeochemical applications of the FREZCHEM model to Earth, Mars, and Europa, where cold aqueous environments played and continue to play a critical role in defining surficial geochemistry. Interpretations include the potential for life in these environments. These simulations cover applications to seawaters, saline lakes, regoliths, aerosols, and ice cores and covers. These examples are the proverbial tip of the iceberg in terms of the potential of this model to describe cold aqueous geochemical processes. At the end of the chapter, we discuss application limitations, cases where the underlying thermodynamic assumptions are at variance with real-world situations. 

First we review controls on the amount and isotopic composition of various forms of sulfur in lacustrine environments. Next, we summarize the diverse behavior of sulfur in sediment from two freshwater environments in sediment from three modern, productive, saline lakes and in oil shales deposited in freshwater and saline lacustrine environments. Lastly, our results are integrated in order to produce models that 1) predict the extent of formation and isotopic composition of sulfide minerals in response to major controls on sulfur geochemisty and 2) show the formational pathway of organosulfur in lacustrine oil shale and its derivative oil. 

Bierman, V., Swain, W. (1982) Mass balance modeling of DDT dynamics in Lakes Michigan and Superior. Environ. Sci. Technol. 16, 572-579. 

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