Model ecosystems static

As one procedure of simulating natural aquatic environment, a freshwater static model ecosystem was established (Figure 3)... 

In a static model ecosystem, several amino derivatives of fenitrothion, probably derived from the soil metabolism, were demonstrated in carp tissues, together with the nitro-containing compounds. The concentration of fenitrothion in carp, snails, daphnids and algae decreased with time, although its bioaccumulation ratio relative to the concentration in water tended to increase gradually in snails, daphnids and algae, presumably due to lower metabolic activity and/or slow excretion. 

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). 

Experimental aquatic metabolism systems have taken one of four forms -- static water in ordinary aquaria, jars, or beakers static "model ecosystems" static outdoor ponds and continuously-flowing systems (Table 1). A very rough comparison of their advantages is shown in Table II. For example, while the static aquaria doubtless are by far the... 

This project was designed to demonstrate that the static water model ecosystems can be scaled up in size to provide sufficient amounts of biomass, soil, and water to study metabolism kinetics of pesticides. Fourteen kg of soil, treated with [l C]-trifluralin at 10 ppm, was flooded with 84 liters water. Blue-gill fish, snails, daphnids, and algae were exposed to this system for 72 days. Samples of soil, water, and organisms were periodically analyzed for trifluralin and eight metabolites. 

So-called "model ecosystems" (12) offer environmental control similar to that in static aquaria but are much more complex and so far have been limited to a few carefully selected and compatible species — typically, microcrustaceans, small snails, and minnows -- which are hardy and tolerate each other in reasonable balance. Remetabolism and collection of... 

Laboratory model static ecosystem used by Metcalf [174]. It is not possible to calculate real steady-state BCF values. 

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