Model ecosystem for the evaluation of pesticide biodegradability and ecological magnification

Unique Information Contributed by Multispecies Systems: Examples From the Standardized Aquatic Microcosm

“…Chemical analyses of products were performed with many of the studies mentioned above and the data are in the papers cited. The SAM sediment was adapted from the studies of Metcalf et al (1971); they developed a ''model ecosystem'' consisting of quartz sand modeled into a sloping soil/air/water interface. The terrestrial end of the sand shelf was flattened to accommodate terrestrial plants.…”

“…Some have considered the sand substrate (amended with cellulose and chitin) of the SAM as a deficiency. We adapted the method of Metcalf et al (1971), who had great success in recovering the radioactively labeled parent and degradation products of test chemi-cals: ''The use of pure sand and water culture is not only much more reproducible than soil, but also eliminates a large amount of organic material which had uncertain effects and interfered with extraction and determination of radiolabeled products.'' Highly organic sediments can act as sinks of hydrophobic compounds and can sequester test chemicals in a nonextractable form.…”

Reactions and Processes

“…1). Basically their Metcalf et al (1971) was the first laboratory microecosystem designed to investigate the biodegradability and ecological fate of pesticides system was designed to follow qualitatively and quantitively the movement and degradation of compounds from a terrestrial to an aquatic environment and to demonstrate the movement of the parent compound plus its transformation products through aquatic food webs. Their system can be briefly described as follows: A terrestrial-aquatic environment is created in a 38 liter aquarium tank by sloping quartz sand into 7 liters of water.…”

Fate of 14C-lindane in a rice-fish model ecosystem

“…The model ecosystem technique for the evaluation of pesticide biodegradability and ecological magnification was introduced in 1971 ( Metcalf and Kapoor 1971). Since then, several modified ecosystems were constructed to fit actual paddy field conditions (Chen, 1982 ;Lee, 1976).…”

“…The ratio of the polar to the non-polar metabolites in fish and rice plant gives an indication about the biodegradability of lindane in these organisms(Table4). This is sometimes referred to as biodegradability index (Chen, 1982 ;Metcalf, 1973Metcalf, ,1971. The data in Table 4 indicate that lindane possesses a relatively low biodegradability in rice plant (0.15 after 30 days).…”