GEOL 3070 Lecture Notes - Lecture 25: Immunodeficiency, Bioavailability, Eutrophication
25 Apr 2017
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Document Summary
Toxic chemicals cause death or adverse sub-lethal effects if an organism is exposed to concentrations above a threshold. Below some concentration, most chemicals are effectively safe. Thresholds = difficult to define because they are among. Some chemicals are required at low concentrations but are toxic at high concentrations, and therefore have an optimal range. Bioaccumulation: most toxic chemicals are more concentrated in organisms than in the surrounding seawater. Usually the chemical can be partially excreted and reaches some equilibrium with seawater, so that if the concentration in seawater decreases, the concentration in the organism also decreases. Bioamplification: some chemicals are mostly or entirely retained by organisms, and are therefore concentrated up the food chain. Includes certain organically-bound metals (e. g. hg) and compounds that are highly soluble in fatty tissues (e. g. synthetic organic compounds) Certain chemicals may defy the general rule that a safe concentration exists.
