EESA10H3 Lecture Notes - Lecture 5: Bioaccumulation, Heavy Metals, Bioavailability
20 Apr 2016
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Heavy metals: naturally occurring, extracted from the earth in ore, wide environmental dispersion, tendency to accumulate in select tissue, toxic in low concentration, metals never disapear. Class a: k, na, mg, ca, macronutrient, form ionic bond, low toxicity. Class b: hg, pb, ti, nonessential elements, form covalent bond, very toxic (form soluble organometallics) Borderline: cr, cu, as, co,ni,zn, mn, fe, micronutrient. Toxicity: class b > borderline > class a. Blocking essential functional groups such as protein or enzymes protein cannot carry anything. 2: modifying the active conformation of biomolecules. Resistance: species develop mechanism not to uptake mental (example pb) Tolerance: the capacity of a species to withstand high level of metals. Binding to nonsensitive compound structure, metabolic transformation to less toxic form (methylation of as in marine biota) Can develop multiple tolerance cu pb zn cd. Free ion species are more bioavailable (ex zn+2 > zn) Some neutral species may be available, important in complexes ph of solution.
