Metals, bioconcentration

Some metals used as metallic coatings are considered nontoxic, such as aluminum, magnesium, iron, tin, indium, molybdenum, tungsten, titanium, tantalum, niobium, bismuth, and the precious metals such as gold, platinum, rhodium, and palladium. However, some of the most important poUutants are metallic contaminants of these metals. Metals that can be bioconcentrated to harmful levels, especially in predators at the top of the food chain, such as mercury, cadmium, and lead are especially problematic. Other metals such as silver, copper, nickel, zinc, and chromium in the hexavalent oxidation state are highly toxic to aquatic Hfe (37,57—60). 

Recent studies suggest that mercury can cause an instant decrease in the sperm viability of fish at concentrations comparable to those which are permitted in drinking water (1 /rg C ). The bioconcentration of the metal to levels in the testis considerably higher than this from water containing only 1/30 of permitted levels" suggests that current legal limits are much too high. 

Significant zinc contamination of soil is only seen in the vicinity of industrial point sources. Zinc is a relatively stable soft metal, although it burns in air. Zinc bioconcentrates in aquatic organisms. 

Tanaka T, Ciffroy P, Stenberg K, Capri E (2010) Regression approaches to derive generic and fish group-specific probability density functions of bioconcentration factors for metals. Environ Toxicol Chem 29(ll) 2417-2425... 

Camusso, M., L. Vigano, and R. Balestrini. 1995. Bioconcentration of trace metals in rainbow trout a field study. Ecotoxicol. Environ. Safety 31 133-141. 

Lithner G, Holm K, Borg H. 1995. Bioconcentration factors for metals in humic waters at different pH in the Ronnskar area (N. Sweden). Water Air Soil Pollut 85 785-790. 

Arsenic, Cobalt, Copper TT assessment of relationships between acute toxicity and various experimental variables (e.g., metal concentration in water, time of exposure, bioconcentration factor) with two fish species. F,F (Liao and Lin, 2001)... 

It is well-known that pH is of importance for bioavailability and uptake of many chemicals, such as metals (e.g. Chapman et al. 1998), but pH may also be important for the same processes concerning organic substances. Nakamura et al. (2008) recently showed that acute toxicity and bioconcentration of the pharmaceutical fluoxetine was affected by pH in the Japanese medaka (Oryzias latipes). Toxicity increased with increasing pH and bioconcentration was lower at pH 7 and higher at pH 9, likely because of increase in nonionized forms with significantly higher hydrophobicity than the ionized forms at pH values closer to pKa. 

As we mentioned earlier, certain plant species are capable of taking up very high amounts of metals from the soil and water. Although As hyperaccumulators bioconcentrate As over 2000 mg kg in plant tissues, the biomass production rates of most of hyperaccumulator species are low. Therefore, a lack of rapid growth, large biomass... 

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