Metals are very necessary for living beings but excess of metals and especially free toxic metal ions could be potentially damaging. Osmoragulatory affects of excessive metal exposure can affect ion transporting enzymes of Na+/K+ -ATPase in living beings.
Metal toxicity of water may be defined as the dissolved metal concentration per unit volume of water. Various models have been developed to predict acute metal toxicity of water. Following are the most used and most satisfactory models used for acute metal toxicity prediction:
To calculate water effect ratio first of all one solution is prepared in laboratory with known toxicity and average range of pH, dissolved oxygen, temperature, and specific conductivity is calculated. After that a water sample is collected from a site whose water effect ratio has to be calculated. Metal toxicity of the site water is calculated and the values of test from lab sample and site sample are used to calculate the ratio.
Free ion activity model is based on the fact that there is always equilibrium between free metal ions in a solution. This model uses Ion characteristics to predict the relative toxicity effects of metal ions. Most ion characteristics that are useful in predictive modeling of metal toxicity reflect the binding tendencies of metals to ligands (Christopher P. Tatara, Michael C. Newman, John T. McCloskey, Phillip L. Williams).
The concentration of metal ions in a solution depends upon various factors such as temperature and chemistry of water. Free ion activity model predicts the metal toxicity by directly measuring the metal ion concentration in water. ...