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. This model is based on the assumption that organism only responds to the free-metal ion concentration in solution, regardless of the nature of the metal complexes present in water (J. Phycol, 2005).
For example in case of AgCl(s) Ag+(aq) + Cl-(aq) if the Cl- ion increase that that can be consumed by Ag+ ions the concentration of Cl- will increase in water and if the concentration of Cl- ions is lesser than that of Ag+ there will be more free Ag+ cations in the water. And if the extra Ag+ ions are not consumed by other anions available in water the Ag metal toxicity of water will increase.
Biotic Ligand Model
The Biotic Ligand Model (BLM) use metal speciation and the protective effects of competing cations (+ve metal ions) to predict metal binding at a surface with possibility of acute metal toxicity (e.g. gill of a fish). A legand may be defined as chemical structures that bind with another chemical or metal.
It is an effective and widely used model to determine acute metal toxicity of dissolved metals. It relies on the mathematical integration of interaction of trace metal or solution phase ligands with biotic ligands i.e. the living organism exposed to the toxicity. This model analyses the ligand's interaction with living beings (biotic ligands). Biotic legand model predict the toxicity of dissolved metal according to the quantity of metal deposited on the receptor living being. Following diagram shows conceptual biotic legand model.
Fig: Conceptual Biotic Legand Diagram
Biotic legand model of toxicity prediction clearly shows the effect of water chemistry variation on the toxicity of metal. Water chemistry which is characterized by the dissolved hydrogen, oxygen, and carbon-di-oxide ...
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(“Metal Toxicity Essay Example | Topics and Well Written Essays - 1000 words”, n.d.)
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(Metal Toxicity Essay Example | Topics and Well Written Essays - 1000 Words)
“Metal Toxicity Essay Example | Topics and Well Written Essays - 1000 Words”, n.d. https://studentshare.net/science/300250-metal-toxicity.
The name often refers to a category name of metalloids (semimetals) and metals associated with eco-toxicity or toxicity potential and contamination (Daffus, 2002). There is an assumption that all heavy-metals and their compounds have properties that are eco-toxic or highly toxic.
The thing about toxicants is that there are many different potential, forms, means of exposure, plus reactions due to a combination of exposures that can make determining the safest levels like fitting together a puzzle where the pieces keep changing.
When he was discharged from the hospital, we consulted a paediatrician, who gave him still more antibiotics. This casual medication took its toll on Zach's immune system and his progress was inhibited."1
There are numerous Zachs' in this world whose life is at peril due to careless medication.
Lack of adequate guidelines for evaluation of the significance of contaminated sediments creates problems for environmental managers. Groundwater is water that is found underground in cracks and spaces in soil, sand and rocks. The area where water fills these spaces is called the saturated zone.
The mode of action of antibiotics on microorganism are:- inhibition of cell wall synthesis, damage to the cytoplasm membrane, inhibition of nucleic acid and protein synthesis, inhibition of specific of enzyme systems. (Michael J Pelczar, 5th edition, page 515)
particles, heavy metals, animal and human waste, toxic chemicals like chlorine, phosphorus, iron coming from chemical manufacturers, gasoline, oil and grease which could cause detriment to the health of the human beings (Perlman 2009).
The goal of wastewater treatment
b chronic toxicity is used to determine the level of toxicity that arises in a subject for a particular period that is from recurring exposures of some weeks to several months. Chronic testing on the other hand is used to determine the level of toxicity that arises in a subject
The author states that a metal drum corrodes since it is exposed to the factors that are favorable for corrosion. Since the problem has already occurred, there are various remedies that could be used in controlling the situation. Welding would be an option to eradicate the cracks and leaking places.
singly becoming an issue of concern because of their well-documented toxicological as well as carcinogenic effects besides the rising environmental levels via industrial pollution. It has been broadly emphasized that such metals may be genotoxic by numerous modes of action and