Heavy metal binding capacity

DETERMINATION OF THE HEAVY METAL BINDING CAPACITY (HMBC) OF ENVIRONMENTAL SAMPLES... 

The Heavy Metal Binding Capacity (HMBC) test is a bioassay that helps to quickly determine metal bioavailability in aquatic environments. HMBC can also be applied to soils and to root exudates from aquatic and terrestrial plants. The HMBC test is based on MetPLATE, a bacterial toxicity test that selectively detects metal toxicity. 

Prior to discussing the heavy metal binding capacity (HMBC) concept, we will introduce the MetPLATE toxicity assay, which is the sole test used to determine HMBC. 

The Heavy Metal Binding Capacity (HMBC) concept initiated in our laboratory (Huang et ah, 1999) is similar to that of WER, except that the ratio is obtained by using MetPLATE which, as mentioned above, is specific for heavy metal toxicity. This ratio assesses the binding and complexing ability of a given environmental sample toward added heavy metals. 

Table 4. Heavy Metal Binding Capacity (HMBC) for cadmium and copper, as determined by MetPLATE (adaptedfrom Huang et al., 1999).

Huang, F., Bitton, G. and Kong, I.-C. (1999) Determination of the heavy metal binding capacity of aquatic samples using MetPLATE a preliminary study, Science of The Total Environment 234, 139-145. 

SHMBC Soil Heavy Metal Binding Capacity... 

Interactions studies between some divalents metal ions and pectins from citms and sugar-beet revealed that the chemical structure of the latter, namely the presence of acetyl functions, induces differences of binding process whereas the scale of selectivity was not affected. Some further studies could be carried out on the correlation between the binding mode and the degree of acetylation. Lastly, pectins showed a clear scale of selectivity towards heavy metals with high capacities of binding which make them suitable to be used in waste-waters depollution. 

Albumin is a major transport facilitator of hydrophobic compounds which would otherwise disrupt cellular membranes. These compounds include free fatty acids and bilirubin as well as hormones such as cortisol, aldosterone, and thyroxine when these materials have exceeded the capacity of proteins normally associated with them. Albumin also binds ions, including toxic heavy metals and metals such as copper and zinc which are essential for normal physiological functioning but may be toxic in quantities in excess of their binding capacity for their carrier proteins. Binding of protons is the basis for the buffering capacity of albumin. 

The liver has two main functions in the body [12], The first is maintenance of internal nutritional homeostasis through facilitation of lipid absorption and intermediary metabolism. As described later, the large metabolic capacity of the liver renders it vulnerable to heavy metals through binding of the metals to and inactivation of electrophilic ligands. 

The adsorption of heavy metals onto amorphous or crystalline forms of iron oxide and clays occurs in nature and is phenomenologically related to the binding of contaminant to the superhcial ferric and/or aluminium ions. Although, this behavior explains the concentration of metal contaminants in soils, it does not constitute a viable method for trapping low concentrations of contaminants from aqueous streams because of its limited adsorption capacity. 

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