Humic acids from the sediments of three ecologically different estuarine systems-a comparison

Humic acids from the sediments of mangrove, estuarine and barmouth regions were isolated and characterized on the basis of elemental and functional group analyses. From the empirical formula deduced, it could be seen that humic acids segregated from the sediments of barmouth region is much different than those from estuarine and mangrove sediments. Humic acids from mangrove regions are proved to be much developed. The interactive effects of these developed humic acids with toxic metals like lead and cadmium were studied. The sorptional studies at varying metal concentrations and pH showed that lead binds on to humic acid easily than cadmium. Characterization with isothermal models reveled that the adsorption is more prominent at neutral pH. adsorption of lead fits well in to both Langmuir and Freundlich isotherms, but of cadmium only to Freundlich isotherm. At higher pH humic acid facilitates the dissolution of metal to the water column there by enhancing the toxicity and bioavailability