Humic substances (HS) are defined as a series of amorphous polymers, yellow-brown to black in color, relatively high molecular weight, complex and heterogeneous structures composed mainly of carbon, oxygen, hydrogen, which changes frequently its configuration depending on the interactions between the functional groups present in its structure. These substances are commonly present in landfill leachate from old landfills, providing difficulty in leachate treatment due to the high degree of recalcitrance of such organic matter. The determination of humic substances in leachate landfill samples is still a difficult measurement to be performed. There are methodologies that were modified to complex aqueous matrices as landfill leachates. These methods, modified Sheng and modified Lowry methods, were tested in two leachates generated in Gericino and Gramacho landfills in Rio de Janeiro State (Brazil). The recovery values for both methodologies were greater than 90% and within the acceptable range for recovery for waste and leachate analysis. The results for the quantification of SH in the leachate to modified Sheng and Lowry methods, respectively, were 616 and 608 mg.L-1 to Gericino leachate (1.4% of deviation) and 1182 and 1191 mg.L-1 to Gramacho leachate (0.72% deviation).
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