Characterization of humic and fulvic acids extracted with NaOH and NaOH‐Na‐pyrophosphate mixture from soils of arid and subhumid regions 1. analytical characteristics

Abstract

Abstract Humic acids (HAs) and fulvic acids (FAs) were extracted from a pine forest and cultivated Mollic Ustifluvent of Momi Hills (subhumid) and from an Aridic Ustochrept of Hisar using 0.1 M NaOH and a mixture containing 0.1 M each of NaOH and Na4P2O7 as extractants. The carbon content was highest in HAs of cultivated Morni soil and lowest in HAs of forest soil, while O contents were just the reverse. The N content of HAs was influenced by N application rates in soil. The mixture‐extracted HAs and FAs contained more C but generally less O than those extracted by NaOH. The two extradants did not produce consistent changes in N and H content. Carboxylic (‐COOH) groups in FAs and phenolic ‐OH groups in HAs predominated over other O‐containing acidic groups. The mixture‐extracted HAs and FAs had higher values of dissociation constants, total acidity, ‐COOH content, intrinsic viscosity, weight, volume, diameter, thickness, and axial ratio of the particles than those extraded with NaOH. A rod‐like configurat...