Characteristics of humic substances from strongly acidic soil remediated and restored using humin enhanced biodegradable waste materials

Description

Abstract This study builds on the previous project on remediation of degraded Okpoma soil using humin enhanced bio-degradable waste material. As a follow up to successful remediation and restoration works, this present investigation focused on chemical characterization of soil humic substances (humic acid and fulvic acid) in order to give a chemistry-based explanation on the improved crop performance recorded for remediated soil systems relative to the control. Consequently, the extracted humic substances were subjected to (i) Volumetric analysis for total, carboxyl and phenolic hydroxyl reactive groups and (ii) Uv– Visible evaluations for optical density (E4/E6 ratio) and optical density characteristics on the visible region in EMR spectrum. The soil system was characterized for pH and electrical conductivity properties using standard procedure. Results show the presence of carboxyl groups in the range of 220 to 280 meq/100g: of phenolic hydroxyl in the range of 272 to 364 meq/100g. The composition of phenolic hydroxyl versus carboxyl group in a given humic acid contained more phenolic hydroxyl relative to the carboxyl group in a given humic acid ranged from 90.7: 9.3% to 93.9: 6.1%. Results showed more aromatic carbon chain in the humic acid molecular fragments, while fulvic acids were characterized by an increased aliphatic carbon chain. Visible spectral absorptions were typical densities decreasing with a wavelength from 500nm to 800nm. Study revealed that humic substances contained in the soil organic matter in the remediated systems were characterized by oxygenated functional group (phenolic hydroxyl and carboxyl groups) capable of binding to plant nutrient cations and enhancing their soil, thereby promoting excellent crop growth. Further study is a contribution to enhance environmental performance for the oil and gas industry in Nigeria.