Chemical Characteristics of Humic Acids in Relation to Lead, Copper and Cadmium Levels in Contaminated Soils from South West Nigeria

Authors

  • Iheoma M Adekunle University of Agriculture Abeokuta, Nigeria
  • Toyin A Arowolo University of Agriculture Abeokuta, Nigeria
  • Naomi P Ndahi
  • Babajide Bello University of Agriculture Abeokuta, Nigeria
  • David A. Owolabi University of Agriculture Abeokuta, Nigeria

Keywords:

copper, lead, cadmium, Nigerian soils, humic acids, analysis

Abstract

Humic acids (HAs) extracted from topsoils obtained from the highways, motor parks and auto-repair workshops in Lagos, Ibadan and Abeokuta, Nigeria were characterized by infrared spectroscopy, titration and UV-visible spectroscopy for reactive groups. The relative abundance of metals as determined by atomicabsorption spectrophotometry decreased in the order Pb > Cu > Cd. Concentrations of soil total Cd (1.7 ± 0.2 to 1.9 ± 0.2 mg/kg), Cu (184 ± 25 to 360 ± 31 mg/kg) and Pb (1039 ± 123 to 1524 ± 88 mg/kg) exceeded international reference values for uncontaminated soils. Parametric and nonparametric correlations of the metal concentrations with humic acid chemical characteristics gave both negative and positive coefficients, some of which were significant at p ≤ 0.05. Competitive trace metal complexation reactions with an equimolar solution of the cations revealed that the HAs bound more Pb (0.911 mmol/g) than Cu (0.779 mmol/g) or Cd (0.237 mmol/g). The oxygen-containing groups (carboxyl and phenol), the chromophores that absorbed in the UV-visible region and the hydrophobic nature (E4/E6 ratios from 4.4 ± 0.2 to 5.7 ± 0.2) of the humic acids affect soil metal sorption.

Permanent URL: http://hdl.handle.net/2047/d10006084

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Published

2007-03-07

How to Cite

Adekunle, I. M., Arowolo, T. A., Ndahi, N. P., Bello, B., & Owolabi, D. A. (2007). Chemical Characteristics of Humic Acids in Relation to Lead, Copper and Cadmium Levels in Contaminated Soils from South West Nigeria. Annals of Environmental Science, 1. Retrieved from https://openjournals.neu.edu/aes/journal/article/view/v1art4

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Articles