Immobilization of Atrazine Using Oxidized Lignite Amendments in Agricultural Soils

Abstract

Leonardite (LND), a low-grade coal, is an inexpensive material used to improve soil fertility in humic-deficient soils. Our objective was to quantify the ability of LND to immobilize atrazine (ATZ). To accomplish this, LND morphological properties, elemental composition, and spectroscopic properties were determined. We found that LND had a high organic matter content (40.53%, w/w) with a mesopore particle structure. Fourier-transform infrared spectroscopy spectral analysis confirmed the presence of aromatic molecules, all of which contributed to ATZ adsorption. The ATZ adsorption characteristics were quantified using batch adsorption kinetic and isotherm experiments. The ATZ adsorption kinetics were best described by a pseudo-second-order kinetic model while the concentrations of ATZ adsorbed (Cads) versus equilibrium concentrations (Ceq) had the best fit with the Freundlich equation compared with five other isotherms tested. The ability of LND to minimize ATZ leaching was tested using one-dimensional transport experiments with packing configurations and materials. The results revealed that up to 95% of ATZ was immobilized in the LND-amended soil. The extractable ATZ residues from both soil and LND corroborated the reduction in ATZ leaching. Overall, the adsorption results indicated that LND had a high affinity for ATZ adsorption and could reduce ATZ transport to the groundwater.