Effect of Atrazine Contamination on Compressibility and Permeability Characteristics of Clay

Atrazine (ATZ) is one of the most heavily used herbicides in the world, particularly in the United States and Australia. This study evaluated the compressibility and permeability characteristics of two Western Australia natural clays contaminated with varying ATZ contents. A series of onedimensional consolidation tests using fixed-ring oedometer device were conducted, and the final hydraulic conductivity was calculated at the end of each loading stage. At the first stage, the strain-time graphs at 1,280 kPa effective overburden pressure (sigma'(n)) were evaluated, and the results indicated that the specimens with a greater ATZ content have higher values of final vertical strain (epsilon(v)). Then, the compression index (C-c) values were computed from the void ratio-effective overburden pressure curves (e-sigma'(n)), and the results showed that the compression index (C-c) increased as the ATZ content of the tested clays increased. At the next stage, the coefficient of consolidation (c(v)) was calculated using the Casagrande method and the Taylor method. The results showed that the computed coefficient of consolidation (c(v)) using the Taylor method was slightly greater than those calculated using the Casagrande method in both tested clays. Also, the hydraulic conductivity (k) values of the tested clays increased as the contamination content increased (i.e., 3.1 x 10(-7) <= k <= 129 x 10(-7) cm/s and 4.49 x 10(-9) <= k <= 95.3 x 10(-9) cm/s). This behavior, which was attributed to promotion of the agglomeration and aggregation between clay particles, promoted formation of the tiny voids in the soil. Finally, the secondary compression ratio (R-alpha) and secondary compression index (C-alpha) were computed, and the results showed that the specimens containing higher ATZ content had greater values of R-alpha and C-alpha.