Detecting Organic Contaminants in the Unsaturated Zone Using Soil and Soil-Pore Water Samples

ABSTRACT

A lysimeter study was conducted to compare the effectiveness of soil core and soil-pore water samples in detecting the movement of organic constituents from land-treated industrial wastes. Lysimeters collected from the Bastrop (Udic Paleustalf), Padina (Grossarenic Paleustalf), and Weswood (Fluventic Ustochrept) soils were amended with a refinery separator sludge, a wood-preserving bottom sediment sludge, or a nonhalogenated solvent recovery sludge at rates of 50, 15, and 50 g kg⁻¹, respectively. Soil-pore water samples from porous ceramic cups and soil cores were collected monthly at three depths in the lysimeters to monitor n-alkanes and polynuclear aromatic hydrocarbons from the petroleum waste, phenols and cresols from the wood-preserving waste, and aromatic solvents from the solvent recovery waste.

The organic carbon normalized soil sorption coefficient (K_oc) may be useful for determining when soil-pore water or soil core samples will be most effective in detecting organic chemicals in the unsaturated zone of soils. N-alkanes with log K_oc values < 4.4; PNAs < 3; chlorophenols (mono-, di-, tri-) < 4.0; nitrophenols (mono-, di-) < 2.3; and aromatics < 3.3, are best detected using soil-pore water sampling methods. N-alkanes with log K_oc values between 4.8 and 6.2 are equally detected by either sampling method. Otherwise, all these classes of chemicals with log K_oc values greater than those mentioned are best detected by obtaining soil cores.