The total amount of exchangeable cations (calcium, magnesium, potassium, sodium, hydrogen, aluminum) a soil can hold on negatively charged sites on clay minerals and organic matter. Expressed as cmol(+)/kg or meq/100g, CEC is a primary index of soil fertility and recovery after thermal treatment.
Cation exchange capacity quantifies a soil's ability to hold and exchange the positively charged nutrients that plants take up. Negative charge sites arise from isomorphic substitution in clay minerals (permanent charge) and from deprotonation of carboxyl and phenolic groups on soil organic matter (pH-dependent charge). The sum of cations a soil can adsorb across these sites is its CEC.
Typical CEC values are 3 to 5 cmol(+)/kg for sandy soils, 10 to 30 for loams, and 30 to 60 or higher for clay- and organic-matter-rich soils. CEC controls nutrient retention, buffering against pH change, and a soil's response to fertilization. It is one of the four physical/chemical indices used to verify soil functional recovery after thermal treatment, alongside bulk density, water-holding capacity, and organic carbon content.
The 2017 SSSAJ peer-reviewed study of soils thermally treated at industrial scale demonstrated that CEC declines initially as organic matter is volatilized but recovers within one to two growing seasons when topsoil blending and revegetation are practised, supporting the case that thermal treatment is compatible with productive post-remediation land use.
Also known as: CEC, cation exchange.
The regulatory metric for thermal destruction performance, expressed as the percentage of a target contaminant destroyed across the system. Common permit thresholds range from 99.99 percent for general hazardous organics to 99.9999 percent (six nines) for PCBs, dioxins, and PFAS.
The duration that gas, vapor, or solids remain inside the heated zone of a thermal treatment unit; together with temperature and turbulence, one of the three governing parameters of complete contaminant destruction.
Liquid that has percolated through contaminated soil, waste, or stockpiles, dissolving and carrying contaminants downward to groundwater or to a collection system. The principal migration pathway for PFAS, dissolved metals, salts, and hydrocarbons from impacted sites.
Laboratory method that oxidizes PFAS precursors in a sample into measurable perfluoroalkyl acids, then quantifies the difference against a pre-oxidation baseline. Reveals the hidden precursor mass that targeted PFAS analysis alone misses.