Influence of soil pH on the sorption of ionizable chemicals: modeling advances

Antonio Franco, Wenjing Fu, Stefan Trapp

Research output: Contribution to journalJournal articleResearchpeer-review

1 Downloads (Pure)

Abstract

The soil-water distribution coefficient of ionizable chemicals (K-d) depends on the soil acidity, mainly because the pH governs speciation. Using pH-specific K-d values normalized to organic carbon (K-OC) from the literature, a method was developed to estimate the K-OC of monovalent organic acids and bases. The regression considers pH-dependent speciation and species-specific partition coefficients, calculated from the dissociation constant (pK(a)) and the octanol-water partition coefficient of the neutral molecule (log P-n). Probably because of the lower pH near the organic colloid-water interface, the optimal pH to model dissociation was lower than the bulk soil pH. The knowledge of the soil pH allows calculation of the fractions of neutral and ionic molecules in the system, thus improving the existing regression for acids. The same approach was not successful with bases, for which the impact of pH on the total sorption is contrasting. In fact, the shortcomings of the model assumptions affect the predictive power for acids and for bases differently. We evaluated accuracy and limitations of the regressions for their use in the environmental fate assessment of ionizable chemicals.
Original languageEnglish
JournalEnvironmental Toxicology and Chemistry
Volume28
Issue number3
Pages (from-to)458-464
ISSN0730-7268
Publication statusPublished - 2009

Keywords

  • Sorption
  • Organic carbon-water partition coefficient

Fingerprint

Dive into the research topics of 'Influence of soil pH on the sorption of ionizable chemicals: modeling advances'. Together they form a unique fingerprint.

Cite this