Predicted models for phenanthrene sorption nonlinearity and capacity based on different HA/BC ratios in sediments

Phenanthrene (Phen) sorption isotherms for synthetic sediment organic matter samples with nine different humic acid/black carbon (HA/BC) ratios were determined to provide predicted models for Phen sorption nonlinearity and affinity by sediments. The sorption data were fitted well by the Freundlich model. The nonlinear sorption of Phen was dominated by BC particles. According to BC/TOC content, Phen sorption nonlinearity can be predicted using the exponential model: n=0.410+0.454 *exp(-0.028 BC/TOC). As sorption is a combination of absorption into soft carbon and adsorption onto hard carbon, based on published K(HA), K(FBC), and n(bc) values and measured f(BC) and f(oc) values, Phen sorption affinity-related parameter K(oc) values can be predicted from the simplified dual sorption model: f(oc)K(oc) = (f(oc) - f(BC))K(HA) + f(BC)K(FBC)C(e)(n(bc) - 1). For sediments from the Song-Liao watershed (China), the exponential model and dual sorption model gave good predictions for n and K(oc) values, which support the availability of the two predicted models.