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 KHA, KFBC, and nbc values and measured fBC and foc values, Phen sorption affinity-related parameter Koc values can be predicted from the simplified dual sorption model: focKoc=(foc-fBC)KHA+fBCKFBCCenbc-1. For sediments from the Song–Liao watershed (China), the exponential model and dual sorption model gave good predictions for n and Koc values, which support the availability of the two predicted models.

Graphical abstractAbout 85% of the reported n values fall into the 90% confidence interval of the exponential model, indicating the practicability of the model in prediction of Phen sorption nonlinearity.Figure optionsDownload full-size imageDownload as PowerPoint slide