In sandy soils organic matter is often the dominant solid phase constituent with regard to (heavy) metal adsorption. We consider the complicated parameter intensive (NICA) adsorption model which may be simplified to less demanding Freundlich models. Parameters are fitted using batch titration data for purified humic acid. With two plausible adaptations, the fitted model is able to predict adsorption with soil organic matter and DOC for varied pH of the soil solution. The models adequately predict copper mobility in laboratory column experiments. Also the relationship between total and dissolved copper, DOC, and pH for a sandy profile (0-0.90 m) at a contaminated site was accurately predicted with the model.