Dioxin leaching risk assessment through selected soils by estimating distribution coefficient and breakthrough curves.

From health and environmental point of views, dioxins are important due to their toxicity and persistence. Dioxins have the potential to reside in the environment for longer time if sorbed onto the clay and organic content of the soil matrix. Their transport or leaching under certain environmental conditions such as preferential flow can increase the risk of groundwater contamination. In the current study, breakthrough curves (BTCs) against time were plotted for selected dioxin transport prediction; based on measured distribution coefficient (Kd), dispersion coefficient (D), and retardation factor (R). Three representative soil series named Burhan, Warsak, and Kunda were selected. For dibenzo-p-dioxin (DD), Kd values followed the order as: Burhan> Warsak > Kunda, while for 2-chloro dibenzo-p-dioxin (2 Cl-DD), Kd values followed an order as: Kunda > Burhan > Warsak. Dioxin transport was measured at two different linear velocities (20 and 50 cm day-1). Attainment of equilibrium was verified to be dependent upon the Kd, R, D, and chlorination on dioxin. Kunda series with low OM (0.6%), clay (0.2%), and R (377) was found to have relatively high DD transport potential under normal velocity, due to high dispersion values for its sandy nature. Under the steady or preferential flow conditions, all the plots obtained were identical irrespective of soil type and dioxin nature.