Impact of biochar on herbicide pollution in the litani river Basin

The Litani River, the largest in Lebanon, suffers from different kind of pollution including that caused by pesticides. Among the herbicides, Fluazifop (FLP), Terbuthylazine (TBZ) and Triclopyr (TCP) are the most used and therefore the sorption on sediment and soil samples from four sites along Litani river basin: Berdaouni, Joub Jannine, Aammiq and Qaraoun, was investigated. For the three herbicides and on all sediment and soil samples, the sorption data, fitted to Freundlich logarithmic equation, show very low Kads values. At sediment and soil pH values, the herbicides and sediment and soil colloids are negatively charged, therefore negative sorption should be expected. Nevertheless, the sorption observed suggest that a lipophilic effect is acting. FLP, TBZ and TCP are herbicides with a high risk of leaching. The addition of biochar (BC) to soils and sediments increases considerably Kads values of BC added sediments and soils in comparison with that of BC-free samples. Moreover, desorption is not observed suggesting that the sorption is not reversible and hysteresis occurs. These findings suggest that the BC soil addition in Litani river basin area may be considered as an useful tool to prevent FLP, TBZ and TCP leaching in this polluted region of Lebanon.