Among all halogens fluorine (F) and chlorine (Cl) have the highest concentrations in soil followed by bromine (Br) and iodine (I). The variability of halogen contents in soils is high, which depends to a major degree on atmospheric deposition (Cl, Br, I), parent material (F), organic matter (Cl, Br, I), secondary minerals (F, Br), and local pollution (F, Cl). The enzyme-mediated reaction between halide ions and organic matter known as halogenation is considerable in some soils for Cl, Br and I, and should be accounted for in future ecosystem halogen budgets.