When considering the environmental fate of a metal, it is not always possible to clearly separate the processes related to the transport and partitioning of a metal, its compounds, and complexes from those related to transformation and degradation of these metal species. Because of analytical limitations, investigators do not often identify the form of a metal present in the environment. A change in the transport or partitioning of a metal may result from the transformation of the metal from one form to another. For example, complexation of a metal with small organic compounds may result in enhanced mobility, while formation of a less-soluble sulfide would decrease its mobility in water or soil. Adsorption may be the result of strong bonds being formed (transformation) as well as weak ones. Characterizing weak and strong adsorption is dependent on the analytical method that is used and care should be exercised when comparing results from different studies.