Natural attenuation definition

The phrase natural attenuation as understood within the context of subsurface remediation of contaminated soil and water evolved over a period of several years. It has largely been accepted as the politically and scientifically appropriate term, however it is still frequently used synonymously with Intrinsic remediation , natural recovery , and natural assimilation . The phrases intrinsic bioremediation and passive bioremediation refer strictly to biologically mediated attenuation processes, which are obviously a less broad definition, not including all the physical and abiotically mediated processes that... 

Uncertain time line and outcome - Unlike natural disasters which have a definite endpoint, natural attenuation is a time intensive process and there in uncertainty as to the extent to which the contamination will be removed... 

The International Union of Pure and Applied Chemistry recommends that the definition should now be based on the ratio of the radiant power of incident radiation (Pq) to the radiant power of transmitted radiation (P). Thus, A = log(Po/P) = log T. In solution, Pq would refer to the radiant power of light transmitted through the reference sample. T is referred to as the transmittance. If natural logarithms are used, the quantity, symbolized by P, is referred to as the Napierian absorbance. Thus, B = ln(Po/P). The definition assumes that light reflection and light scattering are negligible. If not, the appropriate term for log(Po/P) is attenuance. See Beer-Lambert Law Absorption Coefficient Absorption Spectroscopy... 

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