Attenuation comprises which of the following statements?

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Attenuation in groundwater is about reducing contaminant mass as water moves through the subsurface. The key processes that achieve this are retardation, degradation, and adsorption. Retardation slows the advance of a contaminant because it spends time attached to solids or diffusing into less mobile zones. Degradation breaks down the contaminant into less harmful or less mobile forms, lowering its concentration. Adsorption is the sticking of contaminants to mineral surfaces, removing them from the dissolved phase and slowing their travel. Together, these mechanisms lower the amount of contaminant that can migrate to receptors like wells or ecosystems.

The other descriptions are narrower or describe different fate paths: sequestration by mineral surfaces is a form of adsorption but doesn’t encompass the full set of attenuation processes; complete dissolution would not reduce contaminant mass in the water; volatilization removes contaminant to air, which is only one possible path and doesn't capture the whole attenuation concept.