Natural Attenuation

Natural attenuation (See Environment Agency Guidance at Reference #25 on Downloads page) covers a wide range of natural processes that usually leads to the reduction in pollution as water moves through soils and strata. Besides looking for evidence of decreasing concentrations of contaminants, it is important to look for evidence of the processes that could be causing those decreases. This includes evidence of degradation through decreased concentrations of dissolved oxygen, nitrate, sulphate or increased concentrations of iron, manganese, ammoniacal nitrogen, and perhaps hydrogen sulphide gas. Depending on the carbonate content of the strata and the amount of attenuation occurring pH and alkalinity can also be affected.

Nick’s understanding of hydrochemical processes and contaminant properties allows him to check for a number of lines of evidence of natural attenuation. This is important when trying to build a robust case for the use of natural attenuation, rather than active groundwater clean-up, to mitigate against off site migration of contamination.