In the field of science which includes soil pollution, natural attenuation applies to nature’s ability to reduce the toxicity, mobility, volume or concentration of contaminants in water and soil.
Calling oneself a hydrogeologist has many different meanings from completing simple well logging, to analyzing the extent of a chemical spill, to developing a complex groundwater model that reaches thousands of feet below the ocean floor.
While the training for hydrology and hydrogeology are completely different, in practice every hydrologist will do some level of hydrogeology and vice versa.