What does the term "natural attenuation" refer to in groundwater remediation?

The term "natural attenuation" in groundwater remediation refers to the process where natural biological, chemical, and physical mechanisms work to reduce contaminant concentrations in groundwater without the need for human intervention. This method harnesses the existing environmental processes, such as microbial degradation, dispersion, dilution, and adsorption, to stabilize or decrease the concentration of harmful substances over time.

Natural attenuation is particularly valuable as it can be a cost-effective and lower-impact approach to managing contaminated sites. It relies on the inherent abilities of the environment to treat its own pollutants, making it a sustainable option for long-term remediation.

The other options do not align with the concept of natural attenuation. For instance, using physical barriers to prevent pollution is a more active remediation approach, while speeding up natural filtration processes and injecting additives both involve enhancing or altering the existing environmental conditions rather than allowing them to function naturally.