Radon measurements and mitigation at a fish hatchery

Area of Science:

• Environmental Science
• Public Health
• Hydrogeology

Background:

• Groundwater contamination with radon (Rn) poses a significant indoor air quality risk.
• High indoor radon levels were detected in a commercial fish hatchery, originating from groundwater sources.

Purpose of the Study:

• To evaluate the effectiveness of various mitigation strategies for reducing waterborne and indoor radon concentrations.
• To investigate the relationship between waterborne radon reduction and indoor radon levels in a commercial setting.

Main Methods:

• Passive and active mitigation techniques were employed, including packed columns, waterfalls, surface aeration, and bottom bubblers.
• Waterborne radon concentrations were measured before and after mitigation.
• Indoor radon levels were monitored, with consideration for diurnal variations and ventilation rates.

Main Results:

• Waterborne radon concentrations were reduced by up to 83% through combined mitigation procedures.
• A comparable reduction in indoor radon concentrations was not achieved, suggesting limited transferability of water mitigation effects.
• Indoor radon levels exhibited a diurnal cycle, peaking in the early afternoon, potentially due to temperature-driven gas exchange in the water.
• Achieving indoor radon levels below 148 Bq m(-3) was difficult even with water mitigation and high ventilation rates (23 air changes per hour).

Conclusions:

• While waterborne radon can be significantly reduced, this does not guarantee a proportional decrease in indoor radon levels.
• Factors influencing indoor radon, such as temperature-dependent gas dissolution, complicate mitigation efforts.
• Effective control of indoor radon in such environments may require integrated approaches addressing both water and air pathways.