High (36)Cl/Cl ratios in Chernobyl groundwater.

Area of Science:

• Environmental Science
• Radiochemistry
• Hydrogeology

Background:

• Chernobyl Nuclear Power Plant explosion in 1986 led to burial of contaminated material in exclusion zone trenches.
• Strontium-90 (90Sr) plumes were detected downgradient of Trench T22.
• Chlorine-36 (36Cl), a conservative radionuclide, is proposed as a tracer for groundwater contamination.

Purpose of the Study:

• Investigate Chlorine-36 (36Cl) as a tracer for Chernobyl contamination extent.
• Determine the maximal extent of the contamination plume from Trench T22 in groundwater.
• Assess the suitability of 36Cl for long-term plume monitoring.

Main Methods:

• Measurement of 36Cl/Cl ratios in groundwater, trench soil water, and leaf leachates.
• Comparison of measured 36Cl/Cl ratios with theoretical natural ratios.
• Analysis of plume extent relative to 90Sr.

Main Results:

• 36Cl/Cl ratios were 1-5 orders of magnitude higher than natural levels, indicating post-Chernobyl contamination.
• Trench T22 is a significant modern source of 36Cl.
• Groundwater contamination by 36Cl is likely due to dilution of trench soil water with uncontaminated water.
• The 36Cl plume extends further than the 90Sr plume.

Conclusions:

• 36Cl is a suitable tracer for Chernobyl contamination from Trench T22 in groundwater.
• The contamination is persistent and widespread.
• Further characterization of modern 36Cl release processes from trench soil is needed for precise plume delineation.