Sustainable agricultural use of natural water sources containing elevated radium activity

Relatively elevated concentrations of naturally occurring radium isotopes ((226)Ra, (228)Ra and (224)Ra) are found in two main aquifers in the arid southern part of Israel, in activity concentrations frequently exceeding the limits set in the drinking water quality regulations. We aimed to explore the environmental implications of using water containing Ra for irrigation. Several crops (cucumbers, melons, radish, lettuce, alfalfa and wheat), grown in weighing lysimeters were irrigated at 3 levels of (226)Ra activity concentration: Low Radium Water (LRW)<0.04 Bq L(-1); High Radium Water (HRW) at 1.8 Bq L(-1) and (3) Radium Enriched Water (REW) at 50 times the concentration in HRW. The HYDRUS 1-D software package was used to simulate the long-term (226)Ra distribution in a soil irrigated with HRW for 15 years. Radium uptake by plants was found to be controlled by its activity in the irrigation water and in the soil solution, the physical properties of the soil and the potential evapotranspiration. The (226)Ra apeared to accumulate mainly in the leaves of crops following the evapotranspiration current, while its accumulation in the edible parts (fruits and roots) was minimal. The simulation of 15 years of crop irrigation by HYDERUS 1-D, showed a low Ra activity concentration in the soil solution of the root zone and a limited downward mobility. It was therefore concluded that the crops investigated in this study can be irrigated with the natural occurring activity concentration of (226)Ra of 0.6-1.6 Bq L(-1). This should be accompanied by a continuous monitoring of radium in the edible parts of the crops.