Estimation of uranium in groundwater and assessment of age-dependent radiation dose in Nalbari district of Assam, India

Abstract

Uranium concentration has been estimated in 31 groundwater samples collected from the Nalbari district of Assam in pre-monsoon and post-monsoon season. Fourteen other water quality parameters have also been monitored to study their correlation with uranium. The uranium concentration varies from 0.3 to 7.1 µg/L with the mean value of 2.15 µg/L in pre-monsoon and 0.6–10.3 µg/L with the mean value of 2.75 µg/L in the post-monsoon season. The higher concentration of uranium in post-monsoon may be ascribed to the dissolution of uranium from soil sediments in the rainy season. It has been observed that the uranium content in both seasons is far lower than the WHO (2011) permissible limit of 30 µg/L. In both seasons, nitrate, sulphate, and especially phosphate show a positive correlation with uranium, which may be due to different agricultural activities. Agricultural nitrate and phosphate fertilization might be the carrier of uranium in groundwater through dissolution. For all life stage groups, the annual effective dose was appeared to be far below the WHO (2011) prescribed limit of 100 µSv/y. In consideration to adults, the ingestion dose for infants was turned out to be higher. The carcinogenic and non-carcinogenic risk was less than the permissible limits for both children and adults. Both dose value and risk indices were found higher in the post-monsoon season.

A systematic study of uranium in groundwater and its correlation with other water quality parameters

“…Though from the correlation data, some inferences can be made as Uranium for both seasons show a very weak positive correlation with ORP which signifies the favorable conditions for Uranium transport and release in aquifers (Saikia et al 2021). Dissolved Oxygen shows a negative correlation for the range of À0.13 and À0.168 for the pre and post-monsoons respectively as for the fact that the increase in the concentration of Uranium in drinking water is hazardous and thus the negative correlation is justified (Guidelines for drinking water quality 2008).…”

“…The use of chemical fertilizers enhances the leaching of phosphate through the soil, which precipitates as UO 2 (HPO 4 ) 2 À2 . Nitrate plays important role in the dissolution of uranium from minerals like uranyl nitrate [UO 2 (NO 3 ) 2 ] (Saikia et al 2021)]. The positive correlation coefficient for the hardness, calcium, and magnesium for the pre-monsoon season comes more in the range of 0.36, 0.30, and 0.32 respectively and decreases to a value of 0.20, 0.12, and 0.18 respectively in the post-monsoon as the concentration of the uranium decreases.…”

A correlational study of uranium in groundwater with other physicochemical parameters using GIS mapping in Godda district of Jharkhand, India

“…Uranium content in water resources is the combined contribution of natural and anthropogenic activities such as geogenesis, host-water interaction, runoff water, industrial e uents, phosphate fertilizer, fossil fuels etc. (Saikia et al, 2021.). Under conducive oxic conditions, Uranium leaches out of the host rocks and enters groundwater, governed by complex physico-chemical processes.…”