Grain size radioactivity of surficial quaternary deposits of Wadi Arar, Saudi Arabia

Abstract

The present study aims to distribute radioactive elements (radium 226Ra, thorium 232Th, and potassium 40K) within different grain sizes (gravel, coarse sand, medium sand, fine sand, and silt and clay) of quaternary alluvial deposits of Wadi Arar, north of Saudi Arabia. According to correlation analysis, r, radioactive elements have different correlations with different grain sizes and distance of Wadi Arar. Depending on hypothesis testing, Ra is the only element that has a significant correlation, with coarse sand and distance (− 0.82 and − 0.78, respectively), which is a strong and negative correlation. Upon the coefficient of determination, R2 (0.9), the reaction between Ra and both coarse sand content and distance are controlled by 3rd degree polynomial function. Conversion and diversion patterns through the distance between Ra and coarse sand content indicate the availability of three different lithofacies longitudinally, from upstream to downstream, (i) low content of coarse sand with high Ra concentration in the southwestern, (ii) medium content of coarse sand with medium Ra concentration in the central, and (iii) high content of coarse sand with low Ra concentration in the northeastern of Wadi Arar. With the increasing coarse sand content from upstream (SW) to downstream (NE), these three zones include a general decrease of Ra. Although there is a negative relationship between Ra and coarse sand content in the meander’s southern part, there is a positive relationship in the northern region, which increases the zonation to six by dividing the longitudinal zones by two for each.