Distribution and modelling of rare earth elements in Chinese river sediments

Fifty-nine sediment samples were collected from the major rivers of China and analysed using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The background rare earth element (REE) concentrations (μg/g) of these samples were: Sc, 11.1 (1.3–23.1); Y, 13.7 (3.3–24.8); La, 30.8 (7.6–57.2); Ce, 64.4 (16.5–122.6); Pr, 7.3 (1.6–14.4); Nd, 27.8 (5.6–58.5); Sm, 5.74 (1.1–11); Eu, 0.98 (0.05–1.7); Gd, 8.9 (1.6–16.8); Tb, 0.62 (0.12–1.2); Dy, 3.0 (0.53–5.0); Ho, 0.55 (0.09–1.00); Er, 1.4 (0.26–2.4); Tm, 0.19 (0.06–0.4); Yb, 1.0 (0.22–2.9); Lu, 0.16 (0.05–0.42). The total REE concentration (ΣREE), light-REE concentration (LREE) and heavy-REE concentration (HREE) were 44.5–315.8, 38.1–264.6 and 6.36–51.2 μg/g, respectively. The ratio of LREE to HREE ranged from 3.7 to 7.7. The average ratio was approx. 5.1 and did not show much variation with location. Total and individual element concentrations were normally distributed. The variation in the average REE concentration was not greater than 25 μg/g. A high degree of correlation was found between the REEs. Factor analysis indicated that REE concentrations in sediments were mainly described by two factors and the loading of the first two factors could be described by: Y = 1 − X2. Factor score plots were employed to distinguish between samples of natural and anthropogenic origin. Based on the inter-correlation determined between REEs in sediment samples, a model was developed to predict REE concentrations.