Effect of Mangroves on the Horizontal and Vertical Distributions of Rare Earth Elements in Sediments of the Zhangjiang Estuary in Fujian Province, Southeastern China

To examine the influence of the mangrove environment on the distribution of rare earth elements (REE) in estuarine sediments, surface and core sediments were collected from regions of mangrove forest, forest fringe, and adjacent mudflat in the Zhangjiang estuary, SE China. Concentrations of REE were determined in surface sediments and core samples using inductively coupled plasma mass spectrometry. Light REE were more enriched than heavy REE, with a relatively weak negative europium anomaly with respect to the North American shale composite in sediments of the Zhangjiang estuary. Significant differences for REE were found among sampling sites and locations, following the order mangrove forest, to forest edge, to mudflat. The main source for REE in the estuary is the weathered continental materials from the Zhangjiang River drainage basin. The mangrove environment affected the physicochemical features and thus affected the REE spatial distributions in sediments. Vertical REE distributions in core samples were altered by mangrove root activity. Mangroves played a significant role in controlling the horizontal and vertical distribution of REE in sediments of the Zhangjiang estuary.