Abstract
Contents of rare earth elements (REEs), major elements, and the total organic carbon (TOC) were determined for 152 surface sediment samples collected from the continental shelf off Hainan Island (CSHI). From high to low, the average contents of REEs were as follows: Ce > La > Nd > Pr > Sm > Gd > Dy > Er > Yb > Eu > Ho > Tb > Tm > Tm. The LREEs in the south are more abundant than in the north, which is shown by the higher LREE/HREE values in south than in the north. This resulted higher values for the LREE/HREE ratio in the south than in the north. The mean enrichment factor (EF) could be arranged from highest to lowest as follows: Tm > Sm > Pr > Er > La > Lu > Ce > Tb > Eu > Nd > Yb > Gd > Ho > Dy. The EF indicates that pollution as a result of human activity was more serious in the southeast of the study area than in the north. The factors affecting the REE concentrations in this area include naturally occurring minerals and industrial pollution. Based on the spatial variation of upper continental crust (UCC)-normalized REE concentrations, the CSHI was classified into three geochemical provinces. The sediment of province I was controlled by the Red and Pearl rivers. The composition of the province II is mainly controlled by the Red River and the Pearl River, although some sediments have originated from the South China Sea Island. Province III sediments mainly originated from sources on Hainan Island.
Highlights
Rare earth elements (REEs), a group of related lanthanides (McLennan, 1980); have been used as indicators of geochemical processes
The aims of this paper were: (i) to identify the distribution of REEs in surface sediments collected from the continental shelf off Hainan Island (CSHI); (ii) to calculate the enrichment factor (EF) value of REEs and its spatial variation; (iii) to determine whether the enrichment of REE is related to human activities; (iv) to identify the potential sources of REEs in surface sediments collected from the CSHI
The purpose of this study is to provide a scientific basis for environmental management of the CSHI, with particular reference to the distribution of REEs in marine sediments
Summary
Rare earth elements (REEs), a group of related lanthanides (McLennan, 1980); have been used as indicators of geochemical processes. Examples of these geochemical processes include the chemical evolution of the crust and mantle (Cai et al, 2021a), tectonic evolution (Chen et al, 2020), surficial weathering (Hannigan et al, 2010; Qiao et al, 2020) and for identifying the source of material in different environmental systems (Delgado et al, 2012; Khan et al, 2016; da Silva et al, 2018; Li et al, 2018; Oral et al, 2019). The distribution, transport, and generation of REEs in continental shelf surface sediments have started to attract the attention of researchers (Wu et al, 2020)
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