Geochemistry of tropical coastal lagoon sediments from Sungai Kilim, Langkawi, Malaysia: Implications for provenance and weathering

The interaction between land and sea in the coastal zone is dynamic and highly sensitive. It not only records past transgression history, coastal environmental evolution, and sea level changes, but also provides information on climate fluctuations, ocean and river changes, ecological environmental evolution, and human-induced environmental impacts. Coastal zone deposition plays a crucial role in preserving records of paleoenvironment changes and is therefore a key component larger ‘source to sink’ systems at continental margin. Therefore, it has attracted great academic interest in the field of geoscience in recent years. In this study, we measured trace elements and rare earth elements (REEs) in 20 surface sediment samples and a core (LKC 2) collected from the coastal lagoon of Sungai Kilim, Langkawi, Malaysia, to determine the possible sources and to reveal the variations in response to climate change and human activities. The distribution of trace elements (e.g., Li, Ti, Cr, Co, Ni, Cu, Zn, and Mn) was enriched in surface sediments, indicating those elements are affected by human activities. Besides, the concentrations of trace element in LKC 2, combined with AMS dating further confirmed the anthropogenic provenance in the uppermost core layers as a result of deforestation and urbanization in recent decades. However, the low Rb/Sr ratios in surface sediments and LKC 2 corresponds to higher intensity chemical weathering, resulting in higher concentrations of dissolved Sr in the sediments. The enrichment of REEs in surface sediments and LKC 2 indicates typical minerals present in the study area. Overall, the elemental flux patterns observed in this study are responses to complex interactions between intensified human activities and natural climate variability.