A Century of Trace Metal Accumulation Recorded in Lake Maninjau Sediments, Indonesia

Toxic trace elements preserved in lacustrine sediments provide valuable archives of long term environmental change yet their historical accumulation remains poorly constrained in rapidly developing regions. We investigate century scale trace metal variability using a well dated sediment core retrieved from the depocenter of Lake Maninjau, Indonesia. Sediment chronology was established using ²¹⁰Pb dating and a high resolution multiproxy geochemical analysis of trace and major elements (ICP-MS, XRF) including total organic carbon (TOC). Cu, Zn, Pb, and Cd show a gradual increase from the early to mid-20th century followed by a pronounced enrichment in the early 2000s. This recent intensification is most evident for Cd which remains relatively stable earlier in the record before increasing sharply in the last two decades. In contrast Pb exhibits a decline in concentrations during the most recent period. These geochemical changes coincide with a marked increase in TOC beginning around the mid-20th century and a transition from detrital dominated sediments to diatom enriched facies indicating a shift in Lake Maninjau’s depositional regime. The pronounced metal enrichment in the last two decades temporally coincides with the period of intensified aquaculture activity in the lake. The co-variation between TOC and trace metal enrichment suggests that increased organic loading associated with aquaculture expansion enhanced trace metal accumulation under changing depositional conditions. This study demonstrates a clear intensification of trace metal accumulation and organic matter deposition in Lake Maninjau over the last century highlighting the value of sediment records for assessing long term pollution trajectories and environmental changes in tropical lake systems.