278 Understanding Temporal Dynamics in Hydrogeochemistry and Sedimentary Processes in Estuarine Environments

This session explores temporal changes in estuarine environments with respect to water chemistry and sediment inputs. Effects of evolving physiochemical properties and isotopic composition of water, as well as the geochemical attributes of sediments on the environment will be presented.

Wednesday, 22 October 2025
1:30 PM - 5:30 PM
HBGCC, 213AB

Tracing Anthropogenic Signatures in a Tropical Estuary: Depth-Resolved Heavy Metal Co-Variation in the Wouri Estuary, Cameroon

Paper number: 278-6
Program: Technical Sessions
Time: 3:00 PM – 3:15 PM

Authors

Abstract

In estuarine systems like the Wouri Estuary, where tidal flats are influenced by industrial, agricultural, and urban activities, distinguishing between anthropogenic and geogenic sources of heavy metals is often challenging due to overlapping inputs. This study investigates historical trends in heavy metal contamination using a 78 cm sediment core collected from a tidal flat in the Wouri Estuary, Cameroon. Elemental concentrations were analyzed at 5 cm intervals using wavelength-dispersive X-ray fluorescence (WDXRF) to assess enrichment patterns and infer the sources of contamination.

Enrichment factor (EF) analysis of elemental concentrations revealed moderate to high enrichments (2 < EF < 40) of arsenic (As), cobalt (Co), antimony (Sb), and molybdenum (Mo) throughout the core, with zinc (Zn) and uranium (U) enrichment confined to surface section of the sediment core. Distinct co-enrichment and co-variation patterns emerged in the upper 20 cm, where As–Co and Zn–Mo–Sb formed two independent, strongly correlated groups. These patterns were absent or weak in deeper sediments (20–78 cm), suggesting differing enrichment mechanisms over time.

Correlation analyses of enrichment factors showed marked increases in elemental associations near the surface: the As–Co correlation improved from R² = 0.39 at depth to R² = 0.99 at the surface; Sb–Zn from R² = 0.16 to R² = 0.96; and Mo–Zn from R² = 0.00 to R² = 0.99. Spearman correlation and principal component analysis corroborated these depth-dependent trends. Deeper sediments are interpreted as predominantly influenced by geogenic processes, while surface layers reflect more recent anthropogenic inputs. Activities such as metal smelting, port operations, and agriculture likely contributed to the As–Co signal, while vehicular emissions, lubricant waste, and coal combustion residues are probable sources of the Zn–Mo–Sb association.

While heavy metal enrichment in tropical estuaries is well documented, this study uniquely demonstrates that changes in elemental co-variation with depth can serve as a diagnostic tool for isolating anthropogenic contamination. These findings underscore the complex and layered nature of pollution in the Wouri Estuary, highlighting the value of co-variation analysis in tracing contaminant sources in dynamic coastal environments.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413981

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