Sulfur geochemistry as a driver of trace element, rare earth and nutrient cycles in eutrophic estuarine sediment

[Truncated abstract] The biogechemical cycling of sulfur (S) may exert both beneficial and adverse impacts on estuarine sediment and water quality. Here, I investigate the influence of S geochemistry on trace element (metal and metalloid), rare earth element and nutrient behaviour within sediments from a eutrophic estuarine system in Western Australia. Iron monosulfides (mainly amorphous and tetragonal FeS) were high in these sediments, shown by elevated acid-volatile sulfide concentrations (AVS, median 158 μmol/g). Porewater iron was generally low (80% of total concentrations in approximately 70% of samples). Rare earth element concentrations, normalised against Post-Archaean Australian Shale, showed mid-REE (MREE) enrichments (median total MREE enrichment 1.30, median reactive MREE enrichment 1.44) and minor positive Ce anomalies (median total Ce anomaly 1.11, median reactive Ce anomaly 1.19).