Spatial controls on riverbed sediment chemistry in three anthropogenically modified tropical mountainous watersheds

Tropical mountainous rivers transport a disproportionate amount of sediment to the global ocean. While these systems also deliver sediment-related pollutants (i.e., metals) coast, potential accumulation metal contaminants within has been largely unexplored. This study analyzed trace concentrations fine riverbed (< 0.63 µm) collected from Rio Loco, Yauco and Guamaní in Puerto Rico. A total 17 samples were June 2019 (~ 21 months following Hurricane Maria) watersheds. Metal (Al, Ba, Cd, Cu, Cr, Fe, Mn, Ni, Sb, Sn, U Zn) quantified with acid digestion inductively coupled plasma mass spectrometry. Strong positive correlations found between Pb, Sb Sn (ravg > 0.60, p < 0.05) as well Cr Ni 0.81, 0.05). comparison land cover revealed statistical relationships Zn developed agricultural land. Between 7 50% exhibited enrichment factor values indicative moderate significant levels contamination (EF 2) for each metal. Additionally, several exceeded consensus-based threshold effect probable values. Altogether, data confirm that metals do accumulate tropical watersheds can be at impact freshwater ecosystems. These elevated periodic flushing events, regularly supported by hurricanes, suggest threat nearshore ecosystems such coral reefs.