GEOCHEMISTRY AND MINERALOGY OF SEDIMENT CORES AT THE RIVERINE NEXUS OF A DENSELY POPULATED AREA AND A TROPICAL RAINFOREST

Sediment cores serve as repositories of information on local environmental conditions such as those affected by land use, climate change, and pollution. Three sediment cores along the Rio Espiritu Santo tropical riverine-estuarine system on the island of Puerto Rico were collected and analyzed to determine mineralogy, bulk composition, organic content, and trace metal chemistry. Trace metals were analyzed by inductively coupled plasma mass spectrometry to apply as proxies of anthropogenic impact. Metals of interest included: Pb, Zn, Cd, Ni, Cu, Cd and Mn. X-ray diffraction and grain-size analyses were conducted to determine clay mineralogy and particle-size distribution in sediment samples. Percent organic matter was also computed to determine the distribution of organic matter down core. Fine-sized particles such as silts and clays, types of clay present and percent organic matter may influence the mobility and behavior of trace metals in aquatic environments. Preliminary results indicate that this transitional fluvial-marine environment was not faced with a serious metal pollution at the time of collection. We will report on the spatial patterns and geochemical profiles within each core and identify possible environmental controls on their dispersal.