Geochemical records in sediments of a tropical estuary (Southeastern coast of Brazil)

摘要: The Piraque-Acu and Piraque-Mirim estuarine system (PAPMES) is considered to be a hydrologically unaltered estuary; however, several human activities including introduction of pollutants may have contributed changes in this system. We studied hydrocarbons, major elements (Al, Mg, Fe Mn), trace (As, Ba, Cd, Co, Cr, Cu, Li, Ni, Pb, V Zn), Corg./Ntotal ratio, δ13C δ15N stable isotopic composition organic matter assess the natural anthropogenic depositional record three sediment cores dated by 210Pb geochronology. sediments showed strong terrestrial C3 plant contribution input rivers (−29.2≤δ13C≤−25.1‰; 2.1≤δ15N≤5.3‰; 23.3≤Corg./Ntotal≤53.9), with higher phytoplankton influence downstream (−29.3≤δ13C≤−20.7‰; 0.4≤δ15N≤6.6‰, 15.4≤Corg./Ntotal≤34.4). Greater n-alkane concentrations typical plants (nC27, nC29, nC31) confirmed inputs. There was no indication contamination petrogenic sources, but relatively high amounts 17β(H), 21β(H) 21α(H) terpanes, indicate possible association biogenic (bacteria). distributions were associated lithogenic iron manganese oxides/hydroxides. Although there little evidence enrichment direct activity, influenced deforestation for charcoal production which occurred between 1950s 70s, exposing soils weathering erosion.