In this study, we evaluated the pollution history by metals over the twentieth century in an urban reservoir (Garças Reservoir, Metropolitan Region of São Paulo, Southeast Brazil) by the paleolimnological approach. The concentrations of eight metals (Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) were determined in a 210Pb-dated sediment core (~ 100years of information). Metal's enrichment and pollution degree were assessed using the Consensus-Based Sediment Quality Guidelines (CBSQG), enrichment factor (EF), Geoaccumulation Index (Igeo), and Potential Ecological Risk Index (RI). Local background values were used to calculate metal enrichment indexes. Principal component analysis (PCA) was performed to analyze metal variability across samples. Overall heavily to extremely contamination was determined mainly after ~ 1975, particularly to Pb, Ni, and Fe, whereas moderately to heavily Cu, Zn, Mn, and Co pollution levels were detected by Igeo. Very high EF values (> 2 ≤ 24) were found, suggesting mainly anthropogenic sources for these elements. However, Pb concentrations declined considerably towards the top of the core, reflecting the prohibition of leaded gasoline since 1986. The long-term metal enrichment in the Garças Reservoir was related mainly to vehicular traffic emissions and industrial activities. Further anthropogenic stressors such as untreated sewage inputs and surface runoff contributed significantly to metal pollution, particularly from the late 1950s, reflecting the most populous region socio-economic development in Brazil.
Read full abstract