A 150-year record of polycyclic aromatic compound (PAC) deposition from high Andean Cajas National Park, southern Ecuador

• Published in: The Science of the total environment 2018-04, Vol.621, p.1652-1663
• Main Authors: Bandowe, Benjamin A. Musa, Fränkl, Lea, Grosjean, Martin, Tylmann, Wojciech, Mosquera, Pablo V., Hampel, Henrietta, Schneider, Tobias
• Format: Article
• Language: English
• Subjects: Anthropocene; Azaarenes; Oxygenated PAHs; PAHs; Pollution history; South America
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2017.10.060

•Historical PAC depositional records are studied in lakes at low and high elevation.•Increases in fluxes of PAC in Ecuador started later (1950s) than in the northern hemisphere.•2–3 ring PAHs (diagnostic of biomass burning) constitute 30% of the total PAHs.•PAC depositions are 4–5 times higher at 3100m than at 4100m.•High precipitation & proximity to city explains high fluxes of PACs at 3100m. [Display omitted] The temporal profiles of polycyclic aromatic compounds (PACs) in lake sediments reflect past changes in emissions, transport and deposition of these pollutants and, thus, record natural and anthropogenic processes. We document fluxes of PACs [(polycyclic aromatic hydrocarbons (PAHs), oxygenated PAHs (OPAHs) and azaarenes (AZAs)] deposited in two tropical high-altitude lakes in the Cajas National Park (Ecuadorian Andes, 2°50′S, 79°10′W). In remote and high elevation Laguna Fondococha (4130m a.s.l.), the temporal fluxes of OPAHs and AZAs were similar to those of PAHs suggesting similar sources. A significant increase of PAC deposition after the 1950s reflects Ecuador's economic development. PAH fluxes were relatively low (∑27PAHs (without retene and perylene): 0.86–11.21ngcm−2yr−1) with a composition pattern typical for long-range atmospheric transport (high 9-fluorenone/fluorene ratios) and biomass burning (30% low molecular weight PAHs). PAHs diagnostic of high temperature combustion (industry, traffic) make up 20–25% of total PAHs. Perylene concentrations increase linearly with increasing sediment depth suggesting diagenetic in-situ production. At lower elevations (Laguna Llaviucu, 3140m a.s.l.) and closer to urban areas, PAC fluxes in the past decades were 4–5 times higher than in the remote high-elevation lake. Laguna Llaviucu also showed higher concentrations of high molecular weight pyrogenic PAHs and a greater diversity of AZAs. Individual OPAHs and AZAs reflect mainly combustion activities. In Laguna Llaviucu, which is at a lower elevation (3140m a.s.l.) and closer to the city, molecular ratios suggest short-range atmospheric transport and deposition of PACs. A very foggy climate (170 rainy days per year) with the precipitation maximum at 3500m removes PACs very efficiently (by wet deposition) from the atmosphere at very short distances from emission sources. This partly explains why L. Llaviucu shows higher fluxes of PACs than the higher elevation L. Fondococha. This study presents the first historical record of organic pollutants from envir