250-year records of mercury and trace element deposition in two lakes from Cajas National Park, SW Ecuadorian Andes

Abstract

Historical records of trace elements in lake sediments provide source-to-sink information about potentially toxic pollutants across space and time. We investigated two lakes located at different elevations in the Ecuadorian Andes to understand how trace element fluxes are related to (i) geology, (ii) erosion in the watersheds, and (iii) local point sources and atmospheric loads. In remote Lake Fondococha (4150 m a.s.l.), total Hg fluxes stay constant between ca. 1760 and 1950 and show an approximately 4.4-fold increase between pre-1950 and post-1950 values. The post-1950 increase in fluxes of other trace elements (V, Cr, Co, Ni, Cu, Zn, As, Cd, and Pb) is lower (2.1–3.0-fold) than for Hg. Mostly lithogenic sources and enhanced soil erosion contribute to their post-1950 increase (lithogenic contribution: > 85%, Hg: ~ 58%). Average post-1950 Hg fluxes are approximately 4.3 times higher in peri-urban Lake Llaviucu (3150 m a.s.l.) than in the remote Lake Fondococha. Post-1950 fluxes of the other trace elements showed larger differences between Lakes Fondococha and Llaviucu (5.2 < 25–29.5-fold increase; Ni < Pb–Cd). The comparison of the post-1950 average trace element fluxes that are derived from point and airborne sources revealed 5–687 (Hg–Pb) times higher values in Lake Llaviucu than in Lake Fondococha suggesting that Lake Llaviucu’s proximity to the city of Cuenca strongly influences its deposition record (industrial emissions, traffic, caged fishery). Both lakes responded with temporary drops in trace element accumulations to park regulations in the 1970s and 1990s, but show again increasing trends in recent times, most likely caused by increase in vehicular traffic and openings of copper and gold mines around Cajas National Park.

Scientific Research in Ecuador: A Bibliometric Analysis

“…This cluster focuses on various topics related to biodiversity in the national territory (especially in the Andes, Galapagos, and Amazonia) and the resulting impact of climate change. Some researchers have considered these effects on biodiversity [142,143], on the biological quality of water in rivers and lakes [144][145][146], soil moisture deficit [147], land use and land cover [148][149][150]. As well as the retreat of the glaciers, the decline of snow and ice in the Andes [151][152][153].…”

Paleolimnological responses of Ecuadorian páramo lakes to local and regional stressors over the last two millennia

“…Today, these areas are attractive tourist destinations for nature treks, sport fishing, and camping. These tourist activities have resulted in changes in vegetation cover, introduction of invasive species, and pollution of waterbodies (Barros et al 2015;Bandowe et al 2018;Schneider et al 2021).…”

A Tropical Cocktail of Organic Matter Sources: Variability in Supraglacial and Glacier Outflow Dissolved Organic Matter Composition and Age Across the Ecuadorian Andes

“…However, atmospheric deposition of microplastics has been noted on Antisana (proximate to sample sites AN1S1, AN1S2, and AN1‐4; Cabrera et al., 2022). Additionally, a large fraction of mercury concentrations (∼40%) in high altitude lake sediments (Cajas National Park, southwest Ecuador) are believed to be from atmospheric deposition, and a component of which is likely derived from fossil fuel combustion (Schneider et al., 2021). As such, anthropogenic aerosols are likely to reach the surface of Ecuadorian glaciers via long range atmospheric transport, and may have contributed aged, aliphatic compounds to supraglacial and outflow stream DOM composition.…”