Research ArticleENVIRONMENTAL STUDIES

Artificial lake expansion amplifies mercury pollution from gold mining

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Science Advances  27 Nov 2020:
Vol. 6, no. 48, eabd4953
DOI: 10.1126/sciadv.abd4953
  • Fig. 1 Comparison of historical (1987; Landsat) and current [2020; Google Earth from Maxar, Airbus, and Centre National d’Etudes Spatiales (CNES)] landcover for mining-affected locations.

    Locations along the Colorado River (left), adjacent to the Inambari River (middle), and in the Inambari headwaters (right) show the proliferation of mining ponds and deforestation. Specific locations can be seen in fig. S1. Top and bottom panels cover the same spatial extent. Note that in 1987, the Inambari area shown contained 100% forest cover.

  • Fig. 2 Spatial and temporal distribution of surface water extents in Madre de Dios, Peru.

    (A) Map of the study area with historical surface water extent. Colors represent the first year a given area was detected as water. Historic river channels that predate satellite observations appear in yellow, while recent morphological changes and the expanse in mining ponds appear in magenta. (B) Time series of normalized surface water extent broken down by watershed and lentic versus lotic environments. All water pixels connected to the main river channel for a given year are considered lotic; water pixels isolated from the main river channel are considered lentic. Base map imagery from Google Earth (2020, from Landsat/Copernicus). See https://sntopp.users.earthengine.app/view/mdd-hydroscape-explorer for enhanced visualization of hydroscape changes. Sampling locations for mercury analysis are shown in fig. S1.

  • Fig. 3 Concentration and distribution of water column total Hg (THg), methyl Hg (MeHg), and percent Hg as MeHg across water bodies upstream and downstream of artisanal gold mining in Madre de Dios, Peru.

    Right column distribution data are observations shown in order of decreasing Hg values to highlight clustering among sampling locations. Letters represent statistically significant differences between values at each location according to a Kruskal-Wallis analysis of variance on ranks, followed by Dunn’s test.

  • Fig. 4 Global examples of landscape lentification from three countries heavily affected by ASGM.

    The left column shows the relative lentic surface area of the study country (in purple) compared with the heavily mined basins in Peru. The right column shows the historic water masks of the study country with colors denoting the first year a given pixel was classified as water. The main channel in the Offin River is smaller than 30 m wide and below the remote sensing detection threshold; therefore, only surrounding mining ponds are measured. Black areas in the figures on the right represent pixels classified as land throughout the study period.

Supplementary Materials

  • Supplementary Materials

    Artificial lake expansion amplifies mercury pollution from gold mining

    Jacqueline R. Gerson, Simon N. Topp, Claudia M. Vega, John R. Gardner, Xiao Yang, Luis E. Fernandez, Emily S. Bernhardt, Tamlin M. Pavelsky

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