Scholarly record
ASSESSMENT OF THE POLLUTING POTENTIAL OF COMMUNITY TAILINGS IN THE ZARUMA-PORTOVELO MINING DISTRICT, ECUADOR
Abstract
Inadequate management of mining tailings represents a major environmental challenge in Latin America, particularly in mining districts where these deposits are often located near communities and water bodies, increasing the risk of environmental contamination. This study assesses the polluting potential of a community tailings dam located in the Zaruma–Portovelo mining district, one of the country’s most important gold-mining areas. Ten tailings samples were collected and subjected to physicochemical and mineralogical characterization. Concentrations of As, Cd, Cu, Cr, Ni, Pb, and Zn were determined by X-ray fluorescence (XRF). The contamination index (IC) was calculated to evaluate the degree of contamination, and leaching tests were conducted to assess the mobility of potentially toxic elements (PTEs) and their environmental impact. Results showed acidic conditions (pH<3) and high concentrations (in mg/kg) of As (200–8300), Cu (472.61–1600), Pb (200–3300), and Zn (600–11300). These PTEs are linked to sulfide minerals, particularly pyrite, whose oxidation promotes secondary sulfates such as jarosite and gypsum. Quartz and micas dominate the gangue. The IC indicates very high contamination (27<IC<313), mainly due to As and Pb. Leaching tests revealed As, Cd, Cu, and Zn above Ecuadorian limits, indicating significant mobility and environmental risk. Overall, the tailings dam is an active contamination source, highlighting the urgent need for monitoring and sustainable management strategies in mining areas of Ecuador. Future work should integrate hydrogeochemical modeling, long-term monitoring, and community-based risk management to mitigate impacts and support responsible mining practices in vulnerable regions with legacy tailings deposits.
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References20
B. Salgado-Almeida et al., "Assessment of Environmental Pollution and Risks Associated with Tailing Dams in a Historical Gold Mining Area of Ecuador," Resources, vol. 13, no. 8, pp. 1-16, 2024, DOI: 10.3390/resources13080105.
B. G. Marshall, M. M. Veiga, H. A. M. da Silva, and J. R. D. Guimarães, "Cyanide Contamination of the Puyango-Tumbes River Caused by Artisanal Gold Mining in Portovelo-Zaruma, Ecuador," Curr. Environ. Heal. reports, 2020, DOI: 10.1007/s40572-020-00276-3.
P. C. Velásquez-López, M. M. Veiga, B. Klein, J. A. Shandro, and K. Hall, "Cyanidation of mercury-rich tailings in artisanal and small-scale gold mining: Identifying strategies to manage environmental risks in Southern Ecuador," J. Clean. Prod., vol. 19, no. 9-10, pp. 1125-1133, 2011, DOI: 10.1016/j.jclepro.2010.09.008.
G. Schudel et al., "An investigation of mercury sources in the Puyango-Tumbes River: Using stable Hg isotopes to characterize transboundary Hg pollution," Chemosphere, vol. 202, pp. 777-787, 2018, DOI: 10.1016/j.chemosphere.2018.03.081.
G. Schudel et al., "Mercury isotopic signatures of tailings from artisanal and small-scale gold mining (ASGM) in southwestern Ecuador," Sci. Total Environ., vol. 686, pp. 301-310, 2019, DOI: 10.1016/j.scitotenv.2019.06.004.
J. D. Appleton, T. M. Williams, H. Orbea, and M. Carrasco, "Fluvial contamination associated with artisanal gold mining in the Ponce Enriquez, Portovelo-Zaruma and Nambija areas, Ecuador," Water. Air. Soil Pollut., pp. 19-39, 2000.
A. O. Gonçalves, B. G. Marshall, R. J. Kaplan, J. Moreno-chavez, and M. M. Veiga, "Evidence of reduced mercury loss and increased use of cyanidation at gold processing centers in southern Ecuador," J. Clean. Prod., vol. 165, pp. 836-845, 2017, DOI: 10.1016/j.jclepro.2017.07.097.
P. C. Velásquez-López, M. M. Veiga, and K. Hall, "Mercury balance in amalgamation in artisanal and small-scale gold mining: identifying strategies for reducing environmental pollution in Portovelo-Zaruma, Ecuador," J. Clean. Prod., vol. 18, no. 3, pp. 226-232, 2010, DOI: 10.1016/j.jclepro.2009.10.010.
M. Lemos et al., "Mineralogical and geochemical characterization of gold mining tailings and their potential to generate acid mine drainage (Minas gerais, brazil)," Minerals, vol. 11, no. 39, pp. 1-16, 2021, DOI: 10.3390/min11010039.
C. Zhang et al., "Heavy metal pollution caused by cyanide gold leaching: a case study of gold tailings in central China," Environ. Sci. Pollut. Res., vol. 28, no. 23, pp. 29231-29240, 2021, DOI: 10.1007/s11356-021-12728-w.
F. Guzmán-MartÃnez, J. C. Arranz-González, M. F. Ortega, M. J. GarcÃa-MartÃnez, and V. RodrÃguez-Gómez, "A new ranking scale for assessing leaching potential pollution from abandoned mining wastes based on the Mexican official leaching test," J. Environ. Manage., vol. 273, no. 111139, 2020, DOI: 10.1016/j.jenvman.2020.111139.
N. S. Nemeş, D. Kržanović, M. Stojanović, A. Negrea, P. Negrea, and C. Muntean, "Establishing a baseline for environmental risk assessment: a systematic review of the disposal of mining tailings in the crossborder region Romania - Serbia," J. Trace Elem. Med. Biol., vol. 93, 2026, DOI: 10.1016/j.jtemb.2025.127802.
J. C. Arranz-González, F. Guzmán-MartÃnez, A. Tapia-Téllez, S. Jiménez-Oyola, and M. J. GarcÃa-MartÃnez, "Polluting potential from mining wastes: proposal for application a global contamination index," Environ. Monit. Assess., vol. 194, no. 10, p. 792, 2022, DOI: 10.1007/s10661-022-10433-w.
A. Kabata-Pendias, Trace elements in soils and plants: Fourth edition, 4th ed. Boca Raton: CRC Press, 2010.
P. Hageman, "U.S. Geological Survey field leach test for assessing water reactivity and leaching potential of mine wastes, soils, and other geologic and environmental materials," in Laboratory Methods ans Analysis, Reston, Virginia: U.S. Geological Survey, 2007, p. 14.
MAE-TULSMA, "Texto Unificado de Legislación Secundaria Medio Ambiental. Ministerio de Ambiente de Ecuador.," Quito, 2015.
D.W. Blowes, C.J. Ptacek, J.L. Jambor, C.G. Weisener, D. Paktunc, W.D. Gould, and D.B. Johnson, 11.5 - The Geochemistry of Acid Mine Drainage, Treatise on Geochemistry, pages 131-190, 2th ed. Elsevier, 2014. DOI: 10.1016/B978-0-08-095975-7.00905-0.
B. Lottermoser, Mine Wastes, Sprynger, 3th ed. 2010.
J.L. Jambor and D.K. Nordstrom, C.N. Alpers, "Metal-sulfate Salts from Sulfide Mineral Oxidation", Rev. Mineral. Geochem, vol. 40, p.303-350, 2000, DOI: 10.2138/rmg.2000.40.6.
D.K. Nordstrom, "Mine waters: acidic to circumneutral", Elements, vol. 7, p. 393-398, 2011, DOI: 10.2113/gselements.7.6.393.[