2015-Sustainable Industrial Processing Summit
SIPS 2015 Volume 4: Meech Intl. Symp. / Mining Operations
| Editors: | Kongoli F, Veiga MM, Anderson C |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2015 |
| Pages: | 275 pages |
| ISBN: | 978-1-987820-27-0 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Mercury and Heavy Metal Origin and Contamination of the Puyango-Tumbes River System, Ecuador
Robert Kaplan1; Marcello Veiga1; Carolina Gonzalez-Mueller2; Colon Velasquez-Lopez3; Luis Granda3; Leonaor Leonor Rivera2;1UBC-MINING, Vancouver, Canada; 2UNIDO, Geneva, Switzerland (Confederation of Helvetia); 3INIGEMM, Quito, Ecuador;
Type of Paper: Regular
Id Paper: 450
Topic: 4
Abstract:
Worldwide Artisanal Gold Miners (AGM) use significant amounts of mercury, accounting for more than 30% of all industrial uses. UNEP (2013) estimates that AGM is emitting and releasing 1400 tonnes/a of mercury.
Processing centres were established in the 1990s in Portovelo, Ecuador to provide miners with gold extraction services. Miners amalgamate a portion of the gold, but centre owners retain the residual Hg-contaminated tailings using cyanidation to recover the remaining 60 - 80% of the gold.
Based on surveys of 52 out of 87 centres, 1.1-1.85 tonnes of metallic mercury contained in over 880,000 tonnes of tailings are discharged into the Puyango-Tumbes River annually. This mercury represents a loss of approximately 14% of the total mercury used by AGM/a in the region. An additional 19% of the mercury is lost when amalgam is evaporated. An average of 5.7 tonnes of cyanide per month (a total of over 4,500 tonnes/a) is consumed by approximately 68 centres.
In total, 39 river-bank sediments and 31 soils were sampled. Mercury contamination in sediment exceeded the CCME TEL - Canadian Council of Ministers of the Environment threshold effect level in 23 sites. The highest level detected was 30.79 mg/kg in sediment; all soil samples were below 2 mg/kg. An abandoned tailings pit recorded a mercury level of 744.2 mg/kg. Elevated mercury levels in sediment were detected 160 km distant from source, demonstrating that AGM-discharged mercury can flow long distances attached to particulate matter.
Arsenic, Cadmium, Copper, Lead and Zinc levels in water, sediment and soil samples were also found to be above safe standards at many sites. In sediments, Arsenic levels were exceeded at 31 sites, the highest recorded was 12,580 mg/kg; Cadmium – 8 sites (<422.2 mg/kg); Copper – 36 sites (<3,741 mg/kg), Lead – 12 sites (<2,468 mg/kg); and Zinc – 22 sites (<6,184 mg/kg).
A total of 25 fish samples were taken from 3 sites in the river system 45 to 93 km from the source. Dorado fish recorded mercury levels ranging from 0.02 to 0.99 mg/kg; Aquila fish (a bottom feeder) had levels from 0.18 to 0.98 mg/kg.
KEYWORDS: Ecuador, Puyango-Tumbes, mercury, ASGM, AGM, miners, mining, heavy metals, cyanide, water, sediments