Evidence of reduced mercury loss and increased use of cyanidation at gold processing centers in southern Ecuador

Due to the strong price of gold, the number and capacity of gold processing centers in Portovelo-Zaruma in southern Ecuador have increased considerably in recent years. In turn, this has caused increasing environmental pollution of waterbodies with cyanide, mercury and other heavy metals. This paper provides an assessment of gold production methods at 52 processing centers in 2013 and 20 in 2015, including estimations of mercury (Hg) losses and releases, cyanide use and tailings management. Due to an increase in the price of mercury and other government initiatives to reduce and eliminate Hg use, there is evidence of a shift from amalgamation processes to increased employment of cyanidation techniques. It was estimated that the 87 processing centers released 1.9 million tonnes/a of tailings in 2015, including 2033 tonnes/a of cyanide and 222 kg/a of Hg. Furthermore, it was estimated that the burning of gold amalgams released 303 kg/a of Hg to the atmosphere. Although mercury use showed a 60% reduction from 2013 to 2015, while cyanidation processes increased 30% over the same time period, more needs to be done, as 65% of the centers still use Hg amalgamation to extract gold. (C) 2017 Elsevier Ltd. All rights reserved.