Background

The Danish Consortium of Appelglobal (www.appelglobal.com) and its partners (www.ellplatek.com and www.flsmidth.com) recently received generous funding grant from Danish Ministry of Environment for a one-year mercury abatement and clean-up pilot project in Honduras, where Honduran

small-scale gold miners’ gold processing activities annually release over 20 tons of mercury into watersheds that empty into economically important coastal waters. The Consortium, in collaboration with the

HONDURAN MINISTRY OF ENVIRONMENT, ENERGY AND MINES (MiAmbiente), will develop the pilot cleanup project on the country’s Pacific coast, where several thousand small-scale miners working in the El Corpus municipality (Figure 1) have been releasing over

Figure 1: Map showing the region around Gulf of Fonseca and the location of the study area, El Corpus.

five tons of mercury per year into the Choluteca watershed, which empties into the Trinational international Gulf of Fonseca waterway. Coastal wetlands surrounding the Gulf are biologically productive and yield shrimp, clams and scalefish that not only provide the local population with food, but they are also the lifeline for economically important seafood export products for Honduras, as well as Nicaragua and El Salvador. Three of the five shrimp species captured offshore use the Gulf as a nursery area where they grow rapidly. However, high mercury concentrations have already been documented in rivers (Urioste-Daza 2014) and coastal wetlands and fish at the mouth of the Choluteca River (NOAA 2002). In addition to supporting the present pilot project, Denmark is a financial contributor to the World Bank’s PROBLUE Healthy Oceans initiative (https://www.worldbank.org/en/programs/problue), and the Gulf of Fonseca is one of the global intervention sites for the program focusing on sustainable fisheries.

However, unless the levels of mercury polluting the Gulf and its wetland nursery grounds are reduced, the PROBLUE program, as well as seafood producers, exporters and consumers of seafood products face human health risks, and threats to seafood export economies of the three countries bordering the Fonseca Gulf. Another serious threat from the continuous release of mercury into environment arises from the infiltration of mercury into coastal aquifers, which are the main drinking water supply for the population living on the Pacific coast.

The Pilot Project

Appelglobal and its partners will test two approaches for removing and eliminating mercury in the small-scale gold mining areas of the El Corpus region using the following operational framework: i) Removal of mercury from heavily polluted tributaries within the Choluteca Watershed; and ii) Introduction of an effective mercury-free gold extraction to the area and teaching miners how to apply it in their work. A third aspect of the pilot project is to establish geochemical baselines for mercury concentrations in Choluteca watershed and the Fonseca Gulf.

1. Mercury Removal from Rivers and Tributaries

Mercury from river sediments from small rivers of the Choluteca watershed will be extracted using a combination of methods, which include the mechanical concentration of the heavy mineral fraction of river sediments (Figure 2) and chemical extraction of mercury by running the concentrate over coated copper plates. The Consortium could carry out a pilot project with the capacity to clean up more than 20 tons of mercury per hour in river sediments.

Unlike most Hg recovery initiatives, the recovered mercury from the Honduran rivers will be packaged and shipped out of the country to Batrec Industrie in Switzerland, where it will be immobilized (as cinnabar) and deposited it in abandoned deep salt mines in Germany.

Fig.2. Canadian produced classifier of placer deposits.

2. The Mercury-free small-scale gold mining method

The mercury-free gold extraction for small-scale gold miners was developed 40 years ago in the Philippines and has been used by thousands of miners in the Benguet province ever since (Fig. 3)

 The mercury-free gold extraction recovers more gold than using mercury for gold extraction, and the miners save money by avoiding mercury expenses. Appelglobal has, with a team of small-scale gold miners from Benguet, taught the mercury-free gold extraction method on three continents and now intends, as a part of the current project in Honduras to introduce the method to small- scale miners in El Corpus http://youtu.be/X6Sawj0HyF0.

3. Establishing Geochemical baselines

Fig. 3. The mercury-free gold extraction method.

Riverine sediment samples will be collected in triplicate from at least thirty sites within the gold mining areas throughout the Choluteca watershed, as well as from control areas lacking anthropogenic mercury inputs. To the extent possible, sites will include areas sampled by previous studies carried out between one and two decades earlier. In addition to measuring Hg concentrations, reference elements like Fe, AL, Mn or Li will be measured to help address the‘grain size effect’, as well as to distinguish between natural and anthropogenic HG contributions (see Ryan and Windom 1989). All samples will be processed by a Canadian lab using internationally accepted standard analytical methods and split with Honduran laboratories.

References

Appel, P.W.U and Esbensen, K. H. (2019) Reducing global mercury pollution with simultaneous gold recovery from small-scale mining tailings. TOS forum issue 9. https://www.impopen.com/tosf- toc/19_9.

NOAA (2002). Hurricane Mitch Reconstruction/Gulf of Fonseca Contaminant Survey and Assessment. 52 pp.

Ryan, J. and H. Windom (1988). A Geochemical and Statistical Approach for Assessing
Metal Pollution in Coastal Sediments. In: Metals in Coastal Environments of Latin America, Seeliger, U. and L. Lacerda (eds.). Springer-Verlag Berlin Heidelberg 1988

Urioste-Daza, S. (2014) Diagnóstico de calidad de agua en dos quebradas influenciadas por actividad minera en el municipio de El Corpus, Choluteca. MS Thesis. Zambrano University.