This article was downloaded by: [University of Chicago Library] On: 21 June 2013, At: 11:39 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Environmental Technology Letters Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tent19 Mercury inputs into the Amazon Region, Brazil a W. C. Pfeiffer & L. Drude de Lacerda b a Lab. Radioisótopos, List, de Biofísica Carlos Chagas Filho, UFRJ, Rio de Janeiro, RJ, 21941, Brazil b Departamento de Geoquímica, UFF, Niterói, 24.210, RJ, Brasil Published online: 17 Dec 2008. To cite this article: W. C. Pfeiffer & L. Drude de Lacerda (1988): Mercury inputs into the Amazon Region, Brazil, Environmental Technology Letters, 9:4, 325-330 To link to this article: http://dx.doi.org/10.1080/09593338809384573 PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Environmental Technology Letters, Vol. 9, pp. 325-330 ©Publications Division Selper Ltd., 1988 MERCURY INPUTS INTO THE AMAZON REGION, BRAZIL W. C. Pfeiffer* and L. Drude de Lacerda** *Lab. Radioisótopos, List, de Biofísica Carlos Chagas Filho, UFRJ, Rio de Janeiro, RJ, 21941, Brazil **Departamento de Geoquímica, UFF, Niterói, 24.210, RJ., Brasil Downloaded by [University of Chicago Library] at 11:39 21 June 2013 (Received 11 September 1987; in final form 27 October 1987) ABSTRACT Mercury inputs into the Brazilian Amazon ecosystem due to goldmining activities are quantified based on data from various Brazilian Mineral and Environmental Agencies as well as field works. Total losses of Hg were estimated to be 1.32 kg Hg/kg Au from which 45% are released into rivers and 55% into the atmosphere. Total Hg input to the Amazon may contribute with up to 6% of the global anthropogenic Hg emissions to the atmosphere and the releases into the rivers are at the same order of magnitude as the inputs into the North Sea. INTRODUCTION Goldmining has become a major activity in the Brazilian Amazon Region involving presently circa 400 thousand men (Pig. 1). In all sites mercury is used in the extraction to amalgamate the fine gold particles (1). Although this activity exists at least for the last 10 years, only recently the potential threat of Hg contamination of the Amazonian ecosystems has been considered by local environmental authorities. Some attempts to evaluate the problem have been made (1, 2) however, lack of reliable informations, logistic difficulties and the inexistance of a central environmental authority for the majority of Amazon States have lead to some misinformations and a number of conflictive data of diflcult use for scientific purposes. The present paper aims to quantify Hg inputs into the Amazon ecosystems. Results are based on data from various Brazilian Mineral Production Authorities, local Environmental or Geological Survey Agencies and field work performed by the authors in various mining sites. Mercury is used in the process of gold complexing either manually or mechanically in all sites. Losses of mercury occurs during the gold amalgamation" process in pans and in riffles • (woden boxes with inclined stair-like bottoms covered with cloths) both along the river banks and on boats. In the pans process losses of metallic Hg reaches circa 5-10% of the used amount, while in the riffles it can be doubled (10-20%), entering the rivers directly as metallic Hg. The Au-Hg complex is gravimetrlcally separated and the excess of Hg is recovered by 325 squeezing the mixture in a cloths for reutillzation. The amalgam is then burnt to .separate the gold and the totality of Hg used Is lost into the atmosphere as Hg° vapour. The percentage from the initial mercury retained in the amalgam and therefore lost to the atmosphere is circa 20%. The initial amount used by the miner depends on the gold content estimated by eye. In general this relationship Au:Hg is 1:3 to 5 (W.C.P. and L.D.L., personal observations). Downloaded by [University of Chicago Library] at 11:39 21 June 2013 SCALE 1 17000 0 0 0 Sludv Ar»q: BRAZIL I Gotfmintng Areas FIGURE 1 I MAJOR GOLDMINtNG AREAS IN THE BRAZILIAN AMAZON REGION However, other losses can, and problaby due occur, during the process. During the recovery step, losses of metallic Hg are very common. In general the gold produced by this process still contains small quantities of Hg and are normally reburned by the gold dealer. Since high temperatures ( 40° C) are easily reached in the gold mining sites and boats, losses of Hg also occur by evaporation during the entire process. These losses are difficult to estimate but can easily account for about 5% of the initial Hg amount used in the process. Figure 2 presents a diagram 326 of the entire gold production process in the Amazon region through Hg- amalgamation and the estimated Hg losses to the environment. The final ratio of Au:Hg of 1:1.32 is probably very undersestiraated since rough field conditions difficult Hg recovery and miners frequently use Au:Hg ratios of 1:6 and even 1:10 (1). The Hg recovered in the process is normally reused only 3 or k times and then thrown away into the rivers. However, here we will use the 1:1.32 ratio as the best approach to reality even if in the future, optimization of the process would occur. Figure X Downloaded by [University of Chicago Library] at 11:39 21 June 2013 Gold production through Hg amalgamation in the Amazon rivers (Number in parenthesis are minimum estimated Hg losses for the production of 1 kg Au) Hg losses Gravimetric Au preconcentration X Concentrate Addition of Hg to pans or riffles, Au:Hg ratio = 1 : 4 Losses to rivers (0.40 kg) Au-Hg amalgam Squeezing of excess Vaporization to atmosphere (0.72 kg) Burning of Amalgam Hg recovery c.a. 70% Evaporation by handling and reburning (0.20 kg) Total losses: 1.32 kg Hq for 1 kg Au The second, and major difficulty in calculating Hg losses is the estimation of the actual gold production. Most of the produced gold is sold locally and send to non official gold dealers in Rio de Janeiro and Sao Paulo. This non- official market represents about 80% of total gold production and local gold dealers believe that only 10$ of the total gold production is sold to the government (L.D.L. per.obs). This would give a relationship between official data and the real production of circa 1:8 to 10. The official gold production in the Madeira River in 1985 was 1,471 Kg, as can be seen from Table 1 where official gold production data for the major mining areas in the Amazon region are presented. Local gold dealers and the Miners Union estimates this number around 14 to 17 tons. The local geologists from the 327 National Department between 8 and 10. of Mineral Production estimate this number Table 1 OFFICIAL GOLD PRODUCTION IN THE AMAZON REGION Mato Grosso 3 ,822 Roralma 65 4 ,925 Para-Goias Amapa 124 Para. 1 ,80-0 Downloaded by [University of Chicago Library] at 11:39 21 June 2013 Amazonas-Para. 52 1 ,359 Madeira Total: k g . y - 1 . (4) (Average between 1979 and 1982) (Value for 1981) (Average between 1979 and 1982) (Value for 1982) (Average between 1981 and 1982) (Value for 1981) (Average between 1979 and 1985) 12,147 Another way to approach the problem and reach a number as close as possible to reality is to calculate the minimum gold production necessary to mantain a dredge and i t s crew. Considering the equipment and the local difficulties, a minimum of 40 g of gold per day would be necessary. The mining activity last for circa 200 days a year, although some dredges carry on working even during the rainy season. In 1985 circa 1,400 boats were working in the Madeira River, which would give a total production of 11,200 tons of gold per year, close to the estimated real gold production in the area. Therefore a relationship between official and real production would be of 1:8. Although probably underestimated, this number is used in this paper to estimate Hg releases into the environment. Table 2 presents the estimates of Hg fluxes to the Table 2 ESTIMATES OF Hg FLUXES TO THE ENVIRONMENT Official Production Minimum estimated* Maximum estln Au production 12,147 72,882 97,176 Hg loss t o rivers Kg.y" 1 7,288 43,729 58,306 Hg loss t o Atmosphere 1 8,746 52,475 69,967 Total Hg loss Kg.y- 1 16,034 96,204 128,873 Kg.r *Based on the minimum Au production/Hg losses **Based on the maxium Au productlon/Hg losses 328 environment based on the official and the above estimated real gold production of the region. Prom this data one can see that Hg fluxes to the Amazon environment are at the order of 128 ton.y-1, from which about 55# enters the atmosphere as Hg° vapour and H% enters the rivers as metalic Hg. Table 3 Downloaded by [University of Chicago Library] at 11:39 21 June 2013 GLOBAL MERCURY EMISSION TO THE ATMOSPHERE COMPARED EMISSIONS IN THE AMAZONIAN GOLD MINING AREAS Source ton.y"1 Hg Author Natural Sources 2,700 6,000 (5) (6) Anthropogenic 630 2,000 (5) (6) Amazonian Goldralning Areas 50-70 WITH This study Based on this data, comparing Hg emission to the atmosphere in the Amazon goldmining areas with the most recent estimates of global Hg emissions to the atmosphere the Amazon area presently contributes with circa 1% of the total global emissions and with about 6% of the anthropogenic emissions. On the other hand Hg releases in the Amazon are already of the same order of magnitude as the Hg input into the North Sea (3) (Table 3 ) . The situation described above may represent a real threat of Hg contamination to the Amazonian environment, since if contamination of local fisheries occurs, a great portion of local population would be affected. On the other hand, the study Hg biogeocheralsty in this region should give important insights to the understanding of the global Hg cycle. ACKNOWLEDGMENTS The authors wich to thank the Federal University Rondonia, Ene G. da Silveira, Ana A. P. Boischio and Luiz Femandes for local support. This research was supported SUDECO, FIPEC, FINEP and CNPq. of C. by REFERENCES (1) Mallas, J. & Benedicto, N. Mercury and Goldmining Brazilian Amazon. Ambio. 15: 248-249 (1986). in the (2) UNIR. I Seminário sobre contarainação por mercúrio no Rio Madeira. Univ. Fed. Rondônia. Porto Velho (in press) (1986). (3) Salomons, W. & Förstner, V. Metals in the hydrocycle. Springer Verlag, Berlin, 249 p. (1984). 329 1 (4) DNPM. Garimpos do Brasil. Dept. Nac. Prod. Mineral Publ. Avulsa n°. 5, Brasilia, DP,, 301 p. (1983). (5) Pacyna, J.M. Atmospheric trace elements from natural and anthropogenic sources, In: Nriagou, J.O. and Davidson, C.I. (eds.). Toxic Metals in the Atmosphere. Wiley. New York (1984). Downloaded by [University of Chicago Library] at 11:39 21 June 2013 (6) SCOPE. I International SCOPE Metals Cycling Workshop. Rapporteur's Report on Mercury. Sclent. Comm. Problems of the Environment. Toronto. 16 p. (1985). 330