Peer ReviewedPostprint (published version

Alfonso Abella, María Pura

Esbri, José Maria

García-Noguero, Eva María

Higueras Higueras, Pablo Leon

Palacios Ubach, Sílvia

English

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San Juan de Chorunga San Martin y Misky MERCURY POLLUTION CAUSED BY ARTISANAL GOLD MINING IN THE OCOÑA RIVER VALLEY, PERÚ  S. Palacios1,2, P. Alfonso1, P.Higueras2, J.M. Esbrí2, E.M. Garcia-Noguero2   1 Dept. Enginyeria minera i recursos naturals, Universitat Politècnica de Catalunya. Av. De les Bases de Manresa 61-73, 08242, Manresa, Spain 2 Instituto de Geologia  Aplicada, Universidad de Castilla la Mancha, Plaza de Manuel Meca, 1, 13400 Almadén, Spain   Hg Dissolved mg/ l Hg Total mg/l pH Temp. ºC Ñ 1 34,20 61,10 7,71 18,4 Ñ 2 20,50 27,20 7,69 17,3 Ñ 3 0,20 1,20 7,97 17,5 Ñ 4 0,50 0,90 7,30 17,7 Ñ 5 0,30 0,80 8,73 19,7 Ñ 6 0,20 0,70 7,03 18 Ñ 7 0,10 0,40 7,63 16,8 Ñ 8 0,02 0,07 8,18 21,7 Ñ 9 0,01 0,01 8,18 21,2 Ñ 10 0,01 0,01 8,34 19,6 Ñ 11 0,01 0,01 8,13 20,5 Ñ 12 0,02 0,02 8,12 22,2 Introduction In the Ocoña river basin several artisanal mining settlements occur. this valley is located in the Arequipa department, South of Perú (Fig. 1). The main deposits are Posco-Misky, San Cristóbal, Carro Rico and San Juan de Churunga.   This is a gold mining activity. In most of these mining settlements, miners work takinmg in advance old mines that have previously been used by mining interprises and what they leave because low ratability. In these places gold grades are high up to 60 g/t, but gold is found in narrow veins (Fig. 2), and then, reserves are small.  The recoving of gold in these mining activities is performed as an amalgam with mercury. Gold-containing mineral is grinded using mills, in Peru called “quimbaletes” (Fig. 3) toghether with mercury. The gold-mercury amalgam is recovered directy using the hands without protection (Fig. 4).   Finally amalgam is burned for obtaining pure gold. In some places quimbaletes are located outside the place of residence as in Posco-Misky, where they have a special pace 5 km far from the population, called San Martin, where quimbaletes work daily, where each processes 30 kg / day of material, with a consumption of kg of mercury, 20% of the mercury that is not recovered is deposited into the environment. According to Nriagu (1994), between 60-65% of mercury is deposited in the atmosphere creating serious environmental pollution.  The present study aims to avaluate the pollution of mercury used to gold recovering in the Ocaña river valley. Results and discusion Different analyzes were conducted in two universities: Universitat Politecnica de Catalunya (Manresa) and the University of Castilla la Mancha (Almaden). Its purpose is to measure the concentration of mercury in different meday.  In total 12 samples were analyzed for water, where there is a very high mercury concentrations in the first three samples, with values greater than 1 mg / l, high values in the samples and low values Ñ-4/5/6 the remaining samples (Table 1). The pH varied between 7.03 and 8.73, therefore considered that the water is acidic. Water temperatures are between 16.2 to 22.8 °C. The climate of the area is mountainous, cold at night and hot during the day, so the water temperatures can reach different values, depending on the time of day of sampling.  According to the World Health Organization, the maximum allowable limit for drinking water is 1 g/l. Sampled water is not used for human consumption, but or personal hygiene, laundry or clean kitchen utensils. It is also used for consumption of animals. By analyzing data on hair, the concentration range of total mercury is 0.62 µg/g  - 6.43 µg/g, with an average of 2.78 µg/g. According occupations, people that works in quimbalete has the higher values obtained 4,141 µg/g, followed by students 1.98 µg/g, 1.85 µg/g mercury vendors / g, vendors sometimonth quimbalete mercury and 1.66 µg/g, cooks 0.83 mg / g babies finally 0.72 µg/g. As for gender, women get higher values than in the case of males, 2.95 mg / g and 2.64 mg / g respectively. The 89.5% of the population, exceed the total mercury dose according to WHO (World Health Organization), as the value set is 1 µg/g. Only two out of 19 samples have values below this threshold (Table 2).  The population of Almaden, southern Spain where the mercury mines located, are required hair mercury amounts varying from 0.20 to 9.35 ug / g, with an average of 2 , 64 µg/g (Esbri et al., 2012). According to other studies, where artisanal mining works by extracting gold with mercury in Venezuela, extremely higher values are observed, with an average of 6.1 ug / g, (Alvarez and Rojas, 2006).   Three 3 types of plant where analyzed and their corresponding sediments. It is worth mentioning that the number of plants analyzed is much less than ideal, since the study area is desert, and it is very difficult to find a variety of them. In general, the concentration of Hg in plants values were low (V2planta = 0.427 mg/g V3planta = 0.952) and a high value of 7.17 in the V1 mg/g, plant located near the processing area and use of mercury. Mercury concentrations in sediments are varied (V1sed = 62.5 mg/g, V2sed = 0.427 mg/g V3sed = 0.186 mg/g).  According to this study, children have a high content of total mercury in hair, with average values of 1,983 µg/g. The nearest areas where processes are performed amalgamation, there are higher concentrations of mercury in water.   Alternative methods are being studied gold recovering without the use of mercury, such as bioleaching.  Fig. 1. Location of Ocoña river Basin. Table 1. Hg content of water samples from the Ocoña subbasin. Methodology Fig.4. Mercury amalgam. Sample Concentration Hg (mg/Kg) Age Sex Ocupation Amalmagam Consumption fish C-1 - 25 male Quimbalete no 1 time/month C-2 3,66 24 male Quimbalete no no C-3 4,24 50 male Quimbalete no 1 time/day C-4 2,08 17 male Quimbaleter no 1 time/month C-5 2,31 19 male Quimbalete no 1 time/month C-6 1,85 33 female Hg seller no 1 time/week C-7 4,78 27 male Quimbalete Yes 3 timonth/month C-8 1,97 37 female Seller/Quimb No 2 timonth/week C-9 0,62 44 female cooker No 3 timonth/month C-10 2,88 38 female Yes 3 timonth/month C-11 1,47 4 male student No 4 timonth/month C-12 6,43 28 female Quimbalete No 4 timonth/month C-13 1,35 24 female Seller/Quimb yes no C-14 4,14 63 male Quimbalete no 4 timonth/month C-15 0,71 0,6 male no no C-16 1,8 4 female student no 4 timonth/month C-17 1,04 39 male cooker no 4 timonth/month C-18 2,12 6 male student no 4 timonth/month C-19 2,54 10 male student no 4 timonth/month C-20 6,75 40 female Quimbalete no no Table 2. Concentration of Hg in hair in people from Misky. References Alvarez, L., Rojas, L. (2006). Presencia de mercurio total en habitantes de los asentamientos indigenas El Casabe, municipio autónomo Raul Leoni y el Plomo, municipio autónomo Manuel Carlos Piar – Estado Bolivar (Venezuela). Saber, Universidad de Oriente, Venezuela.Vol. 18. Nº 2: 161-167.   Esbri, J.M., Higueras, P., Martinez, A., Diez, S., Tobias, A. (2012). Estudio comparativo de exposición de los habitantes de Almadén y Castilla La Mancha medaynte el uso de los contenidos de mercurio en cabello. II Jornadas de investigación: Ciudad Real- Comunicación 236.  Conclussions The nearest areas where processes are performed amalgamation, there are higher concentrations of mercury in water. The plants and soil also processes closest to contain mercury higher values.  According to the means by occupation, students (children 3 to 16 years), have a high content of total mercury in hair, with average values ​​of 1,983 ug / g. The nearest areas where processes are performed amalgamation, there are higher concentrations of mercury in water.  It provides a continuation in environmental studies, in order to obtain results on the effects that the use of mercury or other chemicals for the production of metal. They study the possible remediation and seek other methods for obtaining gold, less corrosive and harmful to people and the environment. Fig. 2. Quartz vein with sulfides Fig. 3. Processing with quimbaletes For the environmental assessment of the area contaminated by mercury, we proceeded to the taking of samples of different types: water, rocks, plants and hair.  It has produced a map with the different areas sampled as representative as possible and appropriate access for making results. Obtained a total of 12 samples of water, 3 plants, soil 3 and 20 samples of hair.  In the analysis method used to plant, soil, and hair was atomic absorption spectrometry for determination of total mercury.  Statistical analysis using the Minitab program, which analyzed the standard statistical variables. Further correlation test is performed between different variables. 

Mercury pollution caused by artisanal gold mining the Ocoña river Valley, Peru

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Mercury pollution caused by artisanal gold mining the Ocoña river Valley, Peru

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