Mercury in the Madeira River ecosystem ... - ScienceDirect.com

5 downloads 0 Views 356KB Size Report
The Madeira is a highly productive river and is the main fishery to a great proportion of the local population. ... of Hinton et al. (1987), with some adjustments.
Forest Ecology and Management, 38 ( 1991 ) 239-245 Elsevier Science Publishers B.V., Amsterdam

239

Mercury in the Madeira River ecosystem, Rondbnia, Brazil W.C. Pfeiffer~, O. Maim a, C.M.M. Souza a, L. Drude de Lacerda b, E.G. Silveirac and W.R. Bastos a aLaborat6rio de Radiois6topos, Instituto de Biofisica Carlos Chagas Filho, UFRJ, Rio de Janeiro, 21941 RJ, Brazil bDepartamento de Geoquimica, UFF, Niter6i, 24210 R J, Brazil CDepartamento de Geografia e Hist6ria, UNIR, Port Velho, 78900 Rond6nia, Brazil

ABSTRACT Pfeiffer, W.C., Maim, O., Souza, C.M.M., Drude de Lacerda, L., Silveira, E.G. and Bastos, W.R., 1991. Mercury in the Madeira River ecosystem, Rond6nia, Brazil. For. Ecol. Manage., 38: 239245. A survey of mercury levels in river water and sediments, forest soils, fish, air and human hair is presented for the Madeira River watershed in southwest Amazonia, Brazil. Mercury levels appeared particularly high in tributary rivers close to major gold-miningareas. High Hg levels in fish (up to 2.7 ppm) were also found in such areas. Atmospheric Hg levels were mostly close to background, but can reach high values (3.2 mg/m 3) in the proximity of the Hg-Au reburning complex. Human-hair levels, however, reach values up to 26.7 ppm, indicating high exposure rates of the local population.

INTRODUCTION

The Madeira River basin is located in the southwestern Amazonian region, draining an enormous watershed mostly covered by tropical rain-forest ecosystems, although in recent years accelerated deforestation has occurred in localized areas under the 'P01o Noroeste Project' (Fearnside, 1986). Total river water flow varies between 20 000 and 48 000 m3/s during the dry and rainy season, respectively. During the rainy season, water covers the main river channel and overfloads the adjacent forest, forming innumerable marginal lakes. Extraction of alluvial gold in the Madeira River basin has become a significant activity during the last decade. Most of the gold-mining occurs in the Madeira River itself, along 300 km from Porto Velho, capital of the State of Rondonia, along the Bolivian border as far as the town Guajar~i-Mirim (Fig. 1). 0378-1127/91/$03.50

© 1991 - - Elsevier Science Publishers B.V.

240

W.C. PFEIFFER ET AL 8~o00'

/

84o00 `

f*

r .j

0

Study

Areo RivWl

wo~rWOyl

ROODS . . . . SCALE : 1 : 0 0 0 . 0 0 0 o

lo

20

]10

i**1., (~)

0

~/¢.oo Fig. 1. The Madeira River basin, Rondonia, Brazil.

Notionol Iim*ll i nter rlotlor~l hrrmts Stote CODITOl C*ti*s

MERCURY IN THE MADEIRA RIVER ECOSYSTEM, RONDONIA

241

The mining process, executed with boats and divers, as well as with mechanical dredges, remove bottom sediments from the river bed. Heavy particles are concentrated gravimetricaly and then amalgamated with mercury, forming a Hg-Au complex; this is burnt, and Hg vapour is lost to the atmosphere. During the whole process, a significant amount of Hg is also lost directly into rivers (Lacerda et al., 1988; Pfeiffer and Lacerda, 1988). Rondonia Environmental Department estimated that from 1979 to 1985 approximately 100 tons of Hg were released into the river (Anonymous, 1986). The major threat of Hg contamination in the area, apart from direct aspiration of Hg vapour, is the possibility of Hg undergoing organification to alkyl-Hg compotinds, in particular mono-methyl mercury which concentrates in muscle tissues of high-trophic-level fishes (Anonymous, 1985, 1986; Salomons and Frrstner, 1984 ). The Madeira River, a white-water-type river (Junk and Furch, 1980) does not present physico-chemical conditions favouring mono-methyl-Hg formation. Rivers inside the forest, however, are black- and clear-water type rivers (Junk and Furch, 1980). Under such conditions of acidic water, low conductivity, and high dissolved organic matter, inorganic Hg can undergo very fast transformation into monomethylation, and then be carried back into the main rivers (Lindqvist and Rhode, 1985; Lacerda et al., 1988; Mitra, 1986). The Madeira is a highly productive river and is the main fishery to a great proportion of the local population. Under this situation, the potential risk of Hg contamination to the environment and local population is very large. As the biogeochemistry of Hg in tropical ecosystems is almost unknown, the study of the fate of Hg in this region should produce important information about the environmental Hg cycle. The present paper presents Hg concentrations in water, sediment, fish, soil, air and human hair to assess the magnitude of Hg contamination in the area, and to evaluate as well as the potential risk of a Hg transference to the local inababitants. MATERIALS AND METHODS

Four surveys were carried out in the region, from October 1986 to June 1988. Water and bottom sediments were collected along the main river in sedimentation areas, in major tributaries and in forest rivers. The soil samples were from the forest adjacent to the water- and sediment-sampling points. Water samples were kept in plastic flasks and stabilized by the addition of 0.01% K2Cr207 and 5% HNO3. Sediments were kept in plastic boxes and frozen until analysis. Fish samples of known origin and species were obtained from local markets and/or directly from local fishermen; the edible parts were

242

W.C. PFEIFFERET AL.

separated and frozen until analysis. Most fish were carnivorous. Human hair samples were collected among local inhabitants and gold-miners, identified and kept in plastic bags until analysis. Soils and sediments samples were sieved in the laboratory and the fraction smaller than 74 pm was analysed (Lucas et al., 1986 ). Samples were treated according to the technique described by Iskandar et al. (1972), with minor adjustments. The water analytical procedure was performed according to the technique of Hinton et al. (1987), with some adjustments. In 20 ml of water, 2 ml of a strong acid mixture ( 14M HNO3: 18M H2SO4, 1 : 1 ) were added and before cooling 2 ml of 5% KMnO4 were introduced. Fish (edible parts) and hair samples were treated according to the technique described by Agemian and Cheauer (1978 ) with small adjustments. Hair samples prior to analysis were washed with 0.01% EDTA solution in order to remove dust particles, fat substances and external contamination. Air samples were collected by aspirating air through appropriate glass bubblers filled with 0.5% KMnO4 and 5% H 2 S O 4 at a rate of 2 1/min according to the technique described by Kudsk ( 1964 ). Prior to analysis, all samples were neutralized with H4C1ON-NaC1 hydroxylamine. Mercury concentrations in all samples were determined by atomic absorption spectrophotometry using a Varian AA-1475 equipment provided with a cold-vapor generator Varian VGA-76. Analysis were performed in triplicate, and detection limit was determined as 0.04 ppb (Slavin et al., 1972 ). Accuracy was controlled using internal standard procedures and participating in intercalibration programs. RESULTS AND DISCUSSION

Concentration intervals determined for water, bottom sediments and soils collected along the Madeira River and forest rivers are presented in Table 1. In general, all values for sediments and soils are in the same order of magnitude of natural levels (0.01 ppm in 70% of samples). The remaining 30% samples presented higher values, which can reach 19.83 ppm in the Mutum TABLEI Hg concentrations in water, sediments, and soils from the Madeira River and adjacent waterways Sample

Madeira River

Forest rivers

Control areas (mean)

Water (/~g/1) Bottom sediments (/1g/g) Soils (/zg/g)

0.2-5.1 0.05-2.62 0.03-0.18

0.4-9.5 0.2-19.83 0.1-0.95

n.d. 0.19 0.1

n.d.=0.04.

243

MERCURY IN THE MADEIRA RIVER ECOSYSTEM, RONDONIA

Paranfi tributary which therefore, can be characterized as the most contaminated site. Adjacent soils can reach 0.95 ppm. These soil values reinforce the model proposed by Pfeiffer and Lacerda ( 1988 ), which estimated that major Hg lost throughout the process (55-60%) enters the atmosphere and is then deposited on the adjacent forest. A general analysis of individual results indicate that the metal is not distributed along the river but is concentrated in some 'hot-spots', mainly Mutum Paran~i (point 4, Fig. 1 - 19.83 #g/g) Prainha (point 5 - 2.82/~g/g) and Teot6nio (point 8 - 0 . l/tg/g). Mercury concentrations in edible parts of fishes are presented in Table 2. Results indicate that fishes captured in the tributary rivers present the highest Hg concentrations, surpassing the maximum permissible concentration for human consumption allowed by Brazilian legislation (Anonymous, 1975). Carnivorous fishes from the Madeira River also can present high Hg contents thus representing a potential risk to human consumption. Mercury concentrations in air samples are presented in Table 3. Although the values observed near the reburning installations, operated by gold dealers in the middle of the city of Porto Velho, reached 3.2/zg/m 3 at the emission point, the majority of values determined are of the same order of magnitude of published data for natural areas (Matheson, 1979). This result may indiTABLE 2 Mercury concentrations in fishes, edible parts (/~g/g, wet weight) Origin

Popular n a m e / S c i e n t i f i c n a m e

Hg concentration

Madeira River ( Porto Velho )

Filhote a (Brachyplatystoma sp. ) Corimata b

0.5

( Prochilodus nigricans )

0.21 1.43

D o u r a d o (Salminus sp. ) Madeira River ( 180 km downstream from goldmining area)

Fiihote ~ (Brachyplatystoma sp. ) Corimata b

1.47

( Prochilodus nigricans )

O. I 0

Jaci Paran~i (Tributary)

Tucunar6 a (Cichla sp. ) Pintado ~

0.47

( Pseudoplatystoma flasciatus )

2.70

J a m a r i River (Control area)

Pintado a (Pseudoplatystoma flasciatus) Pirarucu a ( Arapaima gigas ) J a t u a r a m a b (Brycon sp. )

0.07

O. 17 0.08

t M a x i m u m Permissible Concentration for h u m a n consumption, 0.5 ppm. a carnivorous; b detritivorous.

244

w.c. PFEIFFERETAL.

TABLE 3 Mercury concentration in air (#g/m 3) Place

Mean concentration

Porto Velho (Gold reburning area) Porto Velho (Near the University) Humait~i ( 180 km downstream from goldminingarea) Guajani-Mirim Teotonio water fall Rio de Janeiro Non mineralized regions

3.2 0.1 0.02 0.08 0.5 0.02 0.022-0.0050

TABLE 4 Mercury concentration intervals for human hair samples (/tg/g dry weight) Sample origin

Concentrationt

Madeira River Mato Grosso Amazonas2. Rio de Janeiro Vegetarian habits Common fish diet No regular fish diet

1.0-26.7 0.04-6.3 10.0-29.0 0.74 3.0-6.4 1.2-2.7

~Acute intoxication concentrations stablished by WHO = 50/~g/g. 2*Munduruku indians working at the Tapaj6s gold mining area (common fish diet).

cate that Hg residence time in the local atmosphere is very short, as expected due to the high humidity of the Amazon region (Lacerda et al., 1988 ). Results of Hg concentrations in human-hair samples from different origins are presented in Table 4. Low concentration results must be analysed carefully, since they depend strongly upon dietary habits. On the other hand, the outstanding values determined for the Indians of the Amazonas region and gold miners from the Madeira are high, indicating the possibility of these people being exposed to toxic levels. Based on the data generated from the gold-mining area, Hg contamination is clearly detected in some sites along the Madeira River, where Hg concentration levels can reach values as high as 19.83/~g/g in bottom sediments and up to 2.7/~g/g in fish (Table 2, pintado in the Jacy Paran~i). Therefore these areas can be considered potentially critical, as the population around is exposed to a Hg body-burden contamination mainly through the food chain. Apart from this concern, mining activity developed in the Madeira River basin is leading to deforestation and endemic malaria infection as well as associated an enormous social impact produced by the miners' presence, increasing every year.

MERCURY IN THE MADEIRA RIVER ECOSYSTEM, RONDONIA

245

ACKNOWLEDGEMENTS T h e a u t h o r s wish to t h a n k the F e d e r a l U n i v e r s i t y o f R o n d o n i a ( U N I R ) for local s u p p o r t . T h i s r e s e a r c h was s u p p o r t e d b y C N P q , F I N E P , F A P E R J , SUDECO, CNEN, UFRJ and UNIR. T h e p r e s e n t p a p e r is C o n t r i b u t i o n no. 5 o f the p r o j e c t ' M e r c u r y Biogeoc h e m i s t r y in T r o p i c a l E c o s y s t e m s ' , c o n d u c t e d b y U F R J , U F F a n d U N I R . REFERENCES Agemian, H. and Cheauer, V., 1978. Simultaneous extraction of mercury and arsenic from fish tissues and an automated determination as arsenic by Atomic Absorption Spectrometry. Anal. Chim. Acta, 101: 193-197. Anonymous, 1975. Ministrrio de Satide ResolufAo no. 18/75 da Comissao Nacional de Normas e Padr~ses para alimentos, Brasil. Di~irio Official da Uni~o, 9 de dezembro de 1975. Anonymous, 1976. Environmental Health Criteria. I. Mercury. World Health Organization, Geneva, pp. 1-131. Anonymous, 1985. I. International SCOPE metals cycling workshop. Rapporteur's Report on Mercury. Scientific Committee on Problems of The Environment, Toronto, 16 pp. Anonymous, 1986. Manual do Garimpeiro. Orientag~o para uso do azougue Conselho Estadual Meio Ambiente, Porto Velho, RO, 15 pp. Fearnside, P.M., 1986. Settlement in Rondrnia and the taken role of science and technology in Brazil's Amazonian development planning. Interci~ncia, 11: 229-236. Hinton, E.R., Rowlins, L.K. and Flanagan, E.B., 1987. Development of on-line mercury stream monitor. Environ. Sci. Technol., 21: 198-202. Iskandar, I.K., Syers, J.K., Jacobs, L.W., Keemey, D.R. and Gilmour, J.T., 1972. Determination of total mercury in sediments and soils. Analyst, 97: 388-393. Junk, W.J. and Furch, K., 1980. Quimica da ~igua e macrofitas aqufiticas de rios e iguaraprs na Bacia Amazrnica e nas ~uas adjacentes. I. Trecho Cuiaba - Porto Velho - Manaus. Acta Amazrn., 10:611-633. Kudsk, F.N., 1964. Chemical determination of Hg in air (An improved Dithizone method for determination of mercury and mercury compounds). Scand. J. Clin. Lab. Invest. 16 (Suppl. 77): 1-15. Lacerda, L.D. Pfeiffer, W.C., Ott, A.T. and Silveira, E.G., 1988. Mercury contamination in the Madeira River, Amazon - Hg inputs to the environment. Biotropica, 21: 91-93. Lindqvist, O. and Rhode, H., 1985. Atmospheric mercury, a review. Tellus, 37B: 136-159. Lucas, M.F., Caldeira, M.F., Hall, A., Duarte, A.C. and Lima, C., 1986. Distribution of mercury in the sediments and fishes of the lagoon of Aveiro, Portugal. Water Sci. Technol., 18:141148.

Matheson, D.H., 1979. M~ercuryin the atmosphere and in precipitation. In: J.O. Nriagu (Editor), The Biogeochemistry of Mercury in the Environment. Elsevier, Amsterdam, pp. 113129. Mitra, S., 1986. Mercury in the Ecosystem. Trans Tech Publications, Columbus, OH, 327 pp. Pfeiffer, W.C. and Lacerda, L.D., 1988. Mercury inputs into the Amazon Region, Brazil. Environ. Technol. Lett., 9: 325-330. Salomons, W. and Frrstner, V., 1984. Metals in the hydrocycle. Springer, Berlin, 249 pp. Slavin, S., Barnett, W. and Crassweller, P.O., 1972. The determination of atomic absorption detection limits by direct measurements. Atomic Absorpt. Newsi., 11: 37.