Environmental Pollution 123 (2003) 301–305 www.elsevier.com/locate/envpol
The effect of iron-ore particles on the metal content of the brown alga Padina gymnospora (Espı´rito Santo Bay, Brazil) Cristina A.G. Nassara, Leonardo T. Salgadob, Yocie Yoneshigue-Valentina, Gilberto M. Amado Filhoc,* a
Universidade Federal do Rio de Janeiro, Centro de Cieˆncias da Sau´de, Instituto de Biologia—Bloco A (sala 099), Ilha do Funda˜o, CEP 21944-970, Rio de Janeiro, RJ, Brazil b Universidade Federal do Rio de Janeiro, Centro de Cieˆncias da Sau´de, Instituto de Cieˆncias Biome´dicas—Departamento de Anatomia—Bloco F (sala 007), Ilha do Funda˜o, 21944-970, Rio de Janeiro, RJ, Brazil c Instituto de Pesquisa Jardim Botaˆnico do Rio de Janeiro, Rua Pacheco Lea˜o, 915, 22460-030 Rio de Janeiro, RJ, Brazil Received 5 October 2001; accepted 6 September 2002
‘‘Capsule’’: Iron ore deposits mat be the source of metals found in the brown alga Padina gymnospora. Abstract The iron-ore particles discharged by a pellet processing plant (Espı´rito Santo Bay, Brazil) cover the seabed of Camburi Beach and consequently, the epibenthic community. In order to determine the importance of the contribution of the iron-ore deposits to the metal concentration in macroalgae of Espirito Santo Bay, four methods of cleaning particulate material adhered to the surface of thalli were tested prior to metal tissue analysis (Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) of Padina gymnospora. In addition, heavy metal concentrations were determined in individuals of P. gymnospora from a site (Frade Island) not affected by the iron-ore particles. The most efficient cleaning treatment, a combination of scraping and washing with an ethanol–seawater solution (NA+SC +ET) removed a number of particles on the surface of thalli 10 times higher than that observed in the control (C). Using this treatment, the total-metal concentrations were reduced by 78% for Fe and 50% for Al respect to the control. However, Fe, Al and Cu concentrations after treatment NA+SC+ET were significantly higher than those found at Frade Island. It is suggested that the iron-ore deposit might be a source for metal availability to macroalgae exposed to the dumped material at Espirito Santo Bay. # 2003 Elsevier Science Ltd. All rights reserved. Keywords: Pollution; Iron-ore; Heavy metals; Macroalgae; Espı´rito Santo State; Brazil
1. Introduction In Espı´rito Santo Bay, the area of Camburi Beach area was subjected to the dumping of waste from an iron-ore pellet processing plant for more than 20 years (Teubner et al., 1991). During this period, tons of ironore material were deposited on Camburi beach and the adjacent seabed, covering most of the local epibenthic community (Mitchell et al., 1990). Particles derived from the iron-ore waste are mostly composed of Fe2O3 (hematite) but compounds like Al2O3, SiO2, CaO, FeO and trace metals are usually associated with iron-ore (Das et al., 2000; Natarajan and Namita, 2001). Although this particulate material is relatively insoluble in seawater, it can become available to the biota if the * Corresponding author. Fax: +55-21-21-22947526. E-mail address: gfi
[email protected] (G.M. Amado Filho).
pH is low and there is a significant amount of organic matter, such as fulvic acid, in the water receiving dumped material (Kratochvil and Volesky, 1998). Under this condition, Fe3+ can be reduced to Fe2+ which is several orders of magnitude more soluble in seawater (Matsunaga et al., 1994). Seaweed species have been commonly used as indicators of biologically available trace metals due to the high capability of their fronds for accumulating metals dissolved in the seawater (Riget et al., 1995; Amado Filho et al., 1997; Muse et al., 1999). Among tropical seaweeds, the brown algae Padina spp. have been shown to be able to withstand a long-term uptake of trace metals (Karez et al., 1994; Amado Filho et al., 1999; Engdahl et al., 1998; Sa´nchez-Rodrı´guez et al., 2001). The species Padina gymnospora (Kuetzing) Sonder (Dictyotales, Phaeophyta) was chosen for this work due to its ubiquous occurrence and abundance at the upper
0269-7491/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0269-7491(02)00369-X
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sublittoral zone of the Espı´rito Santo coast (Mitchell et al., 1990). In order to determine the contribution of surface adhered iron-ore particles to the metal tissue concentration of Padina gymnospora from Camburi Beach, heavy metals were quantified in individuals submitted to four different cleaning treatments. Heavy metal concentrations were also determined in individuals from a site (Frade Island) not affected by the iron-ore waste for comparison of the results obtained.
2. Materials and methods Individuals of P. gymnospora were collected in December of 1998 from the shallow subllitoral zone (0.5
m) of Camburi Beach (iron-ore contaminated site ) and Frade Island (site located in an area under non iron-ore influence; Fig. 1). All plants were collected by hand, frozen for storage ( 4 C), and transported to the laboratory, where plants were thawed in filtrated local seawater, cleaned of epiphytes and thereafter the holdfasts were removed. Four cleaning treatments were used for removing the particles adhered to the fronds of the Camburi’s plants (methodology adapted from Gledhill et al., 1998): C (control plants), NA (removal of the rolled apical margin), NA+SC (removal of the rolled apical margin and scraping of the frond with a glass slide) and NA+SC +ET (removal of the rolled apical margin, scraping of the frond in a 1:9 ethanol: seawater solution, pH 8.2). After cleaning, all samples were rinsed in distilled water. Heavy metals analysis followed the method
Fig. 1. Map showing the location of the sampling sites at Espı´rito Santo Bay.
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described by Amado Filho et al. (1999). Fronds were dried at 60 C until constant weight, then homogenized and turned into ash at 420 C in a muffle furnace. Fractions of 0.5 g (dry wt.) were digested in 10 ml concentrated HNO3 (65% wt.) on a hot plate and left to evaporate. The resulting residue was re-dissolved in 0.1 N HCl. Metal concentrations were measured in triplicate by flame atomic absorption spectrophotometry (Varian AA-1475). Results are given in mg g 1 of dry weight. Analytical procedures were tested by comparative analysis of International Atomic Energy Agency (IAEA) certified reference material IAEA-140 (sea plant homogenate, Fucus), and the results obtained were within confidence limits (significance level =0.05; Table 1). Three plants from each treatment were analyzed under a light microscope (magnification of 100 ). Images of each frond (n=6) were taken with a digital camera (Sony CCD-Iris), and the number of the particles observed per field were estimated using the SigmaScan1Pro 5.0 software. Scanning electron microscopy images of the iron-ore particle adhered to the P. gymnospora surface thallus were obtained after sample drying by CO2 critical point (Balzer/Union CPD 020) method. Samples were mounted on appropriate stub, and thereafter gold-sputtered and were observed and photographed with a Jeol 5310 SEM, operating at 20 kV. The difference between the treatments and the sampling sites was tested using ANOVA (one way analysis). Table 1 Comparison of analyzed metals concentration of algal reference material (IAEA—140, sea plant homogenate, Fucus): 1, mean reference concentration value; 2, results of concentration obtained in this work Metal concentration (mg g
1 2
1
dry wt.)
Al
Cd
Cr
Cu
Fe
Mn
Ni
Pb
Zn
1184 1340
0.54 0.50
10.4 9.70
5.05 4.98
1256 1280
56.1 57.9
3.79 4.04
2.19 1.98
47.8 49.9
Table 2 Comparison of the heavy metal concentration (mg g Samples
Fe Al Zn Mn Ni Cu Pb Cr Cd
1
303
Correlation between the number of particles and the metal concentration for each treatment was estimated using the r-pearson index. All statistical analyses were performed using the Statistica 19971 software package.
3. Results and discussion The most efficient iron-ore particle removal treatment was the combination of scraping and washing with ethanol solution (NA+SC+ET). Comparing treatment C and treatment NA+SC+ET there was a significant reduction (P < 0.05) in mean metal concentrations for Fe (78%), Al (50%), Mn (26%) and Cr (22%). Gledhill et al. (1998) obtained a reduction of 66% of Fe concentration in Fucus vesiculosus using the same treatment. Of the three cleaning treatments, only the NA treatment did not result in a significant reduction (P > 0.05) in metal concentrations when compared to the control treatment C (Table 2). It indicates that the rolled apical margin did not retain a significant amount of particles or accumulated less metal than the rest of the plant. Even after the treatment NA+SC+ET, Fe, Al and Cu concentrations found in Padina were significantly higher than those found at Frade Island (P < 0.005). Values of Fe obtained in the iron-ore deposit area (Camburi Beach) compared to the non-affected area (Frade Island) were in agreement with results reported by Wong et al. (1979). For other metals (Cd, Cr, Mn, Ni, Pb and Zn) no significant difference was observed between the sites (P > 0.05). According to Wong et al. (1979), in sites where iron-ore tailings have been exposed to rain and seawater for long periods of time, macroalgae accumulate high concentrations of Fe, Pb and Mn. The number of particles (mean standard deviation) found on the surface of fronds of control plants under treatment C (166 94) was about 10 times higher than that observed after treatment NA+SC+ET (14 5). No significant difference was found between the number
dry wt.) for Padina gymnospora (meanSD, n=3)
Camburi treatments
Frade Island
C
NA
NA+SC
NA+SC+ET
21,9007100 73101400 4910 450.5 3.620.52 2.711.22 4.070.31 6.580.59 0.220.03
30,6002130 13,9001250 582 690.3 5.250.34 3.490.07 5.910.37 10.000.26 0.220.05
93502160 42601020 612 340.4 3.510.39 2.540.32 5.040.89 5.360.75 0.230.06
44301030 2850440 662 280.3 4.450.30 2.430.44 4.000.07 4.160.23 0.290.10
367 66 617 46 132 66 45 23 5.23 0.61 0.33 0.08 4.53 0.51 4.53 0.45 0.33 0.08
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of iron-ore particles in plants from treatments NA (211 150), NA+SC (95 87) and C. Among the treatments, a significant positive correlation (P< 0.05) was observed between the reduction of the mean particle number and the decrease of Fe (r=0.97), Al (r=0.96) and
Cr (r=0.91) concentrations in algal tissues. This observation indicates that surface particles and cleaning technique strongly influence the analyses of the metal concentration in tissues, reinforcing the need for an effective cleaning procedures previous to metal concentration analysis.
Fig. 2. (A) General view of an iron-ore particle on Padina gymnospora by scanning electron microscopy. (B) Interaction between the iron-ore particle and the CaCO3 crystals (calcite) on P. gymnospora frond (scanning electron microscopy). Bar=1 mm.
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Observation under scanning electron microscope (Fig. 2) revealed that iron-ore particles were partially covered by calcite crystals on the thallus surface of P. gymnospora indicating that the external biomineralization process of calcium carbonate in species of the genus Padina, in agreement with results reported by Okazaki et al. (1996), can contribute to iron-ore particle retention. In summary, we have shown that deposits of iron-ore particles on the fronds of P. gymnospora can be efficiently removed by scraping thalli surface in the presence of an ethanol and seawater solution and the algal metal concentrations of Fe and Al were mainly reduced to 78 and 50%, respectively. Despite reduction of metal content in P. gymnospora the concentrations of Fe, Al and Cu remaining after this treatment were still higher in the area close to the iron-ore deposit than the values found in the non-affected area, suggesting that the dumped material may be a source of available metals to macroalgae living at Camburi Beach.
Acknowledgements The authors would like to thank Dr. Wolfgang C. Pfeiffer from the Laborato´rio de Radioiso´topos/IBCCF from Universidade Federal do Rio de Janeiro for the metals analyses, to Renato Rodrigues from CEPEMAR for his help during the fieldwork and, to Lynne Macrae for her help with the English version of the manuscript. We also wish to thanks the anonymous reviewers that provided valuable comments that improved the manuscript. Part of this work was financially supported by the Brazilian program PRONEX/MCT and by research grants of CNPq (521688/96-5) and FAPERJ (E-26/ 170.336/98) to G.M. Amado Filho. References Amado Filho, G.M., Andrade, L.R., Karez, C.S., Farina, M., Pfeiffer, W.C., 1999. Brown algae species as biomonitors of Zn and Cd at Sepetiba Bay, Rio de Janeiro, Brazil. Marine Environmental Research 48, 213–224. Amado Filho, G.M., Andrade, L.R., Reis, R.P., Bastos, W., Pfeiffer,
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