Distribution of metals in the sediment of the Itá Reservoir, Brazil

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1 Distribution of metls in the sediment of the Itá Reservoir, Brzil Distribuição de metis no sedimento do Reservtório de Itá, Brsil Boni, NC., Souz-Frnco, GM., Fogolri, O, Mocelin, DJC. nd Dl Mgro, J. 1 Progrm de Pós-Grdução em Ciêncis Ambientis, Universidde Comunitári Regionl de Chpecó UNOCHAPECÓ, Av. Sendor Attílio Fontn, 591-E, Efpi, CP 1141, CEP , Chpecó, SC, Brzil e-mil: ndib@unoescxxe.edu.br; gfrnco@unochpeco.edu.br; fogolri@gmil.com; douglsmocellin@gmil.com; jcir@unochpeco.edu.br Chemicl Limnology Abstrct: Aim: Nowdys, one of the mjor concerns of the ecology studies relting to qutic ecosystems refers to the impct cused by the relesing of hevy metls in severl nturl environments, minly in the ones tht hve greter interction with nthropic ctivities. In reltion of reservoirs, sediments re considered to be comprtments of ccumultion of pollutnts, brought by the wter column, tht hve their origin in the different uses of soil of the dringe res bsin. The objective of this reserch ws to evlute the concentrtion of hevy metls in severl sites distributed long the Itá Reservoir in Snt Ctrin stte, Brzil. Methods: Smples were collected in five sites: in the reservoir (deep zone) nd in two tributries (Frgosos nd Rncho Grnde rivers) between November/04 nd August/05 (three smpling occsions). Results: High concentrtions of Fe were found in ll the sites; the concentrtion of Zn nd Cu ws higher in Frgosos River compred to the other sites. Conclusions: High levels of orgnic mtter nd the concentrtion of hevy metls re both relted to the use nd occuption of soil, specificlly due to intensive griculture/cttle ctivities nd urbniztion. Keywords: reservoirs, trce-elements, contmintors, sediments. Resumo: Objetivo: Atulmente um ds grndes preocupções n áre d ecologi de ecossistems quáticos refere-se o impcto cusdo pel liberção de metis pesdos nos diversos mbientes nturis, principlmente, nqueles de mior interção com tividdes ntrópics. No que se refere os reservtórios, os sedimentos são considerdos como um comprtimento de cumulção de poluentes, prtir d colun d águ origindos dos diferentes usos do solo d bci de drengem. Este estudo teve por objetivo vlir concentrção de metis pesdos no sedimento do reservtório d usin Hidrelétric de Itá. Métodos: As colets do sedimento form feits em 5 pontos mostris, no corpo do reservtório (zon profund) e em dois tributários (Rio Frgosos e Rio Rncho Grnde) entre os meses de novembro/04 e gosto/05 (3 cmpnhs). Resultdos: Alts concentrções de Fe form registrdos em todos os pontos; no rio Frgosos concentrção de Zn e Cu foi significtivmente superior os demis locis. Conclusões: Os elevdos teores de mtéri orgânic bem como s concentrções de metis pesdos estão relciondos com o uso e ocupção do solo, como intens tividde gropecuári e urbnizção. Plvrs-chve: reservtórios, elementos-trço, contminntes, sedimento. 1. Introduction The construction of dms constitutes one of the oldest nturl humn interventions nd it hs been very importnt ctivity in Brzil throughout the lst decdes, due to its severl uses. From the biologicl point of view, the reservoirs constitute n interctive nd complex net between the orgnisms nd their physicl nd chemicl environments, which is the result of the permnent processes of deling with the functions of climtic forces nd with the effects produced by the system s mnipultion (Tundisi, 1999). Thornton (1990) emphsizes tht sedimenttion constitute the min wy through where the llochthonous mteril tht lnds in the reservoir is removed, exerting influence in the distribution of prticles nd in the zoning of the reservoirs. According to Almeid nd Weber (1999), sediments re not just stocks of substnces generted in the wter column or brought by rivers, winds nd rin, but they lso function s comprtment tht reprocesses these mterils, nd in the long term they cn supply toxic substnces in the biot nd consequently risk the lives long the trophic chin. Considering the dynmics of qutic ecosystems nd the ccumultive chrcteristic of the reservoirs, it is expected tht most trce-elements which enter into the system re deposited onto the sediment. Thus, throughout the yers, sediments tend to be potentilly more nd more toxic in the environment, cusing dverse effects to the biot (Espíndol et l., 1998; Tonissi, 1999). The toxicity of the trce-elements comes minly from their cpcity of interfering in the enzymtic processes nd from their smll mobility in the orgnism, due to their smll sizes nd to the chrges they possess. Thus, sediments consti- Act Limnol. Brs., 2009, vol. 21, no. 2, p

2 246 Boni, NC. et l. tute n importnt chemicl indictor of the contmintion of the qutic ecosystems, due both to their cpcity of ccumulting trce-elements nd to the role in the trnsport nd, s possible source of contmintion. According to Lmberson et l. (1992), the toxicity of hevy metls in the sediment cn be ffected by the connections between the ions of the metls nd the constituents of the sediment. Thus, the vilbility of the contmintors in the sediment is ssocited to prting behvior with the orgnic mtter, in ddition to the dsorbing processes tht occur between hevy metls nd fine prticles size. Metls tht hve wek ssocition, commonly linked to the sediments, cn be esily broken by the biot, becoming bio-vilble (Försten nd Wittmnn, 1981; Wetzel, 1983; Gtti, 1997). The orgnic mtter is closely linked to the elements Cu, Zn nd Fe, in the lkes sediments, nd to the Cu in the rivers. The orgnic mtter hs good cpcity of bsorption of hevy metls; this ffinity cn both concentrte metls in the environment, hving n impct on it, or it cn be used in the removing of metls in ffected environments. An importnt physicl property of the orgnic mtter is ssocited with the fine texture of the sediments, generlly contining nturl percentge of humic mteril derived from the biologicl trnsformtions of plnts nd niml wste. The humic mteril cn be there s discrete prticle or s lyer of cly prticles, becuse the humic mteril increses the ffinity between the sediment nd the metls (Förstner nd Wittmnn, 1981; Wetzel, 1983; EPA, 1991). Hevy metls re prt of the environment nd the living mtter, occurring nturlly in smll concentrtions, rnging from prts per billion to prts per million. Among them, elements such s Zn, Fe, Mn, Cu, Co nd Mo re essentil to orgnisms, even in minimum quntities, becuse they tke prt in the physiologic processes; other trce elements, such s the Hg, Pb nd Cd, don t hve ny known biologicl function, nd they re responsible for dverse effects on the biotic community. Even the ones which hold biologicl function, in high concentrtions, cn cuse toxicity to orgnisms (Esteves, 1998). The min purpose of this reserch ws to chrcterize the chemicl composition of the sediment, nd to evlute the concentrtion of the hevy metls Cr, Cu, Pb, Zn, Mn, Fe nd Cd s n indictor of contmintion, in the Itá Reservoir (south of Brzil). 2. Mteril nd Methods 2.1. Study re The Itá reservoir forms lke tht hs surfce of 141 km 2 ; it is locted in the Urugui River, between the sttes of Snt Ctrin nd Rio Grnde do Sul. Its closing occurred in 2000, holding 1450 MW cpcity. The two min rivers tht flow down towrds the reservoir re Peixe River in Snt Ctrin nd Apuê River in Rio Grnde do Sul. The region object of this study contins the lrgest density of pigs of the Snt Ctrin Stte, which cuses lrge concentrtion of wste by unit of re, originting serious pollution problems tht ffect the region s hydro resources, minly by the lunching of wstes into the rivers nd strems tht flow down to the Urugui River, cusing ecologicl unblnces nd the increse of orgnic mtter long the wter courses, mong other problems. The smplings were collected in five sites (Figure 1): in the body of the reservoir (deep zone) nd in two brnches, in November/04, April/05 nd August/ Smpling nd chemicl nlysis Sediment smples were collected with Petersen grb dredge (stinless steel), pcked in plstic bgs, nd stored into freezers till they were processed by drying (t 80 C during 24 hours), grinding nd sieving (62 µm). The determintion of concentrtions of hevy metls ws bsed on Algrsmy (2006) where, three 250 mg portions (triplicte) of ech smple of grinded nd dried sediment (digested in n cid environment for lter nlysis) were prepred. Ech smple ws digested in teflon becker, with 10 ml of concentrted HNO 3 nd 10 ml of HF (48%), on n electric heting plte, nd left recting for 12 hours. Lter, 3 ml of HCLO 4 (70%) were dded, nd wrmed till 120 C, becoming lmost dry. After tht, 1 ml of HNO 3 ws dded to the smple, witing gin to become lmost dry. This procedure ws repeted more thn once. When the digestion ws over, 2 ml of HNO 3 10% nd bout 10 ml of deionized wter were dded, the solution ws trnsferred to volumetric blloon, mking volume of 25 ml; fterwrds, it ws used spectrophotometer (Vrin, model Spectr 220 FS) of tomic bsorption to nlyze the metls. The concentrtion of orgnic mtter (%) in the sediments ws obtined by incinerting 10 g of sediment t 500 C during 4 hours. The sttisticl nlysis of the dt ws mde using the one-wy nlysis of vrince (ANOVA), followed by Tukey test; p-vlues less thn 0.05 were considered significnt. The sttisticl progrm Sttistic 5.0 (Sttsoft, 2001) ws used for nlyses. 3. Results The sediment of the Itá reservoir cn be chrcterized s orgnic in most of the sites, demonstrted by the sites 1, 3, 4 e 5, becuse it contins more thn 10% of orgnic mtter in its dry weigh, ccording to Esteves (1998). On Tble 1 the results of the percentges of orgnic mtter disply minimum vlues of 8.57% for site 2, which corresponds to Rncho Grnde River. The centrl region of the reservoir, site 3, hs higher percentges of orgnic Act Limnol. Brs., 2009, vol. 21, no. 2, p

3 Distribution of metls in the sediment of the Itá Reservoir, Brzil Itá - SC P04 N Urugui River P05 Snt Ctrin P03 P02 W S E Rio Grnde do Sul Southern region Coordintes P S nd W P S nd W P S nd W P S nd W P S nd W Brzil P01 Urugui River Figure 1. Loction of the sites in the re of study. mtter thn the mrgins, displying mximum vlues of 17.29%. Tble 1 displys the verges of the concentrtions of Cr, Cu, Mn, Fe, Cd, Pb nd Zn from the sttions smpled in the Itá Reservoir nd the vlues of concentrtions of orgnic mtter (O.M). As comprtive for metls, we used the concentrtion limit estblished by the Conm Resolution 344/04 (Brsil, 2004), which is the only legl document in Brzil tht refers to sediment contmintions. Figures 2 nd 3 disply the men vlues nd stndrd devition (SD) of concentrtion ( ) of metls nd the nlysis of vrince of the sediments collected t the diverse sites of the reservoir. The metls which concentrtion displyed sttisticlly significnt difference for the Tukey test (p < 0.05) between the different sites, were only the Cu nd the Zn, in sites P2 nd P4 (Figure 2c nd 2d). 4. Discussion When the results of this study re compred with other reservoirs such s Slto Grnde (Americn-SP) studied by Dornfeld (2002), in wht reltes to orgnic mtter, we notice tht the verge of its percentges is very similr to the mximum concentrtion evluted in Slto Grnde (1.0 to 17.47%). If we compre it with other studies such s Znt (1999), with mximum vlues of 12.71%, it cn be verified tht the Itá reservoir contins high vlues of orgnic mtter. The orgnic mtter is closely linked to some hevy metls, minly Cu, Zn nd Fe, in the sediments of lkes. According to Forstner nd Wittmnn (1981), the orgnic mtter hs, for hevy metls, gret cpcity of dsorption; this ffinity cn concentrte metls in the environment, cusing n impct on it. According to the sme uthors (Cnells et l., 1999; Jordão et l., 1993) the orgnic mtter cn dsorb the metls, fter they re complexed (Srgentini Jr. et l., 2001), hevy metls re drgged towrds the sediment; s time goes by, nd due to their bio-ccumultive trits tht sediment tends to become effectively toxic for the ecosystem. The high concentrtions of Fe nd Mn in the sediment of the Itá reservoir re higher thn those reported for other reservoirs, such s the Slto Grnde Reservoir, studied by Dornfeld et l. (2004). High concentrtions of these elements re relted minly with the geochemicl chrcteristics of the wtershed dringe nd with n indequte soil mngement. According to Ker (1997), the region s soil is clssified s violet ltosoil, which is rich in Fe 2 O 3 nd possesses higher concentrtions of mngnese compred with the other ltosoils, nd lso, ccording to Moreir et l. (2004), the mngnese is found in high concentrtions in the micro-bsins soils where there is n intense ppliction of pigs dirt. Therefore, the nturl conditions linked to the breeding of pigs result in high concentrtions of Mn nd Fe, found in the studied re. The highest concentrtion of Cu nd Zn in site 4, with Act Limnol. Brs., 2009, vol. 21, no. 2, p

4 248 Boni, NC. et l. Tble 1. Comprison between the concentrtions of metls ( ) of the sediments collected in the Itá Reservoir s sites nd the limit estblished by the Conm Reservoir 344/04 (Brzil, 2004), nd the vlues of the concentrtion of orgnic mtter (O.M) in the Itá Reservoir. CONAMA Cr ( ) ± SD Cu ( ) ± SD Mn ( ) 2, , , , , ± SD Fe ( ) 82, , , , , ± SD 36, , , , , Cd ( ) ± SD Pb ( ) ± SD Zn ( ) ± SD O.M. (%) ± SD p = E5 1.6E5 1.4E5 1.2E5 1E p = b p = b b c p = b b d Men ± SD Figure 2. Men vlues nd stndrd devition (SD) of the concentrtions ( ) of Mn (), Fe (b), Cu (c) nd Zn (d) in the sediments smples of the different sites of the reservoir. The mens followed by the sme letters in the columns, for ech site, don t differ mong them ccording to the Tukey test. Act Limnol. Brs., 2009, vol. 21, no. 2, p

5 Distribution of metls in the sediment of the Itá Reservoir, Brzil p = p = p = b 045 c Men ± SD Figure 3. Men vlues nd stndrd devition (SD) of the concentrtions ( ) of Cr (), Cd (b) nd Pb (c) in the sediments smples of the different sites of the reservoir. significnt difference in comprison with sites 1, 3 nd 5, corrobortes the hypothesis of bd conservtion nd use of the region s soil. The levels of Cu were pproximtely seven times higher thn those estblished by CONAMA s Resolution 344/04 (Brsil, 2004), while the Zn levels were bout three times higher. Those concentrtions were lso higher thn the ones verified by Dornfeld (2002) in Slto Grnde Reservoir. Cu nd Zn re considered to be vitl biologicl elements, plying n enzymtic role in the physiologicl processes of the orgnisms, but they cn lso produce dngerous dmges to helth if consumed in high concentrtions (Cott, 2006). This study highlights the gret influence of frming ctivities, which re the cuse of higher concentrtions of Cu nd Zn (hevy metls which re directly relted with fertilizers nd wstes produced by the intensive breeding of pigs nd poultries). Exhibiting pttern different from other metls, the lowest concentrtions of Cd were obtined t site 1, while the highest ones were verified t site 3, without displying high vrition between the different sites. In literture there is no description for cdmium s n element tht brings benefits or tht is essentil for ll living beings. In contrst, it ccumultes in the tissues originting chronic nd severe helth effects, nd single 9.0 g dose my cuse deth. The led is toxic, bio-ccumultive metl tht cuses pollution, nd with no identified biologicl functions neither for plnts nor nimls (Cott, 2006). The highest concentrtions of Pb were lso observed t site 3 nd the lowest t site 5. For ll the smpled sites, the Pb ws the only metl tht displyed concentrtions which re in ccordnce to legisltion (Resolução 344/04 do CONAMA) which is 35.00, indicting tht the reservoir is not contminted by this metl. The vlues of the concentrtions obtined in this reserch demonstrte tht the mximums re often superior to the ones recommended by the legisltion, nd my confirm contminted system, with possible toxic effects for the qutic biot. The qulity of the wter of the Itá reservoir reflects the nturl conditions nd the mount of polluters generted by humn ctivities, which re lunched directly into the rivers tht flow into the lke. In both riverbnks, besides the trnsport of solids contining biocides s result of plnting ctivities there is lso n intensive pig nd chicken production. This study indictes tht the high levels both of orgnic mtter nd of hevy metls re connected with the intense frming ctivities nd with the use nd occuption of soils round the bsin. It is well-known fct tht high levels of some hevy metls originted by the use of gro-chemicls nd high vlues of orgnic mtter indicte the input of lrge mounts of wstes tht hve their origin in the frming ctivities tht surround the evluted re. Acknowledgements We thnk Jnet Higuti for suggestions, the technicins Mri E. K Anselmini nd Rquel Ternus for the lb nlyses. Support finncil by Fpesc (Fundção de Apoio à Pesquis Científic e Tecnológic do Estdo de Snt Ctrin) nd Unochpecó is grtefully cknowledged. References ALMEIDA, GA. nd WEBER, RR. Pesticids orgnoclordos em sedimentos do complexo esturino Lgunr Igupé Cnnéi e rio Ribeir de Igupé São Pulo, Brsil. In Anis do V Congresso de Geoquímic dos Píses de Língu Portugues e Anis do VII Congresso Brsileiro de Geoquímic, Porto Seguro: Universidde d Bhi, p ALAGARSAMY, R. Distribution nd sesonl vrition of trce metls in surfce sediments of the ndovi estury, west cost of Indi. Esturine, Costl nd Shelf Science, 2006, vol. 67, no. 1-2, p Act Limnol. Brs., 2009, vol. 21, no. 2, p

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