To evaluate the water quality along the continental shoresof Venezuela, where fishing communities exploit the clam Tivelamactroides, the concentration of heavy metals (Cu, Mn, Fe, Zn,Cd, Ni, Pb y Cr) was determined in superficial sediments,together with environmental factors (temperature, salinity,dissolved O2, pH, phytoplanctonic biomass, seston, and total Nand P) of the litoral waters of Playa Güiria on the northeasterncoast (Sucre State), and of Río Chico and Boca de Paparo (MirandaState), two localities on the central coast separated bysome 5km and influenced by the Tuy River. In Río Chico, andmainly in Boca de Paparo, the concentration of heavy metals inthe sediments (>18μg·g-1 Cu, >3μg·g-1 Cd, >5μg·g-1 Cr, >0.9μg·g-1Pb, >11μg·g-1 Ni) and the environmental factors (>28ºC,<5.6ml·l-1 dissolved O2, >55μmol·l-1 total N, >17μmol·l-1 total P)indicated the presence of polluted systems. This environmentaldamage was linked to the influence of the Tuy River, which flowsinto the sea at Boca de Paparo. The values for heavy metalswere higher than the values reported 14 year ago. In PlayaGüiria the values determinated did not show environmentalcontamination (0.03μg·g-1 Cu; 0.5μg·g Cd and no Cr, Pb or Niwere detected). Shore cleanup at Boca de Paparo and Río Chicois recommended, as these locations have dangerous sanitary andenvironmental conditions. Environmental conditions at PlayaGüiria allow for Tivela mactroides fishing.

Total concentrations and chemical forms of metals in superficial sediments of the MiddleOrinoco were determined with acetic acid solution 25% (v/v)/HNO3: HCl: HClO4 (3:2:1) solution,atomic absorption spectrometry with air acetylene flame and cold vapor technique. Totalvalues ranged from 8871 to 116759 μgFeg-1, 102.45 a 469.44 μgMn g-1; 0.93 to 17.64 μgCu g-1;4.46 to 17.48 μgNi g-1; 2.46 to 9.61 μgCo g-1; 42.56 to 181.45 μgZn g-1; 1.29 to 8.76 μgCr g-1; 0.03to 0.74 μgCd g-1 and 0.001 to 7.88 μgPb g-1. The metals were found to be strongly associated with the residual fraction minerals, more resistant iron oxihidroxides, metallic sulfides, and organicmatter. The values ranged from 7.50-99.29% Fe; 7.75-66.34% Mn; 22.55-98.89% Zn; 22.85-91.36% Ni; 4.20-85.03% Cu; 16.76-85.48% Co; 12.56-95.49 Cr; 7.50-99.29% Pb; 2.03-85.48%Cd). The values of metals adsorbed in the surface of particles, associated with carbonates andthe reactive manganese oxihidróxidos varied from 0.04-1.97% Fe; 4.15-71.59% Mn;0.86-3.83% Zn; 0-12.10% Ni; 1.05-14.97% Cu; 6.40-33.06% Co; 1.03-5.08% Cr; 0-1.78% Pb;0-22.97% Cd. The total concentration of Cu, Ni, Zn and Pb in some stations like the Cabrutaand Caicara of Orinoco cities are superiors to the reported for non contaminated sediments.

Resumen: Algunos aspectos geoquímicos de los sedimentos superficiales del litoral de la costa nororiental del Golfo de Cariaco, estado Sucre, Venezuela, son presentados en esta investigación. La estructura geológica del Golfo es tectónica con presencia de sistema de fallas, en donde los sedimentos del litoral norte pueden ser texturizados como arenosos por ser bastantes permeables en su mayoría y presentar un contenido hídrico promedio de 22,44%. Los contenidos de materia orgánica determinados fueron bajos con promedios de 7,63%, detectándose porcentajes de carbono orgánico de 0,97% y 21,97% de carbonatos de calcio. Se apreciaron concentraciones altas de fósforo (360,03 μg.g -1 ) y de nitrógeno total (396,29 μg.g -1 ), siendo la relación entre estos elementos de 1,09, indicando cierto grado de fertilidad orgánica. Las concentraciones de metales presentaron distribuciones discrepantes, con promedios para hierro de 3348,58 μg.g -1 , manganeso 14,63 μg.g -1 , níquel 13,68μg.g -1 , cinc 11,59μg.g -1 , cromo 10,23μg.g -1 , cobre 2,29μg.g -1 , cadmio 1,04 μg.g -1 y plomo 0,57 μg.g -1 , mostrándose contaminación, especialmente por cadmio. La no linealidad presentada por algunos metales como plomo, cobre, níquel y manganeso con el hierro, sugiere la existencia de entradas de tipo no natural, causadas por fuentes de origen antropogénico. Esta fuente probablemente está influenciada por descargas fluviales, industriales y por el aporte exógeno unidireccional desde la costa sur.Palabras claves. Golfo de Cariaco, estudio geoquímico, sedimentos.Abstract: This research presents some geochemical aspects of the marine surface sediments of the north coast of the Gulf of Cariaco, in the state of Sucre, Venezuela. The gulf has a tectonic structure and a fault system mainly featuring sandy sediments, most of which are quite permeable and have an average hydric content of 22.44%. The content of organic matter detected was low, averaging 7.63%, organic carbon and calcium carbonate commanding 0.97% and 21.97%, respectively. Contrarily, phosphorus and total nitrogen were high, 360.03 mg.g -1 for the former and 396.29 mg.g -1 for the latter, the total nitrogen to phosphorus ratio being 1.09, which indicates a certain degree of organic fertility. The metal concentrations presented different distributions, averaging 3548.58, 14.63, 13.68, 11.59, 10.23, 2.29, 1.04, and 0.57 mg.g -1 for iron, manganese, nickel, zinc, chromium, copper, cadmium, and lead, respectively, indicative of contamination, especially by cadmium. The nonlinearity with the iron presented by some metals such as copper, nickel, and manganese suggests the existence of anthropogenic influxes, probably swayed by river-borne industrial contributions, including the exogenous discharges running seawards from the south coast.

RESUMENSe analizó por Espectrofotometría de Absorcion Atomica de llama el contenido de Fe, Mn, Cu, Cr, Ni, Zn, Cd y Pb en tejidos musculares de peces y crustáceos de la laguna de Unare, estado Anzoátegui, Venezuela. Adicionalmente, se determinaron los niveles en el material en suspension del agua y en el sedimento para detectar posibles impactos en el ecosistema. En el agua, las concentraciones medias de metales fueron bajos (0,104-0,53 µmol/L Fe; 0,004-0,06 µmol/L Mn; 0,002-0,028 µmol/L Zn; 0,004-0,012 µmol/L Cr; no detectado-0,011 µmol/L Ni y no detectado-0,001 µmol/L Cd). En el sedimento se evidencia intervención antropogénica con valores medios que decrecen Mn (516,37)>Zn (127,49)>Ni (52,41)>Cr (51,69)>Cu (41,13)>Pb (29)>Cd (1,51 µg/g) y que superan los niveles establecidos para sedimentos no contaminados. En los tejidos de los organismos se detectó la presencia de metales tóxicos como el plomo y cadmio que superan los 0,16 y 0,04 µg/g, respectivamente, al igual que el zinc que alcanza niveles elevados que sobrepasan 17 µg/g en la mayoría de las especies. Las pruebas estadísticas de ANOVA (P<0,05) indican discrepancias en las concentraciones metales en los tejidos por los diferentes géneros y especies, al igual que en los valores de los individuos de la misma especie (Cathorops spixii) que habitan dentro y fuera de la laguna. Los niveles son mayores en los habitantes del interior de la laguna evidenciando fenóme-nos de bioacumulación. La investigación confirman un progresivo deterioro ambiental de la laguna y de las especies ícticas de este ecosistema que son comercializadas por las poblaciones aledañas a la laguna, las cuales sustentan su economía de su explotación pesquera.Palabras clave: Peces, tejidos, metales, laguna costera, degradación. ABSTRACTThe content of Fe, Mn, Cu, Cr, Ni, Zn, Cd and Pb in muscle tissues of fish and crustaceans from the Unare lagoon (Laguna de Unare) in the state of Anzoátegui, Venezuela, was analyzed by flame Atomic Absorption Spectrometry. The levels of these metals present in suspended material of the water and in sediments were also determined in order to detect possible impact on the ecosystem. The mean concentrations in the water were low ( ), all of which are greater than established levels for uncontaminated sediments. Toxic metals were detected in the examined organisms, such as lead and cadmium with levels above 0.16 and 0.04 µg/g, respectively, and zinc with levels greater than 17 µg/g in the majority of the species. ANOVA statistical tests (P < 0.05) show discrepancies in the concentrations or the metals in the tissues of the different genera and species, as well as in the values for individuals of the same species (Cathorops spixii) which live inside and outside of the lagoon. The levels are higher in those which live within the lagoon, 73Recibido: 02 /

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