Heavy metal determination in surface sediment allows pollutant assessment when the detection in the water column is not possible. Geoaccumulation Index (Igeo) and the Sediment Quality Guidelines (SQGs) were used to quantitatively evaluate the degree of heavy metal contamination in fluvial sediments. Both of these methods had already been used by several authors and the generated indexes allowed a good comparison parameter. In the present study, heavy metal in sediments (Mn, Zn, Cd, Cr, Cu, Pb and Ni) were analyzed in 14 sampling points, distributed in the upper watercourse of Subaé river, Feira de Santana -BA, in two field campaigns in order to compare dry and wet seasons. The quantification of heavy metal contents was measured by flame atomic absorption spectrometer. The heavy metal levels in the sampling points were low when compared to the global reference values for world sediments. Cadmium concentrations were always below the detection limit of the used spectrometer, and the relative abundance of the studied metals was the following: Mn>Zn>Pb>Cu>Cr>Ni. The variation range of each element concentrations was: Mn 69.3 and 266 mg Kg -1 ; Zn 30.7 and 426 mg Kg -1 ; Pb 6.00 and 63.6 mg Kg -1 ; Cu 4.26 and 66.2 mg Kg -1 ; Cr 3.24 and 52.9 mg Kg -1 ; Ni 1.96 and 24.7 mg Kg -1 . These results are indicating low contamination risk to biota, despite of the fact that some points presented moderate risk of toxicity. The Igeo ranged from unpolluted (Zn, Mn, Cr, and Ni) to slightly polluted (Pb and Cu) in the assessed sediments. The different approaches to geochemical information treatment allow a wide and coherent debate about the environmental risk of heavy metals from anthropogenic diffuse sources.

Abstract:The current study aims to evaluate the ability of different macrophyte species found in Subaé River headwaters to bioaccumulate heavy metals as well as to investigate whether the found concentrations reflect the environmental quality state in the region. Macrophyte collections were held in February and August 2012 in four points of Subaé Lagoon (one of Subaé River headwaters). The samples were dried, ground, sieved and digested using nitric acid and perchloric acid. The reading of the metals was determined by Flame Atomic Absorption Spectrophotometry (FAAS). The metal accumulation order varied according to the analyzed species, but manganese was the metal that showed the highest concentrations at all collection points. Although only Zn and Cu concentrations in water and macrophytes reflect significant bioaccumulative potential, there was high positive correlation regarding Mn and Pb (0.87 and 0.70, respectively). Typha dominguensis (Mn, Cu and Zn) and Acroceras zizanioides (Pb, Cr and Ni) were the species that stood out in relation to metal concentrations. Therefore, it is suggested that these species should be used in future environmental monitoring studies specific to Subaé River headwaters -Feira de Santana, Bahia.Keywords: Heavy metals; macrophytes; phytoremediation; bioaccumulation. ResumoO objetivo do presente estudo foi avaliar a capacidade de bioacumulação de metais pesados em diferentes espécies de macrófitas presentes nas nascentes do rio Subaé, Feira de Santana-Bahia e evidenciar se as concentrações encontradas refletem o estado de qualidade ambiental da região. As coletas das macrófitas foram realizadas em Fevereiro e Agosto de 2012, em quatro pontos da Lagoa do Subaé (uma das nascentes do rio Subaé). As amostras foram desidratadas, moídas, peneiradas e digeridas com ácido nítrico e ácido perclórico. A análise dos metais foi realizada empregando a espectrofotometria de absorção atômica por chama (EAA). A ordem de acumulação de metais variou conforme as espécies analisadas, porém o manganês foi o metal que apresentou as maiores concentrações, em todos os pontos de coleta. Apesar de apenas as concentrações de Zn e de Cu na água e nas macrófitas refletirem o potencial bioacumulador significativo, houve correlação positiva alta para Mn e Pb (0,87 e 0,70, respectivamente). As espécies que mais se destacaram em relação às concentrações de metais foram a Typha dominguensis (Mn, Cu e Zn) e a Acroceras zizanioides (Pb, Cr e Ni). Portanto, sugere-se que essas espécies sejam utilizadas em futuros estudos de monitoramento ambiental, específicos para as nascentes do rio Subaé-Feira de Santana, Bahia.Palavras-chave: Metais pesados; macrófitas; fitorremediação; bioacumulação.