Changes in Cd and Zn bioavailability upon an experimental resuspension of highly contaminated coastal sediments from a tropical estuary

Abstract

Bioavailability evaluations can be an important tool to determine the quality of dredging sediments. Sequential extractions are commonly used to assess the different chemical forms of trace metals in coastal sediments; however, sometimes they are expensive and timeconsuming. Additionally, these analyses do not represent possible changes due to resuspension during and after dredging activity. Newer, easier options to evaluate bioavailability are necessary to understand and preview bioavailability changes resulting from trace metals in dredging and disposal areas. This study aims to evaluate changes in Cd and Zn bioavailability due to sediment resuspension in a highly contaminated area in Sepetiba Bay, Brazil. Twelve surface sediment samples from this location were submitted to a resuspension experiment during two different time intervals (1 and 24 h). The extraction of potentially bioavailable (1 mol L -1 HCl-extractable) fractions and strongly bound (concentrated HNO 3 -extractable) fractions were sequentially carried out. More than 50 % of the concentrations were in potentially bioavailable fractions. Bioavailability change indexes were proposed; these were estimated as relative changes in bioavailability percentage after resuspension. However, two of these stations presented increases in the Cd and Zn HCl-extractable fractions after sediment resuspension above effects range low and effects range medium National Oceanic and Atmospheric Administration which are the same limits adopted for Brazilian environmental jurisdiction. Positive correlation of Zn and Cd with TOC in strongly bound fractions evidenced the importance of organic matter binding to preserve metals in this fraction. Fe and Mn partitioning was a major geochemical control on bioavailability of Cd and Zn upon short-time resuspension periods.

Separação De Asfaltenos Por Cromatografia Em Placa Preparativa E Análise Por Cg-Em De Biomarcadores Ocluídos

“…No Brasil, estudos sobre o processo de remobilização dos contaminantes pela ressuspensão de sedimentos podem ser aproveitados para complementar, ou mesmo subsidiar a revisão dos parâmetros recomendados pela norma de licenciamento de dragagens (Resolução CONAMA 454/2012). A preocupação em relação ao efeito de distúrbios físicos sobre a mobilização de metais e nutrientes tem sido amplamente discutida internacionalmente (WARNKEN et al, 2003;NIENCHESKI;JAHNKE, 2004), mas investigações sobre esta forma de liberação de contaminantes para a coluna d'água e consequentemente para a biota local ainda é relativamente pouco difundido (por exemplo, MADDOCK et al, 2007;TORRES et al, 2009;URBAN et al, 2010;MACHADO et al, 2011, MONTE et al, 2015, RODRIGUES et al, 2017. (MOLISANI et al, 2004;GOMES et al, 2009).…”

“…A atividade portuária necessita de dragagens periódicas que remobilizam os sedimentos superficiais e de fundo (CAPPUYNS et al, 2006;MONTE et al, 2015). Essa remobilização pode afetar a biodisponibilidade dos metais ligados aos sedimentos, pois aqueles que estavam em fases não biodisponíveis, após um evento de ressuspensão na coluna d'água oxidante, podem passar para fases dissolvidas e/ ou para fases sedimentares mais disponíveis ficando mais biodisponíveis à biota local (MORSE, 1994;MACHADO et al, 2011).…”

Metal Bioavailability in Contaminated Estuarine Sediments from a Highly-Impacted Tropical Bay

“…The percent of HCl-Me i elatio to ΣMe oted as %HCl-Me) was adopted as the relative estimate of metal bioavailability. 13,14 Sediment sand content was estimated by using a CILAS particle-size meter.…”

Trace metal distribution in white shrimp (Litopenaeus schmitti) tissues from a Brazilian coastal area

“…It is suggested that these metals are attached to the fine fraction of sediment, organic matter, and sulfides, mainly in eutrophic areas as Guanabara Bay and Sepetiba Bay (Machado et al 2010;Ribeiro et al 2013;Fiori et al 2013;Sabadini-Santos et al 2014a, b;Monte et al 2015). This may also explain the bioaccumulation of metals in Ilha Grande Bay's decapods (Seixas et al 2014).…”