Evaluation of Cu potential bioavailability changes upon coastal sediment resuspension: an example on how to improve the assessment of sediment dredging environmental risks
- 272 Downloads
Metal bioavailability-based sediment quality analysis, inferred from geochemical partitioning data, may contribute to improve sediment management policies. This is important because decision-making processes should not give similar priorities to sediments offering contrasting environmental risks associated to metal bioavailability. However, current uses of Sediment Quality Guidelines (SQGs) as interpretive tools to support decisions about dredging-related activities have not considered the changes in metal bioavailability upon sediment resuspension.
Sediments from a Cu-contaminated site in Guanabara Bay (Brazil) were submitted to 16-h resuspension experiments in estuarine water to assess the susceptibility of Cu mobilization to the dissolved phase and alteration in the solid phase partitioning between a potentially bioavailable (1 mol/l HCl-extractable) phase and concentrated HNO3-extractable phase.
After sediment resuspensions, dissolved Cu levels became slightly lower (in a surface water-resuspension treatment) or slightly higher (in a bottom water-resuspension treatment). In both treatments, the 1 mol/l HCl-extractable solid phase concentrations changed from seven times lower to two times higher values than an SQG adopted in Brazilian legislation. This change was explained by a transition from concentrated HNO3-extractable phases to reactive HCl-extractable phases upon resuspension.
An evaluation of metal susceptibility to present geochemical partitioning changes, as can be inferred from HCl-extractable fraction analyses before and after resuspension experiments, is recommended as an additional criterion to assess environmental risks of sediment dredging in relation to resuspension-sensitive metals, such as Cu.
KeywordsSediment quality Copper contamination Sediment resuspension Potential bioavailability
The authors thank the critical comments from two anonymous referees, the financial support from Rio de Janeiro State Research Foundation (FAPERJ) and Brazilian Research Council (CNPq), and a post-doctoral grant from Brazilian Ministry of Education (PNPD/CAPES) to A.P.C. Rodrigues.
- CONAMA (2004) Procedures for the evaluation of dredging materials in Brazilian jurisdictional waters. Resolution #344/2004. Diário Oficial da República Federativa do Brasil, Brasília (in Portuguese)Google Scholar
- Huerta-Diaz MA, Delgadillo-Hinojosa F, Hernández-Ayón M, Segovia-Zavala JA, García-Esquivel Z, López-Zárate H, Siqueiros-Valencia A, Galindo-Bect S (2008) Diagnosis of trace metal contamination in sediments: the example of Ensenada and El Sauzal, two harbors in Baja California, Mexico. Mar Environ Res 66:345–358CrossRefGoogle Scholar
- Maranho LA, Abreu I, Santelli RE, Cordeiro RC, Soares-Gomes A, Moreira LB, Morais RD, Abessa DMS (2009) Sediment toxicity assessment of Guanabara Bay, Rio de Janeiro, Brazil. J Coast Res SI56:851–855Google Scholar
- USEPA (1994) Microwave assisted acid digestion of sediments, sludges, soils and oils. USEPA Method 3051Google Scholar