Measurements of labile Cd, Cu, Ni, Pb, and Zn levels at a northeastern Brazilian coastal area under the influence of oil production with diffusive gradients in thin films technique (DGT) João M. de Souza a , Amauri A. Menegário b, ⁎, Marcus A.G. de Araújo Júnior a , Eleine Francioni a a PETROBRAS/CENPES/PDEDS/AMA, Av. Horácio de Macedo, 950, 21941-915 Rio de Janeiro, RJ, Brazil b UNESP—Univ Estadual Paulista, CEA—Centro de Estudos Ambientais, Av. 24-A, 1515, 13506-900 Rio Claro, SP, Brazil HIGHLIGHTS • DGT was used for monitoring metals in an area under the influence of oil production. • Effects of deployment time, gel porosity and thickness were evaluated. • Sites in northeast Brazil coastal area near to a submarine outfall were studied. • It was demonstrated that biofilm interference on DGT measurements was negligible. • Data suggest no contamination in the area under the influence of oil production. abstract article info Article history: Received 9 April 2014 Received in revised form 27 August 2014 Accepted 31 August 2014 Available online xxxx Editor: Daniel A. Wunderlin Keywords: Passive sampler Oil refinery Oil production Metal Labile In this work, the ability of the diffusive gradients in thin films technique (DGT) was evaluated for monitoring the concentrations, and estimating the availability, of metals at a northeastern Brazilian coastal area under the influ- ence of oil production. Three sites with an average distance between 0 m (EM-1), 100 m (EM-2), and 1000 m (EM-3) of a submarine outfall-I (Guamaré—RN, Brazil) and another site (GA-1) with an average distance of 12000 m east of Outfall I, near the city of Galinhos, were studied. DGT units were deployed at the same sites in three campaigns from July, 2010 to June, 2011. Effects on the accuracy of analytical results regarding the deployment time, gel porosity, and thickness were eval- uated. There was no difference between the measurements obtained with two sets of DGT devices, those assem- bled with open or restrictive pore gel, respectively, showing that organic metallic species are not present near the submarine outlet. After 21 day deployments in a region (near Submarine Outfall I) that receives produced waters that have been treated, there was evidence of biofilm formation on DGT membranes. However, it was demon- strated that the biofilm interference with DGT measurements was negligible. Data found in this work show that total concentrations of Cd, Cu, Pb, Ni, and Zn in seawater samples collected at sites GA-1 and EM-1 in two campaigns were below 0.33, 1.67, 0.47, 0.70, 2.86 ng mL -1 respectively. For the first time, labile levels of Cd, Cu, Pb, Ni, and Zn in an area under the influence of oil production were determined. DGT measurements allowed the verification of the effects of temporal variation on levels of Zn and Ni. There were no effects of spatial variations on levels of Cd, Cu, Ni, Pb, and Zn at the four studied sites, suggesting no contamination of these metals at the northeastern Brazilian coastal area investigated in this work. © 2014 Published by Elsevier B.V. 1. Introduction Although there are several economic activities along the northern coast of Rio Grande do Norte, the oil industry is preeminent and, poten- tially, can emit contaminants to the marine environment. The oil production area, called Potiguar Basin, is 40% onshore (3000 small pro- duction wells) and 60% offshore (34 production platforms) (PETROBRAS, 2006). The main residue produced in the extracted oil is water, known as “produced water,” which is often associated with the extracted oil. This effluent is considered as the most significant pollutant, especially regarding the volume, which is significant and growing, due to the maturity of the deposits and use of secondary recovery processes Science of the Total Environment 500–501 (2014) 325–331 ⁎ Corresponding author. Tel./fax.: +55 1935269491. E-mail address: amenega@rc.unesp.br (A.A. Menegário). http://dx.doi.org/10.1016/j.scitotenv.2014.08.117 0048-9697/© 2014 Published by Elsevier B.V. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv