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)

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 influence of oil production. Three sites with an average distance between 0m (EM-1), 100m (EM-2), and 1000m (EM-3) of a submarine outfall-I (Guamaré—RN, Brazil) and another site (GA-1) with an average distance of 12000m 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 evaluated. There was no difference between the measurements obtained with two sets of DGT devices, those assembled with open or restrictive pore gel, respectively, showing that organic metallic species are not present near the submarine outlet. After 21day 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 demonstrated 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, 2.86ngmL−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. •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.