Passive sampling-derived aqueous concentrations of organotins and booster biocides in the largest Port of South America (Southeastern Brazil)

Abstract

Organotin compounds (OTs) used to be the most widely used biocide in antifouling paint systems, but the International Maritime Organization (IMO) banned them because of their high environmental toxicity to non-target organisms. Currently, at least 25 active ingredients are being employed as biocides in antifouling paint formulations. In the present study, silicone rubber-based passive sampling was used to determine the freely dissolved concentrations (C_w) of 6 OTs and 4 booster biocides in the water column at the entrance of Santos Port's main navigation channel, the largest Port of South America (southeastern Brazil). Fifteen sampling events of ∼45 days long were conducted over 2 years. C_w of OTs ranged from 1.1 to 2.5 ng Sn L⁻¹ for monobutyltin (MBT), 0.2 to 4.7 ng Sn L⁻¹ for dibutyltin (DBT), and 0.06 to 0.7 ng Sn L⁻¹ for tributyltin (TBT), while triphenyltin (TPhT), diphenyltin (DPhT), and monophenyltin (MPhT) were always below their limits of detection (<LOD). For booster biocides, C_w ranged from 3.9 to 6.3 ng L⁻¹ for diuron, 0.03 to 0.49 ng L⁻¹ for Irgarol, <0.55 to 44.3 ng L⁻¹ for DCOIT, and <0.01 to <0.02 ng L⁻¹ for dichlofluanid. Levels found in the water column are likely explained by a combination of sources, including simultaneous releases from marinas and shipyards located in adjacent areas, dredging operations, intense vessel traffic in the Santos Port, and desorption from APPs previously released along sediments of the Santos-São Vicente Estuarine System (SSES). Although OTs and booster biocide levels in the Port of Santos were relatively lower than in other studies worldwide, levels detected for TBT, DCOIT, and diuron may pose a risk to non-target organisms.