Critical Aspects in the Determination of the Antifouling Compound Dichlofluanid and its Metabolite DMSA (N,N-dimethyl-N'-phenylsulfamide) in Seawater and Marine Sediments

Abiotic fate of tolylfluanid and dichlofluanid in natural waters

To prevent the growth of unwanted organisms on ship hulls, antifouling paints, containing biocides such as tolylfluanid (N-[dichlor(fluor)methyl]sulfanyl-N-(dimethylsulfamoyl)-4-methylaniline) and dichlofluanid (N-(dichlorfluormethylthio)-N',N'-dimethyl-N-phenylsulfamid), are applied. There are concerns over their occurrence and fate in the marine environment due to long-term immersion in water. In the present study, the hydrolysis and photolysis of these compounds were investigated. Results showed that tolylfluanid and dichlofluanid hydrolyzed completely to their respective hydrolysis products DMST (N,N-dimethyl-N'-p-tolylsulfamide) and DMSA (N,N-dimethyl-N'-phenylsulfamide) in coastal water within 24 h. Furthermore, the transformation of tolylfluanid and dichlofluanid under natural sunlight was determined in selected marine waters (coastal water and sea water) in comparison to deionized water. The experiments revealed that photodegradation rates of DMST and DMSA in coastal water were higher than in sea water or deionized water. The indirect phototransformation of the hydrolysis products with selected reactive species (triplet state organic matter, singlet oxygen, and hydroxyl radicals) showed that DMST and DMSA mainly display triplet reactivity. The measured half-lives of the hydrolysis products in natural waters were 2.7 and 23 days, with DMST being considerably faster transformed than DMSA. However, several direct and indirect photoproducts have been newly identified and measured. DMS (N,N-dimethylsulfamide), was identified as the major phototransformation product in natural waters. It is generated by indirect photodegradation processes and exhibits potential persistence in the environment.

Occurrence and partitioning of antifouling booster biocides in sediments and porewaters from Brazilian Northeast

Fouling organisms attach and grow on submerged surfaces causing several economic losses. Thus, biocides have been introduced in antifouling paints in order to avoid this phenomenon, but their widespread use became a global problem, mainly in ports, leisure and fishing boat harbors, since these substances can be highly toxic to non-target organisms. The occurrence and environmental behavior of antifouling biocides are especially unknown in some peculiar regions, such as Amazon areas. Thus, the aim of this work was to evaluate, for the first time, levels and the partitioning behavior of the antifouling organic biocides irgarol, diuron and also stable degradation products of dichlofluanid and diuron (DMSA and DCPMU, respectively) in sediments and porewaters from a high boat traffic area located in the Northeast of Brazil, a pre-Amazon region. Our results showed high concentrations of irgarol (<1.0-89.7 μg kg^-1) and diuron (<5.0-55.2 μg kg^-1) in sediments. In porewater, DCPMU (<0.03-0.67 μg L^-1) and DMSA (<0.008-0.263 μg L^-1) were the mainly substances detected. High K_d and K_oc obtained for both irgarol and diuron showed a partitioning preference in the solid phase. This work represents one of the few registers of contamination by antifouling substances in Amazonian areas, despite their environmental relevance.

Assessment of organotin and tin-free antifouling paints contamination in the Korean coastal area

Twelve organotins (methyl-, octyl-, butyl-, and phenyl-tin), and eight tin-free antifouling paints and their degradation products were measured in marine sediments from the Korean coastal area, and Busan and Ulsan bays, the largest harbor area in Korea. The total concentration of tin-free antifouling paints was two- to threefold higher than the total concentration of organotins. Principal component analysis was used to identify sites with relatively high levels of contamination in the inner bay area of Busan and Ulsan bays, which were separated from the coastal area. In Busan and Ulsan bays, chlorothalonil and DMSA were more dominant than in the coastal area. However, Sea-Nine 211 and total diurons, including their degradation products, were generally dominant in the Korean coastal area. The concentrations of tin and tin-free compounds were significantly different between the east and west coasts.

Analytical methods for the determination of common booster biocides in marine samples

Booster biocides are organic compounds that are added to antifouling copper-based paints to improve their efficacy. Due to their widespread use, they are common pollutants of marine ecosystems. Some of these compounds show acute and chronic toxic effects in non-targeted organisms at concentrations as low as ng L−1. The determination of these compounds is therefore important, and for some, which are prioritized in the EU water framework directive, a necessity. Because of their low concentrations and the matrix effect, these contaminants often require a suitable sample preparation step (extraction/pre-concentration) prior to chromatographic determination. The aim of the present article is to review extraction and chromatographic methodologies related to the determination of common booster biocides in marine samples published in the scientific literature. These methodologies include liquid-liquid extraction (LLE), solid phase extraction (SPE), solid phase microextraction (SPME), single drop microextraction (SDME), Soxhlet extraction, microwave-assisted extraction (MAE), supercritical fluid extraction (SFE) and pressurized liquid extraction (PLE) as extraction methods, and both gas and liquid chromatography as determination techniques.

Antifouling biocides in discarded marine paint particles

Antifouling paint fragments collected from marinas and leisure boat maintenance facilities and in the vicinity of abandoned boats have been chemically characterised. High concentrations of Cu (23-380mgg(-1)) and Zn (14-160mgg(-1)) in the samples (n=14) are consistent with the use of these metals in the principal biocidal and non-biocidal pigments in contemporary antifouling formulations. Up to about 2% and 7% of the respective metals were solvent-extractable, suggesting that organo-forms of Cu and Zn (e.g. pyrithiones) were also present. Of the organic biocides, dichlofluanid was present in most samples and at concentrations up to about 20mgg(-1). Chlorothalonil and Irgarol 1051(R) were only detected in one and four cases, respectively, and Sea Nine 211(R) was not detected in any sample. Results are discussed in terms of UK legislation regarding biocide usage and the likely effects and fate of discarded paint particles in coastal environments where boats are repaired or moored.

The environmental fate and effects of antifouling paint biocides

Antifouling (AF) biocides are the active ingredients in AF paints that prevent the settlement, adhesion and growth of organisms to a painted surface. A wide range of chemicals are used as AF biocides, which have very different physico-chemical properties and therefore differing environmental fates, behaviour and effects. Copper has been used as an antifoulant for centuries and extensive research has been performed to understand how copper speciation influences bioavailability and toxicity. For biocides that have been widely used over a number of decades, for example Irgarol 1051 and diuron, there are a large amount of environmental data in the public domain, including for their respective metabolites, that allows their environmental safety and potential risk to the environment to be assessed. For other biocides such as dichlofluanid, DCOIT (SeaNine 211) and zinc/copper pyrithione, there is a good understanding of their fate and effects. However, few monitoring studies have been performed and not so much is known about the fate and effects of their metabolites. There are also new or candidate biocides such as triphenylborane pyridine, Econea, capsaicin and medetomidine for which there is very little information in the public domain. This review provides an overview of the environmental fate and occurrence data that are in the public domain for AF biocides and provides some insight into the effects of these compounds on non-target organisms.