Profiles of Benzothiazoles and Benzotriazoles in Marine Sediments from Trondheimsfjorden: The Associations with Trace Elements and Polycyclic Aromatic Hydrocarbons

Abstract

Sedimenter kan fungere som en sink for miljømessige forurensninger der kontaminanter kan bli lagret, noe som fører til sekundære utslipp i akvatiske systemer. Dette gjelder spesielt for lipofile forurensninger, som polysykliske aromatiske hydrokarboner (PAHer) som raskt adsorberes til partikler. Selv om benzothiazoler (BTHer) og benzotriazoler (BTRer) ofte detekteres i overflatevann og grunnvann, er det derimot lite kunnskap om forekomsten av disse forbindelsene i sedimenter.

I denne studien ble væskekromatografi tandem massespektrometri (LC-MS/MS) brukt for simultan bestemmelse av ni BTHer og syv BTRer i sedimentprøver fra Trondheimsfjorden. De analyserte benzothiazolene inkluderer benzothiazole, 2-chlorobenzothiazole, 2-hydroxybenzothiazole, 2-mercaptobenzothiazole, 2-methylthiobenzothiazole, 2-hiocyanomethylthiobenzothiazole, 2-methylbenzothiazole, 2-aminobenzothiazole, og 2-morpholin-4-yl-benzothiazole, mens de anlyserte benzotriazolene inkulderer benzotriazole, 4-methyl-1-H-benzotriazole (tolyltriazole), 5,6-dimethyl-1-H-benzotriazole (xylyltriazole), benzotriazole-5-carboxylic acid, 5-chloro-1-H-benzotriazole, 5-amino-1-H-benzotriazole og 1-hydroxybenzotriazole.I tillegg ble 16 PAHer analysert i sedimentene ved hjep høypresisjonsvæskekromatografi med fluorescensdeteksjon (HPLC-FLD). Dette ble gjort for å etablere forskjeller i konsentrasjonsprofiler mellom de tre gruppene av organiske forurensninger.

Analyse av sporelementer i prøvene ble gjort med induktivt koblet plasma massespektrometri for å se på assosiasjoner mellom organiske forurensninger og sporelementer. Dette studiet demonstrerte forekomsten av BTHer, BTRer og PAHer i sedimentprøver, som ble funnet til å variere fra 9,32-152 ng/g for Σ(9)BTHer (median: 62,3 ng/g), mens konsentrasjonen varierte fra 3,48-67,9 ng/g for Σ(7)BTRer (median: 7,73 ng/g). Σ(13)PAHer ble funnet til å spenne fra 29,1-548 ng/g (median: 351 ng/g). Dette er første gang konsentrasjonsprofiler mellom disse tre gruppene av organiske miljøgifter er rapportert sammen, og den høyere forekomsten av PAHer i sedimentene er mest sannsynlig et resultat av ulike fysisk-kjemiske egenskaper.

Ved hjelp av prinsipalkomponentanalyse (PCA) var det mulig å se noen assosiasjoner mellom de ulike kontaminantene og prøvetakingssted. PCAen indikerte en assosiasjon mellom PAHer og TTR og XTR, mens det ble funnet at BTR var korrelert med flere ulike spormetaller. PCAen indikerte også at BTR ble funnet mest ved stasjonen lengst fra kystlinjen, og det ble foreslått at dette kan ha en sammenheng med båttrafikk i dette området. Det kan også skyldes ulike egenskaper hos sedimentene i dette området.

Sediments can act as a sink for environmental pollutants where contaminants can be stored, causing secondary emissions in aquatic systems. This is especially true for lipophilic contaminants, such as polycyclic aromatic hydrocarbons (PAHs), which are rapidly adsorbed to particulate matter. However, despite the frequent detection of benzothiazoles (BTHs) and benzotriazoles (BTRs) in surface waters and ground waters, knowledge about their occurrence and profiles in sediments is still scarce.

In this study, liquid chromatography tandem mass spectrometry (LC-MS/MS) was used for the simultaneous determination of nine BTHs and seven BTRs in sediment samples from Trondheimsfjorden. The target benzothiazoles were benzothiazole, 2-chlorobenzothiazole, 2-hydroxybenzothiazole, 2-mercaptobenzothiazole, 2-methylthiobenzothiazole, 2-thiocyanomethylthiobenzothiazole, 2-methylbenzothiazole, 2-aminobenzothiazole, and 2-morpholin-4-yl-benzothiazole, while the target benzotriazoles were benzotriazole, 4-methyl-1-H-benzotriazole (tolyltriazole), 5,6-dimethyl-1-Hbenzotriazole (xylyltriazole), benzotriazole-5-carboxylic acid, 5-chloro-1-H-benzotriazole, 5-amino-1-H-benzotriazole and 1-hydroxybenzotriazole. In addition, 16 PAHs were measured in the sediment samples by high-performance liquid chromatography with fluorescence detection (HPLC-FLD) in order to establish differences in occurrence profiles for these three groups of organic contaminants. The analysis of trace elements in the samples was done by inductively coupled plasma mass spectrometry (ICP-MS), to establish possible associations between organic contaminants and trace elements.

This study demonstrated the occurrence of BTHs, BTRs, and PAHs in sediment samples, which were found to range from 9.32-152 ng/g for Σ(9)BTHs (median: 62.3 ng/g), while the concentrations ranged from 3.48-67.9 ng/g for Σ(7)BTRs (median: 7.73 ng/g). Σ(13)PAHs was found to range from 29.1-548 ng/g (median: 351 ng/g). This is the first time concentration profiles between these three groups of organic contaminants are reported together, and the higher abundance of PAHs in sediments is thought to be a result of differences in physicochemical properties.

Making use of principal component analysis (PCA) it was possible to see some associations between the different contaminants, and the sampling sites. The PCA indicated associations between the PAHs and TTR and XTR, while BTR were found to be associated with several trace metals. The PCA also indicated that BTR were found in highest abundance at the site furthest away from the shoreline, and it was proposed that this might be due to commercial ship traffic in this area or due to different properties of the sediments.