Prioritization of organic contaminants in coastal and polar environments using non-target screening analysis

Abstract

More than 120 million chemicals have been registered in the Chemical Abstracts Service (CAS) database, and the widespread use of various organic chemicals from land-based human activity means that they eventually reach the marine environment. Although a few chemicals have been regulated by international and domestic authorities, a scientific method of prioritizing emerging pollutants should be developed to effectively manage emerging pollutants in the marine environment . In this study, an occurrence-based method for this using non-target screening analysis (NTSA) with gas chromatography/quadrupole-time-of-flight (GC/Q-TOF) was developed . To optimize the GC/Q-TOF conditions, an Agilent GC 7890B coupled with Q-TOF 7200 with an Agilent 7693 autosampler were used. The Q-TOF was operated in electron ionization (EI) mode with the ionization voltage set at 70 eV. The Q-TOF mass spectrometer (MS) was operated at 100 mS/spectrum in the mass range m/z 50-600 and the resolution was approximately 13,000 at m/z 131 and 17,000 at m/z 502 in 4Ghz high resolution mode. The transfer line and ionization source temperature were set at 280°C and 230°C, respectively. A DB-5MS UI (30 m x 0.25 mm i.d.; 0.25 μm film thickness) was used to separate the target compounds. The oven temperature was programmed at 80°C for 1 min and increased to 200°C at 10°C/min, and then finally ramped at 5°C/min to 300°C and held for 5 min. The carrier gas was helium at a constant flow rate of 1mL/min. A solvent delay of 4 min was used to prevent damage to the capillary column and ion source filament. MassHunter Quantitative Analysis B.05 and Unknown Analysis B.05 were applied for the treatment of the data, and the National Institute of Standards and Technology (NIST) Library (ver. 2009) was used for matching the non-targeted compounds. In order to remove matrix interference from the marine samples, four types of solid phase extraction (SPE) cartridge: (a) 150 mg hydrophilic liphophilic balanced copolymer (HLB), (b) 500 mg C18-bonded silica (C18), (c) 1 g silica gel, and (d) 500 mg florisil cartridges were examined and compared. The average recoveries for 208 target contaminants (well-known in the Korean coastal environment) were estimated to be 78%, 65%, 72%, and 64% for the HLB, C18, silica, and florisil cartridges, respectively. Based on the recoveries and effectiveness in removing matrix-related compounds, the HLB cartridge (150 mg) was chosen for the analysis. Surface seawater, sediment, and biota samples were collected from the Ulsan Bay in Korea in 2014. A total ion chromatogram (TIC) was used to identify 208 target compounds by matching retention times to monitor and confirm ions using the library. Among the 208 target contaminants, 68, 97, and 106 compounds were detected in seawater, sediment, and biota samples, respectively. After target screening analysis , the NTSA was also performed to identify unknown chemicals in the various media matrices. The TIC chromatogram was deconvoluted using the Unknown Analysis software, and the mass spectrum of each compound from the resulting deconvoluted ion chromatogram (DIC) was used to identify non-targeted compounds using the NIST library. In this study, approximately 4000 compounds were detected in the seawater, sediment, and biota samples. From the target screening analysis, the predominantly identified compounds were polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs), which are monitored contaminants in the Korean coastal environment by the government institute . For the non-target screening analysis, several chemical groups such as siloxanes, phthalates, musk fragrances, organophosphate flame retardants (OPFRs), and chlorinated flame retardants were identified from the various media samples, implying that they could become strong candidates for marine environment monitoring in Korea. The changes in organic pollutants depending on their biological trophic level were identified. To select the priority contaminants that should be managed, trophic levels in 15 species of marine organism were measured using stable isotope analysis because as the trophic levels increases, the effects of organic pollutants (e.g. PAHs, PCBs, siloxanes, and OPFRs) become biomagnified. The identified organic pollutants were classified as organic pollutants requiring priority management in the marine environment in combination with the current priority managed compounds presented in the coastal environment. NTSA was applied to various environmental samples from the Arctic to confirm detection and to suggest priority organic pollutants that could be managed in this polar environment. From the results of the NTSA, PAHs, PCBs, siloxanes, phthalates, OPFRs, synthetic musk compounds (SMCs), and hydrocarbons were proposed as priority control substances in the polar media samples. The approach and systematic framework proposed in the present study can be effectively utilized as a scientific-based decision-making procedure for prioritization to manage the emerging pollutants in the marine environment.