Distribution and pollution history of cyclic and liner siloxanes in sediments from Ulsan and Onsan Bays, Korea

Abstract

Cyclic and linear siloxanes have been widely used in personal care products and industrial products because of their low surface tension, high thermal stability, smooth texture, and chemical inert. Owing to their ubiquitous occurrence, environmental persistence, bioaccumulation, and toxic potentials, siloxanes are of great concerns for environmental chemistry and toxicology. Because of knowledge gap in analytical methods on siloxanes in various environmental matrices and difficulty to control background contamination during experimental procedure, it is necessary to establish optimized analytical methods and quality assurance and quality control (QA/QC) protocols for siloxane determination in sediment samples. Ulsan and Onsan Bays, which are the most industrialized coastal regions in Korea, have a long pollution history on toxic organic and inorganic pollutants such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (DL-PCBs), polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs), and heavy metals. In this study, the optimized analytical methods of cyclic and linear siloxanes were suggested among 4 different methods based on mass spectrometry (MS). The optimized methods were applied for 42 surface sediment samples for Ulsan and Onsan Bays, to investigate the distribution and source identification of siloxanes, one dated core sediment sample was used for grasping pollution history of siloxanes in coastal environment of Ulsan Bay. Through comparison of four different analytical methods for siloxane determination in sediment, gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) without any purification procedure was chosen for the optimized method. Siloxanes were detected in all of the sediment samples, indicating widespread contamination in coastal environment. The highest concentrations of siloxanes were found in sediments from Gosa Stream, surrounded by oil, chemical fertilizer, and petrochemical complexes. The mean concentration of siloxanes in sediments from Gosa Stream was comparable or much higher than those found in previous studies. Mean concentrations of cyclic siloxanes in sediments from Taehwa River, Ulsan Bay, Onsan Bay, Woiwhang River were similar or lower than those reported for previous studies. The concentrations of cyclic siloxanes in surface sediments from Ulsan and Onsan Bays were higher than those of linear siloxanes, suggesting the high consumption of cyclic siloxanes. However, the locations with the highest levels of siloxanes (Gosa Stream) showed the higher contribution of linear than cyclic siloxanes (p < 0.01), implying the existence of specific source of linear siloxanes. Cyclic siloxanes were significantly positively correlated with linear siloxanes, suggesting similar sources and environmental behavior in aquatic environment. D5, D6, D7, and higher molecular linear siloxanes were significantly positively correlated with TOC, suggesting stronger tendency with organic matter. Pollution history of siloxanes showed the increasing levels of siloxanes with time since early 1970s. These results are well matched with history of siloxane production and industrialization of Ulsan and Onsan complexes. Considering widespread presence and bioaccumulation potentials of siloxanes, systematic monitoring program of siloxanes should be instituted to protect the sustainable health of marine organisms from Korean coastal waters.|고리형과 선형 실록산은 낮은 표면장력, 높은 열 안정성, 부드러운 촉감, 그리고 화학적 불활성의 성질로 인해 개인기호품이나 산업제품으로 많이 사용된다. 실록산의 넓은 존재, 환경 잔류성, 생물농축성, 그리고 잠재적 독성으로 인해, 실록산은 환경화학과 독성학적으로 많은 관심을 보이고 있다. 그러나 실록산 분석에 대한 정보가 부족하고 분석과정 중 오염을 통제가는 것이 어렵기 때문에, 퇴적물 내 실록산 분석을 위한 분석방법과 정도관리기법을 확립하는 것이 필요하다. 울산만과 온산만은 우리나라 도시 중 가장 산업화가 많이 진전된 지역이며, 다이옥신/퓨란류 (PCDD/Fs), 다환방향족탄화수소 (PAHs), 폴리브롬화 디페닐에테르류 (PBDEs), 그리고 중금속과 같은 오염물질에 대한 많은 연구들이 진행되어왔다. 본 연구에서는 질량분석기를 기반으로 한 4가지 다른 분석방법 중에 고리형과 선형 실록산의 분석법을 확립하였다. 확립된 분석방법은 울산만과 온산만 지역에서 42개의 표층 퇴적물에 적용하여, 실록산의 분포와 오염원 추적에 관한 조사를 하였고, 한 개의 주상퇴적물 시료는 울산만 연안에 실록산의 오염역사를 파악하는데 사용되었다. 4가지의 퇴적물 내 실록산 분석 방법 비교를 통해, 정제과정을 거치지 않고 기체크로마토그래프-삼중질량분석기 (GC-MS/MS)가 가장 적합한 분석방법이었다. 실록산은 모든 표층퇴적물에서 검출되었다. 이것은 한국 연안에 실록산의 광범위한 오염을 시사한다. 가장 높은 실록산 농도를 보인 지역은 고사천으로, 대규모 정유, 비료, 화학, 석유화학 등의 공업이 집중해있다. 고사천 지역은 다른 나라와 비교하였을 때 비슷하거나 높은 농도를 보였다. 태화강, 울산만, 온산만, 외황강 내 고리형 실록산의 평균 농도는 이전 연구와 비교해 보았을 때, 비슷하거나 낮은 수준이다. 고리형 실록산이 선형 실록산보다 울산만과 온산만 지역에 높은 조성비를 나타내었는데, 이것은 고리형 실록산의 높은 소비량을 시사한다. 그러나, 고사천 내측에는 선형 실록산이 더 높은 조성비를 보였는데, 이는 고사천 근처에 선형 실록산의 특정한 오염원이 존재함을 의미한다. 고리형 실록산과 선형 실록산은 높은 상관관계를 보였다. 이는 비슷한 오염원 그리고 수중 생태계 내 환경적 거동을 시사한다. D5, D6, D7 그리고 고분자량의 선형 실록산은 TOC와 높은 상관관계를 보였는데, 이는 유기물에 강하게 흡착하려는 성질을 보이는 것을 의미한다. 울산만 내 실록산은 1970년대부터 현재까지 농도가 증가하는 추세를 보였는데, 이것은 세계적인 생산량이 지속적으로 증가한 시점과 울산만이 산업화가 급격하게 증가된 시점과 일치한 결과였다. 실록산의 지속적인 광범위한 존재, 생물농축성의 잠재성을 고려하였을 때, 실록산의 지속적인 모니터링 연구는 한국연안 내 해양생물을 보호할 것이다.; Cyclic and linear siloxanes have been widely used in personal care products and industrial products because of their low surface tension, high thermal stability, smooth texture, and chemical inert. Owing to their ubiquitous occurrence, environmental persistence, bioaccumulation, and toxic potentials, siloxanes are of great concerns for environmental chemistry and toxicology. Because of knowledge gap in analytical methods on siloxanes in various environmental matrices and difficulty to control background contamination during experimental procedure, it is necessary to establish optimized analytical methods and quality assurance and quality control (QA/QC) protocols for siloxane determination in sediment samples. Ulsan and Onsan Bays, which are the most industrialized coastal regions in Korea, have a long pollution history on toxic organic and inorganic pollutants such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (DL-PCBs), polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs), and heavy metals. In this study, the optimized analytical methods of cyclic and linear siloxanes were suggested among 4 different methods based on mass spectrometry (MS). The optimized methods were applied for 42 surface sediment samples for Ulsan and Onsan Bays, to investigate the distribution and source identification of siloxanes, one dated core sediment sample was used for grasping pollution history of siloxanes in coastal environment of Ulsan Bay. Through comparison of four different analytical methods for siloxane determination in sediment, gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) without any purification procedure was chosen for the optimized method. Siloxanes were detected in all of the sediment samples, indicating widespread contamination in coastal environment. The highest concentrations of siloxanes were found in sediments from Gosa Stream, surrounded by oil, chemical fertilizer, and petrochemical complexes. The mean concentration of siloxanes in sediments from Gosa Stream was comparable or much higher than those found in previous studies. Mean concentrations of cyclic siloxanes in sediments from Taehwa River, Ulsan Bay, Onsan Bay, Woiwhang River were similar or lower than those reported for previous studies. The concentrations of cyclic siloxanes in surface sediments from Ulsan and Onsan Bays were higher than those of linear siloxanes, suggesting the high consumption of cyclic siloxanes. However, the locations with the highest levels of siloxanes (Gosa Stream) showed the higher contribution of linear than cyclic siloxanes (p < 0.01), implying the existence of specific source of linear siloxanes. Cyclic siloxanes were significantly positively correlated with linear siloxanes, suggesting similar sources and environmental behavior in aquatic environment. D5, D6, D7, and higher molecular linear siloxanes were significantly positively correlated with TOC, suggesting stronger tendency with organic matter. Pollution history of siloxanes showed the increasing levels of siloxanes with time since early 1970s. These results are well matched with history of siloxane production and industrialization of Ulsan and Onsan complexes. Considering widespread presence and bioaccumulation potentials of siloxanes, systematic monitoring program of siloxanes should be instituted to protect the sustainable health of marine organisms from Korean coastal waters.