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| 南海西部及珠江口海水和大气单环芳烃(BTEX)的分布、来源及环境效应评估 |
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王祖甜,徐锋,王雪,王健,乔浩,吴谨巍,张洪海
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1.中国海洋大学深海圈层与地球系统前沿科学中心 海洋化学理论与工程技术教育部重点实验室
山东 青岛 266100;2.中国海洋大学化学化工学院 山东 青岛 266100;3.中国海洋大学化学化工学院 山东 青岛 266101;4.中国海洋大学化学化工学院 山东 青岛 266102;5.中国海洋大学化学化工学院 山东 青岛 266103;6.中国海洋大学化学化工学院 山东 青岛 266104;7.中国海洋大学化学化工学院 山东 青岛 266105;8.中国海洋大学化学化工学院 山东 青岛 266106
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| 摘要: |
| 以苯、甲苯、乙苯、间/对二甲苯和邻二甲苯(即BTEX)为代表的单环芳烃是挥发性有机物的主要组分，因其在二次有机气溶胶和臭氧形成过程中发挥的重要作用而备受关注。然而，由于缺乏足够的观测数据，海洋中BTEX的来源、空间分布特征及其对环境的影响有待进一步研究。为此，本研究在中国南海西部及珠江口海域开展了现场调查，揭示了该区域BTEX的空间分布特征，估算了其海–气通量，并评估了相关的环境效应。表层和底层海水中苯、甲苯、乙苯、间/对二甲苯和邻二甲苯的平均浓度(±标准偏差)分别为(12.6±6.3)、(79.5±92.8)、(10.3±9.6)、(21.6±24.1)、(13.4± 14.6) ng/L和(11.2±7.0)、(58.0±33.3)、(8.2±7.7)、(17.3±19.4)、(8.8±9.4) ng/L，表层和底层的BTEX分布趋势相似，即高值区出现在海南岛东北侧近岸和18.5°N附近海域。海水中苯与乙苯、间/对二甲苯和邻二甲苯之间存在显著的正相关关系，表明它们在海水中拥有相似的源汇过程，受到大气沉降、海上运输活动、钻井平台和洋流运动的影响。苯、甲苯、乙苯、间/对二甲苯和邻二甲苯海–气通量在8.6~43.8、71.2~849.4、4.0~78.9、1.7~189.0和1.1~112.4 g/(km2·d)之间。大气中苯、甲苯、乙苯、间/对二甲苯和邻二甲苯平均浓度分别为(0.31±0.20)、(0.33±0.22)、(0.39±0.44)、(0.47±0.44)和(0.46±0.46) μg/m3。总体而言，大气BTEX浓度从近岸到外海海域显著下降。调查海域上方大气中的BTEX主要受到大陆气团的输送影响，但表层海水的排放也有所贡献。BTEX的臭氧和二次有机气溶胶生成潜势的计算结果显示，间/对二甲苯对其生成的贡献最大，需加强管控。本研究为南海西部及珠江口海域BTEX的排放估算及其环境效应评估提供了重要的数据支持。 |
| 关键词: 单环芳烃 海–气交换 环境效应 南海西部 |
| DOI：10.19663/j.issn2095-9869.20241028003 |
| 分类号: |
| 基金项目:国家自然科学基金(41876082; 42276042)和崂山实验室科技创新项目(LSKJ202201701)共同资助 |
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| Distribution, sources, and environmental impact assessment of monocyclic aromatic hydrocarbons (BTEX) in the western South China Sea and the Pearl River Estuary |
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WANG Zutian1,2, XU Feng3,4, WANG Xue5,6, WANG Jian7,6, QIAO Hao8,6, WU Jinwei9,6, ZHANG Honghai10,6
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1.Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China;2.College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China;3.Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266101, China;4.College of Chemistry and Chemical Engineering, Ocea $ $ ;5.Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266102, China;6.College of Chemistry and Chemical Engineering, Ocea $ ;7.Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266103, China;8.Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266104, China;9.Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266105, China;10.Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266106, China
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| Abstract: |
| Monocyclic aromatic hydrocarbons (MAHs), represented by benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene (BTEX), are key components of volatile organic compounds (VOCs). These compounds play crucial roles in the formation of secondary organic aerosols and ozone. BTEX emissions from oceans contribute to localized atmospheric hydroxyl radical reactions and accelerate the formation of secondary organic aerosols. Additionally, as small lipophilic molecules, BTEX can easily penetrate living organisms, leading to unavoidable ecological risks in BTEX-contaminated environments. Due to its proximity to the economically developed Pearl River Delta (PRD) region, the western South China Sea experiences frequent economic activities, particularly fisheries and oil and gas exploration. Rapid development in the PRD region has also established the western South China Sea as a vital shipping channel. Consequently, industrial development and human activities exert pressure on the ecological environment, leading to increased water pollution and risks to fishery resources. However, limited observational data hinder the comprehensive understanding of the sources, spatial distribution, and environmental impact of BTEX in this region. To address this gap, an in-situ investigation was conducted in the western South China Sea and the Pearl River Estuary. Surface and bottom seawater samples were collected from 39 sites, and atmospheric samples were obtained from 16 sites. Temperature and salinity were measured directly during sampling using a CTD. BTEX in seawater samples was analyzed using automatic purge-trap gas chromatography-mass spectrometry (GC-MS), and sea-air fluxes were calculated using Donald Mackay's fugacity model. The ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) of BTEX were also evaluated. The average concentrations of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene in surface seawater were (12.6±6.3), (79.5±92.8), (10.3±9.6), (21.6±24.1), and (13.4±14.6) ng/L, respectively, showing similar distribution trends. In bottom seawater, these concentrations were (11.2±7.0), (58.0±33.3), (8.2±7.7), (17.3±19.4), and (8.8±9.4) ng/L, respectively. BTEX concentrations in both surface and bottom seawater were consistent with previously reported levels in the nearshore waters of Dalian and the Yangtze River estuary. Significant positive correlations were observed between benzene and ethylbenzene and between m/p-xylene and o-xylene in seawater, suggesting analogous source-sink processes. These compounds are influenced by atmospheric deposition, offshore transportation activities, drilling platforms, and ocean currents. Furthermore, regions with high BTEX concentrations coincided with areas of frequent marine transportation activities, highlighting their impact on marine pollution. The concentrations of BTEX measured in this study were below the acceptable limits established by the World Health Organization (WHO) and the U.S. Environmental Protection Agency (EPA), indicating no immediate threat to marine organisms. Sea-air fluxes of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene ranged from 8.6–43.8, 71.2–849.4, 4.0–78.9, 1.7–189.0, and 1.1–112.4 g/(km²·d), demonstrating the release of BTEX from the ocean to the atmosphere. Comparison with other coastal areas revealed lower sea-air fluxes in this region, attributed to lower sea surface wind speeds. The mean atmospheric concentrations of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene were (0.31±0.20), (0.33±0.22), (0.39±0.44), (0.47±0.44), and (0.46±0.46) μg/m3, respectively. Atmospheric BTEX concentrations decreased significantly from inshore to offshore areas, influenced predominantly by continental air masses and volatile transport emissions from surface seawater. The OFP and SOAFP calculations showed that m/p-xylene contributed the most to their formation, necessitating stricter control. Toluene was also identified as a significant contributor to ozone and secondary organic aerosol pollution, consistent with findings from inland areas. However, OFP and SOAFP values in the western South China Sea and the Pearl River Estuary were much lower than those reported in inland regions. This study provides critical data for estimating BTEX emissions and assessing their environmental effects in the western South China Sea and the Pearl River Estuary. |
| Key words: BTEX Sea-air exchange Environmental effects Western South China Sea |
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