离子迁移谱现场观测渤海和北黄海二甲基硫的研究

渤海、黄海是高产二甲基硫（Dimethyl Sulfide, DMS）的大陆架海区。该海区DMS的现场调查研究有助于准确评估海洋DMS释放量及其对全球气候变化的负反馈作用。目前，无论是基于模型还是直接测量法的通量估算均以表层海水或低层大气DMS浓度为基础，因此，先进的检测技术对其通量估算的准确度具有决定性作用。气相色谱法、质谱法、化学发光法以及卫星遥感技术是现在常用的观测技术，而本文则基于苯辅助光电离离子迁移谱技术进一步提出了一种可在海域现场观测海水中DMS的方法。通过结合动态气提-Nafion管在线除水进样系统，消除环境水汽的干扰；在最优条件下，基于DMS两个产物离子峰，可以实现0.10～120 nmol/L之间DMS的定量分析，检测限低至0.065 nmol/L；然后将所建方法应用于2019年秋季渤海、北黄海海水中DMS的现场观测。结果表明，表层海水中DMS的浓度为0.080～0.96 nmol/L（平均值为（0.44±0.34）nmol/L），其海气通量为0.12～17.75 μmol/（m²·d）（平均值为（ 3.23±4.02）μmol/（m²·d））；通过结合实验室检测结果、环境因子和浮游植物群落结构讨论了海水样品低温储存条件下DMS的变化和影响因素，结果显示，营养盐成分及浮游植物群落结构是影响储存样品中DMS浓度显著增加的主要因素，进一步表明了现场观测方法的建立对海洋DMS释放量的准确评估具有重要意义。

Field investigation of dimethyl sulfur in the Bohai Sea and northern Yellow Sea by ion mobility spectrometry

The Bohai Sea and Yellow Sea are continental shelf areas with high production of dimethyl sulfide (DMS). Field investigation of DMS in this area is helpful to accurately assess its amount released from the ocean and its negative feedback on global climate change. Both model-based and direct measurement methods are based on DMS concentration in surface seawater and lower atmosphere, respectively, so advanced detection technology plays a decisive role in the accurate flux estimation. Gas chromatography, mass spectrometry, chemiluminescence and satellite remote sensing are commonly used observation techniques. At this paper, a method based on benzene-assisted photoionization positive ion mobility spectrometry (BAPI-PIMS) for in-situ observation of DMS in seawater is proposed. Combined with dynamic gas stripping and on-line water removal Nafion tube sampling system, the interference of environmental water vapor is eliminated. Under the optimal conditions, the linear range based on the two DMS product ions is 0.10−120 nmol/L, and the detection limit is as low as 0.065 nmol/L. Then the demonstrated method is applied to field detect DMS in the Bohai Sea and northern Yellow Sea, and the concentration of DMS in surface seawater ranged from 0.08 nmol/L to 0.96 nmol/L, while the air-sea exchange flux ranged from 0.12 μmol/(m2·d) to 17.75 μmol/(m2·d). Lastly, the difference between DMS detected on field and in lab and the main impact factors are discussed via the correlation analysis and canonical correspondence analysis, and results show that nutrients and phytoplankton community are the main factors during the seawater preservation, indicating the important significance of field observation method established currently for accurate evaluation of DMS release from the ocean.