Abstract Marine isoprene concentrations in the East China Sea were measured during two oceanographic cruises: one from October 10, 2013 to November 21, 2013 and another from May 16, 2014 to June 13, 2014. Mean (range) isoprene concentrations in the surface water in the study area were 32.85 (16.31–108.2) pmol L−1 in late spring and 26.83 (11.22–42.13) pmol L−1 in autumn. The isoprene concentrations showed seasonal variation and were higher in late spring, which could be attributable to terrigenous diluted water and seasonal variations of phytoplankton structure. Isoprene and chlorophyll a (Chl-a) concentrations were significantly correlated in late spring and autumn even under complex hydrographic conditions. Isoprene and Chl-a concentrations also exhibited similar variations during a 25 h period and remained high during daytime. Analysis of depth profiles indicated that isoprene concentrations in the water column peaked at the surface layer and gradually decreased with increasing depth. The atmospheric concentration of isoprene (average: 53.4 ppt; range: 14.8–141 ppt) was high in the onshore area but low in the offshore area in late spring. The mean sea-to-air fluxes of isoprene in the East China Sea were 36.12 (late spring) and 48.34 (autumn) nmol m−2 d−1. Results revealed the substantial isoprene emission from surface seawater, which was also a net source of atmospheric isoprene during the study period.

中文翻译：

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东海海洋异戊二烯分布及海气通量的时间变化

摘要 东海海洋异戊二烯浓度在两次海洋航行期间测量：一次是从 2013 年 10 月 10 日至 2013 年 11 月 21 日，另一次是从 2014 年 5 月 16 日至 2014 年 6 月 13 日。研究区春末为32.85（16.31-108.2）pmol L-1，秋季为26.83（11.22-42.13）pmol L-1。异戊二烯浓度呈现季节性变化，晚春较高，这可能与陆源稀释水和浮游植物结构季节性变化有关。即使在复杂的水文条件下，异戊二烯和叶绿素 a (Chl-a) 浓度在晚春和秋季也显着相关。异戊二烯和 Chl-a 浓度在 25 小时内也表现出类似的变化，并在白天保持高水平。深度剖面分析表明，水体中的异戊二烯浓度在表层达到峰值，并随着深度的增加而逐渐降低。晚春，大气中异戊二烯浓度（平均：53.4 ppt；范围：14.8-141 ppt）在陆上地区高，而在海上地区低。东海异戊二烯的平均海气通量分别为 36.12（晚春）和 48.34（秋季）nmol m-2 d-1。结果表明，表层海水中大量异戊二烯排放，这也是研究期间大气异戊二烯的净来源。8-141 ppt) 在晚春在陆上地区较高，而在海上地区较低。东海异戊二烯的平均海气通量分别为 36.12（晚春）和 48.34（秋季）nmol m-2 d-1。结果表明，表层海水中大量异戊二烯排放，这也是研究期间大气异戊二烯的净来源。8-141 ppt) 在晚春在陆上地区较高，而在海上地区较低。东海异戊二烯的平均海气通量分别为 36.12（晚春）和 48.34（秋季）nmol m-2 d-1。结果表明，表层海水中大量异戊二烯排放，这也是研究期间大气异戊二烯的净来源。