Comparative evaluation of high-resolution seawater CO<sub>2</sub> partial pressure measurement methods and their application in coastal monitoring networks

Li Xuanxuan; Li Qian; Wang Bin; Zhang Xuan; Bai Yan; Zhang Yixing; Hu Xupeng; Chen Jiangfang

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Li Xuanxuan，Li Qian，Wang Bin, et al. Comparative evaluation of high-resolution seawater CO2 partial pressure measurement methods and their application in coastal monitoring networks[J]. Haiyang Xuebao，2026, 48(x)：1–12

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Li Xuanxuan，Li Qian，Wang Bin, et al. Comparative evaluation of high-resolution seawater CO₂ partial pressure measurement methods and their application in coastal monitoring networks[J]. Haiyang Xuebao，2026, 48(x)：1–12

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Comparative evaluation of high-resolution seawater CO₂ partial pressure measurement methods and their application in coastal monitoring networks

Li Xuanxuan^{1, 2
,},
Li Qian^{2
,
,},
Wang Bin²,
Zhang Xuan³,
Bai Yan³,
Zhang Yixing²,
Hu Xupeng⁴,
Chen Jiangfang^{2, 3
,
,}

1.
Ocean College, Zhejiang University, Zhoushan 316021, China
2.
Key Laboratory of Marine Ecosystem Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China
3.
State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China
4.
Zhejiang Marine Ecological and Environmental Monitoring Center, Zhoushan 316021, China

Received Date: 2025-12-21
Rev Recd Date: 2026-02-24

Available Online: 2026-04-05

Abstract

Abstract

High-stability monitoring of air-sea CO₂ partial pressure (pCO₂) is fundamental for assessing air-sea CO₂ fluxes across long temporal and broad spatial scales. Among the commonly used methods worldwide, the air-water equilibration technique and the membrane-based diffusion technique are widely applied for measuring pCO₂. In this study, we conducted underway continuous observations in Yueqing Bay and a 50-hour fixed-point deployment near Bianmanyu Island using the LI-5405A (air-water equilibration method) and the CONTROS HydroC® CO₂ sensor (membrane equilibration method). The performance characteristics and application scenarios of the two approaches were systematically compared. The average difference between the two methods was 0.76 ± 4.46 μatm during the entire observation period, but both approaches produced consistent temporal trends with strong correlation. These two approaches exhibited distinct advantages: the membrane equilibrium method features low power consumption and an integrated watertight design, making it suitable for long-term continuous monitoring in in-situ scenarios or where power supply and space are limited. The air-water equilibration method, featuring rapid response and high precision, is more applicable for high-resolution measurements in dynamic environments. We propose a synergistic observational framework combining baseline monitoring using the membrane equilibration technique with periodic calibration via the air-water equilibration method. This integrated approach enhances both temporal and spatial resolution of air-sea CO₂ flux observations, thereby improving data reliability and providing robust technical support for nearshore carbon source-sink assessments.
- CO₂ partial pressure,
- air-water equilibration method,
- membrane equilibration method,
- synergistic observation

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References(48)

References

[1]	Friedlingstein P, O'Sullivan M, Jones M W, et al. Global carbon budget 2022[J]. Earth System Science Data, 2022, 14(11): 4811−4900. doi: 10.5194/essd-14-4811-2022
[2]	中华人民共和国自然资源部. HY/T 0343.4-2022, 海-气二氧化碳交换通量监测与评估技术规程第4部分: 基于分压差的通量评估[S]. 北京: 中国标准出版社, 2022. Ministry of Natural Resources, People's Republic of China. HY/T 0343.4-2022, Protocol of air-sea CO₂ flux monitoring and assessment-Part 4: flux estimation based on pCO₂ difference[S]. Beijing: Standards Press of China, 2022.
[3]	Wanninkhof R, Asher W E, Ho D T, et al. Advances in quantifying air-sea gas exchange and environmental forcing[J]. Annual Review of Marine Science, 2009, 1: 213−244. doi: 10.1146/annurev.marine.010908.163742
[4]	苗燕熠, 王斌, 李德望, 等. 大风事件对长江口及邻近海域海-气CO₂通量的影响[J]. 海洋学研究, 2020, 38(1): 42−49. Miao Yanyi, Wang Bin, Li Dewang, et al. The effect of strong wind on air-sea CO₂ flux in the Changjiang River Estuary and its adjacent sea areas[J]. Journal of Marine Sciences, 2020, 38(1): 42−49.
[5]	卢汐, 宋金明, 袁华茂, 等. 黑潮与毗邻陆架海域的碳交换[J]. 地球科学进展, 2015, 30(2): 214−225. Lu Xi, Song Jinming, Yuan Huamao, et al. Carbon distribution and exchange of Kuroshio and adjacent China sea shelf: a review[J]. Advances in Earth Science, 2015, 30(2): 214−225.
[6]	Guo X H, Zhai W D, Dai Minhan, et al. Air-sea CO₂ fluxes in the East China Sea based on multiple-year underway observations[J]. Biogeosciences, 2015, 12(18): 5495−5514. doi: 10.5194/bg-12-5495-2015
[7]	Zhai Weidong, Dai Minhan. On the seasonal variation of air-sea CO₂ fluxes in the outer Changjiang (Yangtze River) Estuary, East China Sea[J]. Marine Chemistry, 2009, 117(1/4): 2−10. doi: 10.1016/j.marchem.2009.02.008
[8]	Dickson A G, Sabine C L, Christian J R. Guide to best practices for ocean CO₂ measurements[R]. PICES Special Publication, 2007. (查阅网上资料, 未找到对应的出版地信息, 请确认)
[9]	中华人民共和国自然资源部. HY/T 0343.7-2022, 海-气二氧化碳交换通量监测与评估技术规程第7部分: 现场监测二氧化碳分压数据处理[S]. 北京: 中国标准出版社, 2022. Ministry of Natural Resources, People's Republic of China. HY/T 0343.7-2022, Protocol of air-sea CO₂ flux monitoring and assessment-Part 7: date processing of field-measured partial pressure of CO₂[S]. Beijing: Standards Press of China, 2022.
[10]	Arruda R, Atamanchuk D, Cronin M, et al. At-sea intercomparison of three underway pCO₂ systems[J]. Limnology and Oceanography: Methods, 2020, 18(2): 63−76.
[11]	Fiedler B, Fietzek P, Vieira N, et al. In situ CO₂ and O₂ measurements on a profiling float[J]. Journal of Atmospheric and Oceanic Technology, 2013, 30(1): 112−126. doi: 10.1175/JTECH-D-12-00043.1
[12]	Jiang Zongpei, Hydes D J, Hartman S E, et al. Application and assessment of a membrane-based pCO₂ sensor under field and laboratory conditions[J]. Limnology and Oceanography: Methods, 2014, 12(4): 264−280. doi: 10.4319/lom.2014.12.264
[13]	Mo A, Park K, Kim T W, et al. pCO₂ variation in ice-covered regions of the Arctic Ocean from the summer 2022 observation[J]. Limnology and Oceanography Letters, 2024, 9(5): 573−582. doi: 10.1002/lol2.10415
[14]	Macovei V A, Voynova Y G, Becker M, et al. Long-term intercomparison of two pCO₂ instruments based on ship-of-opportunity measurements in a dynamic shelf sea environment[J]. Limnology and Oceanography: Methods, 2021, 19(1): 37−50.
[15]	许苏清, 李伟, 王伟强, 等. 两种海洋二氧化碳现场监测技术比对研究[J]. 海洋技术, 2013, 32(3): 11−14. Xu Suqing, Li Wei, Wang Weiqiang, et al. Comparison study on two systems measuring the in-situ marine pCO₂[J]. Ocean Technology, 2013, 32(3): 11−14.
[16]	Jiang Liqing, Cai Weijun, Wanninkhof R, et al. Air-sea CO₂ fluxes on the U. S. South Atlantic Bight: spatial and seasonal variability[J]. Journal of Geophysical Research: Oceans, 2008, 113(C7): C07019.
[17]	Wanninkhof R, Doney S C, Takahashi T, et al. The effect of using time-averaged winds on regional air-sea CO₂ fluxes[M]//Donelan M A, Drennan W M, Saltzman E S, et al. Gas Transfer at Water Surfaces. Washington: American Geophysical Union, 2002: 351-356.
[18]	Li Qian, Guo Xianghui, Zhai Weidong, et al. Partial pressure of CO₂ and air-sea CO₂ fluxes in the South China Sea: synthesis of an 18-year dataset[J]. Progress in Oceanography, 2020, 182: 102272. doi: 10.1016/j.pocean.2020.102272
[19]	李权龙, 刘文静, 江坤善, 等. 海水二氧化碳分压测量用水-气平衡器[J]. 应用海洋学学报, 2022, 41(2): 185−192. Li Quanlong, Liu Wenjing, Jiang Kunshan, et al. Air-water equilibrators for measurement of partial pressure of CO₂ in seawater[J]. Journal of Applied Oceanography, 2022, 41(2): 185−192.
[20]	Huang W J, Cai Weijun, Wang Yongchen, et al. The carbon dioxide system on the mississippi river-dominated continental shelf in the northern gulf of Mexico: 1. distribution and air-sea CO₂ flux[J]. Journal of Geophysical Research: Oceans, 2015, 120(3): 1429−1445.
[21]	Chen Baoshan, Cai Weijun, Brodeur J R, et al. Seasonal and spatial variability in surface pCO₂ and air-water CO₂ flux in the Chesapeake Bay[J]. Limnology and Oceanography, 2020, 65(12): 3046−3065.
[22]	李德望, 林华, 陈思杨, 等. 2017年春季长江口-东海连续体pCO₂的空间分布特征及其控制因素[J]. 海洋学研究, 2021, 39(4): 52−62. Li Dewang, Lin Hua, Chen Siyang, et al. Distributions and controlling factors of pCO2 in the Changjiang (Yangtze River) Estuary-East China Sea continuum in spring of 2017[J]. Journal of Marine Sciences, 2021, 39(4): 52−62.
[23]	Fietzek P, Fiedler B, Steinhoff T, et al. In situ quality assessment of a novel underwater pCO₂ sensor based on membrane equilibration and NDIR spectrometry[J]. Journal of Atmospheric and Oceanic Technology, 2014, 31(1): 181−196. doi: 10.1175/JTECH-D-13-00083.1
[24]	Merkel T C, Bondar V I, Nagai K, et al. Gas sorption, diffusion, and permeation in poly (dimethylsiloxane)[J]. Journal of Polymer Science Part B: Polymer Physics, 2000, 38(3): 415−434.
[25]	Saderne V, Fietzek P, Herman P M J. Extreme variations of pCO₂ and pH in a macrophyte meadow of the Baltic Sea in summer: evidence of the effect of photosynthesis and local upwelling[J]. PLoS One, 2013, 8(4): e62689. doi: 10.1371/journal.pone.0062689
[26]	Yakushev E, Blomberg A E A, Eek E, et al. Modeling of biogeochemical consequences of a CO₂ leak in the water column with bottom anoxia[J]. International Journal of Greenhouse Gas Control, 2021, 111: 103464. doi: 10.1016/j.ijggc.2021.103464
[27]	Baumann H, Wallace R B, Tagliaferri T, et al. Large natural pH, CO₂ and O₂ fluctuations in a temperate tidal salt marsh on diel, seasonal, and interannual time scales[J]. Estuaries and Coasts, 2015, 38(1): 220−231. doi: 10.1007/s12237-014-9800-y
[28]	Mo A, Park K, Kim T W, et al. pCO₂ variation in ice-covered regions of the Arctic Ocean from the summer 2022 observation[J]. Limnology and Oceanography Letters, 2024, 9(5): 573−582. (查阅网上资料, 本条文献与第13条文献重复, 请确认)
[29]	Mo A, Park K, Park J, et al. Assessment of austral autumn air-sea CO₂ exchange in the Pacific sector of the Southern Ocean and dominant controlling factors[J]. Frontiers in Marine Science, 2023, 10: 1192959, doi: 10.3389/fmars.2023.1192959
[30]	Macovei V A, Petersen W, Brix H, et al. Reduced ocean carbon sink in the south and central North Sea (2014-2018) revealed from FerryBox observations[J]. Geophysical Research Letters, 2021, 48(11): e2021GL092645, doi: 10.1029/2021GL092645
[31]	中国海湾志编纂委员会. 中国海湾志-第六分册-浙江省南部海湾[M]. 北京: 海洋出版社, 1993: 110−118. Compilation Committee of China’s Gulf Records. China’s Gulf Records (Fascicle 6: Southern Bays of Zhejiang Province)[M]. Beijing: China Ocean Press, 1993: 110−118. (查阅网上资料, 未找到对应的英文翻译, 请确认)
[32]	冯礼奎, 朱新强, 王宏义. 潮汐影响海水沉淀池运行的原因分析与对策[J]. 工业水处理, 2009, 29(6): 76−79. Feng Likui, Zhu Xinqiang, Wang Hongyi. Cause analysis and countermeasure research on the effect of sea water tide on sea water sedimentation tanks[J]. Industrial Water Treatment, 2009, 29(6): 76−79.
[33]	Zhang Yixing, Wang Bin, Li Qian, et al. CO₂ dynamics and sequestration potential in high-nutrient, low-chlorophyll bays: a case study of Yueqing Bay[J]. Marine Environmental Research, 2025, 207: 107061. doi: 10.1016/j.marenvres.2025.107061
[34]	胡序朋, 李芯芯, 徐成达, 等. 浙江近岸海域悬浮颗粒物中磷的赋存形态及分布特征研究[J]. 海洋学报, 2021, 43(4): 106−121. Hu Xupeng, Li Xinxin, Xu Chengda, et al. Characteristics of phosphorus speciation and distribution in suspended particulate matter in the Zhejiang coastal area[J]. Haiyang Xuebao, 2021, 43(4): 106−121.
[35]	吴奋武, 李熹. 浙江省温州市滩涂贝苗增养殖情况介绍[J]. 福建水产, 1992(1): 77−79. Wu Fenwu, Li Xi. Introduction to the breeding and stock enhancement of shellfish seeds in tidal flats of Wenzhou City, Zhejiang Province[J]. Fujian Fisheries, 1992(1): 77−79. (查阅网上资料, 未找到对应的英文翻译, 请确认)
[36]	刘镇盛, 王春生, 张志南, 等. 乐清湾浮游动物的季节变动及摄食率[J]. 生态学报, 2005, 25(8): 1853−1862. Liu Zhensheng, Wang Chunsheng, Zhang Zhinan, et al. Seasonal dynamics and grazing rate of zooplankton in Yeqing Bay[J]. Acta Ecologica Sinica, 2005, 25(8): 1853−1862.
[37]	彭欣, 仇建标, 陈少波, 等. 乐清湾生态系统脆弱性研究[J]. 海洋学研究, 2009, 27(3): 111−118. Peng Xin, Qiu Jianbiao, Chen Shaobo, et al. The study on the vulnerability of the ecosystem in Yueqingwan Bay[J]. Journal of Marine Sciences, 2009, 27(3): 111−118.
[38]	Dickson A G, Goyet C. Handbook of methods for the analysis of the various parameters of the carbon dioxide system in sea water. Version 2[R]. Oak Ridge: Oak Ridge National Lab. , 1994. (查阅网上资料, 未找到对应的出版信息, 请确认)
[39]	Weiss R F, Price B A. Nitrous oxide solubility in water and seawater[J]. Marine Chemistry, 1980, 8(4): 347−359. doi: 10.1016/0304-4203(80)90024-9
[40]	Takahashi T, Olafsson J, Goddard J G, et al. Seasonal variation of CO₂ and nutrients in the high-latitude surface oceans: a comparative study[J]. Global Biogeochemical Cycles, 1993, 7(4): 843−878. doi: 10.1029/93GB02263
[41]	Webb J R, Maher D T, Santos I R. Automated, in situ measurements of dissolved CO₂, CH₄, and δ¹³C values using cavity enhanced laser absorption spectrometry: comparing response times of air-water equilibrators[J]. Limnology and Oceanography: Methods, 2016, 14(5): 323−337. doi: 10.1002/lom3.10092
[42]	Liu Qian, Dong Xu, Chen Jinshun, et al. Diurnal to interannual variability of sea surface pCO₂ and its controls in a turbid tidal-driven nearshore system in the vicinity of the East China Sea based on buoy observations[J]. Marine Chemistry, 2019, 216: 103690. doi: 10.1016/j.marchem.2019.103690
[43]	Merkel T C, Bondar V I, Nagai K, et al. Gas sorption, diffusion, and permeation in poly (dimethylsiloxane)[J]. Journal of Polymer Science Part B: Polymer Physics, 2000, 38(3): 415−434. (查阅网上资料, 本条文献与第24条文献重复, 请确认)
[44]	Serpone N. Aquatic chemistry: chemical equilibria and rates in natural waters[J]. Journal of Chemical Education, 1996, 73(11): A277. (查阅网上资料, 未找到本条文献信息, 请确认)
[45]	Cussler E L. Diffusion: Mass Transfer in Fluid Systems[M]. 3rd ed. Cambridge: Cambridge University Press, 2009.
[46]	Berean K, Ou Jianzhen, Nour M, et al. The effect of crosslinking temperature on the permeability of PDMS membranes: evidence of extraordinary CO₂ and CH₄ gas permeation[J]. Separation and Purification Technology, 2014, 122: 96−104. doi: 10.1016/j.seppur.2013.11.006
[47]	Ataeivarjovi E, Tang Zhigang, Chen Jian. Study on CO₂ desorption behavior of a PDMS-SiO₂ hybrid membrane applied in a novel CO₂ capture process[J]. ACS Applied Materials & Interfaces, 2018, 10(34): 28992−29002, doi: 10.1021/acsami.8b08630
[48]	Sun Youwen, Liu Wenqing, Zeng Yi, et al. Water vapor interference correction in a non dispersive infrared multi-gas analyzer[J]. Chinese Physics Letters, 2011, 28(7): 073302. doi: 10.1088/0256-307X/28/7/073302