Abstract

The daytime variation in CO₂ flux between the intertidal sediment and the atmosphere was great and impacted by environmental elements. This paper analyzed the daytime variation in CO₂ flux between the intertidal sediment and the atmosphere and concluded its different rules during the ebb tide and flood tide. During the ebb tide, the CO₂ flux rose as the tide ebbed and its rate of change was different when the redox potential changed (0.13umol m^-2 s^-1 per 100 cm height of the tide at Eh<=300mv, 0.15umol m^-2 s^-1 per 100 cm height of the tide at 300mv<Eh<500mv and  0.07umol m^-2 s^-1 per 100 cm height of the tide at Eh>=500mv). During the flood tide, the CO₂ flux maintained the largest of the day and almost unchanged with the increase of water level. The average CO₂ flux in the flood tide increased with the increase of the redox potential at Eh<=300mv and 300mv<Eh<500mv, but their linear regressions between the average CO₂ flux and the redox potential were different. Compared with the average CO₂ flux at Eh<=300mv and 300mv<Eh<500mv, the average CO₂ flux was no longer related to the redox potential but related to temperature at Eh>=500mv. According to these rules, the daytime CO₂ flux can be calculated  based on limited measurements well and truly. The fitting straight line equation between the estimated and measured CO₂ flux was y= 0.9353x+0.0872(R² = 0.75, P <0.01).

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