Effects of Tidal Scenarios on the Methane Emission Dynamics in the Subtropical Tidal Marshes of the Min River Estuary in Southeast China.

Jiafang Huang,Ji Tan,Yuxiu Liu,Yuxue Zhang,Min Luo

doi:10.3390/ijerph16152790

Abstract

In order to accurately estimate the effects of tidal scenarios on the CH4 emission from tidal wetlands, we examined the CH4 effluxes, dissolved CH4 concentrations, and environmental factors (including in situ pH, Eh and electrical conductivity, porewater SO42−, NO3−, and NH4+) during inundation and air-exposure periods in high- and low-tide seasons in the Min River Estuary in southeast China. By applying static and floating chambers, our results showed that the CH4 effluxes during the inundation periods were relatively constant and generally lower than those during the air-exposed periods in both seasons. When compared, the CH4 effluxes during the air-exposed periods were significantly higher in the high-tide season than those in the low-tide season. In contrast, CH4 effluxes during the inundation periods were significantly lower in the high-tide season than those in the low-tide season. During the inundation periods, dissolved CH4 concentrations were inversely proportional to in situ Eh. Under air-exposed conditions, CH4 effluxes were proportional to in situ pH in both seasons, while the dissolved CH4 concentrations were negatively correlated with the porewater SO42− concentrations in both seasons. Our results highlighted that CH4 effluxes were more dynamic between inundation and air-exposure periods compared to low- and high-tide seasons.

Highlights

Methane (CH4 ) is the second-most important radiatively active greenhouse gas and has a global warming potential 28 times greater than that of carbon dioxide (CO2 ) over a 100-year time span [1].Despite a relatively small surface area, the volume of coastal CH4 effluxes was estimated to be quantitatively comparable to the CH4 uptake by the continental shelf [2]
Our results showed that both tide inundation and seasonality showed a significant influence on CH4 effluxes and dissolved CH4 concentrations, and that tide inundation had a more pronounced impact on CH4 dynamics compared with seasonal change (Figure 5)
We examined the CH4 dynamics under inundation and air-exposed periods across the high- and low-tide seasons

Summary

Introduction

Methane (CH4 ) is the second-most important radiatively active greenhouse gas and has a global warming potential 28 times greater than that of carbon dioxide (CO2 ) over a 100-year time span [1].Despite a relatively small surface area, the volume of coastal CH4 effluxes was estimated to be quantitatively comparable to the CH4 uptake by the continental shelf [2]. Methane (CH4 ) is the second-most important radiatively active greenhouse gas and has a global warming potential 28 times greater than that of carbon dioxide (CO2 ) over a 100-year time span [1]. Even though the quantification of CH4 effluxes from estuarine tidal wetlands is crucial when evaluating the global greenhouse budget, the data available for this purpose is extremely limited as estuarine tidal wetlands are periodically affected by fluctuating tidal hydrologic regimes [5]. The action of tides has a significant effect on CH4 effluxes through various physical, geochemical, and biological factors. The tides influence various biological processes that have the potential to modify carbon cycling, such as microbial and plant respiration, photosynthesis, and carbon uptake [11,12]

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