Qing-Hua He

Bio: Qing-Hua He is an academic researcher from Fujian Normal University. The author has contributed to research in topics: Aquaculture & China. The author has an hindex of 2, co-authored 3 publications receiving 51 citations.

[Diurnal variations of greenhouse gas fluxes at the water-air interface of aquaculture ponds in the Min River estuary].

Abstract: Wetland reclamation and aquaculture is one of the main disturbance types in coastal wetlands. Diurnal variations of CO2, CH4 and N2O fluxes at the water-air interface were determined using a floating chambers + gas chromatography method in a shrimp pond, and a mixed culture pond of fish and shrimp in October in the Shanyutan Wetland of the Min River estuary, southeast China. Meanwhile, the meteorological indicators in ground surface and physical, chemical and biological indicators of surface water were also measured. CO2, CH4 and N2O fluxes at the water-air interface all demonstrated distinct diurnal variations. Both shrimp pond and mixed culture pond of fish and shrimp functioned as a sink of CO2 [the diurnal averaged CO2 fluxes were -48.79 and -105.25 mg x (m2 x h)(-1), respectively], and a source of CH4 [the diurnal averaged CH4 fluxes were 1.00 and 5.74 mg x (m2 x h)(-1), respectively]; the diurnal averaged CO2 and CH4 fluxes at the water-air interface of the mixed culture of fish and shrimp pond were higher than that of the shrimp pond. Greenhouse gas fluxes at the water-air interface from the aquaculture ponds were influenced by many factors. Multiple stepwise regression analysis showed that the concentration of Chlorophyll was the major factor affecting the CO2 fluxes, and the concentrations of SO4(2-) and PO4(3-) were the major factors affecting the CH4 fluxes at the water-air interface of the shrimp pond; whereas water temperature and Chlorophyll were the major factors affecting the CO2 fluxes, and dissolved oxygen, PO4(3-) and pH were the major factors affecting the CH4 fluxes at the water-air interface of the mixed culture pond of fish and shrimp.

Diurnal Variations of CH4 and N2O Fluxes from the Drained Aquaculture Pond in the Minjiang River Estuary During Early Winter

Abstract: Annual drainage is a typical management activity practiced by operators as a way to export aquaculture effluent, accelerate aerobic decomposition of bottom soils, and avoid eutrophication during the non-culture period after harvest. Drainage activities can cause large changes in hydrology, nutrient cycling, sediment physicochemical properties, and even broad ecosystem functions. In order to understand the effects of drainage on the diurnal variation characteristics and magnitude of greenhouse gas (CH4 and N2O) fluxes from the aquaculture ponds of the estuaries, a 24-hour continuous monitoring was conducted from one undrained pond (UDP) and one drained pond (DP) during early winter in the Minjiang River estuary on the southeast coast of China. Over the entire study period, the fluxes of CH4 from the UDP and DP ranged from 0.04 to 0.10 mg·(m2·h)-1 and 14.04 to 33.72 mg·(m2·h)-1, respectively, with means of (0.07±0.01) mg·(m2·h)-1 and (24.74±2.33) mg·(m2·h)-1. The CH4 flux was lower during the day and higher at night with a net flux as the sources of the CH4. The fluxes of N2O from the UDP ranged from -0.027 to 0.011 mg·(m2·h)-1, and the average fluxes of (0.002±0.004) mg·(m2·h)-1 showed "weak absorption by day and emission at night." The N2O fluxes from the DP were emitted all day (ranging from 0.59 to 1.76 mg·(m2·h)-1) with the average fluxes of N2O (1.07±0.15) mg·(m2·h)-1 indicating higher fluxes at night and lower fluxes during the day. Our research demonstrated that drainage would significantly enhance CH4 and N2O release from the aquaculture ponds. The study also preliminarily confirms that the undrained pond converted to a drained pond considerably alter the diurnal variation characteristics of the CH4 and N2O emissions during early winter. Clearly, future measurements in situ at high frequency over a long time and at different spatial scales would be worth researching from drained aquaculture ponds.

Conversion of coastal wetlands, riparian wetlands, and peatlands increases greenhouse gas emissions: A global meta-analysis.

Abstract: Land-use/land-cover change (LULCC) often results in degradation of natural wetlands and affects the dynamics of greenhouse gases (GHGs). However, the magnitude of changes in GHG emissions from wetlands undergoing various LULCC types remains unclear. We conducted a global meta-analysis with a database of 209 sites to examine the effects of LULCC types of constructed wetlands (CWs), croplands (CLs), aquaculture ponds (APs), drained wetlands (DWs), and pastures (PASs) on the variability in CO2 , CH4 , and N2 O emissions from the natural coastal wetlands, riparian wetlands, and peatlands. Our results showed that the natural wetlands were net sinks of atmospheric CO2 and net sources of CH4 and N2 O, exhibiting the capacity to mitigate greenhouse effects due to negative comprehensive global warming potentials (GWPs; -0.9 to -8.7 t CO2 -eq ha-1 year-1 ). Relative to the natural wetlands, all LULCC types (except CWs from coastal wetlands) decreased the net CO2 uptake by 69.7%-456.6%, due to a higher increase in ecosystem respiration relative to slight changes in gross primary production. The CWs and APs significantly increased the CH4 emissions compared to those of the coastal wetlands. All LULCC types associated with the riparian wetlands significantly decreased the CH4 emissions. When the peatlands were converted to the PASs, the CH4 emissions significantly increased. The CLs, as well as DWs from peatlands, significantly increased the N2 O emissions in the natural wetlands. As a result, all LULCC types (except PASs from riparian wetlands) led to remarkably higher GWPs by 65.4%-2,948.8%, compared to those of the natural wetlands. The variability in GHG fluxes with LULCC was mainly sensitive to changes in soil water content, water table, salinity, soil nitrogen content, soil pH, and bulk density. This study highlights the significant role of LULCC in increasing comprehensive GHG emissions from global natural wetlands, and our results are useful for improving future models and manipulative experiments.