Diurnal Variations Of CO2 Fluxes Research Articles

The carbon dioxide fluxes at the open-top chambers experiment on the ombrotrophic bog (Mukhrino field station)

The continuous measurement of CO2 fluxes at the open-top chamber experiment in the ombrotrophic peatland (located in the middle taiga zone, West Siberia, Russia) has been provided during the warm season of 2022 (beginning of June to beginning of October). The Reco, NEE and GPP were calculated for this period; abiotic factors related to CO2 emissions, such as PAR, air temperature, water table level and precipitation, were also measured. The monthly average values showed a negative NEE of -9.89 C g m-2 month-1 in July, a negative GPP of -34.19 C g m-2 month-1 in July, and a positive values Reco of 41.68 C g m-2 month-1 in August. In 2022, the studied peatland hollows were only a carbon stock in July, while in the remaining months they were a source of CO2, which could be caused by small precipitation amount.
 The monthly average diurnal variations of CO2 fluxes showed similar behaviour for both the OTC plot and control plot fluxes, which may be explained by the similarity in vegetation cover.

Characteristics of CO2 flux and its influence factors over winter wheat agroecosystem in the North China Plain

Using CO2 flux data of winter wheat recorded by eddy covariance system, combined with the meteorological data, we examined the diurnal variations of CO2 fluxes in four growth stages (tillering stage, overwintering stage, jointing stage and filling stage) of winter wheat in an agroecosystem of the North China Plain from 2013 to 2014. The seasonal variation of net ecosystem exchange and its relationship with meteorological factors were investigated. The results showed that the net ecosystem exchange in the whole growing season was -360.15 g C·m-2. The gross primary productivity in the whole growing season was 1920.01 g C·m-2. The winter wheat agroecosystem had strong capacity in carbon sequestration. The CO2 fluxes showed an obvious diurnal and seasonal variation characteristics in winter wheat agroecosystem. This ecosystem was a carbon source in tillering stage, while it was a carbon sink in overwintering stage, jointing stage and filling stage. The mean value of apparent initial light energy utilization was 0.03 mg CO2·μmol-1. The mean value of ecosystem production was 1.53 mg CO2·m-2·s-1 when light was saturated. The monthly average value of ecosystem respiration was 193.92 g C·m-2·month-1. The net ecosystem exchange and photosynthetically active radiation had a significant correlation in four growth stages of winter wheat. The correlations between net ecosystem exchange and vapor pressure deficit were significant in all the growth stages. There was a positive correlation between daily total net ecosystem exchange and soil temperature in tillering stage, overwintering stage and filling stage, but a negative correlation between them in jointing stage.

Carbon dioxide emissions from a septic tank soakaway in a northern maritime climate.

Here, we present the first attempt to quantify long-term and diurnal variations of CO2 fluxes from a soakaway of an on-site wastewater treatment system serving a single house located in a northern maritime climate (Ireland). An automated soil gas flux chamber system was deployed semi-continuously over a period of 17months, recording hourly flux measurements from the soakaway (Fsoak) and a control site (Fcontrol). Soil gas fluxes expressed seasonal and diurnal variations: Fsoak and Fcontrol ranged from 0.43 to 100.26μmolCO2m-2s-1 and 0.45 to 19.92μmolCO2m-2s-1 with median fluxes of 6.86 and 5.05μmolCO2m-2s-1, respectively. While temperature, soil water content, and atmospheric pressure were identified as the most significant environmental factors correlated to the release of CO2 from the control site, fluxes from the soakaway showed weaker correlations in regard to environmental factors. Assuming homogeneous spatial flux distributions, the soakaway emitted 15.0kgyr-1 more CO2 into the atmosphere in total compared to a similarly sized control site.

Variations in CO2 fluxes from grass carp Ctenopharyngodon idella aquaculture polyculture ponds

Monthly and diurnal CO2 fluxes at the waterair interface were measured in 3 grass carp Ctenopharyngodon idella polyculture ponds using the closed-chamber method during the farming season from April to September 2013. The results showed that the mean CO2 emission rate from the 3 ponds was 97.8 mg m −2 h −1 (range 50.6 to 151.0 mg m −2 h −1 ). Apparent seasonal and diurnal variations in CO2 fluxes were observed; the lowest (1.73 mg m −2 h −1 ) occurred in April and the highest occurred in July and August (212.9 and 181.9 mg m −2 h −1 , respectively). The night-time to daytime CO2 emission ratio was <1 (range 0.44 to 0.83) in May during the early part of the farm- ing season. Night-time CO2 emissions in early August were higher than those during the daytime (range 1.06 to 1.37). The night-time to daytime CO2 emission ratios were 0.84 to 1.36 during late September. The CO2 fluxes from the freshwater aquaculture ponds were higher than those of lakes and reservoirs, whereas they were lower than those of marshes in previous studies. The increases in nutrient load and pelagic respiration from feeding the fish were significantly associ- ated with CO2 emissions from the freshwater aquaculture ponds. Freshwater aquaculture ponds in temperate monsoon climate regions contribute an estimated 2.98 million t yr −1 CO2 based on the mean investigated CO2 emission rate, contributing 0.0088% of the current annual global CO2 emissions, and represent a small but previously unquantified CO2 emission source.

Diurnal and seasonal variations in carbon dioxide exchange in ecosystems in the Zhangye oasis area, Northwest China.

Quantifying carbon dioxide exchange and understanding the response of key environmental factors in various ecosystems are critical to understanding regional carbon budgets and ecosystem behaviors. For this study, CO2 fluxes were measured in a variety of ecosystems with an eddy covariance observation matrix between June 2012 and September 2012 in the Zhangye oasis area of Northwest China. The results show distinct diurnal variations in the CO2 fluxes in vegetable field, orchard, wetland, and maize cropland. Diurnal variations of CO2 fluxes were not obvious, and their values approached zero in the sandy desert, desert steppe, and Gobi ecosystems. Additionally, daily variations in the Gross Primary Production (GPP), Ecosystem Respiration (Reco) and Net Ecosystem Exchange (NEE) were not obvious in the sandy desert, desert steppe, and Gobi ecosystems. In contrast, the distributions of the GPP, Reco, and NEE show significant daily variations, that are closely related to the development of vegetation in the maize, wetland, orchard, and vegetable field ecosystems. All of the ecosystems are characterized by their carbon absorption during the observation period. The ability to absorb CO2 differed significantly among the tested ecosystems. We also used the Michaelis-Menten equation and exponential curve fitting methods to analyze the impact of Photosynthetically Active Radiation (PAR) on the daytime CO2 flux and impact of air temperature on Reco at night. The results show that PAR is the dominant factor in controlling photosynthesis with limited solar radiation, and daytime CO2 assimilation increases rapidly with PAR. Additionally, the carbon assimilation rate was found to increase slowly with high solar radiation. The light response parameters changed with each growth stage for all of the vegetation types, and higher light response values were observed during months or stages when the plants grew quickly. Light saturation points are different for different species. Nighttime Reco increases exponentially with air temperature. High Q10 values were observed when the vegetation coverage was relatively low, and low Q10 values occurred when the vegetables grew vigorously.

CO2 sources and sinks in urban and suburban areas of a northern mid-latitude city

Abstract Urban environments can modify the local climate and are net CO2 emitters, both of which can affect the life of an increasing proportion of the world’s population that lives in and around cities. Observational information on the seasonal and diurnal variations of CO2 fluxes ( F CO 2 ) as well as on the contribution from the different CO2 sources and sinks is needed at fine spatial resolution to help develop and validate weather prediction and atmospheric dispersion models. This study reports on F CO 2 measured using the eddy covariance technique for a two-year period over a suburban and an urban residential area as well as a reference agricultural site located in the Montreal region, which experiences cold winters and warm summers. The seasonal and diurnal variability of F CO 2 and its response to incoming light and to air temperature was analysed. Typical weekday and weekend vehicular traffic CO2 emissions (EVT) were estimated from inventory data for both residential sites. The urban site was a net source of CO2 throughout the entire measurement period on the order of 200 t CO2 ha−1 year−1. The suburban site was a winter source and a summer daytime sink of CO2 resulting in a net source of 50 t CO2 ha−1 y−1. Lower emissions at the suburban site are attributed to the large biological uptake in summer and to its low anthropogenic emissions. Higher emissions at the urban site are partly associated with its greater population and building density, promoting higher emissions from vehicular traffic and heating fuel combustion. The cold climate induced increased heating fuel combustion as compared to cities under a warmer climate.