Biosphere-Atmosphere Gas Exchange Measurements using Fourier Transform Infrared Spectrometry

Field measurements of biosphere-atmosphere gas exchange are of great importance because they provide the possibility to study greenhouse gas dynamics and its feedback mechanisms in detail. This thesis contributes to the further development of concentration and flux measurement techniques to study biosphere-atmosphere exchange processes, by exploring the possibilities of using an in-situ Fourier Transform Infrared (FTIR)-analyzer for ecosystem research. This instrument is capable of measuring CO2, CH4, N2O, CO, and delta13CO2 simultaneously. It was combined with different flux measurement techniques, such as the flux gradient technique, the ratio-nocturnal boundary layer technique, and the flux chamber technique. The system was used in four different field campaigns and several laboratory studies. This thesis focuses on the use of the system to a) apply and assess different (new) flux measurement techniques, and b) study different flux and ecosystem processes

Biosphere-Atmosphere Gas Exchange Measurements using Fourier Transform Infrared Spectrometry

Field measurements of biosphere-atmosphere gas exchange are of great importance because they provide the possibility to study greenhouse gas dynamics and its feedback mechanisms in detail. This thesis contributes to the further development of concentration and flux measurement techniques to study biosphere-atmosphere exchange processes, by exploring the possibilities of using an in-situ Fourier Transform Infrared (FTIR)-analyzer for ecosystem research. This instrument is capable of measuring CO2, CH4, N2O, CO, and delta13CO2 simultaneously. It was combined with different flux measurement techniques, such as the flux gradient technique, the ratio-nocturnal boundary layer technique, and the flux chamber technique. The system was used in four different field campaigns and several laboratory studies. This thesis focuses on the use of the system to a) apply and assess different (new) flux measurement techniques, and b) study different flux and ecosystem processes

Global soil consumption of atmospheric carbon monoxide : an analysis using a process-based biogeochemistry model

Carbon monoxide (CO) plays an important role in controlling the oxidizing capacity of the atmosphere by reacting with OH radicals that affect atmospheric methane (CH4) dynamics. We develop a process-based biogeochemistry model to quantify the CO exchange between soils and the atmosphere with a 5 min internal time step at the global scale. The model is parameterized using the CO flux data from the field and laboratory experiments for 11 representative ecosystem types. The model is then extrapolated to global terrestrial ecosystems using monthly climate forcing data. Global soil gross consumption, gross production, and net flux of the atmospheric CO are estimated to be from -197 to -180, 34 to 36, and -163 to -145 TgCOyr(-1) (1 Tg = 10(12) g), respectively, when the model is driven with satellite-based atmospheric CO concentration data during 2000-2013. Tropical evergreen forest, savanna and deciduous forest areas are the largest sinks at 123 TgCOyr(-1). The soil CO gross consumption is sensitive to air temperature and atmospheric CO concentration, while the gross production is sensitive to soil organic carbon (SOC) stock and air temperature. By assuming that the spatially distributed atmospheric CO concentrations (similar to 128 ppbv) are not changing over time, the global mean CO net deposition velocity is estimated to be 0.16-0.19mms 1 during the 20th century. Under the future climate scenarios, the CO deposition velocity will increase at a rate of 0.0002-0.0013 mms 1 r(-1) during 2014-2100, reaching 0.20-0.30 mm s(-1) by the end of the 21st century, primarily due to the increasing temperature. Areas near the Equator, the eastern US, Europe and eastern Asia will be the largest sinks due to optimum soil moisture and high temperature. The annual global soil net flux of atmospheric CO is primarily controlled by air temperature, soil temperature, SOC and atmospheric CO concentrations, while its monthly variation is mainly determined by air temperature, precipitation, soil temperature and soil moisture.Peer reviewe

How rainfall events modify trace gas mixing ratios in central Amazonia

This study investigates the rain-initiated mixing and variability in the mixing ratio of selected trace gases in the atmosphere over the central Amazon rain forest. It builds on comprehensive data from the Amazon Tall Tower Observatory (ATTO), spanning from 2013 to 2020 and comprising the greenhouse gases (GHGs) carbon dioxide (CO2) and methane (CH4); the reactive trace gases carbon monoxide (CO), ozone (O3), nitric oxide (NO), and nitrogen dioxide (NO2); and selected volatile organic compounds (VOCs). Based on more than 1000 analyzed rainfall events, the study resolves the trace gas mixing ratio patterns before, during, and after the rain events, along with vertical mixing ratio gradients across the forest canopy. The assessment of the rainfall events was conducted independently for daytime and nighttime periods, which allows us to elucidate the influence of solar radiation. The mixing ratios of CO2, CO, and CH4 clearly declined during rainfall, which can be attributed to the downdraft-related entrainment of pristine air from higher altitudes into the boundary layer, a reduction of the photosynthetic activity under increased cloud cover, and changes in the surface fluxes. Notably, CO showed a faster reduction than CO2, and the vertical gradient of CO2 and CO is steeper than for CH4. Conversely, the O3 mixing ratio increased across all measurement heights in the course of the rain-related downdrafts. Following the O3 enhancement by up to a factor of 2, NO, NO2, and isoprene mixing ratios decreased. The temporal and vertical variability of the trace gases is intricately linked to the diverse sink and source processes, surface fluxes, and free-troposphere transport. Within the canopy, several interactions unfold among soil, atmosphere, and plants, shaping the overall dynamics. Also, the mixing ratio of biogenic VOCs (BVOCs) clearly varied with rainfall, driven by factors such as light, temperature, physical transport, and soil processes. Our results disentangle the patterns in the trace gas mixing ratio in the course of sudden and vigorous atmospheric mixing during rainfall events. By selectively uncovering processes that are not clearly detectable under undisturbed conditions, our results contribute to a better understanding of the trace gas life cycle and its interplay with meteorology, cloud dynamics, and rainfall in the Amazon.This research has been supported by the Max Planck Society, the FAPESP grant no. 2022/07974-0, and the Bundesministerium für Bildung und Forschung (BMBF contract nos. 01LB1001A, 01LK1602B, 01LK1602C, and 01LK2101B).Peer reviewe

Biosphäre-Atmosphäre Gas Austausch Messungen unter Verwendung von Fourier Transformations Infrarot Spektrometry

Field measurements of biosphere-atmosphere gas exchange are of great importance because they provide the possibility to study greenhouse gas dynamics and its feedback mechanisms in detail. This thesis contributes to the further development of concentration and flux measurement techniques to study biosphere-atmosphere exchange processes, by exploring the possibilities of using an in-situ Fourier Transform Infrared (FTIR)-analyzer for ecosystem research. This instrument is capable of measuring CO2, CH4, N2O, CO, and delta13CO2 simultaneously. It was combined with different flux measurement techniques, such as the flux gradient technique, the ratio-nocturnal boundary layer technique, and the flux chamber technique. The system was used in four different field campaigns and several laboratory studies. This thesis focuses on the use of the system to a) apply and assess different (new) flux measurement techniques, and b) study different flux and ecosystem processes

The emission of CO from tropical rainforest soils

<jats:p>Abstract. Soil carbon monoxide (CO) fluxes represent a net balance between biological soil CO uptake and abiotic soil and (senescent) plant CO production. Studies largely from temperate and boreal forests indicate that soils serve as a net sink for CO, but uncertainty remains about the role of tropical rainforest soils to date. Here we report the first direct measurements of soil CO fluxes in a tropical rainforest and compare them with estimates of net ecosystem CO fluxes derived from accumulation of CO at night under stable atmospheric conditions. Furthermore, we used laboratory experiments to demonstrate the importance of temperature on net soil CO fluxes. Net soil surface CO fluxes ranged from −0.19 to 3.36 nmol m−2 s−1, averaging ∼1 nmol CO m−2 s−1. Fluxes varied with season and topographic location, with the highest fluxes measured in the dry season in a seasonally inundated valley. Ecosystem CO fluxes estimated from nocturnal canopy air profiles, which showed CO mixing ratios that consistently decreased with height, ranged between 0.3 and 2.0 nmol CO m−2 s−1. A canopy layer budget method, using the nocturnal increase in CO, estimated similar flux magnitudes (1.1 to 2.3 nmol CO m−2 s−1). In the wet season, a greater valley ecosystem CO production was observed in comparison to measured soil valley CO fluxes, suggesting a contribution of the valley stream to overall CO emissions. Laboratory incubations demonstrated a clear increase in CO production with temperature that was also observed in field fluxes, though high correlations between soil temperature and moisture limit our ability to interpret the field relationship. At a common temperature (25 °C), expected plateau and valley senescent-leaf CO production was small (0.012 and 0.002 nmol CO m−2 s−1) in comparison to expected soil material CO emissions (∼ 0.9 nmol CO m−2 s−1). Based on our field and laboratory observations, we expect that tropical rainforest ecosystems are a net source of CO, with thermal-degradation-induced soil emissions likely being the main contributor to ecosystem CO emissions. Extrapolating our first observation-based tropical rainforest soil emission estimate of ∼ 1 nmol m−2 s−1, global tropical rainforest soil emissions of ∼ 16.0 Tg CO yr−1 are estimated. Nevertheless, total ecosystem CO emissions might be higher, since valley streams and inundated areas might represent local CO emission hot spots. To further improve tropical forest ecosystem CO emission estimates, more in situ tropical forest soil and ecosystem CO flux measurements are essential. </jats:p&gt