Flow Cytometry at Sea

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Plastics in blue carbon ecosystems: a call for global cooperation on climate change goals

Methane (CH4) and carbon dioxide (CO2) are widely acknowledged as the major greenhouse gases. Theoretically speaking, the mixture of methane and carbon dioxide would reform into gas fuels like hydrogen (H2) and carbon monoxide (CO) under certain treatment conditions. However, the traditional conversion of methane and carbon dioxide requires a high temperature, which can cause carbon deposition and deactivate the catalyst. Non-thermal plasma technology can alleviate this problem. In this research, a method of hydrogen production from greenhouse gases by non-thermal plasma was studied. We discussed the influence of plasma on the reforming of methane and carbon dioxide into hydrogen as functions of different parameters like power input, electrode gaps, total gas fluxes and methane/carbon dioxide ratios in customized single and double dielectric reactors. Meanwhile, the potential mechanism for the reforming has also been discussed. As a result, it was observed higher power input, smaller electrode gap and total gas flux would contribute to better performance of reforming. Based on the results of Fourier transform infrared spectroscopy and emission spectrum analysis, the mechanism of different reforming products such as carbon monoxide, hydrogen, other organic by-products and carbon deposition is discussed based on numerous free radicals including ·C, ·CHx, ·CO, ·H, and ·O in the discharge zone.

Chapter 1: Brief Overview of Carbon on Earth 1. An unusual look at Earth's shells 2. Global carbon cycle 3. Fundamental equation of a cycle and carbon flows 4. Carbon in Fossil Fuels 5. Feedbacks in the carbon cycle Chapter 2: Earth's Volatile Beginnings 1. The Major Volatiles 2. Primordial Atmosphere-Ocean System 3. Carbon Dioxide 4. Summary and Speculations 5. An Early Biosphere Chapter 3: Heat Balance of the Atmosphere and Carbon Dioxide 1. Heat Sources at the Earth's Surface 2. Solar Heating and Radiation Balance 3. Greenhouse Effect 4. Temperature of a Prebiotic Atmosphere 5. CO2 and Climate Change Chapter 4: Mineralogy, Chemistry, and Reaction Kinetics of the Major Carbonate Phases 1. Carbonate Minerals 2. Calcites 3. Dolomite 4. Aragonite 5. Carbonate Dissolution and Precipitation Kinetics 6. Carbonate Precipitation and Dissolution in Marine Ecosystems 7. Some Geological Considerations Chapter 5: Carbon Dioxide in Natural Waters 1. Dissolution and Dissociation of CO2 in Water 2. CO2 Transfer from Atmosphere to Water 3. Calcite and Aragonite in Natural Waters 4. Degree of Saturation With Respect to Carbonate Minerals 5. CO2 Phases: Gas, Liquid, Hydrate, Ice 6. Air-Sea CO2 Exchange due to Carbonate and Organic Carbon Formation Chapter 6: Isotopic Fractionation of Carbon: Inorganic and Biological Processes 1. Isotopic species and their abundance 2. Isotopic concentration units and mixing 3. Fractionation in inorganic systems 4. Photosynthesis and plant physiological responses to CO2 5. Biological fractionationand 13C cycle 6. Long-term trends Chapter 7: Sedimentary Rock Record and Oceanic and Atmospheric Carbon 1. Geologic Time Scale and Sedimentary Record 2. The Beginnings of Sedimentary Cycling 3. Broad Patterns of Sediment Lithologies 4. Differential Cycling of the Sedimentary Mass and Carbonates 5. Sedimentary Carbonate System 6. Evaporites and Fluid Inclusions 7. Isotopic Trends 8. Summary of the Phanerozoic Rock Record in Terms of Ocean Composition Chapter 8: Weathering and Consumption of CO2 1. Weathering Source: Sedimentary and Crystalline Lithosphere 2. Dissolution at the Earth's Surface 3. Mineral-CO2 Reactions in Weathering 4. CO2 Consumption from Mineral-Precipitation Model 5. CO2 Consumption from Mineral-Dissolution Model 6. Environmental Acid Forcing Chapter 9: Carbon in the Oceanic Coastal Margin 1. The Global Coastal Zone 2. Carbon Cycle in the Coastal Ocean 3. Inorganic and Organic Carbon 4. Marine Calcifying Organisms and Ecosystems 5. Present and Future of Coastal Carbon System Chapter 10: Natural Global Carbon Cycle through Time 1. The Hadean to Archaean 2. The Archaean to Proterozoic 3. The Phanerozoic 4. Pleistocene to Holocene Environmental Change Chapter 11: The Carbon Cycle in the Anthropocene 1. Characteristics of the Anthropocene 2. Major Perturbations in the Carbon Cycle: 1850 to the Early 21st Century 3. Partitioning of Carbon, Nitrogen and Phosphorus Fluxes 4. The Fundamental Carbon Problem of the Future

On the relation between organic and inorganic carbon in the Weddell Sea

The Snowball Earth hypothesis explains the development of glaciation at low latitudes in the Neoproterozoic, as well as the associated iron formations and cap carbonates, in terms of a runaway ice‐albedo feedback leading to a global glaciation followed by an extreme greenhouse climate. The initiation of a snowball glaciation is linked to a variety of unusual perturbations of the carbon cycle operating over different timescales, as evidenced by unusual patterns in the carbon isotopic composition of marine carbonate. Thus a theory for why multiple glaciations happened at this time, and not in the Phanerozoic nor earlier in the Proterozoic, requires a reexamination of the carbon cycle and the controls on climate stability. We propose that the concentration of continental area in the tropics was a critical boundary condition necessary for the onset of glaciation, both because the existence of substantial continental area at high latitudes may prevent atmospheric carbon dioxide from getting too low and because a tropical concentration of continental area may lead to more efficient burial of organic carbon through increased tropical river discharge. Efficient organic carbon burial sustained over tens of millions of years, required by the high carbon isotopic compositions of preglacial carbonate, may lead to the buildup of enormous quantities of methane, presumably in hydrate reservoirs. We examine how the slow release of this methane may explain the drop in δ13C values immediately before the glaciation. Moreover, the accumulation of methane in the atmosphere coupled with the response of silicate weathering to the additional greenhouse forcing can lead to a climate with methane as the major greenhouse gas. This situation is unstable because methane is not buffered by a large ocean reservoir like carbon dioxide, and so the collapse of the methane source may provide a trigger for the onset of a runaway ice‐albedo feedback. A simple model of the carbon cycle is used to explore the boundary conditions that would allow this to occur.

ntroduction: The previous reports from this laboratory have demonstrated the existence and growth of endosymbiotic actinidic archaea in human population which has been related to disease states like schizophrenia, autism, metabolic syndrome, cancer, autoimmune disease and degenerations. The overgrowth of endosymbiotic actinidic archaea results in neanderthalisation of humans. The overgrowth of endosymbiotic archaea results from the growth of homo sapien civilization. The homo sapien civilization results in industrialization and production of carbon dioxide, a greenhouse gas. The homo sapien civilization also results in widespread use of electronic devices like mobile phones and internet producing interconnectivity and a globalised world. The resultant low level EMF pollution also results in endosymbiotic archaeal growth. Carbon dioxide is a major greenhouse gas whose effects are long term but moderate. The archaea are methanogenic organisms. Methanogenesis results from the production of methane from carbon dioxide and hydrogen. Methanogenesis can also occur from formate and acetate. Acetate is the end product of carbohydrate, protein and lipid catabolism in humans. The human nutritional sources get metabolically converted to acetate and acetyl CoA which can enter the citric acid cycle and mitochondrial oxidative phosphorylation. The presence of endosymbiotic actinidic archaea results in conversion of acetate to formate and methane. It also results in conversion of the ubiquitous carbon dioxide and hydrogen to methane. Thus the human body due to endosymbiosis by archaea becomes the principal source of methanogenesis. Methane is an important greenhouse gas. The effect of methane is short term as compared to carbon dioxide. Methane being a larger molecule can produce absorption of long range radiation and its global warming potential is 29 times that of carbon dioxide. Thus the principal culprit for global warming and eventual catastrophic extinction of human society is methane produced by human endosymbiotic archaea. The archaeal overgrowth due to global warming can affect ocean beds and lakes. This results in warming of the ocean and instability of methane hydrates in the ocean bed releasing methane. The arctic permafrost decays releasing organic carbon which can be a source of methanogenesis by archaea. The study was conducted to evaluate the growth of actinidic archaea in humans. Materials and Methods: Cytochrome F420 levels were studied in the homo sapien population as well as human populations exhibiting the Neanderthal phenotype. Fifteen cases each of the above mentioned groups were chosen for the study. The blood samples were drawn in the fasting state. Cytochrome F420 was estimated flourimetrically (excitation wavelength 420 nm and emission wavelength 520 nm). The permission from the Ethics Committee of the Institute was obtained for this study. Results: The study showed that there was increased cytochrome F420 levels in the population with Neanderthal phenotype in the blood. This indicated the growth of archaeal endosymbionts in the Neanderthal phenotype. There was also increased cytochrome F420 level in the normal homo sapien population but the extent of increase was small. The blood samples were drawn in the fasting state. Discussion: Thus the increased production of greenhouse gases predominantly methane is from human sources alone due to increased growth of endosymbiotic archaea consequent to global warming triggered by industrial overproduction of carbon dioxide and EMF pollution. The homo sapien industrialisation is a small trigger but is rapidly taken over and dominated by endosymbiotic archaeal growth in humans. The archaeal overgrowth and neanderthalisation of homo sapiens converts the somatic cells to stem cells leading to cancer, autoimmune disease, degeneration and autism/schizophrenia in the neoneanderthal species. The Warburg phenotype of stem cells also produces the metabolic syndrome. The neoneanderthals becomes prone to civilisational disease. The neanderthalised humans stem cells phenotypes are retroviral resistant due to digoxin induced RNA editing, reverse transcriptase inhibition due to magnesium deficiency and membrane raft changes due to cholesterol depletion. The neanderthalised human stem cells serve as a reservoir for other species virus and bacteria resulting in breakage of the species barrier for infection. The archaeal symbionts can secrete RNA and DNA virus like particles which can recombine with expressed viral remnants in the genome as well as parts of the human genome per se producing new viruses and bacteria. The neanderthalised humans stem cells are resistant to infection which ravages the sensitive homo sapien phenotype exterminating them. Thus archaeal symbiosis, global warming, generation of new emerging viruses, pandemics of viral infections, homo sapien extinction and homo neanderthalis dominance becomes the rule. The realm of the homo neanderthalis sets in. The archaeal overgrowth in the oceanic beds and oceanic warming results in instability of methane hydrates in the ocean bed releasing methane. This produces global catastrophe. It results in oceanic earthquakes, continental shifts, tsunamis and flooding leading to eventual extinction of the human race of both species. Conclusion: Thus the human body due to endosymbiosis by archaea becomes the principal source of methanogenesis. Methane is an important greenhouse gas. The effect of methane is short term as compared to carbon dioxide. Methane being a larger molecule can produce absorption of long range radiation and its global warming potential is 29 times that of carbon dioxide. Thus the principal culprit for global warming and eventual catastrophic extinction of human society is methane produced by human endosymbiotic archaea.

δ 13 C in particulate organic carbon (POC), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), carbon dioxide (CO 2(g) ) and methane (CH 4(g) ), together with geochemical modeling, were applied to describe carbon cycle evolution in 40 boreal lakes situated across a permafrost thaw gradient in northeastern Alberta, Canada, where hydrological and geochemical trends had previously been established in a multi‐decadal study. Progressive carbon cycle succession, characterized by enhanced allochthonous carbon loading, methanogenesis, methane oxidation, and alteration of in‐lake DIC regulation, is found to progress in response to periodic water input increases associated with permafrost thaw, and has resulted in modification of the carbon cycle processes in post‐thaw lakes. Hydrologic indicators, including water yield (WY), groundwater—surface water ratio (GW/SW), and tritium content appear to undergo evolution across the thaw gradient, and proceed consistently among softwater, circumneutral, and hardwater lakes, although site‐specific differences in underlying organic versus inorganic carbon source balances are apparent. Progressive CO 2 supersaturation and CH 4 increases generally accompany permafrost thawing. Isotopic signatures suggest mainly acetoclastic methane production, found in previous studies to be common for newly‐thawed peatlands, subsequently modified by methane oxidation in 50% of lakes. Alteration of hydrologic, geochemical and carbon cycling processes has important implications for understanding potential trajectories of climate‐driven changes near the southern margin of the zone of discontinuous permafrost.

Large-scale CO2 disposal/storage in bedded rock salt caverns of China: An evaluation of safety and suitability

Methanotrophy is a biological process that effectively reduces global methane emissions by utilizing microorganisms that can utilize methane as a source of energy under both oxic and anoxic conditions, using a variety of different electron acceptors. Methanotrophic microbes, which utilize methane as their primary source of carbon and energy, are microorganisms found in various environments, such as soil, sediments, freshwater, and marine ecosystems. These microbes play a significant role in the global carbon cycle by consuming methane, a potent greenhouse gas, and converting it into carbon dioxide, which is less harmful. However, methane is known to be the primary contributor to ozone formation and is considered a major greenhouse gas. Methane alone contributes to 30% of global warming; its emissions increased by over 32% over the last three decades and thus affect humans, animals, and vegetation adversely. There are different sources of methane emissions, like agricultural activities, wastewater management, landfills, coal mining, wetlands, and certain industrial processes. In view of the adverse effects of methane, urgent measures are required to reduce emissions. Methanotrophs have attracted attention as multifunctional bacteria with potential applications in biological methane mitigation and environmental bioremediation. Methanotrophs utilize methane as a carbon and energy source and play significant roles in biogeochemical cycles by oxidizing methane, which is coupled to the reduction of various electron acceptors. Methanotrophy, a natural process that converts methane into carbon dioxide, presents a promising solution to mitigate global methane emissions and reduce their impact on climate change. Nonetheless, additional research is necessary to enhance and expand these approaches for extensive use. In this review, we summarize the key sources of methane, mitigation strategies, microbial aspects, and the application of methanotrophs in global methane sinks with increasing anthropogenic methane emissions.

The carbon cycle in agroecosystems is determined by the balance between the absorption of carbon dioxide by terrestrial vegetation of agricultural crops to create organic matter and its release during soil respiration. The soil cover is a powerful source of carbon dioxide and serves as a reservoir accumulating soil organic carbon. Organic carbon accumulating in the humus of soils serves as a drain of carbon dioxide, methane into the atmosphere for hundreds of years. The research was carried out in order to analyze the reserves of organic carbon in the soils of agroecosystems and assess the emission of CO2 and CH4 gases. The work was carried out in 2022-2023 at the site of a pilot carbon landfill (arable land) in the Republic of Bashkortostan. In field and laboratory experiments, technologies for controlling carbon dioxide emissions on agricultural lands were developed and tested. In the field, full-profile soil sections and digs were laid in accordance with GOST R58595-2019 with the determination of morphological properties and the selection of soil samples for laboratory analysis. Agrochemical analysis of the soil for the content of organic matter, the density of addition, the content of mobile phosphorus and potassium, the pH value allowed us to estimate the carbon stock of the soil of the carbon landfill according to the methodology of the Ministry of Natural Resources of the Russian Federation. The total reserves of organic carbon of the arable horizon at the carbon-new landfill amount to 503.8 t/ha, which vary and depend on the employment of the field and the characteristics of the agricultural crop. Measurement of the destructive part of the carbon cycle using a portable LI-COR 7810 camera showed that the fields occupied by crops differ in the intensity of the release of soil carbon dioxide ‒ in the field under pure steam, CO2 emissions were 2.18 times lower than under perennial grasses. The availability of data on the spatial distribution of organic soil carbon makes it possible to introduce carbon-dependent crop rotations with a set of crops that contribute to the maximum absorption of atmospheric CO2 and other greenhouse gases into the practice of agriculture.

By virtue of the large fraction of the terrestrial carbon (C) cycle controlled by human activities, agroecosystems are both sources and sinks for greenhouse gases. Their potential role in mitigation of climate change thus depends on a dual strategy of decreasing greenhouse gas emissions while increasing sinks so that the net impact on climate warming is less than at present. Emissions of carbon dioxide, methane and nitrous oxide arise from various agricultural activities, ranging from land clearing to ploughing, fertilization, and animal husbandry. Reductions in these emissions can be achieved by decreasing the heterotrophic conversion of organic C to carbon dioxide, and by better management of agricultural waste streams to minimize release of methane and nitrous oxide. Current sinks include C stored in standing biomass and soil organic matter, and the oxidation of atmospheric methane by soil bacteria. These sinks can be enhanced by increasing net primary productivity, thereby actively withdrawing more carbon dioxide from the atmosphere, and by promoting more oxidation of methane by soils. Judicious biochar management may contribute to both strategies, reductions of emissions by agriculture and active withdrawal of atmospheric carbon dioxide, as part of a comprehensive scheme in agricultural and forestry watersheds. Biochar is amore » carbon-rich organic material generated by heating biomass in the absence, or under a limited supply, of oxygen. This so-called charring or pyrolysis process has been used to produce charcoal as a source of fuel for millennia. Recently, interest has grown in understanding the potential of this process to improve soil health by adding biochar as an amendment to soil, to manage agricultural and forestry wastes, to generate energy, to decrease net emissions of nitrous oxide and methane, and to store carbon (C). The main incentive of biochar systems for mitigation of climate change is to increase the stability of organic matter or biomass. This stability is achieved by the conversion of fresh organic materials, which mineralize comparatively quickly, into biochar, which mineralizes much more slowly. The difference between the mineralization of uncharred and charred material results in a greater amount of carbon storage in soils and a lower amount of carbon dioxide, the major greenhouse gas, in the atmosphere. The principle of creating and managing biochar systems may address multiple environmental constraints. Biochar may help not only in mitigating climate change, but also fulfill a role in management of agricultural and forestry wastes, enhancement of soil sustainability, and generation of energy. Pyrolysis is a comparatively low-technology intervention. Deployment on a global scale, however, must be done carefully if the full mitigation potential is to be reached. Critical aspects of a successful implementation are that: 1) the biochar is sufficiently stable to reduce greenhouse gases in the atmosphere for an appropriate length of time. 2) the storage of carbon as biochar in soil is not offset by greenhouse gas emissions along the value chain of the system, such as mineralization of soil carbon or emissions of other greenhouse gases (e.g., methane and nitrous oxide). 3) net emission reductions are achieved for the entire life cycle of the system including indirect land use. 4) the biochar product does not cause unwanted side effects in soil. 5) the handling and production of biochar are in compliance with health and safety standards and do not pose hurdles to implementation. and 6) the biochar system is financially viable. This chapter discusses these issues in separate sections, identifies knowledge gaps, and proposes a road map to fully evaluate an environmentally and socially safe exploration of the biochar potential to mitigate climate change if adopted widely around the world.« less

Coastal seas, including coastal bays, are the geographically critical transitional zone that links terrestrial and open oceanic ecosystems. Organic carbon cycling in this area is a dynamic and disproportionally key component in the global carbon cycle and budget. As the thermally-transformed organic carbon produced exclusively from the incomplete combustion of biomass and fossil fuels, the recalcitrance and resultant longer environmental residence times result in important implications of black carbon (BC) in the global carbon budget. However, the environmental dynamics of BC in coastal seas have not well been constrained. In this study, we conducted one seawater sampling campaign in the high-intensity BC emission influenced Bohai Bay (BHB) and Laizhou Bay (LZB) in 2013, and quantified both particulate and dissolved BC (PBC and DBC). We elaborated the distributions, sources, and associated influencing factors of PBC and DBC in BHB and LZB in 2013, and simultaneously contrasted the PBC and DBC quantity and quality under two distinct fluvial hydrological regimes of 2013 and 2014 [discussed in Fang et al. (Environ. Sci. Technol., 2021, 55, 788–796)]. Except for the overwhelmingly high PBC in northern BHB caused by anthropogenic point-source emission, horizontally, both PBC and DBC showed a seaward decreasing trend, suggesting that riverine discharge was the major source for PBC and DBC. Vertically, in contrast to the uniform concentrations of DBC between surface and bottom waters, the PBC levels in bottom waters was significantly higher than that in surface waters, which was primarily resulted from the intense sediment re-suspension process during this sampling period. The nearly simultaneous investigations in 2013 and 2014 revealed consistent spatial patterns of PBC and DBC quantity and quality. But significantly lower PBC and DBC quantity and quality were found in 2014 than in 2013, which were largely due to the significantly different climatic conditions (including the watershed hydrology and sunlit radiation) between these 2 years.

The control of greenhouse gas is arguably the most challenging environmental policy issue facing China and other countries. CO 2 is considered to be the major greenhouse gas( GHG) contributing to global warming. Ocean is the largest active carbon pool,and plays an important role in globe climate change. And it is of great significance in the global carbon cycle to accurately estimate the absorbance,transformation,deposition rate of the carbon element in the marine ecosystem. In general,the air-sea CO 2 exchange fluxes were estimated from CO 2 partial pressure between the atmosphere and surface seawater,the primary productivity of phytoplankton was calculated by use of the biogeochemical models based on chlorophyll concentrations in the sea,particle organic carbon( POC) export fluxes in the euphotic zone were derived with 234Th—238U disequilibrium in the upper water column,and the organic carbon deposition rate was measured from210Pb specific activity vertical distribution in the sediment,respectively. Improvements in knowledge of the magnitude of this oceanic carbon uptake can be made thanks to an emerging international observation network that allow routine monitoring of the oceanic CO 2 uptake,on decadal and basin scales. However,not all uncertainties have been resolved,and the high variability of oceanic environments means that a unified description of marine carbon sequestration cannot yet be achieved. For example,there is no invaluable information to illustrate the mutual influence on carbon exchange flux in different medium of the atmosphere,sea water,and sedimentation,respectively,although the amount of carbon sequestration had been investigated in the single medium. There is unclear knowledge to indicate the key factors controlling carbon cycle process in the whole system,which includes the air-sea CO 2 exchange,the primary productivity of phytoplankton in the sea, POC export in the euphotic zone,and the organic carbon deposition in the sediment. It would be extremely challenging to quantify with acceptable accuracy the carbon sequestration in the ocean on a long term basis,and to adequately monitor unintended impacts over large space and time-scales. So,meaningful projections of future behavior of the oceanic sink are more challenging. Attempts to set a baseline stabilization target for the atmospheric CO 2 concentration will ultimately depend on an improved understanding of the oceanic mechanism regulating CO 2 uptake and the ability to make useful predictions of this parameter. To further improve the carbon sequestration assessment method in marine ecosystem,the comprehensive knowledge is required to form the assessment system that consists of the observation techniques,analysis method and the amount of carbon sequestration estimate. Furthermore,the index,criterion and standard,as well as evaluating the standard system of carbon sequestration in the marine ecosystem should be addressed in order to meet the demand of carbon reduction and carbon sink increase in China.

Beside carbon dioxide and methane, the atmospheric trace gas nitrous oxide (N2O) is a major greenhouse gas. It is predominantly produced in soils and aquatic systems during microbiological processes. Global N2O emissions have been substantially increased due to the intensification of agricultural practices and the related inputs of nitrogen compounds. High N2O concentrations were found in the groundwater of agricultural ecosystems. Thus, agricultural groundwater is assumed to be a potential source of N2O emissions into the atmosphere. The significance of N2O emissions from agricultural groundwater is the key question of this thesis. First, this key question is introduced in a preliminary chapter. In the following three chapters, different methods and approaches are described and discussed in order to provide knowledge of different aspects of the topic. Finally, these findings are assessed within the scope of a final synthesis and general conclusions are drawn. Research activities were conducted within four denitrifying aquifers in Lower Saxony, but the Fuhrberger Feld aquifer situated close to the city of Hannover was the main study site. In all investigated aquifers, the input of nitrate-contaminated agricultural seepage water causes elevated nitrate concentrations at the groundwater table. This nitrate is reduced during denitrification, yielding N2O as an intermediate and finally dinitrogen. The kinetics of N2O production and reduction in the Fuhrberger Feld aquifer was investigated during long-term anaerobic incubations. The results were compared with concentration profiles obtained from multilevel well measurements (chapter 2). It was confirmed that two vertically separated denitrification zones exist within the aquifer, heterotrophic denitrification in the surface groundwater and autotrophic denitrification in the deeper aquifer and both reactions were identified to be a significant source for N2O. The time courses of the N-species obtained from the laboratory incubations showed that heterotrophic denitrification is kinetically much slower than the autotrophic process. This was quantitatively proven by derived reaction rate constants following first order kinetics and attributed to the different microbial bioavailability of the associated electron donors, i.e. organic carbon and reduced sulfur compounds. The field measurements revealed considerable N2O accumulation in both denitrification zones, e.g. the mean N2O concentration close to the water table at one of the investigated wells was 1.84 mg N2O-N L-1. The N2O concentration profiles enabled a further refinement of the existing process model of denitrification in the Fuhrberger Feld aquifer. Within the scope of a 15N field experiment it was investigated to what extent groundwater-derived N2O emissions occurring via the vertical emission pathway contribute to total N2O emissions at the soil surface. This approach was based on stable labeling of the groundwater surface during the entire measuring period with K15NO3 tracer solution. 15N-labeled N2O was produced during denitrification and could be measured within the system groundwater / unsaturated zone / soil surface. Fluxes of groundwater-derived N2O were very low and found to be between 0.0002 und 0.0018 kg N2O-N ha-1 year-1. Only 0.13 % of the total positive N2O fluxes at the soil surface originated from groundwater-derived N2O. This showed that groundwater N2O emissions occurring via the vertical pathway are negligible in the Fuhrberger Feld aquifer. Determination and assessment of emission factors for indirect N2O emissions from agricultural groundwater was a further main objective of this thesis. A new emission factor basing on reconstructed initial nitrate concentrations was introduced. Thus, the concept relates potential N2O emission to the input of nitrogen to the groundwater surface. The application of this concept yielded emission factors that were considerably lower than conventional emission factors derived from the ratio between N2O concentrations and measured nitrate concentrations. This showed the necessity to take initial nitrate concentrations for calculating the groundwater N2O emission factor into account. The reaction kinetics as well as the evaluated rate constants (chapter 2) could be a basis for modeling the reactive transport of N2O and may contribute to further improve the emission factor for indirect N2O emissions from agricultural groundwater. Summarizing the results, it can be underlined for the investigated aquifers that N2O produced in groundwater is hardly reaching the atmosphere and thus contributes to a very low extent to total emissions of the greenhouse gas.