Comparison of Cooling System Designs for an Exhaust Heat Recovery System Using an Organic Rankine Cycle on a Heavy Duty Truck

A complex simulation model of a heavy duty truck, including an Organic Rankine Cycle (ORC) based waste heat recovery system and a vehicle cooling system, was applied to determine the system fuel economy potential in a typical drive cycle. Measures to increase the system performance were investigated and a comparison between two different cooling system designs was derived. The base design, which was realized on a Mercedes-Benz Actros vehicle revealed a fuel efficiency benefit of 2.6%, while a more complicated design would generate 3.1%. Furthermore, fully transient simulation results were performed and are compared to steady state simulation results. It is shown that steady state simulation can produce comparable results if averaged road data are used as boundary conditions

Functional, not Taxonomic, Composition of Soil Fungi Reestablishes to Pre-mining Initial State After 52 Years of Recultivation

Open-cast mining leads to the loss of naturally developed soils and their ecosystem functions and services. Soil restoration after mining aims to restore the agricultural productivity in which the functions of the fungal community play a crucial role. Whether fungi reach a comparable functional state as in the soil before mining within half a century of recultivation is still unanswered. Here, we characterised the soil fungal community using ITS amplicon Illumina sequencing across a 52-year chronosequence of agricultural recultivation after open-cast mining in northern Europe. Both taxonomic and functional community composition showed profound shifts over time, which could be attributed to the changes in nutrient status, especially phosphorus availability. However, taxonomic composition did not reach the pre-mining state, whereas functional composition did. Importantly, we identified a positive development of arbuscular mycorrhizal root fungal symbionts after the initial three years of alfalfa cultivation, followed by a decline after conversion to conventional farming, with arbuscular mycorrhizal fungi being replaced by soil saprobes. We conclude that appropriate agricultural management can steer the fungal community to its functional pre-mining state despite stochasticity in the reestablishment of soil fungal communities. Nonetheless, conventional agricultural management results in the loss of plant symbionts, favouring non-symbiotic fungi

Dolerite fines used as a calcium source for microbially induced calcite precipitation reduce the environmental carbon cost in sandy soil

Microbial-Induced Calcite Precipitation (MICP) stimulates soil microbiota to induce a cementation of the soil matrix. Urea, calcium and simple carbon nutrients are supplied to produce carbonates via urea hydrolysis and induce the precipitation of the mineral calcite. Calcium chloride (CaCl2) is typically used as a source for calcium, but silicate rocks and other materials have been investigated as alternatives. Weathering of calcium-rich silicate rocks (e.g. basalt and dolerite) releases calcium, magnesium and iron; this process is associated with sequestration of atmospheric CO2 and formation of pedogenic carbonates. We investigated atmospheric carbon fluxes of a MICP treated sandy soil using CaCl2 and dolerite fines applied on the soil surface as sources for calcium. Soil-atmosphere carbon fluxes were monitored over two months and determined with an infrared gas analyser connected to a soil chamber. Soil inorganic carbon content and isotopic composition were determined with isotope-ratio mass spectrometry. In addition, soil-atmosphere CO2 fluxes during chemical weathering of dolerite fines were investigated in incubation experiments with gas chromatography. Larger CO2 emissions resulted from the application of dolerite fines (116 g CO2-C m-2) compared to CaCl2 (79 g CO2-C m-2) but larger inorganic carbon precipitation also occurred (172.8 g C m-2 and 76.9 g C m-2, respectively). Normalising to the emitted carbon to precipitated carbon, the environmental carbon cost was reduced with dolerite fines (0.67) compared to the traditional MICP treatment (1.01). The carbon isotopic signature indicated pedogenic carbonates (δ13Cav = 8.2±5.0‰) formed when dolerite was applied and carbon originating from urea (δ13Cav = 46.4±1.0‰) precipitated when CaCl2 was used. Dolerite fines had a large but short-lived (<2 d) carbon sequestration potential, and results indicated peak CO2 emissions during MICP could be balanced optimizing the application of dolerite fines

Hydroxylamine Contributes More to Abiotic N2O Production in Soils Than Nitrite

Nitrite (NO2-) and hydroxylamine (NH2OH) are important intermediates of the nitrogen (N) cycle in soils. They play a crucial role in the loss of nitrous oxide (N2O) and nitric oxide (NO) from soil due to their high reactivity. In this study, we collected soil samples from three ecosystems (grassland, arable land, and forest with a riparian zone) and explored the contribution of NO2- and NH2OH to N2O formation in the different soils after exposure to oxic or anoxic pre-treatment. In addition, the importance of abiotic processes on the N2O formation from the two intermediates was studied by irradiating the soil samples with γ-irradiation. Our results demonstrate that NO2- addition induced the largest N2O production in the grassland soil, followed by the forest and arable soils. Only 9–39% of the produced N2O after NO2- addition came from abiotic processes. NH2OH addition increased N2O emissions the most from the arable soil, followed by the grassland and forest soils. The conversion of NH2OH to N2O was mostly (73–93%) abiotic. Anoxic pre-treatment decreased N2O production from NH2OH remarkably, especially for the grassland soil, while it increased N2O production from NO2- for most of the soils. Correlation analysis showed that NO2- effects on N2O production were strongly correlated to NH4+ content in soils with anoxic pre-treatment, while NH2OH effects on N2O production were strongly correlated to soil Mn and C content in soils with oxic pre-treatment. Our results indicate that NH2OH plays an important role for abiotic N2O formation in soils with low C and high Mn content, while the effect of NO2- was important mainly during biotic N2O production. Anoxic periods prior to N addition may increase the contribution of NO2-, but reduce the contribution of NH2OH, to soil N2O formation

Influence of wind speed and wind direction above the sea surface on the diffusive methane flux and the atmospheric methane concentration at the North Sea

The estimations of the diffusive methane flux from the water phase into the atmosphere in coastal waters is relevant for a better estimate of the atmospheric greenhouse-gas budget. Unfortunately, so far, the numerical determination of the fluxes has a high level of uncertainty in coastal waters. To improve the estimation of coastal methane fluxes, not only a high temporal and spatial sampling resolution of the dissolved methane in the water are required. Besides, also the atmospheric methane concentration and the wind speed and wind direction above the surface is important. In most cases, these atmospheric data are obtained from near-by atmospheric and meteorologic monitoring stations. In this study, we measured wind speed, direction and atmospheric methane local directly on board of three research vessel cruising in the southern North Sea within the MOSES project and compared the effects of local versus remote measurements of these data on the flux data. In addition, using the wind direction and speed, we try to assess the origin of the atmospheric methane measured in the study area. Using these “improved” data sets, we discuss if local measurements of auxiliary data provide better insights in the determining factors of the methane flux, and thus also improve the regional aquatic methane budget

Infrastructures for agroecological field research – Current situation and future prospectsPosition paper of the DFG Senate Commission on Agroecosystem Research

Groß angelegte und langfristig etablierte Feldversuche sind ein zentrales Element der standortbezogenen Agrarwissenschaften. Die Erarbeitung des Grundlagenwissens zu standortangepassten bzw. regionalspezifischen Produktivitätspotentialen von Pflanzenbeständen sowie die Entwicklung von ökologisch vertretbaren, innovativen Produktionssystemen mit hoher Produktivität und Resi­lienz erfordern leistungsfähige Forschungsinfrastrukturen, die relevante Gradienten an Klima- und Bodenfaktoren abdecken und den interdisziplinären Dialog fördern. Das Positionspapier der Senatskommission für Agrar­öko­systemforschung der Deutschen Forschungsgemeinschaft stellt den Status quo und die zukünftigen Anforderungen an Feldversuchseinrichtungen dar. Zur Optimierung des agrarwissenschaftlichen Feldversuchswesens wird angeregt, in einem Netzwerk aus Versuchseinrichtungen Landschaftsfunktionen prototypisch abzubilden, um in einem interdisziplinären Ansatz Flächenproduktivität, Resilienz und Ressourceneffizienz landschaftsspezifisch untersuchen zu können. Des Weiteren ist es erforderlich, der wissenschaftlichen Community standardisierte Daten in Datenrepositorien zur Verfügung zu stellen. DOI: 10.5073/JfK.2014.07.02, https://doi.org/10.5073/JfK.2014.07.02Large-scale, long-term field experiments are a core element of site-specific agricultural science. To create basic knowledge of site-adapted and regional agricultural production potentials as well as to develop ecologically sound and innovative plant production systems with high productivity and resilience requires high-capacity research infrastructures that cover relevant climatic gradients and soils and that promote an interdisciplinary dialog. The position paper of the Senate Commission on Agroecosystem Research of the Deutsche Forschungsgemeinschaft shows the current status and future requirements on infrastructures for agroecological field research. To optimize the infrastructure for agricultural field trials, a network of experimental sites that cover prototype landscape functions is suggested, enabling interdisciplinary investigations of productivity, resilience and resource efficiency in the landscape context. Further it is necessary to provide standardized data in open access data repositories to the scientific community. DOI: 10.5073/JfK.2014.07.02, https://doi.org/10.5073/JfK.2014.07.0

Nitrogen fertilizer fate after introducing maize and upland-rice into continuous paddy rice cropping systems

Water scarcity and economic incentives favor the introduction of upland crops into permanent paddy rice systems during dry seasons. However, introducing upland crops into permanently flooded cropping systems temporarily changes soil conditions from anaerobic to aerobic, affecting nitrogen (N) dynamics profoundly. We hypothesized that under maize and dry rice, total fertilizer $^{15}$N recovery in soil as well as the immobilization of fertilizer $^{15}$N in microbial residues is reduced compared with continuous paddy rice cropping. Furthermore, we expected enhanced emissions of fertilizer $^{15}$N in form of nitrous oxide (N₂O) under maize and dry rice. To test these hypotheses, we traced the fate of a $^{15}$N-urea pulse in a field experiment in the Philippines with three different crop rotations: continuous paddy rice, paddy rice – dry rice, and paddy rice – maize for two years. Indeed, the $^{15}$N recovery in the first 5 cm of bulk soil was lowest in the paddy rice – maize rotation (arithmetic mean with standard error: 19.2 ± 1.8% of applied $^{15}$N), while twice as much was recovered in the first 5 cm of bulk soil of the continuous paddy rice cropping systems (37.8 ± 2.2% of applied $^{15}$N) during the first dry season. The $^{15}$N recovery in the plant biomass (shoots and roots) in the continuous paddy rice cropping was 13% larger than in the dry rice plant biomass and 5% larger than in the maize plant biomass during the first dry season. Fertilizer $^{15}$N remained longest in paddy rice – maize (mean residence time=90 ± 25 days) and in continuous paddy rice (mean residence time=77 ± 30 days), compared with dry rice – paddy rice rotation (mean residence time=16 ± 5 days). After 2 years, 10% (paddy rice – dry rice, paddy rice – maize) to 23% (continuous paddy rice) of the applied fertilizer 15N were still stored in soil. The largest fraction of this $^{15}$N was immobilized by soil microbes, which stored 3-4% of applied 15N in the form of amino sugars as specific cell wall constituents, in all cropping systems. Nevertheless, introducing upland crops into continuous paddy rice systems likely increased N leaching losses and resulted in initial losses of urea- $^{15}$N to N₂O, which thus has to be considered in climate smart mitigation strategies