TY - JOUR A1 - Puppe, Daniel A1 - Leue, Martin A1 - Sommer, Michael A1 - Schaller, Jörg A1 - Kaczorek, Danuta T1 - Auto-fluorescence in phytoliths BT - a mechanistic understanding derived from microscopic and spectroscopic analyses JF - Frontiers in Environmental Science N2 - The detection of auto-fluorescence in phytogenic, hydrated amorphous silica depositions (phytoliths) has been found to be a promising approach to verify if phytoliths were burnt or not, especially in archaeological contexts. However, it is unknown so far at what temperature and how auto-fluorescence is induced in phytoliths. We used fluorescence microscopy, scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), and Fourier transform infrared spectroscopy to analyze auto-fluorescence in modern phytoliths extracted from plant samples or in intact leaves of winter wheat. Leaves and extracted phytoliths were heated at different temperatures up to 600 degrees C. The aims of our experiments were i) to find out what temperature is needed to induce auto-fluorescence in phytoliths, ii) to detect temperature-dependent changes in the molecular structure of phytoliths related to auto-fluorescence, and iii) to derive a mechanistic understanding of auto-fluorescence in phytoliths. We found organic compounds associated with phytoliths to cause auto-fluorescence in phytoliths treated at temperatures below approx. 400 degrees C. In phytoliths treated at higher temperatures, i.e., 450 and 600 degrees C, phytolith auto-fluorescence was mainly caused by molecular changes of phytolith silica. Based on our results we propose that auto-fluorescence in phytoliths is caused by clusterization-triggered emissions, which are caused by overlapping electron clouds forming non-conventional chromophores. In phytoliths heated at temperatures above about 400 degrees C dihydroxylation and the formation of siloxanes result in oxygen clusters that serve as non-conventional chromophores in fluorescence events. Furthermore, SEM-EDX analyses revealed that extractable phytoliths were dominated by lumen phytoliths (62%) compared to cell wall phytoliths (38%). Our findings might be not only relevant in archaeological phytolith-based examinations, but also for studies on the temperature-dependent release of silicon from phytoliths and the potential of long-term carbon sequestration in phytoliths. KW - fluorescence microscopy KW - FTIR spectroscopy KW - SEM-EDX KW - burnt phytoliths; KW - carbon sequestration Y1 - 2022 U6 - https://doi.org/10.3389/fenvs.2022.915947 SN - 2296-665X VL - 10 PB - Frontiers Media CY - Lausanne ER - TY - JOUR A1 - Siegmund, Nicole A1 - Panebianco, Juan E. A1 - Avecilla, Fernando A1 - Iturri, Laura Antonela A1 - Sommer, Michael A1 - Buschiazzo, Daniel A1 - Funk, Roger T1 - From gustiness to dustiness BT - the impact of wind gusts on particulate matter emissions in field experiments in La Pampa, Argentina JF - Atmosphere N2 - This study delivers the first empirical data-driven analysis of the impact of turbulence induced gustiness on the fine dust emissions from a measuring field. For quantification of the gust impact, a new measure, the Gust uptake Efficiency (GuE) is introduced. GuE provides a percentage of over- or under-proportional dust uptake due to gust activity during a wind event. For the three analyzed wind events, GuE values of up to 150% could be found, yet they significantly differed per particle size class with a tendency for lower values for smaller particles. In addition, a high-resolution correlation analysis among 31 particle size classes and wind speed was conducted; it revealed strong negative correlation coefficients for very small particles and positive correlations for bigger particles, where 5 mu m appears to be an empirical threshold dividing both directions. We conclude with a number of suggestions for further investigations: an optimized field experiment setup, a new particle size ratio (PM1/PM0.5 in addition to PM10/PM2.5), as well as a comprehensive data-driven search for an optimal wind gust definition in terms of soil erosivity. KW - wind gusts KW - wind erosion KW - particle uptake KW - dust plumes Y1 - 2022 U6 - https://doi.org/10.3390/atmos13081173 SN - 2073-4433 VL - 13 IS - 8 PB - MDPI CY - Basel ER - TY - JOUR A1 - Siegmund, Nicole A1 - Funk, Roger A1 - Sommer, Michael A1 - Avecilla, Fernando A1 - Esteban Panebianco, Juan A1 - Iturri, Laura Antonela A1 - Buschiazzo, Daniel T1 - Horizontal and vertical fluxes of particulate matter during wind erosion on arable land in the province La Pampa, Argentina JF - International journal of sediment research N2 - A detailed analysis of horizontal and vertical particulate matter (PM) fluxes during wind erosion has been done, based on measurements of PM smaller than 10, 2.5, and 1.0 mu mm, at windward and leeward positions on a measuring field. The three fractions of PM measurement are differently influenced by the increasing wind and shear velocities of the wind. The measured concentrations of the coarser fractions of the fine dust, PM10, and PM2.5, increase with wind and shear velocity, whereas the PM1.0 concentrations show no clear correlation to the shear velocity. The share of PM2.5 on PM10 depends on the measurement height and wind speed and varies between 4 and 12 m/s at the 1 m height ranging from 25% to 7% (average 10%), and at the 4 m height from 39% to 23% (average 30%). Although general relationships between wind speed, PM concentration, and horizontal and vertical fluxes could be found, the contribution of the measuring field was very low, as balances of incoming and outgoing fluxes show. Consequently, the measured PM concentrations are determined from a variety of sources, such as traffic on unpaved roads, cattle drives, tillage operations, and wind erosion, and thus, represent all components of land use and landscape structure in the near and far surroundings of the measuring field. The current results may reflect factors from the landscape scale rather than the influence of field-related variables. The measuring devices used to monitor PM concentrations showed differences of up to 20%, which led to considerable deviations when determining total balances. Differences up to 67% between the calculated fluxes prove the necessity of a previous calibration of the devices used. (c) 2022 International Research and Training Centre on Erosion and Sedimentation/the World Association for Sedimentation and Erosion Research. KW - PM10, PM2.5 and PM1.0 concentrations KW - Field measurements KW - Horizontal KW - flux KW - Vertical flux KW - PM balances Y1 - 2022 U6 - https://doi.org/10.1016/j.ijsrc.2022.01.004 SN - 1001-6279 SN - 2589-7284 VL - 37 IS - 5 SP - 539 EP - 552 PB - IRTCES CY - Beijing ER - TY - JOUR A1 - Lischeid, Gunnar A1 - Webber, Heidi A1 - Sommer, Michael A1 - Nendel, Claas A1 - Ewert, Frank T1 - Machine learning in crop yield modelling BT - A powerful tool, but no surrogate for science JF - Agricultural and forest meteorology N2 - Provisioning a sufficient stable source of food requires sound knowledge about current and upcoming threats to agricultural production. To that end machine learning approaches were used to identify the prevailing climatic and soil hydrological drivers of spatial and temporal yield variability of four crops, comprising 40 years yield data each from 351 counties in Germany. Effects of progress in agricultural management and breeding were subtracted from the data prior the machine learning modelling by fitting smooth non-linear trends to the 95th percentiles of observed yield data. An extensive feature selection approach was followed then to identify the most relevant predictors out of a large set of candidate predictors, comprising various soil and meteorological data. Particular emphasis was placed on studying the uniqueness of identified key predictors. Random Forest and Support Vector Machine models yielded similar although not identical results, capturing between 50% and 70% of the spatial and temporal variance of silage maize, winter barley, winter rapeseed and winter wheat yield. Equally good performance could be achieved with different sets of predictors. Thus identification of the most reliable models could not be based on the outcome of the model study only but required expert's judgement. Relationships between drivers and response often exhibited optimum curves, especially for summer air temperature and precipitation. In contrast, soil moisture clearly proved less relevant compared to meteorological drivers. In view of the expected climate change both excess precipitation and the excess heat effect deserve more attention in breeding as well as in crop modelling. KW - Crop modelling KW - Machine learning KW - Random forests KW - Support vector KW - machine KW - Feature selection KW - Equivocality Y1 - 2021 U6 - https://doi.org/10.1016/j.agrformet.2021.108698 SN - 0168-1923 SN - 1873-2240 VL - 312 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Funk, Roger A1 - Busse, Jaqueline A1 - Siegmund, Nicole A1 - Sommer, Michael A1 - Iturri, Laura Antonela A1 - Panebianco, Juan E. A1 - Avecilla, Fernando A1 - Buschiazzo, Daniel T1 - Phytoliths in particulate matter released by wind erosion on arable land in La Pampa, Argentina JF - Frontiers in environmental science N2 - Silicon (Si) is considered a beneficial element in plant nutrition, but its importance on ecosystems goes far beyond that. Various forms of silicon are found in soils, of which the phytogenic pool plays a decisive role due to its good availability. This Si returns to the soil through the decomposition of plant residues, where they then participate in the further cycle as biogenic amorphous silica (bASi) or so-called phytoliths. These have a high affinity for water, so that the water holding capacity and water availability of soils can be increased even by small amounts of ASi. Agricultural land is a considerable global dust source, and dust samples from arable land have shown in cloud formation experiments a several times higher ice nucleation activity than pure mineral dust. Here, particle sizes in the particulate matter fractions (PM) are important, which can travel long distances and reach high altitudes in the atmosphere. Based on this, the research question was whether phytoliths could be detected in PM samples from wind erosion events, what are the main particle sizes of phytoliths and whether an initial quantification was possible.Measurements of PM concentrations were carried out at a wind erosion measuring field in the province La Pampa, Argentina. PM were sampled during five erosion events with Environmental Dust Monitors (EDM). After counting and classifying all particles with diameters between 0.3 and 32 mu m in the EDMs, they are collected on filters. The filters were analyzed by Scanning Electron Microscopy and Energy Dispersive X-Ray analysis (SEM-EDX) to investigate single or ensembles of particles regarding composition and possible origins.The analyses showed up to 8.3 per cent being phytoliths in the emitted dust and up to 25 per cent of organic origin. Particles of organic origin are mostly in the coarse dust fraction, whereas phytoliths are predominately transported in the finer dust fractions. Since phytoliths are both an important source of Si as a plant nutrient and are also involved in soil C fixation, their losses from arable land via dust emissions should be considered and its specific influence on atmospheric processes should be studied in detail in the future. KW - dust KW - dust composition KW - particulate matter KW - scanning electron microscope KW - (SEM) analysis KW - phytolith Y1 - 2022 U6 - https://doi.org/10.3389/fenvs.2022.969898 SN - 2296-665X VL - 10 PB - Frontiers Media CY - Lausanne ER - TY - JOUR A1 - Iturri, Laura Antonela A1 - Funk, Roger A1 - Sommer, Michael A1 - Buschiazzo, Daniel T1 - Transport preferences of P forms in wind-blown sediments of two susceptible soils JF - Aeolian research : an international journal on wind erosion research / International Society of Aeolian Research N2 - Wind erosion of agricultural soils affects their stock of essential elements for plants, like phosphorus (P). It is known that the composition of the eroded sediments varies with height, according to the size and density of the transported substances. Aim of this study was to analyze the concentration and enrichment ratios of P forms in sediments transported by the wind. A wind-tunnel study was performed on a sandy-and a sandy loam soil in order to measure P forms concentrations in the saltating sediments. P concentrations were also measured in the particulate matter (PM) of each soil, gained with the Easy Dust Generator. In both soils, inorganic-(Pi) and organic P (Po) were preferentially transported in PM, with enrichment ratios of 1.8 and 5.5, respectively. Nevertheless, a Pi/Po of 0.9 indicated that the accumulation of the minor Po in PM was more pronounced than Pi. This agrees with P-rich light and easily erodible organic compounds, almost exclusively accumulated in PM, and in relatively heavy and less erodible minerals, like apatites, in lower height sediments. Labile P (Pl) was preferentially transported in saltating sediments of both soils. This was attributed to the selective Bray & Kurtz I's extraction of the abundant inorganic P forms of these sediments. Total P (Pt) copied the transport trends of Pi, the major form. According to the transporting trends, Pi and Po would be re-sedimented at longer distances from the source than Pl. Outcomes become useful for modeling the influence of wind erosion on P cycling. KW - Nutrient KW - Soil fertility KW - Wind erosion KW - Semiarid KW - Wind tunnel Y1 - 2022 U6 - https://doi.org/10.1016/j.aeolia.2022.100776 SN - 1875-9637 VL - 55 PB - Elsevier CY - Amsterdam [u.a.] ER -