Challenges in using mid-infrared spectroscopy for the determination of soil physical, chemical, and biochemical properties on undisturbed soil samples

Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy in the mid-infrared range (MIR) has become an established analytical tool for quantitative and qualitative analysis of soil samples. The heterogeneity of soil requires sample preparation procedures to optimize the reproducibility and accuracy of the spectroscopic measurement. These procedures have not been standardized. Generally, soil is dried and ground before measurement to avoid reflections of surface water films and minimize the intra- and inter-particle variability, respectively. Additionally, the sample surface is levelled to a plain surface for an ideal reflection. These sample preparation techniques are limited to disturbed samples only. Thus, a potential DRIFT mapping of undisturbed soil samples requires an adjusted calibration to allow for an accurate prediction of soil properties. In this study, we developed a method for calibrating the prediction of DRIFT spectra collected from undisturbed soil samples. In a first step, differences of spectral information measured from undisturbed and ground soil samples have been evaluated. Therefore, we record the DRIFT spectra of 120 German and 120 West-African chemically well characterized soils. DRIFT spectra of both, ground and sieved only soil samples are recorded and both calibrated against different physio-chemical soil properties, such as texture, CEC, organic carbon, pH, or iron oxides. In preliminary experiments, we found that spectra of sieved and ground samples significantly differed in specific spectral regions representing clay minerals, as well as organic matter. It can be assumed that the prediction of surface related soil parameters could be superior using sieved soil spectra, as grounding alters the surface structure of the soil. In a further step, microtopgraphy effects on spectra quality from disturbed and undisturbed soil samples have been evaluated. Therefore, spectral information has been taken from two dimensional disturbed and undisturbed soil samples at a high spatial resolution. The spectra quality was significantly higher in the disturbed soils since microtopography was absent in these samples. Thus, a digital elevation model (DEM) will be constructed using close-range digital photogrammetry to correct these topography effects. With this new method, there is a potential of imaging soil parameters on a microscale that can help considerably in locating and understanding soil processes on a small scale

Classification of West African (peri)-urban and rural agricultural soils based on mid-infrared diffuse reflectance spectroscopy (DRIFT) and multivariate statistics and data mining

Urban and peri-urban agriculture has long been part of West African society. In Sub-Sahara Africa with its low soil fertility and high vulnerability for droughts, food security not only depends on rural food production but also on this (peri)-urban agriculture. The interdisciplinary GlobE – UrbanFoodPlus project aims to enhance the resource use efficiency of such agricultural sites in West African cities to improve the economic situation and food security for the people in this area. To assess soil productivity inside this project, several randomized surveys were conducted to characterize urban and peri-urban agriculture in Tamale (Ghana), Ouagadougou (Burkina Faso), and in rural Northern Ghana. All sample sites were situated in the West African Savannah zone. These surveys systematically described the status of urban agriculture by collecting soil samples, as well as additional socioeconomic and land use data. For our study, the spectra of more than 1000 soil samples were analyzed using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy in the mid-infrared range (MIR 4000–400 cm–1) at a resolution of 4 cm-1. Based on the large data set of spectra, we exploratory analyzed the data for clustering and grouping based on latest improvements in multivariate statistics and data mining. Statistically, we were able to find classes inside the spectral data. This grouping could be explained by sample location using the Random Forest algorithm at a very low error of about 5%. By mathematical pretreatment of the data, the error could further be reduced to <2%. Due to the spectral difference by geography location, potential caused by differences in climate, we continued to determine groups within one location using cluster algorithms. With this technique, we could determine further subgroups in the data. We then used topographic, land use, and socioeconomic data to explain the statistically found clustering in the MIR spectra. We herewith present a novel approach by combing multivariate MIR spectra analysis with socioeconomic data. Although we showed that soil spectra seemed to be largely affected by topography and climate, there were also differences in the spectra that could be explained by differences in land use practices

Design and experimental verification of an improved magnetostrictive energy harvester

This paper summarizes and extends the modeling state of the art of magnetostrictive energy harvesters with a focus on the pick-up coil design. The harvester is a one-sided clamped galfenol unimorph loaded with two brass pieces each containing a permanent magnet to create a biased magnetic field. Measurements on different pick-up coils were conducted and compared with results from an analytic model. Resistance, mass and inductance were formulated and proved by measurements. Both the length for a constant number of turns and the number of turns for a constant coil length were also modeled and varied. The results confirm that the output voltage depends on the coil length for a constant number of turns and is higher for smaller coils. In contrast to a uniform magnetic field, the maximal output voltage is gained if the coil is placed not directly at but near the fixation. Two effects explain this behavior: Due to the permanent magnet next to the fixation, the magnetic force is higher and orientates the magnetic domains stronger. The clamping locally increases the stress and forces the magnetic domains to orientate, too. For that reason the material is stiffer and therefore the strain smaller. The tradeoff between a higher induced voltage in the coil and an increasing inductance and resistance for every additional turn are presented together with an experimental validation of the models. Based on the results guidelines are given to design an optimal coil which maximizes the output power for a given unimorph

Bent crystal spectrometer for both frequency and wavenumber resolved x-ray scattering at a seeded free-electron laser

We present a cylindrically curved GaAs x-ray spectrometer with energy resolution $\Delta E/E = 1.1\cdot 10^{-4}$ and wave-number resolution of $\Delta k/k = 3\cdot 10^{-3}$, allowing plasmon scattering at the resolution limits of the Linac Coherent Light Source (LCLS) x-ray free-electron laser. It spans scattering wavenumbers of 3.6 to $5.2/$\AA\ in 100 separate bins, with only 0.34\% wavenumber blurring. The dispersion of 0.418~eV/$13.5\,\mu$m agrees with predictions within 1.3\%. The reflection homogeneity over the entire wavenumber range was measured and used to normalize the amplitude of scattering spectra. The proposed spectrometer is superior to a mosaic HAPG spectrometer when the energy resolution needs to be comparable to the LCLS seeded bandwidth of 1~eV and a significant range of wavenumbers must be covered in one exposure

Vegetable production, consumption and its contribution to diets along the urban – rural continuum in Northern Ghana

Malnutrition continues to be a problem, with sub-Saharan Africa affected the worst. Women and children are at the pinnacle of this problem. The perpetual scourge of malnutrition in urban and periurban settings, coupled with levels of vegetable consumption below the recommended amounts, are a major problem in most African countries including West African cities. A household survey was conducted between November and December 2013 (dry season) in and around Tamale, Ghana as part of an urban food system analysis, to understand vegetable production and consumption and its contribution to household diets and income along the urban – rural continuum. Data collection was guided by a transect approach. A total of 240 households participated in the survey, with 62% males and 38% females. Additionally, 186 women of reproductive age (15 – 49 years) staying in the sampled households contributed to the computing of household dietary diversity through Women’s Dietary Diversity Scores (WDDS). Most vegetables produced were for subsistence use, considering that most households sold less than 50% of the crops and consumed the rest. Vegetable production varied significantly along the urban - rural continuum, with more households in rural areas producing all the requirements of their vegetables compared to urban and periurban areas. Nevertheless, the households in the rural areas (16%) had the lowest dietary diversity (≤ 3 WDDS) compared to urban areas (13%) and periurban areas (5%). The study showed low consumption of vegetables (especially the dark green vegetables) mostly in the rural area and limited diversity of vegetables, especially vitamin A rich vegetables and tubers, with only three vegetables (carrots, red pepper and sweet potato) consumed. There was evidence of more inclination toward staple crops compared to vegetables along the urban – rural continuum for both production and consumption, clearly shown in crops grown and food groups mostly consumed (cereals and tubers rather than dark green vegetables). There was overall low consumption of dark green leafy vegetables, such as amaranth, with only 26% reported to have consumed them during the reported period compared to food groups like cereals (98%). This study confirms the dual purpose of vegetables in complementing dishes (balanced diets) with much needed micronutrients and helping households along the urban – rural continuum to generate income.Keywords: Vegetables, dietary diversity, food groups, urban – rural continuum, Northern Ghan

Changes in bulk and surface properties of two biochar types during 12 months of field ageing in two West-African soils

The study investigated the changes in properties of rice husk and corn cob biochars applied in urban agricultural field soils in Tamale (northern Ghana) and Ouagadougou (Burkina Faso), respectively. The biochars were both pyrolyzed at 500 °C with a batch reactor. Fine polyethylene mesh (litter bags) filled with 10 g of each type of biochar were buried at 20 cm depth in urban fields trials with a 3 x 2 factorial layout replicated 4 times. Factor 1 involved soil management practices at 3 levels: (1) farmers’ practice (FP), (2) 20 t biochar ha-1 and (3) control (no biochar). The second factor was time (duration) at two levels (6 and 12 months). Aged and fresh biochars were analyzed for volatile matter (VM), ash and fixed carbon (FC) contents, pH, effective cation exchange capacity (ECEC), and total surface acidity (Sa) and basicity (Sb). Dissolved organic carbon contents were determined sequentially by cold (cDOC) and hot water extractions (hDOC), respectively and aromaticities of cold water DOC (cSUVA) and hot water DOC (hSUVA) were determined. There was no significant interaction effect of soil management practices and time on measured ageing biochar properties. Time significantly affected most biochar ageing properties except Sa and Sb in rice husk biochar and ECEC in corn cob biochars at 6 months of exposure. In both biochars, Ash content, Fixed carbon (FC), cDOC, hDOC, cSUVA and hSUVA increased whilst pH and volatile matter contents decreased significantly. The hDOC was 2-3 times higher than cDOC contents for both biochars. Aromaticity of DOC contents of aged rice husk biochar exposed to soil management practices and time in the experimental site in Tamale showed persistence with time compared to corn cob biochar exposed in Ouagadougou experimental site. The results imply that rainfall, soil organic matter contents with interplay of soil minerals are key drivers to ageing and sequestration of these biochars and that these forces act at different scales but driven by time

Produktkennzeichnungen als Kommunikations- und Informationsmedium für Bodenschutz - eine Analyse von Zertifizierungssystemen auf dem deutschen Markt

Die Vermittlung von Informationen über die Notwendigkeit, unsere Böden und deren Funktionen zu schützen, stellt eine zentrale Voraussetzung für die Erhöhung des Bodenbewusstseins in der Bevölkerung dar. Als Kommunikations- und Informationsmedium verfügen Produktkennzeichnungen über ein vielversprechendes Potential, bodenschutzrelevante Informationen in Verbindung mit produktspezifischen Eigenschaften an die Verbraucher zu vermitteln. Derzeit existiert eine Vielzahl an Kennzeichnungen auf dem deutschen Markt, die Konsumenten über nicht sichtbare Produkteigenschaften informieren. Sie werden in Form von Logos, Symbolen und Texten direkt am Produkt oder auf der Verpackung angebracht und dienen u. a. der Kennzeichnung von Produkten, die klimafreundlich und ressourcensparend sind, zum Erhalt von Ökosystemen, Tier- und Pflanzenarten beitragen sowie den Schutz von Gewässern, Atmosphäre und Böden fördern. Verbraucher erhalten hierdurch Informationen zur Identifikation von umweltfreundlichen Produkten, die sowohl zum Umweltschutz als auch zur Reduktion negativer Umweltauswirkungen beitragen. Im Zuge einer umfassenden Analyse wurde der Fragestellung nachgegangen, in welchem Umfang bestehende Produktkennzeichnungen auf dem deutschen Markt den Schutz von Böden berücksichtigen und den Verbraucher hierüber informieren. Zu diesem Zweck wurden die Vergabekriterien, die Kommunikationswege und die dem Verbraucher zur Verfügung gestellten Informationen von über 550 Produktkennzeichnungen untersucht. Eine Analyse der mithilfe dieser Zertifizierungssysteme vermittelten bodenschutzbezogenen Informationen ist im Hinblick auf ihre inhaltliche Aufbereitung sowie grafische und textliche Gestaltung ebenfalls Gegenstand der durchgeführten Untersuchung gewesen. Als Ergebnis wurden rund 100 Produktkennzeichnungen identifiziert, die in ihren Vergabekriterien unterschiedliche Aspekte des Bodenschutzes berücksichtigen, wohingegen nur wenige diese Informationen auch an die Konsumenten weitergeben. Unter ihnen befinden sich hauptsächlich Kennzeichnungen für Produkte, die einen direkten Bezug zur Thematik aufweisen und zu Produktgruppen aus der Forst- und Landwirtschaft sowie dem Gartenbau und dem Baugewerbe gehören. Zudem wurde festgestellt, dass in Abhängigkeit von der betrachteten Produktgruppe die Aufbereitung der an die Verbraucher übermittelten bodenschutzbezogenen Informationen sowie deren textliche und grafische Gestaltung in erheblichem Maße voneinander variieren

Ist der Kohlenstoffabbau in Unterböden limitiert auf Hotspots? - Räumliche Erfassung des Substratabbaus und der Enzymaktivitäten mittels Radiographie und Zymographie

Durch die größere Relevanz von präferentiellen Fließwegen und Wurzeln für den Kohlenstoffinput in den Unterboden (< 30 cm) ergibt sich eine höhere räumliche Heterogenität der Kohlenstoffverteilung und -flüsse als im Oberboden. Eine mögliche räumliche Segregation zwischen Konsumenten und Kohlenstoff im Unterboden ist eine Theorie, weshalb der dortige Kohlenstoff nur langsam abgebaut wird. Dies lässt vermuten, dass im Unterboden der Kohlenstoffumsatz hauptsächlich in mikrobiellen „Hot Spots“ stattfindet. Bisherige methodische Ansätze können diese Theorie nicht untersuchen, da z.B. bei Substratmineralisierungsstudien nur gestörte Proben verwendet werden können. Die Kombination aus Radiographie und Zymographie kann ein neuer Ansatz sein, um die räumliche Aktivität von Enzymen und den Abbau von C14-markierten Substraten an ungestörten (Unter)Bodenproben zu untersuchen. An der Probe (11 x 7 cm) wird zunächst die räumliche Aktivität von Enzymen aus verschieden Nährstoffkreisläufen mittels Zymographie (1) erfasst. Anschließend wird die Bodenoberfläche mit einem C14-markierten Substrat (z.B. Glukose) besprüht (100 Bq cm-2). Hierfür wird ein hochpräziser Sprühroboter (iMatrix Spray) verwendet, der ein sehr kleines Volumen von 1 µl cm-2 auf die Probe bringt. Die Probe wird für 2 Wochen inkubiert und das mineralisierte C14 in einer KOH-Lösung gefangen und nach ausgesuchten Zeiträumen mittels b-Counter analysiert. Der räumliche Abbau des Substrats wird zu denselben Zeitpunkten mit Hilfe der Radiographie (Bestimmung der Verteilung der Radioaktivität) erfasst. Die Kombination der zwei verschiedenen Methoden wird zeigen, ob das Substrat hauptsächlich in den mikrobiellen „Hot Spots“ abgebaut wird. Nach Beendigung der Inkubation wird die Zymographie wiederholt, um zu untersuchen, ob durch die C-Zugabe neue „Hotspots“ im Laufe der Inkubation entstanden sind. Dieser Beitrag wird die ersten Ergebnisse für Oberboden vs. Unterboden behandeln