Katja Wiedner | Martin Luther University Halle-Wittenberg (original) (raw)

Papers by Katja Wiedner

Journal of Agricultural and Food Chemistry, 2015

Biochar composting experiments were performed to determine whether composting is a suitable metho... more Biochar composting experiments were performed to determine whether composting is a suitable method to accelerate biochar surface oxidation. To assess the results, surface properties of Terra Preta (Brazil) and ancient charcoal pit (Northern Italy) biochars were additionally investigated. Calculation of O/C ratios by energy-dispersive X-ray spectroscopy demonstrated the anticipated increasing values from fresh biochars (0.13) to composted biochars (0.40), and finally charcoal pit biochars (0.54) and ancient Terra Preta biochars (0.64). By means of Fourier transformation infrared microscopy, creation of carboxylic and phenolic groups on biochars surface could be detected. Carboxylic acids of three composted biochars increased up to 14%, whereas one composted biochar showed a 21% lower proportion of carboxylic acids compared to the corresponding fresh biochar. Phenolic groups increased by 23% for the last mentioned biochar, and on all other biochars phenolic groups decreased up to 22%. Results showed that biochar surface oxidation can be accelerated through composting but still far away from ancient biochars.

Die fruchtbaren, bis über 2000 Jahre alten anthropogenen Schwarzerden (Terra Preta de Índio) im t... more Die fruchtbaren, bis über 2000 Jahre alten anthropogenen Schwarzerden (Terra Preta de Índio) im tropischen Amazonas Gebiet (Brasilien), dienen als Vorbild u.a. für die nachhaltige landwirtschaftliche Nutzung von Böden und der Schließung regionaler Stoffkreisläufe. Weltweit sind zahlreiche derartige Böden mit hohem Anteil an pyrogenem Kohlenstoff dokumentiert, jedoch hinsichtlich ihrer Genese kaum untersucht. Die wissenschaftliche Einordung und Untersuchung, dieser in verschiedenen Klimazonen vorkommenden Böden ist jedoch essentiell, um langfristige Veränderungen in Boden und Umwelt durch den Einsatz von moderner Pflanzenkohle besser abschätzen zu können. Der Fund eines tiefschwarzen Bodens (Nordic Dark Earth) während einer archäologischen Ausgrabung in den Überesten einer etwa 1000 Jahre alten slawischen Siedlung in Brünkendorf (Wendland Region), stellt ein beeindruckendes Beispiel anthropogener Bodenbildung im gemäßigten Klima dar. Die Wendlandregion ist aufgrund ihrer geologischen...

The demand of biochars (and hydrochars) as a soil amendment and for carbon sequestration is risin... more The demand of biochars (and hydrochars) as a soil amendment and for carbon sequestration is rising and industrial scale production develops rapidly. To ensure environmental friendly production conditions, the use of organic waste material as feedstocks and characterization of end products in terms of composition as well as pollution risk is needed. The aim of our study was to evaluate carbonized end products of five companies in Europe using three different production technologies (pyrolysis, gasification and hydrothermal carbonization) at industrial scale. We characterized elemental and bulk chemical composition (13C NMR), combined scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) and contribution of specific compounds such as black carbon (BC). In addition, polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were determined for risk assessment of biochars and hydrochars from large...

Das Einzugsgebiet der Unteren Mittelelbe und ist geprägt von nährstoff- und humusarmen, sandigen ... more Das Einzugsgebiet der Unteren Mittelelbe und ist geprägt von nährstoff- und humusarmen, sandigen Böden. Umso interessanter ist der Fund einer etwa 1,5 ha großen Fläche, die ungewöhnlich tiefschwarze Böden aufweist und daher in starkem Kontrast zu den umliegenden Böden steht. Die Böden befinden sich im Bereich einer slawischen Siedlung nahe Brünkendorf die auf das 10. Jh. n. Chr. vermutet wird. Im Vergleich zu einem umliegenden Referenzprofil, liegt der organische Kohlenstoffgehalt (Corg) bei durchschnittlich 1,38% anstatt der nur durchschnittlichen 0,40%. In den humusangereicherten Horizonten wurden immer wieder Holzkohlereste gefunden, was ein möglicher Grund für ein erhöhtes C/N Verhältnis von bis zu 19 sein kann. Der Anteil an pflanzenverfügbarem Phosphat liegt mit 27 mg kg-1 deutlich über dem der angrenzenden Böden mit durchschnittlich 16 mg kg-1. Pseudo-total Konzentrationen der Elemente P, Fe, Na, Ca, Ba, Cu und Zn zeigen im Vergleich zum Referenzprofil erhöhte Werte auf. Beso...

In recent years, soils rich in pyrogenic carbonaceous material (PCM) have become increasingly the... more In recent years, soils rich in pyrogenic carbonaceous material (PCM) have become increasingly the subject of scientifi c and public interest as biochar application to soil is a possible way to improve soil properties and sustainable management of natural resources (Glaser et al, 2000; Glaser et al, 2002; Lehmann et al, 2003). The use of biochar as a PCM added to soil has been commonplace in many parts of the world for centuries and even millennia. The aim of this chapter is to synthesize available knowledge and data on the historical use of biochar. Biochar plays a prominent role, leaving behind sustainable fertile black earth-like soils such as the famous Amazonian Dark Earths or Terra Preta de Indio(Glaser et al, 2001). The chapter focuses mainly on the historic use of biochar and identifies its specific role in sustainable agriculture. The term ‘biochar’ is a modern creation often used along with charcoal, pyrogenic C or black C, but not fully interchangeably or synonymous (Chapt...

Journal of Agricultural and Food Chemistry, 2015

Agronomy for Sustainable Development, 2014

Biochars are new, carbon-rich materials that could sequester carbon in soils improve soil propert... more Biochars are new, carbon-rich materials that could sequester carbon in soils improve soil properties and agronomic performance, inspired by investigations of Terra Preta in Amazonia. However, recent studies showed contrasting performance of biochar. In most studies, only pure biochar was used in tropical environments. Actually, there is little knowledge on the performance of biochar in combination with fertilizers under temperate climate. Therefore, we conducted an experiment under field conditions on a sandy Cambisol near Gorleben in Northern Germany. Ten different treatments were established in 72-m 2 plots and fivefold field replicates. Treatments included mineral fertilizer, biogas digestate, microbially inoculated biogas digestate and compost either alone or in combination with 1 to 40 Mg ha −1 of biochar. Soil samples were taken after fertilizer application and maize harvest. Our results show that the biochar addition of 1 Mg ha −1 to mineral fertilizer increased maize yield by 20 %, and biochar addition to biogas digestate increased maize yield by 30 % in comparison to the corresponding fertilizers without biochar. The addition of 10 Mg ha −1 biochar to compost increased maize yield by 26 % compared to pure compost. The addition of 40 Mg ha −1 biochar to biogas digestate increased maize yield by 42 % but reduced maize yield by 50 % when biogas digestate was fermented together with biochar.

Biochar and Soil Biota, 2013

Organic Geochemistry, 2014

ABSTRACT The addition of biomass-derived black carbon or biochar to agricultural soils is attract... more ABSTRACT The addition of biomass-derived black carbon or biochar to agricultural soils is attracting attention as a means for sequestering carbon and as a potentially valuable method for improving soil fertility. Recent research has shown, however, that biochar is not completely unreactive in soils as it potentially enhances microbial activity, adsorption of organic contaminants or release of polycyclic aromatic compounds, which may ultimately affect the composition of dissolved organic matter (DOM) leaching from a soil. We have tested this hypothesis using batch and soil column experiments. Addition of fresh biochar (1 wt. %) to a Gleyic Fluvisol resulted in a 22% reduction in OM mobilization from the soil. Ultrahigh resolution mass spectrometry revealed a marked change in the composition of the OM mobilized. The most saturated and reduced compounds were removed in the solutions leached from the biochar amended soil. On the other hand, while dissolved black carbon-type compounds were already leaching from the un-amended soil, their abundance increased after biochar amendment. We also detected newly-appeared “lignin-type” compounds with relatively high O/C ratio of ca. 0.65, indicating that non-black carbon was also leached from the amended soil and was highly oxygenated DOM. During a flow interruption of 1 week the soil columns turned anoxic. The DOM mobilized after flow interruption was mostly identical to that mobilized under oxic conditions, with the exception of aromatic and polycyclic aromatic compounds being more abundant. These were probably associated with Fe and Mn oxides and released during the reductive dissolution of the oxides. In summary, the biochar amendment changed the molecular composition of soil-derived DOM. The net effect was (i) a reduction in total OC mobilization and (ii) a shift towards more oxidized and therefore less bioavailable OM that was leached to the subsoil.

Organic Geochemistry, 2013

Field application of biochar is intended to increase soil carbon (C) storage. The assessment of C... more Field application of biochar is intended to increase soil carbon (C) storage. The assessment of C storage potential of biochars lacks methods and standard materials. The reactivity of biochars and hydrochars may be one possible means of evaluating their environmental stability. The aim of this study was to evaluate the reactivity of biochar produced by gasification (GS) and hydrochar produced by hydrothermal carbonisation (HTC). The approach included analysis of the two different char types produced from the same three feedstocks. Moreover, we analysed the reactivity of Holocene charcoal (150 and 2000 yr old) to evaluate whether or not their use as standard materials to represent stable biochar is meaningful. We assessed carbon loss following oxidation with acid dichromate as well as hydrolysis with HCl. Our results showed that chemical reactivity is not a straightforward approach for characterising the stability of biochar and hydrochar. Acid hydrolysis showed little difference between HTCs and GSs, despite the contrasting elemental composition. Using acid dichromate oxidation, we determined that GSs contained ca. 70% of oxidation resistant C while the proportion for HTCs was < 10%. The different feedstocks had a slight, but significant, influence on the reactivity of GSs and HTCs. The content of oxidation resistant C decreased in the order 100 yr old charcoal = GSs > 2000 yr old charcoal > HTCs > feedstock and was related to elemental composition. This shows that acid dichromate oxidation may allow differentiation of the reactivity of modern biochars but that there is not necessarily a relationship between reactivity and age of Holocene charcoals. As the chemical reactivity of biochars may change with exposure time in soil, it is poorly suited for assessing their environmental residence time.

Organic Geochemistry, 2013

Hydrothermal carbonization (HTC) of biomass may be a suitable technique to increase its carbon se... more Hydrothermal carbonization (HTC) of biomass may be a suitable technique to increase its carbon sequestration potential when applied to soils. However, the properties of end products of HTC (hydrochars) could be significantly influenced by feedstock source and temperature during the carbonization process. This study focused on chemical modification of wheat straw, poplar wood and olive residues through HTC at different temperatures (180°C, 210°C and 230°C). Besides general properties such as pH, electrical conductivity (EC), ash content, elemental composition and yield, we evaluated bulk chemical composition ( 13 C NMR) and contribution of specific compounds (lignin and black carbon). Moreover, the possible environmental risk of using hydrochars was assessed by determining their polycyclic aromatic hydrocarbon (PAH) and their dioxin contents. Our results showed that hydrochars were generally acidic with a pH value below 5. The highest EC (1710 lS/cm) and ash content (10.9%) were found in wheat straw derived hydrochars. Hydrochar yields and C recovery decreased with increasing temperature to about 50% and 75%, respectively for all feedstocks at 230°C. N recovery increased with increasing temperature but N content of feedstock is more important. H/C and O/C ratios showed a linear decrease with increasing production temperature for all feedstocks. O-alkyl C decreased while alkyl C and aromatic C increased with increasing temperature and no significant feedstock dependence could be observed. Carboxyl C was not influenced by feedstock and temperature. Lignin content decreased with increasing temperature, while its oxidation degree and the content of black carbon and PAH contents increased. We conclude that transformation of biomass was most advanced at 230°C only. Feedstock did not significantly influence the chemical composition of the hydrochars apart from N content and recovery. Instead, HTC temperature is the main driver determining the chemical composition of hydrochars. Environmental risk of investigated hydrochars is low with respect to PAH and dioxin contents. Despite the advanced biomass transformation during the HTC process at 230°C, chemical properties indicated that the end product might have a less stable structure than pyrochar. Considering the higher hydrochar yields and C and N recoveries, its C and N sequestration potential in soil could have some advantages over hydrochars but this still remains to be evaluated.

Biomass and Bioenergy, 2013

Gasification 13 C NMR Black carbon Polycyclic aromatic hydrocarbons a b s t r a c t Technologies ... more Gasification 13 C NMR Black carbon Polycyclic aromatic hydrocarbons a b s t r a c t Technologies for agro-industrial feedstock utilization such as pyrolysis, gasification and hydrothermal carbonization at industrial scale develop rapidly. The thermochemically converted biomasses of these production technologies have fundamentally different

During an archaeological excavation of a Slavic settlement (10th/11th C. A.D.) in Brünkendorf (We... more During an archaeological excavation of a Slavic settlement (10th/11th C. A.D.) in Brünkendorf (Wendland region in Northern Germany), a thick black soil (Nordic Dark Earth) was discovered that resembled the famous terra preta phenomenon. For the humid tropics, terra preta could act as model for sustainable agricultural practices and for long-term CO2-sequestration into terrestrial ecosystems. The question was whether this Nordic Dark Earth had similar properties and genesis as the famous AmazonianDark Earth in order to find amodel for sustainable agricultural practices and long term CO2-sequestration in temperate zones. For this purpose, a multianalytical approach was used to characterise the sandy-textured Nordic Dark Earth in comparison to less anthropogenically influenced soils in the adjacent area in respect of ecological conditions (pH, electric conductivity, cation exchange capacity, amino sugar) and input materials. Total element contents (C, N, P, Ca, Mg, K, Na, Fe, Cu, K, Zn, Mn and Ba) were highly enriched in the Nordic Dark Earth compared to the reference soil. Faecal biomarkers
such as stanols and bile acids indicated animalmanure from omnivores and herbivores but also human excrements. Amino sugar analyses showed that Nordic Dark Earth contained higher amounts of microbial residues being dominated by soil fungi. Black carbon content of about 30 Mg ha−1 in the Nordic Dark Earth was about four times higher compared to the adjacent soil and in the same order of magnitude compared to terra preta.
The input materials and resulting soil chemical characteristics of theNordic Dark Earth were comparable to those of Amazonian Dark Earth suggesting that their genesis was also comparable. Amazonian Dark Earth and Nordic Dark Earth were created by surface deposition and/or shallow soil incorporation of waste materials including human and animal excrements together with charred organic matter. Over time, soil organisms degraded and metabolized these materials leaving behind deep black stable soil organic matter. The existence of the Nordic Dark Earth in the temperature zone of Europe demonstrates the capability of sandy-textured soils to maintain high soil organicmatter contents and nutrient retention over hundreds of years. Deeper insights are needed urgently to understand soil organic matter stabilization mechanisms in this sandy soil to promote conceptual models for sustainable land use and long-term C sequestration.
It is argued that the knowledge of Nordic Dark Earth probablywas an important part of the Viking–Slavic subsistence agriculture system, which could have had a great impact on the development of the Viking age emporia in
the 9th/10th C. A.D.

Conference Presentations by Katja Wiedner

Cultural layers of medieval settlements are often characterised by a considerable thickness and d... more Cultural layers of medieval settlements are often characterised by a considerable thickness and deep black colour, even if the subsoil is sandy and nutrient-poor. During archaeological excavations of a Slavic settlement (10th/11th c. A.D.) near the river Elbe in Brünkendorf (Northern Germany), a thick black cultural layer was uncovered and scientifically investigated by a multianalytical approach. Faecal biomarkers such as stanols and bile acids indicated animal manure from omnivores and herbivores but also human excrements. Striking was the unusual high content of black carbon. The input materials and resulting soil chemical characteristics were comparable to those of Amazonian Dark Earth suggesting that their genesis was also comparable. This gave the reason for naming the investigated soil „Nordic Dark Earth“. The existence of the Nordic Dark Earth in the temperate zone of Europe demonstrates the capability of sandy-textured soils to maintain high soil organic matter contents and nutrient retention over hundreds of years. Furthermore, the extraordinary high fertility of the Nordic Dark Earth allows the development of new models for agricultural practices. The later is of special importance in the forest zone of Eastern Europe, where suitable areas and soils for farming remain rather limited. Corresponding to empirical studies such soil types developed mainly from the 9th to 11th c. AD in the territories of the Western and Eastern Slavs as well as in some Viking Age trading sites in the Baltic Sea region. We suggest that Nordic Dark Earth was an important part of the Viking-Slavic agriculture system in the forest zone. In the 9th/10th c. A.D. especially the Eastern trading sites of the Vikings (the so called emporia) flourished as early urban settlements, before economic system changed at the turn of the 1st to the 2nd millennia AD. We cannot exclude that the Nordic Dark Earth could have had a great impact on the development of the Viking age emporia in that time. High yields from relatively small areas allowed to provide many people in a limited space with food. Within the scope of the presentation we will show further examples from Russia, Belarus und Poland which suggests that other subsistence strategies than previously thought were persued during the Viking age.

Journal of Agricultural and Food Chemistry, 2015

Agronomy for Sustainable Development, 2014

Biochar and Soil Biota, 2013

Organic Geochemistry, 2014

Organic Geochemistry, 2013

Biomass and Bioenergy, 2013

Wölbäcker sind als Zeugnisse des historischen Ackerbaus in Mitteleuropa weiträumig verbreitet und... more Wölbäcker sind als Zeugnisse des historischen Ackerbaus in Mitteleuropa weiträumig verbreitet und zumeist unter heute bewaldeten Gebieten erhalten geblieben. Die bis zu 17 Meter breiten und parallel zueinander laufenden Wölbackerstreifen sind charakterisiert durch eine bis zu 1 m hohe Wölbung mit einer Länge von mehreren hundert Metern. Das von der DFG geförderte Projekt zur „Entstehung und Nutzung von Wölbäckern in Sachsen-Anhalt“ beschäftigt sich mit kontrovers
diskutierten Fragen u. a. hinsichtlich der Entstehung, Funktion und Bewirtschaftung der Ackerfluren. Dazu kommen modernste, multianalytische Methoden (u.a. stabile Isotope und Biomarker)
kombiniert mit der Auswertung historischer Quellen zum Einsatz.
Im Rahmen der im vergangenen Sommer 2017 durchgeführten Feldkampagne wurde jeweils ein Schnitt durch 12 Wölbäcker an ausgewählten Standorten im Harz und in der Altmark angelegt. Der
Querschnitt einiger Wölbäcker zeigt, dass die manifestierte Meinung, Wölbungen seien ausschließlich durch schollenwendende Pflüge entstanden, falsifiziert werden kann. Auch bisher kaum beachtete historische Quellen weisen darauf hin. Die langjährige Bodenbearbeitung aber auch der Eintrag an organischem Material (z.B. Dung) hat(te) Auswirkungen auf bodenbildende Prozesse. Zudem ist davon auszugehen, dass die unterschiedlichen Charakteristika der Standorte die Form und Nutzung der Wölbäcker stark prägten. Erste Laborergebnisse zeigen, dass sich die δ15N, P und C Werte nicht nur aufgrund natürlicher Gegebenheiten stark voneinander unterscheiden. Inwieweit z.B. der Eintrag von Fäkalien bei stark P angereicherten Standorten eine Rolle bei der Urbarmachung der v.a. in der Altmark sehr sandigen und nährstoffarmen Böden eine Rolle gespielt haben könnte, ist auch Gegenstand des Projekts. Auch das Alter der Wölbäcker ist Grundlage für kontroverse Diskussionen. Erste Ergebnisse von OSL
Datierungen in der Altmark deuten auf einen wesentlich früheren Beginn (1060±70 AD) der Wölbackerkultur hin als bisher angenommen. Datierungen (OSL und 14C) an weiteren Standorten sind
aktuell unter Bearbeitung.
Der Vortrag zur Wölbackerkultur in Sachsen-Anhalt bündelt die ersten Gelände- und Laborergebnisse, welche zeigen, dass die bisherige Theorie nur in Teilen haltbar ist und neu überdacht werden muss.