The excessive and often unregulated use of antibiotics in livestock production and human health has led to the dissemination of antibiotic residues and antibiotic resistance genes (ARGs) posing a serious threat to the environment and public health. This study investigates the co-occurrence and spatial distribution of antibiotic residues and ARGs in livestock manure and agricultural soils from Machakos, Kiambu, and Kajiado counties in Kenya, regions characterized by intensive livestock farming. A total of 180 animal manure and soil samples from 30 farms across the three counties were collected and pooled into 18 samples. Antibiotic residues were extracted and quantified using high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Nine ARGs (aadA, ermB, sul1, tetQ, tetW, dfrA1, blaMOX, blaOXA and qnrB were quantified via absolute and relative qPCR, normalized to 16S rRNA gene copy numbers. Multivariate analyses, including PCoA and Spearman Correlation, were conducted to explore ARG structure and co-occurrence. Tetracycline, particularly oxytetracycline, was the most abundant antibiotic in manure (up to 1150 ng mL-1), especially in pig manure from Kiambu. Sulfadimethoxine was undetectable in nearly all samples except in soil mixed with pig manure from Kajiado county, which showed a concentration above 70 ng mL-1, the pig manure from the same county had levels below 2 ng mL-1. Sulfadimidine, sulfamethoxanole and erythromycin were not detected in any of the samples. A three-way ANOVA showed that animal source (cattle, pigs, poultry) and sample type (manure, soil) were generally not significant factors for antibiotic concentration. Only oxytetracycline (P = 0.0421, 0.0901) and sulfadimethoxine (P = 0.0904, 0.044, 0.054) showed marginal significance by sample type (P = 0.0785). Antibiotic resistance genes were widely distributed, with aadA, ermB and sul1 being the most prevalent, especially in soils from Kiambu and Machakos. The tetQ showed extremely high relative abundance, indicating intense selection pressure from tetracyclines. Strong positive correlations were observed between co-occurring ARGs, including tetQ and tetW as well as erm and sul1. The concurrent detection of persistent antibiotic residues and high ARG loads in both manure and soils underscores the urgent need for improved antibiotic stewardship, sustainable manure management, and environmental monitoring in Kenyan agroecosystems.

ZusammenfassungViele Regelungsfunktionen von Böden (Kap. 10.1) beruhen auf biogeochemischen Prozessen und werden deshalb von den chemischen Eigenschaften der Böden beeinflusst. Beispiele hierfür sind die Speicherung und Nachlieferung von Nährstoffen, die Sorption und der Abbau von Schadstoffen sowie die Pufferung von Säureeinträgen. Chemische Prozesse an Grenzflächen sind dabei von herausragender Bedeutung. Etwa 40…60 % des Bodenvolumens bestehen aus Poren, die je nach aktueller Bodenfeuchte mit Wasser (Bodenlösung) und Gasen (Bodenluft) gefüllt sein können. Die feste Bodensubstanz besteht überwiegend aus Mineralen und kleineren Anteilen von organischen Substanzen. In diesem porösen System aus mineralischen und organischen Bodenpartikeln, Gasen, wässrigen Lösungen und Organismen bilden sich enorm große und chemisch reaktive Grenzflächen aus. An diesen Grenzflächen können Ionen und Moleküle adsorbiert, komplexiert, ausgefällt oder chemisch umgewandelt werden.

Böden sind Naturkörper und als solche durch jeweils typische physikalische Eigenschaften gekennzeichnet; Farbe (Kap. 6.8) und Körnung (Kap. 6.1) fallen am meisten ins Auge. Sie sind daher wichtige Bestandteile einer jeden Bodenbeschreibung.

Climate change-driven disturbances of forest ecosystems such as bark beetle infestations have been counteracted with salvage logging resulting in vast clear cuts. During these operations, commonly used heavy machinery causes irreversible degradation of forest soils. Thus, traffic has been restricted to skid trails. However, the emerging trend of mechanizing manual work leads to an increasing application of remote-controlled mini forestry crawlers (MFC) on undisturbed forest soils. We present the first study simulating the initial traffic effects on soil physical properties and functions of a Cambisol caused by a light-weight, rubber tracked MFC, with and without using a portable matting system (PMS) for soil protection at unfavorable soil moisture content. Our data document that successive passes without PMS significantly intensify soil structural damage and cause deep reaching compaction. Even a PMS does not completely protect against negative effects on soil physical properties and functions. However, after five passes over the PMS, these effects corresponded to those of a single pass without PMS, but even 10 passes with PMS use did not lead to further soil degradation. Steering maneuvers caused the most intense soil compaction and deformation. The induced shear forces and machine vibrations could provoke a loosening of the topsoil and the formation of macropore-like crack structures. These structures will most likely increase the aeration and hydraulic conductivity of the damaged soil, but should not be misinterpreted as soil improvement. Hence, MFC traffic on undisturbed, moist forest soil should be avoided and cannot be recommended without using a PMS.

Iron is a critical micronutrient for organisms in ecosystems globally and plays a crucial role in (co)limiting the biogeochemical cycles of other essential elements. Large uncertainties exist regarding the processes that govern the terrestrial production of bioavailable Fe in the fjord zone of the southernmost Patagonian Andes. We therefore investigated the Fe-cycling in alternately saturated peaty Andosols by analyzing the organic and inorganic geochemical composition of rhyolitic tephra, soil horizons as well as leachates and soil-tephra substrates. In batch experiments, changing redox conditions simulated the influence of rainfall-induced water-level fluctuations on weekly to seasonal time scales. Our data demonstrate that successive biotic-abiotic dissolution(re)crystallization processes predominantly form Fe-compounds, which are typically considered bio-accessible. These comprise dissolved Fe and metastable, organic matter (OM)-associated Fe-phases that are leached or (trans)formed from tephra and Fe-(hydr)oxides. Under oscillating redox, this biogeochemical cycling is primarily driven by intense OM turnover and microbial activity, constantly producing solutes that contain essential elements, which are either dissolved or exist as colloidal OM complexes. Under the variable hyper-humid climate, the composition of Andosol-sourced solutes varies seasonally, providing similar to 80 % of the annually released Fe during austral winter. At the land-fjord interface in this region, the Andosol-sourced Fe flux should considerably surpass that from glacial meltwaters and last several thousand years. Therefore, we consider volcanic ash deposits and the soils derived from it as the prevailing contributor of bioavailable Fe for the primary producers in the fjords of one of the most pristine ecosystems worldwide.

Die Stellung der Böden im Stoffkreislauf der Lithosphäre (Abb. 2.1-1) zeigt, dass an der Gesteinsbildung, der Lithogenese, eine große Zahl von Prozessen in Form eines Kreislaufs beteiligt sind. Beim Abkühlen glutflüssigen Magmas entstehen am Beginn der Lithogenese Gesteine durch Kristallisation aus der Schmelze. Sie unterliegen weiteren vielfältigen Veränderungen durch die Prozesse Verwitterung, Abtragung, Transport, Ablagerung, Diagenese, Metamorphose und Anatexis, die sich zu einem Kreislauf zusammenschließen. In diesem Kreislauf sind die Böden eine bedeutsame Station. Sie sind einerseits das Ergebnis der Gesteinsumwandlung in Kontakt mit Atmosphäre und Biosphäre (Pedogenese) und liefern andererseits Material für die Bildung neuer Gesteine. Daher sind Böden nicht ohne Gesteinskenntnis zu verstehen und zu klassifizieren, ebenso wenig aber auch viele Gesteine nicht ohne Kenntnis der Böden (Kittrick 1985).

Alle Böden unserer Erde sind nützlich. Sie dienen dem Naturhaushalt, der Pflanzen- und Tierproduktion oder vielfältigen Zwecken der Zivilisation (vgl. Kap. 1.2). Je größer die Bevölkerung unserer Erde wird, desto mehr konkurrieren verschiedene Nutzungen um ein und denselben Boden. Deshalb wird häufiger die Grundfrage gestellt: Ist dieser Boden für eine bestimmte Nutzung geeignet? Diese Frage ist so alt wie der Umgang mit Böden. Schon die Menschen der Steinzeit mussten sich fragen, ob es Gewinn bringt, den Wald zu roden und ihn zu ackerbaulichen Zwecken umzufunktionieren. Auch die Anfänge der Bodensystematik sind in der Nutzbarkeit der Böden begründet (vgl. Kap. 7). Die wichtigste Einschätzung ist nach wie vor die Frage nach der Bodenfruchtbarkeit bzw. nach dem Ertragspotenzial der Böden für verschiedene Kulturen. Am besten überliefert ist uns aus römischer und griechischer Literatur die Koinzidenz von Bodeneinteilung und Nutzungseignung unserer Böden.

Soil biodiversity remains one of the least systematically studied components of global biodiversity, largely invisible in policy agendas. A coordinated soil biodiversity monitoring approach is urgently needed to enable national‐level action.

Soils are multi-component, open systems and play a decisive role in natural energy and matter fluxes, e.g. in the storage and bioenergetic control of carbon. A key component in this system is soil organic matter (SOM), as it determines the functionality of the soil. SOM is formed by building blocks from biomass, plant and animal detritus. Therefore, SOM itself is a complex, supramolecular mixture of different components. This property complicates the thermodynamic characterization of SOM and consequently the determination of the energy content. The latter is an important piece of the puzzle for a thermodynamic description of energy fluxes in soil systems, which is necessary for a holistic understanding of SOM turnover and stabilization. In soil science, simultaneous thermal analysis (STA) is used to determine the energy content of SOM. The soil sample is heated in crucibles in a defined temperature program (e.g. 30-1000 °C, 10 °C/min) under an oxidative atmosphere. During heating, the mass loss (thermogravimetry, TG) and heat flux caused by SOM combustion (dynamic scanning calorimetry, DSC) are measured simultaneously. The STA data can be used to determine the energy content of the SOM during combustion and to identify SOM fractions of different thermal stability. To develop a deeper understanding of the reactions taking place during STA of SOM, we investigated the combustion of building blocks of SOM and examined the influence of different crucible setups (Al2O3 with and without lid, Pt-Rh-Al2O3 with lid) on the measured energy content. The selection of building blocks included well-defined compounds like glucose, cellulose, chitin, etc. and complex compounds like maize straw, peptidoglycan, humic acid and lignin (organosolv). The STA was coupled with an evolved gas analyzer (mass spectrometer, MS) to draw also conclusions about the combustion reactions of the building blocks by monitoring H2O and CO2. Our results show two main points: First, the crucible setup has a huge impact on the measured energy content. A better thermal conductivity (Pt-Rh > Al2O3) and the use of a lid lead to an increase in the measured energy content. Secondly, we observe two distinguishable thermal reactions for most of the building blocks, which were mainly revealed by the release of H2O and CO2. The first reaction is a decomposition at low temperatures (< 400 °C) with the formation of char, which was then further oxidized at higher temperatures (> 400 °C). The change in the ratio between the H2O- and CO2-MS signal allows a clear allocation of different thermal reactions. In summary, the investigation of building blocks of SOM by STA coupled with MS provides a better understanding of the combustion of SOM in soil samples and thus allows a more reliable interpretation of the measured energy contents. Further STA studies should focus on the interaction between SOM building blocks and soil minerals to identify other possible thermal reactions that could affect the measured energy content.

BackgroundThe stability of soil organic matter (SOM) can be characterized by thermal analysis. Methods to determine the thermal stability of SOM have recently been increasingly applied in soil analysis. Most studies focus on organic carbon (OC), whereas its subfractions, for example, microbial biomass carbon (MBC) or hot water-extractable carbon (HWEC), representing fast-reacting pools, have been less investigated.AimA set of 100 soil samples was analyzed for thermal mass losses and their relation to SOM and soil mineral phase properties.MethodThe temperature-dependent mass losses were determined by thermogravimetric analysis. For this purpose, soils differing in terms of parent material, soil texture, and land use were characterized and analyzed.ResultsTemperature ranges of mass losses and corresponding fractions of different thermal stability (thermolabile and thermostable) were defined. SOM-related parameters were highly correlated with mass losses of the thermolabile fractions. Mass losses of thermostable matter were significantly correlated with soil mineral phase parameters. The soil thermostability index (STSI) was calculated as the ratio of thermolabile and thermostable mass proportions, represented by the mass losses of selected temperature intervals. Regressions of STSI with ratios of mineral phase parameters to OC (e.g., clay/OC), representing the saturation degree of the mineral phase with OC, HWEC, or MBC, yielded strong relationships.ConclusionThe saturation of the mineral phase with OC determines the thermal stability of OC. Overall, relevant factors for OC thermal stability were identified. OC and HWEC were significantly correlated with thermal stability and mineral phase saturation. For MBC, no such relationship was found, indicating that its stability is driven by other factors.

The thermodynamic perspective on soil systems gets more and more in the research focus and has the potential to take us a substantial step toward a holistic understanding of soil organic matter (SOM) turnover and stabilization. An integral part of new bioenergetic concepts and models is the energy content of SOM, but its determination particularly in mineral soils is challenging. One of the most promising techniques in this respect is thermogravimetry combined with differential scanning calorimetry (TG-DSC), where the heat of combustion is related to the mass losses of soil material during a temperature ramp from 50 to 1000°C under an oxidative atmosphere. Heat and mass changes in the range from 180-600°C are usually interpreted as the result from the exothermic reaction of SOM and thus used to obtain the energy content (combustion enthalpy, ∆CH) of SOM. Overlapping exo- and endothermic reactions by other non-oxidizing processes (e.g. dehydroxylation/-carboxylation and desorption of soil minerals etc.) in that temperature range are often neglected because their distinction and quantification from the rather strong exothermic oxidation reactions from SOM is challenging. To investigate this, we determined the ∆CH of an organic substrate (cellulose) and soil minerals (quartz sand, quartz silt, goethite, illite, montmorillonite) 1) individually, 2) intensively mixed in the dry state, and 3) intensively mixed after several wetting-drying cycles. Furthermore, the minerals were mixed to create a silt loam texture and combined with cellulose to mimic an artificial soil. Calorimetric analyses were conducted using a TG-DSC coupled with a mass spectrometer (MS) to analyze the evolved gases during combustion. First results show that the ∆CH value obtained by TG-DSC is lower for the organic substrate compared to reference values obtained by combustion calorimetry as the standard method. Furthermore, ∆CH differs when mineral compounds are mixed with cellulose indicating that thermal reactions by mineral soil compounds affect the determination of the energy content by the TG-DSC standard procedure described above. This is supported by the analyses of the pure mineral compounds, which revealed that all investigated minerals show exothermic and/or endothermic side reactions in the range from 180-600°C affecting the TG-DSC signal. In dependence on the mineral composition of the soil, the energy content of SOM by the classical TG-DSC approach can be substantially over- or underestimated. From this first data set, we identified options to improve both the measurement and the data evaluation procedures. Building on this, we aim to develop a procedure for the accurate measurement of the energy content of SOM in (mineral) soils by TG-DSC(-MS), taking into account the contribution of mineral oxidation and the effect of organo-mineral associations on the energetic signatures derived from the thermograms. This is crucial if energy flows and sinks in soil systems are to be quantified to better understand OM turnover and stabilization in soil.

Microplastics (MP) in soil have emerged as an environmental pollutant of increasing interest in recent years, emphasizing the need for efficient screening methods. Hyperspectral imaging in the visible and near-infrared (VNIR) and short-wave infrared (SWIR) coupled with machine learning (ML) have shown potential for rapid, cost-effective MP detection in soils. However, key methodological challenges, including optimal ML algorithms for MP classification, detection limits dependent on MP type, and scaling relationships between area-based hyperspectral imaging and soil MP concentrations, should further be explored. In this study, we explored the potential of SWIR hyperspectral imaging to detect and quantify three MP types (polyamide - PA, polyethylene - PE, polypropylene - PP) at the (sub-)pixel level in soil-MP mixtures with concentrations ranging from 0.01 wt-% to 5.00 wt-% using Partial Least Squares - Discriminant Analysis (PLSDA), Random Forests (RF), 1D-Convolutional Neural Networks (1D-CNN) and a three-model ensemble. All machine learning algorithms achieved comparable classification accuracies in a calibration-validation approach on a large spectral library developed from pure material spectra. When applied to the independent SWIR image data, RF performance decreased markedly, whereas the ensemble proved beneficial to suppress individual model-specific random misclassifications. We found a close non-linear relationship between the SWIR image area-based MP quantification and the actual concentration (wt-%) of MP in the soil samples that depended on the MP type. Interpolated MP detection limits were also MP-type specific and corresponded to 0.05 wt-%, 0.46 wt-% and 1.15 wt-% for PE, PP and PA, respectively, with the larger PE particles having a lower detection limit than the more finely dispersed PA and PP particles. Our results show that hyperspectral SWIR imaging has the potential to enable screening applications where elevated MP levels can occur, such as landfill or industrial sites, but is likely not sensitive enough to detect current background concentrations.