publications

2024

1. PRISMSPLC

   Superabsorbent Polymers in Soil: The New Microplastics?

   Christian Buchmann, Janina Neff, Maximilian Meyer, Mirco Bundschuh, and Zacharias Steinmetz

   Cambridge Prisms: Plastics 2(e3), 1–14, 2024

   Abstract DOI PDF

   The extensive use of synthetic polymers in our everyday lives has resulted in significant plastic pollution. Superabsorbent polymers (SAPs) are yet another class of anthropogenic materials with uncertain environmental implications. SAPs, like polyacrylates (PAA) or polyacrylamides (PAM), find applications in personal care products, construction, wastewater treatment, agriculture and soil remediation. However, when SAPs enter the soil, weathering may change their intended properties, potentially forming plastic-like solid residues over time. This review aims to evaluate the current scientific understanding of the application and environmental fate of SAPs in soil, focusing on the processes driving their potential transformation into solid residues. We explore analytical techniques for the qualitative and quantitative characterization of SAPs and solid SAP residues. Our research provides first insights into the potential mechanisms and conditions governing SAP aging and transformation, advancing our understanding of the fate of SAPs in soil and their impact on soil properties and functioning. There are specific knowledge gaps regarding the influence of climate change on the application and transformation of SAPs in soil. To facilitate future research, we suggest scrutinizing relevant processes of SAP transformation in the field, critically (re)evaluating SAP application to the soil and establishing robust monitoring methods.
2. ENVPOL

   Vertical Distribution of Microplastics in an Agricultural Soil after Long-Term Treatment with Sewage Sludge and Mineral Fertiliser

   Wiebke Mareile Heinze, Zacharias Steinmetz, Nanna Dyg Rathje Klemmensen, Jes Vollertsen, and Geert Cornelis

   Environmental Pollution 356, 124343, 2024

   Abstract DOI PDF

   Sewage sludge applications release contaminants to agricultural soils, such as potentially toxic metals and microplastics (MPs). However, factors determining the subsequent mobility of MPs in long-term field conditions are poorly understood. This study aimed to understand the vertical distribution of MPs in soils amended with sewage sludge in comparison to conventional mineral fertiliser for 24 years. The depth-dependent MP mass and number concentrations, plastic types, sizes and shapes were compared with the distribution of organic carbon and metals to provide insights into potentially transport-limiting factors. Polyethylene, polypropylene and polystyrene mass concentrations were screened down to 90 cm depth via pyrolysis-gas chromatography/mass spectrometry. MP number concentrations, additional plastic types, sizes, and shapes were analysed down to 40 cm depth using micro-Fourier transform-infrared imaging. Across all depths, MP numbers were twice and mass concentrations 8 times higher when sewage sludge was applied, with a higher share of textile-related plastics, more fibres and on average larger particles than in soil receiving mineral fertiliser. Transport of MPs beyond the plough layer (0–20 cm) is often assumed negligible, but substantial MP numbers (42 %) and mass (52 %) were detected down to 70 cm in sewage sludge-amended soils. The initial mobilization of MPs was shape- and sizedependent, because the fractions of fragmental-shaped and relatively small MPs increased directly below the plough layer, but not at greater depths. The sharp decline of total MP concentrations between 20 and 40 cm depth resembled that of metals and organic matter suggesting similar transport limitations. We hypothesize that the effect of soil management, such as ploughing, on soil compactness and subsequent transport by bioturbation and via macropores drives vertical MP distribution over long time scales. Risk assessment in soils should therefore account for considerable MP displacement to avoid underestimating soil exposure.
3. TrAC

   Plastic Problem Solved? Environmental Implications of Synthetic Hydrophilic Polymers across Ecosystem Boundaries

   Zacharias Steinmetz, Christian Plicht, Christian Buchmann, Mathilde Knott, Maximilian Meyer, Stefanie Müller-Schüssele, Dorina Strieth, Marc H. Prosenc, Heidrun Steinmetz, Hermann F. Jungkunst, Werner R. Thiel, and Mirco Bundschuh

   TrAC Trends in Analytical Chemistry 181, 118000, 2024

   Abstract DOI PDF

   Synthetic hydrophilic polymers are an emerging yet overlooked class of anthropogenic substances. Unlike particulate plastics, synthetic hydrophilic polymers can interact with water, which complicates studying their fate and effects in the environment. This review discusses the sources, fate, and effects of these polymers across ecosystem boundaries. We identified households, agriculture, and mining as major sources. Despite wastewater treatment, synthetic hydrophilic polymers enter natural waterbodies. Agrochemical and sewage sludge applications release them to soil. Sorption and coagulation processes, influenced by polarity and molecular weight, likely define their fate through aquatic and terrestrial systems. Slow biodegradation may favor their accumulation. To advance our understanding of their fate, analytical techniques need improvement. Ecotoxicity studies found acute effects but long-term and field studies on mixtures and interactions with other pollutants are lacking. All in all, the prevailing literature emphasizes benefits of synthetic hydrophilic polymers while neglecting potential negative consequences; this calls for precaution.

2023

1. Recycling

   Identification and Evaluation of (Non-)Intentionally Added Substances in Post-Consumer Recyclates and Their Toxicological Classification

   Christian Rung, Frank Welle, Anita Gruner, Arielle Springer, Zacharias Steinmetz, and Katherine Munoz

   Recycling 8(1), 24, 2023

   Abstract DOI PDF

   According to the European circular economy strategy, all plastic packaging placed on the market by 2030 has to be recyclable. However, for recycled plastics in direct contact with food, there are still major safety concerns because (non-)intentionally added substances can potentially migrate from recycled polymers into foodstuffs. Therefore, the European Food Safety Authority (EFSA) has derived very low migration limits (e.g., 0.1 µg/L for recycled polyethylene terephthalate (PET) and 0.06 µg/L for recycled high-density polyethylene (HDPE)) for recycled polymers. Thus, the use of recyclates from post-consumer waste materials in direct food contact is currently only possible for PET. A first step in assessing potential health hazards is, therefore, the identification and toxicological classification of detected substances. Within this study, samples of post-consumer recyclates from different packaging-relevant recycling materials (HDPE, LDPE, PE, PP, PET, and PS) were analyzed. The detected substances were identified and examined with a focus on their abundance, toxicity (Cramer classification), polarity (log P values), chemical diversity, and origin (post-consumer substances vs. virgin base polymer substances). It was demonstrated that polyolefins contain more substances classified as toxic than PET, potentially due to their higher diffusivity. In addition, despite its low diffusivity compared to polyolefins, a high number of substances was found in PS. Further, post-consumer substances were found to be significantly more toxicologically concerning than virgin base polymer substances. Additionally, a correlation between high log P values and a high Cramer classification was found. It was concluded that PET is currently the only polymer that complies with EFSA’s requirements for a circular economy. However, better-structured collection systems and cleaning processes, as well as more analytical methods that enable a highly sensitive detection and identification of substances, might offer the possibility of implementing other polymers into recycling processes in the future.
2. ETC

   Subsidy Quality Affects Common Riparian Web-Building Spiders: Consequences of Aquatic Contamination and Food Resource

   Sebastian Pietz, Sara Kolbenschlag, Nina Röder, Alexis P. Roodt, Zacharias Steinmetz, Alessandro Manfrin, Klaus Schwenk, Ralf Schulz, Ralf B. Schäfer, Jochen P. Zubrod, and Mirco Bundschuh

   Environmental Toxicology and Chemistry 42(6), 1346–1358, 2023

   Abstract DOI PDF

   Anthropogenic stressors can affect the emergence of aquatic insects. These insects link aquatic and adjacent terrestrial food webs, serving as high-quality subsidy to terrestrial consumers, such as spiders. While previous studies have demonstrated that changes in the emergence biomass and timing may propagate across ecosystem boundaries, the physiological consequences of altered subsidy quality for spiders are largely unknown. We used a model food chain to study the potential effects of subsidy quality: Tetragnatha spp. were exclusively fed with emergent Chironomus riparius cultured in the absence or presence of either copper (Cu), Bacillus thuringiensis var. israelensis (Bti), or a mixture of synthetic pesticides paired with two basal resources (Spirulina vs. TetraMin®) of differing quality in terms of fatty acid (FA) composition. Basal resources shaped the FA profile of chironomids, whereas their effect on the FA profile of spiders decreased, presumably due to the capacity of both chironomids and spiders to modify (dietary) FA. In contrast, aquatic contaminants had negligible effects on prey FA profiles but reduced the content of physiologically important polyunsaturated FAs, such as 20:4n-6 (arachidonic acid) and 20:5n-3 (eicosapentaenoic acid), in spiders by approximately 30% in Cu and Bti treatments. This may have contributed to the statistically significant decline (40%–50%) in spider growth. The observed effects in spiders are likely related to prey nutritional quality because biomass consumption by spiders was, because of our experimental design, constant. Analyses of additional parameters that describe the nutritional quality for consumers such as proteins, carbohydrates, and the retention of contaminants may shed further light on the underlying mechanisms. Our results highlight that aquatic contaminants can affect the physiology of riparian spiders, likely by altering subsidy quality, with potential implications for terrestrial food webs.
3. JTAC

   A Differential Scanning Calorimetry (DSC) Approach for Assessing the Quality of Polyethylene Terephthalate (PET) Waste for Physical Recycling: A Proof-of-Concept Study

   Lucie Šudomová, Helena Doležalová Weissmannová, Zacharias Steinmetz, Veronika Řezáčová, and Jiří Kučerík

   Journal of Thermal Analysis and Calorimetry 148(20), 10843–10855, 2023

   Abstract DOI PDF

   Physical recycling of plastics is among the most important approaches of circular economy. The efficiency of the recycling is influenced by many factors including the number of recycling cycles, composition of plastics, chemical modifications, additives and others. Currently, however, there are no methods enabling to distinguish the quality of plastics for recycling. In this work, we address this issue and suggest a new method based on the correlation of solely thermophysical properties of polyethylene terephthalate (PET) waste obtained using differential scanning calorimetry (DSC) during repeated heating and cooling. The combination of results of differential scanning calorimetry and advanced statistical methods enabled to separate 76 PET samples into six groups according to their origin, chemical modification, degradation and suitability for recycling. The discriminant analysis enabled to suggest a model which uses for the discrimination a combination of temperatures and enthalpies of melting and crystallization. The approach illustrates that thermophysical properties, which can be obtained using a single DSC experiment, can be used to distinguish the polymers of various origin and quality.

2022

1. SOIL

   Are agricultural plastic covers a source of plastic debris in soil? A first screening study

   Zacharias Steinmetz, Paul Löffler, Silvia Eichhöfer, Jan David, Katherine Muñoz, and Gabriele E. Schaumann

   SOIL 8(1), 31–47, 2022

   Abstract DOI PDF Data

   Agricultural plastic covers made from polyethylene (PE) and polypropylene (PP) provide increased yields and an improved crop quality. However, such covers are suspected of partially breaking down into smaller debris and thereby contributing to soil pollution with microplastics. To scrutinize this, we randomly sampled 240 topsoil cores (0–5 cm) from eight fields which were covered with fleeces, perforated foils, and plastic mulches for less than 2 years. Samples from the field periphery (50 m perimeter) served as a reference. Visual plastic debris >2 mm was analyzed by Fourier transform infrared spectroscopy. Smaller, soil-associated plastic debris was dispersed from 50 g of fine soil (≤ 2 mm) using sodium hexametaphosphate solution and density-separated with saturated NaCl solution. The collected PE, PP, and polystyrene (PS) debris was selectively dissolved in a mixture of 1,2,4-trichlorobenzene and p-xylene at 150 °C and quantified by pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS). We counted six PE and PS fragments >2 mm in two out of eight fields. By contrast, Py-GC/MS detected PE, PP, and PS contents in the fine soil of six fields (6 % of all samples). In three fields, PE levels of 3–35 mg kg⁻¹ were potentially associated with the use of thinner and less durable perforated foils (40 µm thickness). This was slightly more pronounced at field edges where the plastic covers are turned and weighed down. By contrast, 50 µm thick PE films were not shown to emit any plastic debris. PP contents of 5–10 mg kg⁻¹ were restricted to single observations in the field centers of three sites. At one site, we found expanded PS particles >2 mm that concurred with elevated PS levels (8–19 mg kg⁻¹) in the fine soil. Both PP and PS were distributed indistinctly across sites so that their source remained unresolved. In addition, the extent to which plastic contents of up to 7 mg kg⁻¹ in the field periphery of some sites were attributed to wind drift from the covered fields or from external sources needs to be investigated in future studies. Our results suggest that the short-term use of thicker and more durable plastic covers should be preferred over thinner or perforated films to limit plastic emissions and accumulation in soil.
2. Soil Systems

   Effects of Plastic versus Straw Mulching Systems on Soil Microbial Community Structure and Enzymes in Strawberry Cultivation

   Katherine Muñoz, Sören Thiele-Bruhn, Kilian G. J. Kenngott, Maximilian Meyer, Dörte Diehl, Zacharias Steinmetz, and Gabriele E. Schaumann

   Soil Systems 6(1), 21, 2022

   Abstract DOI PDF

   This study aimed to evaluate changes in abundance, structure, and enzyme activity of the soil microbiome in response to 4 years of mulching using either black polyethylene plastic film (PM) or wheat straw (SM). Soil samples (depth 0–5 and 5–10 cm) were collected from conventional strawberry plots, in two samplings: 1 week prior (S1) and 7 weeks after straw application (S2). Selected soil properties were monitored in each system and the abundance and structure of microbial communities were characterized via phospholipid fatty acid (PLFA) analysis. The investigation of soil microbial functions included activities of the enzymes chitinase, leucine aminopeptidase, and acid phosphatase, as well as function genes involved in nitrogen transformation. Each mulch system resulted in distinct physicochemical properties. In particular, a pH value higher by one-unit under PM (7.6 ± 0.3) compared to SM (6.5 ± 0.3) was observed. Values for SOC, DOC, and total-N were 15%, 22%, and 16% higher in PM than in SM. The microbial biomass (total PLFAs) was 1.5-fold higher in SM compared to PM. The abundance of soil fungi (F) and bacteria (B) increased by 37% and 44% after straw incorporation compared to PM (S2). In particular, Gram-negative bacteria (gr–) increased by twofold in SM. Consequently, wider F:B and gr+:gr– ratios were observed in PM. According to the shifts in microbial abundance, the activity of the enzyme chitinase was lower by 27% in PM, while the activity of the acid phosphatase increased by 32%. Denitrification genes were not affected by the mulching systems. In conclusion, the abundance and structure of the investigated microbial groups and the enzyme activities were strongly influenced by the mulching system. In detail, effects on microbiota were primarily attributed to the altered soil pH and probably the input of degradable organic matter with straw mulching in SM. This resulted in higher abundance of soil microorganisms in SM, although measures within this cultivation system such as fungicide application may have exerted adverse effects on the microbiota.
3. PeerJ

   Plastic debris in plastic-mulched soil—a screening study from western Germany

   Zacharias Steinmetz, and Heike Schröder

   PeerJ 10, e13781, 2022

   Abstract DOI PDF Data

   Background. Agricultural plastic mulches offer great benefits such as higher yields and lower pesticide use. Yet, plastic mulches may disintegrate over time and fragment into smaller debris. Such plastic debris is expected to remain in the field after removal of the plastic mulch and thus contributes to soil contamination with plastics. Method. To investigate this, we collected soil samples at 0–10 cm and 10–40 cm depth from three fields covered with black mulch film for three consecutive years. Three fields without any reported plastic use served as control. Visual plastic debris > 1 cm (macroplastics) was collected from the soil surface. Mesoplastics between 2 mm and 1 cm were density separated from the sampled soil using saturated NaCl solution and analyzed by Fourier-transform infrared spectroscopy. Debris ≤ 2 mm (microplastics) was dispersed from 50 g soil using sodium hexametaphosphate solution followed by the aforementioned density separation. The separated polyethylene (PE), polypropylene (PP), and polystyrene (PS) were quantified via solvent-based pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS). Results. With 89–206 fragments ha⁻¹, the majority of macroplastics were located in fields previously covered with mulch films. 80% of the collected specimen were identified as black PE film. The number of mesoplastics in plastic-mulched soil was 2.3 particles kg⁻¹, while only 1.0 particles kg⁻¹ were found in the reference fields. Py–GC/MS revealed microplastic levels of up to 13 mg kg⁻¹. The PE content was significantly higher in plastic-mulched fields than in reference fields. Discussion. Although the identified plastic levels are lower than those reported in comparable studies, our results still suggest that plastic mulching functions as a source of plastic debris in agricultural systems. Due to its severely restricted degradability, these plastics are likely to accumulate in soil in the long term and further fragment into smaller and smaller debris.
4. ENVPOL

   Historical and current occurrence of microplastics in water and sediment of a Finnish lake affected by WWTP effluents

   Mirka Viitala, Zacharias Steinmetz, Mika Sillanpää, Mika Mänttäri, and Markus Sillanpää

   Environmental Pollution 314, 120298, 2022

   Abstract DOI PDF

   Only scarce information is available about the abundance of microplastics (MPs) in Nordic lakes. In this study, the occurrence, types, and distribution of MPs were assessed based on the lake water and sediment samples collected from a sub-basin of Lake Saimaa, Finland. The main goal was to estimate the possible effect of the local wastewater treatment plant (WWTP) on the abundance of MPs in different compartments of the recipient lake area. Collected bottom sediment samples were Cs-137 dated and the chronological structure was utilized to relate the concentrations of MPs to their sedimentation years. Raman microspectroscopy was used for the MPs’ identification from both sample matrices. In addition, MPs consisting of polyethylene (PE), polypropylene (PP) and polystyrene (PS) were quantified from lake water samples by pyrolysis-gas chromatography-mass spectrometry to provide a complementary assessment of MPs based on two different analysis methods, which provide different metrics of the abundance of microplastics. MPs concentrations were highest in sediment samples closest to the discharge site of WWTP effluents (4400 ± 620 n/kg dw) compared to other sites. However, such a trend was not found in lake water samples (0.7 ± 0.1 n/L). Overall, microplastic fibers were relatively more abundant in sediment (70%) than in water (40%), and the majority of detected microplastic fibers were identified as polyester. This indicates that a part of textile fibers passing the WWTP processes accumulate in the sediment close to the discharge site. In addition, the abundance of MPs was revealed to have increased slightly during the last 30 years.

2021

1. ANCHAM

   Microplastic Spectral Classification Needs an Open Source Community: Open Specy to the Rescue!

   Win Cowger, Zacharias Steinmetz, Andrew Gray, Keenan Munno, Jennifer Lynch, Hannah Hapich, Sebastian Primpke, Hannah De Frond, Chelsea Rochman, and Orestis Herodotou

   Analytical Chemistry 93(21), 7543–7548, 2021

   Abstract DOI Request PDF Code

   Microplastic pollution research has suffered from inadequate data and tools for spectral (Raman and infrared) classification. Spectral matching tools often are not accurate for microplastics identification and are cost-prohibitive. Lack of accuracy stems from the diversity of microplastic pollutants, which are not represented in spectral libraries. Here, we propose a viable software solution: Open Specy. Open Specy is on the web (www.openspecy.org) and in an R package. Open Specy is free and allows users to view, process, identify, and share their spectra to a community library. Users can upload and process their spectra using smoothing (Savitzky–Golay filter) and polynomial baseline correction techniques (IModPolyFit). The processed spectrum can be downloaded to be used in other applications or identified using an onboard reference library and correlation-based matching criteria. Open Specy’s data sharing and session log features ensure reproducible results. Open Specy houses a growing library of reference spectra, which increasingly represents the diversity of microplastics as a contaminant suite. We compared the functionality and accuracy of Open Specy for microplastic identification to commonly used spectral analysis software. We found that Open Specy was the only open source software and the only software with a community library, and Open Specy had comparable accuracy to popular software (OMNIC Picta and KnowItAll). Future developments will enhance spectral identification accuracy as the reference library and functionality grows through community-contributed spectra and community-developed code. Open Specy can also be used for applications beyond microplastic analysis. Open Specy’s source code is open source (CC-BY-4.0, attribution only) (https://github.com/wincowgerDEV/OpenSpecy).
2. ACSO

   Validation of a Simple and Reliable Method for the Determination of Aflatoxins in Soil and Food Matrices

   Julius Albert, Camilla A. More, Niklaus R. P. Dahlke, Zacharias Steinmetz, Gabriele E. Schaumann, and Katherine Muñoz

   ACS Omega 6(29), 18684–18693, 2021

   Abstract DOI PDF

   Aflatoxins (AFs) are toxic fungal secondary metabolites that are commonly detected in food commodities. Currently, there is a lack of generic methods capable of determining AFs both at postharvest stages in agricultural products and preharvest stages, namely, the agricultural soil. Here, we present a simple and reliable method for quantitative analysis of AFs in soil and food matrices at environmentally relevant concentrations for the first time, using the same extraction procedure and chromatography, either by HPLC-FLD or LC–MS. AFs were extracted from matrices by ultrasonication using an acetonitrile/water mixture (84:16, v + v) without extensive and time-consuming cleanup procedures. Food extracts were defatted with n-hexane. Matrix effects in terms of signal suppression/enhancement (SSE) for HPLC-FLD were within ±20% for all matrices tested. For LC–MS, the SSE values were mostly within ±20% for soil matrices but outside ±20% for all food matrices. The sensitivity of the method allowed quantitative analysis even at trace levels with quantification limits (LOQs) between 0.04 and 0.23 μg kg^–1 for HPLC-FLD and 0.06–0.23 μg kg^–1 for LC–MS. The recoveries ranged from 64 to 92, 74 to 101, and 78 to 103% for fortification levels of 0.5, 5, and 20 μg kg^–1, respectively, with repeatability values of 2–18%. The validation results are in accordance with the quality criteria and limits for mycotoxins set by the European Commission, thus confirming a satisfactory performance of the analytical method. Although reliable analysis is possible with both instruments, the HPLC-FLD method may be more suitable for routine analysis because it does not require consideration of the matrix.

2020

1. GEODER

   Effect of matric potential and soil-water-hydrogel interactions on biohydrogel-induced soil microstructural stability

   Christian Buchmann, Zacharias Steinmetz, Mathilde Brax, Stephan Peth, and Gabriele E. Schaumann

   Geoderma 362, 114142, 2020

   Abstract DOI Request PDF

   Soil structure formation and its stability against external stress ensure sufficient water, air and nutrient supply for plants under varying environmental conditions. In this context, soil-born biohydrogels glue soil particles together and increase structural stability and water retention via the formation of swollen interparticulate hydrogel structures. However, interparticulate hydrogel behavior in soil under fluctuating water potentials remains still unclear. We addressed this by treating loamy sand and clayey loam with alginate, a hydrogel-forming biopolymer, at various concentrations and adjusted them to matric potentials of ψ = −0.3 kPa, −3.2 kPa and −6.3 kPa. For both soils, we assessed soil-water interactions in terms of mobility, distribution and freezability of water by 1H nuclear magnetic resonance relaxometry and differential scanning calorimetry. The measurements on water entrapment were complemented with the characterization of soil microstructural stability using rheometry (amplitude sweep tests). Alginate hydrogel increased soil microstructural stability and shifted pore-size distributions towards smaller pore sizes with more restricted water mobility. Interestingly, alginate-induced microstructural stability remained constant or further increased with decreasing matric potential, although the effect of alginate on the entrapment and mobility of water decreased with decreasing matric potential for both soils. Moreover, the direction and intensity of alginate-derived effects differed between both soils as water entrapment increased for the loamy sand and decreased for the clayey loam, respectively. This effect was attributed to the mutually restricted swelling of alginate and clay particles as result of various polymer-clay interactions in the clayey loam, which increased the relative amount of less strongly bound water in the soil matrix. The results indicate that the gel effect is composed of several components that strongly depends on various intrinsic and extrinsic factors, including the properties of the hydrogel-forming biopolymer itself and the complex interplay with the available water and mineral surfaces in soil.
2. JAAP

   A simple method for the selective quantification of polyethylene, polypropylene, and polystyrene plastic debris in soil by pyrolysis-gas chromatography/mass spectrometry

   Zacharias Steinmetz, Aaron Kintzi, Katherine Muñoz, and Gabriele E. Schaumann

   Journal of Analytical and Applied Pyrolysis 147, 104803, 2020

   Abstract DOI Request PDF Data

   The lack of adequate analytical methods for the quantification of plastic debris in soil challenges a better understanding of their occurrence and fate in the terrestrial environment. With this proof-of-principle study, we developed a simple and fast method for the selective quantification of the three most environmentally relevant polymers polyethylene (PE), polypropylene (PP), and polystyrene (PS) in soil using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). In order to facilitate the preparation of calibration series and to better account for the heterogeneity of soil matrix, polymers were dissolved in 1,2,4-trichlorobenzene (TCB) at 120 °C. Thereby, liquid sample aliquots from up to 4 g of solid sample became amenable to pyrolysis without further preparation. To evaluate the performance of this approach, three reference soils with 1.73–5.16% organic carbon (C_org) were spiked at 50 and 250 μg g⁻¹ of each polymer and extracted with TCB. Prior cleanup steps with methanol, flocculation with KAl(SO₄)₂, or Fenton digestion were tested for their suitability to reduce potentially interfering C_org. Calibration curves responded linearly (adj. R² > 0.996) with instrumental detection limits of 1–86 ng corresponding to method detection limits of 1–86 μg g⁻¹. The measurement repeatability was 3.2–7.2% relative standard deviation. Recoveries of 70–128% were achieved for plastic contents of 250 μg g⁻¹ extracted with TCB without prior cleanup from soils with less than 2.5% C_org. A higher C_org particularly interfered with the quantification of PE. The addition of non-target polymers (polyethylene terephthalate, polyvinyl chloride, poly(methyl methacrylate), and tire wear particles) did not interfere with the quantification of the analytes highlighting the selectivity of the method. Further research is needed to determine low plastic contents in soils exceeding 2.5% C_org. With 1–3 h processing time per sample, our method has the potential for routine analyses and screening studies of agricultural systems to be complemented with microspectroscopic techniques for additional information on particle shapes and sizes.
3. Sustainability

   Sample Preparation Techniques for the Analysis of Microplastics in Soil—A Review

   Daniela Thomas, Berit Schütze, Wiebke Mareile Heinze, and Zacharias Steinmetz

   Sustainability 12(21), 9074, 2020

   Abstract DOI PDF

   Although most plastic pollution originates on land, current research largely remains focused on aquatic ecosystems. Studies pioneering terrestrial microplastic research have adapted analytical methods from aquatic research without acknowledging the complex nature of soil. Meanwhile, novel methods have been developed and further refined. However, methodical inconsistencies still challenge a comprehensive understanding of microplastic occurrence and fate in and on soil. This review aims to disentangle the variety of state-of-the-art sample preparation techniques for heterogeneous solid matrices to identify and discuss best-practice methods for soil-focused microplastic analyses. We show that soil sampling, homogenization, and aggregate dispersion are often neglected or incompletely documented. Microplastic preconcentration is typically performed by separating inorganic soil constituents with high-density salt solutions. Not yet standardized but currently most used separation setups involve overflowing beakers to retrieve supernatant plastics, although closed-design separation funnels probably reduce the risk of contamination. Fenton reagent may be particularly useful to digest soil organic matter if suspected to interfere with subsequent microplastic quantification. A promising new approach is extraction of target polymers with organic solvents. However, insufficiently characterized soils still impede an informed decision on optimal sample preparation. Further research and method development thus requires thorough validation and quality control with well-characterized matrices to enable robust routine analyses for terrestrial microplastics.

2019

1. AGRFORMET

   Implications of crop model ensemble size and composition for estimates of adaptation effects and agreement of recommendations

   A. Rodríguez, M. Ruiz-Ramos, T. Palosuo, T. R. Carter, S. Fronzek, I. J. Lorite, R. Ferrise, N. Pirttioja, M. Bindi, P. Baranowski, S. Buis, D. Cammarano, Y. Chen, B. Dumont, F. Ewert, T. Gaiser, P. Hlavinka, H. Hoffmann, J. G. Höhn, F. Jurecka, K. C. Kersebaum, J. Krzyszczak, M. Lana, A. Mechiche-Alami, J. Minet, M. Montesino, C. Nendel, J. R. Porter, F. Ruget, M. A. Semenov, Z. Steinmetz, P. Stratonovitch, I. Supit, F. Tao, M. Trnka, A. Wit, and R. P. Rötter

   Agricultural and Forest Meteorology 264, 351–362, 2019

   Abstract DOI PDF

   Climate change is expected to severely affect cropping systems and food production in many parts of the world unless local adaptation can ameliorate these impacts. Ensembles of crop simulation models can be useful tools for assessing if proposed adaptation options are capable of achieving target yields, whilst also quantifying the share of uncertainty in the simulated crop impact resulting from the crop models themselves. Although some studies have analysed the influence of ensemble size on model outcomes, the effect of ensemble composition has not yet been properly appraised. Moreover, results and derived recommendations typically rely on averaged ensemble simulation results without accounting sufficiently for the spread of model outcomes. Therefore, we developed an Ensemble Outcome Agreement (EOA) index, which analyses the effect of changes in composition and size of a multi-model ensemble (MME) to evaluate the level of agreement between MME outcomes with respect to a given hypothesis (e.g. that adaptation measures result in positive crop responses). We analysed the recommendations of a previous study performed with an ensemble of 17 crop models and testing 54 adaptation options for rainfed winter wheat (Triticum aestivum L.) at Lleida (NE Spain) under perturbed conditions of temperature, precipitation and atmospheric CO₂ concentration. Our results confirmed that most adaptations recommended in the previous study have a positive effect. However, we also showed that some options did not remain recommendable in specific conditions if different ensembles were considered. Using EOA, we were able to identify the adaptation options for which there is high confidence in their effectiveness at enhancing yields, even under severe climate perturbations. These include substituting spring wheat for winter wheat combined with earlier sowing dates and standard or longer duration cultivars, or introducing supplementary irrigation, the latter increasing EOA values in all cases. There is low confidence in recovering yields to baseline levels, although this target could be attained for some adaptation options under moderate climate perturbations. Recommendations derived from such robust results may provide crucial information for stakeholders seeking to implement adaptation measures.
2. Chemosphere

   Introducing a soil universal model method (SUMM) and its application for qualitative and quantitative determination of poly(ethylene), poly(styrene), poly(vinyl chloride) and poly(ethylene terephthalate) microplastics in a model soil

   Jan David, Helena Doležalová Weissmannová, Zacharias Steinmetz, Lucie Kabelíková, Michael Scott Demyan, Jana Šimečková, David Tokarski, Christian Siewert, Gabriele E. Schaumann, and Jiří Kučerík

   Chemosphere 225, 810–819, 2019

   Abstract DOI Request PDF

   Methods for analysis of microplastic in soils are still being developed. In this study, we evaluated the potential of a soil universal model method (SUMM) based on thermogravimetry (TGA) for the identification and quantification of microplastics in standard loamy sand. Blank and spiked soils (with amounts of one of four microplastic types) were analyzed by TGA. For each sample, thermal mass losses (TML) in 10 °C intervals were extracted and used for further analysis. To explain and demonstrate the principles of SUMM, two scenarios were discussed. The first refers to a rare situation in which an uncontaminated blank of investigated soil is available and TML of spiked and blank soils are subtracted. The results showed that the investigated microplastics degraded in characteristic temperature areas and differences between spiked and blank soils were proportional to the microplastics concentrations. The second scenario reflects the more common situation where the blank is not available and needs to be replaced by the previously developed interrelationships representing soil universal models. The models were consequently subtracted from measured TML. Sparse principal component analysis (sPCA) identified 8 of 14 modeled differences between measured TMLs and the universal model as meaningful for microplastics discrimination. Calibrating various microplastics concentrations with the first principal component extracted from sPCA resulted in linear fits and limits of detection in between environmentally relevant microplastics concentrations. Even if such an approach using calculated standards still has limitations, the SUMM shows a certain potential for a fast pre-screening method for analysis of microplastics in soils.
3. Chemosphere

   Biodegradation and photooxidation of phenolic compounds in soil—A compound-specific stable isotope approach

   Zacharias Steinmetz, Markus P. Kurtz, Jochen P. Zubrod, Armin H. Meyer, Martin Elsner, and Gabriele E. Schaumann

   Chemosphere 230, 210–218, 2019

   Abstract DOI Request PDF

   Phenolic compounds occur in a variety of plants and can be used as model compounds for investigating the fate of organic wastewater, lignin, or soil organic matter in the environment. The aim of this study was to better understand and differentiate mechanisms associated with photo- and biodegradation of tyrosol, vanillin, vanillic acid, and coumaric acid in soil. In a 29 d incubation experiment, soil spiked with these phenolic compounds was either subjected to UV irradiation under sterile conditions or to the native soil microbial community in the dark. Changes in the isotopic composition (δ¹³C) of phenolic compounds were determined by gas chromatography–isotope ratio mass spectrometry and complemented by concentration measurements. Phospholipid-derived fatty acid and ergosterol biomarkers together with soil water repellency measurements provided information on soil microbial and physical properties. Biodegradation followed pseudo-first-order dissipation kinetics, enriched remaining phenolic compounds in 13C, and was associated with increased fungal rather than bacterial biomarkers. Growing mycelia rendered the soil slightly water repellent. High sample variation limited the reliable estimation of apparent kinetic isotope effects (AKIEs) to tyrosol. The AKIE of tyrosol biodegradation was 1.007 ± 0.002. Photooxidation kinetics were of pseudo-zero- or first-order with an AKIE of 1.02 ± 0.01 for tyrosol, suggesting a hydroxyl-radical mediated degradation process. Further research needs to address δ¹³C variation among sample replicates potentially originating from heterogeneous reaction spaces in soil. Here, nuclear magnetic resonance or nanoscopic imaging could help to better understand the distribution of organic compounds and their transformation in the soil matrix.

2018

1. AGSY

   Adaptation response surfaces for managing wheat under perturbed climate and CO₂ in a Mediterranean environment

   M. Ruiz-Ramos, R. Ferrise, A. Rodríguez, I. J. Lorite, M. Bindi, T. R. Carter, S. Fronzek, T. Palosuo, N. Pirttioja, P. Baranowski, S. Buis, D. Cammarano, Y. Chen, B. Dumont, F. Ewert, T. Gaiser, P. Hlavinka, H. Hoffmann, J. G. Höhn, F. Jurecka, K. C. Kersebaum, J. Krzyszczak, M. Lana, A. Mechiche-Alami, J. Minet, M. Montesino, C. Nendel, J. R. Porter, F. Ruget, M. A. Semenov, Z. Steinmetz, P. Stratonovitch, I. Supit, F. Tao, M. Trnka, A. Wit, and R. P. Rötter

   Agricultural Systems 159(Supplement C), 260–274, 2018

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   Adaptation of crops to climate change has to be addressed locally due to the variability of soil, climate and the specific socio-economic settings influencing farm management decisions. Adaptation of rainfed cropping systems in the Mediterranean is especially challenging due to the projected decline in precipitation in the coming decades, which will increase the risk of droughts. Methods that can help explore uncertainties in climate projections and crop modelling, such as impact response surfaces (IRSs) and ensemble modelling, can then be valuable for identifying effective adaptations. Here, an ensemble of 17 crop models was used to simulate a total of 54 adaptation options for rainfed winter wheat (Triticum aestivum) at Lleida (NE Spain). To support the ensemble building, an ex post quality check of model simulations based on several criteria was performed. Those criteria were based on the “According to Our Current Knowledge” (AOCK) concept, which has been formalized here. Adaptations were based on changes in cultivars and management regarding phenology, vernalization, sowing date and irrigation. The effects of adaptation options under changed precipitation (P), temperature (T), [CO₂] and soil type were analysed by constructing response surfaces, which we termed, in accordance with their specific purpose, adaptation response surfaces (ARSs). These were created to assess the effect of adaptations through a range of plausible P, T and [CO₂] perturbations. The results indicated that impacts of altered climate were predominantly negative. No single adaptation was capable of overcoming the detrimental effect of the complex interactions imposed by the P, T and [CO₂] perturbations except for supplementary irrigation (sI), which reduced the potential impacts under most of the perturbations. Yet, a combination of adaptations for dealing with climate change demonstrated that effective adaptation is possible at Lleida. Combinations based on a cultivar without vernalization requirements showed good and wide adaptation potential. Few combined adaptation options performed well under rainfed conditions. However, a single sI was sufficient to develop a high adaptation potential, including options mainly based on spring wheat, current cycle duration and early sowing date. Depending on local environment (e.g. soil type), many of these adaptations can maintain current yield levels under moderate changes in T and P, and some also under strong changes. We conclude that ARSs can offer a useful tool for supporting planning of field level adaptation under conditions of high uncertainty.
2. ANCHAM

   Quantitative Analysis of Poly(ethylene terephthalate) Microplastics in Soil via Thermogravimetry–Mass Spectrometry

   Jan David, Zacharias Steinmetz, Jiří Kučerík, and Gabriele E. Schaumann

   Analytical Chemistry 90(15), 8793–8799, 2018

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   The use of plastic materials in daily life, industry, and agriculture can cause soil pollution with plastic fragments down to the micrometer scale, i.e., microplastics. Quantitative assessment of microplastics in soil has been limited so far. Until now, microplastic analyses in soil require laborious sample cleanup and are mostly restricted to qualitative assessments. In this study, we applied thermogravimetry–mass spectrometry (TGA–MS) to develop a method for the direct quantitative analysis of poly(ethylene terephthalate) (PET) without further sample pretreatment. For this, soil samples containing 1.61 ± 0.15 wt % organic matter were spiked with 0.23–4.59 wt % PET bottle recyclate microplastics. dl-Cysteine was used as the internal standard (IS). Sample mixtures were pyrolyzed with a 5 K min^–1 ramp (40–1000 °C), while sample mass loss and MS signal intensity of typical PET pyrolysis products were recorded. We found MS signal intensities linearly responding to microplastic concentrations. The most-promising results were obtained with the IS-corrected PET pyrolysis product vinylbenzene/benzoic acid (m/z = 105, adj. R² = 0.987). The limits of detection and quantification were 0.07 and 1.72 wt % PET, respectively. Our results suggest that TGA–MS can be an easy and viable complement to existing methods such as pyrolysis or thermogravimetry–thermal desorption assays followed by gas chromatography/mass spectrometry detection or to spectral microscopy techniques.

2017

1. APSOIL

   Physicochemical and microbial soil quality indicators as affected by the agricultural management system in strawberry cultivation using straw or black polyethylene mulching

   K. Muñoz, C. Buchmann, M. Meyer, M. Schmidt-Heydt, Z. Steinmetz, D. Diehl, S. Thiele-Bruhn, and G. E. Schaumann

   Applied Soil Ecology 113, 36–44, 2017

   Abstract DOI Request PDF

   The aim of this study was to understand the differences in physicochemical and microbial soil quality resulting from the use of either wheat straw or black polyethylene, two widely used practices in strawberry cultivation. Soil samples were collected from strawberry crops used during 4 years as mono-cropping system, covered by either straw or black polyethylene (plastic mulching). Soil physicochemical properties included water content, pH, effective cation exchange capacity, elemental analysis of total carbon and nitrogen, dissolved and total organic carbon, and soil stability by percentage of water-stable aggregates (>0.2 mm). Soil microbial analysis comprised soil microbial biomass (C_mic and N_mic and DNA concentrations) and estimation of soil eco-physiological conditions C_mic:C_org and N_mic:Ntot. Soil bacteria and a fraction of cultivable fungi were studied respectively by molecular analysis and counting of colony-forming units (CFU values). Mycotoxin concentration in soil (deoxynivalenol) was used as an indirect indicator of fungal stress. The plastic mulching system showed positive effects on soil physicochemical properties as compared to straw mulching: Higher soil carbon content and better aggregate stability were observed in soils under plastic film, and the values for soil microbial biomass were comparable in both systems. Yet, soil eco-physiological conditions under plastic mulching were less appropriate compared to straw, as reflected by a reduced C_mic:C_org ratio (1.3 ± 0.3%), followed by a decline of the number of bacteria (18%), a six-fold reduction of the biomass of soil cultivable fungi, and finally by a two-times higher deoxynivalenol concentration in soil (mean 2.2 ± 2.4 μg kg⁻¹). This indicates that the plastic mulching system led to less favourable soil conditions and that the production of mycotoxins can be understood as a stress induced response by fungi. Further information is therefore needed to assess how the quality of soil is restricted by the shift of soil microbial communities and by the production of mycotoxins, especially in intensive agriculture with long-term plastic coverage.
2. JSSS

   Fractionation of copper and uranium in organic and conventional vineyard soils and adjacent stream sediments studied by sequential extraction

   Zacharias Steinmetz, Kilian G. J. Kenngott, Mohamed Azeroual, Ralf B. Schäfer, and Gabriele E. Schaumann

   Journal of Soils and Sediments 17(4), 1092–1100, 2017

   Abstract DOI Request PDF Data

   PurposeParticularly in organic viticulture, copper compounds are intentionally released into the environment as fungicide, whereas uranium originates from conventional phosphate fertilization. Both activities contribute to the metal contamination in wine-growing areas. This pilot study aimed to better understand how soil properties influence the presence and environmental fate of copper and uranium with respect to viticultural management.Materials and methodsWe characterized metal binding forms, i.e., their association with different soil constituents, in organically and conventionally cultivated vineyard soils and adjacent upstream and downstream sediments. The available metal fraction and the fractions associated with manganese oxides, organic matter, iron oxides, and total contents were extracted sequentially.Results and discussionTotal soil copper ranged from 200 to 1600 mg kg⁻¹ with higher contents in topsoil than subsoil. The majority of copper (42–82%) was bound to soil organic matter. In all fractions, copper contents were up to 2-fold higher in organic than in conventional vineyards, whereas the sediment concentrations were independent of the adjacent viticultural management. A net increase of copper in downstream sediments was found only when water-extractable organic carbon (WEOC) in an adjacent vineyard was elevated. With 11 ± 1 mg kg⁻¹, total uranium was 25% higher in conventional than in organic vineyard soils. Its affinity to iron or WEOC potentially rendered uranium mobile leading to a substantial discharge to downstream sediments.ConclusionsTranslocation of copper and uranium from vineyards into adjacent stream sediments may rather be attributed to WEOC and iron contents than the viticultural management. Follow-up studies should scrutinize the processes driving metal availability and transport as well as their interaction at the aquatic–terrestrial interface.
3. JPCA

   Influence of Organic Chemicals on Water Molecule Bridges in Soil Organic Matter of a Sapric Histosol

   Pavel Ondruch, Jiri Kucerik, Zacharias Steinmetz, and Gabriele E. Schaumann

   The Journal of Physical Chemistry A 121(12), 2367–2376, 2017

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   Water molecules in soil organic matter (SOM) can form clusters bridging neighboring molecular segments (water molecule bridges, WaMBs). WaMBs are hypothesized to enhance the physical entrapment of organic chemicals and to control the rigidity of the SOM supramolecular structure. However, the understanding of WaMBs dynamics in SOM is still limited. We investigated the relation between WaMBs stability and the physicochemical properties of their environment by treating a sapric histosol with various solvents and organic chemicals. On the basis of predictions from molecular modeling, we hypothesized that the stability of WaMBs, measured by differential scanning calorimetry, increases with the decreasing ability of a chemical to interact with water molecules of the WaMBs. The interaction ability between WaMBs and the chemicals was characterized by linear solvation energy relationships. The WaMBs stability in solvent-treated samples was found to decrease with increasing ability of a solvent to undergo H-donor/acceptor interactions. Spiking with an organic chemical stabilized (naphthalene) or destabilized (phenol) the WaMBs. The WaMBs stability and matrix rigidity were generally reduced strongly and quickly when hydrophilic chemicals entered the soil. The physicochemical aging following this destabilization is slow but leads to successive WaMBs stabilization and matrix stiffening.

2016

1. STOTEN

   Plastic mulching in agriculture. Trading short-term agronomic benefits for long-term soil degradation?

   Zacharias Steinmetz, Claudia Wollmann, Miriam Schaefer, Christian Buchmann, Jan David, Josephine Tröger, Katherine Muñoz, Oliver Frör, and Gabriele E. Schaumann

   Science of The Total Environment 550, 690–705, 2016

   Abstract DOI Request PDF

   Plastic mulching has become a globally applied agricultural practice for its instant economic benefits such as higher yields, earlier harvests, improved fruit quality and increased water-use efficiency. However, knowledge of the sustainability of plastic mulching remains vague in terms of both an environmental and agronomic perspective. This review critically discusses the current understanding of the environmental impact of plastic mulch use by linking knowledge of agricultural benefits and research on the life cycle of plastic mulches with direct and indirect implications for long-term soil quality and ecosystem services. Adverse effects may arise from plastic additives, enhanced pesticide runoff and plastic residues likely to fragment into microplastics but remaining chemically intact and accumulating in soil where they can successively sorb agrochemicals. The quantification of microplastics in soil remains challenging due to the lack of appropriate analytical techniques. The cost and effort of recovering and recycling used mulching films may offset the aforementioned benefits in the long term. However, comparative and long-term agronomic assessments have not yet been conducted. Furthermore, plastic mulches have the potential to alter soil quality by shifting the edaphic biocoenosis (e.g. towards mycotoxigenic fungi), accelerate C/N metabolism eventually depleting soil organic matter stocks, increase soil water repellency and favour the release of greenhouse gases. A substantial process understanding of the interactions between the soil microclimate, water supply and biological activity under plastic mulches is still lacking but required to estimate potential risks for long-term soil quality. Currently, farmers mostly base their decision to apply plastic mulches rather on expected short-term benefits than on the consideration of long-term consequences. Future interdisciplinary research should therefore gain a deeper understanding of the incentives for farmers and public perception from both a psychological and economic perspective in order to develop new support strategies for the transition into a more environment-friendly food production.

2015

1. JPNSS

   The seasonal influence of olive mill wastewater applications on an orchard soil under semi-arid conditions

   Zacharias Steinmetz, Markus Peter Kurtz, Arnon Dag, Isaac Zipori, and Gabriele E. Schaumann

   Journal of Plant Nutrition and Soil Science 178(4), 641–648, 2015

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   Olive oil production generates large amounts of olive mill wastewater (OMW). OMW has a high nutrient content and could serve as fertilizer, but its fatty and phenolic constituents induce soil water repellency, phytotoxicity, and acidification. An appropriate season of OMW application may mitigate negative consequences while preserving beneficial effects. In order to investigate this, a field study was conducted, in which OMW was applied to an olive orchard in Israel either in winter or summer. Soil–water interactions (water drop penetration time, hydraulic conductivity), soil physicochemical parameters, phenolic compounds, and soil biological activity (bait-lamina test) were determined 12 to 18 months after OMW application. The results showed elevated K⁺ contents in all treatments, but all other soil properties of winter treatments were comparable to the control, which suggested a certain recovery potential of the soil when OMW is applied in winter. By contrast, summer treatments revealed a ten-fold higher soil water repellency, a three-times lower biological activity, and a four-fold higher content of phenolic compounds, independently of whether the soil was kept moist by irrigation or not. Thus, the OMW constituents were neither degraded nor leached by winter rain when applied during the hot season. Further research is needed to distinguish leaching and biodegradation effects, and to understand the development of the composition and degradation kinetics of organic OMW constituents.

2020

1. BvBoden

   (Mikro-)Plastik im Boden

   Elke Brandes, Melanie Braun, Matthias C. Rillig, Eva F. Leifheit, Zacharias Steinmetz, Peter Fiener, and Daniela Thomas

   Bodenschutz 3, 121–125, 2020

   Abstract DOI Request PDF

   Die (Mikro-)Plastikbelastung in Böden rückt zunehmend in den öffentlichen Fokus, aber die Datenbasis zu diesem Thema ist noch wenig belastbar. Über die Bedeutung der verschiedenen Eintragsquellen und -pfade liegen bis heute hauptsächlich Annahmen vor. Notwendige Voraussetzung für die Entwicklung von Vermeidungsstrategien ist ein besseres Systemverständnis der Mikroplastikbelastung und der Auswirkung auf Ökosystemfunktionen. Für weitere interdisziplinäre Forschung im Bereich der Datenerhebung und Modellierung besteht daher dringender Bedarf.

2016

1. DIV

   Soil based wastewater treatment - Effective Utilization of Olive Mill Wastewater in Israel and Palestine

   Markus Peter Kurtz, Nisreen Tamimi, Christian Buchmann, Zacharias Steinmetz, Yonatan Keren, Benjamin Peikert, Mikhail Borisover, Dörte Diehl, Amer Marei, Jawad Hasan Shoqeir, Isaac Zipori, Arnon Dag, and Gabriele Ellen Schaumann

   Water Solutions 157, 82–86, 2016

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   Cultivated since ancient times, the olive tree is native to Israel and the Palestinian Authority. Around 375 olive mills in the region are operated by a three phase continuous centrifugation process which yields pomace, olive oil and olive mill wastewater (OMW). The Project “Wastewater from Olive Oil Mills in Israel and Palestine: Interactions with Soil, Organic Contaminants and Mechanisms of Incorporation into Soil.” (DFG: SCHA 849/13) investigates locational and seasonal dependent application scenarios of OMW to soil. The general objective is to understand processes and mechanisms of OMW-soil interaction affecting soil quality and their temporal dynamics in order to optimize OMW soil application for minimal negative effects.

2021

1. SETAC

   Screening for Plastic Debris in Agricultural Soil — an Open Data Approach

   Zacharias Steinmetz, Paul Löffler, Katherine Muñoz, and Gabriele E. Schaumann

   SETAC North America 42nd Annual Meeting, 2021

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   The use of agricultural plastic covers offers increased yields and an improved crop quality. The most applied materials are polyethylene (PE) films and polypropylene (PP) fleeces. Although made to last for up to five years, parts of these covers are suspected of breaking down into smaller debris due to physical stress and may thereby contribute to soil contamination with microplastics. To scrutinize this, we randomly sampled 240 topsoil cores (0–5 cm) from eight fields covered with fleece, perforated foil, and/or plastic mulch. Samples from the field periphery (50 m perimeter) served as reference. Visual plastic debris >2 mm were analyzed by FTIR–ATR and identified using the Open Specy library. Smaller plastic debris were dispersed from 50 g of fine soil (≤2 mm) using sodium hexametaphosphate solution and density-separated with saturated NaCl solution. The collected PE, PP, and polystyrene (PS) debris were selectively dissolved in a 1:1-mixture of 1,2,4-trichlorobenzene and p-xylene at 150 °C, quantified by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), and evaluated with OpenChrom and R statistical software (all data will be made publicly available upon submission of the manuscript preprint). We counted eight PE and PS fragments >2 mm in two out of eight fields. By contrast, Py-GC/MS analysis revealed PE, PP, and PS contents >1 µg g^–1 in seven fields (18% of all samples). PE and PP levels of up to 7 µg g^–1 were probably associated with the use of thinner and less durable perforated films or fleeces. This was most pronounced at field edges where agricultural covers are typically turned and weighted down with soil or sandbags. On one site, we observed expanded PS particles >2 mm that concurred with elevated PS levels (8–19 µg g^–1) in the fine soil; but their source remained unresolved. In addition, the extent to which increased PE contents of up to 7 µg g^–1 in the field periphery may be attributed to wind drift of plastic covers or other, external sources needs to be addressed in future studies.

2020

1. SETAC

   Solve it! Using 1,2,4-trichlorobenzene and p-xylene to make polyolefin plastic debris amenable to pyrolysis-GC/MS quantification in soil

   Zacharias Steinmetz, Aaron Kintzi, Katherine Muñoz, and Gabriele E. Schaumann

   SETAC SciCon, 2020

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   The majority of plastic is produced, used and disposed of on land, where it probably disintegrates into debris smaller than 5 mm, so-called microplastics. Until now, the lack of adequate analytical methods for the quantification of plastic debris in soil has challenged a better understanding of their occurrence and fate in the terrestrial environment. We recently developed a simple and fast method for the quantification of polyethylene (PE) and polypropylene (PP) in soil using pyrolysis-GC/MS. In order to facilitate the preparation of calibration series and to better account for the heterogeneity of soil matrix, polymers were dissolved in 1,2,4-trichlorobenzene at 120 °C. However, it was not resolved if the method was applicable to all types of PE and PP, for example with cross-linking or molar weights deviating from the initially tested analytical standards. With this follow-up study, we aimed to optimize PE and PP dissolution while further reducing matrix interferences from soil. To this end, we tested a 1:1 mixture of 1,2,4-trichlorobenzene (TCB) and p-xylene at 150 °C for its efficiency to dissolve a variety of different PE and PP samples. Calibration series (5–200 µg g^–1) were prepared in the same solvent mixture. In addition, dispersive solid phase extraction (dSPE) was evaluated for its potential to reduce interfering matrix components from reference soils. Unlike TCB at 120 °C, the TCB/p-xylene mixture dissolved all tested plastic samples and solutions remained stable at room temperature. Calibration series in TCB/p-xylene responded linearly (adj. R² ≥ 0.995) with LODs of 5.7 and 3.3 µg mL^–1 for PE and PP, respectively. Whereas matrix-induced background levels were close to the LOD of PP, reference soils without any plastic addition produced a PE equivalent of 57–145 µg g^–1. The dSPE cleanup reduced matrix interferences by 23–45 %. Further method development is crucial to optimize dSPE for subsequent recovery and spiking experiments. Once ready, this approach may have the potential for routine analyses and screening studies of agricultural systems.

2019

1. SETAC

   Microplastic Analysis Goes Nano—Quantifizierung von Polyethylen, Polypropylen und Polystyrol im Nanogrammbereich

   Zacharias Steinmetz, Aaron Kintzi, Katherine Muñoz, and Gabriele E. Schaumann

   SETAC GLB, 2019

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   Um die Umweltbelastung durch Mikroplastik und dessen Schicksal besser charakterisieren zu können, benötigt es geeignete analytische Methoden. Während bisherige mikrospektroskopische Verfahren wie Fourier-Transform-Infrarotspektroskopie und Raman-Spektroskopie eine aufwendige Probenvorbereitung erfordern und anfällig für falsch positive Ergebnisse sind, mangelt es thermoanalytischen Ansätzen wie Thermogravimetrie/Massenspektrometrie (TGA/MS) oder Thermodesorptionsgaschromatographie mit Massenspektrometriekopplung (TED-GC/MS) bisweilen an einer ausreichenden Sensitivität, um Mikro- oder Nanoplastik in umweltrelevanten Konzentrationen detektieren zu können. Ziel dieser Studie war es daher, eine einfache und robuste Methode zur Quantifizierung von Polyethylen (PE), Polypropylen (PP) und Polystyrol (PS) mit möglichst niedrigen Nachweisgrenzen (LODs) zu entwickeln und zu validieren. Dazu wurden PE, PP und PS als Einzelsubstanzen und in Mischung bei 120 °C in 1,2,4-Trichlorbenzol gelöst und auf Standardkonzentrationen von 5–150 μg/mL verdünnt. Je 2 μL der Standards wurden per online Pyrolyse-GC/MS bei 750 °C für 15 s pyrolysiert und die Pyrolysate chromatographisch aufgetrennt (30 m DB-5, 40–300 °C bei 8 °C/min, Messzeit: 50 min). Zur Quantifizierung von PE eignete sich das Pyrolysat 1,16-Heptadecadien am besten (m/z 82, 95; adj. R² = 0.998; LOD = 2.5 μg/mL). Das spezifischste PP-Pyrolysat war 2,4-Dimethyl-1-hepten (m/z 70, 126; adj. R² = 0.997; LOD = 43.2 μg/mL). PS wurde über α-Methylstyrol quantifiziert (m/z 103, 118; adj. R² = 0.999; LOD = 1.6 μg/mL). Daraus ergeben sich absolute LODs von 3–86 ng. Ferner unterschieden sich die Peakintensitäten der Pyrolysate nicht signifikant voneinander, wenn die Polymere einzeln oder in Mischung gemessen wurden. Die relativen Standardabweichungen einer Messreihe (n = 10) betrugen 3 %, 4% und 7 % für 1,16-Heptadecadien, α-Methylstyrol und 2,4-Dimethyl-1-hepten. Unsere Ergebnisse legen nahe, dass die Verwendung von 1,2,4-Trichlorbenzol als Lösungsmittel mit anschließender Pyrolyse-GC/MS eine vielversprechende Methode zur selektiven Quantifizierung von PE, PP und PS darstellt. In Folgestudien soll untersucht werden, ob sich dieser Ansatz mit entsprechenden Extraktionsmethoden kombinieren lässt, um Mikro- und Nanoplastik auch in komplexen Umweltmatrizes, wie Boden, Sediment oder Fäzes quantifizieren zu können.

2021

1. BEW

   Nachweis von Mikroplastik im Boden – Probenahme, Aufbereitung, Quantifizierung

   Zacharias Steinmetz

   BEW Online Training (Mikro-)Plastik in Böden – Aktuelles Wissen und Herausforderungen, 2021

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2019

1. Cusanuswerk

   Back to the Roots. Haben unsere Böden ein Plastikproblem?

   Zacharias Steinmetz

   Fachschaftstagung Biologie/Chemie des Cusanuswerks, 2019

   Abstract Request PDF

   Gigantische Müllstrudel in den Weltmeeren, Fischmägen voller Plastikteile und tonnenweise Mikroplastik in der Schlei—Wissenschaft und Medien schauen beim Thema Plastikmüll vor allem ins Wasser. Doch wo kommen die rund 300 Mio. Tonnen jährlich weltweit neu produzierten Plastiks her und welchen Weg geht der unsachgemäß entsorgte Teil ehe er in die Weltmeere gelangt? Neben dem achtlosen Wegwerfen von Plastikmüll werden derzeit unter anderem Reifenabrieb, Klärschlamm, Kompostdünger und landwirtschaftliche Plastikfolien als mögliche Quellen für Plastik in der Umwelt diskutiert. Durch physikalische und chemische Verwitterung zerfallen größere Plastikfragmente in kleineres Mikro- vielleicht sogar Nanoplastik. Wind und Wetter verteilen sie bis in die entlegensten Gebiete. Im Boden wird Mikroplastik möglicherweise durch Regenwürmer in tiefere Erdschichten verfrachtet und in organische Bodensubstanz, den Humus, eingebaut. Altert Plastik im Boden, könnten sich Biofilme darauf bilden, wodurch die Partikel immer schwerer von ihrer natürlichen Umgebung zu unterscheiden sind. Mitunter lösen sich darüber hinaus in der Polymerstruktur enthaltene Schad- und Beistoffe und werden ins Boden- und Grundwasser ausgewaschen. Noch aber ist unklar, wie viel Plastik in unseren Böden schlummert, wie es sich dort verhält und welchen Einfluss es auf im Boden lebende Organismen hat. Schätzungen gehen davon aus, dass allein in Europa jährlich 63.000–430.000 Tonnen Plastik in landwirtschaftliche Böden gelangen. Erste Feldstudien finden bis zu 55 mg kg^–1 oder 0.3–600 Plastikpartikel pro Kilogramm Boden. Die große Unsicherheit in diesen Daten liegt nicht zuletzt am komplexen Gefüge Boden, das eine schnelle und einfache Quantifizierung des darin enthaltenen Plastiks erschwert. Analytische Methoden befinden sich derzeit in der Entwicklung und sind noch nicht standardisiert. Besondere Beachtung verdienen hier thermoanalytische Verfahren, wie die Pyrolyse–Gaschromatographie/Massenspektrometrie, die Plastikpartikel bei Temperaturen über 600 °C zersetzt. Über die dabei entstehenden Zersetzungsprodukte kann auf die Art des Plastiks und dessen Gehalt einer Umweltprobe zurückgeschlossen werden. Aufschluss über Form, Größe und Oberflächenbeschaffenheit der Partikel geben komplementär dazu optische Verfahren, wie Infrarot- und Ramanspektroskopie. Allerdings verlangen diese meist eine aufwendige Aufreinigung der Probe.
2. S-prep

   Quantifizierung von Mikroplastik in Bodenproben

   Zacharias Steinmetz

   S-prep Anwenderseminar Pyrolyse und Thermodesorption als Probenzuführung für die GC und GC/MS, 2019

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2021

1. NADC

   Professioneller Textsatz mit Latex

   Zacharias Steinmetz

   Nachrichten aus der Chemie 69(5), 30–33, 2021

   Abstract DOI Request PDF

   Das Textsatzsystem Latex fristet ein Nischendasein — zu unrecht. Einmal in die Syntax eingearbeitet, hilft es nicht nur beim korrekten Setzen von Formeln und Einheiten. Mit Paketen wie chemmacros und chemfig stehen zudem Werkzeuge zur Verfügung, um Reaktionsgleichungen und Strukturformeln zu erstellen.

2020

1. c’t

   Chemiebaukasten—Chemische Formeln und Reaktionsgleichungen in LaTeX

   Zacharias Steinmetz

   c’t 22, 160–163, 2020

   Abstract HTML Request PDF

   Wenn bei einem technischen Bericht oder einer Studienarbeit Chemie ins Spiel kommt, stoßen klassische Textverarbeitungs-programme an ihre Grenzen. Dagegen können Sie mit LaTeX chemische Notationen mit einfachen Kommandos direkt im Dokument erzeugen.

2019

1. c’t

   In Form gegossen—Anspruchsvolle Texte mit LaTeX schreiben und gestalten

   Zacharias Steinmetz

   c’t 9, 152–157, 2019

   Abstract HTML Request PDF

   Bislang ist der Umgang mit TeX und LaTeX vor allem im akademischen Bereich populär. Dabei geht damit jedwede Schreibarbeit bereits nach kurzer Einarbeitung leicht von der Hand und liefert selbst für komplexe Schriftstücke stets das gewünschte Layout.