SSS7.4 | Plastic in arable soils - where do we stand?
EDI
Plastic in arable soils - where do we stand?
Convener: Peter Fiener | Co-conveners: Melanie Braun, John Quinton, Florian Wilken
Orals
| Fri, 28 Apr, 14:00–15:45 (CEST)
 
Room K2
Posters on site
| Attendance Fri, 28 Apr, 16:15–18:00 (CEST)
 
Hall X3
Posters virtual
| Attendance Fri, 28 Apr, 16:15–18:00 (CEST)
 
vHall SSS
Orals |
Fri, 14:00
Fri, 16:15
Fri, 16:15
There is a steadily growing scientific and public concern regarding macro-, micro- and nanoplastic accumulation in arable soils. This is mirrored in a substantial increase of scientific publications over the past 3 to 4 years. However, the soil plastic research is still in its infancy, with more questions unanswered than answered. Overall, still little is known about plastic accumulation, degradation, losses, and the potential effects of plastic particles of different size on soil fertility, soil health and generally soil properties. This is partly associated with substantial difficulties to identify and quantify, especially micro- and nanoplastic mixed into the soil matrix.
The intention of this session is to bring together scientists working on different aspects of plastic contamination of soils. Highly welcome are studies dealing with analytical techniques, input and output pathways, degradation of plastic in soils, eco-toxicology effects, and potential mitigation approaches.

Orals: Fri, 28 Apr | Room K2

Chairpersons: Peter Fiener, Melanie Braun, John Quinton
14:00–14:05
14:05–14:15
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EGU23-13873
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ECS
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On-site presentation
Quynh Nhu Phan Le, Crispin Halsall, Stoyana Peneva, Olivia Wridley, Wulf Amelung, Melanie Braun, John Quinton, and Ben Surridge

Fluorescence microscopy utilising Nile Red staining was applied and tested to analyse microplastic particles in soil. Given a large number of analytical methods for measuring plastic particles in environmental and biological matrices, often utilising microscopy/spectroscopy approaches, efforts were made to validate this method for a range of soils and different microplastic (MP) particle types (varying size and morphology).  Eight MP types (including both non-biodegradable and biodegradable plastics) within three size categories (dia. 500-1000 µm, 100-250 µm and 10-150 µm) were spiked into three different agricultural soils (loam-reference soil, clay, and sandy soils) for a comprehensive assessment of the fluorescence microscopy methodology. Each soil (with replicates) was subject to digestion, density separation and filtration (with Nile Red staining) prior to analysis using fluorescence microscopy (GFP filter set, excitation/emission 470/525 nm) and bright filed microscopy for black microplastics. As a tool to shorten the analysis time, a digital image analysis pipeline using Image J was developed, allowing fully automated particle recognition and quantification of MPs in the samples. The main steps for image analysis, including background correction, fluorescent intensity thresholding, watershed segmentation and particle analysis, were optimised, the validation of which showed high accuracy (88% match to true observation) for MP particles on a filter without a soil matrix. To avoid false positive results due to the presence of natural organic particles from the soil matrix, the numbers of microplastics recovered from spiked samples were corrected with those found in the non-spiked soils. Recoveries ranged from 80-90% for MP with sizes from 500-1000 µm regardless of the soil types, whereas those for smaller MP (10-250 µm) varied between different soils and plastic types (e.g., recovery for low-density polyethylene, LDPE, from sand and loam-reference soil were 85% and 90% respectively whereas those for polybutylene adipate terephthalate/polylactic acid, PBAT/PLA, were 60% and 10% respectively). The lowest recovery rates were observed in clayey soil (20% for LDPE and 5% for biodegradable plastics PBAT/PLA). A relationship between the microplastic mass (LDPE and PBAT/PLA fragments) and the corresponding particle number was established in this study, which enabled the conversion between mass and particle number data. Fluorescence microscopy with Nile Red staining and automatic particle recognition software provides a relatively reproducible and accurate technique for plastic particle counts in heterogeneous matrices like soil. Still, selectivity for different polymer types is clearly limited. 

How to cite: Phan Le, Q. N., Halsall, C., Peneva, S., Wridley, O., Amelung, W., Braun, M., Quinton, J., and Surridge, B.: Towards quality-assured measurements of microplastics in soils using fluorescence microscopy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13873, https://doi.org/10.5194/egusphere-egu23-13873, 2023.

14:15–14:25
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EGU23-4315
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ECS
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On-site presentation
Tabea Scheiterlein and Peter Fiener

In Europe, about 0.71 million tonnes of agricultural plastic were intentionally used in 2019. Most widely used were plastic films (about 75%), which are dominated by light density polyethylene (LDPE). Especially LDPE plastic films for mulching covers in direct contact arable soil to increase temperature and reduce evaporation. Thereby, microplastic is detached from the mulch film via mechanical and environmental weathering. Another microplastic pathway in arable soil is the application of sewage sludge. Depending on land use, a 4 to 23 times higher microplastic contamination in soils than in the sea is estimated. Obviously, microplastic input to soils is critically high, but an accurate quantification is still lacking. This is partly caused by challenges in detection and analysis of microplastic in soils. First, it is challenging to extract microplastic from a matrix of organic and inorganic particles of similar size. Second, the well-established spectroscopic methods (e.g., Raman and FTIR) for detecting microplastics in water samples are sensitive to soil organic matter, and they are very time-consuming. Eliminating very stable organic particles (e.g., lignin) from soil samples without affecting the microplastic to be measured is another challenge. Hence, a robust analytical approach to detect microplastic in soils is needed. In this context, we developed a methodological approach that is based on a high-throughput (25 g soil sample) density separation scheme for measurements in a 3D Laser Scanning Confocal Microscope (Keyence VK-X1000, Japan) and subsequently using a Machine-Learning algorithm to classify and analyze microplastic in soil samples. Our aim is to develop a method for a fast screening of microplastic particle numbers in soils while avoiding the use of harmful substances (e.g., ZnCl2) or prolonged organic carbon destruction. For method development, we contaminate a standard soil (LUFA type 2.1 - sand: 86.6% sand, 9.7% silt, 3.7% clay, 0.58% organic carbon; and LUFA type 2.2 - loamy sand: 72.6% sand, 16.8% silt, 10.7% clay, 1.72% organic carbon) with different concentrations of transparent LDPE microplastic (< 700 µm), LDPE microplastic originating from black mulch film (< 400 µm) and microplastic originating from Bio-degraded black mulch film (< 250 µm). For density separation, three non-toxic, easy to handle mediums were compared for the best microplastic output: distilled water (ρ = 1.0 g/cm3), 26% NaCl solution (ρ = 1.2 g/cm3), and 41% CaCl2 solution (ρ = 1.4 g/cm3). The separated microplastic plus organic particles and some small mineral particles were scanned using a 3D Laser Scanning Confocal Microscope. For each sample, the 3D Laser Scanning Confocal Microscope generates three different main outputs: color, laser intensity, and surface characteristics. Based on these data outputs, a Machine-Learning algorithm distinguishes between the mineral, organic, and microplastic particles. It was found that color changes of microplastics due to soil contact challenge the classification but can be compensated by surface characteristics that become an essential input parameter for the detection. The presented methodological approach provides an accurate and high-throughput microplastic assessment in soil systems, which is critically needed to understand the boundaries of sustainable plastic application in agriculture.

How to cite: Scheiterlein, T. and Fiener, P.: Microplastic detection in arable soil using a 3D Laser Scanning Confocal Microscope coupled with a Machine-Learning Algorithm, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4315, https://doi.org/10.5194/egusphere-egu23-4315, 2023.

14:25–14:35
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EGU23-9039
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ECS
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On-site presentation
Charlie Monkley, Michaela Reay, Richard Evershed, and Charlotte Lloyd

Plastic is a prominent material finding growing use globally within agricultural supply chains, through cultivational practices to product packaging. Mulch film is one such ‘plasticulture’ application where opaque film is stretched over the soil surface to maintain a humid microclimate at the crops / fruits soil-root zone as well as protecting ungerminated seeds and small crops from pests. However, mulch film represents an unregulated chemical input source to agroecosystems, whose ecotoxicological legacy is yet to be assessed. The first step in addressing this issue is characterising the chemical content of the source material that may later be released. Amidst the polymeric base, manufacturers include a diverse multitude of chemical additives into plastic formulations to aid with manufacturing, improve functionality, retard degradation and alter aesthetics. In most cases, additives are not chemically but physically bound to the polymeric matrix meaning over time they are free to migrate and be released to the surrounding agroecosystem. Once released, these chemicals may cycle between compartments, interacting with biota or entering the food chain through uptake by plant life or livestock. To trace the extend of release and subsequent interaction of chemical additives within ecosystems, the formulation of the film must be determined. An untargeted characterisation approach has to be adopted, as additive packages remain confidential as property of the manufacturers. Microwave assisted solvent extraction and dissolution-precipitation have been implemented for two agriplastic mulch films: synthetic low density polyethylene (LDPE) and biodegradable polylactic acid (PLA; 15 %) / polybutyrate adipateterephthalate (PBAT; 85 %) blend. Extracts were analysed by GC-MS and spectral libraries used to characterise the leachable content of the films. Alternatively, thermal desorption of the additives from the polymeric base and subsequent analysis of the volatiles through py-GC/MS allows for rapid screening of low molecular weight species, with the caveat of loss in quantification accuracy. An array of chemicals have been identified including: plasticisers (phthalates, citrates, adipates), slip agents (fatty amides), antioxidants (hindered phosphates, hindered phenols), antistatics (fatty esters), lubricants (fatty alcohols, alkanes) and transformation products of both additives and polymer. Additive characterisation work is complimented by confirmation of the mulches polymeric compositions or revelation of unreported polymeric components, through techniques such as fourier transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance (NMR). Later investigation seeks to understand the transformation, cycling and fate of these additive targets within agroecosystems at predicted release levels, which are based on leaching studies into water and in-field measurements.

How to cite: Monkley, C., Reay, M., Evershed, R., and Lloyd, C.: Characterising the Chemical Additive Content of Agricultural Plastic Mulch Film, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9039, https://doi.org/10.5194/egusphere-egu23-9039, 2023.

14:35–14:45
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EGU23-77
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ECS
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Highlight
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On-site presentation
Spatial and temporal variance of microplastics in agricultural soils
(withdrawn)
Collin J. Weber, Jan-Eric Bastijans, and Christian Heller
14:45–14:55
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EGU23-13542
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ECS
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Highlight
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On-site presentation
Silvan Arn, Flora Wille, Mattia Cerri, Ralf Kägi, Thomas Bucheli, Franco Widmer, Kristopher McNeill, and Michael Sander

Non-biodegradable polyethylene mulch films are widely used in agriculture to allow for an extended growing season and to increase crop yields. These mulch films are, however, difficult to completely recollect from the field after use, particularly when they are thin (< 25 µm). Residual mulch film pieces can accumulate in soils over time, thereby negatively impacting soil productivity and possibly turning agricultural soils into sources of plastics to surrounding environments. Mulch films certified as biodegradable in soils promise to be a solution to these problems. While such mulch films are already commercially available, a thorough assessment of the biodegradation dynamics of biodegradable mulch film products in soils in the field is lacking. So far, certification relies exclusively on laboratory soil incubations coupled to respirometric analysis of CO2 formed from the mulch films during biodegradation. Respirometric analyses are, however, very challenging to implement in field incubation studies. Past studies determining concentrations of biodegradable mulch films in field soils and attempts to follow their biodegradation dynamics in the field have relied on approximate quantification approaches, such as determining the decrease in surface area or gravimetric mass of film pieces recollected by hand. To advance a more robust and quantitative analytical approach for residual mulch film quantification in soils, we present a methodology to solvent extract and quantify the main synthetic polymeric components of commercial biodegradable mulch films, poly(butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA), from soil. The methodology is based on exhaustive Soxhlet extraction using chloroform/methanol coupled to quantitative 1H-NMR of the extracted residual PBAT and PLA. We show full recovery of these polymers added to soils in spike-recovery experiments. Here, we use this approach to assess the biodegradation of two commercial biodegradable mulch films in three Swiss agricultural soils in a multiyear incubation study. These incubations are conducted at three experimental incubation scales: flasks in the laboratory, mesocosms in a greenhouse and the actual field. We statistically compare biodegradation rates and extents between three soils, two tested films across the three incubation scales, as well as differences in the relative rates of biodegradation between PBAT and PLA. Thereby, we assess the transferability of biodegradation results from laboratory incubations to field incubations. Our results highlight variations in biodegradation between soils and polyesters and indicate that laboratory soil incubations show faster biodegradation than measured in the same soil in the field.

How to cite: Arn, S., Wille, F., Cerri, M., Kägi, R., Bucheli, T., Widmer, F., McNeill, K., and Sander, M.: Biodegradation of commercial mulch films in Swiss agricultural soils: Results from combined laboratory, mesocosm and field incubations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13542, https://doi.org/10.5194/egusphere-egu23-13542, 2023.

14:55–15:05
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EGU23-5406
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ECS
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Highlight
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On-site presentation
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Wang Li, Saunak Sinha Ray, Emilee Severe, David Zumr, Tomáš Dostál, Josef Krasa, Florian Wilken, John N. Quinton, Ahsan Maqbool, Jos ́e Alfonso G ́omez, and Christine Stumpp

Microplastic pollution in agricultural sites has gained increased attention in recent years. Many studies focused on the impact of plastic residues on soil functions, such as soil physiochemical properties, fertility, and biodiversity. However, research on the transport behavior of microplastics (MPs) in agricultural soil remains rare. Therefore, it is important to understand the transport mechanism of MPs in the natural environment. Plot experiments (1x1 m) were conducted in an agricultural site (silty loam) near Prague to investigate the size-dependent movement of MPs under both artificial irrigation (first campaign) and natural rainfall (second campaign). Before irrigation, fluorescent PE microspheres with four different size ranges (53-63 µm, 125-150 µm, 250-300 µm, 425-500 µm) were mixed with soil and then uniformly distributed on the plot surface (upper 1 cm). Deuterium as a conservative tracer was added and well mixed with water for the rainfall simulation. The rainfall simulation with an intensity of 60 mm/h was applied. Results from the first campaign show that the maximum migration depth of MPs was up to 4-6 cm, which is consistent with the results from the tracer experiment. Moreover, larger particles were mostly found on the top layer up to 2 cm, with small MPs at 53-63 µm transported down to 6 cm. These results indicate that the infiltration of water could enhance the movement of MPs in the soil profile, with smaller MPs having higher mobility under rainfall simulation. This finding provides insight into the mobility of MPs in agricultural soils, and it could be applied for control and risk assessment to estimate the potential of MPs leaching into aquifer systems.

How to cite: Li, W., Ray, S. S., Severe, E., Zumr, D., Dostál, T., Krasa, J., Wilken, F., Quinton, J. N., Maqbool, A., G ́omez, J. ́. A., and Stumpp, C.: Vertical transport of microplastic in agricultural soil in controlled irrigation plot experiments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5406, https://doi.org/10.5194/egusphere-egu23-5406, 2023.

15:05–15:15
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EGU23-13713
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ECS
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On-site presentation
Emilee Severe, Ben Surridge, Rachel Platel, Michael Coogan, Michael James, Peter Fiener, and John Quinton

Microplastics are ubiquitous in the environment. While it is well documented that microplastics can be harmful to aquatic and terrestrial life, little is understood about how microplastics affect soil environments. Understanding the processes enhancing or constraining microplastic transport through the environment, including within soils, is essential in order to minimize the negative impacts of microplastic pollution. Soil erosion is thought to be a primary process responsible for translocating microplastics from soils to aquatic environments. This study aims to investigate the processes controlling microplastic movement in response to rainfall and overland flow in laboratory rainfall simulations. Using fluorescent photography, we compared the real- time movement of a natural soil particle, sand, with two types of microplastics of differing densities (linear low-density polyethylene and acrylic) in two size fractions (250-355 μm and 500-600 μm). We quantified the rate and number of microplastic particles transported by overland flow and splash erosion, along with the depth to which the particles migrate into the soil profile. The results from this study represent some of the first empirical data that seek to quantify microplastic surface transport processes. Ultimately, additional research in this area will be required to more accurately estimate the extent to which microplastics are exported from soils and the factors that control this export.

How to cite: Severe, E., Surridge, B., Platel, R., Coogan, M., James, M., Fiener, P., and Quinton, J.: Quantifying the movement of microplastics in soil in response to overland flow and splash erosion, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13713, https://doi.org/10.5194/egusphere-egu23-13713, 2023.

15:15–15:25
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EGU23-8848
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ECS
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On-site presentation
Michaela Reay, Lucy Greenfield, Martine Graf, Charlotte Lloyd, Richard Evershed, Dave Chadwick, and Davey Jones

Micro and macroplastics, produced from plastic mulch film and polytunnels, are contaminants of growing concern in agricultural settings. However, their impact on nitrogen (N) cycling and partitioning in plant-soil-microbial systems, critical to soil health and food security, is poorly understood. The differing impact of conventional plastics (e.g. low density polyethylene; LDPE) and emerging biodegradable plastics on microbially-mediated N transformations is also unclear, especially with accumulation over long timescales. In this mesocosm-scale study, spring barley (Hordeum vulgare L.) was exposed to macro (1 x 1 cm) or microplastic (< 500 μm) produced from LDPE or biodegradable (polylactic acid/polybutylene adipate terephthalate (PLA/PBAT); 15%/85% w/w) plastic mulch at concentrations equivalent to 1 (0.02%), 10 (0.2%) and 20 (0.4%; LDPE only) years of plastic mulch film use. Mesocosms were fertilised with ammonium nitrate (40 kg N ha−1, 20 atom%15N), and partitioning of 15N-labelled fertiliser into plant biomass, soil and leachate yielded a partial mass balance. Soil-N partitioning was probed via diffusion of extractable ammonium and nitrate, and compound-specific 15N-stable isotope analyses of soil microbial protein. Barley chlorophyll content and growth were used to determined effects on plant health. Plant health parameters were not effected by increasing concentrations of micro or macroplastic, however, there were concentration-dependent decreases in plant 15N uptake. This was linked to increased leached nitrogen for biodegradable and LDPE micro- and macroplastic, due to changes in physical pore flow pathways. This was also observed for total soil 15N, while varying patterns in soil 15N partitioning between plastic type, size and concentrations revealed potential complexities of impacts of N cycling for macro and microplastics. Assimilation into soil microbial protein was higher for biodegradable plastics, which we associate with early-stage degradation. Microbial assimilation in the presence of LDPE was a function of abiotic impacts on leaching, with suppression of inorganic N transformations. While micro- and macroplastics altered soil N cycling, the limited impacts on plant health indicated the threshold for negative effects was not reached at agriculturally relevant concentrations during early-stage barley growth. However, changes in soil N cycling and available N will impact nitrogen use efficiency and soil organic matter dynamics. Thus, the differing impacts of conventional and biodegradable macro and microplastics, and effects of accumulation, must be considered in risk assessments for agricultural plastics. 

How to cite: Reay, M., Greenfield, L., Graf, M., Lloyd, C., Evershed, R., Chadwick, D., and Jones, D.: LDPE and biodegradable plastics differentially affect plant-soil nitrogen partitioning and microbial uptake, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8848, https://doi.org/10.5194/egusphere-egu23-8848, 2023.

15:25–15:35
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EGU23-15971
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ECS
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Highlight
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On-site presentation
Sofia Barili, Alessandro Bernetti, Ciro Sannino, Nicolò Montegiovo, Eleonora Calzoni, Alessio Cesaretti, Irina Pinchuk, Daniela Pezzolla, Benedetta Turchetti, Pietro Buzzini, Giovanni Gigliotti, and Carla Emiliani

Microplastics are emerging pollutant found in many ecosystems including soil. Within them, polyvinyl chloride (PVC) is one of the most toxic polymers and is known for its remarkable resistance to degradation. The recalcitrant nature of PVC and the improper waste disposal could cause serious environmental concerns. In addition, the possible fragmentation and accumulation of small plastic particles in agricultural soils might have impacts on soil chemical and microbiological properties. Based on these considerations, a microcosm experiment was set up to investigate the effects of PVC microplastics (0.021% w/w) on soil chemical properties and soil bacterial and fungal communities at different incubation times (from 3 to 360 days).

Among chemical parameters, soil CO2 emissions, fluorescein diacetate hydrolysis (FDA), total organic C (TOC), total N, water extractable organic C (WEOC), water extractable N (WEN) and SUVA254 were investigated, while the structure of soil microbial communities was studied at different taxonomic levels (phylum and genus) by sequencing bacterial 16S and fungal ITS2 rDNA (Illumina MiSeq). The number and the dimensions of PVC particles were also evaluated after one year of experiment.

The results showed that the presence of PVC particles in soil caused significant (p < 0.05) variations in chemical parameters in short- and medium-term, thus suggesting that the presence of this polymer in soil can affect the turnover of organic matter. In the long period, instead, an increase of the soil enzymatic activity (FDA) was observed.

The analysis of microbiological parameters showed that PVC microplastics significantly affected (p < 0.05) the structure of soil microbial communities changing the abundances of specific bacterial and fungal taxa: Acidobacteria, Actinobacteria, Bacteroides, Candidatus_Saccharibacteria, and Proteobacteria, , among bacteria, and Ascomycota, Basidiomycota, and Mortierellomycota among fungi, suggesting that the impact of this polymer could be taxa-dependent.

A significant (p < 0.05) decrease of the number and dimensions of PVC particles was also detected after one year of incubation, supposing a possible role of microbial community on polymer degradation.

How to cite: Barili, S., Bernetti, A., Sannino, C., Montegiovo, N., Calzoni, E., Cesaretti, A., Pinchuk, I., Pezzolla, D., Turchetti, B., Buzzini, P., Gigliotti, G., and Emiliani, C.: Long term influences of PVC microplastics on soil chemical and microbiological parameters, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15971, https://doi.org/10.5194/egusphere-egu23-15971, 2023.

15:35–15:45
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EGU23-11465
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ECS
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On-site presentation
Giovana P. F. Macan, Manuel Anguita-Maeso, and Blanca B. Landa

Currently, plastic mulch debris represent one of the main sources of microplastic pollution in agricultural soils. However, there is still limited research on plastic and microorganisms' interaction in terrestrial agroecosystems as compared to marine ecosystems. In this study, we have characterized the microbial communities associated with agricultural plastic mulch debris by using culture-dependent, and culture-independent (i.e., high-throughput DNA sequencing) approaches. Weathered plastic mulch debris samples were collected from the topsoil of five agricultural fields in Baza, Granada province in southern Spain, characterized by intensive horticultural production over the last ten years. The bacterial communities from the plastisphere soil (soil tightly adhered to the plastic) as well as the community tightly attached to the plastic surface were assessed by estimating the culturable populations by dilution plating on general media and the total (culturable and non-culturable) populations by NGS analysis of 16S rRNA amplicons. Additionally, all the plastic samples were characterized by FTIR spectroscopy and identified as polyethylene. The results from the culturable approach showed a significantly higher number of colony-forming units in the plastisphere soil than on the plastic surface, revealing some differences among field plots. Furthermore, 16S rRNA amplicon sequencing showed that the bacterial alpha-diversity, as measured by Richness index was higher in the plastisphere soil. Beta diversity Weighted-UniFrac index indicated that the main significant differences in the bacterial communities occurred among field plots, which might be related to the soil type, and/or crop history, and a lower effect of the plastic niche sampled. Some genera such as Arthrobacter, Bacillus, Blastococcus, Kocuria, Nocardioides, Sphingomonas, and Streptomyces were present in high abundance on both plastisphere soil and plastic surface from all the assessed fields. Furthermore, in one of the fields, the genera Polycyclovorans and Bdellovibrio showed significantly higher abundance in the plastic surface than in the plastisphere soil, indicating in this case a selective effect of the plastic for specific bacterial genera. Further research is still needed to better understand the potential impacts of plastic pollution on terrestrial agroecosystems as well as the complex interaction between plastic and microorganisms.

“This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 955334 - SOPLAS.”

How to cite: Macan, G. P. F., Anguita-Maeso, M., and Landa, B. B.: Microbial communities associated with plastic mulch debris in agricultural soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11465, https://doi.org/10.5194/egusphere-egu23-11465, 2023.

Posters on site: Fri, 28 Apr, 16:15–18:00 | Hall X3

Chairpersons: Peter Fiener, Florian Wilken, Melanie Braun
X3.142
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EGU23-1626
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ECS
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Ahsan Maqbool and José Alfonso Gómez

Abstract

Microplastics (5mm) enter the soil in several ways, including directly through the purposeful use of plastic (e.g., in plastic mulch, greenhouses, or coated items) or inadvertently through the addition of sewage sludge, compost, or irrigation water that has been polluted with plastic. The effect of microplastic on plant growth, soil biota, and soil physicochemical properties has been reviewed (Shafea et al., 2022), while soil physical properties have yet to be synthesized. Soil structure is an important soil feature affecting key variables in earth system models like, e.g., soil aggregation and soil hydraulic properties (Fatichi et al., 2020). These soil physical properties are influenced by widespread microplastic dispersion and pervasiveness, which might affect the soil's capacity to provide different ecosystem services and is a potential obstacle to sustainable agriculture (Rillig & Lehmann, 2020). Thereby, we present the preliminary results of a review on the plastic and microplastic impact on soil physical properties, including soil compaction, soil aggregation, water retention and transmission, and porosity, from peer-reviewed publications. Our review indicates that increasing plastic and microplastic concentration reduces soil compaction due to changes in bulk density. Soil structure and aggregate stability are also subject to alteration due to plastic contamination. Microplastic in the soil might affect water repellency, mainly measured by water drop penetration time. However, data on hydraulic properties, thermal properties, and pore-size distribution are scant. Moreover, potential factors, i.e., plastic-type, size, concentration, and soil type, by which microplastic can influence soil physical properties, are also discussed. This communication tries to identify trends in the influence of plastic and microplastic among different treatments using different indexes. From this analysis, we identify knowledge gaps for future studies.

Keywords: agroecosystem, microplastic, soil aggregates, infiltration.

References

Fatichi, S., Or, D., Walko, R., Vereecken, H., Young, M. H., Ghezzehei, T. A., Hengl, T., Kollet, S., Agam, N., & Avissar, R. (2020). Soil structure is an important omission in Earth System Models. Nature Communications, 11(1), 522. https://doi.org/10.1038/s41467-020-14411-z

Rillig, M. C., & Lehmann, A. (2020). Microplastic in terrestrial ecosystems. Science, 368(6498), 1430–1431. https://doi.org/10.1126/science.abb5979

Shafea, L., Yap, J., Beriot, N., Felde, V. J. M. N. L., Okoffo, E. D., Enyoh, C. E., & Peth, S. (2022). Microplastics in agroecosystems: A review of effects on soil biota and key soil functions. Journal of Plant Nutrition and Soil Science. https://doi.org/10.1002/jpln.202200136

How to cite: Maqbool, A. and Gómez, J. A.: Does plastic and microplastic change the soil physical properties? A review, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1626, https://doi.org/10.5194/egusphere-egu23-1626, 2023.

X3.143
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EGU23-1899
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ECS
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Ana Carolina Cugler Moreira, Florian Wilken, Melanie Braun, and Peter Fiener

In modern agriculture, plastic material is intentionally used for different purposes. In 2020, it was estimated that about 7.1 105 t of plastic was used in European agriculture, whereas most plastic was applied in form of plastic mulch films to improve growing conditions, e.g., via temperature regulation or reduction of evaporation. Most of this plastic films are made from Light Density Polyethene (LDPE) with different physical (e.g., thickness between 15 and 200 µm) and chemical properties (e.g., different types and amounts of additives for UV stabilization). Plasticulture improves productivity but a growing number of studies indicate soil contamination with macro-, meso- and microplastic particles originating from plastic mulching films. The aim of this study is to compare the changes in plastic film properties and stability as basis for the fragmentation into meso- to microplastic following different environmental stressors applied to plastic films used for different purposes. A series of lab experiments was set-up to mimic natural UV radiation as well as mechanical stress. Overall, six different agricultural films were tested (two black LDPE mulch films, thickness 20 µm; two transparent LDPE films of small tunnels, thickness 180 µm; and two black-white LDPE asparagus mulch films, thickness 100 and 150 µm). In a first step, different UV light exposures time were used (Q-SUN Xe-1-SE xenon test chamber, TUV (300-400 nm)) to simulate LDPE aging as exposed to sunlight at the soil surface, in second step mechanical stress was applied during an abrasion test (20 g of standard soil were mixed with the degraded samples at 4 rpm for 61 days). Both treatments and their combinations were then analyzed regarding changes in plastic properties. Therefore, we used a 3d laser scanner confocal microscope (LSM) to analyze changes in plastic surfaces, a Fourier-transform infrared-attenuated total reflectance spectrometer (FTIR-ATR) to determine changes in the chemical compounds, an optical contact angle (OCA) to determine changes in hydrophobicity and finally tested changes in mechanical stability with a universal nanomechanical tester (UNAT). First results indicate that UV alone can affect the stability of the films, which is increased by mechanical stress. The FTIR-ATR spectra, especially from the thin black film, presented variation at the carbonyl band (1800-1600 cm-1) after the degradation test; LSM results for the degradation test didn’t show any significant change, while preliminary results from the mechanical stress present changes on its surface; for OCA preliminary results the thin black film showed a variation from 85.7o to 77.2o after UV degradation. Overall, the tests indicate the importance of a combination of UV radiation and mechanical stress for LDPE film degradation, which especially in case of the thin, black mulch film leads to a change in plastic properties paving the way for plastic fragmentation within months of environmental exposure, while the thicker foils are less affected within such timeframe. Hence, thin plastic mulching foils might improve agricultural productivity but on the cost of increasing soil plastic contamination.

How to cite: Cugler Moreira, A. C., Wilken, F., Braun, M., and Fiener, P.: From intentionally used plastic films to soil microplastic contamination, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1899, https://doi.org/10.5194/egusphere-egu23-1899, 2023.

X3.144
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EGU23-3220
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ECS
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Saunak Sinha Ray, David Zumr, and Tomas Dostal

Due to the ecological risk posed by plastic pollution, biodegradable plastics (BDPs) usage in agriculture has gained attention as an alternative to conventional plastics. However, agricultural soil remains a major reservoir of microplastics (MPs) in today’s global environment. Given the persistence of MPs, few studies have focused on the fate and transport of conventional MPs from agricultural topsoil. However, understanding the transport of biodegradable MPs is largely unknown. The aim of this study is to analyze the erosion and transport behavior of biodegradable polylactic acid (PLA) MPs (size 250 – 300 μm) under simulated heavy rainfall events on fallow and crusted agricultural soils. The experiment used fluorescent PLA filament to obtain the MPs. Based on the fluorescent property of the PLA MPs, a simple, reliable, and cost-effective method using darkroom photography under a 365nm UV lamp, and an Image J script was developed for quantification. The study was conducted on three plots (1m × 1m) of loamy soil at an agricultural field in the Czech Republic. A concentration of 4 g m-2 of PLA MPs was incorporated into the top 5 cm of the soil in each plot. Rainfall simulations with an intensity of 60 mm h-1 were carried out twice within one week in April 2022. The results showed a general depletion of biodegradable PLA MPs in the delivered sediment. Eroded sediments showed mean enrichment ratios of 0.59 ± 0.05 in the fallow plot and 1.45 ± 0.37 in the crusted plot. Higher MP enrichment and sediment delivery were observed on crusted soil compared to fallow soil, suggesting a more conservative erosion and transport for the latter. Overall, our study highlights that a relatively high-density biodegradable MP, such as PLA, tends to remain within the topsoil and is negligibly affected by rainfall-induced surface runoff and very low infiltration capacity.

How to cite: Sinha Ray, S., Zumr, D., and Dostal, T.: Transport of Polylactic Acid (PLA) Microplastics in Agricultural Soils under Simulated Rainfall Events - Analyzing Surface Water Runoff as an Environmental Pathway, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3220, https://doi.org/10.5194/egusphere-egu23-3220, 2023.

X3.145
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EGU23-4371
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ECS
Leila Shafea, Angelo Yoffre Rodriguez Carlos, Susanne Karoline Woche, Leopold Sauheitl, Marc-Oliver Göbel, and Stephan Peth

Comparing pristine microplastic (MP) to aged MP collected from the soil environment, aged MP particles generally have a rougher surface and thus a greater specific surface area, higher crystallinity, more oxygen-containing functional groups, and lower tensile strength, as well as greater mobility and consequently a higher risk of leaching into the groundwater [1, 2]. The aged MP is produced due to the solar UV irradiation and soil abiotic and biotic processes [3]. Thus, pristine and aged MP may behave differently in the environment due to different surface properties and MP extraction from soil consequently must ensure to recover both, pristine and aged MP. Therefore, we aimed to develop a fast and efficient laboratory method to detect pristine and aged MP and to compare the recovery rate of aged and pristine MP. For this purpose, an experiment was conducted by adding pristine and UV-aged (UV irradiation period: 35 d) MP particles of two different types, polyethylene terephthalate (PET) and polystyrene (PS), at three sizes (S: 500 µm, M: 500-630 µm, L: 630 µm -1mm) to sand and loess soil at a concentration of 0.5% w/w. For extraction, a density separation was performed, using saturated NaCl (1.2 g cm-3) and NaI (1.8 g cm- 3) solutions, followed by H2O2 (33 %) treatment to remove soil organic matter. Recovered MP was quantified gravimetrically. The physico-chemical properties of pristine and aged MP before and after extraction were analyzed by Mid-FTIR for changes in surface functional groups and by contact angle (CA) determination for changes in wetting properties due to aging. We found that the recovery rates of pristine and UV-aged particles were the same for both PS and PET, with no significant differences between recovery from sand and loess soils. The average recovery rate of all samples was about 81 %. Pristine MP was hydrophobic (CA≥90) while aged MP was subcritically water repellent (CA>0 and <90°). In line, FTIR spectra indicated the formation of hydroxyl groups (i.e., polar sites) in aged MP. FTIR spectra before and after recovery showed no significant differences, however, CA of aged MP (size L) was increased to >90° after recovery, probably due to amphiphilic organic matter (OM) compounds sorbed during extraction. In conclusion, the tested recovery procedure did work for pristine and aged MP at all size fractions and loess and sandy soils, while the extraction procedure seems to result in an interaction between polar sites and released OM in case of aged MP.

Keywords: Microplastic, Pristine, UV-aged, Recovery, Identification, Quantification.

[1] doi: 10.1016/j.scitotenv.2018.02.079. [2] doi: 10.1016/j.watres.2021.117407.117407.[3] doi: 10.1002/jpln.202200136.

How to cite: Shafea, L., Yoffre Rodriguez Carlos, A., Woche, S. K., Sauheitl, L., Göbel, M.-O., and Peth, S.: Effects of microplastic aging on its detectability and physico-chemical properties in loess and sandy soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4371, https://doi.org/10.5194/egusphere-egu23-4371, 2023.

X3.146
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EGU23-8476
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ECS
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Highlight
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Alessandro Fabrizi, Peter Fiener, Thomas Jagdhuber, Kristof Van Oost, and Florian Wilken

The use of plastic in agriculture (plasticulture) started together with the rise of plastic in global markets, around 1950. Nowadays, plastic plays a key role in agriculture as an inexpensive, lightweight and resistant material. In European vegetable production, around 80% of plastic use is attributed to plastic films for crop covers. While meeting the needs of both producers and consumers (e.g., higher yields, early harvest, availability of out-of-season products), serious concerns have been raised about end-of-life management of plastic films. Different management practices, crop and film types are potentially controlling the amount of macro- and microplastic residues that remain in soil. While part of the scientific studies is improving our understanding of the environmental risks of plasticulture, a tool to monitor and quantify its extent at large scale (e.g., regions up to countries) is still lacking. The presence of publicly and freely available satellite data with increasing temporal and spatial resolution, coupled with increasing computing capabilities, qualify satellite remote sensing as a potential data source for large scale plasticulture monitoring. The challenge of detecting plastic covered crops by satellite data stimulated a growing number of papers. However, most of the literature focuses on local plasticulture hotspots, while a few authors recently tried to identify either greenhouses or plastic mulched farmlands (PMF) at larger scale. To the best of our knowledge, no attempts have been made for large scale plasticulture mapping in regions where different types of plastic covers are present (PMF, tunnels and greenhouses).

In this research study we aim at identifying PMF, tunnels and greenhouses across Germany, one of the most active countries in the EU agricultural plastic film market. Google Earth Engine cloud computing capabilities were combined with Sentinel-1 and Sentinel-2 data coming from a whole year of acquisitions. In this context, time series analyses were supplied with a novel multi-image classification-based index (called Plastic Detection Frequency, PDF). The index was created by looping a random forest classifier over a yearly image collection to address the seasonality of temporary plastic covers (e.g., mulch foils, tunnels), which might not be caught by analysing time series with traditional methods alone. The results were evaluated in two German sub-regions (Cologne-Bonn region and Rhine-Valley south of Mainz), by combining ground truth sampling on Google Earth images and regional crop type databases. The overall accuracy assessed in the evaluation regions reaches 90% when plasticulture is distinguished between PMF, tunnels and greenhouses, while it exceeds 95% when the total area of plasticulture is mapped. Based on the feature rank, the PDF resulted to be the most important feature in the classification process. Moreover, the PDF showed higher values for crops typically associated with use of plastic films, which points at a strong relationship between the PDF and the presence of plastic covers. This study demonstrates the potential of an operational workflow for large scale plasticulture mapping and monitoring by synergising freely available optical and SAR satellite data.

How to cite: Fabrizi, A., Fiener, P., Jagdhuber, T., Van Oost, K., and Wilken, F.: Large scale detection of plastic covered crops using multispectral and SAR satellite data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8476, https://doi.org/10.5194/egusphere-egu23-8476, 2023.

X3.147
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EGU23-14969
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ECS
Microplastics are released from agricultural soils to the atmosphere by wind erosion
(withdrawn)
Mahrooz Rezaei, Sajjad Abbasi, Haniye Pourmahmood, Patryk Oleszczuk, Andrew Turner, and Coen Ritsema
X3.148
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EGU23-16140
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ECS
Juliana Laszakovits, Ralf Kägi, Flora Willie, Michael Sander, and Kristopher McNeill

Biodegradable polymers can play an important role in helping to overcome the plastic pollution problem by replacing conventional, persistent polymers in specific applications. These include applications in which plastics are used directly in the environment and cannot be completely recollected (e.g., mulch films and seed coatings) and for bags used to collect biowaste for industrial composting. Temperature is an important system factor that determines the rate at which biodegradable polymers biodegrade in both natural and engineered environments. Yet, there is a limited quantitative understanding of how temperature impacts polymer biodegradation rates in the open environment, specifically in soils. Temperature not only affects the activity of soil microorganisms but also their extracellular enzymes that hydrolyze backbone bonds in biodegradable polymers. Here, we assessed the impact of temperature on the biodegradation of poly-3-hydroxybutyratehydroxyhexanoate (PHBH) in agricultural soils. We incubated PHBH in three different standards soils and at four temperatures (5, 15, 25 and 35 ºC). We determined the amount of residual PHBH in soil over time by extracting PHBH from the soil using a chloroform-methanol mixture and then quantifying the extracted polymer using proton nuclear magnetic resonance spectroscopy (1H NMR). We find that the rate of PHBH biodegradation increased with increasing temperatures in all three soils, but that the rates and temperature dependence of the rates variedbetween soils. The fastest biodegradation occurred in LUFA 6S (clay) followed by LUFA 2.4 (loam), and the slowest biodegradation was in LUFA 2.2 (sandy loam). The soil-dependence likely reflects differences in the abundance and activity of microbial degraders in these soils. At lower incubation temperatures, there was a noticeable lag-phase prior to the onset of biodegradation, which was most pronounced in soil LUFA 2.2 . When the lag-phase is included in the kinetic modeling, the temperature-dependence of the PHBH biodegradation rate can be described reasonably well by the Arrhenius rate law but differs between soils. We further investigated the microbial colonization dynamics of PHBH film surfaces during the lag-phase using optical and scanning electron microscopy. After incubation of solvent-cast PHBH films in the soil at the aforementioned temperatures, microscopic analyses revealed that fungal hyphae were involved in both colonization and initial breakdown of the PHBH films, and that fungal activity increased with increasing temperature. Taken together, these results suggest that a careful determination of the temperature dependence of polymer biodegradation in different soils is needed to predict, from standard tests run at elevated and constant temperature, how quickly biodegradable polymers will biodegrade in the open environment where temperatures are lower and variable.

How to cite: Laszakovits, J., Kägi, R., Willie, F., Sander, M., and McNeill, K.: Temperature impacts polymer biodegradation rates in soils in predictable ways but with dependencies that differ between soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16140, https://doi.org/10.5194/egusphere-egu23-16140, 2023.

X3.149
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EGU23-17599
Fungal plastiphily and its link to generic virulence traits makes environmental microplastics a global health factor
(withdrawn)
Gerasimos Gkoutselis, Stephan Rohrbach, Janno Harjes, Andreas Brachmann, Marcus A. Horn, and Gerhard Rambold

Posters virtual: Fri, 28 Apr, 16:15–18:00 | vHall SSS

vSSS.5
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EGU23-15134
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ECS
Growth reduction of- and interactions with nanoplastic particles in a soil bacterium and a soil fungus
(withdrawn)
Paola Micaela Mafla Endara, Pelle Ohlsson, Jason Beech, and Edith C. Hamemr