Spatial Distribution of Meso- and Microplastics in Floodplain Soilscapes: Novel Insights from Rural to Urban Floodplains in Central Germany

Plastics and especially microplastics have become an emerging threat to global ecosystems. Despite the manifold benefits and applications of the human-made material plastic, the uncontrolled release of plastics into the environment has led to a “global plastic crisis”. During the last decades it becomes apparent that this crisis leads to the presence of plastics within different environments including marine, aquatic and terrestrial systems under worldwide evidence. Furthermore, environmental plastic research was able to reveal that although plastic often ends up in oceans, the majority of plastics in the environment are transported as part of a “global plastic cycle” from the land to sea via river systems. Those river systems are not isolated in the landscape, but rather a part of an “aquatic-terrestrial interface” which also encompasses floodplains and their soilscapes. The present thesis focuses on the spatial distribution and spatio-temporal accumulation of meso- and microplastics in floodplain soilscapes following the overall objective to unravel the role of floodplain soilscapes as depositional areas of plastics within the global plastic cycle. In this context, a number of individual contributions have been published, reaching from conceptual spatial research approaches, over case studies conducted within two different floodplain soilscapes, to further opinions on the scientific benefit of plastic residues in floodplain soils. The individual contributions are linked by the major hypothesis that floodplain soilscapes act as temporal accumulation sites for plastics, driven by flood-related processes and land use over the last 70 years. To proof this major hypothesis and to overcome the lack of spatial reference in microplastics research, a geospatial sampling approach was conducted. Initial spatial data on meso- and microplastics in floodplain soils were obtained by a holistic analysis approach including the analysis of basic soil feature and metal analysis, the quantification of meso- and microplastics as well as sediment dating. Within both studied river floodplains geospatial sampling enables a detection of meso- and microplastics over the entire floodplain area and within the entire soil column reaching depths of two meters. Additionally, a frequent accumulation of plastics was found within the upper 50 cm of floodplain soils. In combination with dating of near-channel floodplain sites, it could be demonstrated that those plastic accumulations are related to recent sedimentary deposits since the 1960s. However, evidence of plastic from deeper soil layers suggests that vertical displacements in floodplain soils occur and that plastics become mobilized. Furthermore, the presence of plastics in upstream areas suggests that plastics are released to river systems and deposited via flood dynamics already in rural areas. Additionally it appears that anthropogenic impacts, such as tillage or floodplain restoration influence plastic distributions. The findings of this thesis clarify that floodplain soilscapes are part of the global plastic cycle as temporally depositional areas of plastics, but raising further questions on the mobility of plastics in soils and about the exact contribution of different environmental drivers towards plastic deposition. Finally, the present thesis indicates that the spatial reference of environmental plastic research should be rethought, in order to understand the spatial dynamics of plastics within the aquatic-terrestrial interface

Plastics in soil description and surveys – practical considerations and field guide

A growing evidence base has shown that plastics are widely distributed in soils and could have negative effects on soil functions. However, within international standards for soil description, plastics are handled so far as one part of humanmade artefacts. With the ongoing plastic crisis, such a simple classification may no longer be sufficient to provide a satisfactory description of plastics in soils. Based on the latest research on plastics in soils, these foreign components can no longer be understood as relevant only for soils in urban, industrial, traffic, mining and military areas. This perspective therefore aims to suggest a possible approach towards a future and more comprehensive description of plastics in soil characterization. Based on the existing definitions within the international soil description standards, a description concept and a corresponding field guide are proposed. The proposed approach comprises a recent definition of plastics and guidelines for the description of visible plastic residues in soils during field work. Classification approaches are developed for plastics abundance and distribution as well as plastic characteristics. Furthermore, pitfalls during the description, as well as during the extraction of plastics from soils in the field, and further limitations are discussed. Basic soil description during soil surveys or soil mapping, are a strong tool of soil science to derive environmental data sets. The perspective and the field guide presented in this paper are intended to change this circumstance and enable soil scientists to describe plastic residues in soils simple, comparable and adapted to existing standards in future

Opening Space for Plastics — Why Spatial, Soil and Land Use Data Are Important to Understand Global Soil (Micro)Plastic Pollution

After five years of research on microplastic pollution of soils it becomes obvious that soil systems act as a reservoir for microplastics on global scales. Nevertheless, the exact role of soils within global microplastic cycles, plastic fluxes within soils and environmental consequences are so far only partly understood. Against the background of a global environmental plastic pollution, the spatial reference, spatial levels, sampling approaches and documentation practices of soil context data becomes important. Within this review, we therefore evaluate the availability of spatial MP soil data on a global scale through the application of a questionnaire applied to 35 case studies on microplastics in soils published since 2016. We found that the global database on microplastics in soils is mainly limited to agricultural used topsoils in Central Europe and China. Data on major global areas and soil regions are missing, leading to a limited understanding of soils plastic pollution. Furthermore, we found that open data handling, geospatial data and documentation of basic soil information are underrepresented, which hinders further understanding of global plastic fluxes in soils. Out of this context, we give recommendations for spatial reference and soil context data collection, access and combination with soil microplastic data, to work towards a global and free soil microplastic data hub

Investigating microplastic dynamics in soils: Orientation for sampling strategies and sample pre‐procession

Studies on microplastics in soils is currently being established as a new research field. So far, mainly 'explorative studies' have been carried out to detect microplastics in different soil environments. To generate a deeper understanding of microplastics dynamics, 'systematic studies' are required. Such research must built on a targeted sampling strategy and considerate fieldwork and sample handling. From literature enquiry, a five-stage methodological workflow was deduced for studies on microplastics in soils. In the present review, the spatial representation of soils/soilscapes with microplasticsin soils research is conceptually and practically assessed. We discuss judgmental, randomized, and metric soil sampling strategies. Then, we explain sample pre-processing and give a brief overview of methods for microplastics identification and quantification. We conclude that the establishment of the novel field of research 'microplasticdynamics in soils' requires more intensive consideration of soil sampling strategies. Assoil is a complex medium and the soilscape is spatially heterogeneous, we highlight systematic sampling strategies as the best possible options for sophisticated research. However, no overall optimum methodology can be defined because the specific strategy must be in line with the particular research question. For all studies on microplastics in soils, practical improvement is needed to prevent contamination of soilsamples with plastics during sampling and sample pre-processing

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Autogenous Eutrophication, Anthropogenic Eutrophication, and Climate Change: Insights from the Antrift Reservoir (Hesse, Germany)

Climate change is projected to aggravate water quality impairment and to endanger drinking water supply. The effects of global warming on water quality must be understood better to develop targeted mitigation strategies. We conducted water and sediment analyses in the eutrophicated Antrift catchment (Hesse, Germany) in the uncommonly warm years 2018/2019 to take an empirical look into the future under climate change conditions. In our study, algae blooms persisted long into autumn 2018 (November), and started early in spring 2019 (April). We found excessive phosphorus (P) concentrations throughout the year. At high flow in winter, P desorption from sediments fostered high P concentrations in the surface waters. We lead this back to the natural catchment-specific geochemical constraints of sediment P reactions (dilution- and pH-driven). Under natural conditions, the temporal dynamics of these constraints most likely led to high P concentrations, but probably did not cause algae blooms. Since the construction of a dammed reservoir, frequent algae blooms with sporadic fish kills have been occurring. Thus, management should focus less on reducing catchment P concentrations, but on counteracting summerly dissolved oxygen (DO) depletion in the reservoir. Particular attention should be paid to the monitoring and control of sediment P concentrations, especially under climate change

Phosphorus enrichment in floodplain subsoils as a potential source of freshwater eutrophication

Despite decades of management efforts, freshwater eutrophication has not been effectively mitigated in each affected ecosystem. This might be due to insufficient knowledge of the sources of phosphorus (P) inputs into surface waters. We sampled 2 m-deep soil profiles in four floodplain areas under differently managed grassland in Germany under dry and moist conditions regarding soil moisture and precipitation. Four soil P fractions of decreasing solubility were determined. We found systematic enrichment of easily soluble P forms in the floodplain subsoils (average: from 87.5 cm depth). Water-soluble P in these “deep P stocks” was positively correlated with total phosphorus concentrations in the adjacent surface waters. Our data cautiously suggest increased P mobilization from deep P stocks under moist conditions. Drier conditions coincided with increased P retention, resulting in relatively large amounts of easily soluble P which could readily be desorbed and lost at the next stronger precipitation event. We found no effects of grassland management on deep P stock features and dynamics. Deep P stocks might be considered a new source of diffuse P losses from soils. To effectively mitigate freshwater eutrophication, best management practices need to be developed to minimize P transfer from deep P stocks

Plastics as a stratigraphic marker in fluvial deposits

Plastics as purely human-made materials have entered the environment for at least 70 years. They are detectable in a wide variety of ecosystems worldwide. Due to the global occurrence of plastics, the long-lasting presence, the clear temporal delineation and the lack of a geogenic background, plastics have also been considered as a potential marker for the proposed Anthropocene. Fluvial depositional systems are transport pathways for anthropogenic plastic residues through the environment, and they provide opportunities for the storage and accumulation of plastics. Despite the potential negative effects that originate from pollution to the environment and its biota, the presence of plastic in fluvial environments is also potentially useful for a scientific advantage. The viewpoint presented in this paper raises the question of whether plastic particles are also usable as a new stratigraphic marker within fluvial systems of the “Anthropocene”, and thus for dating the youngest sedimentary deposits. We elaborate on the theory of conditions for using plastic as a stratigraphic marker, as well as its use as a general marker (from 1950) and as a specific marker based on polymer types and the associated age on earliest possible occurrence (1910–1990). Benefits and limitations in practical and interdisciplinary application include an inexpensive and rapid approach with combinable existing methods, that may be limited by disturbance of the investigated legacy sediments or in-situ relocation of plastic

Comparative risk assessment of phosphorus loss from “deep phosphorus stocks” in floodplain subsoils to surface waters

Phosphorus (P) loss from soil may trigger freshwater eutrophication and endanger supply with drinking water regionally. The present paper aims at encouraging discussion and development of sophisticated strategies for risk assessment of P loss from soils of riparian buffer zones (RBZ) as a prerequisite for targeted and effective mitigation of such P losses and their effects on freshwater eutrophication. We use data from a case study on RBZ soils in Germany to compare the performance of different environmental indicators of a risk for P loss from soil. Our data suggest that RBZ soils are temporarily sinks or sources for P. The spatial hotspots of P loss are the topsoils and the deep P stocks (labile P enriched in RBZ subsoils below on average 87.5 cm depth). We discuss four aspects to be considered conceptually and methodologically in the assessment of a risk for P loss from RBZ soils: (1) spatial heterogeneity and spatial bias; (2) temporal heterogeneity and temporal bias; (3) conceptual bias caused by different dynamics of individual P fractions; and (4) adequacy of threshold values. To minimize bias, we propose to assess risk for P loss from RBZ soils using a geospatial, temporally resolved sampling strategy, site-specific or regional threshold values, and a P fractionation approach. For this purpose, we introduce PdHCl as a risk indicator, which is not susceptible to very short-term dynamics (in contrast to water-soluble P)

The enrichment of phosphorus in floodplain subsoils – A case study from the Antrift catchment (Hesse, Germany)

Deep phosphorus (P) stocks are considered a potential driver of freshwater eutrophication because they may temporarily transfer P to the groundwater and adjacent surface waters. The build-up of deep P stocks is not yet understood. Hence, their contribution to water quality impairment cannot be mitigated effectively. We conducted a field study with soil sampling and P fractionation in the laboratory to assess five scenarios how deep P stocks might develop. Our data show that deep P stocks result neither from primary bedrock/substratum features (geogenic loading) nor from primary pedological characteristics. Instead, they seem to originate from secondary processes, i.e., underground P translocation. The build-up of deep P stocks is indicated to be specifically driven by downslope translocation of P in the interflow, which leads to P enrichment of toeslope subsoils. Moreover, under low flow conditions, floodplain subsoils might become enriched with P by increased sorption of P from groundwater which is hydrologically connected with surface waters with high P concentrations. Gleysol groundwater dynamics did not prove to be a systematic driver of the build-up of deep P stocks. However, on certain sites, intensive groundwater dynamics might foster vertical P translocation and could hence contribute to deep P enrichment. Thus, enrichment of phosphorus in floodplain subsoils probably results interactively from several subsurface P translocation processes which might be weighted site-specifically