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.

Plastic pollution is increasingly perceived as an emerging threat to terrestrial environments, but the spatial and temporal dimension of plastic exposure in soils is poorly understood. Bioturbation displaces microplastics (>1 μm) in soils and likely also nanoplastics (<1 μm), but empirical evidence is lacking. We used a combination of methods that allowed us to not only quantify but to also understand the mechanisms of biologically driven transport of nanoplastics in microcosms with the deep-burrowing earthworm Lumbricus terrestris . We hypothesized that ingestion and subsurface excretion drives deep vertical transport of nanoplastics that subsequently accumulate in the drilosphere, i.e., burrow walls. Significant vertical transport of palladium-doped polystyrene nanoplastics (diameter 256 nm), traceable using elemental analysis, was observed and increased over 4 weeks. Nanoplastics were detected in depurated earthworms confirming their uptake without any detectable negative impact. Nanoplastics were indeed enriched in the drilosphere where cast material was visibly incorporated, and the reuse of initial burrows could be monitored via X-ray computed tomography. Moreover, the speed of nanoplastics transport to the deeper soil profile could not be explained with a local mixing model. Earthworms thus repeatedly ingested and excreted nanoplastics in the drilosphere calling for a more explicit inclusion of bioturbation in nanoplastic fate modeling under consideration of the dominant mechanism. Further investigation is required to quantify nanoplastic re-entrainment, such as during events of preferential flow in burrows.

The studies aimed at examining the influences of the particle size distribution and surface charge on the behaviour of sludge in dewatering. It was possible to show that defined size dispersions of sludge particles as well as surface charge are necessary to reach better dewatering results and that the found correlations were independent of the type of sludge and the sewage treatment plant (Friedrich et al., 1990 and 1991). Based on laser diffraction measurements to determine panicle size distribution it was found that it was necessary to set a specific proportion between fine and large sludge particles in order to produce the best possible dewatering results and to get the required shear resistant flocs. To characterize the surface charge of the sludge particles various measuring methods were used. Determining the zeta-potential is a suitable means to describe the kinetics of degradation process in the sludge.

A new technique for the fast and quantitative extraction of cell parameters from diffraction patterns was applied to cervical gynecologic material.

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&lt;p&gt;Microplastic pollution of the terrestrial environment and its potential impact on ecosystem services are gaining increasing public and scientific attention. Although the number of investigations on microplastic presence in soil under different management systems is growing, knowledge on the potential mobility of microplastics and their spatial distribution within soil is still lacking. In particular, microplastic fibres are often considered less mobile in soil due to their elongated shape and the resulting potential entanglement in pore structures or aggregated soil particles. While these processes may affect their water-driven transport, biologically-driven transport may still occur unimpeded because particles may be ingested by macrofauna such as earthworms. Micro- and nanoplastic transport by earthworms has been previously observed, however, the effect of particle shape on the transport dynamics is still elusive.&lt;/p&gt;&lt;p&gt;For understanding microplastic fibre transport in soil from a mechanistic perspective, we performed a series of process-studies with deep-burrowing earthworms, i.e. &lt;em&gt;Lumbricus terrestris&lt;/em&gt;, in microcosms. We utilized metal-doped fibrous polyethylene terephthalate (PET) microplastics (1.27&amp;#177;0.66 mm) for a facilitated detection through acid extraction and subsequent analysis via inductively-coupled plasma mass-spectrometry. Fibres were spiked into the top of the soil columns of the microcosms, which were sampled according to specific depth segments every 7 days for four weeks. As a result, we were able to quantify fibre transport in soil profiles with a temporal resolution. Earthworms were important drivers of vertical transport of microplastic fibres in the soil, with fibres visibly incorporated into burrow walls. Thus, despite their elongated shape and relative larger size, microplastic fibres are not necessarily immobilized by interactions with soil particles, but continuously affected by burrowing soil organisms. Understanding these transport dynamics and the potential spatial distribution of microplastics of different shapes and sizes in the field is crucial in order to support appropriate sampling schemes for monitoring and for obtaining accurate mass estimates of microplastic pollution of terrestrial ecosystems.&lt;/p&gt;

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