Extraction and quantification of nano- and microplastics from sediments and soils is challenging. Although no standard method has been established so far, flotation is commonly used to separate plastic from mineral material. The objective of this study was to test the efficiency of flotation for the extraction of nano- and microplastics from biosolids and soil. We spiked biosolids and soil samples with polystyrene nano- and microbeads (0.05, 1.0, 2.6, 4.8, and 100 μm diameter). Different extraction methods (w/ and w/o H2O2 digestion) were tested, and plastic beads were separated from mineral particles by flotation in a ZnCl2 solution. Plastic particles were quantified by UV-Vis spectrometry and gravimetrically. While large beads (100 μm) could be quantitatively extracted (∼100%) from both biosolids and soils, smaller beads had low extraction efficiencies (ranging from 5 to 80%, with an average of 20%). Except for the 100 μm beads, oxidation with H2O2 negatively impacted the extraction efficiencies. For the soil, extraction with water only, followed by flotation in a ZnCl2 solution, resulted in relatively high extraction efficiencies (>75%) for beads larger than 1 μm, but low efficiencies (<30%) for the 0.05 and 1.0 μm beads. Our results indicate that while flotation generally works to separate plastic nano- and microbeads in a solution, the challenge is to quantitatively extract nano- and microbeads from a biosolids or soil matrix. Samples high in organic matter content require removal of the organic matter, but the common method of H2O2 oxidation leads to poor extraction efficiencies for nano- and microbeads.

Association of plastic particles with plant roots could represent a pathway for human consumption of plastic and plastic-associated organic contaminants.

Hematopoietic stem cell (HSC) transplantation has the potential to treat a variety of human diseases, including genetic deficiencies, immune disorders, and to restore immunity following cancer treatment. However, there are several obstacles that prevent effective HSC transplantation in humans. These include finding a matched donor, having a sufficient number of cells for the transplant, and the potency of the cells in the transplant. Ethical issues prevent effective research in humans that could provide insight into ways to overcome these obstacles. Highly immunodeficient mice can be transplanted with human HSCs and this process is accompanied by HSC homing to the murine bone marrow. This is followed by stem cell expansion, multilineage hematopoiesis, long-term engraftment, and functional human antibody and cellular immune responses. As such, humanized mice serve as a model for human HSC transplantation. A variety of conditions have been analyzed for their impact on HSC transplantation to produce humanized mice, including the type and source of cells used in the transplant, the number of cells transplanted, the expansion of cells with various protocols, and the route of introduction of cells into the mouse. In this review, we summarize what has been learned about HSC transplantation using humanized mice as a recipient model and we comment on how these models may be useful to future preclinical research to determine more effective ways to expand HSCs and to determine their repopulating potential in vivo.

Environmental contextNanominerals are more reactive than bulk minerals, a property that strongly influences the fate of nutrients and contaminants in soils and plants. This review discusses applications of Fe- and Mn-nano-oxides in agricultural systems and their potential to be used as fertiliser and contaminant adsorbents, while addressing potential phytotoxicity. We discuss areas where significant advances are needed, and provide a framework for future work. AbstractRising population growth and increase global food demand have made meeting the demands of food production and security a major challenge worldwide. Nanotechnology is starting to become a viable remediation strategy of interest in farming. Ultimately, it may be used as a sustainability tool in agricultural systems. In these roles, it could be used to increase the efficiency of techniques such as food monitoring, pathogen control, water treatment and targeted delivery of agrochemicals. In addition to these uses, nanoparticles, particularly nano-metal-oxides (NMOs), have been engineered to act as contaminant scavengers and could be applied to a wide range of systems. Numerous studies have investigated the scavenging ability of NMOs, but few have investigated them in this role in the context of agricultural and food systems. Within these systems, however, research has demonstrated the potential of NMOs to increase crop health and yield but few have studied using NMOs as sources of key micronutrients, such as Fe and Mn. In this review, we address previous research that has used Fe- and Mn-NMOs in agricultural systems, particularly the worldwide crop production of the four major staple foods – rice, wheat, maize and soybeans – highlighting their application as fertilisers and sorbents. Fe- and Mn-NMOs are strong candidates for immobilisation of agricultural contaminants in soils and, because they are naturally ubiquitous, they have the potential to be a cost-effective and sustainable technology compared with other remediation strategies.

Biosolids can be a source of metals and metal nanoparticles. The objective of this study was to quantify and characterize the accumulation and transport of silver (Ag) in a natural soil that has received agronomically recommended rates of biosolids as fertilizer from 1994 to 2017. Total Ag concentrations were measured in biosolids and soil samples collected from 0 to 10 cm between 1996 and 2017. The depth distribution of Ag in soil to 60-cm depth was measured in 2017. Electron microscopy, in combination with X-ray spectroscopy, and X-ray absorption spectroscopy were used to characterize the Ag. The Ag concentrations in the biosolids-amended soil increased steadily from 1996 until 2007, after which the concentrations leveled off at about 1.25 mg Ag kg −1 soil. This corresponded with a decrease of Ag concentrations in biosolids over time. The majority of the Ag (82%) was confined to the top 10 cm of the soil, small amounts (14%) were detected at 10-to-20-cm depth, and trace amounts (4%) were detected at 30-to-40-cm depth. The Ag in the biosolids was identified as S-containing nanoparticles (Ag 2 S) with a diameter of 10-12 nm; however, in soil, the Ag concentrations were too low to allow identification of Ag speciation. This study shows that in a real-world field scenario, biosolids applied at agronomic rates represent a long-term, economically viable source of crop nutrients without increasing the concentration of total Ag in soil above a maximum of 1.5 mg Ag kg −1. This concentration is below estimated ecotoxicity limits for Ag 2 S in soil.

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