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Biodegradable mulch film potentially offers an encouraging alternative to conventional (petroleum-based) plastic films. Since biodegradable films are more susceptible to rapid degradation, more microplastics (MPs) are likely to be generated than conventional films within the same time frame, probably leading to more severe MPs pollution and associated effects. However, the effect of biodegradable mulch film residues and associated MPs pollution on plant-soil health remains uncertainty. Here, we evaluated the potential effect of bio-MPs pollution on soil carbon (C) and nutrient (i.e., N and P) cycling, soil biology (microorganisms and mesofauna), and plant health, as these are crucial to agroecosystem functioning and the delivery of key ecosystem services. Unlike the inert (and therefore recalcitrant) C contained within petroleum-based MPs, at least 80% of the C from bio-MPs is converted to CO2, with up to 20% immobilized in living microbial biomass (i.e., < 0.05 t C ha−1). Although biodegradable films are unlikely to be important in promoting soil C storage, they may accelerate microbial biomass turnover in the short term, as well as CO2 production. Compared to conventional MPs, bio-MPs degradation is more pronounced, thereby inducing greater alterations in microbial diversity and community composition. This may further alter N2O and CH4 emissions, and ultimately resulting in unpredictable consequences for global climate warming. The extent to which this may occur, however, has yet to be shown in either laboratory or field studies. In addition, bio-MPs have a large chance of forming nanoplastics, potentially causing a stronger toxic effect on plants relative to conventional MPs. Consequently, this would influence plant health, crop productivity, and food safety, leading to potential health risks. It is unclear, however, if these are direct effects on key plant processes (e.g. signaling, cell expansion) or indirect effects (e.g. nutrient deficiency or acidification).

Many anthropogenic pressures are being exerted on terrestrial ecosystems globally, perhaps the most pressing of which include microplastics (MPs; <5 mm in size) pollution and climate change, both of which may have unpredictable consequences on soil ecosystem functioning. We therefore hypothesized that a dual pressure (MPs and warming) on plant-soil functioning would be more severe than either stress alone. Thus, we studied the interactive effects of MPs and warming on soil quality and ecosystem multifunctionality. Maize (Zea mays L.) was grown for 6 weeks under ambient and warming (+5 °C) conditions in the absence (control) or presence (5 % loading) of either polyethylene (PE), polyvinylchloride (PVC), or biodegradable polyhydroxyalkanoate (PHA). We found that PHA stimulated microbial biomass and enzyme activity due to the additional C resources, thus changing soil quality and ecosystem multifunctionality under ambient temperature. However, the accelerated microbial growth in PHA-treated soils also promoted N immobilization and plant–microbe nutrient competition, consequently decreasing plant health index by 65 % relative to the Control. As PVC and PE are chemically more stable than PHA, they had limited effect on soil quality and plant health under ambient temperature in the short term (6 weeks). Most of the negative impacts of MPs only occurred under ambient temperature, with few effects evident under warming conditions. This suggested that the effect of heat stress (evidenced by stunted growth and chlorophyll content) was noticeably more acute than the effect of MPs. In conclusion, we showed that MPs do affect plant health, soil quality, and ecosystem multifunctionality but these effects on plant-soil health were not exacerbated by the effects of a warmer climate.

This contribution reports experimental measurements of the oxidation of H2S and CH3SH, under atmospheric pressure in a jet-stirred reactor (JSR), in the temperature range of 600–1100 K and for stoichiometric and oxidizing conditions. We update a recent kinetic model, originally developed based on the measurements of oxidation of H2S and CH3SH in a tubular flow-reactor and apply it to simulate the experimental data. The CH3SH subset of the kinetic model features new reactions based on a recent theoretical work and the rate parameters proposed in the present investigation. The oxidation of CH3SH proceeds mainly through an intersystem crossing process that leads to the formation of sulfine (CH2SO). The unimolecular decomposition of CH2SO in two competing reactions produces CO + H2S and COS + H2. The results from the model concur well with the experimental measurements, both from the present work and from the literature. We demonstrate that, both H2S and CH3S exhibit a similar ignition temperature, due to the initiation step that involves the abstraction of H initially bonded to sulfur. It is expected that, the results from the present investigation find application in processing of sour gas, including shale gas, especially in the direct combustion of the gas (i.e., without purification) for energy production.

This contribution combines results of experiments with kinetic modelling to probe the unusual behaviour of carbonyl sulfide (COS), a sulfur species that frequently arises in fuel systems. The experiments identified CO and SO2 as the primary oxidation products, with no formation of CO2. The low ignition temperature (<600 K) of COS observed in prior experiments conflicts with the high activation barrier for the reaction COS + O2 → CO2 + SO of 211.3 kJ mol−1 on the traditional triplet reaction surface. We proposed that, this kinetic barrier prompts the reaction to transfer onto the singlet surface through intersystem crossing that allows the process to surmount lower-energy hurdles. By considering the oxidation of COS as a single step reaction, we fitted the Arrhenius parameter for the reaction COS + O2 → CO + SO2 directly from our experimental measurements. The fitted activation energy of 70.1 kJ∙mol−1 agrees with that of 85.4 ± 20.0 kJ∙mol−1 as calculated in literature at the Hartree-Fock level of theory, indicating the appearance of the intersystem crossing process in the oxidation of COS. The reaction mechanism based on this comportment leads to excellent agreement between the kinetic model and the experimentally measured quantities, such as the onset temperature and the conversion profiles of detected species. The proposed kinetic model for the oxidation of COS provides a tool to design both the SOx mitigation processes and industrial systems for safe handling of sulfur impurities in fossil fuels.

© 2020 Elsevier B.V. The production of magnesium alloy WE43 was achieved by selective laser melting (SLM). The alloy was investigated after SLM, hot isostatic pressing (HIP), and solutionising heat treatment. The microstructure and corrosion behaviour of the specimens were carefully characterised, whilst assessed and contrast relative to the conventionally cast alloy counterpart. The SLM prepared specimens possess a unique microstructure comprising fine grains growing with a strong [0001] texture along the building direction with a low fraction of process-induced and metallurgical defects, reaching < 0.1 %, after optimising the SLM parameters and the HIP treatment. Electrochemical measurements demonstrated that the SLM prepared WE43 is cathodically more active as compared with its cast counterpart. It is proposed that this behaviour is due to a high density of zirconium-rich oxide particles uniformly distributed throughout the alloy microstructure as well as the alterations in the chemical composition of the solid-solution matrix originating from the high cooling rates of SLM. It was also noted that the oxide particles are mainly sourced by powder. The present results suggest that the corrosion of SLM prepared Mg alloys could be greatly improved once the influence of powder characteristics is further understood and controlled.