A bibliometric analysis of global research hotspots and progress on microplastics in soil‒plant systems.

Plastic pollution has become a global and persistent challenge, posing threats to ecosystems and organisms. In recent years, there has been a rapid increase in scientific research focused on understanding microplastics in the soil‒plant system. This surge is primarily driven by the direct impact of microplastics on agricultural productivity and their association with human activities. In this study, we conducted a comprehensive bibliometric analysis to provide an overview of the current research on microplastics in soil‒plant systems. We systematically analysed 192 articles and observed a significant rise in research interests since 2017. Notably, China has emerged as a leading contributor in terms of published papers, closely followed by Germany and the Netherlands. Through co-authorship network analysis, we identified 634 different institutions that participated in publishing papers in this field, with the Chinese Academy of Sciences having the most collaborations. In the co-occurrence keyword network, we identified four clusters focusing on the diversity of microplastics within the agroecosystem, transportation, and quantification of microplastics in soil, analysis of plastic contamination type and impact, and investigation of microplastic phytotoxicity. Furthermore, we identified ten research priorities, categorized into the effects of microplastics in "soil" and "plant". The research hotspots were found to be the effect of microplastics on soil physicochemical properties and the synergistic phytotoxicity of microplastics with other pollutants. Overall, this bibliometric analysis holds significant value, serving as an important reference point and offering valuable suggestions for future researchers in this rapidly advancing field.

Bacterial cellulose/lignin nanoparticles composite films with retarded biodegradability.

In practical applications, the full biodegradability of all-biomass-based bacterial cellulose (BC) composites enhances their environmentally friendliness but results in the poor durability especially at humid conditions. This work prepared BC/lignin nanoparticles (LNPs) composite films with retarded biodegradability, which could broaden their application area. Three LNPs were fabricated using technical lignins extracted by deep eutectic solvent (DES), ethanol organosolv, soda/anthraquinone from poplar. LNPs involvement during BC fermentation showed limited influence on its productivity but significantly retarded the biodegradation of composite films. The potential inhibition mechanism was physical barrier and non-productive binding of LNPs. The BC/Soda LNPs showed much higher retarded degradation property (~58 wt% degradation) compared to BC/Organosolv LNPs and BC/DES LNPs (~85 wt% and ~ 97 wt% degradation respectively) at high enzyme loadings of 5 mg g-1 BCE. While at low enzyme loadings of 1 mg g-1 BCE, all these three composite films showed comparable retarded degradation property of ~60 wt%.

Fabrication of spherical lignin nanoparticles using acid-catalyzed condensed lignins.

Valorization of lignin by-products enhances the overall economics of current lignocellulose biorefinery. This work showed the high potential of fabricating acid-catalyzed condensed lignin fragments into high-value lignin nanoparticles (LNPs) with spherical structure. Four condensed lignins, i.e., liquid hot water pretreated hardwood aspen and eucalyptus lignin, steam pretreated softwood lodgepole pine and herbaceous corn stover lignin, were assessed for their abilities for LNPs using facile self-assembly method. Results showed the contents of condensed aromatics (0.20-0.67 mmol g-1) were varied with biomass species and hydrothermal pretreatment methods selected. Those resulting LNPs exhibited yields from 17.5 to 29.4%, particle sizes ranging from 20 to 100 nm and considerable suspension stabilities at pH 4-10. It was proposed that higher content of condensed lignin aromatics could provide more anchors available for their self-assembly through enhanced hydrophobic interactions, thus LNPs with more uniform particle size could be obtained. This work showed the technical opportunity to enhance the value of intractable condensed lignin through LNPs production towards a multi-product lignocellulose biorefinery.

Acidic deep eutectic solvents pretreatment for selective lignocellulosic biomass fractionation with enhanced cellulose reactivity.

This work tailored a promising two-step pretreatment, i.e., liquid hot water extraction followed by mild acidic deep eutectic solvents pretreatment for clean lignocellulose fractionation while enhancing cellulose reactivity for its subsequent utilization. The abilities of three acidic deep eutectic solvents (formic acid-, acetic acid- and lactic acid-choline chloride) to selectively extract poplar wood lignin and enhance cellulose reactivity were comparatively assessed. Results showed that rather high lignin selectivity of 6.3-7.9 was obtained while the available area and porosity of the resulting cellulose were significantly increased. The resulting cellulose pulps exhibited comparable chemical reactivity to commercial bleached Kraft pulp when cellulose acetate was selected as testing cellulose derivative for demonstrating purpose, showing their great promise for high-value use. It was proposed that the unique ionic properties of these acidic deep eutectic solvents were responsible for their selective lignin removal and cellulose swelling/deconstruction to enhance cellulose chemical reactivity.

Enhancing the soil heavy metals removal efficiency by adding HPMA and PBTCA along with plant washing agents.

Plant washing agents-water-extracted from Coriaria nepalensis (CN), Clematis brevicaudata (CB), Pistacia weinmannifolia (PW) and Ricinus communis (RC)-are feasible and eco-friendly for soil heavy metal removal, but their single application has limited removal efficiency. To improve their metal removal efficiencies, two biodegradable assistant agents, hydrolytic polymaleic anhydride (HPMA) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA), were investigated in combination with plant washing agents through batch soil washing experiments. Results showed that the addition of HPMA or PBTCA with plant agents greatly enhanced the removal efficiencies of soil heavy metals (p<0.05). Under acidic conditions, the maximum improvements in soil heavy metal removal reached 18.69% and 18.00% for soil Cd and Zn by PW+HPMA, respectively, and 12.89% for soil Pb by CN+HPMA. Under neutral or alkaline conditions, the largest improvements in soil Cd, Pb and Zn were 24.18%, 54.38% and 25.47% by PW+PBTCA, respectively. When compared with EDTA, the loss rates of soil nitrogen, phosphorus and potassium significantly decreased (p<0.05) and the soil organic carbon significantly increased (p<0.05) after washing with the combinations. Hence, the addition of HPMA or PBTCA with the plant agents could improve the removal of soil heavy metals.

Effects of surfactants on low-molecular-weight organic acids to wash soil zinc.

Soil washing is an effective approach to the removal of heavy metals from contaminated soil. In this study, the effects of the surfactants sodium dodecyl sulfate, Triton X-100, and non-ionic polyacrylamide (NPAM) on oxalic acid, tartaric acid, and citric acid used to remove zinc from contaminated soils were investigated. The Zn removal efficiencies of all washing solutions showed a logarithmic increase with acid concentrations from 0.5 to 10.0 g/L, while they decreased as pH increased from 4 to 9. Increasing the reaction time enhanced the effects of surfactants on Zn removal efficiencies by the acids during washing and significantly (P < 0.05) improved the removal under some mixed cases. Oxalic acid suffered antagonistic effects from the three surfactants and seriously damaged soil nutrients during the removal of soil Zn. Notably, the three surfactants caused synergistic effects on tartaric and citric acid during washing, with NPAM leading to an increase in Zn removal by 5.0 g/L citric acid of 10.60 % (P < 0.05) within 2 h. NPAM also alleviated the loss of cation exchange capacity of washed soils and obviously improved soil nitrogen concentrations. Overall, combining citric acid with NPAM offers a promising approach to the removal of zinc from contaminated soil.