Plastic footprint deteriorates dryland carbon footprint across soil-plant-atmosphere continuum.

Plastic fragments are widely found in the soil profile of terrestrial ecosystems, forming plastic footprint and posing increasing threat to soil functionality and carbon (C) footprint. It is unclear how plastic footprint affects C cycling, and in particularly permanent C sequestration. Integrated field observations (including 13C labelling) were made using polyethylene and polylactic acid plastic fragments (low-, medium- and high-concentrations as intensifying footprint) landfilling in soil, to track C flow along soil-plant-atmosphere continuum (SPAC). The result indicated that increased plastic fragments substantially reduced photosynthetic C assimilation (p < 0.05), regardless of fragment degradability. Besides reducing C sink strength, relative intensity of C emission increased significantly, displaying elevated C source. Moreover, root C fixation declined significantly from 21.95 to 19.2 mg m-2, and simultaneously root length density, root weight density, specific root length and root diameter and surface area were clearly reduced. Similar trends were observed in the two types of plastic fragments (p > 0.05). Particularly, soil aggregate stability was significantly lowered as affected by plastic fragments, which accelerated the decomposition rate of newly sequestered C (p < 0.05). More importantly, net C rhizodeposition declined averagely from 39.77 to 29.41 mg m-2, which directly led to significant decline of permanent C sequestration in soil. Therefore, increasing plastic footprint considerably worsened C footprint regardless of polythene and biodegradable fragments. The findings unveiled the serious effects of plastic residues on permanent C sequestration across SPAC, implying that current C assessment methods clearly overlook plastic footprint and their global impact effects.

Microplastics affect soil bacterial community assembly more by their shapes rather than the concentrations.

Polyethylene film mulching is a key technology for soil water retention in dryland agriculture, but the aging of the films can generate a large number of microplastics with different shapes. There exists a widespread misunderstanding that the concentrations of microplastics might be the determinant affecting the diversity and assembly of soil bacterial communities, rather than their shapes. Here, we examined the variations of soil bacteria community composition and functioning under two-year field incubation by four shapes (ball, fiber, fragment and powder) of microplastics along the concentration gradients (0.01%, 0.1% and 1%). Data showed that specific surface area of microplastics was significantly positively correlated with the variations of bacterial community abundance and diversity (r=0.505, p<0.05). The fragment- and fiber-shape microplastics displayed more pronounced interfacial continuity with soil particles and induced greater soil bacterial α-diversity, relative to the powder- and ball-shape ones. Strikingly, microplastic concentrations were not significantly correlated with bacterial community indices (r=0.079, p>0.05). Based on the variations of the ßNTI, bacterial community assembly actually followed both stochastic and deterministic processes, and microplastic shapes significantly modified soil biogeochemical cycle and ecological functions. Therefore, the shapes of microplastics, rather than the concentration, significantly affected soil bacterial community assembly, in association with microplastic-soil-water interfaces.

Aging rate, environmental risk and production efficiency of the low-density polyethylene (LDPE) films with contrasting thickness in irrigated region.

Physical thickness of low-density polyethylene (LDPE) films might determine the release rate of phthalic acid esters (PAEs) & structural integrity and affect production efficiency. However, this critical issue is still unclear and little reported. Aging effects were evaluated in LDPE films with the thickness of 0.006, 0.008, 0.010 and 0.015 mm in a maize field of irrigation region. The Scanning electron microscope (SEM) results showed that the proportion of damaged area (Dam) to total area of LDPE films was massively lowered with increasing thickness after aging. The highest and lowest Dam was 32.2% and 3.5% in 0.006 and 0.015 mm films respectively. Also, the variations in peak intensity of asymmetric & symmetrical stretching vibrations (ASVI & SSVI) were detected using Fourier transform infrared spectrum (FTIR), indicating that the declines in peak intensity tended to be slower with thickness. Interestingly, the declines in physical integrity were tightly associated with increasing exhalation rate of PAEs. Average releasing rate of PAEs was 38.2%, 31.4%, 31.5% and 19.7% in LDPE films from 0.006 to 0.015 mm respectively. Critically, thicker film mulching can lead to greater soil water storage at plough layer (SWS-PL) and better thermal status, accordingly harvesting higher economic benefit. Therefore, LDPE film thickening may be a solution to reduce environmental risk but improve production efficiency in arid region.

Farmers' participation into the recovery of waste agricultural plastic film: An application of the Theory of Planned Behavior.

This study aims to address the lack of relevant researches in the field of waste recycling using the Theory of Planned Behavior (TPB). A village-scale social survey was conducted to investigate the degree of farmers' participation in a waste plastic film program, i.e. Old for New in northwest China. The program required farmers to recycle plastic film residues in exchange for new films. Survey results showed that 67.5% of farmers accepted the program, yet only 14.5% of them actually participated. Logistic regression analysis was used to analyze questionnaire data and identify the factors that significantly affected farmers' recycling behavior. Principal component and weight analysis further showed that farmers' participation was mainly influenced by their attitudes (p < 0.01), with a relative weight (RW) of 46.3%. Yet, subjective norms (p < 0.1) and perceived behavior control (p < 0.1) had less effect on the degree of participation, and their RWs were 4.2% and 4.1% only, respectively. Moreover, the RW of plastic film usage characteristics and household characteristics reached up to 13.2% and 6.4%, respectively. Interestingly, environmental awareness (ß = 0.083) and compulsory environmental education (ß = 0.130) as surface factors strongly affected the farmers' adoption and response, with the RW of 25.7%. As such, the extended TPB model was established to analyze the participation behavior of farmers for stronger explanatory power. This study highlighted a promising strategy based on TPB for waste plastic film recycling and similar environmental management practices.

Plant biomass mediates the decomposition of polythene film-sourced pollutants in soil through plastisphere bacteria island effect.

The polyethylene (PE) film mulching as a water conservation technology has been widely used in dryland agriculture, yet the long-term mulching has led to increasing accumulation of secondary pollutants in soils. The decomposition of PE film-sourced pollutants is directly associated with the enrichment of specific bacterial communities. We therefore hypothesized that plant biomass may act as an organic media to mediate the pollutant decomposition via reshaping bacterial communities. To validate this hypothesis, plant biomass (dried maize straw and living clover) was embedded at the underlying surface of PE film, to track the changes in the composition and function of bacterial communities in maize field across two years. The results indicated that both dry crop straw and alive clover massively promoted the α-diversity and abundance of dominant bacteria at plastisphere, relative to bulk soil. Bacterial communities tended to be clustered at plastisphere, forming the bacteria islands to enrich pollutant-degrading bacteria, such as Sphingobacterium, Arthrobacter and Paracoccus. As such, plastisphere bacteria islands substantially enhanced the degradation potential of chloroalkene and benzoate (p < 0.05). Simultaneously, bacterial network became stabilized and congregated at plastisphere, and markedly improved the abundance of plastisphere module hubs and connectors bacteria via stochastic process. Particularly, bacterial community composition and plastic film-sourced pollutants metabolism were evidently affected by soil pH, carbon and nitrogen sources that were mainly derived from the embedded biomass. To sum up, plant biomass embedding as a nature-based strategy (NbS) can positively mediate the decomposition of plastic-sourced pollutants through plastisphere bacteria island effects.

Priming effects of nZVI on carbon sequestration and iron uptake are positively mediated by AM fungus in semiarid agricultural soils.

We investigated the priming effect of nanoscale zero-valent iron (nZVI) on carbon sink and iron uptake, and the possible mediation by AMF (arbuscular mycorrhizal fungi, Funneliformis mosseae) in semiarid agricultural soils. Maize seed dressings comprised of three nZVI concentrations of 0, 1, 2 g·kg-1 and was tested with and without AMF inoculation under high and low soil moistures, respectively. The ICP-OES observations indicated that both low dose of nZVI (1 g·kg-1) and high dose of nZVI (2 g·kg-1) significantly increased the iron concentrations in roots (L: 54.5-109.8 %; H: 119.1-245.4 %) and shoots (L: 40.8-78.9 %; H: 81.1-99.4 %). Importantly, the absorption and translocation rate of iron were substantially improved by AMF inoculation under the low-dose nZVI. Yet, the excess nanoparticles as a stress were efficiently relieved by rhizosphere hyphae, and the iron concentration in leaves and stems can maintain as high as about 300 mg·kg-1 while the iron translocation efficiency was reduced. Moreover, next-generation sequencing confirmed that appropriate amount of nZVI clearly improved the rhizosphere colonization of Funneliformis mosseae (p < 0.001) and the development of soil fungal community. Soil observations further showed that the hyphae development and GRSP (glomalin-related soil protein) secretion were significantly promoted (p < 0.05), with the increased R0.25 (< 0.25 mm) by 35.97-41.16 %. As a return, AMF and host plant turned to input more organic matter into soils for microbial growth and Fe uptake, and such interactions became more pronounced under drought stress. In contrast, high dose of nZVI (2 g·kg-1) tended to agglomerate on the surface of hyphae and spores, causing severe deformation and inactivation of AMF symbionts. Therefore, the priming effects of nZVI on carbon sequestration and Fe uptake in agricultural soils were positively mediated by AMF via the feedback loop of the plant-soil-microbe system for enhanced adaptation to global climate change.

Thickness effects of polyethylene and biodegradable film residuals on soil properties and dryland maize productivity.

Plastic film residuals are increasingly remaining in cultivated lands. However, it is a critical issue how residual plastic type and thickness affect soil properties and crop yield. To address this issue, in situ landfill was conducted using thick polyethylene (PEt1), thin polyethylene (PEt2), thick biodegradable (BIOt1), thin biodegradable (BIOt2) residues, and CK (control) with no residues landfill in a semiarid maize field. The findings demonstrated that the impact of various treatments on soil characteristics and maize yield varied considerably. Soil water content decreased by 24.82% in PEt1 and 25.43% in PEt2, compared to BIOt1 and BIOt2, respectively. BIOt2 treatment increased soil bulk density by 1.31 g cm-3 and lowered soil porosity by 51.11%, respectively; it also elevated the silt/clay proportion by 49.42% relative to CK. In contrast, microaggregate composition in PEt2 was higher (43.02%). Moreover, BIOt2 lowered soil nitrate (NO3-) and ammonium (NH4+) content. Compared with other treatments, BIOt2 resulted in significantly higher soil total nitrogen (STN) and lower SOC/STN. Finally, BIOt2 exhibited the lowest water use efficiency (WUE) (20.57 kg ha-1 mm-1) and yield (6896 kg ha-1) among all the treatments. Therefore, BIO film residues exhibited detrimental impacts on soil quality and maize productivity compared to PE film ones. Considering film thickness, thin residual films more evidently influenced soil quality and maize productivity than thick film ones.

Thickness-dependent release of microplastics and phthalic acid esters from polythene and biodegradable residual films in agricultural soils and its related productivity effects.

It is crucial to elucidate the release rate of microplastics (MPs) and phthalic acid esters (PAEs) in agricultural soil and their effects on crop productivity regarding film types and thicknesses. To address this issue, two-year landfill test was performed using 0.016 mm-thick polyethylene (PEt1) & biodegradable (BIOt1), and 0.01 mm-thin polyethylene (PEt2) & biodegradable (BIOt2) residual films as materials with no landfill as CK. Scanning electron microscopy (SEM) and infrared analyses revealed that two-year landfill caused considerable changes in physical forms and spectral peaks in BIO film, which was more pronounced in thin BIO (36.90 % weight loss). Yet, less changes were presented in the above analyzes in polyethylene (PE) films, and thick films damaged relatively less. MPs number was 86,829.11 n/kg in BIOt1 and 134,912.27 n/kg in BIOt2, equivalent to 2.55 and 3.72 times higher than in PEt1 and PEt2, respectively. This was closely associated with PAEs release, as soil PAEs concentration was substantially lower in PEt1 (17.60 g/kg) and PEt2 (21.43 g/kg) than in BIOt1 and BIOt2 (37.12 g/kg and 49.20 g/kg), respectively. Furthermore, maize productivity parameters were negatively correlated with the amount of MPs and PAEs. BIOt2 and PEt1 had the lowest and highest grain yield, respectively. BIO exhibited greater environmental risk and adverse effects on soil and crop productivity than PE film due to physical degradation and release of PAEs. Thickness-wise comparison exhibited that thin film residues had more adverse effect relative to thick film ones.

Moss-dominated biocrust-based biodiversity enhances carbon sequestration via water interception and plant-soil-microbe interactions.

We investigated a nature-based solution (NbS) via incorporating biocrust into alfalfa-maize intercropping system to test carbon sequestration in seriously eroded agricultural soils. Field investigation showed that the NbS (moss-dominated biocrust + intercropping) massively lowered surface soil erosion by 94.5% and soil carbon (C) and nitrogen (N) loss by 94.7 and 96.8% respectively, while promoting rainwater interception by 82.2% relative to bare land (CK). There generally existed positive interactions between biocrust and cropping in the integrated standing biodiversity system. Enhanced plant biomass input into soils substantially promoted soil fungal community diversity and abundance under NbS (p < 0.05). This enabled NbS to evidently improve soil macroaggregate proportion and mean weight diameter. Critically, topsoil carbon storage was increased by 2.5 and 10.7%, compared with CK and pure intercropping (p < 0.05). Conclusively, the standing diversity under such NbS fostered soil C sequestration via water interception and plant-soil-microbe interactions in degraded agricultural soils.

In situ degradation of low-density polyethylene film in irrigation maize field: Thickness-dependent effect.

Thickness of low-density polyethylene (LDPE) film might determine its mechanical strength, clean production and soil health. Yet, this issue is little understood. In situ aging effects were evaluated in LDPE films with the thickness of 0.006 mm, 0.008 mm, 0.010 mm and 0.015 mm in maize field. The data showed that maximum tensile force (TFmax), maximum tensile strength (TSmax) and elongation at break (EAB) were massively lowered with increasing thickness after aging. The greatest and lowest reduction magnitude of EAB was 27.6 % and 11.2 % in 0.006 mm and 0.015 mm films respectively. Also, the melting point (Tm) and crystallinity (Xc) under Differential Scanning Calorimeter (DSC) tended to decline with the increasing thickness. Moreover, the peak intensity of crystalline regions tended to transfer and concentrate on the amorphous regions, and such tendency became more pronounced in the thin films. Interestingly, there existed a pronounced distinct thickness-dependent effects on soil bulk density (SBD) and soil water-stable aggregate proportion. Thick plastic film mulching increased SBD but reduced the proportion of macroaggregates (mainly referred to 0.015 mm and 0.010 mm). In addition, thick film mulching slightly reduced the levels of soil organic carbon (SOC) and total nitrogen (TN), but significantly promoted the contents of soil labile C and N. Particularly, it significantly promoted above- & under-ground biomass of maize across two growing seasons (p < 0.05). To sum up, thickening LDPE film may act as a promising solution to improve LDPE film residue recycling, while benefiting for higher productivity. However, thick film mulching may cause a certain adverse impact on soil structure, and further investigations would be needed in the future.

Rhizosphere effect of nanoscale zero-valent iron on mycorrhiza-dependent maize assimilation.

Rhizosphere effect of nanoscale zero-valent iron (nZVI) is crucial but little reported. Maize seeds were dressed with four nZVI concentrations (0, 1.0, 1.5, 2 g kg-1 ) and inoculated with arbuscular mycorrhizal fungus (AMF) (Funneliformis mosseae). The SEM images illuminated that excessive nZVI particles (2 g kg-1 ) were agglomerated on the surface of hyphae and spore, causing severe deformation and inactivation of AMF symbionts and thereafter inhibiting water uptake in maize seedlings. This restrained the scavenging effects of enzymatic (superoxide dismutase, peroxidase) and non-enzymatic compounds (proline & malondialdehyde) on ROS, and leaf photoreduction activity and gas exchange ability (p < 0.05). Interestingly, the inoculation with AMF effectively alleviated above negative effects. In contrast, appropriate dose of nZVI, that is, ≤1.5 g kg-1 , can be evenly distributed on the hyphae surface and form the ordered symbionts with AMF. This help massively to enhance hyphae growth and water and nutrient uptake. The enhanced mycorrhizal infection turned to promote rhizosphere symbiont activity and leaf Rubisco and Rubisco activase activity. Light compensation point was massively lowered, which increased photosynthetic carbon supply for AMF symbionts. Particularly, such priming effects were evidently enhanced by drought stress. Our findings provided a novel insight into functional role of nZVI in agriculture and AMF-led green production.

Transition in plant-plant facilitation in response to soil water and phosphorus availability in a legume-cereal intercropping system.

BACKGROUND: The tradeoff between negative and positive interactions of facilitated species and facilitators may depend on the degree of resource availability in agroecosystems. However, the rhizospheric mechanisms driving trade-offs that occur along phosphorus (P) and water availability gradients have not yet been systematically clarified. We established three types of root isolation conditions (no barrier, nylon barrier and solid barrier) at different P and water addition levels to address the above issue in a maize-grass pea intercropping system. RESULTS: The total yield and biomass net effect (NE) and the relative interaction index (RII) were significantly higher than 0 under all environmental conditions, demonstrating that plant-plant interactions generated positive effects in the intercropping system. The maize yield and biomass RII were 0.029-0.095 and 0.018-0.066, respectively, which indicated that maize growth was constantly facilitated. However, the RII for grass pea yield and biomass exhibited a different trend in comparison with maize. It was higher than 0 (as the facilitated species) under low soil P and moisture conditions and transitioned to values lower than 0 (facilitator species) under high P and moisture conditions, which showed that the type and intensity of plant-plant interactions steadily shifted with the applied stressors. Direct interactions decreased the maize rhizospheric soil pH by 1.5% and 1.9% under Low-P conditions. Notably, the rhizospheric soil acid and alkaline phosphatase secretions of maize and grass pea increased by 17.4-27.4% and 15.3-27.7%, respectively, in P-deficient soils. These results show that plant-plant interactions can effectively relieve P stress by mineralizing organophosphorus in P-deficient soils. Furthermore, the above tendency became more pronounced under drought-stressed conditions. The nylon barrier partially restricted the exchange and utilization of available nutrients and decreased the total yield and biomass by 1.8-7.8% and 1.1-7.8%, respectively. The presence of a solid barrier completely restricted interspecific rhizospheric interactions and decreased the total yield and biomass by 2.1-13.8% and 1.6-15.7%, respectively. Phytate and KH2PO4 addition intensified asymmetric interspecific competition, and grass pea was consistently subjected to competitive pressures. CONCLUSION: Briefly, the tradeoff between facilitation and competition was driven by rhizospheric interactions, and the transition in the intensity and type of interaction was highly dependent on resource availability in a biologically diverse system.

Dual effects of nZVI on maize growth and water use are positively mediated by arbuscular mycorrhizal fungi via rhizosphere interactions.

Nanoscale zero-valent iron (nZVI) might generate positive and negative effects on plant growth, since it acts as either hazardous or growth-promotion role. It is still unclear whether such dual roles can be mediated by arbuscular mycorrhizal fungi (AMF) in plant-AMF symbiosis. We first identified that in 1.5 g kg-1 nZVI (≤1.5 g kg-1 positively), maize biomass was increased by 15.83%; yet in 2.0 g kg-1 nZVI, it turned to be declined by 6.83%, relative to non-nZVI condition (CK, p < 0.05), showing a negative effect. Interestingly, the inoculation of AMF massively improved biomass by 45.18% in 1.5 g kg-1 nZVI, and relieved the growth inhibition by 2.0 g kg-1 nZVI. The event of water use efficiency followed similar trend as that of biomass. We found that proper concentration of nZVI can positively interact with rhizosphere AMF carrier, enabling more plant photosynthetic carbon to be remobilized to mycorrhiza. The scanning of transmission electron microscopy showed that excessive nZVI can infiltrate into root cortical cells and disrupt cellular homeostasis mechanism, significantly increasing iron content in roots by 76.01% (p < 0.05). Simultaneously, the images of scanning electron microscopy showed that nZVI were attached on root surface to form an insoluble iron ion (Fe3+) layer, hindering water absorption. However, they were efficiently immobilized and in situ intercepted by extraradical hyphae in mycorrhizal-nZVI symbiosis, lowering iron translocation efficiency by 6.07% (p < 0.05). Herein, the optimized structure remarkably diminished aperture blockage at root surface and improved root activities by 30.06% (p < 0.05). Particularly, next-generation sequencing demonstrated that appropriate amount of nZVI promoted the colonization and development of Funneliformis mosseae as dominant species in rhizosphere, confirming the positive interaction between AMF and nZVI, and its regulatory mechanism. Therefore, dual effects of nZVI can be actively mediated by AMF via rhizosphere interactions. The findings provided new insights into the safe and efficient application of nanomaterials in agriculture.

Environmental risk of multi-year polythene film mulching and its green solution in arid irrigation region.

Environmental risk of multi-year polythene film mulching (PM) was evaluated and investigated. The location observation following 19-year (2000-2018) PM in irrigated region indicated that the cumulative accumulation of soil microplastics was as high as 2900 ± 19.5 n kg-1. Microplastic accumulation was tightly associated with soil plasticizer concentration (Pearson's r = 0.728, p <0.05), and the concentration of dominant phthalic acid esters (PAEs) was up to 117.5-705 µg kg-1. As such, we conducted organic mulching substitute experiment (2019-2020) with non-mulching (CK), maize straw mulching (SM), living clover mulching (CM), PM, PM+SM and PM+CM respectively. The data showed that organic mulching (SM, CM) achieved similar productivity benefit as PM-involved treatments (p > 0.05). Critically, total concentration of PAEs decreased by 6.43% in SM relative to CK, and by 9.61% in PM+SM relative to PM respectively. High throughput sequencing indicated that the proportions of predominant bacteria and fungi were totally lower in PM than those of organic mulching, particularly Sphingomonadaceae and Stachybotryaceae. KEGG analyses indicated that organic mulching promoted the metabolisms of polycyclic aromatic hydrocarbons, benzoic acid (probability>75%) and heterologous organism metabolism (p<0.001), due to improved microbial community assembly. Therefore, organic mulching efficiently accelerated microbial mineralization of PM pollutants, and may act as a green solution to displace PM.

[Research Advances in the Diagnostic Value of Rapid On-site Evaluation in Endobronchial Ultrasound-guided Transbronchial Needle Aspiration for Lung Cancer].

Rapid on-site evaluation(ROSE),an auxiliary sampling quality evaluation technology,can be used to evaluate the adequacy and diagnostic category of samples,judge the histological type of lung cancer,and optimize the gene type of lung cancer.Applying ROSE to endobronchial ultrasound-guided transbronchial needle aspiration of suspected lung cancer can improve the puncture success rate and diagnostic rate and reduce complications and puncture attempts.Rose performed via remote cytopathology technology or by trained respiratory specialists may become the future trends.