Extraction and decontamination of microplastics from high organic matter soils: A simple, cost-saving and high efficient method.

This article introduces a simple, cost-saving and high efficient for the extraction and separation of microplastics (MPs) from soil with a high organic matter (SOM) content. In this study, MP with particle sizes of 154-600 µm of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC) and polyethylene terephthalate (PET) were artificially added into the five Mollisols with the high SOM. Three flotation solutions were used to extract these MPs from soils, and four digestion solutions were used to digest the SOM. As well, their destruction effects on MPs were also examined. The results showed that the flotation recovery rates of PE, PP, PS, PVC and PET were 96.1%-99.0% by ZnCl2 solution, while were 102.0%-107.2% by rapeseed oil, were 100.0%-104.7% by soybean oil. The digestion rate of SOM was 89.3% by H2SO4:H2O2 (1:40, v:v) at 70 °C for 48 h, and this was higher than by H2O2 (30%), NaOH and Fenton's reagent. However, the digestion rate of PE, PP, PS, PVC and PET were 0.0%-0.54% by H2SO4:H2O2 (1:40, v:v), and this was lower than by H2O2 (30%), NaOH and Fenton's reagent. As well, the factors influencing on MP extraction was also discussed. Generally, the best flotation solution was ZnCl2 (ρ > 1.6 g cm-3) and the best digestion method was H2SO4:H2O2 (1:40, v:v) at 70 °C for 48 h. The optimal extraction and digestion method were verified by the known concentrations of MPs (recovery rate of MPs was 95.7-101.7%), and this method was also used to extract MPs from long-term mulching vegetable fields in Mollisols of Northeast China.

Lewis Acid Mediated Tandem Reaction of Propargylic Alcohols with Hydroxylamine Hydrochloride To Give α,ß-Unsaturated Amides and Alkenyl Nitriles.

We have developed a highly selective method for the synthesis of α,ß-unsaturated amides and alkenyl nitriles from readily available propargylic alcohols. The reaction proceeded smoothly under the neutral conditions with hydroxylamine hydrochloride (NH2OH·HCl) as the nitrogen source. The development of these new strategies has significantly extended the application of hydroxylamine hydrochloride to the chemistry of propargylic alcohols. Moreover, both secondary and tertiary alcohols have been highly regioselectively transformed to the desired products with good functional group compatibility.

BF3·Et2O-promoted cleavage of the Csp-Csp2 bond of 2-propynolphenols/anilines: route to C2-alkenylated benzoxazoles and benzimidazoles.

A novel BF3·Et2O-promoted tandem reaction of easily prepared 2-propynolphenols/anilines and trimethylsilyl azide is developed to give C2-alkenylated benzoxazoles and benzimidazoles in moderate to good yields. Most reactions could be accomplished in 30 min at room temperature. This tandem process involves a Csp-Csp2 bond cleavage and a C-N bond formation. Moreover, both tertiary and secondary propargylic alcohols with diverse functional groups were tolerated under the mild conditions.

TMSCl-mediated synthesis of α,ß-unsaturated amides via C-C bond cleavage and C-N bond formation of propargyl alcohols with trimethylsilyl azide.

A new method with high efficiency for the synthesis of α,ß-unsaturated amides from the easily prepared propargyl alcohols and TMSN3 using TMSCl as an acid promoter is developed. A wide variety of α,ß-unsaturated amides were produced in moderate to excellent yields. Mechanistic studies indicate that this transformation involves TMSCl-mediated allenylazide intermediate formation, C-C bond cleavage, and C-N bond formation. Significantly, this reaction shows good functional group compatibility and high regioselectivity, with a relatively short reaction time and inexpensive reagents.

Copper-catalyzed one-pot trifluoromethylation/aryl migration/carbonyl formation with homopropargylic alcohols.

A novel copper-catalyzed one-pot functionalization of homopropargylic alcohols that involves trifluoromethylation, aryl migration, and formation of a carbonyl moiety has been developed. This reaction constitutes the first direct conversion of homopropargylic alcohols into CF3-containing 3-butenal or 3-buten-1-one derivatives in a regioselective manner. Mechanistic studies indicate that the 1,4-aryl migration proceeds through a radical pathway.

Crops Change the Morphology, Abundance, and Mass of Microplastics in Mollisols of Northeast China.

Degradation of microplastics (MPs) by both physicochemical and biological processes in the natural environment is determined by the enzymes inside the soil, and which was severely influenced by crop growth and straw amendment (SA). However, it is still unclear how crop growth and SA influence degradation of MPs in soils. In this study, both catalase and sucrase were measured, and the stereomicroscope combined with microscopic infrared spectroscopy and scanning electron microscope (SEM) was used to detect the morphology and quantity of low-density polyethylene microplastic (LDPE-MP) and low-density polypropylene microplastic (LDPP-MP), after crop growth (maize and soybean, with and without SA, 1 and 2% MP) in an outdoor pot experiment, in the Mollisols. The results showed that the growth of the crops changed the morphology, functional groups (e.g., methylene, carbonyl), total mass, and abundance ratio of MPs of different sizes. These were possibly caused by enzymes that were significantly influenced by crop types, abundance, and types of MPs in the soils. Maize growth decreased the mass of LDPE-MP and LDPP-MP by 28.7 and 32.7%, respectively, and 2% (w/w) of LDPP-MP addition in soil decreased mass of 9%, which was higher than that in 1% (w/w) LDPP-MP addition in soil. Soybean growth with SA decreased the mass of LDPE-MP and LDPP-MP by 36.6 and 20.7%, respectively, than the control treatment (CK). Compared with CK, both crop growth and SA changed the abundance of MPs of different sizes and decreased the mean size of MPs. The LDPE-MP could be more easily degraded by enzymes in the soils compared to LDPP-MP when the MP size was smaller with surface roughness. Generally, both maize and soybean growth can accelerate MP change in soils, and MP change process was mainly determined by SA, MP types, and the dose effect of MP.

Field management changes the distribution of mesoplastic and macroplastic in Mollisols of Northeast China.

Mesoplastic (MaP) and macroplastic (MeP) coming from plastic mulching tend to cause negative effects on biota in ecosystems. However, it is still not clear how field management influences the distribution of MeP/MaP in soils. In this study, MeP/MaP was investigated in 0-20 and 20-30 cm soil layers of three vegetable fields (3.4-6.5 ha) after 13 years plastic-mulching in Mollisols of Northeast China under different management methods (MM) of fertilization and tillage frequency. The tillage frequency was MM2 > MM1 > MM3, while the fertilization was MM1 > MM2 > MM3. The results showed that polyethylene (PE), polypropylene (PP), polystyrene, polyvinyl chloride, polyethylene terephthalate (PET), polyamide, melamine-formaldehyde resin and polyether urethane were found in soil, and PE (>83.76%, from plastic mulching) was the predominant type of MeP/MaP. MeP abundance was significantly (p < 0.05) higher in MM1 and MM2 than that in MM3 in the 0-20 cm soil layer. MM1 and MM2 had the highest abundance of MeP/MaP of size <4 cm2 and 4-16 cm2, while MM3 had the highest abundance at the size >16 cm2. The broken index of MeP/MaP was significantly (p < 0.05) lower in MM2 compared with MM1 and MM3 in the 20-30 cm soil layer. Both tillage frequency and fertilization accelerate the breaking of plastics, especially since the influence was stronger from fertilization. Compared with original plastics, the PE, PP and PET's carbonyl index was significantly (p < 0.05) higher in the three MMs. Generally, fertilization and frequent tillage can reduce the physical effects of large-sized plastic debris on crop growth and increases the negative effects of small-sized plastic and new pollutants formed on biota in the agroecosystems. MeP/MaP recycling should be strengthened, and the irrigation and rotation of farmland should be carried out when the wind speed is weak to avoid plastic invasion.

Non-biodegradable microplastics in soils: A brief review and challenge.

Non-biodegradable microplastics (MPs) pollution long-termly existed in soils, and was only concerned in recent years. In order to better understand MP behavior in soils, the sources, migration, distribution, biological effects, degradation and analytical methodology of non-biodegradable MPs in soils were quantificationally summarized from 170 publications based on Web of Science in 1950-2020. From the publications, we found these studies were mainly carried out in the Asia (60.0%) and Europe (23.3%), and most were on agricultural soils (68.5%). Polyethylene-MP (78.8% of the studies), Polypropylene-MP (78.8%), and Polystyrene-MP (45.5%) were the MPs most frequently found in the soils, with a MP size of 20-5000 µm being most common. Of the soil samples 64.3% contained MP 1000-4000 items kg-1, and the colour frequency ranking is blue (66.7%) > white (61.1%) ≈ red ≈ black. MPs changed the soil microenvironment and microorganism activity, and caused the negative effects on both soil animals (100%) and plants (57.9%). MP degradation was influenced by the photooxidation reactions, microorganism activities, enzymatic effects, environmental conditions, and by the composition, size and morphology of the MPs. An optional analytical method was suggested in this study. At the end of paper, the urgent and important research work in the future was prospected.

Fertilization accelerates the decomposition of microplastics in mollisols.

Agricultural films composed of low-density polyethylene (LDPE) have been widely used in farmland, and LDPE microplastics (LDPE-MPs) produced from LDPE degradation can pollute soils and can exert negative effects on biota. Both nitrogen (N) and phosphorus (P) can alter the activity of soil microorganisms and may alter the LDPE-MP degradation process in soils. In this study, LDPE-MP surface morphology, particle size, abundance and mass in a mollisol were evaluated after the application of a gradient of N and P fertilizer in a laboratory incubation experiment. The results showed the following: (1) LDPE-MP particles became fragmented into smaller debris with a coarse surface after 40 days of incubation, and the effect was more obvious with increased P or N application; (2) high N and P fertilization significantly reduced the abundance of LDPE-MP particles >100 µm by 38.5-50.0% and increased the abundance of LDPE-MP particles <20 µm by 43.2-59.5% after 40 days of incubation; (3) high N and P fertilization significantly increased the mass of LDPE-MP particles <75 µm by 25.5-60.1% and decreased the mass of LDPE-MP particles >150 µm by 32.4-37.5%; (4) the mass of LDPE-MPs decreased with increasing incubation time after N and P fertilization, which could be simulated by exponential models (p < 0.05), LDPE degradation was rapid in the first 20 days after N or P fertilization, and both N and P caused a "priming effect" of LDPE degradation; and (5) N and P fertilization increased both the biodiversity and abundance of several predominant genera of soil microorganisms that degrade LDPE. Therefore, N and P fertilization can accelerate LDPE-MP degradation, and the relatively large amounts of fine debris from degraded LDPE-MPs can be problematic for the environment and soil biota. LDPE-MP pollution should be strictly controlled in mollisols, and the degradation mechanisms of LDPE-MPs warrant further study.

Distribution of low-density microplastics in the mollisol farmlands of northeast China.

Plastic pollution, especially microplastic (MP), which is small in size (<5 mm) is one of the main environmental problems in global ecosystems and can cause harm to organisms. Low-density plastic has been widely used in farmlands, but the factors that influence Low-density microplastic (LDMP) distribution are still not clear. In this study, both field investigations at small and large scales and laboratory simulations, and both geostatistics and classical statistics were used to examine LDMP distributions and the main driving factors in farmland soils. The results showed the following. (1) Only polyethylene (PE) of LDMP was found in farmland. (2) The means of LDMP weight content (LDMP-W), LDMP abundance (LDMP-AB) and LDMP area content (LDMP-A) were 0.27 mg kg-1, 107 N kg-1 and 12.6 mm2 kg-1 in mollisol farmlands, respectively. (3) LDMPs were positively correlated with macroplastics (MAP) at the large scale, while any correlations were not obvious at small scales. (4) LDMPs were not only transported by surface soil-water loss (>96%) but were also transported by infiltration through soil pores (<4%). (5). LDMP loss increased with soil bulk density (BD) increasing, and low BD tends to increase LDMP loss by interflow. (6) LDMP distribution was not only influenced by water movement but also maybe influenced by microorganisms and crops. For LDMP pollution control, the focus on both surface soil-water loss and the infiltration processes is necessary, and a combination of the functions of microorganisms and crops probably accelerate LDMP decomposition in soils.

Palladium-Catalyzed Intramolecular Dearomatization of Indoles via Decarboxylative Alkynyl Termination.

A highly diastereoselective dearomatization of indoles via palladium-catalyzed decarboxylative alkynyl termination was developed. This protocol provides dissimilar tetracyclic and tetrasubstituted indoline scaffolds bearing congested stereocenters, which led to operationally simple conditions, short time, and broad substrate scope. Additionally, this reaction system could be scaled to gram quantities in a satisfactory yield and diastereoselectivity.

Study on the role of hepatic first-pass elimination in the low oral bioavailability of scutellarin in rats.

In the present study, we compared the systemic exposure of scutellarin following intraportal with intravenous administration to understand the contribution of presystemic hepatic elimination to the low oral bioavailability. Results showed that the hepatic first-pass elimination of scutellarin played an insignificant role in the presystemic elimination of orally administered scutellarin. Moreover, our results suggested that the site of first pass extraction was not the liver, but the gastrointestinal tract.

Metal-free nitro-carbocyclization of 1,6-enynes with (t)BuONO and TEMPO.

A novel and convenient metal-free nitration and cyclization of 1,6-enynes has been developed. Two C-C bonds and one C-N bond were constructed in one process in this reaction. This transformation is proven to have relatively good functional-group applicability and can be scaled up to gram quantities in satisfactory yields. According to the following experimental facts and related literature reports, a radical pathway was involved in this transformation.

Palladium-catalyzed ring opening of norbornene: efficient synthesis of methylenecyclopentane derivatives.

The first palladium-catalyzed ring opening of norbornene to prepare methylenecyclopentane derivatives has been established. The process, which uses readily available aryl iodides, tosylhydrazones and norbornene as starting materials, likely takes place via tandem Heck-type coupling, palladium carbene migratory insertion, C-C bond cleavage and the ß-hydride elimination pathway in a single synthetic sequence.

Facile synthesis of disubstituted isoxazoles from homopropargylic alcohol via C═N bond formation.

A novel iron-catalyzed aerobic oxidative reaction to synthesize disubstituted isoxazoles from homopropargylic alcohol, t-BuONO, and H2O is developed. The method provides mild conditions to afford a variety of useful substituted heterocycles in an efficient and regioselective manner. The mechanism has been studied and proposed, which indicates that the transformation can be realized through construction of a C═N bond and C═O bond, C-H oxidation, and then cyclization. Moreover, this method can be enlarged to gram scale.