Effect of LDPE microplastics on chemical properties and microbial communities in soil

The accumulation of plastics in the soil ecosystem poses an increasing environmental concern worldwide. However, little is known about the effect of plastic concentrations on soil properties and soil biota. In this study, we investigated the effect of low-density polyethylene (LDPE) microplastics (MPs) on the chemical and microbial properties of agricultural soil using a set of microcosm experiments. The soil was incubated for 100 days with LDPE at concentrations of 0%, 0.1%, 1%, 3%, 5%, and 7% at 25°C with 70% water-holding capacity. Along with soil chemical analysis, we conducted an analysis of soil microbial properties on the first day and again after 100 days of incubation. LDPE concentrations of ≥1% significantly (p < .05) decreased the pH but increased the electrical conductivity of the soil in comparison with the control (0% LDPE at 100 days). Increasing the LDPE concentration did not affect the soil exchangeable cation content or the available Pb concentration. Firmicutes were the most abundant phyla in the soil on the first day, whereas Proteobacteria, Firmicutes and Actinobacteria became dominant in all treatments after 100 days. An increasing LDPE concentration increased the abundance of Actinobacteria and decreased Proteobacteria. Principal component analysis demonstrated that only 7% LDPE was positively correlated with Actinobacteria, indicating that higher concentrations of LDPE contributed to the growth of this phylum. The findings of this study imply that MP contamination could affect soil chemical properties and microbial activity and that these effects primarily depend on MP concentrations in soil.     

Combined effect of biochar and soil moisture on soil chemical properties and microbial community composition in microplastic-contaminated agricultural soil

Accumulation of microplastics (MPs) in agricultural environments has caused growing concern in recent years because of its detrimental impacts on soil quality, crop productivity and ecosystem function. This study was conducted to assess the impact of biochar on soil chemical and microbial properties in a MP-contaminated soil under two moisture regimes. Soil was contaminated with 1% (w/w) of low-density polyethylene MPs. Four types of standard biochar, that is, oil seed rape (OSR) biochar produced at 550°C (OSR 550) and 700°C (OSR 700) and soft wood pellet (SWP) biochar produced at 550°C (SWP 550) and 700°C (SWP 700), were applied at a rate of 5% (w/w). The control was maintained without MP addition. The samples were incubated in soil with two moisture regimes, that is, at 30% and 70% of the water holding capacity, and the soil chemical and microbiological properties were assessed after 100 days of incubation. OSR biochar application significantly increased soil pH (8.53–8.81) and electrical conductivity (0.51–0.58 dS/m) in both moisture regimes. The effect of biochar application on soil enzyme activity and microbial community composition did not show a clear trend. However, SWP 700 biochar improved soil enzyme activity compared with that of the control and improved bacterial diversity and evenness compared with those of other biochars, which was attributed to the high surface area available for microbial colonization. Low soil moisture content significantly reduced enzyme activity and bacterial richness even with biochar amendment, except for SWP 550 biochar. This study implies the suitability of biochar for improvement of soil quality in MP contaminated soil under both moisture regimes. However, further long-term studies are needed to get a clear understanding on the impact of different types of biochar on MP-contaminated soil.     

根用芥菜贮藏中品质和超微结构的变化

以根用芥菜为试材,采用PE包装的方法,在低温(2±1)℃下贮藏,研究0.01 mm PE保鲜膜包装对根用芥菜贮藏中品质和超微结构的影响,以期为根用芥菜的贮藏提供参考依据。结果表明:0.01 mm PE保鲜膜可以抑制根用芥菜失重率上升,减缓呼吸速率,延缓硬度下降,抑制纤维素含量上升,增加过氧化氢酶和超氧化物歧化酶活性,同时延缓细胞间隙的增加、改善其风味物质,有效延长其贮藏期。     

葡萄柚籽提取物和聚乙烯包装对香椿贮藏品质的影响

香椿（Toona sinensis）的嫩叶和嫩芽营养丰富，风味独特，但香椿属于季节性蔬菜，极易腐烂，严重影响货架期。葡萄柚籽提取物（grapefruit seed extract，GSE）是天然的强抗氧化剂、天然防腐剂。使用0.02 mm厚度的聚乙烯（polyethylene，PE）薄膜包装香椿并利用0.1%、0.3%和0.5%浓度的GSE进行处理，研究不同处理下贮藏期间香椿感官品质与理化指标的影响。结果表明：不同处理均具有一定的保鲜效果。其中，0.5% GSE+PE处理可以显著延缓香椿褐变和腐烂，降低失重率，控制叶绿素含量的升高，抑制呼吸速率和乙烯释放速率。研究结果为香椿的采后保鲜提供了重要的理论依据和实践参考。     

PEG预处理对青稞种子萌发、幼苗生长和抗旱性的影响

以抗旱性弱的青稞品种''大麻青稞’为材料,研究不同质量分数(5%~30%)聚乙二醇(PEG)预处理对其种子萌发、幼苗生长和抗旱性的影响。结果表明,1)随着PEG预处理质量分数的增加,''大麻青稞’种子的发芽率和生根率,幼苗的根长、苗高和鲜重均呈先增加后降低的趋势;种子的发芽率、生根率、幼苗的根长和苗高均在10%的PEG处理下值最高,分别为对照的1.14、1.05、1.24和1.33倍,且除生根率外,其他指标均与对照差异极显著(P<0.01);叶片可溶性蛋白和叶绿素先增加后降低,而丙二醛含量和相对电导率则先降低后增加,并在15%PEG处理下最佳,分别为对照的1.38、1.84、0.65和0.71倍,且与对照差异极显著(P<0.01);2)当幼苗经30%PEG重度胁迫时,其叶片蛋白质和叶绿素含量分别比胁迫前下降42.11%和38.98%,而经15%PEG预处理的两者含量比胁迫对照组提高了42.80%和1.01倍;经30%PEG重度胁迫后相对电导率和丙二醛含量分别比胁迫前上升了28.24%和6.04%,而经15%PEG预处理的两者含量比胁迫对照组降低了28.64%和33.41%。表明低质量分数的PEG对青稞种子的萌发和幼苗的生长生理特性具有促进作用,高质量分数的PEG处理对植物的生长产生了抑制作用。