[Effect of Polyethylene Microplastics on the Microbial Community of Saline Soils].

Mulching to conserve moisture has become an important agronomic practice in saline soil cultivation, and the effects of the dual stress of salinity and microplastics on soil microbes are receiving increasing attention. In order to investigate the effect of polyethylene microplastics on the microbial community of salinized soils, this study investigated the effects of different types (chloride and sulphate) and concentrations (weak, medium, and strong) of polyethylene (PE) microplastics (1% and 4% of the dry weight mass of the soil sample) on the soil microbial community by simulating microplastic contamination in salinized soil environments indoors. The results showed that:PE microplastics reduced the diversity and abundance of microbial communities in salinized soils and were more strongly affected by sulphate saline soil treatments. The relative abundance of each group of bacteria was more strongly changed in the sulphate saline soil treatment than in the chloride saline soil treatment. At the phylum level, the relative abundance of Proteobacteria was positively correlated with the abundance of fugitive PE microplastics, whereas the relative abundances of Bacteroidota, Actinobacteriota, and Acidobacteria were negatively correlated with the abundance of fugitive PE microplastics. At the family level, the relative abundances of Flavobacteriaceae, Alcanivoracaceae, Halomonadaceae, and Sphingomonasceae increased with increasing abundance of PE microplastics. The KEGG metabolic pathway prediction showed that the relative abundance of microbial metabolism and genetic information functions were reduced by the presence of PE microplastics, and the inhibition of metabolic functions was stronger in sulphate saline soils than in chloride saline soils, whereas the inhibition of genetic information functions was weaker than that in chloride saline soils. The secondary metabolic pathways of amino acid metabolism, carbohydrate metabolism, and energy metabolism were inhibited. It was hypothesized that the reduction in metabolic functions may have been caused by the reduced relative abundance of the above-mentioned secondary metabolic pathways. This study may provide a theoretical basis for the study of the effects of microplastics and salinization on the soil environment under the dual pollution conditions.

[Response of Relationship Between Microplastic Abundance and Nitrogen Metabolism Function Microorganisms and Genes in Water].

The impact of microplastics (MPs) as a new type of pollutant on water pollution has become a research hotspot. To explore the response relationship between the abundance of MPs and nitrogen metabolism function in a freshwater environment, Lake Ulansuhai was used as the research object; the abundance of MPs in the water was detected using a Zeiss microscope, and the distribution characteristics of nitrogen metabolism functional bacteria and functional genes in the water were analyzed using metagenomics sequencing. The correlation analysis method was used to explore the relationship between the abundance of MPs and nitrogen metabolism functional microorganisms and nitrogen metabolism functional genes. The results showed that the presence of MPs in freshwater environments had a higher impact on Cyanobacteria and Firmicutes as the dominant phyla, and the presence of MPs promoted their enrichment and growth. Among the dominant bacterial genera, MPs promoted the growth of Mycobacterium and inhibited Candidatus_Planktopila more significantly, further indicating that in freshwater environments, MPs affected normal nitrogen metabolism by affecting microbial communities, and pathways such as carbon and nitrogen fixation and denitrification were important pathways for MPs to affect nitrogen metabolism. From the perspective of nitrogen metabolism functional genes, it was found that the abundance of MPs significantly affected some functional genes during nitrification (pmoA-amoA, pmoB-amoB, and pmoC-amoC), denitrification (nirK and napA), and dissimilatory nitrate reduction (nrfA) processes (P < 0.05). Moreover, the influence of MPs abundance on different functional genes in the same pathway of nitrogen metabolism varied, making the impact of MPs on aquatic environments very complex; thus, its harm to the water environment cannot be underestimated.

[Effect of Microplastics on Soil Water Infiltration and Evaporation].

In order to explore the influences of microplastics with different abundances (0.5%, 1%, and 2% of the dry weight of the soil) and different types (PP, PVC, and PE) on the moisture infiltration and evaporation of the soil, we adopted the method of indoor soil column simulation to elaborate the influences of the microplastics with different abundances and different types on the moisture accumulated infiltration time, moisture containing rate, wetting front, and evaporation characteristics, among which the A1, A2, and A3; Q1, Q2, and Q3; and Z1, Z2, and Z3 respectively represented the experimental number of PE, PVC, and PP under the abundances of 0.5%, 1%, and 2%. The influences of the microplastics with different types and different abundances on the moisture infiltration and evaporation of the soil showed obvious differentiation. Under the same types of conditions, when the abundances of the microplastics increased, the accumulated infiltration time also increased significantly. However, under the occurrence condition of the microplastics of different types but the same abundances, the accumulated infiltration time of the PP experiment group>that of the PVC experiment group>that of the PE experiment group>that of the blank experiment group. Under the occurrence condition of microplastics, the maximum moisture rate of the soil basically appeared at the depth from 10 to 25 cm, and the CK of the blank group appeared at the depth from 20-25 cm. Within the same infiltration time, when the abundances of the microplastics increased, the moving distance and the moving rate of wetting front of the soil decreased accordingly. When the infiltration time was 60 minutes, the wetting moving distances of A1, A2, and A3; Q1, Q2, and Q3; and Z1, Z2, and Z3, respectively, decreased 4.38%, 8.76%, and 10.58%; 7.30%, 10.22%, and 14.60%; and 10.95%, 13.14%, and 15.33% compared to those of the CK groups, among which the influence of PP microplastics was the most significant. The occurrence of the microplastics had a prohibition function to the moisture evaporation of the soil; when the microplastics had the same types, the accumulated amount of the soil decreased with the increase in abundance. When evaporating for 27 hours, the accumulated evaporation amount of the experiment soil column of PP, PVC, and PE microplastics with the added abundances of 2% respectively decreased 22.9%, 19.4%, and 13.3% compared to that in the CK. The Rose evaporation model relatively truly reflected the changing situation of the soil accumulated evaporation amount with time under the occurrence situation of the microplastics. This research can provide a theoretical basis for the changing study of the soil moisture movement under the occurrence condition of microplastics.

[Occurrence Characteristics and Quality Estimation of Microplastics in Drainage Ditches in Hetao Irrigation District of Inner Mongolia].

Microplastic pollution due to land runoff has gained increasing attention as it is closely associated with human beings. In this study, we analyzed the occurrence characteristics of microplastics in drainage channel and main drainage channel in Hetao irrigation district of Inner Mongolia and estimated its quality. Through field sampling, the density separation of suspension method and microscope observation, Fourier infrared spectrum measurement, and proportional flow method, the abundance distribution, shape, color, particle size, and chemical composition of microplastics in the water body and sediment of the drainage channel and main drainage channel in the Hetao irrigation district were identified. The mass of microplastics transported in the main drainage channel was also estimated. The results showed that the value range of microplastic abundance in the water body of the drainage channel and the main drainage channel in Hetao irrigation district was 2880-11200 n ·m-3, and the value range of microplastic abundance in the sediment was 100-292 n ·kg-1. Fiber was the most common microplastic form, occupying 34.98%-70.39% and 42.24%-58.56% in the water and sediment, respectively. The color of microplastics was mainly transparent, which occupied 46.43%-61.51% and 40.41%-57.44% in the water and sediment, respectively. The largest particle size of microplastics was<0.5 mm, accounting for 46.43%-61.51% and 43.27%-54.79% in the water and sediment microplastics, respectively. It was concluded that polyethylene was the most common type (43%), followed by polystyrene (34%) and polypropylene (16%) using Fourier infrared spectroscopy. It was estimated that the main drainage channel in the Hetao irrigation district could transport 116.06 kg of microplastics into Lake Ulansuhai every day, and a serious microplastic pollution effect was generated due to the accumulation of microplastics in Lake Wulangsuhai. This study can provide reference for the pollution of microplastics in Hetao irrigation district of Inner Mongolia.

Isolation and characterization of mesophilic cellulose-degrading bacteria from flower stalks-vegetable waste co-composting system.

Fifteen mesophilic bacteria with high C(x) cellulase activities were isolated and purified from a mixed-culture enriched from a flower stalks-vegetable waste co-composting system. A CMCase test showed that the enzyme activity of these isolates ranged from 7.9 to 28.0 U ml(-1). Although filter paper degrading capability was low in single culture, significant synergetic cellulose degradation were detected in four groups of mixed cultures, their degradation rates were 23.5%, 26.3%, 19.4% and 24.5%, respectively. Study of morphological and physiological characters of five predominant isolates which possess high CMCase and had positive effect on synergetic cellulose degradation in mixed culture system showed that two of them were closely related to Bacillus pasteurii and Bacillus cereus, whereas the rest belong to the genus Halobacillus, Aeromicrobium and Brevibacterium, respectively.

[Application of high-efficient cellulose utilization microorganisms in co-composting of vegetable wastes and flower stalk].

An inoculation composing 17 species of cellulose utilization microorganisms was used in co-composting of vegetable wastes and flower stalk, and the efficiency of the inoculation on lignocellulose degradation was studied. The experiments result show that at the beginning of the first stage of composting, inoculating cellulose utilization microorganism in the substrates with 0.5% (V/V) can improve the biomass of the microorganisms into the substrates greatly and make them dominant ones. When the temperature was controlled as 55 degrees C, the biomass of cellulose utilization microorganisms can keep between [symbol: see text] 3.84 x 10(9)-1.80 x 10(10) CFU/g. At the beginning of the second stage, inoculating with 1% (V/V) can improve the temperature during this period effectively. Monitoring of the content of lignocelluloses in the substrate shows that the inoculation of cellulose utilization microorganism can accelerate the degradation of cellulose. The degradation efficiency of cellulose under inoculation condition is 23.64% higher than those without inoculation. This shows that inoculating with cellulose utilization microorganisms in each stage of the composting can greatly decompose the lignocellulose in the substrates, accelerate the co-composting process and improve the quality of composting production.

Effect of inoculating flower stalks and vegetable waste with ligno-cellulolytic microorganisms on the composting process.

A lab-scale composting experiment was carried out using vegetable and flower stalks waste to study the effectiveness of ligno-cellulolytic microorganisms (LCMs) obtained from the previous isolation on composting process, especially on enhancement of biodegradation rate of these organic materials. The addition of LCMs to compost showed promised to be a valuable asset by rendering timely benefits in efficiency, maturity, and quality of the composting. This was evidenced by a significant increase of temperature, O2 consumption and CO2 emission, and population density of LCMs in compost mass compared with that of biotic (addition of culture of horse feces) and abiotic (1% molasses amendment) treatments, as well as control trial. The phytotoxicity assay showed that the substrate became mature after 60 days' composting. The LCMs inoculation enhanced the biodegradation of the composting materials as evidenced by an increasing screening ratio (1.2 cm sieve pore) of 34.5% in the treated trail, compared with that of control, which elucidated that big advantage of adding selected inoculants over other treatment, and screening ratio is a reasonable index to compare the quality of different compost. However, the inoculation seemed to have no significant effect on the moisture content, pH, and the final organic carbon of the composting materials.