The occurrence of microplastics in farmland and grassland soils in the Qinghai-Tibet plateau: Different land use and mulching time in facility agriculture.

Plastic particles of less than 5 mm size, referred as microplastics, have recently become a major environmental issue. While microplastics are well known in marine and lake systems, there have been less investigations in soils and groundwater. Here we review the origin, shape, impact, and mitigation strategies of soil and groundwater microplastics. We found that littering is the main origin of microplastics in global topsoils, while greenhouses are the main source of microplastics in South Korea. Fibers and pellets are dominant microplastic shapes in soil and groundwater. Microplastic contamination of soil and groundwater is detrimental to human health, plants, nematodes, earthworms, and soil properties. Remediation methods include pyrolysis, replacing plastics by biodegradable plastics, plastic filtration, and subsequent chemical or biological degradation.

Microplastic pollution in soil and groundwater: a review

Current progress on plastic/microplastic degradation: Fact influences and mechanism.

A critical review of microplastics in the soil-plant system: Distribution, uptake, phytotoxicity and prevention.

A critical review of microplastics in the soil-plant system: Distribution, uptake, phytotoxicity and prevention

Distinct microplastic distributions in soils of different land-use types: A case study of Chinese farmlands.

Microplastics (MPs), tiny particles broken down from larger pieces of plastics, have accumulated everywhere on the earth. As an inert carbon stream in aquatic environment, they have been reported as carriers for heavy metals and exhibit diverse interactive effects. However, these interactions are still poorly understood, especially mechanisms driving these interactions and how they pose risks on living organisms. In this mini review, a bibliometric analysis in this field was conducted and then the mechanisms driving these interactions were examined, especially emphasizing the important roles of microorganisms on the interactions. Their combined toxic effects and the potential hazards to human health were also discussed. Finally, the future research directions in this field were suggested. This review summarized the recent research progress in this field and highlighted the essential roles of the microbes on the interactions between MPs and heavy metals with the hope to promote more studies to unveil action mechanisms and reduce/eliminate the risks associated with MP presence.

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Interactions Between Microplastics and Heavy Metals in Aquatic Environments: A Review

Microplastics (MPs) are ubiquitous in the aquatic environment and can be frequently ingested by zooplankton, leading to various effects. Brine shrimp (Artemia parthenogenetica) has an important role in the energy flow through trophic levels in different seawater systems. In this work, the influence of polyethylene (PE) and polystyrene (PS) MPs on the growth of brine shrimp and corresponding changes of gut microbiota were investigated. Our results showed that the MPs remarkably reduced the growth rate of brine shrimp, and the two types of MPs have different impacts. The average body length of brine shrimps was reduced by 17.92 and 14.95% in the PE group and PS group, respectively. MPs are mainly found in the intestine, and their exposure evidently affects the gut microbiota. By using 16S rRNA gene high-throughput sequencing, 32 phyla of bacteria were detected in the intestine, and the microbiome consisted mainly of Proteobacteria, Firmicutes, and Actinobacteria. MPs' exposure significantly increased the gut microbial diversity. For the PE group, the proportion of Actinobacteria and Bacteroidetes increased by 45.26 and 2.73%, respectively. For the PS group, it was 54.95 and 1.27%, respectively. According to the analysis on genus level, the proportions of Ponticoccus, Seohaeicola, Polycyclovorans, and Methylophaga decreased by 46.38, 1.24, 1.07, and 2.66%, respectively, for the PE group and 57.87, 1.43, 0.88, and 2.24%, respectively, for the PS group. In contrast, the proportions of Stappia, Microbacterium, and Dietzia increased by 1.12, 23.27, and 11.59%, respectively, for the PE group, and 1.09, 3.79, and 42.96%, respectively, for the PS group. These experimental results demonstrated that the ingestion of MPs by brine shrimp can alter the composition of the gut microbiota and lead to a slow growth rate. This study provides preliminary data support for understanding the biotoxicity of MPs to invertebrate zooplankton and is conducive to the further risk assessment of MP exposure.

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Li Jiayao

Papers

Distinct microplastic distributions in soils of different land-use types: A case study of Chinese farmlands.

Interactions Between Microplastics and Heavy Metals in Aquatic Environments: A Review

Influence of Microplastics on the Growth and the Intestinal Microbiota Composition of Brine Shrimp.