Response of greenhouse gas emissions, nitrogen loss and microbial communities to the presence of conventional and biodegradable microplastics in soil

Discrepant responses of bacterial community and enzyme activities to conventional and biodegradable microplastics in paddy soil

Integrated microbiota and multi-omics analysis reveal the differential responses of earthworm to conventional and biodegradable microplastics in soil under biogas slurry irrigation

The land application of sewage sludge from wastewater treatment plants has been recognized as a major source of microplastic contamination in soil. Nevertheless, the fate and behavior of microplastics in soil remain uncertain, particularly their distribution and transport, which are poorly understood. This study does a bibliometric analysis and visualization of relevant research publications using the CiteSpace software. It explores the limited research available on the topic, highlighting the potential for it to emerge as a research hotspot in the future. Chinese researchers and institutions are paying great attention to this field and are promoting close academic cooperation among international organizations. Current research hot topics mainly involve microplastic pollution caused by the land application of sewage sludge, as well as the detection, environmental fate, and removal of microplastics in soil. The presence of microplastics in sludge, typically ranging from tens of thousands to hundreds of thousands of particles (p)/kg, inevitably leads to their introduction into soil upon land application. In China, the estimated annual accumulation of microplastics in the soil due to sludge use is approximately 1.7 × 1013 p. In European countries, the accumulation ranges from 8.6 to 71 × 1013 p. Sludge application has significantly elevated soil microplastic concentrations, with higher application rates and frequencies resulting in up to several-fold increases. The primary forms of microplastics found in soils treated with sludge are fragments and fibers, primarily in white color. These microplastics consist primarily of components such as polyamide, polyethylene, and polypropylene. The vertical transport behavior of microplastics is influenced by factors such as tillage, wind, rainfall, bioturbation, microplastic characteristics (e.g., fraction, particle size, and shape), and soil physicochemical properties (e.g., organic matter, porosity, electrical conductivity, and pH). Research indicates that microplastics can penetrate up to 90 cm into the soil profile and persist for decades. Microplastics in sewage sludge-amended soils pose potential long-term threats to soil ecosystems and even human health. Future research should focus on expanding the theoretical understanding of microplastic behavior in these soils, enabling the development of comprehensive risk assessments and informed decision-making for sludge management practices. PRACTITIONER POINTS: Microplastics in sewage sludge range from tens to hundreds of thousands per kilogram. Sludge land application contributes significantly to soil microplastic pollution. The main forms of microplastics in sludge-amended soils are fragments and fibers. Microplastics are mainly composed of polyamide, polyethylene, and polypropylene. Microplastics can penetrate up to 90 cm into the soil profile and persist for decades.

Insights into microplastics in the soil environment: Migration, biodegradation, toxicity and risk assessment

Massive labile carbon and nitrogen inputs into lakes change greenhouse gas emissions. However, the rapid driving mechanism from eutrophic and swampy lakes is not fully understood and is usually contradictory. Thus, we launched a short-term and anaerobic incubation experiment to explore the response of greenhouse gas emissions and microbial communities to glucose and nitrate nitrogen (NO3−-N) inputs. Glucose addition significantly increased CH4 and CO2 emissions and decreased N2O emissions, but there were no significant differences. NO3−-N addition significantly promoted N2O emissions but reduced CH4 accumulative amounts, similar to the results of the Tax4Fun prediction. Bacterial relative abundance changed after glucose addition and coupled with the abundance of denitrification genes (nirS and nirK) decreased while maintaining a negative impact on N2O emissions, considerably increasing methanogenic bacteria (mcrA1) while maintaining a positive impact on CH4 emissions. Structural equation modeling showed that glucose and NO3−-N addition directly affected MBC content and greenhouse gas emissions. Further, MBC content was significantly negative with nirS and nirK, and positive with mcrA1. These results significantly deepen the current understanding of the relationships between labial carbon, nitrogen, and greenhouse emissions, further highlighting that labile carbon input is the primary factor driving greenhouse gas emissions from eutrophic shallow lakes.

Response of greenhouse gas emissions from three types of wetland soils to simulated temperature change on the Qinghai-Tibetan Plateau

Compared with the widespread knowledge about the supply of soil with nutrients for optimal vine growth, the possible effect of microplastics in vineyard soils has not yet been addressed. Little is known about how microplastics may affect the bioavailability and fractionation of nutrients in vineyard soils of contrasting pH. In this study, a 120-day soil incubation experiment was performed to investigate the effect of new and aged polypropylene (PP) microplastics and polyvinyl chloride (PVC) microplastics on the soil pH, nitrogen availability (NH4+ and NO3-) and binding behaviour of macro- (phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg)) and micro-nutrients (iron (Fe), copper (Cu), manganese (Mn) and zinc (Zn)). The results showed that the presence of microplastics in soils increased the pH and decreased the bioavailability of macro- and micronutrients in the soil, with the acid soil being more affected. Furthermore, the presence of PVC microplastics had a stronger impact on nutrient availability than PP microplastics. The most important finding of this study was that micro-PVC particles in soil utterly reduce the bioavailability of nitrate (NO3-) in both calcareous and acid soil samples. This pronounced negative effect was only measured for the micro-PVC particles from the PVC tube ties used in the vineyards and not from the standard PVC material (Sigma Aldrich). Wine producers should be aware that PVC microplastics reduce the bioavailability of nitrate in soils. However, further studies are in progress to clarify the mechanisms involved in the reduction of soil nitrate bioavailability by PVC microplastics from degraded vineyard strings, in particular from the microbial side.

Organic fertilizer and irrigation water are the primary sources of microplastics in the facility soil, Beijing

Microplastics have become a threat to the environment in recent years, and its adverse effect has direct impact on animals and human beings because of its accumulation in the environment. This chapter mainly deals with the source and contamination of microplastics in the agricultural soil and groundwater. Moreover, the experimental approach has been adopted to extract and investigate the presence of microplastics in the soil and groundwater and to classify microplastics based on their physical appearances, such as mass, shape, size, color, and chemical properties like diversity of microplastics characterized using Raman spectroscopy as well as Fourier transform infrared spectroscopy. Sources of microplastics have been reported either in the aquatic environment or in the terrestrial ecosystem, which is widely described and noted down with respective experimental techniques for identification and quantification of microplastics in this chapter. Agricultural soils were stated to be dumping sites for waste collected from households in rural, urban, and industrial areas. Therefore, sewage sludge, industrial effluents, paints, discarded plastics, households materials, and fertilizers are common contributors of microplastics in agricultural soils and groundwater either through biological agents or vertical transport into aquifers. This chapter highlights the source, extraction approach, and quantification techniques for microplastics being applied in numerous research across the globe. The presence of microplastics in soil is affecting soil properties such as water infiltration capacity, bulk density, microbial activity, and soil structure. The chapter analytically argues the recent progress in various extraction, identification, and quantification process aims to identify the pertinent gaps in agricultural soils and groundwater and offers possible solutions by briefing the ongoing investigation to preclude these gaps through applicable scientific interventions.

Response of earthworms to microplastics in soil under biogas slurry irrigation: Toxicity comparison of conventional and biodegradable microplastics

Large amounts of microplastics have been accumulated in soils and their degradation is relatively slow. The residual time of microplastics in soils could be extended to decades or even over a hundred years. Therefore, the ecological effects of long-term residual of the microplastics in soils has been of concerned widely in recent years. Published papers related to the microplastics and their effects in soils were collected and introduced in order to make a full review in the field. The research advances were presented based on the different ecological receptors, which included change of soil physical environment due to the accumulation of microplastics, ingestion of microplastics by invertebrates from soils and their effects on the enteric microorganism, response of soil microbial community and soil enzyme to microplastics pollution, plant uptake of microplastics and their effects. The studies of effects on soil physical environment in the present of microplastics mainly focus on soil density, soil aggregate composition and water hold capacity. Such effects were supposed to have further impacts on soil enzyme activity, microbial community composition and even plant growth based on current limited studies. Many other studies at present were also concentrated on the migration of microplastics induced by soil invertebrates e.g. earthworm, springtail. Meanwhile, microplastics in the soil might be ingested by soil invertebrates and subsequently caused some negative effects and influence on the gut microorganism community of the soil invertebrates. There were also some studies focusing on the microplastics accumulation through food chain regarding the effects of microplastics on soil animals. For example, microplastics might be accumulated in chicken through the predation of earthworm by chicken. After the introduction of current studies, several research proposal were put forward based on the complication of microplastic’s properties and the shortage of current researches. These proposal contained four aspects: (1) development of standard protocols for the study of ecotoxicology of soil microplastics pollution, (2) studying the interaction mechanism between microplastics and microorganisms, plants and invertebrates, (3) revealing microbiological mechanisms that regulation of the transformation of materials and microplastics in soils, (4) exploring plastishere in soils of different ecosystems. All these researches are expected to be supportive to assessment of the ecological effects of soil microplastics pollution. [Ch, 80 ref.]

Effect of different types and shapes of microplastics on the growth of lettuce

Microplastics effects on soil biota are dependent on their properties: A meta-analysis

In the last 20 years, world plastic production has increased rapidly, reaching 4.00 × 1011 kg in 2022. However, less than 10% was recycled. Moreover, most conventional plastics are persistent and, therefore, remain in the environment long after their release. Although most studies on microplastic contamination focus on a single environmental compartment, an integrated and multicompartment approach is highly recommended considering the multitude of interactions between those compartments. This study addresses this knowledge gap, investigating the presence and potential sources of microplastics (MP) in agricultural soils under typical conditions of the Mediterranean region, characterised by dry summers and relatively moist and mild winters (Csa according to the Köppen-Geiger classification). For this, 19 orchards from east-central Portugal were used as case study sites, and a total of 111 samples were analysed. Soil content in MP was assessed in 3 soil layers (0–5, 5–15 and 15–25 cm). To quantify potential sources to soil, information from farmers was used, and samples from irrigation water, atmospheric deposition and manure were analysed. Optical assessment with the assistance of a stereomicroscope was used for MP quantification. The 0–5 cm soil layer showed a lower content (average of 2.2 particles·g−1) and higher particle sizes (average of 168 µm) than deeper soil layers. The identified sources contributed with 1.02 × 105 particles·m−2·year−1. Irrigation water was the main source, representing 55.9% of the aforementioned input rate encountered for the 3 identified MP sources. Additional knowledge is needed regarding the possible variation in MP content throughout the year and between years and the polymer identification, not only in samples collected from soil but also from its main contamination sources. Furthermore, this study should be extended to other crops and regions as part of broader soil health monitoring.

Deciphering the effects of long-term exposure to conventional and biodegradable microplastics on the soil microbiome.