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Low-density polyethylene microplastics as a source and carriers of agrochemicals to soil and earthworms
Abstract
Microplastics (MPs) are of environmental concern to marine ecosystems owing to the evidence of their presence in and adverse effects on organisms, but studies to address this problem on soils and its biota are scarce. Several questions can arise related to this major environmental problem and its impact on terrestrial ecosystems, mainly, whether MPs can transport contaminants (e.g. pesticides) to the soil matrix and if they can be a carrier of pesticides to soil biota. To contribute to the understanding of these issues, earthworms (Eisenia fetida) were exposed for 14 days to soil containing two different sized MPs (5 mm and 0.25 µm–1 mm) that were either previously sprayed or not with chlorpyrifos (CPF). Acetylcholinesterase (AChE) activity and thiobarbituric acid reactive substances (TBARS) were measured to track the exposure of the earthworms to MPs, both non-sprayed and sprayed with CPF. The behaviour of the earthworms in the test containers and the movement of MPs in the soil were assessed. The concentration of CPF in soil at the end of the experiment differed between the treatments with MPs of different sizes (17.9 ng g−1 and 2442 ng g−1 for large and small MPs, respectively). Despite the ability of the MPs to release CPF to the soil, the earthworms avoided the contaminated MPs at the highest contaminant level. At a lower concentration of CPF (large MPs), the earthworms avoided the MPs, but the contact time with contaminated soil was higher, as shown by the enhanced level of TBARs and AChE inhibition. However, no evidence of MPs uptake was recorded, thus it was not demonstrated that MPs can be carriers of pesticides to earthworms.
... The balance between these two contrasting processes was dependent on the chemical properties of the pesticides, as well as on the thickness and size of film pieces. In this regard, chlorpyrifos was confirmed to be released from contaminated low-density PE to the soil at rates that were dependent on particle size [136]. Recent research has corroborated that, in soil ecosystems, MPs could act as carriers of pesticides, thus increasing the risk of their mobility through the soil matrix or to other environmental compartments. ...
... An alternative pathway for pesticides to reach deeper soil layers is co-transport with MPs by the action of soil organisms such as earthworms, although contradictory results have been published. On one hand, Rodríguez-Seijo et al. [136] could not demonstrate if low-density PE can be an efficient carrier of chlorpyrifos to earthworms. However, this MP increased the total amounts of glyphosate [142] and chlorpyrifos [143] transported by earthworms. ...
... Rodríguez-Seijo et al. [136] also evaluated the behavior and enzyme activity of E. fetida when exposed in the soil to a mixture of two sizes of MPs and chlorpyrifos. The authors confirmed the inhibition of acetylcholinesterase activity, as well as the release of the insecticide from the MPs. ...
In the middle of the 20th century, the production of plastics exploded worldwide because of their low cost and the versatility of their applications. However, since plastic debris is highly resistant to environmental degradation, a growing presence of plastics in all the ecosystems has been confirmed. Among them, plastic particles < 5 mm, also known as microplastics (MPs), are of special concern because they are dispersed in aerial, terrestrial and aquatic environments, being the soil the main environmental sink of these contaminants. Due to their large specific surface area and hydrophobicity, MPs are considered good adsorbents for other environmental organic pollutants also present in terrestrial ecosystems, such as pharmaceuticals, personal-care products or pesticides with which they can interact and thus modify their environmental fate. In this review article, we examine the recent literature (from 2017 to 2022) to get a better understanding of the environmental fate of pesticides in soil (adsorption, mobility and/or degradation) when they are simultaneously present with MPs and the ecological risks on living organisms of the interactions between MPs and pesticides in soil. More studies are needed to fully understand the toxicological impact of the copresence in soil of pesticides and MPs.
... In addition, aquatic biota may have mistakenly ingested plastic particles as food, thus serving as carriers of plastic particles that are then metabolized and transported to different regions of the water or reintegrated into the food chain and returned to the mainland [37,[118][119][120]. When plastic particles contact the soil on land, large-sized plastic particles accumulate on the surface, while small-sized plastic particles can easily be infiltrated into the soil layer via the crevices in the soil [121,122]. In addition, Okutan et al. [123] reported that MPs accumulation might be an issue with the actual aquifer instead of its transportation, which required further investigation. ...
... In addition, Okutan et al. [123] reported that MPs accumulation might be an issue with the actual aquifer instead of its transportation, which required further investigation. Then, plants and soil-growing organisms may ingest the plastic particles [109,110,121,124], followed by their decomposition into MPs, which penetrate deeper into the soil [109,[125][126][127] and the food chain through digestion or excretion after ingestion by living organisms (earthworms, fungi and insects) [26,33,128,129]. The soil's MPs can carry pathogenic bacteria and other pollutants (bisphenols, phthalates, short/medium chain chlorinated paraffin, heavy metals, and persistent organic pollutants) [26,130]. ...
Celluloid, the predecessor to plastic, was synthesized in 1869, and due to technological advancements, plastic products appear to be ubiquitous in daily life. The massive production, rampant usage, and inadequate disposal of plastic products have led to severe environmental pollution. Consequently, reducing the employment of plastic has emerged as a pressing concern for governments globally. This review explores microplastics, including their origins, absorption, and harmful effects on the environment and humans. Several methods exist for breaking down plastics, including thermal, mechanical, light, catalytic, and biological processes. Despite these methods, microplastics (MPs, between 1 and 5 mm in size) continue to be produced during degradation. Acknowledging the significant threat that MPs pose to the environment and human health is imperative. This form of pollution is pervasive in the air and food and infiltrates our bodies through ingestion, inhalation, or skin contact. It is essential to assess the potential hazards that MPs can introduce. There is evidence suggesting that MPs may have negative impacts on different areas of human health. These include the respiratory, gastrointestinal, immune, nervous, and reproductive systems, the liver and organs, the skin, and even the placenta and placental barrier. It is encouraging to see that most of the countries have taken steps to regulate plastic particles. These measures aim to reduce plastic usage, which is essential today. At the same time, this review summarizes the degradation mechanism of plastics, their impact on human health, and plastic reduction policies worldwide. It provides valuable information for future research on MPs and regulatory development.
... MPs in soil can also adsorb hydrophobic organic contaminants (HOCs), such as pesticides, which could potentially affect the bioavailability of these compounds and their durability in the soil environment. This could pose unpredictable risks to soil properties, especially when pesticides are transported together with MPs through different environmental systems (Huffer et al., 2019;Rodríguez-Seijo et al., 2019;Yang et al., 2019;Wang et al., 2020a, Wang et al., 2020b. However, compared to natural sources, the importance of MPs as a source of HOCs is a controversial issue due to the abundance of MPs in the environmental system. ...
... In this study, we found that the presence of CPF increased the biogenic transport of LDPE-MPs by the earthworm Lumbricus terrestris. Rodríguez-Seijo et al. (2019) suggested that the transport of LDPE-MPs sprayed with CPF by the earthworm Eisenia fetida did not significantly differ from that of LDPE-MP alone, probably because of the sizes of the MPs (1 mm and 5 mm) which were too big to be ingested and transported by Eisenia fetida. We also found that CPF had no significant effect on the biogenic transport of Bio-MPs even though CPF decreased the ingestion of Bio-MPs by earthworms in treatments with high levels of Bio-MPs. ...
Although microplastics (MPs) are ubiquitous in agricultural soil, little is known about the effects of MPs combined with pesticides on soil organisms and their biogenic transport through the soil profile. In this study, we conducted mesocosm experiments to observe the effects of microplastics (polyethylene (LDPE-MPs) and biodegradable microplastics (Bio-MPs)) and chlorpyrifos (CPF) on earthworm (Lumbricus terrestris) mortality, growth and reproduction, as well as the biogenic transport of these contaminants through earthworm burrows. The results showed that earthworm reproduction was not affected by any treatment, but earthworm weight was reduced by 17.6% and the mortality increased by 62.5% in treatments with 28% Bio-MPs. Treatments with 28% LDPE-MPs and 7% Bio-MPs combined with CPF showed greater toxicity while the treatment with 28% Bio-MPs combined with CPF showed less toxicity on earthworm growth as compared to treatments with only MPs. The treatments with 1250 g ha⁻¹ CPF and 28% Bio-MPs significantly decreased the bioaccumulation of CPF in earthworm bodies (1.1 ± 0.2%, w w⁻¹), compared to the treatment with CPF alone (1.7 ± 0.4%). With CPF addition, more LDPE-MPs (8%) were transported into earthworm burrows and the distribution rate of LDPE-MPs in deeper soil was increased. No effect was observed on the transport of Bio-MPs. More CPF was transported into soil in the treatments with LDPE-MPs and Bio-MPs, 5% and 10% of added CPF, respectively. In addition, a lower level of the CPF metabolite 3,5,6-trichloropyridinol was detected in soil samples from the treatments with MPs additions than without MP additions, indicating that the presence of MPs inhibited CPF degradation. In conclusion, Bio-MPs caused significant toxicity effects on earthworms and the different types of MPs combined with CPF affected earthworms differently, and their transport along the soil profile. Thus, further research is urgently needed to understand the environmental risks of MPs and MP-associated compounds in the soil ecosystem.
... Industrial sources include tire dust, asphalt, various road and building paints, traffic safety facilities, artificial turf, and sports facility flooring (Dehghani et al. 2017;Dris et al. 2016;Dris et al. 2017;Henseler et al. 2019;Magnusson et al. 2016;Rezaei et al. 2019). In agriculture, the use of agricultural machinery, plastic mulch, polytunnels, agricultural waste, sewage sludge containing microplastics, organic fertilizers, controlled-release fertilizers, soil amendments, contaminated irrigation water, and flooding all contribute to large amounts of microplastics (Blasing and Amelung 2018;Carr et al. 2016;He et al. 2018;Rodríguez-Seijo et al. 2019;Weithmann et al. 2018). Microplastics are also present in a wide range of living environments, e.g., in clothing, furniture, or household items, and are released during waste incineration; they are also contributed by landfills and traffic (Dris et al. 2015(Dris et al. , 2016Liebezeit and Liebezeit 2015). ...
Purpose
A number of studies have been conducted on the occurrence, transport, and fate of microplastics in soil environments. The complexity of matrices presents significant challenges in investigating microplastics in soil, highlighting the need for further research and development in this field. In this review, sampling and pretreatment methods available for detecting and further studying microplastics in soil environments are primarily focused with a minor discussion on their various sources and behavior. Finally, based on the current research findings, the directions of future research are proposed as well.
Methods
Based on a comprehensive search of the available database, we provide updated information on the sources and behavior of microplastics in the soil and the analytical techniques available for their study.
Results
Previous studies have predominantly focused on microplastic contamination and its levels in various environments. We propose that the focus of microplastic research needs to be redirected to allow a better understanding of the behavior and impact of soil microplastics. The novel approach involves modeling the behavior of microplastics in the soil and associated environmental impacts and risks and developing standardized testing methods. These tools will provide a comprehensive strategy for creating a healthy and safe environment.
Conclusions
As plastic production increases worldwide, the accumulation of microplastics in the soil also increases, with potentially adverse implications for food security, human health, and climate change. A comprehensive strategy for rational delineation of microplastic behavior in the soil, as presented here, is needed to counteract and control the environmental impact of microplastics.
... While MPs have been the subject of extensive study in marine environments, researchers have only recently begun to focus on MPs in terrestrial ecosystems (He et al. 2013). Terrestrial ecosystems are more receptive to MPs' interactions with biota, which could have consequences for the environment's Gaylor et al. 2013;Lwanga et al. 2017;Rodríguez-Seijo et al. 2019;Huerta et al. 2016;Song et al. 2017) geology and biophysics. Insights into MPs as a stressor of worldwide changes in terrestrial systems, particularly soil and air environments (Fig. 6), are presented here. ...
Microplastics and also nanoplastics are tiny pieces of plastics that have been a rising source of worry due to their ubiquitous occurrence and possible environmental effect. This article dives into the presence, origins, and degrading processes that cause microscopic and nanoplastics in the natural environment, illuminating the complexities of this worldwide issue. Micro- and nanoplastics have become increasingly common in the environment during the last few decades. Microplastics have negative effects on aquatic habitats when they enter water bodies. Atmospheric deposit (microplastics are substances that have been found in the upper atmosphere, primarily originating compared to the breakdown of bigger polymers and the everyday use of car tires), splitting at sea in the marine environment, materials are confronted with constant both chemical and physical stressors, leading to dispersion into smaller pieces along with land-based runoff; storm water drainage from urban areas can transport polymer content, and particle size all impact the breakdown of micro- and nanoplastics. While plastics are known for their durability, they can be degraded through a variety of mechanisms, including mechanical weathering, photodegradation, corrosion by chemicals, biological degradation, and fragmentation. The widespread presence and persistence of micro- and nanoplastics in the surroundings has raised concerns about their potential effects on ecosystems and human health. Particles like these can be consumed by a variety of creatures, ranging from zooplankton to bigger marine animals, resulting in the spread of plastics throughout the food chain. The occurrence and degradation of micro- and nanoplastics is therefore focused in this review.
... CPF has a high octanol-water partition coefficient, log K ow = 4.66, which might explain the high affinity to the polyethylene particles [88]. Different authors considered that PE when compared with other plastics, presents the highest adsorption capacity of MP [89,90]. ...
The constant change in microplastics (MP) due to exposure to environmental conditions leads to physical and chemical changes that enhance their ability to transport other pollutants, increasing the concern about their widespread presence in the environment. This work aimed to simulate the aging process of six MP (polyamide 6, unplasticized polyvinyl chloride, low-density polyethylene, polystyrene, polyethylene-co-vinyl acetate, polypropylene) in freshwater and seawater ecosystems at laboratory scale and evaluate its effects through optical microscope observation, Fourier transform infrared spectroscopy-Attenuated Total Reflectance (FTIR-ATR), Raman spectroscopy, and thermal gravimetric analysis (TGA). Through a combined experimental study of aged MP, the degradation by UV interaction was evidenced by the appearance of new infrared bands in the FTIR spectra assigned to ketones and hydroxyl groups. While Raman analysis and microscope images reveal the appearance of pores, wrinkles, and roughness in the MP surfaces. Variations in the temperature of the maximum weight loss of the MP were observed in the TGA analysis. The adsorption of chlorpyrifos (CPF), a common pesticide widely used in agriculture, by the pristine and aged MP was also studied. The highest affinity for CPF was observed for pristine LDPE and the lowest for PP. The batch adsorption studies revealed an increase in adsorption capacity as a consequence of the aging process for both MP. These results proved that the weathering effects caused changes in the behavior of MP, namely in the interaction with other pollutants.
... After 30 days, no mortality was observed, but the earthworms exposed to plastics lost weight compared to earthworms in plastic-free control soil (Boots et al., 2019). Compost earthworms, Eisenia spp., exhibited oxidative stress responses and immune reactions after PE MPs (250 to 1000 μm) ingestions at concentrations of 0.006, 0.0125, 0.025, 0.5, and 0.1% wt in soil for 28 days, particularly at the three highest concentrations, but no effects on mortality or weight changes were observed (Rodriguez-Seijo et al., 2017;Rodríguez-Seijo et al., 2018). However, no oxidative stress responses were observed when E. fetida was exposed to PE (<300 μm) and PS MPs (<250 μm) at concentrations of up to 10% wt for 14 days . ...
Micro and nanoplastics (MPs and NPs, respectively) in agricultural soil ecosystems represent a pervasive global environmental concern, posing risks to soil biota and crops, hence soil health and food security. This review provides a comprehensive and current summary of the literature on sources and properties of MNPs in agricultural ecosystems, methodology for the isolation and characterization of MNPs recovered from soil, MNP surrogate materials that mimic the size and properties of soil-borne MNPs, and transport of MNPs through the soil matrix. Furthermore, this review elucidates the impacts of agricultural MNPs on crops and soil microorganisms and fauna. A significant source of MPs in soil is plasticulture, involving the use of mulch films and other plastic-based implements to provide several agronomic benefits for specialty crop production, while other sources of MPs include irrigation water and fertilizer. Long-term studies are needed to address current knowledge gaps of formation, soil surface and subsurface transport, and environmental impacts of MNPs, including for MNPs derived from biodegradable mulch films, which, although ultimately undergoing complete mineralization, will reside in soil for several months. Because of the complexity and variability of agricultural soil ecosystems and the difficulty in recovering MNPs from soil, a deeper understanding is needed for the fundamental relationships between MPs, NPs, soil biota and microbiota, including ecotoxicological effects of MNPs on earthworms, soil-dwelling invertebrates, and beneficial soil microorganisms, and soil geochemical attributes. In addition, the geometry, size distribution, fundamental and chemical properties, and concentration of MNPs contained in soils are required to develop surrogate MNP reference materials that can be used across laboratories for conducting fundamental laboratory studies.
... MPs have toxic effects on microorganisms that could be associated with leached chemical additives Wei et al. 2019c). Rodríguez-Seijo et al. (2018a) carried out studies on the impact of exposure to MPs on Eisenia andrei and Eisenia fetida; the analysis of artificial soils was made with virgin LDPE particles (0.25-1 mm). They reported that there was no impact on weight loss or mortality at 28 days (100% survival), nor significant differences in reproduction. ...
Microplastics (MPs) represent a serious problem for the environment and for this reason they have been studied in many articles, especially their presence in aquatic environments and soils. MPs have been found in wastewater and sewage sludge from municipal wastewater treatment plants (WWTPs). Most part of the published works have focused on the detection and elimination of MPs in the water line and several reviews have been published in the last years. In addition, the application of sewage sludge produced from WWTPs for agricultural use is known to be a primary source of MPs in soils. However, in the scientific literature less attention has been paid to the sludge and little is known about MPs fate when it is applied in agriculture. This work aims to give a global revision on the most used techniques to identify and detect MPs in sludges, their characteristics and incidence, their effect on sludge treatments and their impact on the environment. As far as we know, there are no standardized protocols for MPs extraction from soil and the possible repercussions on the cultivation of plants are not known. This review evidences that more studies are necessary to stablished standardized protocols and decipher the main mechanisms and the effects of MPs from sewage sludge in the environment.
... ☆ This paper has been recommended for acceptance by Cheng-Di Dong. This is mainly borne out of the fact that conventional wastewater treatment systems are not designed for microplastic removal; thus, these particles find their way through the drains, bypass the treatment plants and get introduced into different receiving waters and perpetuate indefinitely due to their non-biodegradable nature (Tanaka and Takada, 2016;Rodríguez-Seijo et al., 2019). Although, microplastics including microbeads have been found in significant quantities in all parts of our planet including environmentally protected and remote areas, the marine environments have since been identified as the greatest area of impact due to their significant contamination of sea surfaces and water columns, as well as their deposition in the long-term accumulation matrix (Guerranti et al., 2019;Huang et al., 2022b). ...
Since the advent of microplastics, it has become a vital component, directly or indirectly, in our daily lives. With advancements in their use, microplastics have become an integral part of personal care, cosmetics, and cleaning products (PCCPs)and emerged as a domestic source of environmental pollution. Over the years, researchers have ascertained the harmful effects of microplastics on the environment. In this context, the assessment and monitoring of microplastics in PCCPs require considerable attention. In addition, it raises concern regarding the need to develop innovative, sustainable, and environmentally safe technologies to combat microplastic pollution. Therefore, this review is an endeavor to uncover the fate, route and degradation mechanism of cosmetic microplastics. In addition, the major technological advancement in cosmetic microplastic removal and the steps directed toward mitigating cosmetic microplastic pollution are also discussed.
... It can also cause soil animals to produce false satiety, thereby reducing the carbon biomass intake, further leading to energy consumption, and ultimately resulting in reduced growth and even death [122]. In addition to particle toxicity, the impact of microplastics on soil organisms also includes the toxic effects of the various environmental pollutants attached to their surface, as discussed above [123,124]. At present, the research on the impact of microplastic distribution on soil microbial ecology mainly focuses on the assessment of changes in soil enzyme activities [45]. ...
As plastic products are widely used in all walks of life, plastic waste is also accumulating in the environment. Today, microplastic pollution in the soil environment has become an environmental issue of global concern. Compared with the water environment, the research on microplastics in the soil environment is relatively lacking. Based on the above situation, this paper systematically reviews the distribution characteristics, influencing factors, and environmental and ecological risks of microplastics in the soil environment. The abundance, distribution characteristics, and impacts of microplastics in soils globally in recent years are reviewed in detail. Our review suggests that most scholars only focus on the surface soil, and the determination of the accumulation of microplastics in the soil as a whole is still lacking, and there is still no uniform standard for sampling techniques, extraction methods, analytical procedures, and even expression units for soil microplastics. The distribution of microplastics in soil is affected by human factors, natural factors, and the physical and chemical properties of the plastics themselves. We also focused on the analysis of the environmental risks arising from the accumulation of microplastics in soil interacting with metals and organic pollutants, and found that large research gaps exist in the interaction between microplastics and pollutants in the soil and the mechanism of compound pollution. The impact and ecological risks of microplastics on animals, microorganisms, and plants in the soil are explained. Moreover, key suggestions for future research are presented based on the current research status, and we call for more efforts focusing on the occurrence and fate of microplastics in the soil environment.
... Recent studies have demonstrated that microplastics with varied chemical compositions can cause skin damage, tissue lacerations, immunity disruption, and neurotoxicity in terrestrial organisms such as ciliates, collembolans, and earthworms [55,56]. Some studies have even shown that E. fetida ingestion of MPs (HDPE, PP, and LDPE) smaller than 300 μm [57,58] leads to inflammatory processes between the gut epithelium and the chloragogeneous tissue, sometimes with the development of fibrosis and congestion [59]. Our results showed that the control treatment reached the highest value at the end of the exposure bioassay. ...
Nowadays, plastic materials are extensively used in the agri-food sector for multiple purposes. The end-of-life management of these plastics is an environmental challenge because frequent incomplete recoveries after the crop seasons lead to the accumulation of plastics debris in agricultural waste, which is now recognized as an emerging environmental issue of global concern. However, the effects of plastic debris in agricultural waste undergoing biotreatment have been poorly studied. This study assesses the effects of agricultural plastic waste (APW) (LDPE + LLDPE and EPS) (1.25% f.w.) on the vermicomposting process (45 days) in terms of earthworm health by measuring biomarker responses and the enzymatic activity and quality/stabilization of the vermicompost obtained. The results showed that exposure to all the plastic materials tested had negative morphological effects on earthworm survival and body biomass. In the vermicomposting process, the changes detected in the enzymatic activity of the vermicompost and the biofilm seemed to affect the degradation rate of earthworms and the microbiome of the substrate, as demonstrated by the low organic matter mineralization in the vermicompost exposed to plastic. Although no significant changes were recorded in several biomarkers, signs of oxidative stress were evidenced throughout the glutathione S-transferase and carboxylesterase activity, mainly involving balanced oxidative stress and xenobiotic resistance systems.
... The wear of tires, laundering, and the decomposition of plastic products exposed to the environment have produced granular, fibrous, and flake-like microplastics, respectively, at the millimeter and micrometer scales (Browne et al., 2011;Siegfried et al., 2017;Song et al., 2017;Hodgson et al., 2018;Zhang and Liu, 2018). The concentration of fibrous microplastics in laundry wastewater is more than 100 microplastics per liter (Rodríguez-Seijo et al., 2019). Recycled plastics are usually ground into granules or powders as secondary raw materials, resulting in microscale or even nanoscale microplastics . ...
Despite the serious risk of microplastic pollution in the roots and leaves of crops, the phytotoxicity of microplastics (introduced via different exposure routes) in leafy vegetables remain insufficiently understood. Here, the effects of the root and foliar exposure of polymethyl methacrylate microplastic (PMMAMPs) on phytotoxicity, As accumulation, and subcellular distribution were investigated in rapeseed (Brassica campestris L). The relative chlorophyll content under PMMAMPs treatment decreased with time, and the 0.05 g L⁻¹ root exposure decreased it significantly (by 9.97–20.48%, P < 0.05). In addition, superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and ascorbate peroxidase (APX) activities in rapeseed were more sensitive to PMMAMPs introduced through root exposure than through foliar exposure. There was dose-dependent ultrastructural damage, and root exposure had a greater impact than foliar exposure on root tip cells and chloroplasts. PMMAMPs entered the shoots and roots of rapeseed through root exposure. Under foliar exposure, PMMAMPs promoted As accumulation in rapeseed by up to 75.6% in shoots and 68.2% in roots compared to that under control (CK). As content in cell wall under PMMAMP treatments was 3.6–5.3 times higher than that of CK, as indicated by subcellular component results. In general, root exposure to PMMAMPs resulted in a stronger physiological impact and foliar exposure led to increased As accumulation in rapeseed.
... The decrease in AChE activity inhibition and changes in ETS activity by microplastics co-exposure suggest that the bioavailability of chlorpyrifos to woodlice was decreased by both types of microplastics. As chlorpyrifos is a specific inhibitor of AChE (Sanchez-Hernandez et al., 2014;Muangphra et al., 2016;Rodríguez-Seijo et al., 2018), a decrease of its inhibition suggests a lower available concentration of the inhibitor. The same phenomenon was observed for the ETS activity in woodlice. ...
Synthetic fibers released from sewage sludge and tire particles released from traffic are among the most common types of microplastics in soil. In soil, microplastics may interact with chemicals, such as plant protection products used in agriculture. Most studies on the interactions of microplastics and chemicals focused on aquatic environments and only few addressed soil arthropods. To increase the understanding of the combined effects of microplastics and chemicals on soil arthropods, we studied the effects of polyester fibers and tire particles on the toxicity of the insecticide chlorpyrifos. Springtails (Folsomia candida) and woodlice (Porcellio scaber) were exposed in Lufa 2.2 soil to a range of chlorpyrifos concentrations (0.0088-0.8 and 0.2-3.9 mg kg − 1 dry soil, respectively) without or with 0.05 % w/w ("low") or 0.5 % w/w ("high") of microplastics. Tire particles reduced the lethality of chlorpyrifos to springtails (LC50 = 0.13-0.14 mg kg − 1 dry soil) and isopods (LC50 = 1.6 mg kg − 1 dry soil) by a factor of 2-> 2.5 and the chlorpyrifos-induced inhibition of acetylcholinesterase (AChE) activity and changes in electron transfer system (ETS) activity in P. scaber by a factor of 2-4. Polyester fibers reduced the chlorpyrifos-induced inhibition of AChE activity by a factor of 2 and increased (ETS) activity in P. scaber by a factor of >3. The fibers did not affect the toxicity of chlorpyrifos to the survival of P. scaber or the survival and reproduction of F. candida. These results indicate that the bioavailability of chlorpyrifos may be decreased by microplastics, especially by tire particles. This study shows the importance of applying a mixture toxicity approach for understanding the threats of microplastics to soil, but also suggests that the organism and the endpoints chosen are crucial for the interpretation of the effects of combined exposures to microplastics and chemicals.
... It is now well established that conventional microplastics composed of polyethylene or polypropylene can exert a wide range of negative effects on the soil leading to a decline in soil quality (Qi et al., 2020a;Zang et al., 2020;Zhou et al., 2022). For example, these microplastics can interfere with earthworm growth and reproduction, alter microbial activity and function and change the physical properties of the soil Rodríguez-Seijo et al., 2019;Lin et al., 2020;Azeem et al., 2021;Wang et al., 2021;Wang et al., 2022a). In contrast, however, the impact of bio-based biodegradable macro-and micro-plastics on soil functioning remains largely unknown. ...
Microplastic contamination poses a significant threat to agroecosystem functioning, provoking a move away from the use of conventional oil-based plastics in agriculture, to biodegradable alternatives that may be degraded over a shorter timescale. The impact of these bioplastics on plant and soil health, however, has received relatively little attention. Here, we investigated the effect of soil loading (0.01%, 0.1%, 1% and 10%) of biobased microplastic poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) on soil and plant (Zea mays L.) health and function. We showed that PHBV caused a dose-dependent reduction in plant growth and foliar nitrogen (N) content while untargeted metabolite analysis revealed significant shifts in foliar metabolic function. These results were also reflected in soil, where PHBV led to reduced plant availability of both ammonium and nitrate. Soil ¹⁴C-isotope tracing and 16 S metabarcoding revealed that PHBV supressed microbial activity, reduced bacterial diversity and shifted microbial community structure, inducing a major shift in soil metabolic pathways, and thus functioning. Overall, our data suggests that the bioplastic PHBV is not environmentally benign and that contamination levels as low as 0.01% (0.01 mg kg⁻¹) can induce significant short-term changes in both plant and soil microbial functioning, with potential implications for long term agroecosystem health.
... Microplastics can concentrate harmful pollutants, particularly hydrophobic organic compounds, by surface adsorption and thus could act as a carrier creating hotspots of contaminants in soil environments (Rochman et al., 2014;Rodríguez-Seijo et al., 2019;Teuten et al., 2007;Zhang and Liu, 2018). Similarly, some studies show that persistent organic pollutants (such as the insecticide DDT) and pharmaceuticals, including a range of antibiotics, are also bound to MPs Torres et al., 2021;Velzeboer et al., 2014;Wang et al., 2020e). ...
The increasing production and use of conventional plastics, including in agricultural systems, has generated over 6500 million tonnes of plastic waste over the last 70 years. Over two–third of this waste had been deposited in landfills and natural environments including soils. However, the existence, persistence and impacts of plastics on soil properties and soil ecosystem services have received little attention compared to aquatic environments. Some agricultural soils accumulate plastics in large concentration from the application of sewage sludge and composts, wastewater for irrigation and the use of plastic films. The review provides an overview of the procedures used for the separation and characterization of plastics in soils. Based on the limited data, we have found that contaminated soils accumulate substantial amounts of plastics worldwide with a mean of 6153 particles kg− 1 soil (median 1083 = particles kg− 1). The presence of plastics can cause a series of toxic effects to soil health, fauna and plants through complex interactions. The results from existing literature have been reviewed and summarized. Once plastics enter the soil, they can simultaneously go through photo–, thermal– and bio– degradation. However, the degradation of conventional plastics is very slow, with half–lives ranging from a few hundreds to thousands of years in soil environments. Based on our review findings we recommend a number of priority research areas.
... Additionally, hydrophobic persistent organic pollutants in the environment, such as polycyclic aromatic hydrocarbons (PAHs), are easily adsorbed on PS particles (C. M. Rodriguez-Seijo et al., 2019). Pollution caused by PAHs poses environmental problems worldwide. ...
Owing to their wide distribution, easy production, and resistance to degradation, microplastics (MPs) represent a globally emerging group of pollutants of concern. Furthermore, their decomposition can result in the generation of nanoplastics (NPs), which cause further environmental issues. Currently, the impact of the combination of these plastics with other organic pollutants on crop growth remains poorly investigated. In this study, a hydroponic experiment was conducted for seven days to evaluate the effects of 50 nm, 50 mg/L polystyrene (PS), and 1 mg/L phenanthrene (Phe) on the growth of rice plants. The results revealed that both Phe and PS inhibited growth and improved the antioxidant potential of rice. Relative to Phe alone, exposure to a combination of PS and Phe reduced Phe accumulation in the roots and shoots by 67.73% and 36.84%, respectively, and decreased the pressure on the antioxidant system. Exposure to Phe alone destroyed the photosynthetic system of rice plant leaves, whereas a combination of PS and Phe alleviated this damage. Gene Ontology (GO) analysis of the rice transcriptomes revealed that detoxification genes and phenylalanine metabolism were suppressed under exposure to Phe, which consequently diminished the antioxidant capacity and polysaccharide synthesis in rice plants. Kyoto Encyclopaedia of Genes and Genomes (KEGG) transcriptome analysis revealed that the combined presence of both PS and Phe improved photosynthesis and energy metabolism and alleviated the toxic effects of Phe by altering the carbon fixation pathway and hormone signal transduction in rice plants. The combination of PS and Phe also prevented Phe-associated damage to rice growth. These findings improve our understanding of the effects of MP/NPs and polycyclic aromatic hydrocarbons on crops.
... Third, microplastics may serve as a vector of pathogenic bacteria (Martínez-Campos et al., 2022) and fungi as well as antibiotic-resistant bacteria (Parthasarathy et al., 2019). Furthermore, microplastics can be carriers of pesticides (Rodríguez-Seijo et al., 2018). Finally, microplastics represent fossil carbon, which is independent of photosynthesis and net primary production (Rillig and Lehmann, 2020). ...
Agricultural land soils have become a source and sink for microplastics. Due to the low recycling rate, long durability, and small size, microplastics pose a potential risk to soil fauna, which are critical for maintaining healthy soil. However, whether and how would microplastics affect soil biodiversity and ecological functioning is not well-understood. Soil nematodes are valuable indicators of the soil food web. In the present study, the abundance, diversity, community composition, maturity indices, soil food web indices, and metabolic footprints of soil nematodes in bulk soils of maize were utilized to indicate the potential impacts of polypropylene (PP) microplastic pollution on soil fauna using a soil-incubation experiment in a climate-controlled chamber with four concentration levels of microplastic pellets (0%, 0.5%, 1%, and 2%, w/w) added to loess soil collected from the Loess Plateau in China. Soil sampling was conducted at the fully ripe stage of maize. Twenty-nine genera of nematodes, including thirteen genera of plant-feeding nematodes, seven genera of bacterial-feeding nematodes, five genera of fungal-feeding nematodes, and four genera of omnivorous nematodes were recovered from soil samples. Microplastic concentration negatively affected the abundance, diversity (including genus richness, Margalef’s richness, Shannon–Wiener index, and Simpson’s dominance index), sigma maturity index (∑MI), structural index, and metabolic footprints. The abundances of plant parasites, bacterivores, fungivores, and omnivores in 2% soils were reduced by 90.16%, 76.06%, 82.35%, and 100%, respectively, in comparison with those of control. The major drivers of soil nematode communities in bulk soils of maize at a depth range of 0–20 cm were the soil pH, soil organic carbon content, C/N, and TP content. In conclusion, the addition of 200 μm-sized PP microplastic pellets negatively affected the soil nematode community and associated ecological functioning under greenhouse conditions.
... For instance, polyester microfibers significantly affect soil physical properties (bulk density and water holding capacity) as compared to PE fragments, polyamide beads, and polyacrylic fibers (de Souza Machado et al. 2018b). A detailed account of the negative effects of microplastics on soil properties is given in Table 3. Microplastics contain several toxic additives (viz., bisphenol A, phthalates, alkylphenol), which may further leach and render negative effects on soil organisms (vertebrates and invertebrates) by disrupting their hormonal system (Teuten et al. 2009;Hodson et al. 2017;Rodríguez-Seijo et al. 2019;Groh et al. 2019). Microplastics may act as small sinks and further sources of adsorbed contaminants viz., metal/ metalloids, antibiotics and pesticides Cao et al. 2021). ...
In the past few decades, pollution from microplastics has emerged as an important issue on a global scale. These plastic particles are mainly the result of anthropogenic activities. Urban sprawl, industrialization, indiscriminate use and poor waste management of plastic products are the main factors responsible for the accumulation of microplastics in different ecosystems of the environment. The presence of microplastics in the soil matrix is considered an emerging threat to agroecosystems. Since most of the studies on microplastics have been done in the aquatic environment. The understanding of the ecotoxicological effects of these contaminants in terrestrial ecosystems is still limited, especially in agroecosystems. The negative effects of microplastics on the physical, chemical and biological properties of soil are now revealing. But the effects of microplastics on plant growth and yield are largely unexplored. Microplastic contamination in the soil can alter the functioning of plants by affecting the microbial community of the rhizosphere and disturbing the homeostasis of the agroecosystem. Furthermore, it may transfer into the plant system through nutrient and water absorption channels and affect plant physiology. The pervasive nature of microplastics in the soil is considered a barrier to sustainable agriculture and ecosystem functioning. The present review gives an overview of the sources, dissipation and effects of microplastics with reference to the soil–plant system, highlights the research gaps, and deciphers the possible future threats to agroecosystems.
Graphical abstract
... However, this observation was not made after exposures to higher concentrations of 1 mg/kg polystyrene, which fits more with the results of the present study. Other studies confirm this low acute toxicity with no observed mortality after even higher concentrations of PS or exposures to other microplastics such as polyethylene (Rodríguez-Seijo et al., 2018a;2018b;Wang et al., 2019). A study by (Sheng et al., 2021) investigated effects of car tire abrasions on the earthworm E. fetida after exposures of 14 and 28 d in artificial soil and only observed changes on enzymatic biomarkers but no mortality. ...
Microplastics are small plastic fragments that are widely distributed in marine and terrestrial environments. While the soil ecosystem represents a large reservoir for plastic, research so far has focused mainly on the impact on aquatic ecosystems and there is a lack of information on the potentially adverse effects of microplastics on soil biota. Earthworms are key organisms of the soil ecosystem and are due to their crucial role in soil quality and fertility a suitable and popular model organism in soil ecotoxicology.
Therefore, the aim of this study was to gain insight into the effects of environmentally relevant concentrations of microplastics on the earthworm Eisenia andrei on multiple levels of biological organization after different exposure periods. Earthworms were exposed to two types of microplastics: (1) polystyrene-HBCD and (2) car tire abrasion in natural soil for 2, 7, 14 and 28 d. Acute and chronic toxicity and all subcellular investigations were conducted for all exposure times, avoidance behavior assessed after 48 h and reproduction after 28 d. Subcellular endpoints included enzymatic biomarker responses, namely, carboxylesterase, glutathione peroxidase, acetylcholinesterase, glutathione reductase, glutathione S-transferase and catalase activities, as well as fluorescence-based measurements of oxidative stress-related markers and multixenobiotic resistance activity. Multiple biomarkers showed significant changes in activity, but a recovery of most enzymatic activities could be observed after 28 d. Overall, only minor effects could be observed on a subcellular level, showing that in this exposure scenario with environmentally relevant concentrations based on German pollution levels the threat to soil biota is minimal. However, in areas with higher concentrations of microplastics in the environment, these results can be interpreted as an early warning signal for more adverse effects. In conclusion, these findings provide new insights regarding the ecotoxicological effects of environmentally relevant concentrations of microplastics on soil organisms.
Landfill leachate contains antibiotic resistance genes (ARGs) and microplastics (MPs), making it an important reservoir. However, little research has been conducted on how ARGs are enriched on MPs and how the presence of MPs affects pathogens and ARGs in leachates and soil. MPs possess the capacity to establish unique bacterial populations and assimilate contaminants from their immediate surroundings, generating a potential environment conducive to the growth of disease-causing microorganisms and antibiotic resistance genes (ARGs), thereby exerting selection pressure. Through a comprehensive analysis of scientific literature, we have carried out a practical assessment of this topic. The gathering of pollutants and the formation of dense bacterial communities on microplastics create advantageous circumstances for an increased frequency of ARG transfer and evolution. Additional investigations are necessary to acquire a more profound comprehension of how pathogens and ARGs are enriched, transported, and transferred on microplastics. This research is essential for evaluating the health risks associated with human exposure to these pollutants.
Soil and water are two important basic ecosystems for the survival of different organisms. The excessive microplastic pollutants in soil have been directly discharged into the terrestrial ecosystems. Microplastic pollutants (MPs) constitute a ubiquitous global menace due to their durability, flexibility, and tough nature. MPs posed threat to the sustainability of the ecosystem due to their small size and easy transportation via ecological series resulting in the accumulation of MPs in aquatic and terrestrial ecosystems. After being emitted into the terrestrial ecosystem, the MPs might be aged by oxidative degeneration (photo/thermal), reprecipitation (bioturbation), and hetero-accumulation. The mechanism of adsorption, degradation, and breakdown of MPs into unaffected plastic debris is accomplished by using several biological, physical, and chemical strategies. This review presents the importance of ecosystems, occurrence and sources of MPs, its toxicity, and the alteration in the ecology of the ecosystems. The inhibitory impact of MPs on the ecosystems also documents to unveil the ecological hazards of MPs. Further research is required to study the immobilization and recovery efficiency of MPs on a larger scale.
The pollution caused by micro- (MP) and nanoplastics (NP) in the planet’s ecosystems has gained significant interest in recent years due to their environmental impact and effects on the health of living organisms. Given this, it is necessary to conduct a comprehensive analysis of the actions required to mitigate their impacts. This paper analyzes existing legislation across different countries and regions, including Europe, North America, China, Russia, India, Brazil, Mexico, and the global initiatives undertaken by the United Nations. Furthermore, it highlights the need for additional measures to mitigate the impact of MP/NP in future years, such as the development of technologies for the separation or degradation of these particles in water intended for human consumption and in wastewater treatment plant effluents, studying plastic particulate material in the air considering meteorological parameters, MP/NP detection protocols in human fluid samples, creating truly biodegradable polymers for use as bioplastics, and establishing institutions responsible for the management of plastic waste. The study also shows the current state of abundance (characterization and quantification) of MP/NP in different environmental matrices based on reports from recent years, and identifies key research opportunities and actions required to evaluate the risks and toxicity associated with MP/NP. Socio-economic aspects are considered, including the impact of MP/NP on different regions, by associating economic and human wellness parameters to plastic waste generation by using available data from 148 countries. As result of this analysis, both the most populated and developed countries contribute to MP/NP generation, however, they have different capacities to address this problem due to social circumstances. The solution to this problem requires efforts from authorities, industry, the scientific community, and the active participation of the population, then, resolving social, political, and economic issues between countries and regions of the world is necessary.
As MPs are released into the soil, various equilibrium statuses are expected. MPs could play roles as a "source," a "cleaner," or a "sink" of HOCs. Three types of MPs (LDPE, PLA, and PS) were selected to study their effect on polychlorinated biphenyl (PCBs) relative bioavailability (RBA) measured by a mouse model. As a "source" of HOCs, exposure to MP-sorbed PCBs resulted in their accumulation in adipose tissue with PCB RBA as 101 ± 6.73% for LDPE, 76.2 ± 19.2% for PLA, and 9.22 ± 2.02% for PS. The addition of 10% MPs in PCB-contaminated soil led to a significant (p < 0.05) reduction in PCB RBA (52.2 ± 16.7%, 49.3 ± 4.85%, and 47.1 ± 5.99% for LDPE, PLA, and PS) compared to control (75.0 ± 4.26%), implying MPs acted as "cleaner" by adsorbing PCBs from the digestive system and reducing PCB accumulation. MPs acted as a "sink" for PCBs in contaminated soil after aging, but the sink effect varied among MP types with more pronounced effect for LDPE than PLA and PS. Therefore, the role played by MPs in bioavailability of HOCs closely depended on the MP types as well as the equilibrium status among MPs, soil, and HOCs.
Polyethylene microplastics have been detected in farmland soil, irrigation water, and soil organisms in agroecosystems, while plastic mulching is suggested as a crucial source of microplastic pollution in the agroecosystem. Plastic mulch can be broken down from plastic mulch debris to microplastics through environmental aging and degradation process in farmlands, and the colonization of polyethylene-degrading microorganisms on polyethylene microplastics can eventually enzymatically depolymerize the polyethylene molecular chains with CO2 release through the tricarboxylic acid cycle. The selective colonization of microplastics by soil microorganisms can cause changes in soil microbial community composition, and it can consequently elicit changes in enzyme activities and nutrient element content in the soil. The biological uptake of polyethylene microplastics and the associated disturbance of energy investment are the main mechanisms impacting soil-dwelling animal development and behavior. As polyethylene microplastics are highly hydrophobic, their presence among soil particles can contribute to soil water repellency and influence soil water availability. Polyethylene microplastics have been shown to cause impacts on crop plant growth, as manifested by the effects of polyethylene microplastics on soil properties and soil biota in the agroecosystems. This review reveals the degradation process, biological impacts, and associated mechanisms of polyethylene microplastics in agroecosystems and could be a critical reference for their risk assessment and management.
Microplastics (size 1 μm–5 mm) and nanoplastics (size 1–1000 nm), commonly referred to as micro(nano)plastics (MNPs), are ubiquitously present in aquatic and terrestrial environments, where they imminently interact with persistent organic pollutants, such as pesticides, inducing adverse toxicological effects in exposed organisms. MNPs interact with pesticides through adsorption and desorption processes, which require additional consideration due to the prospective role this nexus plays in changing the environmental transportation, fate, bioavailability, and ecotoxicity of both plastic particles and pesticides. Therefore, this review summarizes studies on the adsorption of pesticides on MNPs and factors affecting that adsorption process, including MNP properties (particle size, surface area, shape, dose), characteristics of pesticides (ionic properties, hydrophobicity), and environmental factors (temperature, pH, ionic strength). Furthermore, the bioaccumulation and associated combined toxicological impacts of pesticides and MNPs in freshwater, marine water, and terrestrial organisms are highlighted. Reviewed studies revealed that MNPs and pesticides undergo bioaccumulation in aquatic and terrestrial organisms and can cause multifaceted impacts, including growth and reproduction impairments, oxidative stress, altered genetic and enzymatic responses, metabolism abnormalities, multigenerational effects, histopathological modifications, neurotoxicity, and hepatotoxicity, among others. Last but not least, research gaps and future perspectives for pesticide and MNP interactions and their interconnected ecological implications are offered.
The production and disposal of plastics have become significant concerns for the sustainability of the planet. During the past 75 years, around 80% of plastic waste has either ended up in landfills or been released into the environment. Plastic debris released into the environment breaks down into smaller particles through fragmentation, weathering, and other disintegration processes, generating microplastics (plastic particles ≤ 5 mm in size). Although marine and aquatic ecosystems have been the primary focus of microplastic pollution research, a growing body of evidence suggests that terrestrial ecosystems are equally at risk. Microplastic contamination has been reported in various terrestrial environments from several sources such as plastics mulch, pharmaceuticals and cosmetics, tire abrasions (tire wear particles), textiles industries (microfibers), sewage sludge, and plastic dumping. Recent studies suggest that the soil has become a significant sink for pollutants released into terrestrial ecosystems and is often contaminated with a mixture of organic and inorganic pollutants. This has gradually caused adverse impacts on soil health and fertility by affecting soil pH, porosity, water-holding capacity, and soil microbial enzymatic activities. Microplastics can interact with the co-existing pollutants of the environments by adsorbing the contaminants onto their surfaces through various intermolecular forces, including electrostatic, hydrophobic, non-covalent, partition effects, van der Waals forces, and microporous filling mechanisms. This subsequently delays the degradation process of existing contaminants, thereby affecting the soil and various ecological activities of the ecosystem. Thus, the present article aims to elucidate the deleterious impact of microplastics and their interactions with other pollutants in the terrestrial ecosystem. This review also addresses the impact of microplastics in disrupting the soil sustainability of the planet.
Microplastics (MP) and nanoplastics (NP) contamination of the terrestrial environment is a growing concern worldwide and is thought to impact soil biota, particularly the micro and mesofauna community, by various processes that may contribute to global change in terrestrial systems. Soils act as a long-term sink for MP, accumulating these contaminants and increasing their adverse impacts on soil ecosystems. Consequently, the whole terrestrial ecosystem is impacted by microplastic pollution, which also threatens human health by their potential transfer to the soil food web. In general, the ingestion of MP in different concentrations by soil micro and mesofauna can adversely affect their development and reproduction, impacting terrestrial ecosystems. MP in soil moves horizontally and vertically because of the movement of soil organisms and the disturbance caused by plants. However, the effects of MP on terrestrial micro-and mesofauna are largely overlooked. Here, we give the most recent information on the forgotten impacts of MP contamination of soil on microfauna and mesofauna communities (protists, tardigrades, soil rotifers, nematodes, collembola and mites). More than 50 studies focused on the impact of MP on these organisms between 1990 and 2022 have been reviewed. In general, plastic pollution does not directly affect the survival of organisms, except under co-contaminated plastics that can increase adverse effects (e.g. tire-tread particles on springtails). Besides, they can have adverse effects at oxidative stress and reduced reproduction (protists, nematodes, potworms, springtails or mites). It was observed that micro and mesofauna could act as passive plastic transporters, as shown for springtails or mites. Finally, this review discusses how soil micro- and mesofauna play a key role in facilitating the (bio-)degradation and movement of MP and NP through soil systems and, therefore, the potential transfer to soil depths. More research should be focused on plastic mixtures, community level and long-term experiments.
Spatial and Temporal Variations of Air Temperature on Drought Hazard in Sri
Lanka: with Special Reference to Hambantota District
Microplastic pollution is an increasing threat to the terrestrial ecosystem. Microplastic use increases day by day in industries for the manufacturing of several products. Wastewater of the industries are released in the water system, and farmers utilize this water for irrigation purposes. Due to its small size, microplastics interact with the soil macro and micro-fauna and cause various toxic disorders. In the agriculture field, a large amount of plastic mulch used for farming also acts as another source of microplastics. Different types of microplastics were extracted and detected from the soil by using different types of techniques. Our study mainly focuses on the sources, extraction and detection of microplastics from agricultural soil.The effect of microplastic on earthworms and its degradation by gut bacteria of earthworms has been studied in this chapter.
Contamination of soils in agroecosystems with microplastics (MPs) is of increasing concern. The contamination of the environment/farmland soils with MPs (1 µm to 5 mm sized particles) and nanoplastics (NPs; <1 µm sized particles) is causing numerous effects on ecological soil functions and human health. MPs enter the soil via several sources, either from intentional plastic use (e.g., plastic mulch, plastic greenhouses, plastic‐coated products) or indirectly from the input of sewage sludge, compost, or irrigation water that is contaminated with plastic. Once in the soil, plastic debris can have various impacts such as changes in soil functions and physicochemical properties and it affects soil organisms due to its toxic behavior. This review paper describes the different effects of plastic waste to understand the consequences for agricultural productivity. Furthermore, we identify knowledge gaps and highlight the required approaches, indicating future research directions on sources, transport, and fate of MPs in soils to improve our understanding of various unspecified abiotic and biotic impacts of MP pollution in agroecosystems. Microplastic impacts on agroecosystem soil.
Microplastics are ubiquitous and continue to migrate and transform. The potential hazards of microplastics to the environment and organisms, including humans, have attracted great concerns worldwide. Microplastics enter the soil ecosystems via different sources such as mulch degradation, plastic landfills, organic fertilizer, transport, etc., and occur widely with a significant spatial difference. Microplastics interact with the physicochemical properties of soil and negatively impact fauna, plant, and environmental health. More than 400 bacterial species have been identified as potential plastic degraders, but little is known about these organisms' structure, dynamics, and functional abilities in plastic-contaminated environments. Here, in this review, we have highlighted the distribution and transportation of microplastics in terrestrial environments. We then discussed the synergistic efficacy of soil and earthworm-gut microbiomes towards the effective degradation of microplastics and highlighted the role of metagenomic approaches in assessing the diverse plastisphere.
In the current scenario, plastic pollution has become one of the serious environmental hazard problems due to its improper handling and insufficiency in degradation. Nanoplastics (NPs) are formed when plastic fragments are subjected to ultraviolet radiation, natural weathering, and biodegradation. This review paper focuses on the source of origin, bioaccumulation, potential nanoplastics toxicity impact towards environment and human system and management strategies towards plastic pollution. Moreover, this study demonstrates that nanoplastics interfere with metabolic pathways and cause organ dysfunction. A wide range of studies have documented the alteration of organism physiology and behavior, caused by NPs exposure. A major source of NPs exposure is via ingestion because these plastics are found in foods or food packaging, however, they can also enter the human body via inhalation but in a less well-defined form. In recent literature, the studies demonstrate the mechanisms for NP uptake, affecting factors that have been discussed followed by cytotoxic mechanisms of NPs. However, study on challenges regarding NPs toxicity for the risk assessment of human health is limited. It is important to perform and focus more on the possible impacts of NPs on human health to identify the key challenges and explore the potential impacts of their environmental accumulation and its toxicity impacts.
Microplastics (MPs) and Nanoplastics (NPs) are ubiquitous pollutants which have been widely recognized as a threat to soil ecosystems. Soil fauna includes many different organisms such as earthworms, collembola, mites and nematodes and its activity is essential for maintaining a correct level of soil productivity and health. Once MNPs are ingested by terrestrial animals, they can cause several negative physiological effects including gut dysbiosis. MNPs driven changes in gut microbiota are often overlooked but could result in significant ecosystemic risks. Our current opinion is that gut dysbiosis can have repercussions on soil microbial community composition, functioning and on ecosystemic services. Furthermore, the current number of studies on the effects of MNPs on soil fauna gut microbiome is still very limited. Future research should thus further investigate the effects of MNPs on gut microbiota. Moreover, the relationship between terrestrial fauna intestinal microbiome and soil functionality needs to be considered and more in-depth researched.
The accumulation of plastics in the environment is a major problem in the Anthropocene. As most plastic is produced, used and discarded on land, ∼4–23 times more plastics are deposited in soils than in the oceans. However, there is far too little knowledge on the ecological consequences of plastic pollution, especially for soil ecosystems. Microplastics (<5 mm), whether derived from larger plastic pieces through physical, chemical and biological degradation or produced as primary particles, is of considerable interest, as they can be ingested by organisms at the basis of the trophic net and transferred to higher trophic levels. Nonetheless, although the assessment of microplastic effects on soil invertebrates is of undeniable relevance, most studies have focussed on nano- and microplastics in aquatic environments. This review examines the current state of knowledge regarding the effects of microplastics on soil invertebrates. As part of the soil biota, these organisms are of utmost importance for carbon cycling, respiration and biodiversity. Based on strict quality criteria, the data of 45 papers reporting ecotoxicological effects on soil invertebrates were analyzed, considering various test organisms and types of microplastic (in terms of polymer, shape and size). However, although different impacts were demonstrated, a deduction of general effect tendencies of microplastics in soils was difficult due to the scarcity of data and the use of diverse methodological setups. Moreover, almost all experiments were based on short-term single-species testing involving only a small number of species and single microplastic types. The review concludes with a discussion of the remaining knowledge gap and the needs for a standardized approach allowing an ecologically relevant risk assessment of the impacts of microplastic on invertebrates in terrestrial ecosystems.
Mulched drip irrigation is the primary irrigation technology for cotton (Gossypium hirsutum L.) cultivation in arid and semi-arid regions. In recent years, the increasing amount of residual plastic film (RPF) in mulched cotton fields has posed a more significant threat to soil quality and the sustainability of agricultural production. However, the relationship between different soil RPF amounts and cotton growth, yield, and carbon balance in cotton fields is unclear. In this study, six RPF amounts, namely RPF0 (0 kg ha–1), RPF5 (146.18 kg ha–1), RPF10 (228.03 kg ha–1), RPF15 (309.88 kg ha–1), RPF20 (391.73 kg ha–1), and RPF25 (473.58 kg ha–1), were set in a two-year (2020–2021) field experiment to investigate their effects on cotton growth, yield, field CO2 emissions, and carbon sequestration. Results showed that cotton growth indicators (Plant height, stem diameter, leaf area index, biomass of each organ) at different growth stages and yield indicators (Single boll weight, per plant bolls number, seed cotton yield) were significantly negatively correlated (p < 0.05) with the soil RPF amount. The RPF25 treatment showed yield decreases of up to 33.4% and 43.2% in these two years, respectively, compared with the RPF0 treatment. Surprisingly, the presence of RPF in soil reduced the rate and cumulative CO2 emissions from cotton fields during the growth and fallow periods, but carbon sequestration in cotton fields decreased significantly with increasing RPF amounts (15.05%~60.98% in 2020 and 17.38~76.81% in 2021). RPF inhibited cotton root growth, reducing plant biomass accumulation, decreasing seed cotton yield, and weakening cotton fields' carbon sink. When the RPF amount in the soil was less than or equal to 228.03 kg ha–1, cotton economic benefits and field carbon storage were not unduly weakened. The second-year indicators of cotton fields with the RPF were significantly lower than the first year, and the permanent residue of soil RPF also created a more hostile crop growing environment. We concluded that the RPF amount in fields should be reduced as soon as possible and that more environmentally friendly and carbon-reducing mulching materials should be used instead of plastic film.
In the soil environment, microplastics are often present together with other contaminants. The co-exposure to microplastics and other contaminants may result in combined effects on soil organisms. This paper summarizes recent research advances in the combined effects of microplastics and heavy metals/hydrophobic organic contaminants (HOCs) on earthworms. The effects of co-exposure on earthworms are mainly in the aspects of contaminants bioaccumulation and the mortality, behavior, growth, reproduction, oxidative response, and gut microbiota of earthworms. In general, microplastics can exacerbate the adverse effects of other contaminants on earthworms, such as facilitating the accumulation of other contaminants in earthworms, inhibiting growth rates, aggravating oxidative damage, and changing gut microbiota of earthworms. Research limitations and current gaps are discussed, and future perspectives are proposed.
Plastics are ubiquitous. It has been used in human activities, from agriculture to packaging, infrastructure, and health. The wide range of usage makes plastics an omnipresent pollutant in the environment. This study investigated the abundance and type of plastics in agricultural soil in the Adana/Karataş region in Turkey, where disposable low-tunnel greenhouse plastic films and irrigation pipes were in use. For this purpose, 1 kg of soil samples from the top 5 cm (from the surface) was taken from 10 different sampling locations. An average of 16.5 ± 2.4 pcs/kg was found in the soil samples. The highest amount of plastics was seen at the Bahçe-4 location with 39.7 ± 12 pcs/kg and the lowest amount of plastics at the Karataş-1 location with 0.7 ± 0.3 pcs/kg. The average size of plastics was found to be 18.2 ± 1.3 mm. The average size of plastics originating from greenhouse cover was 18.9 ± 1.4 mm, and from disposable irrigation pipes was 12.5 ± 3.5 mm. It was determined that 41.9% of extracted plastics were microplastics, 36.3% were mesoplastics, 16.3% were macroplastics, and 5.6% were megaplastics. Results indicated that residual plastics decreased in the soil where used plastics were removed after usage. As a result, it is worth noting that a significant amount of plastics remain in soil due to plastics being used in agricultural areas.
Graphical abstract
Contamination of soil by plastics is a global environmental issue. Plastics pollution has been detected and is showing a regular increase in both water and land ecosystems. There are many researches reporting the profound effects of plastics on soil quality parameters and its biota. This review provides information sources, abundance, distribution, toxic effects, and control measures of plastics in soil environment especially agricultural ecosystems. The use of plastics as sewage sludge, packaging material, plastic mulches, and compost is the major source of soil contamination. Soil environment may receive plastics directly or indirectly from different sources. When plastics accumulate in the soil, they may be combined with other soil contaminants such as heavy metals (HMs), persistent organic pollutants (POPs), antibiotics, and many other toxic substances, which have a greater harmful impact on soil quality, flora, and fauna. There are only few reports available on the biological effects of plastics on soil due to the lack of data from field and laboratory studies. More research data is required to understand completely the role of plastics as environmental contaminants and vectors of other contaminants which can enter the food chain. Gap of knowledge is still there on plastic pollution and its impact on soil environment which need to be fully revealed. This global environmental issue deserves more attention from the researchers and policymakers in the future.
Healthcare waste includes the waste generated by healthcare facilities, medical laboratories and biomedical research facilities. Improper treatment of this waste stands severe risks of disease transmission to waste pickers, waste workers, health workers, patients, and the community in general through exposure to infectious agents. Poor management of the waste emits destructive and deleterious contaminants into society. The WHO has established guidelines for management of healthcare waste. These guidelines are assisting to manage the highly contagious healthcare waste resulting from the current pandemic. Proper healthcare waste management may add value by lower
the spread of the COVID-19 virus and raising the recyclability of materials instead of sending them to landfill. Disinfecting and sorting out healthcare waste facilitate sustainable management and enable their utilization for valuable purposes. This review discusses the various healthcare solid waste management strategies and the possible solutions for overcoming these challenges. It also provides useful knowledge’s into healthcare solid waste management scenarios during the COVID-19 pandemic and a possible way forward.
Recent studies have been engaged in estimating the adverse effects of microplastic (MP) on soil quality parameters. Mass concentrations of MP, as found in highly contaminated soils, have been shown to weaken the soil structure, and parts of the edaphon are adversely affected mainly by the
<100 µm MP size fraction. However, the vast majority of these studies used pristine particles, which have surface characteristics different from those of environmental MP. Exposed to UV radiation, plastic
undergoes photochemical weathering with embrittlement and the formation of surface charge, leading to an alteration of physiochemical behavior. When plastic particles then enter the soil environment, further aging factors appear with yet unknown efficacy. This little explored soil biogeochemical phase includes biofilm cover, decay with enzymes (as shown in laboratory experiments with both conventional and biodegradable plastics), contact with biotic and abiotic acids, oxidants, and uptake by the soil fauna that causes physical fragmentation. Such transformation of the surfaces is assumed to affect soil aggregation processes, soil faunal health, and the transport of
plastic colloids and adsorbed solubles. This perspective article encourages us to consider the weathering history of MP in soil experiments and highlights the need for reproducing the surface characteristics of soil MP to conduct laboratory experiments with closer-to-nature results.
The organic manures contain large proportion of organic matter, small quantities of plant nutrients and play pivotal role in improving the soil physical, chemical and biological properties. The use of FYM and compost in agriculture is an age old practice to improve crop productivity. The inoculations of microorganisms in soil are also beneficial for maintaining soil health though decomposition of organic matter, N fixation, solubilization/mineralization, production of antibiotics and plant growth regulators etc. In the paper, the roles of vermicompost, FYM and biofertilizers on crop productivity and soil health have been discussed in detail. The bioxidation and stabilization of organic material by using earthworms and mesophilic microorganisms is known as vermicomposting. The vermicompost applications in soil stimulate soil microbial activity and mineralization processes. The application of FYM and vermicompost boost the activities of beneficial soil microorganisms and improve the supply of mineral nutrients, soil structure, water retention capability and enzymatic activities. Seed or soil inoculated biofertilizers promotes the nutrient cycling and improves crop productivity with two ways i.e. direct - N fixation, solubilization of nutrients production of phytohormones, indirect – development of resistance in plant against the stress and diseases and heavy metals bioremediation. The use of manures along with biofertilizers in farming ensures the improvement in soil biodiversity and food safety for human consumption. The use of manures in agriculture is essential for sustainable production systems and to keep the soil alive and healthy.
Biochar particles are extensively used in soil remediation and interact with microplastics (MPs), especially metal oxide-modified biochar may have stronger interactions with MPs. The mechanism of interactions between humic acid (HA) and different valence cations is different and the co-effect on the transport of MPs is not clear. In this study, the co-effects of HA and cations (Na⁺, Ca²⁺) on the transport and retention of MPs in saturated porous media with peanut shell biochar (PSB) and MgO-modified PSB (MgO-PSB) were systematically investigated. Breakthrough curves (BTCs) of MPs were fitted by the two-site kinetic retention model for analysis. In the absence of HA, the addition of PSB and MgO-PSB significantly hindered the transport of MPs in saturated porous media, and the retention of microplastics increased from 34.2% to 59.1% and 75.5%, respectively. In Na⁺ solutions, the HA concentration played a dominant role in controlling MPs transport, compared to the minor role of Na⁺. The transport capacity of MPs always increased gradually with the increase of HA concentration. Whereas, in Ca²⁺ solutions, Ca²⁺ concentrations had a stronger effect than HA. The transport ability of MPs was instead greater than that in Na ⁺ solutions as the HA concentration increased at low ionic strength (1 mM). However, the transport capacity of MPs was significantly reduced with increasing HA concentrations at higher ionic strength (10, 100 mM). The two-site kinetic retention model indicated that chemical attachment and physical straining are the main mechanisms of MPs retention in the filled columns.
In recent years, the intensification in environmental pollution with micro and nano-plastics (MNPs) has become a global environmental concern. MNPs are some of the emerging contaminants that appear as new challenges to the scientific community because of their adverse effect on human health and environment. Conventional wastewater treatment plants (WWTPs) can efficiently remove the MNPs from the wastewater. The reduction of MNPs from WWTPs has attracted much attention in the past decades. Despite the efficient removal, WWTPs are considered one of the key routes through which MNPs have been introduced to the environment, through the large volumes of effluent continually released to the water bodies. Therefore, a detailed understanding of the behavior of MNPs and their removal mechanisms in WWTPs is highly essential. Nevertheless, an inclusive review of the MNPs treatment techniques in WWTPs is infrequent. So, we review the treatment processes presently employed for MNPs removal in WWTPs to upgrade the existing designs further. In addition, the effectiveness of advanced treatment processes, such as membrane technologies, advanced oxidation process, electro-coagulation, nano technology, etc., in eliminating MNPs are presented and discussed. However, possible toxic microbial biotransformation of MNPs during biological treatment steps in WWTPs needs to be taken care of via further in-depth research. As a basic knowledge of removal mechanisms in WWTPs could reduce the environmental pervasiveness of MNPs, this review is likely to offer helpful information in establishing an efficient approach to control and minimize environmental pollution from MNPs.
Microplastic (MP) is one of the largest issues within which the global terrestrial environment, flora, fauna, and water bodies are now facing problems. The existence of MPs is abundant in our ecosystem. It has entered our food chain and food web and has become a serious issue that should be discussed worldwide. It is the result of anthropogenic activities and inappropriate disposal of plastics by humans. MPs are more dangerous because they transfer into higher organisms through trophic levels and biological magnification. MPs are considered an invisible peril to human health. In the case of soil microbes and animals, studies reveal that after ingestion, they alter digestive systems, circulatory systems, reproductive organs, and feeding behavior, which results in stagnant growth. The main aim of this chapter is to explain the various issues faced when MPs enter into the environment. We also broadly discuss microbes, animals, occurrences, distributions, mechanisms of entry, accumulation, and ecological effects into soils. Therefore, research on the interactions with MPs would provide an understanding of its interactions and impacts to the organisms in the ecosystems.
Microplastics may be potential vectors for environmental contaminants such as heavy metals in the aquatic ecosystem due to their highly hydrophobic surfaces and fugacity property. To investigate the combined effects of microplastics with Pb, we exposed juvenile Chinese mitten crabs Eriocheir sinensis to different Pb concentrations (0, 5 and 50 μg/L) combined with microplastics (0 and 400 μg/L) for 21 days to determine the Pb bioaccumulation, oxidative stress, lipid anabolism, and histopathology of hepatopancreas. In general, the results showed that compared to single Pb exposure, the combination of MPs and Pb significantly increased the bioaccumulation of Pb, activities/content of antioxidant biomarkers and lipid metabolism enzymes, and liver injury parameters in crabs, indicating MPs are potential vector of heavy metals and co-exposure exerts more severe effects on crabs. This study provides the insights into the oxidative defense and preliminary lipid anabolism of economic crustaceans in response to combined stress of Pb and MPs.
Soils are both a sink and a pathway of plastic wastes, but there is a great lack of knowledge regarding their impacts on soil biota. To tackle the mechanisms of toxicty of these contaminants to soil invertebrates, earthworms (Eisenia fetida Savigny 1826) were exposed during 28 days to different concentrations of low-density polyethylene microplastics (62, 125, 250, 500 and 1000 mg MPs kg-1 soildw) with sizes ranging between 250-1000 m, in an artificial soil. The ecotoxicological responses were evaluated by analysing various oxidative stress biomarkers (catalase, glutathione S-transferase, and thiobarbituric acid reactive substances), a biomarker of energy metabolism (lactate dhydrogenase) and overall organism molecular changes by Fourier-transform Infrared Spectrometry (FTIR) and Nuclear Magnetic Resonance (NMR) analyses. Significant effects resulting from an unbalanced oxidative stress system, expressed in terms of thiobarbituric acid reactive substances levels were recorded on earthworms exposed at the three highest concentrations tested. Despite that, no significant changes were recorded on the molecular profiles of earthworms by FTIR-ATR. NMR analysis pointed out for differences from the control, only for earthworms exposed to the lowest concentration of MPs. Considering that stress responses are complex, and involve multiple mechanisms, a cluster analysis taking into account all the parameters assessed , clearly identified two groups of eartworms separated by the concentration of 250 mg MPs kg soildw, above each meaningful effects were recorded.
The contamination of the environment with microplastic, defined as particles smaller than 5 mm, has emerged as a global challenge because it may pose risks to biota and public health. Current research focuses predominantly on aquatic systems, whereas comparatively little is known regarding the sources, pathways, and possible accumulation of plastic particles in terrestrial ecosystems. We investigated the potential of organic fertilizers from biowaste fermentation and composting as an entry path for microplastic particles into the environment. Particles were classified by size and identified by attenuated total reflection-Fourier transform infrared spectroscopy. All fertilizer samples from plants converting biowaste contained plastic particles, but amounts differed significantly with substrate pretreatment, plant, and waste (for example, household versus commerce) type. In contrast, digestates from agricultural energy crop digesters tested for comparison contained only isolated particles, if any. Among the most abundant synthetic polymers observed were those used for common consumer products. Our results indicate that depending on pretreatment, organic fertilizers from biowaste fermentation and composting, as applied in agriculture and gardening worldwide, are a neglected source of microplastic in the environment.
Microplastic particles in terrestrial and aquatic ecosystems are currently discussed as an emerging persistent organic pollutant and as acting as a vector for hydrophobic chemicals. Microplastic particles may ultimately deposit and accumulate in soil as well as marine and freshwater sediments where they can be harmful to organisms. In this study, we tested the sensitivity of natural freshwater sediment bacterial communities (by genetic fingerprint) to exposure to microplastics (polyethylene, 2 and 20 mg/g sediment) and microplastics loaded with polycyclic aromatic hydrocarbons (PAHs, phenanthrene and anthracene), using a laboratory-based approach. After two weeks of incubation, the bacterial community composition from an unpolluted river section was altered by high concentrations of microplastics, whereas the community downstream of a wastewater treatment plant remained unchanged. Low microplastic concentrations loaded with phenanthrene or anthracene induced a less pronounced response in the sediment communities compared to the same total amount of phenanthrene or anthracene alone. In addition, biodegradation of the PAHs was reduced. This study shows, that microplastic can affect bacterial community composition in unpolluted freshwater sediments. Moreover, the results indicate that microplastics can serve as a vehicle for hydrophobic pollutants but bioavailability of the latter is reduced by the sorption to microplastics.
Synthetic polymers are one of the most significant pollutants in the aquatic environment. Most research focused on small plastic particles, so-called microplastics (particle size, 1–5,000 μm). Compared to macroplastics, the small size complicates their determination in environmental samples and demands for more sophisticated analytical approaches. The detection methods of microplastics reported in the past are highly diverse. This chapter summarizes different strategies for the sampling of water and sediment and sample treatments, including the separation of plastic particles and removal of natural debris that are necessary prior the identification of microplastics. Moreover, the techniques used for the identification of plastics particles are presented in this chapter.
We live in a plastic age (Thompson et al., 2009), with microplastic (typically defined as plastic particles < 5 mm) becoming an increasingly appreciated aspect of environmental pollution. Research has been overwhelmingly focused on aquatic systems, especially the oceans, but there is a current shift to more strongly consider terrestrial ecosystems (Rillig, 2012; Horton et al., 2017). In particular agroecosystems are coming into focus as a major entry point for microplastics in continental systems (Nizzetto et al., 2016b), where contamination might occur via different sources as sludge amendment or plastic mulching (Steinmetz et al., 2016). Given the central role of agroecosystems, including their soil biodiversity (Rillig et al., 2016), in food production, such numbers are potential cause for concern. Field data on measured microplastic presence in agricultural soils are still not widely available, but nevertheless this material is certain to arrive at the soil surface. The fate of material deposited at the soil surface is not clear: particles may be removed by wind or water erosion, becoming airborne, or may be lost by surface runoff (Nizzetto et al., 2016a). Nevertheless, a substantial part of the microplastic (or nanoplastic following further disintegration) is expected to enter the soil.
The degree of hazard represented by microplastic to various soil biota is not clear. Direct evidence comes from experimental work on earthworms, on which microbeads had negative effects (Huerta Lwanga et al., 2016; also reviewed in Horton et al., 2017). Data on impacts on other soil biota groups are not available. However, Kiyama et al. (2012) have shown that polystyrene beads can be taken up by the nematode Caenorhabditis elegans; this means the material could also accumulate in the soil food web (Rillig, 2012). Movement into soil is an important aspect of assessing risk: will soil biota be exposed to microplastics? Here, we sketch what is known about movement of such particles in soil, which players and factors could influence this, and we chart avenues for research aimed at the movement and distribution of microplastic in agricultural soils.
Microplastics are widely dispersed throughout the marine environment. An understanding of the distribution and accumulation of this form of pollution is crucial for gauging environmental risk. Presented here is the first record of plastic contamination, in the 5 mm–250 μm size range, of Irish continental shelf sediments. Sixty-two microplastics were recovered from 10 of 11 stations using box cores. 97% of recovered microplastics were found to reside shallower than 2.5 cm sediment depth, with the area of highest microplastic concentration being the water-sediment interface and top 0.5 cm of sediments (66%). Microplastics were not found deeper than 3.5 ± 0.5 cm. These findings demonstrate that microplastic contamination is ubiquitous within superficial sediments and bottom water along the western Irish continental shelf. Results highlight that cores need to be at least 4–5 cm deep to quantify the standing stock of microplastics within marine sediments. All recovered microplastics were classified as secondary microplastics as they appear to be remnants of larger items; fibres being the principal form of microplastic pollution (85%), followed by broken fragments (15%). The range of polymer types, colours and physical forms recovered suggests a variety of sources. Further research is needed to understand the mechanisms influencing microplastic transport, deposition, resuspension and subsequent interactions with biota.
Plastics have outgrown most man-made materials and have long been under environmental scrutiny. However, robust global information, particularly about their end-of-life fate, is lacking. By identifying and synthesizing dispersed data on production, use, and end-of-life management of polymer resins, synthetic fibers, and additives, we present the first global analysis of all mass-produced plastics ever manufactured. We estimate that 8300 million metric tons (Mt) as of virgin plastics have been produced to date. As of 2015, approximately 6300 Mt of plastic waste had been generated, around 9% of which had been recycled, 12% was incinerated, and 79% was accumulated in landfills or the natural environment. If current production and waste management trends continue, roughly 12,000 Mt of plastic waste will be in landfills or in the natural environment by 2050.
Despite great general benefits derived from plastic use, accumulation of plastic material in ecosystems, and especially microplastic, is becoming an increasing environmental concern. Microplastic has been extensively studied in aquatic environments, with very few studies focusing on soils. We here tested the idea that microplastic particles (polyethylene beads) could be transported from the soil surface down the soil profile via earthworms. We used Lumbricus terrestris L., an anecic earthworm species, in a factorial greenhouse experiment with four different microplastic sizes. Presence of earthworms greatly increased the presence of microplastic particles at depth (we examined 3 soil layers, each 3.5 cm deep), with smaller PE microbeads having been transported downward to a greater extent. Our study clearly shows that earthworms can be significant transport agents of microplastics in soils, incorporating this material into soil, likely via casts, burrows (affecting soil hydraulics), egestion and adherence to the earthworm exterior. This movement has potential consequences for exposure of other soil biota to microplastics, for the residence times of microplastic at greater depth, and for the possible eventual arrival of microplastics in the groundwater.
Microplastics are widespread contaminants in terrestrial environments but comparatively little is known about interactions between microplastics and common terrestrial contaminants such as zinc (Zn). In adsorption experiments fragmented HDPE bags c. 1 mm2 in size showed similar sorption characteristics to soil. However, when present in combination with soil, concentrations of adsorbed Zn on a per mass basis were over an order of magnitude lower on microplastics . Desorption of the Zn was minimal from both microplastics and soil in synthetic soil solution (0.01 M CaCl2), but in synthetic earthworm guts desorption was higher from microplastics (40 - 60%) than soil (2 - 15 %), suggesting microplastics could increase Zn bioavailability. Individual Lumbricus terrestris earthworms exposed for 28 days in mesocosms of 260 g moist soil containing 0.35 wt% of Zn-bearing microplastic (236-4505 mg kg-1) ingested the microplastics, but there was no evidence of Zn accumulation, mortality or weight change. Digestion of the earthworms showed that they did not retain microplastics in their gut. These findings indicate that microplastics could act as vectors to increase metal exposure in earthworms, but that the associated risk is unlikely to be significant for essential metals such as Zn that are well regulated by metabolic processes.
Although the earthworm Eisenia fetida has been used in many ecotoxicological studies in recent years, most of these studies have only focused on assessing the effects of individual insecticides. In the present study, we aimed to compare the individual and combined toxic effects of imidacloprid and three insecticides (phoxim, chlorpyrifos, and lambda-cyhalothrin) on E. fetida. We showed that imidacloprid had the highest intrinsic toxicity to the worms in filter paper contact test, followed by phoxim and lambda-cyhalothrin, while the least toxicity was found from chlorpyrifos. Moreover, 14-day soil toxicity test revealed that the highest toxicity was still detected for imidacloprid with an LC50 value of 2.82 (2.61∼3.17) mg a.i. kg⁻¹ dry weight (DW), followed by chlorpyrifos with an LC50 value of 384.9 (353.5∼440.3) mg a.i. kg⁻¹ DW. Meanwhile, a relatively less toxicity was found for lambda-cyhalothrin with an LC50 value of 560.3 (475.9∼718.5) mg a.i. kg⁻¹ DW, while the lowest toxicity to E. fetida was observed for phoxim with an LC50 value of 901.5 (821.3∼1017) mg a.i. kg⁻¹ DW. In addition, significant synergistic responses were found from the ternary mixture of imidacloprid-phoxim-lambda-cyhalothrin and quaternary mixture of imidacloprid-phoxim-chlorpyrifos-lambda-cyhalothrin in both bioassay systems. Therefore, our findings highlighted that the simultaneous presence of several insecticides in the soil environment might lead to increased toxicity, resulting in serious damage to the nontarget organisms compared with individual insecticides.
Plastic debris is an environmentally persistent and complex contaminant of increasing concern. Understanding the sources, abundance and composition of microplastics present in the environment is a huge challenge due to the fact that hundreds of millions of tonnes of plastic material is manufactured for societal use annually, some of which is released to the environment. The majority of microplastics research to date has focussed on the marine environment. Although freshwater and terrestrial environments are recognised as origins and transport pathways of plastics to the oceans, there is still a comparative lack of knowledge about these environmental compartments. It is highly likely that microplastics will accumulate within continental environments, especially in areas of high anthropogenic influence such as agricultural or urban areas. This review critically evaluates the current literature on the presence, behaviour and fate of microplastics in freshwater and terrestrial environments and, where appropriate, also draws on relevant studies from other fields including nanotechnology, agriculture and waste management. Furthermore, we evaluate the relevant biological and chemical information from the substantial body of marine microplastic literature, determining the applicability and comparability of this data to freshwater and terrestrial systems. With the evidence presented, the authors have set out the current state of the knowledge, and identified the key gaps. These include the volume and composition of microplastics entering the environment, behaviour and fate of microplastics under a variety of environmental conditions and how characteristics of microplastics influence their toxicity. Given the technical challenges surrounding microplastics research, it is especially important that future studies develop standardised techniques to allow for comparability of data. The identification of these research needs will help inform the design of future studies, to determine both the extent and potential ecological impacts of microplastic pollution in freshwater and terrestrial environments.
Biodiversity is responsible for the provision of many ecosystem services; human well-being is based on these services, and consequently on biodiversity. In soil, earthworms represent the largest component of the animal biomass and are commonly termed ‘ecosystem engineers’. This review considers the contribution of earthworms to ecosystem services through pedogenesis, development of soil structure, water regulation, nutrient cycling, primary production, climate regulation, pollution remediation and cultural services. Although there has been much research into the role of earthworms in soil ecology, this review demonstrates substantial gaps in our knowledge related in particular to difficulties in identifying the effects of species, land use and climate. The review aims to assist people involved in all aspects of land management, including conservation, agriculture, mining or other industries, to obtain a broad knowledge of earthworms and ecosystem services.
Marine debris, mostly consisting of plastic, is a global problem, negatively impacting wildlife, tourism and shipping. However, despite the durability of plastic, and the exponential increase in its production, monitoring data show limited evidence of concomitant increasing concentrations in marine habitats. There appears to be a considerable proportion of the manufactured plastic that is unaccounted for in surveys tracking the fate of environmental plastics. Even the discovery of widespread accumulation of microscopic fragments (microplastics) in oceanic gyres and shallow water sediments is unable to explain the missing fraction. Here, we show that deep-sea sediments are a likely sink for microplastics. Microplastic, in the form of fibres, was up to four orders of magnitude more abundant (per unit volume) in deep-sea sediments from the Atlantic Ocean, Mediterranean Sea and Indian Ocean than in contaminated sea-surface waters. Our results show evidence for a large and hitherto unknown repository of microplastics. The dominance of microfibres points to a previously underreported and unsampled plastic fraction. Given the vastness of the deep sea and the prevalence of microplastics at all sites we investigated, the deep-sea floor appears to provide an answer to the question-where is all the plastic?
Acetylcholinesterase is involved in the termination of impulse transmission by rapid hydrolysis of the neurotransmitter acetylcholine in numerous cholinergic pathways in the central and peripheral nervous systems. The enzyme inactivation, induced by various inhibitors, leads to acetylcholine accumulation, hyperstimulation of nicotinic and muscarinic receptors, and disrupted neurotransmission. Hence, acetylcholinesterase inhibitors, interacting with the enzyme as their primary target, are applied as relevant drugs and toxins. This review presents an overview of toxicology and pharmacology of reversible and irreversible acetylcholinesterase inactivating compounds. In the case of reversible inhibitors being commonly applied in neurodegenerative disorders treatment, special attention is paid to currently approved drugs (donepezil, rivastigmine and galantamine) in the pharmacotherapy of Alzheimer's disease, and toxic carbamates used as pesticides. Subsequently, mechanism of irreversible acetylcholinesterase inhibition induced by organophosphorus compounds (insecticides and nerve agents), and their specific and nonspecific toxic effects are described, as well as irreversible inhibitors having pharmacological implementation. In addition, the pharmacological treatment of intoxication caused by organophosphates is presented, with emphasis on oxime reactivators of the inhibited enzyme activity administering as causal drugs after the poisoning. Besides, organophosphorus and carbamate insecticides can be detoxified in mammals through enzymatic hydrolysis before they reach targets in the nervous system. Carboxylesterases most effectively decompose carbamates, whereas the most successful route of organophosphates detoxification is their degradation by corresponding phosphotriesterases.
The use of plastic mulch in agriculture has increased dramatically in the last 10 years throughout the world. This increase is due to benefits such as increase in soil temperature, reduced weed pressure, moisture conservation, reduction of certain insect pests, higher crop yields, and more efficient use of soil nutrients. However, disposing of used plastic films, which cause pollution, has led to development of photodegradable and biodegradable mulches. Here we review the use of plastic mulches in agriculture, with special reference to biodegradable mulches. Major topics discussed are (1) history of plastic mulch and impact on crop yield and pest management, (2) limitations of polyethylene mulches and potential alternatives, (3) biodegradable and photodegradable plastic mulches, (4) field performance of biodegradable mulches, and (5) use of biodegradable plastic mulches in organic production. We found that (1) despite multiple benefits, removal and disposal of conventional polyethylene mulches remains a major agronomic, economic, and environmental constraint; (2) early use of photodegradable plastic mulch during the 1970s and 1980s, wrongly named biodegradable mulch films, discouraged adoption of new biodegradable mulch films because they were too expensive and their breakdown was unpredictable; (3) biodegradable plastic films are converted through microbial activity in the soil to carbon dioxide, water, and natural substances; (4) polymers such as poly(lactic acid), poly(butylene adipate-coterephthalate), poly(ε-caprolactone), and starch-based polymer blends or copolymers can degrade when exposed to bioactive environments such as soil and compost; (5) with truly biodegradable materials obtained from petroleum and natural resources, opportunity for using biodegradable polymers as agricultural mulch films has become more viable; and (6) the source of polymer and additives may limit use of some biodegradable mulches in organic production. More knowledge is needed on the effect of biodegradable mulches on crop growth, microclimate modifications, soil biota, soil fertility, and yields.
The intensive use of pesticide and plastic mulches has considerably enhanced crop growth and yield. Pesticide residues and plastic debris, however, have caused serious environmental problems. This study investigated the effects of the commonly used herbicide glyphosate and micrometre-sized plastic debris, referred as microplastics, on glyphosate decay and soil microbial activities in Chinese loess soil by a microcosm experiment over 30 days incubation. Results showed that glyphosate decay was gradual and followed a single first-order decay kinetics model. In different treatments (with/without microplastic addition), glyphosate showed similar half-lives (32.8 days). The soil content of aminomethylphosphonic acid (AMPA), the main metabolite of glyphosate, steadily increased without reaching plateau and declining phases throughout the experiment. Soil microbial respiration significantly changed throughout the entirety of the experiment, particularly in the treatments with higher microplastic addition. The dynamics of soil β-glucosidase, urease and phosphatase varied, especially in the treatments with high microplastic addition. Particles that were considerably smaller than the initially added microplastic particles were observed after 30 days incubation. This result thus implied that microplastic would hardly affect glyphosate decay but smaller plastic particles accumulated in soils which potentially threaten soil quality would be further concerned especially in the regions with intensive plastic mulching application.
Plastic particle accumulation in arable soils is a growing contaminant of concern with unknown consequences for
soil productivity and quality. This study aimed to investigate abundance and distribution of plastic particles
among soil aggregate fractions in four cropped areas and an established riparian forest buffer zone at Dian
Lake, southwestern China. Plastic particles (10–0.05 mm) from fifty soil samples were extracted and then sorted
by size, counted, and categorized. Plastic particles were found in all soil samples. The concentration of plastic par-
ticles ranges from 7100 to 42,960 particles kg−1 (mean 18,760 particles kg−1
). 95% of the sampled plastic parti-
cles are in the microplastic size (1–0.05 mm) range. The predominant form is plastic fibers, making up on average
92% of each sample followed by fragments and films that contributed with to 8%. Results of this study also show
that 72% of plastic particles are associated with soil aggregates, and 28% of plastic particles are dispersed. The
abundance of aggregate-associated plastic fibers is significantly greater in the micro-aggregate than that in the
macro-aggregate, whereas the less concentrations of plastic films and fragments are found in the micro-
aggregate. Compared to the adjacent vegetable soil, the less concentration of plastic particles in the buffer soil im-
plicates that application of soil amendments and irrigation with wastewater must be controlled to reduce accu-
mulation of microplastics in agricultural soils. While the implications of microplastic on ecological and human health are poorly understood, the staggering number of microplastic in agricultural soils should be continually concerned in the future.
Complex and organic-rich solid substrates such as sludge and soil have been shown to be contaminated by microplastics; however, methods for extracting plastic particles have not yet been systemically tested or standardised. This study investigated four main protocols for the removal of organic material during analysis of microplastics from complex solid matrices: oxidation using H2O2, Fenton’s reagent, and alkaline digestion with NaOH and KOH. Eight common polymer types were used to assess the influence of reagent exposure on particle integrity. Organic matter removal efficiencies were established for test sludge and soil samples. Fenton’s reagent was identified as the optimum protocol. All other methods showed signs of particle degradation or resulted in an insufficient reduction in organic matter content. A further validation procedure revealed high microplastic extraction efficiencies for particles with different morphologies. This confirmed the suitability of Fenton’s reagent for use in conjunction with density separation for extracting microplastics. This approach affords greater comparability with existing studies that utilise a density-based technique. Recommendations for further method optimisation were also identified to improve the recovery of microplastic from complex, organic-rich environmental samples.
Furan is a common food contaminant and environmental pollutant. Spirulina platensis (SP) is a blue-green algae extensively used as therapeutic and health supplements. This study aimed to explore the probable beneficial role of SP against the influence of furan on reproductive system of male rats. Adult male rats were divided into control, vehicle control, SP (300 mg/kg bwt/ day, 7 days), furan (16 mg/kg bwt/ day,30 day), SP/furan, furan/SP and furan+SP groups. Hematology, sperm count, sperm morphology, serum testosterone (TES), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and estradiol (E2) levels, reduced glutathione (GSH), malondialdehyde (MDA), testicular enzymes, and pro inflammatory cytokines were estimated. In addition, histopathology of testis and seminal vesicles and apoptosis were evaluated. Anaemia, leukocytosis, and reduced gonadosomatic index were observed in the furan treated group. TES, LH, FSH, E2, and GSH were significantly decreased following furan treatment. MDA, testicular enzymes, and pro inflammatory cytokines were significantly incremented in testis of furan treated rats. Furan induced apoptic changes in testis. SP significantly counteracted furan reprotoxic impacts, particularly at co-exposure. Conclusively, these findings verified that SP could be candidate therapy against furan reprotoxic impacts.
The interaction of plastics with hydrophobic organic compounds (HOCs) is well established. Several HOCs are known carcinogens and/or endocrine disruptors. To determine how chemicals in plastic affect the marine environment, it is necessary to understand the kinetics of HOC sorption/desorption. This includes the understanding of sorption kinetics and mechanisms along with simple modeling concepts such as the first order rate kinetic model that can often adequately describe the overall phenomenon. However, to more mechanistically understand the chemical uptake and desorption process, the diffusion of chemicals in plastic is also discussed as well as the direct observation of this process in sectioned plastic particles. Moreover, modeling is required to understand the diffusion of chemicals in microplastic particles. In addition, case studies from the literature are presented which seek to understand how compounds move in and out of the plastics found in the marine environment or when in contact with other fluids besides seawater such as stomach fluids or fish oil.
Microplastics are ubiquitous not just in the ocean but also on land and in freshwater systems
Microplastics and nanoplastics are emerging pollutants of global importance. They are small enough to be ingested by a wide range of organisms and at nano-scale, they may cross some biological barriers. However, our understanding of their ecological impact on the terrestrial environment is limited. Plastic particle loading in agroecosystems could be high due to inputs of some recycled organic waste and plastic film mulching, so it is vital that we develop a greater understanding of any potentially harmful or adverse impacts of these pollutants to agroecosystems. In this article, we discuss the sources of plastic particles in agroecosystems, the mechanisms, constraints and dynamic behaviour of plastic during aging on land, and explore the responses of soil organisms and plants at different levels of biological organisation to plastic particles of micro and nano-scale. Based on limited evidence at this point and understanding that the lack of evidence of ecological impact from microplastic and nanoplastic in agroecosystems does not equate to the evidence of absence, we propose considerations for addressing the gaps in knowledge so that we can adequately safeguard world food supply.
This article introduces a simple and cost-saving method developed to extract, distinguish and quantify light density microplastics of polyethylene (PE) and polypropylene (PP) in soil. A floatation method using distilled water was used to extract the light density microplastics from soil samples. Microplastics and impurities were identified using a heating method (3-5s at 130°C). The number and size of particles were determined using a camera (Leica DFC 425) connected to a microscope (Leica wild M3C, Type S, simple light, 6.4×). Quantification of the microplastics was conducted using a developed model. Results showed that the floatation method was effective in extracting microplastics from soils, with recovery rates of approximately 90%. After being exposed to heat, the microplastics in the soil samples melted and were transformed into circular transparent particles while other impurities, such as organic matter and silicates were not changed by the heat. Regression analysis of microplastics weight and particle volume (a calculation based on image J software analysis) after heating showed the best fit (y=1.14x+0.46, R(2)=99%, p<0.001). Recovery rates based on the empirical model method were >80%. Results from field samples collected from North-western China prove that our method of repetitive floatation and heating can be used to extract, distinguish and quantify light density polyethylene microplastics in soils. Microplastics mass can be evaluated using the empirical model.
At least 300 Mio t of plastic are produced annually, from which large parts end up in the environment, where it persists over decades, harms biota and enters the food chain. Yet, almost nothing is known about plastic pollution of soil; hence, the aims of this work are to review current knowledge on i) available methods for the quantification and identification of plastic in soil, ii) the quantity and possible input pathways of plastic into soil, (including first preliminary screening of plastic in compost), and iii) its fate in soil. Methods for plastic analyses in sediments can potentially be adjusted for application to soil; yet, the applicability of these methods for soil needs to be tested. Consequently, the current data base on soil pollution with plastic is still poor. Soils may receive plastic inputs via plastic mulching or the application of plastic containing soil amendments. In compost up to 2.38-1200mg plastic kg(-1) have been found so far; the plastic concentration of sewage sludge varies between 1000 and 24,000 plastic items kg(-1). Also irrigation with untreated and treated wastewater (1000-627,000 and 0-125,000 plastic items m(-3), respectively) as well as flooding with lake water (0.82-4.42 plastic items m(-3)) or river water (0-13,751 items km(-2)) can provide major input pathways for plastic into soil. Additional sources comprise littering along roads and trails, illegal waste dumping, road runoff as well as atmospheric input. With these input pathways, plastic concentrations in soil might reach the per mill range of soil organic carbon. Most of plastic (especially >1μm) will presumably be retained in soil, where it persists for decades or longer. Accordingly, further research on the prevalence and fate of such synthetic polymers in soils is urgently warranted.
Areas such as Douro Demarcated Region (Portugal), where vineyards are frequently located on steep slopes of narrow valleys, can be particularly sensitive to runoff and erosion processes. These particular conditions are expected to enhance the transport of pollutants, acting as a potential source of contamination to freshwater systems. The intense vine cultivation in this region includes decades of pesticides application, that have resulted in the accumulation of these chemicals and its degradation products in the vineyards soils and sediments. Residues of several pesticides related to agricultural activities were found in soils, with older vineyards showing higher levels of Cu and banned insecticides (such as DDT). The metabolite 4,4-DDE was the compound found at higher levels in soils and in sediments. The relatively high levels in more recent sediments suggest that soils are still a source of contamination. Levels of currently used pesticides were low, which is related with their physicochemical properties, the application period, and climacteric conditions.
The occurrence of microplastics (MPs) in saltwater bodies is relatively well studied, but nothing is known about their presence in most of the commercial salts that are widely consumed by humans across the globe. Here, we extracted MP-like particles larger than 149 μm from 17 salt brands originating from 8 different countries followed by the identification of their polymer composition using micro-Raman spectroscopy. Microplastics were absent in one brand while others contained between 1 to 10 MPs/Kg of salt. Out of the 72 extracted particles, 41.6% were plastic polymers, 23.6% were pigments, 5.50% were amorphous carbon, and 29.1% remained unidentified. The particle size (mean ± SD) was 515 ± 171 μm. The most common plastic polymers were polypropylene (40.0%) and polyethylene (33.3%). Fragments were the primary form of MPs (63.8%) followed by filaments (25.6%) and films (10.6%). According to our results, the low level of anthropogenic particles intake from the salts (maximum 37 particles per individual per annum) warrants negligible health impacts. However, to better understand the health risks associated with salt consumption, further development in extraction protocols are needed to isolate anthropogenic particles smaller than 149 μm.