Mitigating microplastic pollution: A critical review on the effects, remediation, and utilization strategies of microplastics.

Microplastics are found ubiquitous in the natural environment and are an increasing source of worry for global health. Rapid industrialization and inappropriate plastic waste management in our daily lives have resulted in an increase in the amount of microplastics in the ecosystem. Microplastics that are <150 µm in size could be easily ingested by living beings and cause considerable toxicity. Microplastics can aggregate in living organisms and cause acute, chronic, carcinogenic, developmental, and genotoxic damage. As a result, a sustainable approach to reducing, reusing, and recycling plastic waste is required to manage microplastic pollution in the environment. However, there is still a significant lack of effective methods for managing these pollutants. As a result, the purpose of this review is to convey information on microplastic toxicity and management practices that may aid in the reduction of microplastic pollution. This review further insights on how plastic trash could be converted as value-added products, reducing the load of accumulating plastic wastes in the environment, and leading to a beneficial endeavor for humanity.

A bibliometric analysis of global research hotspots and progress on microplastics in soil‒plant systems.

Plastic pollution has become a global and persistent challenge, posing threats to ecosystems and organisms. In recent years, there has been a rapid increase in scientific research focused on understanding microplastics in the soil‒plant system. This surge is primarily driven by the direct impact of microplastics on agricultural productivity and their association with human activities. In this study, we conducted a comprehensive bibliometric analysis to provide an overview of the current research on microplastics in soil‒plant systems. We systematically analysed 192 articles and observed a significant rise in research interests since 2017. Notably, China has emerged as a leading contributor in terms of published papers, closely followed by Germany and the Netherlands. Through co-authorship network analysis, we identified 634 different institutions that participated in publishing papers in this field, with the Chinese Academy of Sciences having the most collaborations. In the co-occurrence keyword network, we identified four clusters focusing on the diversity of microplastics within the agroecosystem, transportation, and quantification of microplastics in soil, analysis of plastic contamination type and impact, and investigation of microplastic phytotoxicity. Furthermore, we identified ten research priorities, categorized into the effects of microplastics in "soil" and "plant". The research hotspots were found to be the effect of microplastics on soil physicochemical properties and the synergistic phytotoxicity of microplastics with other pollutants. Overall, this bibliometric analysis holds significant value, serving as an important reference point and offering valuable suggestions for future researchers in this rapidly advancing field.

Different Species of Epigeic and Anecic Earthworms Cause Similarly Effective and Beneficial Biocomposting-A Case Study Involving the Pernicious Aquatic Weed Salvinia (Salvinia molesta, Mitchell).

As reported recently by the present authors, vermicomposting by the epigeic earthworm Eisenia fetida transforms the highly ligninous and allelopathic aquatic weed salvinia (Salvinia molesta) into a benign organic fertilizer. The present study was carried out with four other earthworm species, including three epigeic species of different sizes and phytophagic habits: Eisenia andrei, Lumbricus rubillus, and Perionyx sansibaricus. One anecic species, with geophytophagous habits, was also explored for comparison: Drawida willsi. The objective was to see whether the type of salvinia transformation caused by E. fetida is a general phenomenon or whether there are significant differences in the nature of biocomposts generated by different earthworm species. Accordingly, the characteristics of the biocomposts separately generated by each of the six species mentioned above were assessed with UV-visible spectrophotometry, Fourier-transform infrared spectrometry, differential scanning calorimetry, thermogravimetry, and scanning electron microscopy. The studies reveal that, with minor variations, the biocomposting by all four species was able to remove the intransigence of salvinia and impart plant/soil-friendly attributes to it in substantial measures. All the findings obtained with different techniques corroborated each other in arriving at this conclusion. Hence, it can be said that, in general, biocomposting by earthworms takes away the toxicity of pernicious weeds such as salvinia, converting them into plant-friendly and soil-friendly biofertilizers.

Greenhouse gas emission during swine manure aerobic composting: Insight from the dissolved organic matter associated microbial community succession.

Greenhouse gas emissions during aerobic composting is unavoidable, but good practices can minimize emission. Therefore, to explore the key factors influencing the release of greenhouse gas emissions during composting, the inaction of organic matter conversion, greenhouse gas emissions and bacterial community structure during co-composting with different ratio (pig manure and corn straw) over a 6-week period was studied. The excitation-emission matrix fluorescence spectroscopy with the parallel factor was used to identify that dissolved organic matter associated microbial community succession mainly influenced greenhouse gas emissions. Protein-like fractions of dissolved organic matter were more likely to decompose and promote CH4 and CO2 emissions, while the humic-like fractions of dissolved organic matter positively affected N2O emissions. The largest of greenhouse gas emissions was appeared in MR2 with 12.7 kg CO2-eq, and the MR3 and MR4 reduced greenhouse gas emissions by 26.8 % and 11.4 %, respectively.

Greenhouse gas emissions following biosolids application to farmland: Estimates from the DeNitrification and DeComposition model.

Municipal wastewater sludge may be processed into biosolids and applied to farmland for crop production, rather than be disposed of in landfills. Biosolids supply plant nutrients and increase soil organic carbon but also contribute to the production of greenhouse gases (GHGs). Computational models must therefore be refined to estimate the contribution of these gases to national GHG inventories. The DeNitrification and DeComposition (DNDC) model was evaluated for processes regulating crop growth, GHGs and soil C&N dynamics to determine its suitability for informing policy decision-making and advancing Canada's GHG inventory. Three years (2017-2019) of data were collected from replicated corn (Zea mays L.) plots in Quebec, Canada. The plots received 120 kg of available N ha-1 y-1 in mesophilic anaerobically digested biosolids, composted biosolids, alkaline-stabilized biosolids, urea, or combinations of these, while control plots were left unfertilized. Treatments receiving digested biosolids emitted more nitrous oxide (N2O) during the growing season than other treatments, while carbon dioxide (CO2) emissions were similar between treatments. After calibration, DNDC estimates were within the 95% confidence interval of the measured variables. Correlation coefficients (r) indicated discrepancies in trends between the estimated and measured values for daily CO2 and N2O emissions. These emissions were underestimated in the early and mid-growing season of 2018. They were more variable from plots fertilized with composted or alkaline-stabilized biosolids than from those with digested biosolids. Annual N2O emissions (r = 0.8), crop yields (r = 0.5), and soil organic carbon (r = 0.4) were modelled with higher accuracy than cumulative CO2 emissions (r = 0.3) and total soil N (r = 0.1). These findings suggest that DNDC is suitable for estimating field-scale N2O emissions following biosolids application, but estimates of CO2 emissions could be improved, perhaps by disaggregating the biosolids from the soil organic matter pools in the decomposition subroutines.

Role of different earthworm species in nullifying the toxicity of Ipomea carnea and enhancing its utility as a phytoremediator.

The dreaded weed ipomea (Ipomea carnea), has shown promise as a versatile phytoremediator. But I. carnea plants exude several alkaloids and phenols which are harmful to plants as well as animals. Due to this, the weed imparts as much or more toxicity to the soil as it remediates. These authors have earlier found that upon being vermicomposted by Eisenia fetida ipomea loses its toxicity and becomes a benign organic fertilizer with pest repellant attributes. These findings open up the possibility of using earthworms in those segments of land which are sought to be phytoremediated by ipomea so that the earthworms can keep converting the dead ipomea plants and the debris of live plants to fertilizer. The present work has aimed to determine whether the extent and nature of earthworm impact differs from species to species or is similar across different species. It has revealed that the action of each of the four different earthworm species deployed by the authors caused the C:N ratio of ipomea to change drastically ̶ from 28.20 to 15.95 ± 0.75, bringing the vermicomposts to the category of fertilizers fit for horticulture. The Fourier transform infrared (FTIR) spectra revealed that all the species caused a breakdown of the alkaloids and the phenolic compounds present in ipomea, resulting in the weed's detoxification. The earthworms also effected partial degradation of the lignocellulosic content of ipomea to simpler and more soil-friendly constituents like humic acids. Thermogravimetry, differential scanning calorimetry and scanning electron microscopy corroborated these findings. The influence exerted by the four species of earthworms was similarly beneficial in nature and extent.

First-ever study which establishes the general applicability of earthworms in nullifying the toxic impacts caused by ipomea during its use in phytoremediation, thereby greatly enhancing ipomea's value as a phytoremediator. The studies also provide an avenue for the utilization of the otherwise worthless ipomea harvested after phytoremediation or from natural stands.

Generation of highly potent organic fertilizer from pernicious aquatic weed Salvinia molesta.

Utilization of Salvinia molesta, an aquatic weed which is notorious for its allelopathy and invasiveness, has been explored by its vermicomposting. Fourier transform infrared spectroscopy (FT-IR) and plant bioassay tests were conducted to analyze the composition and fertilizer value of S .molesta vermicompost. Germination and seedling growth tests were performed in soil supplemented with vermicompost at levels ranging from 0.75 to 40% by weight of the soil on three common food plants, ladies finger (Abelmoschus esculentus), cucumber (Cucumis sativus), and green gram (Vigna radiata). The influence of S. molesta's vermicompost on some of the physicochemical and biological attributes of the soil was also studied. FT-IR analysis revealed that S. molesta loses its allelopathy, as the chemical compounds that are responsible for it are largely destroyed, in the course of its vermicomposting. There is also an indication that a portion of lignin content of S. molesta is degraded. Vermicompost enhanced the germination success and promoted the morphological growth and biochemical content of the plant species studied. It also bestowed plant friendly physicochemical and biological attributes to the soil. The findings raise the prospect that billions of tons of S. molesta biomass-which not only goes to waste at present but is also a cause of serious harm to the environment-may become utilizable in organic agriculture.

Detoxification of parthenium (Parthenium hysterophorus) and its metamorphosis into an organic fertilizer and biopesticide.

BACKGROUND: Vermicompost of the toxic and allelopathic weed parthenium (Parthenium hysterophorus) was explored for its possible use as an organic fertilizer. Replicated plant growth trials were conducted using four levels of parthenium vermicompost (0, 2.5, 3.75, and 5 t/ha) to assess their effects on the germination, growth, and fruition of a typical food plant ladies finger (Abelmoschus esculentus). Additionally the role of vermicompost in reducing plant pests and disease was evaluated. RESULTS: Vermicompost encouraged the germination and growth of ladies finger at all levels of vermicompost application, with best results obtained in 5 t/ha treatments. The positive impact extended up to the fruit yield. Vermicompost application also improved the quality of fruits in terms of mineral, protein, and carbohydrate contents, and reduced the disease incidence and pest attacks. CONCLUSIONS: The studies establish the fact that parthenium acquires all the qualities of a good organic fertilizer with concomitant loss of its toxic and allelopathic properties after it gets vermicomposted. The findings raise the prospects of economical and eco-friendly utilization of billions of tons of parthenium biomass which is generated annually but goes to waste at present.

Vermicomposting transforms allelopathic parthenium into a benign organic fertilizer.

Vermicompost, which had been derived solely by the action of the epigeic earthworm Eisenia fetida on parthenium (Parthenium hysterophorus), was tested for its impact on the germination and early growth of green gram (Vigna radiata), ladies finger (Abelmoschus esculentus) and cucumber (Cucumis sativus). Seedlings were germinated and grown in soil amended with 0 (control), 0.75, 1.5, 2, 4, 8, 20 and 40% (by weight) parthenium vermicompost. Even though parthenium is known to possess strong negative allelopathy, as also plant/animal toxicity in other forms, its vermicompost (VC) manifested none of these attributes. Rather the VC enhanced germination success, introduced plant-friendly physical features in the container media, increased biomass carbon, and was seen to promote early growth as reflected in several morphological and biochemical characteristics in plants which had received parthenium VC in comparison to those which had not. All these effects were statistically significant. Fourier Transform Infrared (FTIR) Spectrometry revealed that the phenols and the sesquiterpene lactones that are responsible for the negative allelopathic impact of parthenium were largely destroyed in the course of vermicomposting. FTIR spectra also indicated that lignin content of parthenium was reduced during its vermicomposting. The findings open up the possibility that several other invasives known for their negative allelopathy and toxicity may also produce vermicompost which may be plant-friendly and soil-friendly. It also makes it appear possible that the huge quantities of phytomass that is generated annually by parthenium can be gainfully utilized in producing organic fertilizer via vermicomposting, thereby providing a means of exercising some control over parthenium's rampant growth and invasion.

Transformation of toxic and allelopathic lantana into a benign organic fertilizer through vermicomposting.

In a first study of its kind, the composition of vermicompost derived solely from the toxic and allelopathic weed lantana has been investigated using UV-visible and Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric (TG) and differential scanning calorimetry (DSC), gas chromatography-mass spectometry (GC-MS), and scanning electron microscopy (SEM). The studies reveal that a sharp reduction in humification index, substantial mineralization of organic matter and degradation of complex aromatics such as lignin and polyphenols into simpler carbohydrates and lipids occur in the course of vermicomposting. GC-MS analysis shows significant fragmentation, bio-oxidation and molecular rearrangements of chemical compounds in vermicompost in comparison to those in lantana. SEM micrographs of vermicompost reflect strong disaggregation of material compared to the much better formed lantana matrices. The phenols and sesquiterpene lactones which are specifically responsible for the toxicity and allelopathy of lantana are seen to get significantly degraded in the course of vermicomposting - turning it into a plant-friendly organic fertilizer. The study leads to the possibility that the millions of tons of phytomass that is generated annually by lantana can be gainfully utilized in producing organic fertilizer via vermicomposting.