Adsorption mechanisms of chlorobenzenes and trifluralin on primary polyethylene microplastics in the aquatic environment

Remediation of biochar-supported effective microorganisms and microplastics on multiple forms of heavy metals in eutrophic lake

In mineral-rich areas, eutrophic lakes are at risk of HMs pollution. However, few papers focused on the repair of HMs in eutrophic environment. Our study analyzed multiple forms of HMs, pore structure and microbial responses in the water-sediment system of eutrophic lake treated with biochar, Effective Microorganisms (EMs) or/and microplastics (MPs). As biochar provided an ideal carrier for EMs, the remediation of biochar-supported EMs (BE) achieved the greatest repairment that improved the bacterial indexes and greatly decreased the most HMs in various forms across the water-sediment system, and it also reduced metal mobility, bioavailability and ecological risk. The addition of aged MPs (MP) stimulated the microbial activity and significantly reduced the HMs levels in different forms due to the adsorption of biofilms/EPS adhered on MPs, but it increased metals mobility and ecological risks. The strong adsorption and high mobility of aged MPs would increase enrichment of HMs and cause serious ecological hazards. The incorporation of BE and MP (MBE) also greatly reduced the HMs in full forms, which was primarily ascribed to the adsorption of superfluous biofilms/EPS, but it distinctly depressed the microbial activity. The single addition of biochar and EMs resulted in the inability of HMs to be adsorbed due to the preferentially adsorption of dissolved nutrients and the absence of effective carrier, respectively. In the remediation cases, the remarkable removal of HMs was principally accomplished by the adsorption of HMs with molecular weight below 100 kDa, especially 3 kDa ∼100 kDa, which had higher specific surfaces and abundant active matters, resulting in higher adsorption onto biofilms/EPS.

Trojan horse in the intestine: A review on the biotoxicity of microplastics combined environmental contaminants

With the reported ability of microplastics (MPs) to act as "Trojan horses" carrying other environmental contaminants, the focus of researches has shifted from their ubiquitous occurrence to interactive toxicity. In this review, we provided the latest knowledge on the processes and mechanisms of interaction between MPs and co-contaminants (heavy metals, persistent organic pollutants, pathogens, nanomaterials and other contaminants) and discussed the influencing factors (environmental conditions and characteristics of polymer and contaminants) that affect the adsorption/desorption process. In addition, the bio-toxicological outcomes of mixtures are elaborated based on the damaging effects on the intestinal barrier. Our review showed that the interaction processes and toxicological outcomes of mixture are complex and variable, and the intestinal barrier should receive more attention as the first line of defensing against MPs and environmental contaminants invasion. Moreover, we pointed out several knowledge gaps in this new research area and suggested directions for future studies in order to understand the multiple factors involved, such as epidemiological assessment, nanoplastics, mechanisms for toxic alteration and the fate of mixtures after desorption.

Distribution characteristics of microplastics in the soil of mangrove restoration wetland and the effects of microplastics on soil characteristics

The dense vegetation in the wetland could effectively retain microplastic particles, and the distribution of microplastics varied significantly under different planting densities. In addition, microplastics in the soil environment can affect soil properties to a certain extent, which in turn can affect soil functions and biodiversity. In this study, we investigated the distribution of soil microplastics in a mangrove restoration wetland under different planting densities and their effects on wetland soil properties. The results indicated that the average abundance of soil microplastics was 2177.5 n/500 g, of which 70.9% exhibited a diameter ranging from 0.038-0.05 mm, while the remaining soil microplastics accounted for less than 20% of all microplastics, indicating that smaller-diameter microplastics were more likely to accumulate in wetland soil. The microplastic abundance could be ranked based on the planting density as follows: 0.5 × 0.5 m > 1.0 × 0.5 m > 1.0 × 1.0 m > control area. Raman spectroscopy revealed that the predominant microplastic categories in this region included polyethylene terephthalate (PET, 52%), polyethylene (PE, 24%) and polypropylene (PP, 15%). Scanning electron microscopy (SEM) images revealed fractures and tears on the surface of microplastics. EDS energy spectra indicated a large amount of metal elements on the surface of microplastics. Due to the adsorptive features of PET, this substance could influence the soil particle size distribution and thus the soil structure. All physicochemical factors, except for the soil pH, were significantly affected by PET. In addition, the CV analysis results indicated that soils in vegetated areas are more susceptible to PET than are soils in bare ground areas, leading to greater variation in their properties.

Exploring the adsorption behavior of benzotriazoles and benzothiazoles on polyvinyl chloride microplastics in the water environment

As a kind of emerging pollutant, microplastics (MPs) play an important role as a carrier for pollutant migration in the water environment. Carried by the MPs, benzotriazoles, and benzothiazoles (collectively referred to as BTs)¹ are ubiquitous water contaminants. In this paper, the adsorption behavior of BTs on polyvinyl chloride (PVC) MPs was first studied systematically to explain the adsorptive mechanisms and the consequential pollution caused by the absorption-desorption process. The studies on kinetics, isotherms, and thermodynamics revealed that the adsorption of BTs on PVC MPs was a multi-rate, heterogeneous multi-layer, and exothermic process, which was affected by external diffusion, intra-particle diffusion, and dynamic equilibrium. The factors including pH, salinity, and particle size also influenced the adsorption process. In the multi-solute system, competitive adsorption would occur between different BTs. The desorption of BTs from PVC MPs was positively associated with the increase of adsorption amount. Based on the results, the adsorption mechanisms of PVC MPs were clarified, involving hydrophobic interaction, electrostatic force, and non-covalent bonds. It was demonstrated that BTs in the water environment could most probably be accumulated and migrated through MPs, and eventually carried into organisms, posing an increased risk to the ecological environment.

Microplastic Pollution Focused on Sources, Distribution, Contaminant Interactions, Analytical Methods, and Wastewater Removal Strategies: A Review

Plastics have been one of the most useful materials in the world, due to their distinguishing characteristics: light weight, strength, flexibility, and good durability. In recent years, the growing consumption of plastics in industries and domestic applications has revealed a serious problem in plastic waste treatments. Pollution by microplastics has been recognized as a serious threat since it may contaminate all ecosystems, including oceans, terrestrial compartments, and the atmosphere. This micropollutant is spread in all types of environments and is serving as a “minor but efficient” vector for carrier contaminants such as pesticides, pharmaceuticals, metals, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). The need to deeply study and update the evolution of microplastic sources, toxicology, extraction and analysis, and behavior is imperative. This review presents an actual state of microplastics, addressing their presence in the environment, the toxicological effects and the need to understand their extent, their interactions with toxic pollutants, the problems that arise in the definition of analytical methods, and the possible alternatives of treatments.

Sorption/Desorption and Kinetics of Atrazine, Chlorfenvinphos, Endosulfan Sulfate and Trifluralin on Agro-Industrial and Composted Organic Wastes

The use of pesticides presents a risk to terrestrial and aquatic ecosystems. For this reason, the development of strategies to prevent and restore pollution is of the greatest interest, including the adsorption to organic matter. The aim of the present study was to investigate the sorption/desorption and kinetics of atrazine, chlorfenvinphos, endosulfan sulfate, and trifluralin onto several raw organic wastes by batch experiments. Three kinetic models were used to fit the obtained sorption kinetics data and two to fit the obtained adsorption isotherm data; both the Freundlich and pseudo-second-order kinetic models described the sorption isotherms well. The desorption study revealed hysteresis in all cases, showing strong, and not completely reversible, adsorption in most cases, with the exception of atrazine-sawdust and chlorfenvinphos-sawdust and chicken manure combinations, for which responses were weak and irreversible. The best kinetic, adsorption and desorption constants were achieved for the hydrophobic pesticides. With respect to sorption-desorption rates, orujillo was found to be the best adsorbent for atrazine, while composted urban solid waste was more suitable for trifluralin and endosulfan sulfate. Sorption constants and simple correlations indicated that, not only the organic matter content, but also the nature of the organic matter itself, and the pesticide and adsorbent properties, determine pesticide sorption-desorption. The use of wastes as efficient and cheap adsorbents for reducing the risk of pesticide pollution is proposed.

Revisiting pesticide pollution: The case of fluorinated pesticides

Fluorinated pesticides acquired a significant market share in the agrochemical sector due to the surge of new fluoroorganic ingredients approved in the last two decades. This growing trend has not been accompanied by a comprehensive scientific and regulatory framework entailing all their potential negative impacts for the environment, especially when considering the hazardous properties that may result from the incorporation of fluorine into organic molecules. This review aims to address the safe/hazardous dichotomy associated with fluorinated pesticides by providing an updated outlook on their relevancy in the agrochemical sector and how it leads to their role as environmental pollutants. Specifically, the environmental fate and distribution of these pesticides in the ecosystems is discussed, while also analysing their potential to act as toxic substances for non-target organisms.