Fate of four phthalate esters with presence of Karenia brevis: Uptake and biodegradation

Contamination levels and ecological risk assessment of phthalate esters (PAEs) in the aquatic environment of Chaohu Lake

Phthalate esters (PAEs), widely recognized as synthetic organic compounds with extensive production and utilization, are known to disrupt physiological processes in both animals and humans, even at low environmental concentrations. This study investigated the occurrence, distribution, and potential ecological risk of five representative PAEs (DMP, Dimethyl phthalate; DEP, Diethyl phthalate; DBP, Dibutyl phthalate; DiBP, Diisobutyl phthalate; DEHP, Bis(2-ethylhexyl) phthalate) in a typical lake (Chaohu Lake, China). It was found that PAEs were detected in both the aqueous (1.09-6.402 µg/L) and solid phases (0.827-6.602 µg/g) of Chaohu Lake. Notably, DiBP and DBP were the predominant PAEs in the water, and DiBP and DEHP were the most prevalent in the sediments. The concentrations of PAEs exhibited significant seasonal variations in the aqueous phases, with total PAEs in summer being nearly twice those in winter. Toxicity assessments revealed that DEHP, DBP, and DiBP posed high risks to the survival of three indicator organisms (algae, Daphnia, and fish) in the aqueous phase. In the solid phase, the exceeding rate of DiBP was as high as 92.9%. On the other hand, DBP and DEHP generally presenting moderate risk, although some sites were identified as high-risk. This study's analysis of PAEs concentrations in Chaohu Lake reveals a discernible increasing trend when compared with historical data. These findings underscore the urgent need for interventions to mitigate the ecological threats posed by PAEs in Chaohu Lake.

Phthalate acid esters: A review of aquatic environmental occurrence and their interactions with plants

The increasing use of phthalate acid esters (PAEs) in various applications has inevitably led to their widespread presence in the aquatic environment. This presents a considerable threat to plants. However, the interactions between PAEs and plants in the aquatic environment have not yet been comprehensively reviewed. In this review, the properties, occurrence, uptake, transformation, and toxic effects of PAEs on plants in the aquatic environment are summarized. PAEs have been prevalently detected in the aquatic environment, including surface water, groundwater, seawater, and sediment, with concentrations ranging from the ng/L or ng/kg to the mg/L or mg/kg range. PAEs in the aquatic environment can be uptake, translocated, and metabolized by plants. Exposure to PAEs induces multiple adverse effects in aquatic plants, including growth perturbation, structural damage, disruption of photosynthesis, oxidative damage, and potential genotoxicity. High-throughput omics techniques further reveal the underlying toxicity molecular mechanisms of how PAEs disrupt plants on the transcription, protein, and metabolism levels. Finally, this review proposes that future studies should evaluate the interactions between plants and PAEs with a focus on long-term exposure to environmental PAE concentrations, the effects of PAE alternatives, and human health risks via the intake of plant-based foods.

Comparison of phthalate esters (PAEs) in freshwater and marine food webs: Occurrence, bioaccumulation, and trophodynamics

Phthalate esters (PAEs) have received widespread attentions due to their ubiquity in various kinds of matrices and potential biotoxicity. This study systematically compared the concentrations, bioaccumulation, trophodynamics and health risk of PAEs in 25 species (n = 225) collected from a marine (Bohai Bay, BHB) and freshwater environment (Songhua River, SHR), China. Results showed that di-(2-ethylhexyl) phthalate and di-n-butyl phthalate were the predominant PAEs in the organisms from the two aquatic environments. The total concentrations of 6 PAEs in algae and fish from SHR were significantly higher than those from BHB. Two food webs were constructed in BHB and SHR based on the abundance of 15N in the organisms. All the PAEs except dimethyl phthalate exhibited trophic dilution with the trophic magnification factors less than 1. Moreover, an obvious biodilution of PAEs was observed in marine food web compared to freshwater food web. A low health risk of PAEs was found in organisms from both BHB and SHR. However, di-(2-ethylhexyl) phthalate exhibited a potential carcinogenic risk by consumption of some benthos in BHB and fish in SHR. This study provides a valuable perspective for understanding the trophodynamics and health risk of PAEs in marine and freshwater environments.

Comparing the removal efficiency of diisobutyl phthalate by Bacillariophyta, Cyanophyta and Chlorophyta

The utilization of microalgae for both removing phthalate esters (PAEs) from wastewater and producing bioenergy has become a popular research topic. However, there is a lack of studies comparing the effectiveness of different types of microalgae in removing these harmful compounds. Therefore, the present study aimed to evaluate and compare the efficiency of various processes, such as hydrolysis, photolysis, adsorption, and biodegradation, in removing diisobutyl phthalate (DiBP) using six different species of microalgae. The study indicated that the average removal efficiency of DiBP (initial concentrations of 5, 0.5, and 0.05 mg L-1) by all six microalgae (initial cell density of 1 × 106 cells mL-1) was in the order of Scenedesmus obliquus (95.39 %) > Chlorella vulgaris (94.78 %) > Chroococcus sp. (91.16 %) > Cyclotella sp. (89.32 %) > Nitzschia sp. (88.38 %) > Nostoc sp. (84.33 %). The results of both hydrolysis and photolysis experiments revealed that the removal of DiBP had minimal impact, with respective removal efficiencies of only 0.89 % and 1.82 %. The adsorption efficiency of all six microalgae decreased significantly with increasing initial DiBP concentrations, while the biodegradation efficiency was elevated. Chlorella vulgaris and Chroococcus sp. demonstrated the highest adsorption and biodegradation efficiencies among the microalgae tested. Scenedesmus obliquus was chosen for the analysis of the degradation products of DiBP due to its exceptional ability to remove DiBP. The analysis yielded valuable results, identifying monoisobutyl phthalate (MiBP), phthalic acid (PA), and salicylic acid (SA) as the possible degradation products of DiBP. The possible degradation pathways mainly included dealkylation, the addition of hydroxyl groups, and decarboxylation. This study lays a theoretical foundation for the elimination of PAEs in the aquatic environment.

Comparative analysis of the effects of conventional and biodegradable plastic mulching films on soil-peanut ecology and soil pollution

In agricultural production, biodegradable plastic mulching film (Bio-PMF) has the potential to replace conventional plastic mulching film (CPMF) due to its degradability, but their impacts on soil-crop ecology are controversial. In this study, from 2019 to 2021, effects of CPMF and Bio-PMF on the soil-crop ecology and soil pollution were evaluated on a peanut farm. Compared to the Bio-PMF, an overall improvement in the soil-peanut ecology under the CPMF was observed, including an increase of 10.77 ± 4.8% in peanut yield, an amelioration of four soil physicochemical properties (total P and available P in the flowering stage, total P and temperature in the mature stage), an increase of rhizobacterial relative abundances in class level (Bacteroidia, Blastocatellia, Thermoleophilia and Vicinamibacteria in the flowering stage, Nitrospira and Bacilli in the mature stage) and genus level (RB41 and Bacillus in the flowering stage, Bacillus and Dongia in the mature stage), and an enhancement of soil nitrogen metabolism abilities (ureolysis, nitrification and aerobic ammonia in the flowering stage, nitrate reduction and nitrite ammonification in the mature stage). These preserved soil nutrients and temperature, reshaped rhizobacterial communities, and enhanced soil nitrogen metabolism abilities in the mature stage were obviously correlated with peanut yield under CPMF. However, such remarkable relations were not existed under Bio-PMF. In addition, compared with Bio-PMF, CPMF significantly increased the contents of dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP) and microplastics (MPs) in soil by 79.93, 44.55, 138.72 and 14.1%, respectively. Thus, CPMF improved soil-peanut ecology and caused serious soil pollution, while Bio-PMF introduced little pollutants into the soil and had little impact on soil-peanut ecology. Based on these, the degradation ability of CPMF or the ecological improvement capacity of Bio-PMF should be improved to obtain the environmentally and soil-crop ecology friendly plastic film in the future.

Alterations in the conformation and function of human serum albumin induced by the binding of methyl hydrogen phthalate

Phthalate esters (PAEs) are widely used as plasticizer components in production. Methyl hydrogen phthalate (MHP) is a metabolite of dimethyl phthalate (DMP, a kind of PAEs), and its toxic residues accumulate in the nature and can enter the human body. Here, the interaction between MHP and human serum albumin (HSA) was probed by using multi-spectral, computer simulations, and biochemical techniques. The results showed that MHP was spontaneously embedded in site I of HSA to form a complex by H-bonds and van der Waals forces (ΔH < 0, ΔS < 0). The binding constant (K_a) of the HSA-MHP system was 1.136 ± 0.026 × 10⁴ M^-1 (298 K). The combination of MHP produced conformational variations of HSA, as shown by the 3D fluorescence spectrum, CD spectra, and molecular dynamics simulation. Additionally, molecular docking indicated that MHP was surrounded by multiple residues, such as Lys199, Leu203, Phe206, and Trp214. Specifically, Lys199 and Trp214 exerted a crucial effect on the interaction of HSA and MHP. The residues with important energy contribution were mostly located in site I. The ASA values of the aromatic amino acids of HSA changed after combining with MHP. The R_g and SASA values of HSA increased after adding MHP, suggesting that the structure of HSA was less compact. Moreover, the esterase-like activity of HSA increased after adding MHP to HSA, indicating that MHP may disturb the normal physiological activities in the human body. This study was helpful to understand the biological function of MHP and provided some insights for its side effect in the human body.

Occurrence and cross-interface transfer of phthalate esters in the mangrove wetland in Dongzhai Harbor, China

Phthalate esters (PAEs), the most widely used plasticizers, are extensively present in various environmental media, and are continuously transported from land to sea. However, PAEs have not been well characterized in multiple media in mangrove wetlands, an important land-sea interface. This study investigated the distribution and transfer of six PAEs in water, sediment, mangroves, and fish in Dongzhai Harbor. The mangrove forest in Dongzhai Harbor is the largest in China and is surrounded by shrimp ponds and villages. PAEs are ubiquitous in the study area. The mean concentration range of ∑₆PAEs was 0.31-1.52 μg/L in water, 450-2096 μg/kg dry weight (dw) in sediment, 210-937 μg/kg dw in mangrove plants, and not detected (n.d.) -205 μg/kg in fish. Among the six PAEs, di-n-butyl phthalate (DBP) and di-ethylhexyl phthalate (DEHP) were predominant. The concentrations of the PAEs in mangrove plants tended to decrease from the river and coast to tidal gullies, which might be related to the periodic inundation of tides. A study of PAEs bioaccumulation showed that the concentration of PAEs in herbivorous fish was higher than that in carnivorous fish. In the same species, larger individuals had a lower concentration of ∑₆PAEs. Di-n-octyl phthalate (DnOP) and DEHP tended to transfer from water to sediments, while the four less-hydrophobic PAEs, such as DBP, were more likely to be released from sediments to water. Our results can provide important information of the distribution and fate of PAEs in mangrove wetlands.

Biodegradable and re-usable sponge materials made from chitin for efficient removal of microplastics

Microplastics have attracted widespread attention due to their detrimental effects on organisms, and their efficient removal poses great challenges, especially those smaller than 3 µm that are more harmful for aquatic biota. Herein, the chitin based sponges with interconnected pores, excellent elasticity and mechanical durability were fabricated and composed with graphene oxide (GO) and oxygen-doped carbon nitride (O-C₃N₄). The chitin based sponges could effectively remove different functionalized microplastics (~1 µm) at pH 6-8, including carboxylate-modified polystyrene (PS-COOH), amine-modified polystyrene (PS-NH₂), and polystyrene (PS). Notably, the removal efficiency of three microplastics by the chitin based sponges reached up to 71.6-92.1% at an environmentally relevant concentration of 1 mg L^-1 in water system. The potential driving forces of the adsorption were electrostatic interactions, hydrogen bond interactions, and π-π interactions. In addition, the chitin based sponges are reusable and after re-used for 3 cycles due to their excellent compressibility. The algae toxicity test demonstrated good biocompatibility of the chitin based sponges and they are also biodegradable in a natural soil. This study provides a green and promising method for fabricating environmentally friendly adsorbents for small-size microplastics removal, and expands the insights into the mechanisms of microplastic adsorption onto the sponge materials.

Seasonal distribution and ecological risk of phthalate esters in surface water and marine organisms of the Bohai Sea

The spatiotemporal variability and ecological risks related to 16 phthalate esters (PAEs) were investigated in surface water and marine organisms of the Bohai Sea. The average PAE concentrations in the surface water were 8.02, 4.53, and 3.16 μg L^-1 in spring, summer, and winter, respectively. Additionally, suspended particle matter was positive related to PAE content in seawater in spring and winter. The predominant PAEs in both water and biota were dimethyl phthalate (DMP), di-butyl phthalate (DBP), di-isobutyl phthalate (DIBP), and diethylhexyl-phthalate (DEHP). Because they do not exhibit long-distance migratory behavior, Chaeturichthys hexanema, Cynoglossus lighti, and Loligo japonica were good candidate indicator organisms for PAE pollution in Bohai Sea. The risk quotient method revealed that DIBP, DBP, and DEHP posed relatively greater risks to the aquatic system. This research establishes baseline data from which future management strategies to control PAEs in the Bohai Sea can be developed.

Effects of Fe-Mn oxide-modified biochar composite applications on phthalate esters (PAEs) accumulation in wheat grains and grain quality under PAEs-polluted brown soil

Phthalate esters (PAEs), such as dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP), are used extensively as additives and plasticizers, and have become ubiquitous in the environment. PAEs in the soil could have adverse effects on crop plants as well as humans via accumulations in food chain. Thus, it is important to explore strategies to reduce the bioavailability of phthalate esters. We investigated the effects of Fe-Mn oxide-modified biochar composite (FMBC) applications on the quality of wheat grown in DBP- and DEHP-polluted brown soil. The application of FMBC and biochar (BC) increased the wheat grain biomass by 9.71-223.01% and 5.40-120.15% in the DBP-polluted soil, and 10.52-186.21% and 4.50-99.53% in the DEHP-spiked soil in comparison to the controls. All FMBC treatments were better than the BC treatments, in terms of decreasing DBP and DEHP bioavailability for the wheat grains. The activities of the glutamine synthetase and glutamic-pyruvic transaminase in the flag leaves at the filling stage and of granule-bound starch synthase, soluble starch synthase, and adenosine diphosphate-glucose pyrophosphorylase in the grains at maturity increased significantly with increases in either the BC or FMBC applications. This, in turn, increased the starch, protein, and amino acid content in the wheat grains. Compared with the BC treatment, the FMBC amendment induced only slight increases in the aforementioned factors. This study offers novel insights into potential strategies for decreasing PAEs bioavailability in soil, with potential positive implications for crop quality and environmental health improvements.

Influences of nutritional conditions on degradation of dibutyl phthalate in coastal sediments with Cylindrotheca closterium

In this work, microphytobenthos Cylindrotheca closterium was planted on the surface of coastal sediments to investigate its influence on dibutyl phthalate (DBP) degradation in sediments under different nutritional conditions. The results indicated that C. closterium largely utilized nutrients from the overlying water. Addition of nitrogen, phosphorus or silicon increased algal biomass (as chlorophyll a) by 0.97-3.16, 1.75-2.36 and 1.61-3.09 times, respectively, meanwhile it changed bacterial community structure in sediments with C. closterium. Growth of C. closterium was more sensitive to nitrogen content in the overlying water. Inoculation of C. closterium increased the relative abundances of dominant aerobic bacteria by 10-67%. Compared with treatments without C. closterium, inoculation of C. closterium increased DBP degradation percentage in sediments (8.5-18.9% increment), which was positively correlated with chlorophyll a content. Thus, microphytobenthos showed the potential for improving the cleansing of polluted coastal sediments, which was obviously related to nutritional conditions in the overlying water.

Biotransformation of Phthalate Plasticizers and Bisphenol A by Marine-Derived, Freshwater, and Terrestrial Fungi

Phthalate esters (PEs, Phthalates) are environmentally ubiquitous as a result of their extensive use as plasticizers and additives in diverse consumer products. Considerable concern relates to their reported xenoestrogenicity and consequently, microbial-based attenuation of environmental PE concentrations is of interest to combat harmful downstream effects. Fungal PE catabolism has received less attention than that by bacteria, and particularly fungi dwelling within aquatic environments remain largely overlooked in this respect. We have compared the biocatalytic and biosorptive removal rates of di-n-butyl phthalate (DBP) and diethyl phthalate (DEP), chosen to represent two environmentally prominent PEs of differing structure and hydrophobicity, by marine-, freshwater-, and terrestrial-derived fungal strains. Bisphenol A, both an extensively used plastic additive and prominent environmental xenoestrogen, was included as a reference compound due to its well-documented fungal degradation. Partial pathways of DBP metabolization by the ecophysiologically diverse asco- and basidiomycete strains tested were proposed with the help of UPLC-QTOF-MS analysis. Species specific biochemical reaction steps contributing to DBP metabolism were also observed. The involved reactions include initial cytochrome P450-dependent monohydroxylations of DBP with subsequent further oxidation of related metabolites, de-esterification via either hydrolytic cleavage or cytochrome P450-dependent oxidative O-dealkylation, transesterification, and demethylation steps - finally yielding phthalic acid as a central intermediate in all pathways. Due to the involvement of ecophysiologically and phylogenetically diverse filamentous and yeast-like fungi native to marine, freshwater, and terrestrial habitats the results of this study outline an environmentally ubiquitous pathway for the biocatalytic breakdown of plastic additives. Beyond previous research into fungal PE metabolism which emphasizes hydrolytic de-esterification as the primary catabolic step, a prominent role of cytochrome P450 monooxygenase-catalyzed reactions is established.