Major factors dominating the fate of dibutyl phthalate in agricultural soils

High-throughput screening of acetals/ketals in edible essences via GC-Orbitrap-MS and their formation rates at room temperature

Flavors contain active aldehydes and ketones that react with glycerol and propylene glycol to form acetals and ketals. The identification of acetals and ketals is challenging due to the incomplete information in mass spectral libraries. This study examines the reaction kinetics of 36 aldehydes and ketones with propylene glycol and glycerol, and establishes a high sensitivity and throughput screening method for 185 acetals and ketals using GC-Orbitrap-MS. Formation rates of acetals and ketals at room temperature, and influencing factors like steric hindrance, boiling point, and molecular size were explored. A high-resolution mass spectrometry database was established through model reactions and 10 market-purchased edible essences were analyzed. The analysis of edible essences showed that the detected analytes closely correspond to aldehyde and ketone species prone to hydroxyl-aldehyde condensation reactions at room temperature. This method offers high sensitivity, throughput, and accuracy for rapid screening of acetals and ketals in essences.

Predicting bioavailable barium transfer in soil-bok choy systems: A study induced by shale gas extraction in Chongqing, China

Barium (Ba) is a significant contaminant from shale gas extraction and is also used in various other industries. However, there has been very limited attention paid to Ba. Elucidating the Ba in soil-crop system are of great significance for both human health risk assessment and pollution control. In this study, the bioavailability of Ba in soils was studied by using various characterization methods. Then the major factors dominating the transfer of Ba in soil-bok choy system and a suitable predicted model was derived. The results showed that Ba was mainly accumulated in the roots (transfer factor < 0.3). The relationships between Ba in shoots and the bioavailability of Ba characterizing with different methods increased in the order of CH3COOH (R2 = 0.81) < ethylenediamine tetraacetic acid (R2 = 0.87) < pore water (R2 = 0.89) < diffusive gradients in thin film (R2 = 0.90) < CaCl2 (R2 = 0.91). The major soil properties affecting Ba in shoots were pH (r = -0.32, P > 0.05), cation exchange capacity (r = -0.43, P < 0.01) and labile Al (r = 0.38, P < 0.05). Bioavailability of Ba can preferably model the Ba transfer in soil-bok choy system. The best reliable model was LogBa[shoot] = 0.591LogBa[soil-Pore water] + 1.749 (R2 = 0.963, P < 0.001). This model without measuring soil physicochemical properties, making it easier and more convenient to use in practice. Overall, these results highlight the role of metal bioavailability in predicting their transfer in soil-plant systems.

Diethyl phthalate and dibutyl phthalate disrupt sirtuins expression in the HepG2 cells

Background

Phthalates are additives used as plasticizers among other uses, classified as endocrine disruptors and may contribute to some metabolic disorders. The aim of this work was to determine the effect of the exposure of diethyl phthalate (DEP) and dibutyl phthalate (DBP) on cell viability and reactive oxygen species (ROS) production, as well as the regulation of sirloins in HepG2 cells.

Methods

HepG2 cells were exposed to DEP or DBP at 0.1, 1, 10 and 100 μg/mL, and after 48 or 72 h the gene and protein expression of sirtuins was quantified by qRT-PCR and Western-Blot, respectively.

Results

Results showed that even at a low concentration of 0.1 μg/mL DEP affected the expression of Sirt3 and Sirt4, whereas DBP at 0.1 μg/mL affected Sirt3 and Sirt5 gene expression. Protein analysis showed a reduction in Sirt1 levels at a DEP concentration of 1 μg/mL and higher, while DBP at higher dose (100 μg/mL) decreased Sirt3 protein levels. Cell viability decreased by 20% only at higher dose (100 μg/mL) and ROS production increased at 10 and 100 μg/mL for both phthalates.

Conclusion

These findings indicate that exposure to low concentrations (0.1 μg/mL) of DEP or DBP can negatively influence the expression of some sirtuins.

Exploring additives beyond phthalates: Release from plastic mulching films, biodegradation and occurrence in agricultural soils

It is widely recognized that applications of plastic films result in plastic pollution in agroecosystems. However, there is limited knowledge on the release and occurrence of additives beyond phthalates in agricultural soil. In this study, the rates of release and biodegradation of various additives, including phthalates, bisphenols, organophosphate esters, phenolic antioxidants, and ultraviolet absorbents from mulching films in soil were quantified by laboratory incubation. The rates of release and biodegradation ranged from 0.069 d-1 to 5.893 d-1 and from 1.43 × 10-3 d-1 to 0.600 d-1, respectively. Both of these rates were affected by temperature, flooding, and the properties of additives, films, and soils. An estimated 4000 metric tons of these additives were released into soil annually in China exclusively. The total concentrations of these additives in 80 agricultural soils varied between 228 and 3455 μg kg-1, with phenolic antioxidants, phthalates, and bisphenols accounting for 54.1%, 25.2%, and 17.9% of the total concentrations, respectively. A preliminary risk assessment suggested that the current levels of these additives could potentially present moderate hazards to the soil ecosystem.

Ultrasensitive, Label-Free Voltammetric Detection of Dibutyl Phthalate Based on Poly-l-lysine/poly(3,4-ethylenedioxythiophene)-porous Graphene Nanocomposite and Molecularly Imprinted Polymers

Development of an efficient technique for accurate and sensitive dibutyl phthalate (DBP) determination is crucial for food safety and environment protection. An ultrasensitive molecularly imprinted polymers (MIP) voltammetric sensor was herein engineered for the specific determination of DBP using poly-l-lysine/poly(3,4-ethylenedioxythiophene)/porous graphene nanocomposite (PLL/PEDOT-PG) and poly(o-phenylenediamine)-imprinted film as a label-free and sensing platform. Fabrication of PEDOT-PG nanocomposites was achieved through a simple liquid-liquid interfacial polymerization. Subsequently, poly-l-lysine (PLL) functionalization was employed to enhance the dispersibility and stability of the prepared PEDOT-PG, as well as promote its adhesion on the sensor surface. In the presence of DBP, the imprinted poly(o-phenylenediamine) film was formed on the surface of PLL/PEDOT-PG. Investigation of the physical properties and electrochemical behavior of the MIP/PLL/PEDOT-PG indicates that the incorporation of PG into PEDOT, with PLL uniformly wrapping its surface, significantly enhanced conductivity, carrier mobility, stability, and provided a larger surface area for specific recognition sites. Under optimal experimental conditions, the electrochemical response exhibited a linear relationship with a logarithm of DBP concentration within the range of 1 fM to 5 µM, with the detection limit as low as 0.88 fM. The method demonstrated exceptional stability and repeatability and has been successfully applied to quantify DBP in plastic packaging materials.

Altered gut microbiota community structure and correlated immune system changes in dibutyl phthalate exposed mice

Di-n-butyl phthalate (DBP) is a ubiquitous environmental contaminant linked with various adverse health effects, including immune system dysfunction. Gut microbial dysbiosis can contribute to a wide range of pathogenesis, particularly immune disease. Here, we investigated the impact of DBP on the gut microbiome and examined correlations with immune system changes after five weeks oral exposure (10 or 100 mg/kg/day) in adult male mice. The fecal microbiome composition was characterized using 16S rRNA sequencing. DBP-treated mice displayed a significantly distinct microbial community composition, indicated by Bray-Curtis distance. Numerous amplicon sequence variants (ASVs) at the genus level were altered. Compared to the vehicle control group, the 10 mg/kg/day DBP group had 63 more abundant and 65 less abundant ASVs, while 60 ASVs were increased and 76 ASVs were decreased in the 100 mg/kg/day DBP group. Both DBP treatment groups showed higher abundances of ASVs assigned to Desulfovibrio (Proteobacteria phylum) and Enterorhabdus genera, while ASVs belonging to Parabacteroides, Lachnospiraceae UCG-006 and Lachnoclostridium were less common compared to the control group. Interestingly, an ASV belonging to Rumniniclostridium 6, which was less abundant in DBP-treated mice, demonstrated a negative correlation with the increased number of non-classical monocytes observed in the blood of DBP-treated animals. In addition, an ASV from Lachnospiraceae UCG-001, which was more abundant in the DBP-treated animals, showed a positive correlation with the non-classical monocyte increase. This study shows that DBP exposure greatly modifies the gut bacterial microbiome and indicates a potential contribution of microbial dysbiosis to DBP-induced immune system impairment, illustrating the importance of investigating how interactions between exposome components can affect health.

Leaching of phthalate acid esters from plastic mulch films and their degradation in response to UV irradiation and contrasting soil conditions

Phthalate acid esters (PAEs) are commonly used plastic additives, not chemically bound to the plastic that migrate into surrounding environments, posing a threat to environmental and human health. Dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) are two common PAEs found in agricultural soils, where degradation is attributed to microbial decomposition. Yet the impact of the plastic matrix on PAE degradation rates is poorly understood. Using ¹⁴C-labelled DBP and DEHP we show that migration from the plastic matrix into soil represents a key rate limiting step in their bioavailability and subsequent degradation. Incorporating PAEs into plastic film decreased their degradation in soil, DBP (DEHP) from 79% to 21% (9% to <1%), over four months when compared to direct application of PAEs. Mimicking surface soil conditions, we demonstrated that exposure to ultraviolet radiation accelerated PAE mineralisation twofold. Turnover of PAE was promoted by the addition of biosolids, while the presence of plants and other organic residues failed to promote degradation. We conclude that PAEs persist in soil for longer than previously thought due to physical trapping within the plastic matrix, suggesting PAEs released from plastics over very long time periods lead to increasing levels of contamination.

Isolation, characterization and application of the epoxiconazole-degrading strain Pseudomonas sp. F1 in a soil-vegetable system

Epoxiconazole (EPX) has a long half-life in soil and causes various toxicological effects in both the ecosystem and mammals. In this study, eight strains of bacteria capable of degrading EPX were isolated from pesticide-contaminated soil, with strain F1 showing the best effect. This strain was identified as Pseudomonas sp. by 16S rRNA gene sequencing and physiological-biochemical analyses. Our results indicated that strain F1 has a high capacity to degrade EPX, removing 92.1% of EPX within 6 days. The temperature and pH were the two most important environmental factors affecting EPX degradation, followed by substrate concentration and inoculum dose. In addition, strain F1 has a high capacity to promote EPX degradation in soils, with a lower t_1/2 value (2.64 d) in F1-inoculated soil compared to the control (t_1/2 = 96.3 d) without strain F1. The strain could efficiently colonize rhizosphere soil and enhance degradation of EPX, leading to a significant decrease in the accumulation and translocation of EPX in vegetables, thereby alleviating the effects of EPX-induced stress on plants. Moreover, we observed that strain F1-gfp was able to colonize the roots, stems and leaves of Brassica rapa var. chinensis. Such colonization may play a role in the efficient degradation of EPX within plants. To our knowledge, this is the first study to demonstrate biodegradation of EPX in a soil-vegetable system using an EPX-degrading bacterium. This study indicates that strain F1 is a promising candidate for simultaneous bioremediation of soil contaminated with EPX and safe food production.

Interference between di(2-ethylhexyl) phthalate and heavy metals (Cd and Cu) in a Mollisol during aging and mobilization

Diffuse pollution of the soil by phthalates and heavy metals causes numerous concerns. Their respective fates when coexisting require further investigation. In this study, di(2-ethylhexyl) phthalate (DEHP) and Cd/Cu were used as subjects, focusing on their behavior in Mollisols under combined pollution based on their concentration, fractionation, and leaching. The results indicated that when the two pollutants coexist, the dissipation rate of DEHP in the soil decreased, and its half-life was extended from 30.81 to 40.53 (Cd) and 35.40 d (Cu). DEHP altered the distribution of Cd and Cu in the soil, and this effect persisted after most of the DEHP had degraded. Leaching tests showed that the interaction of DEHP with Cd and Cu hindered leaching during the first rainfall event, but as DEHP degraded and Cd/Cu stabilized, the trapped pollutants were gradually released in subsequent rainfall events. Additionally, to investigate the partitioning of pollutants between soil water and solid surfaces, a diffusion model of DEHP and metal ions on the surface of montmorillonite (high specific surface area adsorbents abundant in soils) was built using molecular dynamics simulations. Simulations revealed their density distribution on the clay surface increased synergistically, whereas their diffusion was antagonistic. This study provides basic data and theoretical support concerning the ecological risk assessment of combined phthalate and heavy metals pollution in soil.

Di(2-ethylhexyl) phthalate and dibutyl phthalate have a negative competitive effect on the nitrification of black soil

Di (2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) are the most widely used plasticizers for agricultural mulching films and one of the most common organic pollutants in black soil. However, little is known about the effect of these two contaminants on nitrification in black soil. This study investigated the changes of 20 mg/kg DEHP and DBP on the diversity of nitrification microbial communities, the abundance of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) related genes, and the activities of key enzymes involved in nitrification. During ammonia oxidation, DEHP and DBP had uncompetitive inhibition of urease, reducing the copy number of amoA gene, and microorganisms (Azoarcus, Streptomyces and Caulobacter) would use inorganic nitrogen as a nitrogen source for physiological growth. During nitrite oxidation, the copy number of nxrA gene also reduced, and the relative abundance of chemoautotrophic nitrifying bacteria (Nitrosomonas and Nitrobacter) decreased. Moreover, the path analysis results showed that DEHP and DBP mainly directly or indirectly affect AOB and NOB through three ways. These results help better understand the ecotoxicological effects of DEHP and DBP on AOB and NOB in black soil.

Prediction of phthalate acid esters degradation in soil using QSAR model: A combined consideration of soil properties and quantum chemical parameters

Phthalic acid esters (PAEs) are predominant hazardous substances and endocrine-disrupting compounds to be controlled in soil. The degradation behaviors of PAEs in soil had been long term concerned. Thus, the degradation rate (K) is important for assessing theexposure risk and is of great significance in evaluating the ecological risk of PAEs in soil environment. But by far, quantitative structure activity relationship (QSAR) models for PAEs degradation have rarely been considered in soil environment. In this study, quantum chemical parameters were considered along with soil properties as two kinds of descriptors in QSAR model. A total of 32 logk of PAEs were collected from reference and experiment. Degradation kinetics in soils were determined by pseudo-first order kinetic models. The residual concentration of PAEs in Udic ferrosols and Aquic cambisols suggesting a potential expose risks of PAEs to ecosystem in soil. The QSAR model between logk and quantum chemical parameters revealed that E_HOMO and qC- are two predominant factors in determining logk value. Furthermore,our study further indicated that soil organic matter (SOM) as new predictor contributes more to predict logk values of PAEs during degradation process than pH. Results from this study make a new contribution for methods to predict the degradation of PAEs in soil environment and highlight the potential to evaluate the environmental risks of degradation of PAEs.

Effect of plastic film mulching and film residues on phthalate esters concentrations in soil and plants, and its risk assessment

The application of plastic film mulching can greatly improve dryland productivity, while the release of toxic phthalate esters (PAEs) from the plastic film has generated concern. This study investigated the effects of mulched plastic film and residual plastic film on the PAE concentrations in the soil-crop system and assessed the risks to people eating crop products. The PAEs concentration in the 0-25 cm soil layer of plastic mulched farmland was 0.45-0.81 mg/kg, while the average PAEs concentration of 0.37-0.73 mg/kg in non-mulched farmland decreased by 19%. The PAEs concentration in mulched soil reached the highest in July, being 0.80-0.84 mg/kg, while in the non-mulched soil, the PAEs also appeared and gradually decreased from May at 0.62-0.74 mg/kg to October, and the PAEs concentrations were almost the same in the mulched and non-mulched soils at the harvest time in October at 0.37-0.44 mg/kg. With the amounts of residual film in farmland increasing from 0 kg/ha to 2700 kg/ha (equivalent to the total amount of residual film after 60 years of continuous plastic film mulching), the PAEs concentrations were no significant changes, being 0.54-0.93 mg/kg. Maize (Zea mays L.) roots could absorb and accumulate PAEs, and the bio-concentration factor (BCF) was 1.6-2.3, and the average PAEs concentrations in stems, leaves, and grains were 79%-80% of those in roots at 0.77-1.47 mg/kg. For the ingestion of maize grains or potato (Solanum tuberosum L.) tubers grown in plastic film mulched farmland or farmland containing residual film of 450-2700 kg/ha, the hazard index (HI) were less than 1, the carcinogenic risks (CRs) were 2.5 × 10^-7-2.2 × 10^-6, and the estrogenic equivalences were 6.17-17.73 ng E₂/kg. This study provides important data for the risk management of PAEs in farmlands.

Accumulation and transport patterns of six phthalic acid esters (PAEs) in two leafy vegetables under hydroponic conditions

In this study, we investigated the accumulation and transport patterns of six phthalic acid esters (PAEs) in two leafy vegetables under hydroponic conditions. The tested PAEs included dibutyl phthalate (DBP), diethyl phthalate (DEP), diallyl phthalate (DAP), diisobutyl phthalate (DIBP), dimethyl phthalate (DMP) and benzyl butyl phthalate (BBP), and the tested vegetables included Gaogengbai and Ziyoucai. The results revealed that the six PAEs were taken up by vegetables from the solution, although their accumulation and distribution varied among PAEs. The ability of concentrating PAEs into the roots followed the order of BBP > DBP > DIBP > DAP > DEP > DMP, whereas the ability of concentrating PAEs in plant shoots had the opposite order. By analysing the fractionation of the six PAEs in vegetable roots, DMP had the largest proportion in terms of apoplastic movement, while BBP had the largest proportion in terms of symplastic movement. Correlation analyses revealed that the differences among the accumulation and distribution behaviours of the six PAEs in plant tissues were not only related to their physicochemical parameters, such as alkyl chain length and the octanol/water partition coefficient (logK_ow), but also related to the proportion of apoplastic and symplastic movement in the plant roots. In addition, PAEs were more readily accumulated in the Gaogengbai roots than in the Ziyoucai roots; however, the opposite trend was observed for the shoots.