Fate and transport modeling of phthalate esters from biosolid amended soil under corn cultivation

The concentrations and behavior of classic phthalates and emerging phthalate alternatives in different environmental matrices and their biological health risks

Because of their excellent plasticity, phthalates or phthalic acid esters (PAEs) are widely used in plastic products. However, due to the recognized toxicity of PAEs and legislative requirements, the production and use of emerging PAE alternatives have rapidly grown, such as di-isononyl cyclohexane-1,2-dicarboxylate (DINCH) and di(2-ethylhexyl) terephthalate (DEHTP) which are the primary replacements for classic PAEs. Nowadays, PAEs and emerging PAE alternatives are frequently found in a variety of environmental media, including the atmosphere, sludge, rivers, and seawater/sediment. PAEs and emerging PAE alternatives are involved in endocrine-disrupting effects, and they affect the reproductive physiology of different species of fish and mammals. Therefore, their presence in the environment is of considerable concern due to their potential effects on ecosystem function and public health. Nevertheless, current research on the prevalence, destiny, and conduct of PAEs in the environment has primarily focused on classic PAEs, with little attention given to emerging PAE alternatives. The present article furnishes a synopsis of the physicochemical characteristics, occurrence, transport, fate, and adverse effects of both classic PAEs and emerging PAE alternatives on organisms in the ecosystem. Our analysis reveals that both classic PAEs and emerging PAE alternatives are widely distributed in all environmental media, with emerging PAE alternatives increasingly replacing classic PAEs. Various pathways can transform and degrade both classic PAEs and emerging PAE alternatives, and their own and related metabolites can have toxic effects on organisms. This research offers a more extensive comprehension of the health hazards associated with classic PAEs and emerging PAE alternatives.

Status of phthalate esters pollution in facility agriculture across China: Spatial distribution, risk assessment, and remediation measures

The pervasive utilization of phthalate esters (PAEs) in plastic products has led to an emergent concern regarding the PAEs contamination in environmental matrices. However, the overall understanding of PAEs pollution in facility agriculture and its relevant risks remain limited. In this paper, the characteristics, health risks, and remediation measures of PAEs pollution in facility agriculture across China were analyzed. In general, PAEs pollution in facility agriculture soil in SWC and vegetables in SC were more serious than that in the other six regions (p < 0.05). The total level of six PAEs ranged from 0.053 to 5.663 mg·kg-1 in soil samples, nd (not detectable) to 12.540 mg·kg-1 in vegetable samples, with mean values of 0.951 mg·kg-1 and 2.458 mg·kg-1, respectively. DEHP and DnBP were dominant in both soil and vegetable samples with a total contribution of over 70 % of the six PAEs, but their concentrations were a little lower in soil samples. The PAEs concentrations of leafy, root, and fruit vegetables exhibited a descending trend. Correlation analysis revealed that the relationships between soil and vegetable PAEs concentrations remained inconclusive, lacking clear correlations. Furthermore, risk assessments indicated that the hazard quotient (HQ) for both total and individual PAEs in the vast majority of vegetable samples remained within acceptable thresholds. Meanwhile, all values for carcinogenic risks (CR) were confined within the range of 10-4. In conclusion, the study outlines remediation measures aimed at precluding and mitigating the environmental risks associated with PAEs exposure. These findings furnish a scientific foundation for the targeted assessment and judicious management of PAEs pollution within facility agriculture landscape of China.

A metal-organic framework regulated graphdiyne-based electrochemiluminescence sensor with a electrocatalytic self-acceleration effect for the detection of di-(2-ethylhexyl) phthalate

In this work, a super-sensitive electrochemiluminescence (ECL) aptamer sensor was constructed using a multiple signal amplification strategy to realize ultra-sensitive detection of di-(2-ethylhexyl) phthalate (DEHP). The incorporation of a highly efficient electrocatalytic metal-organic framework (NH2-Zr-MOF) and graphdiyne (GDY) composite has significantly enhanced the overall electrochemically active surface area, facilitating electron transfer during the entire electrochemical reaction process, and the large number of pores in graphdiyne and NH2-Zr-MOF limited a series of redox reactions within a certain range. This resulted in the generation of a greater number of SO4˙- radicals, thereby boosting the ECL intensity of the GDY in the K2S2O8 system. To increase the performance of the sensor even further, sodium ascorbate (NaAsc) as an accelerator was added to the co-reactant system. Additionally, nitrogen micro-nano bubbles with higher stability and stronger mass transfer have been introduced into the ECL system for the first time. Based on these, the aptamer as the recognition element realized the ultra-sensitive detection of DEHP in the linear range of 1.0 × 10-12 to 1.0 × 10-4 mg mL-1 with the limit of detection (LOD) of 2.43 × 10-13 mg mL-1. In summary, we have utilized the electrocatalytic activity of the porous MOF and the reducing capability of sodium ascorbate to enhance the ECL emission of GDY, which has been successfully applied to the detection of DEHP in water samples.

Effect of biosolids amendment on the fate and mobility of non-steroidal anti-inflammatory drugs (NSAIDs) in a field-based lysimeter cell study

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used globally to treat and prevent illness. Biosolids change physico-chemical characteristics of soil and can affect the mobility of NSAIDs. A field-based lysimeter study evaluated the effect of three rates (0, 7, and 28 Mg ha^-1) of alkaline treated biosolids (ATB) on the leaching potential of naproxen (NPX), ibuprofen (IBF), and ketoprofen (KTF) over 34 days in a sandy loam textured soil. Although all three NSAIDs in the lysimeter cells vertically migrated to deeper soil depths after spiking, the sum of all NPX, IBF, and KTF detected in the leachate samples from all treatments were only 0.03%, 0.02%, and 0.04% of the initial spiking mass to the surface soil, respectively. A mass balance analysis indicated a low accumulation of these compounds in the soil at the end of the study (Day 34) from all treatments with only 4.8%, 0.5%, and 0.7% of initial spiked NPX, IBF, and KTF, respectively. Application of ATB significantly increased soil pH and organic matter (OM) content of the soils but did not impact retention of the compounds in the soil profile. Overall, all three NSAIDs in the present study presented low mobility in the loamy sand textured agricultural soil.

Visualizing the Distribution of Phthalate Esters and Plant Metabolites in Carrot by Matrix-Assisted Laser Desorption/Ionization Imaging Mass Spectrometry

The accumulation of organic pollutants in vegetables is a major global food safety issue. The concentrations of pollutants in vegetables usually differ across different tissues because of different transport and accumulation pathways. However, owing to the limitations of conventional methods, in situ localization of typical organic pollutants such as phthalate esters (PAEs) in plant tissues has not yet been studied. Here, we developed a quick and efficient method for in situ detection and imaging of the spatial distribution of PAEs in a typical root vegetable, carrot, using matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS). The use of a 2,5-dihydroxybenzoic acid matrix with a spray-sublimation coating method led to the successful identification of PAEs ion signals. The IMS results showed that a typical PAE-di-(2-ethylhexyl)phthalate (DEHP) was broadly distributed in the cortex, phloem, and metaxylem, but was barely detectable in the cambium and protoxylem. Interestingly, MALDI-IMS data also revealed for the first time the spatial distribution of sugars and β-carotene in carrots. In summary, the developed method offers a new and practical methodology for the in situ analysis of PAEs and plant metabolites in plant tissues. As a result, it could provide a more intuitive understanding of the movement and transformation of organic pollutants in soil-plant systems.

Effects of fertilizer application on phthalate ester pollution and the soil microbial community in plastic-shed soil on long-term fertilizer experiment

Due to the use of agricultural film, the pollution of phthalate esters (PAEs) in plastic-shed soils has attracted increasing attention. In this study, we used watermelon as a planting system and investigated the effects of organic fertilizer and chemical fertilizer application on the degradation of PAEs by evaluating soil nutrients and soil bacterial communities in plastic-shed soil. The dibutyl phthalate (DBP) concentration in the organic fertilizer soil was only 58.2% in the zero-fertilization control (CK) soil, but the concentrations of monohexyl phthalate (MEHP) and mono-n-butyl ester (MBP), the metabolites of PAEs, were found to be higher. The concentration of MBP is ten times that of DBP. The results showed that fertilization, especially the application of organic fertilizers, had a significant effect on the degradation of PAEs. There were specific biomarkers in different fertilization treatments. Among the microbiome community, Planifilum had the highest relative abundance in the organic fertilizer (OF) soil, and the highest proportion of Thermodesulfovibrionia was detected in the chemical fertilizer (CF) soil. These biomarkers were significantly correlated with PAEs and their metabolites. The relative abundance of Thermomonosporaceae was significantly positively correlated with DBP. Planifilum and Thermaerobacter, which significantly increased in organic fertilizer soil, showed a significant negative correlation with DBP and a significant positive correlation with MBP. The relative abundances of Planifilum and Geobacillus were elevated in the OF soil and may be able to co-metabolize soil nitrogen and PAEs. PAEs and their metabolites in soils had significant effects on soil microbes, as did the soil nutrients including available phosphorus (AP), alkali-hydrolysable nitrogen (Alkali-N), and organic matter (OM). Our research provides scientific support for the use of fertilizers to reduce PAE contamination but also warns of the potential risks of PAE metabolites.

Effects of phthalate esters on soil microbial community under different planting patterns in Northern China: Case study of Hebei Province

Soil microorganisms are biological factors involved in the farmland environment. The factors that shape soil microbial communities and how these are influenced by geographic location, planting pattern (open-field or greenhouse), and soil organic pollutants (phthalate esters, PAEs) remain poorly understood at large scales. Using 16 S rRNA gene and ITS sequencing, we characterized the soil microbiota in open-field and greenhouse soils in Hebei Province, China, and correlated their structure and composition to geographic location, planting pattern and PAEs. Compared with geographic location, planting pattern is more decisive for shaping soil microbes and has more significant effects on bacteria, and the effects are shaped by the number and types of core OTUs. PAEs participated in the shaping of soil microbial communities by altering the relative abundances of dominant microorganisms in the two planting patterns, and the effects of PAEs with high K_ow were more significant. PAEs have a greater impact on bacteria than fungi in both planting patterns. Bacteria in the greenhouse soil were sensitive to the 9 kinds of PAEs detected, however in the open-field samples, mainly responded to PAEs with high K_ow and rarely respond to PAEs with low K_ow. DEHP and DBP, as two monomers with the highest concentration, have significant effects on dominant genera of microorganisms under both planting patterns, with inhibiting effect on bacteria and significantly promotion on fungi. Our study clarified the factors that have a substantial impact on soil microorganisms at the provincial scale and the mechanisms involved in shaping soil microbial community structure, as well as the significant impact of PAEs on soil microbial dominant microorganisms.

Diffuse phthalate acid esters losses induced from large amount of agricultural plastic film residues caused low risks for water quality in China during 1991-2017

Extensive application of agricultural plastic films has resulted in abundant film residues in farmlands. Phthalate acid esters (PAEs) are vital additives of the agricultural plastic film and are easily emitted into soils. However, spatio-temporal variations of diffuse PAEs loss to water bodies have not been explored in China. This study used an integrated estimation framework and high-resolution activity data to conduct a comprehensive inventory of diffuse PAEs loss associated with plastic films of six main crop types in China for 1991-2017. We found that the diffuse PAEs loss induced from agricultural plastic films increased 10.57-46.30 kg over the same time. Di-butyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP) accounted for ~75% of the national total loss. High PAEs loss regions are mainly located in Eastern China, the Middle-Lower Yangtze Plain, and eastern Yunnan and Sichuan provinces. We proved that PAEs emission, agricultural film residues, surface runoff, precipitation, and soil organic carbon explained 19.64%, 17.50%, 15.45%, 12.88%, and 9.83% of the total variation, respectively. The potential ecological risks to the various aquatic species were assessed to be low. Overall, our results are valuable for addressing severe agricultural plastic film residues and associated pollutant emissions and losses in China.

Lycopene prevents DEHP-induced testicular endoplasmic reticulum stress via regulating nuclear xenobiotic receptors and unfolded protein response in mice

Lycopene (LYC) is a potent antioxidant synthesized by red vegetables or plants. Di-2-ethylhexyl phthalate (DEHP) is frequently detected in diverse agricultural environments and considered as a reproductive toxicant. The present research was designed to assess the potential mechanisms of DEHP-induced testicular toxicity and the treatment efficacy of LYC. In this study, after the oral administration of LYC at the dose of 5 mg per kg b.w. per day, mice were given 500 or 1000 mg per kg b.w. per day of DEHP. This research suggested that LYC prevented the DEHP-induced disorder at the levels of activity and content of CYP450 enzymes. LYC attenuated DEHP-caused enhancement in nuclear xenobiotic receptors (NXRs) and the phase I metabolizing enzymes (CYP1, CYP2, CYP3, etc.) levels. Furthermore, endoplasmic reticulum (ER) stress was induced by DEHP and triggered unfolded protein response (UPR). Interestingly, LYC could effectively ameliorate these "hit". The present study suggested that LYC prevents DEHP-induced ER stress in testis via regulating NXRs and UPRER.

Removal of Emerging Pollutants in Horizontal Subsurface Flow and Vertical Flow Pilot-Scale Constructed Wetlands

We assessed constructed wetland (CW) performance in the removal of six emerging pollutants (EPs) from university campus wastewater. The EPs considered were: diethyl phthalate (DEP), di-isobutyl phthalate (DIBP), di-n-octyl phthalate (DNOP), bis(2-ehtylxexyl) phthalate (DEHP), tris(1-chloro-2-propyl) phosphate (TCPP) and caffeine (CAF). Six pilot-scale CWs, i.e., three horizontal subsurface flow (HSF) and three vertical flow (VF), with different design configurations were used: two types of plants and one unplanted for both the HSF and the VF, two hydraulic retention times (HRT) for the HSF, and two wastewater feeding strategies for the VF units. The results showed that the median removals in the three HSF-CWs ranged between 84.3 and 99.9%, 79.0 and 95.7%, 91.4 and 99.7%, 72.2 and 81.0%, 99.1 and 99.6%, and 99.3 and 99.6% for DEP, DIBP, DNOP, DEHP, TCPP, and CAF, respectively. In the three VF-CWs, the median removal efficiencies range was 98.6–99.4%, 63.6–98.0%, 96.6–97.8%, 73.6–94.5%, 99.3–99.5% and 94.4–96.3% for DEP, DIBP, DNOP, DEHP, TCPP and CAF, respectively. The study indicates that biodegradation and adsorption onto substrate were the most prevalent removal routes of the target EPs in CWs.

Colorimetric assay based on arginine-functionalized gold nanoparticles for the detection of dibutyl phthalate in Baijiu samples

In this paper, a simple and innovative colorimetric method is established, which is based on DBP-induced aggregation of arginine functionalized gold nanoparticles (ARG-AuNPs), and can be used for the sensitive determination of dibutyl phthalate (DBP) in Baijiu samples. The morphological characteristics and the color changes of ARG-AuNPs caused by aggregation show good sensitivity, and can be observed through ultraviolet-visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential technology. The color change of ARG-AuNPs from red to blue is due to the strong non-covalent interactions between DBP and ARG-AuNPs (electrostatic, van der Waals force and hydrogen bonding), which leads to the reduction of the electrostatic repulsion between the nanoparticles and aggregation. A two-stage linear equation was established between the absorption ratio (A₆₉₀/A₅₃₀) and the DBP concentration (0.0-2.8 mg L^-1); the correlation coefficient (R²) was 0.9914-0.9940, and the detection limit (LOD) was estimated at 0.05 mg L^-1. The designed ARG-AuNPs acting as a dependable sensor for the detection of Baijiu samples equally acquired satisfactory recoveries. When the concentration of DBP in the solution is more than 1.0 mg L^-1, the color change can be clearly observed by the naked eye; so there is no need for sample preparation techniques and tedious operations to quickly and semi-quantitatively detect DBP. The successful application of the proposed method in Baijiu samples indicates its potential to detect DBP in more complex environment samples.

Contamination and human health risks of phthalate esters in vegetable and crop soils from the Huang-Huai-Hai region of China

The widespread presence of phthalate esters (PAEs) in a variety of agricultural inputs has led to PAE contamination in soils and farm products. The endocrine disruption and carcinogenicity of PAEs have attracted much attention. Our research investigated the characteristics of PAE pollution in the soils of vegetable fields and adjacent stable crop fields in four provinces/municipalities across a major agricultural production area in China. We found that the concentrations of PAEs in vegetable soils were not significantly higher than those in stable crop soils. The noncarcinogenic and carcinogenic risks from bis (2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) to humans were calculated to represent the risk posed by PAEs. The results showed that diet was the main route for noncarcinogenic risks from PAEs in crop soil and vegetable soils. Because of the combined effect of the population dietary structure and the concentration of PAEs in soils, the noncarcinogenic risks from PAEs in crop soils were similar to or higher than those in vegetable soils. The same pattern was also applicable to the carcinogenic risk from DEHP. Low noncarcinogenic and carcinogenic risks posed by DEHP and DBP indicated that the current level of PAEs in soils did not decrease the safety of agricultural products in the Huang-Huai-Hai region. Stable crop soil, as a non-negligibly phthalate-polluted area, is worthy of as much attention as vegetable soil. This study provides scientific support for food safety risk assessment and control of PAE pollution in the main agricultural production areas in China.

Biostimulation of Rhodovulum sp., for enhanced degradation of di-n-butyl phthalate under optimum conditions

Di-butyl phthalate (DBP) is an extensively applied synthetic plasticizer, toxic organic compound with elevated concentrations in aquatic and terrestrial ecosystem that cause serious risk to the human health. A marine bacterium Rhodovulum sp. DBP07 isolated from sea water with proficient of efficiently degrading DBP. The maximum DBP degradation (70.2%) and the cell growth (1.3 OD_600nm) were observed at 600 mg/L. The DBP degradation characteristics of the isolate Rhodovulum sp. DBP07 with diverse preliminary concentrations of DBP was found to be 200 ˃ 400 ˃ 600 ˂ 800 ˂ 1000 mg/L DBP. Glucose was identified as most favorable nutrient factor for the enhanced growth and showed 79.8 and 77.4% of degradation rate at 5.0 and 2.0 g/L respectively. The influence of the carbon sources on DBP degradation was found to be Glucose ˃ fructose ˃ sucrose ˃ maltose ˃ lactose ˃ citric acid ˃ starch. Box-Behnken (BBD) statistical optimization results showed enhanced DBP biodegradation rate (91.1%) at pH 7.0, 3% of NaCl concentration with 3 days of incubation. Two intermediate compounds were observed in the retention times of 10.8 and 12.2 which are identified as diethyl phthalate (DEP) and mono-nbutyl phthalate (MBP) using Gas chromatography mass spectroscopy (GC-MS). Furthermore, the phthalate (pht) gene expression pattern under DBP stress was analyzed using RT-qPCR and the maximum fold change (5.7 fold) was observed at 3 day of incubation. Overall, the observed results indicate the possibility of utilizing Rhodovulum sp. for remediation of DBP contaminated environment.

Prevalent phthalates in air-soil-vegetable systems of plastic greenhouses in a subtropical city and health risk assessments

Wide use of plastic greenhouses for vegetable production increases human exposure to phthalate (PAEs) through vegetable intake. However, little information is available about distribution of PAEs in air-soil-vegetable systems of plastic greenhouses and PAE estrogenic effects. This study was designed to investigate PAE distributions and corresponding health risk in plastic greenhouses in Guangzhou, a subtropical city in South China. PAEs were prevalent in plastic greenhouses, with sum concentrations of 16 PAE compounds (∑16PAEs) up to 5.76 mg/kg in soils, 5.27 mg/kg in vegetables and 4393 ng/m³ in air. Di (2-ethylhexyl) phthalate, di-isobutyl phthalate, and dibutyl phthalate were predominant compounds. Average concentrations and bioconcentration factor of ∑16PAEs and the predominant PAE compounds in vegetables of greenhouses were higher than those of open fields. Plastic greenhouses exhibited significantly higher air PAE levels than those of open fields due to higher indoor temperature, which enhanced PAE accumulation by vegetables. Both carcinogenic and non-carcinogenic risks of PAEs via dietary and non-dietary exposures for farmers decreased with an order of vegetable > air > soil. Consumption of vegetables from greenhouses resulted in significantly higher estrogenic effects compared to those from open field cultivation. This study emphasizes highly potential health risks of PAEs in air-soil-vegetable systems of plastic greenhouses.

Enhanced Biodegradation of Phthalic Acid Esters' Derivatives by Plasticizer-Degrading Bacteria (Burkholderia cepacia, Archaeoglobus fulgidus, Pseudomonas aeruginosa) Using a Correction 3D-QSAR Model

A phthalic acid ester’s (PAEs) comprehensive biodegradability three-dimensional structure-activity relationship (3D-QSAR) model was established, to design environmentally friendly PAE derivatives, which could be simultaneously degraded by plasticizer-degrading bacteria, such as Burkholderia cepacia, Archaeoglobus fulgidus, and Pseudomonas aeruginosa. Only three derivatives of diethyl phthalate (DEP (DEP-27, DEP-28 and DEP-29)) were suited for their functionality and environmental friendliness, which had an improved stability in the environment and improved the characteristics (bio-toxicity, bioaccumulation, persistence, and long-range migration) of the persistent organic pollutants (POPs). The simulation inference of the microbial degradation path before and after DEP modification and the calculation of the reaction energy barrier exhibited the energy barrier for degradation being reduced after DEP modification and was consistent with the increased ratio of comprehensive biodegradability. This confirmed the effectiveness of the comparative molecular similarity index analysis (CoMSIA) model of the PAE’s comprehensive biodegradability. In addition, a molecular dynamics simulation revealed that the binding of the DEP-29 derivative with the three plasticizer-degradation enzymes increased significantly. DEP-29 could be used as a methyl phthalate derivative that synergistically degrades with microplastics, providing directional selection and theoretical designing for plasticizer replacement.

Pollutants delivered every day: Phthalates in plastic express packaging bags and their leaching potential

The rapid development of the express industry brings not only convenience but also environmental problems such as plastic wastes. In this study, we collected plastic express packaging bags from major express companies in China to investigate phthalates in them. Infrared spectra indicated that all these samples were made from polyethylene but with different carbonyl index (CI) values. Total phthalates (∑Phthalates) concentrations in these samples ranged from 11.16 to 309.70 μg g^-1. Di(2-ethylhexyl) phthalate, di-n-butyl phthalate, and di-isobutyl phthalate were predominant phthalates. The leaching amounts of ∑Phthalates after 48 h ranged from 181.44 to 5320.64 ng g^-1. The leaching amounts of ∑Phthalates significantly positively related to ∑Phthalates concentrations of samples, while the leaching ratios presented opposite trends. Concentrations and leaching amounts of ∑Phthalates and major phthalates were significantly higher in samples from high CI value company group than those from low CI value company group. The results of our study indicate that plastic express packaging bags could be a critical source of phthalates. The involving of recycled plastics during the manufacture of plastic express packaging bags may influence the content and composition of phthalates in them and also increase the releasing risk of phthalates.

Bioaugmentation of Exogenous Strain Rhodococcus sp. 2G Can Efficiently Mitigate Di(2-ethylhexyl) Phthalate Contamination to Vegetable Cultivation

This work developed a bioaugmentation strategy that simultaneously reduced soil di(2-ethylhexyl) phthalate (DEHP) pollution and its bioaccumulation in Brassica parachinensis by inoculating the isolated strain Rhodococcus sp. 2G. This strain could efficiently degrade DEHP at a wide concentration range from 50 to 1600 mg/L and transformed DEHP through a unique biochemical degradation pathway that distinguished it from other Rhodococcus species. Besides, strain 2G colonized well in the rhizosphere soil of the inoculated vegetable without competition with indigenous microbes, resulting in increased removal of DEHP from soil (∼95%) and reduced DEHP bioaccumulation in vegetables (∼75% in the edible part) synchronously. Improved enzyme activities and DOC content in the rhizosphere of the planting vegetable and inoculating strain 2G were responsible for the high efficiency in mitigating DEHP contamination to vegetable cultivation. This work demonstrated a great potential application to grow vegetables in contaminated soil for safe food production.

Sorption Mechanism, Kinetics, and Isotherms of Di- n-butyl Phthalate to Different Soil Particle-Size Fractions

Di- n-butyl phthalate (DBP) is a prevalent pollutant in agricultural soils due to use of plastic film. This study focused on sorption mechanism, kinetics, and isotherms of DBP to six paddy soil particle-size fractions (i.e., coarse sand, fine sand, coarse silt, fine silt, clay, and humic acid fractions). DBP sorption involved in both boundary layer diffusion and intraparticle diffusion, following pseudo-second-order kinetics. DBP sorption was a spontaneous physical process, which fit the Freundlich model. Hydrophobic and ionic interaction relevant to the organic matter content, cation exchange capacity, surface area, and pore volume of soil fractions played key roles in DBP sorption. DBP was strongly adsorbed to humic acid and the sorption was reversely associated with soil particle sizes. DBP may exhibit higher mobility and bioavailability in a soil-crop system at lower temperature (15 °C), due to the lower log K_oc values.

Biodegradation pathway of di-(2-ethylhexyl) phthalate by a novel Rhodococcus pyridinivorans XB and its bioaugmentation for remediation of DEHP contaminated soil

A novel bacterial strain designated as Rhodococcus pyridinivorans XB, capable of utilizing various endocrine disruptor phthalates or phthalic acid (PA) as sole source of carbon and energy, was isolated from activated sludge. Under the optimal culture conditions (pH 7.08, 30.4 °C, inoculum size (OD_{600 nm}) of 0.6) obtained by response surface methodology, di-(2-ethylhexyl) phthalate (DEHP, 200 mg/L) could be degraded by strain XB with a removal rate of 98% within 48 h. Under the observation of an atomic force microscope, it was confirmed that DEHP did not inhibit the growth of strain XB which might produce some extracellular polymeric substances as a response to DEHP stress, resulting in rapid degradation of DEHP. At initial concentrations of 50-800 mg/L DEHP, its degradation curves were well fitted with the first-order kinetic model, and the half-life of DEHP degradation varied from 5.44 to 23.5 h. The degradation intermediates of DEHP were identified by both GC-MS and high performance liquid chromatography-time of flight-mass spectrometry (HPLC-TOF-MS). Significant up-regulation was observed for the relative expression levels of genes (i.e., phthalate hydrolase, PA 3,4-dioxygenase, protocatechuate 3,4-α and 3,4-β dioxygenase) involved in DEHP degradation determined by real-time quantitative PCR (RT-qPCR). A DEHP biodegradation pathway by strain XB was proposed based on the identified intermediates and the degrading genes. Bioaugmentation of DEHP-contaminated soils with strain XB could efficiently promote DEHP removal, offering great potential in bioremediation of DEHP-contaminated environment.

Biodegradation of di-butyl phthalate (DBP) by a novel endophytic bacterium Bacillus subtilis and its bioaugmentation for removing DBP from vegetation slurry

Di-butyl phthalate (DBP) is a widely used plasticizer, recalcitrant and hazardous organic compound with high detection frequencies and concentrations in water and soil that pose a great threat to human health. A novel endphytic bacterium strain N-1 capable of efficiently degrading DBP and utilizing it as sole carbon source was isolated from Ageratum conyzoides. This bacterium was identified as Bacillus subtilis based on its morphological characteristics and 16S rDNA sequence analysis. Under the optimal culture conditions (pH 7.0, 30 °C), degradation percentage of DBP (12.5-100 mg/L) was up to 95% within five days, and its biodegradation half-life was less than 7.23 h. Degradation percentage of high DBP concentration (200 mg/L) was relatively lower (89%) with half-life of 56.8 h. DBP was degraded by Bacillus subtilis N-1 into mono-butyl phthalate and phthalic acid as evidenced by GC-MS analysis. Bioaugmentation of Youngia japonica plant slurry with strain N-1 greatly accelerated DBP dissipation with 97.5% removal percentage (higher by 47% than non-inoculation). The results highlighted that strain N-1 has great potential for bioremediation by plant-endophyte partnerships and for lowering PAE accumulation in crops.

Variation in accumulation, transport, and distribution of phthalic acid esters (PAEs) in soil columns grown with low- and high-PAE accumulating rice cultivars

The extensive use of plasticizers containing di-n-butyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) results in high residual concentrations in agricultural soils and poses potential risks to human health through the food chain. Here, two rice cultivars with low (Fengyousimiao) and high (Peizataifeng) phthalic acid ester (PAE) accumulation were grown in leaching columns packed with DBP- and DEHP-contaminated soils to investigate their transport, fraction distribution, and accumulation in soil-rice-water system. Significant differences in soil vertical distribution of DBP and DEHP were observed among the two cultivars, sterilization and non-sterilization treatments. Both DBP and DEHP could leach to the bottom layer even though their concentrations in both soil and pore water decreased along with soil depth. DBP and DEHP concentrations in pore water were significantly correlated with those in corresponding soil layer at ripening stage. The available fractions including desorbing and non-desorbing fractions were predominant in the total concentrations of DBP and DEHP of soils. DBP and DEHP storages in coarse soil fractions (i.e., coarse and fine sands) with higher bioavailability displayed higher bioconcentration factors compared to finer soil fractions (i.e., silt and clay), and bioconcentration factors of Peizataifeng were higher than those of Fengyousimiao. The variations in vertical migration and accumulation of DBP and DEHP by the two cultivars implied different adverse effects on the security of groundwater and food.

Iron-based magnetic molecular imprinted polymers and their application in removal and determination of di-n-pentyl phthalate in aqueous media

Iron-based magnetic molecular imprinted polymers (Fe@SiO₂@MIP) were synthesized for highly selective removal and recognition of di-n-pentyl phthalate (DnPP) from water. Well-defined core-shell Fe@SiO₂ nanoparticles (less than 70 nm) were decorated on MIPs reticular layers to endow DnPP-MIPs with magnetic property for the first time. Five other phthalic acid esters including dimethyl phthalate, diethyl phthalate, dipropyl phthalate, di-n-butyl phthalate and di-iso-octyl phthalate were used to investigate the adsorptive selectivity to DnPP. The designed experiments were carried out to explore the adsorption kinetics, isotherms and thermodynamics and the results demonstrated that the adsorption was a spontaneous, exothermal and physical adsorption process. The materials were proved to be excellent adsorbents in removal of DnPP with an adsorption capacity as high as 194.15 mg g^-1 in optimal condition. Furthermore, a magnetic solid phase extraction with Fe@SiO₂@MIP coupled to high-performance liquid chromatography method was successfully developed for the determination of DnPP, and the proposed method achieved a good linear range of 0.5-250 µg l^-1 with a correlation coefficient (R²) of 0.999 and low limit of detection (LOD) of 0.31 µg l^-1. These materials exhibited excellent capacity in removal and highly sensitive identification of DnPP from aqueous environment samples, and opened a valuable direction for developing new adsorbents for the removal and enrichment of important pollutants.