Sorption behavior of 17 phthalic acid esters on three soils: effects of pH and dissolved organic matter, sorption coefficient measurement and QSPR study

Study on the mechanism and degradation behavior of Encifer adhaerens DNM-S1 capturing dimethyl phthalate

The global concern surrounding pollution caused by phthalates is escalating, with dimethyl phthalate (DMP) emerging as one of the most prevalent contaminants within the phthalates (PAEs) category. Although the biodegradation of DMP is considered both safe and efficient, its underlying degradation mechanism is not yet fully elucidated, and the degradation performance can be somewhat inconsistent. To address this issue, our study isolated a DMP-degrading bacterium (DNM-S1) from a vegetable greenhouse. The resulting data revealed that DNM-S1 exhibited a remarkable degradation performance, successfully degrading 84.98% of a 2000 mg L-1 DMP solution within 72 h. Remarkably, it achieved complete degradation of a 50 mg L-1 DMP solution within just 3 h. DMP degradation by DNM-S1 was also found to be efficient even under low-temperature conditions (10 °C). Our research further indicates that DNM-S1 is capable of capturing DMP through the ester bond in the bacterium's cell wall fatty acids, forming hydrogen bonds through hydrophobic interactions. The DMP was then transported into the DNM-S1 protoplasm using an active transport mechanism. Interestingly, the secondary metabolites of DNM-S1 contained natural carotenoids, which could potentially counteract the damaging effects of PAEs on cell membrane permeability. In summary, these findings highlight the potential of DNM-S1 in addressing PAEs pollution and provide new insights into the metabolic mechanism of PAEs degradation.

Influencing factors and risk assessment of phthalate ester pollution in the agricultural soil on a tropical island

Phthalate esters (PAEs) are widely prevalent in agricultural soil and pose potential risks to crop growth and food safety. However, the current understanding of factors influencing the behavior and fate of PAEs is limited. This study conducted a large-scale investigation (106 sites in 18 counties with 44 crop types) of 16 types of PAEs on a tropical island. Special attention was given to the impacts of land use type, soil environmental conditions, agricultural activity intensity, and urbanization level. The health risks to adults and children from soil PAEs via multiple routes of exposure were also evaluated. The results showed that the mean concentration of PAEs was 451.87 ± 284.08 μg kg-1 in the agricultural soil. Elevated agricultural and urbanization activities contributed to more pronounced contamination by PAEs in the northern and southern regions. Land use type strongly affected the concentration and composition of PAEs in agricultural soils, and the soil PAE concentration decreased in the order of vegetable fields, orchards, paddy fields, and woodlands. In paddy fields, di-isobutyl phthalate and di-n-butyl phthalate made more substantial contributions to the process through which the overlying water inhibited volatilization. Soil microplastic abundance, pesticide usage, crop yield, gross domestic product, and distance to the nearest city were calculated to be the major factors influencing the concentration and distribution of PAEs. Soil pH, organic matter content, microplastic abundance and the fertilizer application rate can affect the adsorption of PAEs by changing the soil environment. A greater risk was detected in the northern region and paddy fields due to the higher soil PAE concentrations and the dietary structure of the population. This study reveals important pathways influencing the sources and fate of PAE pollution in agricultural soils, providing fundamental data for controlling PAE contamination.

Phthalate esters pollution in the leachate, soil, and water around a landfill near the sea, Iran

This investigation aimed to scrutinize the level of phthalate esters (PEs) in the landfill leachate of a coastal city in the north of the Persian Gulf and the sensitive ecosystem (soil and water) around it. Soil (two depths) and water samples were prepared from 5 stations in wet and dry seasons. The studied landfill leachate contained 114-303 μg/L of phthalates. The highest concentration of phthalates was related to bis (2-ethylhexyl) phthalate (3257 ng/g) in the wet season at surface soil (0-5 cm) in the landfill site, while the lowest one (6 ng/g) belonged to dimethyl phthalate at sub-surface soil at 700 m from the landfill in the dry season. A significant change in the level of Σ6PEs in the dry (303 μg/L) and wet (114 μg/L) seasons (P ≤ 0.05) was observed for water samples. The PE concentrations in wet times were higher in all soil depths than in dry times. With increasing depth, the content of phthalates decreased in all studied environments. A direct relationship was observed between the phthalates concentration and the pH value of leachate/water and soil. The PEs concentration was linked to electrical conductivity (leachate: R2 = 0.65, P < 0.01 and surface soil: R2 = 0.77, P < 0.05) and the soil organic content. The ecological risk of di-n-butyl phthalate, benzyl butyl phthalate, bis (2-ethylhexyl) phthalate, and di-n-octyl phthalate in the wet season was greater than one. The results showed that significant levels of phthalate esters are released from landfills to the surrounding environment, which requires adequate measures to maintain the health of the ecosystem and nearby residents.

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.

The seasonal distribution of plasticizers in estuarine system: Controlling factors, storage and impact on the ecosystem

Plasticizers such as phthalate esters (PAEs) are commonly used in various consumer and industrial products. This widespread use raises valid concerns regarding their ubiquity in the environment and potential negative impacts. The present study investigates the distribution of eight common plasticizers in the largest European lagoon (Curonian Lagoon) located in the SE Baltic Sea. The concentration levels of plasticizers in the water column, containing both the dissolved and particulate-bound phases, and in sediments were evaluated to reveal seasonal patterns in distribution and potential effects on the lagoon ecosystem. A total of 24 water samples and 48 sediment samples were collected across all four seasons from the two dominant sedimentary areas within the lagoon. The average concentration of total PAEs in the water column ranged from 1 to 21 μg L-1, whereas sediment concentration varied from 5.0 to 250 ng g-1. The distribution of plasticizers was influenced by the patterns in hydrodynamics and water circulation within the lagoon. The confined south-central area contained a higher amount of PAEs in sediments, accounting for most of the lagoon's plasticizer accumulation. More than 7 tons of plasticizers are stored in the 5 upper centimetres of sediment, with over 3 tons persisting for more than five years. Di(2-ethylhexyl) phthalate (DEHP), Diisobutyl phthalate (DiBP), and Dibutyl phthalate (DnBP) were the most abundant PAE congeners, with DEHP posing the highest risk quotient to algae, based on water column concentration. Several other congeners demonstrated medium to high-risk levels for organisms living in the lagoon.

The role of extracellular polymeric substances (EPS) in chemical-degradation of persistent organic pollutants in soil: A review

Persistent organic pollutants (POPs) in soil show high environmental risk due to their high toxicity and low biodegradability. Studies have demonstrated the degradation function of microbial extracellular polymeric substances (EPS) on POPs in various matrices. However, the degradation mechanisms and the factors that influence the process in soil have not been clearly illustrated. In this review, the characteristics of EPS were introduced and the possible mechanisms of EPS on degradation of organic pollutants (e.g., external electron transfer, photodegradation, and enzyme catalysis) were comprehensively discussed. In addition, the environmental conditions (e.g., UV, nutrients, and redox potential) that could influence the production and degradation-related active components of EPS were addressed. Moreover, the current approaches on the application of EPS in biotechnology were summarized. Further, the future perspectives of enhancement on degradation of POPs by regulating EPS were discussed. Overall, this review could provide a new thought on remediation of POPs by widely-existing EPS in soil with low-cost and minimized eco-disturbance.

Insights into the effect of hydrochar-derived dissolved organic matter on the sorption of diethyl phthalate onto soil: A pilot mechanism study

Biowaste-derived hydrochar is an emerging close-to-natural product and has shown promise for soil improvement and remediation, but the environmental behavior of the dissolved organic matter released from hydrochar (HDOM) is poorly understood. Focusing on the typical mulch film plasticizer diethyl phthalate (DEP), we investigated the effect of HDOM on the sorption behavior of DEP on soil. The relatively low concentration of HDOM (10 mg L-1, 25 mg L-1) decreases the sorption quantity of DEP on soil, while it increases by a relatively high concentration, 50 mg L-1. The transformation from multilayer to monolayer sorption of DEP on soil occurs as the concentration of HDOM increases. The tryptophan-like substance is the main component of HDOM sorbed to soil, reaching 49.82 %, and results in competition sorption with DEP. The soil pores are blocked by HDOM, which limits the pore filling and mass transfer of DEP, but partitioning is significantly enhanced. The surface functional groups in HDOM are similar to those in soil, and chemical sorption, mainly composed of hydrogen bonding, exists but is not significantly strengthened. We identified the specific impact of HDOM on the sorption of organic pollutants on soil and provide new insights into the understanding of the environmental behavior of hydrochar.

Occurrence and health risk assessment of phthalates in a typical estuarine soil: A case study of the various functional areas of the Yellow River Delta

In recent years, the extensive distribution of phthalates (PAEs) in soils has attracted increasing attention. In this study, the concentrations of six types of PAEs were measured in five dissimilar regions of the Yellow River Delta (YRD), and regional differences, pollution characteristics and health risks of PAEs pollution were investigated. The detection rate of PAEs was 100 %, and the concentration range of Σ6PAEs was 0.709-9.565 mg/kg, with an average of 3.258 ± 2.031 mg/kg. There were different spatial distribution differences of PAEs in soils of the YRD, with residential living, chemical industrial, and crop growing areas being the main areas of PAEs distribution. It was worth noting that di (2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) are prominent contributors to PAEs in soils of the YRD. Correlation analyses showed that soils physicochemical properties such as SOM, TN and CEC were closely correlated to the transport and transformation of PAEs. Use by petrochemical industries, accumulation of plasticizers, additives (derived from cosmetics, food, pharmaceutical), fertilizers, pesticides, plastics, and atmospheric deposition are the principal sources of PAEs in the YRD. A health risk assessment showed that the health risk caused by non-dietary intake of PAEs was low and considered acceptable. PAEs pollution in the YRD soil is particularly noteworthy, especially for the prevention and control of DEHP and DBP pollution. This study provides basic data for an effective control of soil PAEs pollution in the YRD, which is conducive to the sustainable development of the region.

Assessment of phthalic acid esters plasticizers in sediments of coastal Alabama, USA: Occurrence, source, and ecological risk

Considering the ubiquitous occurrences and ecotoxicity of phthalates (PAEs), it is essential to understand their sources, distribution, and associated ecological risks of PAEs in sediments to assess the environmental health of estuaries and support effective management practices. This study provides the first comprehensive dataset on the occurrence, spatial variation, inventory, and potential ecological risk assessment of PAEs in surface sediments of commercially and ecologically significant estuaries in the southeastern United States, Mobile Bay and adjoining eastern Mississippi Sound. Fifteen PAEs were widely detected in the sediments of the study region, with total concentrations varying between 0.02 and 3.37 μg/g. The dominance of low-molecular-weight (LMW) PAEs (DEP, DBP and DiBP) relative to high-molecular-weight (HMW) PAEs (DEHP, DOP, DNP) indicates that residential activities have stronger impacts than industrial activities on PAE distributions. The total PAE concentrations displayed an overall decreasing trend with increasing bottom water salinity, with the maximum concentrations occurring near river mouths. These observations suggest that river inputs were an important pathway by which PAEs were transported to the estuary. Linear regression models identified sediment adsorption (measured by total organic carbon and median grain size) and riverine inputs (measured by bottom water salinity) as significant predictors for the concentrations of LMW and HMW PAEs. Estimated 5-year total inventories of sedimentary PAEs in Mobile Bay and the eastern Mississippi Sound were 13.82 tons and 1.16 tons, respectively. Risk assessment calculations suggest that LMW PAEs posed a medium-to-high risk to sensitive aquatic organisms, and DEHP posed a low or negligible risk to the aquatic organisms. The results of this study provide important information needed for establishing and implementing effective practices for monitoring and regulating plasticizer pollutants in estuaries.

Contribution of molecular structures and quantum chemistry technique to root concentration factor: An innovative application of interpretable machine learning

Root concentration factor (RCF) is a significant parameter to characterize uptake and accumulation of hazardous organic contaminants (HOCs) by plant roots. However, complex interactions among chemicals, plant roots and soil make it challenging to identify underlying mechanisms of uptake and accumulation of HOCs. Here, nine machine learning techniques were applied to investigate major factors controlling RCF based on variable combinations of molecular descriptors (MD), MACCS fingerprints, quantum chemistry descriptors (QCD) and three physicochemical properties related to chemical-soil-plant system. Compared to models with variables including MACCS fingerprints or solitary physicochemical properties, the XGBoost-6 model developed by the variable combination of MD, QCD and three physicochemical properties achieved the most remarkable performance, with R2 of 0.977. Model interpretation achieved by permutation variable importance and partial dependence plots revealed the vital importance of HOCs lipophilicity, lipid content of plant roots, soil organic matter content, the overall deformability and the molecular dispersive ability of HOCs for regulating RCF. The integration of MD and QCD with physicochemical properties could improve our knowledge of underlying mechanisms regarding HOCs accumulation in plant roots from innovative structural perspectives. Multiple variables combination-oriented performance improvement of model can be extended to other parameters prediction in environmental risk assessment field.

Composition, distribution, health risks, and drivers of phthalates in typical red paddy soils

The accelerated accumulation of phthalate esters (PAEs) in paddy soils poses a serious threat to human health. However, related studies mainly focus on facility vegetable fields, drylands, and orchards, and little is known about paddy soils. In this study, 125 samples were collected from typical red paddy fields to investigate the pollution characteristics, sources, health risks, and main drivers of PAEs. Soil physicochemical properties, enzyme activity, and bacterial community composition were also measured simultaneously. The results showed that eight PAE congeners were detected ranging from 0.17 to 1.97 mg kg-1. Di-n-butyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP), and di-isobutyl phthalate (DIBP) were the most abundant PAE congeners, accounting for 81% of the total PAEs. DEHP exhibited a potential carcinogenic risk to humans through the intake route. The main PAEs were positively correlated with soil organic matter (SOM) and soil water content (SWC) contents. Low levels of PAEs increased bacterial abundance. Furthermore, most PAE congeners were positively correlated with hydrolase activity. Soil acidity and nutrient dynamics played a dominant role in the bacterial community composition, with PAE congeners playing a secondary role. These findings suggest that there may be a threshold response between PAEs and organic matter and nutrient transformation in red paddy soils, and that microbial community should be the key driver. Overall, this study deepens the understanding of ecological risks and microbial mechanisms of PAEs in red paddy soils.

Adsorptive removal of dimethyl phthalate using peanut shell-derived biochar from aqueous solutions: equilibrium, kinetics, and mechanistic studies

Rise in polymer industry and extensive use of their products leads to leaching of phthalate esters and distributed into the different matrices of the environment. This chemical group has the potential to hamper the life of living organisms and ecosystem. Thus, it is essential to develop cost-effective adsorbents capable of removing these harmful compounds from the environment. In this work, peanut hull-derived biochar was taken as the adsorbent, and DMP was selected as the model pollutant or adsorbates. The biochars of different properties were produced at three pyrolysis temperatures (i.e., 450, 550, and 650 °C) to check how temperature affected the adsorbent properties and adsorption performance. Consequently, the performance of biochars for DMP adsorption was thoroughly studied by the combination of experiments and compared with commercial activated carbon (CAC). All the adsorbents are meticulously characterized using various analytical techniques and used for adsorption DMP from aqueous solutions. The results suggested that adsorption was favoring chemisorption with multi-layered adsorption as adsorption kinetics and isotherm are in good alignment with pseudo-second-order kinetics and Freundlich isotherm, respectively. Further, thermodynamic study revealed DMP adsorption on adsorbent is physically spontaneous and endothermic. The removal efficiency order of four adsorbent was as follows: BC650 > CAC > BC550 > BC450 with maximum efficiency of 98.8% for BC650 followed by 98.6% for CAC at optimum conditions. And as it is a short carbon chain PAE, dominant mechanisms of adsorption for DMP onto porous biochar were H-bonding, π-π EDA interactions, and diffusion within the pore spaces. Therefore, this study can provide strategies for the synthesis of biochar for effectively removing DMP from aqueous solution.

Divergence in the distribution of di(2-ethylhexyl) phthalate (DEHP) in two soils

Understanding the distribution of di(2-ethylhexyl) phthalate (DEHP) is necessary for future risk evaluation of DEHP in agricultural soils. This study used 14C-labeled DEHP to examine its volatilization, mineralization, extractable residues, and non-extractable residues (NERs) incubated in Chinese typical red and black soil with/without Brassica chinensis L. Results showed that after incubated for 60 days, 46.3% and 95.4% of DEHP were mineralized or transformed into NERs in red and black soil, respectively. The distribution of DEHP in humic substances as NER descended in order: humin > fulvic acids > humic acids. DEHP in black soil was more bioavailable, with 6.8% of initial applied radioactivity left as extractable residues at the end of incubation when compared with red soil (54.5%). Planting restrained the mineralization of DEHP by 18.5% and promoted the extractable residues of DEHP by 1.5% for black soil, but no such restrain was observed in red soil. These findings provide valuable information for understanding the distribution of DEHP in different soils and develop the understanding for the risk assessments of PAEs in typical soils.

Estimation and potential ecological risk assessment of multiphase PAEs in mangrove wetlands in Dongzhai Harbor, Hainan

With the application of plastic products, phthalates now widely occur in various environmental media. A large number of ecological risk assessment experiments have only been carried out on a single medium such as water or sediment. There are few reports of ecological risk assessments based on the phase states of phthalic acid esters (PAEs) such as the free dissolved state and the dissolved organic carbon (DOC) adsorption state. In this study, the concentrations of the free dissolved state, the DOC adsorption state, and the easily released PAEs in the sediments, as well as the dissolved organic carbon release potential and their influencing factors were calculated in the Dongzhaigang water body. The potential ecological risks posed by state-of-the-art PAEs were investigated. The average concentration of six freely dissolved PAEs in water was 0.542 (0.226-1.115) μg/L, accounting for 76.3 % of the total PAEs. The PAEs with the highest concentrations in the free dissolved state were di-n-butyl phthalate (DBP, 0.383 μg/L), followed by Di(2-ethylhexyl) phthalate (DEHP, 0.094 μg/L). The average concentration of all six PAEs (∑6PAEs) adsorbed by the DOC in the water was 0.172 μg/L, accounting for 23.74 % of all of the PAEs. The DOC-adsorbed DEHP (0.148 μg/L) accounted for about 86 % of the six adsorbed PAEs. Sediment organic carbon may affect the release potential of the DOC through changing the soluble organic carbon concentration. Most types of PAEs in water posed low risk to organisms. However, DBP posed low and medium risk to algae and crustaceans, and medium risk to fish. Medium or high risk of DEHP to algae, crustaceans and fish was observed. The high ecological risk of PAEs related to sediments were only found at S13 and S14. Generally, the potential ecological risk of PAEs in sediment was more stable than that in water bodies.

Occurrence, source, ecological risk, and mitigation of phthalates (PAEs) in agricultural soils and the environment: A review

The widespread distribution of phthalates (PAEs) in agricultural soils is increasing drastically; however, the environmental occurrence and potential risk of PAEs in agricultural systems remain largely unreviewed. In this study, the occurrence, sources, ecotoxicity, exposure risks, and control measures of PAEs contaminants in agricultural soils are summarized, and it is concluded that PAEs have been widely detected and persist in the soil at concentrations ranging from a few μg/kg to tens of mg/kg, with spatial and vertical variations in China. Agrochemicals and atmospheric deposition have largely contributed to the elevated contamination status of PAEs in soils. In addition, PAEs cause multi-level hazards to soil organisms (survival, oxidative damage, genetic and molecular levels, etc.) and further disrupt the normal ecological functions of soil. The health hazards of PAEs to humans are mainly generated through dietary and non-dietary pathways, and children may be at a higher risk of exposure than adults. Improving the soil microenvironment and promoting biochemical reactions and metabolic processes of PAEs are the main mechanisms for mitigating contamination. Based on these reviews, this study provides a valuable framework for determining future study objectives to reveal environmental risks and reduce the resistance control of PAEs in agricultural soils.

Influence of Organic Matter on the Sorption of Cefdinir, Memantine and Praziquantel on Different Soil and Sediment Samples

Pharmaceuticals are known for their great effects and applications in the treatment and suppression of various diseases in human and veterinary medicine. The development and modernization of science and technologies have led to a constant increase in the production and consumption of various classes of pharmaceuticals, so they pose a threat to the environment, which can be subjected to the sorption process on the solid phase. The efficiency of sorption is determined by various parameters, of which the physicochemical properties of the compound and the sorbent are very important. One of these parameters that determine pharmaceutical mobility in soil or sediment is the soil−water partition coefficient normalized to organic carbon (Koc), whose determination was the purpose of this study. The influence of organic matter, suspended in an aqueous solution of pharmaceutical (more precisely: cefdinir, memantine, and praziquantel), was studied for five different types of soil and sediment samples from Croatia. The linear, Freundlich, and Dubinin−Raduskevich sorption isotherms were used to determine specific constants such as the partition coefficient Kd, which directly describes the strength of sorbate and sorbent binding. The linear model proved to be the best with the highest correlation coefficients, R2 > 0.99. For all three pharmaceuticals, a positive correlation between sorption affinity described by Kd and Koc and the amount of organic matter was demonstrated.

Composting and green technologies for remediation of phthalate (PAE)-contaminated soil: Current status and future perspectives

Phthalate esters (PAEs) are hazardous organic compounds that are widely added to plastics to enhance their flexibility, temperature, and acidic tolerance. The increase in global consumption and the corresponding environmental pollution of PAEs has caused broad public concerns. As most PAEs accumulate in soil due to their high hydrophobicity, composting is a robust remediation technology for PAE-contaminated soil (efficiency 25%-100%), where microbial activity plays an important role. This review summarized the roles of the microbial community, biodegradation pathways, and specific enzymes involved in the PAE degradation. Also, other green technologies, including biochar adsorption, bioaugmentation, and phytoremediation, for PAE degradation were also presented, compared, and discussed. Composting combined with these technologies significantly enhanced removal efficiency; yet, the properties and roles of each bacterial strain in the degradation, upscaling, and economic feasibility should be clarified in future research.

An Insight into the Sorption Behavior of 2,3,7,8-Tetrachlorodibenzothiophene on the Sediments and Paddy Soil from Chaohu Lake Basin

Considering the frequent detection of polychlorinated dibenzothiophenes (PCDTs) in various environmental matrices and the potential ecological health risks, the environmental behavior of such compounds needs to be elucidated further. In this work, the sorption behavior of 2,3,7,8-tetrachlorodibenzothiophene (2,3,7,8-TCDT) onto three sediments and paddy soil from Chaohu Lake were investigated via batch equilibration experiments. From the perspective of sorption kinetics and isotherms, the sorption characteristics and mechanism of 2,3,7,8-TCDT on the above four carriers were compared, and the relationship between their structural characteristics and soil sorption capacity was discussed. Results suggested that rapid sorption played the primary role during the sorption process of 2,3,7,8-TCDT and the corresponding sorption isotherms were well fitted using the Freundlich logarithmic model. Moreover, the effects of pH and dissolved organic matter (DOM) on the sorption of 2,3,7,8-TCDT were investigated. The maximum sorption capacity of 2,3,7,8-TCDT on sediment was under acidic pH condition (pH = 4.0). Meanwhile, DOM at a low level promoted the sorption capacity of sediment toward 2,3,7,8-TCDT, while the high concentration of DOM inhibited this effect. In addition, the values of logK_oc were obtained using high-performance liquid chromatography (HPLC) and did not show any significant correlation with organic carbon (OC) contents, thereby indicating that the partition effect was the dominating influencing factor for the sorption of 2,3,7,8-TCDT both on sediments and soil. This work provides useful data to understand the sorption behavior of 2,3,7,8-TCDT on sediments and soil and assess its potential environmental risk.

Occurrence of Phthalate Acid Esters (PAEs) in Protected Agriculture Soils and Implications for Human Health Exposure

This study explored occurrence of phthalic acid esters (PAEs) in protected agriculture soils and assessed their potential health risks to humans. Results showed that DEHP and DBP were the most abundant PAEs congeners, with mean concentrations of 318.68 μg/kg and 137.56 μg/kg, respectively. DOP and BBP concentrations were relatively low, and DMP and DEP were not detected in all samples. DBP concentrations were higher than the allowable concentration standard value. Additionally, soil pH and organic matter were key environmental parameters which may play the vital roles to the occurrence of organic pollutants. Heath risk assessment results indicated that dermal contact was the predominant human exposure route under non-dietary conditions, and children obtained higher health risk scores than adults. In summary, the overall health risk scores were at an acceptable level. These results provide insights for assessing soil environmental safety and ecological risks in protected agricultural soil.

Comparison of Different Chemical Extraction Methods for Predicting the Bioavailability and Phytotoxicity of Soil PAEs to Green Vegetables (Brassica Rapa Var. Chinensis)

The aim of the present study was to compare the predictive ability of four chemical extraction methods, i.e., Tenax, hydroxypropyl[β]cyclodextrin (HPCD), n-butanol and low-molecular-weight-organic-acids (LMWOA), for predicting the bioavailability and phytotoxicity of soil phthalic acid esters to the green vegetable Shanghaiqing (SHQ). Results showed that the extraction ability of different extraction methods varies significantly. For dibutyl phthalate (DBP), the extraction ability followed the order of Tenax > LMWOA > HPCD > n-butanol. For di-(2-ethylhexyl) phthalate (DEHP), the order of the extraction ability was n-butanol > HPCD > Tenax > LMWOA. All the extraction methods underestimated the DBP concentration while overestimating the DEHP concentration accumulated by SHQ. The concentrations of DBP and DEHP extracted by Tenax were most related to the concentrations accumulated by SHQ and the phytotoxicity indicators of SHQ. Tenax can serve as a good chemical extractant to assess the bioavailability and phytotoxicity of soil DBP and DEHP to SHQ.

The investigation of influencing factors on the degradation of sulfonamide antibiotics in iron-impregnated biochar-activated urea-hydrogen peroxide system: A QSAR study

Iron-impregnated biochar-activated urea-hydrogen peroxide (FB-activated UHP) is a potential in-situ technology for simultaneously reducing soil sulfonamide antibiotic contaminants and improving soil fertility. To better understand the degradation of sulfonamide antibiotics by FB-activated UHP, a two-dimensional quantitative structure-activity relationship (2D-QSAR) model based on quantum chemical parameters and a three-dimensional QSAR (3D-QSAR) model based on molecular force field were developed to investigate the factors influencing the removal efficiencies (Re%). The optimal 2D-QSAR model was Re%= 0.858-8.930 E-5 E_B3LYP-0.175 f(+)_x with the evaluation indices of R²= 0.732, q²= 0.571, and Q_ext²= 0.673. The given 2D-QSAR model indicated that the molecular size (E_B3LYP) and Fukui index with respect to nucleophilic attack (f(+)) were intrinsic factors influencing Re%. Three degradation pathways were subsequently proposed based on the f(+) distribution. Compared to the 2D-QSAR model, the developed 3D-QSAR model exhibited a better predictive ability, with the evaluation indices of R²= 0.989, q²= 0.696, and SEE= 0.001. The analysis of field contribution rates suggested that electrostatic field (48.2%), hydrophobic field (25.3%), and hydrogen-bond acceptor field (12.7%) were the main factors influencing Re%. These findings generated critical information for evaluating the degradation mechanisms/rules and provided theoretical bases for initially estimating the Re% of sulfonamide antibiotics undergoing FB-activated UHP process.

OPFRs in e-waste sites: Integrating in silico approaches, selective bioremediation, and health risk management of residents surrounding

A multilevel index system of organophosphate flame retardant bioremediation effect in an e-waste handling area was established under three bioremediation scenarios (scenario I, plant absorption; scenario II, plant-microbial combined remediation; scenario III, microbial degradation). Directional modification of OPFR substitutes with high selective bioremediation was performed. The virtual amino acid mutation approach was utilised to generate high-efficiency selective absorption/degradation mutant proteins (MPs) in a plant-microbial system under varying conditions. In scenario III, the MP's microbial degrading ability to replace molecules was increased to the greatest degree (165.82%). Appropriate foods such as corn, pig liver, and yam should be consumed, whereas the simultaneous consumption of high protein foods such as pig liver and walnut should be avoided; sweet potato and yam are believed to be prevent OPFRs and substitute molecules from entering the human body through multiple pathways for reduced genotoxicity of OPFRs in the populations of e-waste handling areas (the reduction degree can reach 85.12%). The study provides a theoretical basis for the development of ecologically acceptable OPFR substitutes and innovative high-efficiency bioremediation MPs, as well as for the reduction of the joint toxicity risk of multiple ingestion route exposure/gene damage of OPFRs in high OPFR exposure sites.

Phthalate's multiple hormonal effects and their supplementary dietary regulation scheme of health risks for children

Four common phthalic acid esters (PAEs), namely, butylbenzyl phthalate (BBzP), dibutyl phthalate (DBP), di(2-ethylhexyl) phthalate (DEHP), and di-n-octyl phthalate (DNOP) that are known to affect children upon exposure, were selected, and the hormone effects were explored during different supplementary food intakes by using methods such as factorial design experiment, molecular docking, and dynamics simulation techniques. A supplementary diet regulation scheme to prevent health risks of PAEs was constructed to avoid or mitigate the hormonal effects in children exposed to PAEs. Firstly, the MM/PBSA binding energy of PAEs with single hormone receptors and multiple hormone receptor complexes was calculated. In addition, 10 foods were selected as external interference conditions to carry out dynamic simulation, which showed that kiwi fruit and broccoli can effectively alleviate the PAEs' hormone effects. Furthermore, inference of the metabolic process of DEHP found that the supplementary diets could effectively promote the metabolism of PAEs. Finally, based on the mechanism analysis, it was confirmed that the selected supplementary diets could inhibit the binding process. This study aims to explore the role of supplementary diets in regulating various PAEs' hormone effects and thereby provide theoretical support for slowing down hormonal effects in children.

PAEs Derivatives' Design for Insulation: Integrated In-Silico Methods, Functional Assessment and Environmentally Friendly Molecular Modification

As a common substance in production and life, phthalic acid esters (PAEs), the main component of plastics, have brought more and more serious problems to the environment. This study normalized the insulation, toxicity, and bioconcentration data of 13 PAEs to eliminate the dimensional coefficients of each index, and then used the comprehensive index method to calculate the comprehensive effect value of PAEs with three properties. The comprehensive effect value was used as the data source to construct the 3D-QSAR model of PAE molecular comprehensive effect. The DAP was selected as the target molecule, the distribution of each force field in the three-dimensional equipotential map was analyzed, and 30 molecular modification schemes were created. The constructed single-effect models of insulation, toxicity, and bioconcentration of PAEs and the scoring function module of DS software were used to evaluate the stability and environmental friendliness of PAE derivative molecules. Four PAE derivatives were screened for increased comprehensive effects, enhanced insulation, and reduced toxicity and bioconcentration. By calculating the binding energy of the target molecule and the derivative molecule with the degrading enzyme under different applied electric fields, it was found that the binding energy of DAP-1-NO2-2-CH2C6H5 decreases more than DAP does when there is an applied electric field, indicating that the degradation ability of degrading enzymes on PAE derivative molecules is reduced, which indirectly proves that the insulation is enhanced. The innovation of this paper lies in the insulation, toxicity, and bioenrichment data of PAEs being processed by mathematical method for the first time, and PAEs with high insulation, low toxicity, and low bioconcentration were designed by building a comprehensive model.

Accumulation of phthalates under high versus low nitrogen addition in a soil-plant system with sludge organic fertilizers instead of chemical fertilizers

Nitrogen is the main nutrient in soil. The long-term addition of N leads to changes in the soil dissolved organic matter (DOM) and other quality indicators, which affects the adsorption and accumulation of organic pollutants. The use of organic fertilizer is important for the development of green agriculture. However, organic fertilizers (especially sludge organic fertilizers (SOFs) contain phthalates (PAEs) that may accumulate in the soil and result in environmental contamination. How this accumulation response varies with the magnitude of long-term N addition, especially in different soil layer profiles, remains unclear. Here, changes in the content of PAEs in the soil-plant system without and after SOFs application were studied through field experiments in soils with different N addition backgrounds (CK, N1, N3 (0, 100, 300 kg N ha^-1 yr^-1 respectively)). Our results showed that the application of SOFs increase the accumulation of PAEs in soil profiles and plant systems, increasing human health risks. The content of Σ₅PAEs in the topsoil increased from 0.96 ± 0.10 to 1.86 ± 0.09 mg kg^-1. Moreover, under a high N addition background and SOFs application, the characteristics of soil DOM change, and the accumulation of PAEs in soil was nearly 30% higher compared with the low N group. Some suggestions such as removing PAEs from SOFs during preparation, conducting soil surveys before applying PAEs, and using soil amendments, which are provided for optimizing the trialability and environmental safety of SOFs application.

Reduction effects of solar radiation, mechanical tension, and soil burial on phthalate esters concentrations in plastic film and soils

Phthalate esters (PAEs) are potentially dangerous chemicals in plastic film mulched fields; however, few studies have investigated how to reduce their concentrations in plastic film and soil. In this study, the effects of solar radiation, mechanical tension, and soil burial on PAEs concentrations in polyethylene (PE) film and degradable film were investigated, and the half-lives of di-n-butyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) in soil also studied. PAEs concentrations in polyethylene films were about twice those in the degradable films; however, PAEs concentrations in all experimental films were similar after 1-year of field exposure. Mechanical tension had no effect on the PAEs concentrations of polyethylene films, but increased the detected concentrations of PAEs in degradable films by 34%-120%. After 4-years of burial, the PAEs concentrations in films decreased by 79.2%-98.0%, and mechanical tension promoted the reductions. However, there was little difference in PAEs concentrations between the buried soils with and without films, indicating the released PAEs reduced quickly in soil. Also, the half-lives of DBP and DEHP were 2.4-4.6 days and 18.5-41.4 days, respectively. Overall, the results presented herein provide reasonable approaches to reduce the concentrations of PAEs in plastic films and soils.

Facilitating effect of heavy metals on di(2-ethylhexyl) phthalate adsorption in soil: New evidence from adsorption experiment data and quantum chemical simulation

In terms of researching and treating farmland pollution, interactions between organic and inorganic pollutants are very important aspects. Herein, the effects of heavy metals on di(2-ethylhexyl) phthalate (DEHP) adsorption in soil were investigated. The presence of Cd²⁺/Cu²⁺ increased the adsorption capacity of DEHP (>23%) in a nonlinear manner. Fourier transform infrared spectroscopy revealed that the stretching vibration of soil functional groups changed under different pollution combinations, while quantum chemical simulation, including an independent gradient model and localized orbital locator, proved that outer-orbital complexes could be formed by electrostatic interaction between Cd²⁺/Cu²⁺ and DEHP. The electron transfer process was analyzed by charge decomposition analyses, and these, combined with bond critical point analyses, revealed that metal ions reduced DEHP stability. The binding energy and binding free energy of different combinations were calculated and analyzed, using the key soil organic matter (SOM) information obtained through pyrolysis gas chromatography mass spectrometry. This effectively explained the adsorption behavior, and showed that SOM polar functional groups played an important role in the effect of heavy metals on DEHP adsorption. The study described here has provided a new basis for understanding the multiple interactions, accumulation, and transformation of pollutants in the soil.

Effects of endogenous and exogenous dissolved organic matter on sorption behaviors of bisphenol A onto soils

The transport of organic contaminants in groundwater might be greatly affected by coexistence of dissolved organic matter (DOM) from different sources. In this study, the effects of endogenous and exogenous DOMs (referred to as DOM_en and DOM_ex, respectively) on sorption behavior of bisphenol A (BPA) onto two reference soils were investigated by batch experiments and microscopic characterization. The results showed that BPA sorption onto soils was dominated by soil organic matter content and affected by DOM properties. The effect of DOM_en on BPA sorption was also related to the inorganic components of the two soils. The decrease of organic matter content reduced the sorption capacity of fluvo-aquic soil. However, because the content of available inorganic components in black soil was high, after removing DOM_en, more inorganic sites were exposed to increase the sorption capacity. In addition, DOM_en could form complexes with BPA in solution, thus the removal of DOM_en promoted BPA sorption onto black soil. Under the experimental conditions, contribution of DOM_ex to the total sorption of BPA onto both soils was not more than 30%. Results of dialysis experiments and soil sorption experiments indicated that effects of coexisting DOM_ex on BPA sorption was related to the affinity of DOM_ex to soils and complexation of BPA and DOM_ex. Since the affinity of DOM_ex to fluvo-aquic soil was relatively low, the complex of BPA and DOM_ex in solution was the main inhibition mechanism for BPA sorption. For black soil, higher complexation proportion of BPA with DOM_ex adsorbed onto soil which promoted BPA sorption onto soil. The findings are of significance for understanding the co-migration of DOM with BPA through soils.

A model for phthalic acid esters' biodegradability and biotoxicity multi-effect pharmacophore and its application in molecular modification

The objective of this study was to investigate 13 phthalic acid esters (PAEs) with medium or long straight-alkyl-chain, branching or unsaturated side chains, because their structural characteristics make them difficult to biodegrade or highly toxic. A biodegradability and biotoxicity multi-effect pharmacophore model was built using comprehensive evaluation method. The results suggested that introducing hydrophobic groups to the side chains of the PAEs could improve the molecules' biodegradability and biotoxicity effects simultaneously. Thus, 40 target PAE (HEHP, DNOP, DUP) derivatives were designed. Two environmentally friendly PAE derivatives (HEHP-Anthryl and HEHP-Naphthyl) were screened via the test of environmental friendliness and functionality. In addition, the biodegradation and biotoxicity of derivatives were found to have improved as a result of the change in van der Waals forces between molecules and their corresponding proteins. Moreover, the environmental safety of the screened PAE derivatives was confirmed by predicting the toxicity of their intermediates and calculating the energy barrier values for biodegradation and metabolic pathways. This study could provide theoretical guidance for the practical development of environmentally friendly plasticizer.

Effect of polyethylene particles on dibutyl phthalate toxicity in lettuce (Lactuca sativa L.)

The effects of dibutyl phthalate (DBP) on the toxicity and edible quality (e.g., soluble proteins, soluble sugars, and vitamin C) of green and purple lettuce in the presence of polyethylene (PE) fragments were evaluated. The results revealed that PE treatment for 28 days decreased DBP and monobutyl phthalate content in lettuce roots and leaves, but enhanced the inhibitory effects of DBP on root growth and activity, reduced soluble protein and sugar content in lettuce leaves, and increased vitamin C content in lettuce leaves. Scanning and transmission electron microscopies revealed that PE only adhered to the root surface and did not enter the lettuce roots. Moreover, separation of the cell wall was aggravated in lettuce roots treated with DBP+PE, but not in lettuce treated with individual DBP or PE, and even led to the expansion of endoplasmic reticulum vesicles and cell rupture. Gaussian analysis indicated that PE interacted with DBP molecules through van der Waals interactions, which decreased DBP transport from the culture solution into the lettuce roots. In addition, purple lettuce was more sensitive to exogenous pollutants than green lettuce. This study provides new insights for food safety related to DBP fate and toxicity under PE stress.

Sorption behavior of dimethyl phthalate in biochar-soil composites: Implications for the transport of phthalate esters in long-term biochar amended soils

The characteristics and content of organo-mineral complex were confirmed to be changed in agriculture soils under the biochar application with long-term, but the resulting environmental effects in the retention and lasting of agrochemicals and xenobiotic pollutants is far from clear. In this study, biochar-soil composites were prepared by one-step dry ball-milling method, and a sorption case study was proceed to investigate the biochar incorporated affection in soils on the transport of dimethyl phthalate (DMP). More surface oxygen-containing functional groups on ball-milled biochar enhanced its complexation with soil minerals. Sorption isotherms of DMP onto the biochar-soil composites were well described by the Freundlich model, both heterogeneous surface and multilayer interactions occurred simultaneously. The kinetics of sorption could be simulated with the pseudo-second-order model (R² > 0.98), while the average sorption energy (E_a) calculated from Dubinin-Radushkevich isotherms were found in the range of 3.83-5.60 kJ mol^-1, which revealed that the sorption processes coexist of chemisorption and physisorption, and π-π electron donor-acceptor interaction, pore-filling and hydrophobic interactions could be identified as the main sorption mechanisms. Desorption of absorbed DMP appeared obvious nonlinear characteristics and lag effect, the calculated hysteresis index (HI) increased with the application of biochar into soil. Considering the phenomenon of biochar aging and soil complexation, it is important to verify how the transport and natural attenuation of contaminant will be influenced by biochar addition, especially the long-term effect in soil ecosystem.

The Age Distribution among Children Seeking Medical Treatment for Precocious Puberty in Taiwan

Objective: Children with precocious puberty (PP) may have increased physiological and psychological problems. In this study, we aimed to explore the trend of parents seeking medical care for their children with precocious puberty. Methods: The Taiwan National Health Insurance Research Dataset (NHIRD) was used to estimate the prevalence (2000–2013) and incidence (2002–2013) of PP (ICD-9 code: 259.1) among boys aged 0–11 years and girls aged 0–10 years. The proportions of PP management within 1 year from the date of first diagnosis were also compared between two periods (2002–2007 and 2008–2012). The trends of PP prevalence or incidence were determined by join-point regression. Results: In 2000, 309 boys and 2706 girls had at least one visit for PP, the crude prevalence rates (per 10,000 persons) were 0.99 (95% confidence interval, 95% CI 0.87–1.14) and 13.56 (95% CI 13.01–14.13) in boys and girls, respectively. In 2013, the crude prevalence rates increased to 7.01 (95% CI 6.56–7.84) and 110.95 (95% CI 108.97–112.96) in boys and girls, respectively. A total of 2584 girls and 207 boys with incident PP cases were identified in 2002, and 7498 girls and 739 boys were identified in 2013. For girls, the incidence rates (per 10,000 person-years) were 16.17 (95% CI 15.55–16.80) and 70.23 (95% CI 68.65–71.83) in 2002 and 2013, respectively. For boys, the incidence rates were 1.09 (95% CI 0.95–1.24) and 5.72 (95% CI 5.32–6.15) in 2002 and 2013, respectively. The sex ratio (F:M) of the incidence of PP cases was 14.89 in 2002 and 12.28 in 2013. Conclusion: In this study, from 2000 to 2013, the frequency of visiting pediatric endocrinology outpatient clinics for precocious puberty increased in both genders. We advocate that it is important to pay increased attention to children’s health, environmental hormones, and diet. Researchers should consider how to survey precocious puberty and offer parents more education to avoid the waste of medical resources or delays in seeking medical care.

Efficient transformation of diethyl phthalate using calcium peroxide activated by pyrite

In this study, pyrite (FeS₂) was used as a novel activator of calcium peroxide (CaO₂) for the degradation of diethyl phthalate (DEP) in both aqueous solution and soil. DEP (10 mg/L) in aqueous solution was completely degraded within 5.0 min by the FeS₂ (0.30 g/L)/CaO₂ (1.0 mM) system at pH 3.5. X-ray diffraction (XRD), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), free radical quenching, and X-ray photoelectron spectroscopy (XPS) were used to elucidate the mechanism of the catalytic decomposition of CaO₂, radical formation and DEP degradation in the presence of by pyrite. The results show that hydroxyl radicals (OH) are the dominant active species responsible for DEP degradation. Surface or lattice Fe(II) of FeS₂ readily activates H₂O₂ generated by CaO₂ decomposition to produce OH, while the reducing sulfur species of FeS₂ promotes the regeneration of surface of Fe(II) that catalyzes the production of additional OH, leading to the efficiently oxidative degradation of DEP. Although high concentration of common anions, such as Cl^-, NO₃^-, SO₄^2-, and HCO₃^-, exert inhibitory effects on DEP degradation by pyrite/CaO₂, the reaction system can still efficiently degrade DEP in realistic soil. It was observed that 78% of DEP (25 mg kg^-1) was degraded by 2.5% CaO₂ (w/w) and 0.5% FeS₂ (w/w) within 24 h. These results provide new insight into the mechanistic processes of CaO₂ activation and OH formation by the novel FeS₂ catalyst, demonstrating a promising alternative to the traditional H₂O₂-base Fenton process for contaminated soil remediation.

Impact of different environmental particles on degradation of dibutyl phthalate in coastal sediments with and without Cylindrotheca closterium

This study investigated the impact of different environmental particles at different concentrations (0.2% and 2%, w/w) on biodegradation of dibutyl phthalate (DBP) in sediments with and without Cylindrotheca closterium, a marine benthic diatom. The particles included biochar pyrolyzed at 400 °C, multi-walled carbon nanotube (MWNT), nanoscale zero-valent iron (nZVI) and polyethylene microplastic. In treatments without C. closterium, inhibition effect of the particles on degradation percentage of DBP (up to 15.7% decrement except 1.7% increment for 0.2% nZVI) increased with the increase of particle sorption ability to DBP and particle concentration in general. The results of 16s rDNA sequencing showed that C. closterium was probably the most abundant DBP-degrader, accounting for 20.0-49.3% of the total taxon read numbers. In treatments with C. closterium, inoculation of C. closterium increased the degradation percentage of DBP in all treatments with particle addition by 0.0-11.3%, which increased with the increase of chlorophyll a content in general but decreased with the increase of particle concentration from 0.2% to 2%. The increment was the highest for treatment with 0.2% nZVI addition due to its highest promotion effect on algal growth. In contrast, the increment was the lowest for treatments with MWNT addition due to its strong sorption to DBP and strong inhibition on the growth of C. closterium. Our findings suggested that the environmental particles could influence bioavailability of DBP by sorption and biomass of C. closterium, and thus degradation of DBP in sediments.

Spatial distribution of phthalate esters and the associated response of enzyme activities and microbial community composition in typical plastic-shed vegetable soils in China

The widespread use of phthalate esters (PAEs) in plastic products has made them ubiquitous in environment. In this study, 93 soil samples were collected in 31 plastic-sheds from one of China's largest vegetable production bases, Shouguang City, Shandong Province, to investigate the pollution characteristics and composition of PAEs in soils. Eleven PAEs were detected in the soil samples with the total concentration of 756-1590 μg kg^-1 dry soil. Di (2-ethylhexyl) phthalate (DEHP), bis (2-n-butoxyethyl) phthalate (DBEP), di-isobutyl phthalate (DiBP) and di-n-butyl phthalate (DBP) were the main pollutants with the highest concentrations. Moreover, soil properties, including pH, total organic carbon (TOC), soil enzyme activities, and soil microbial community characteristics, were monitored to explore the associated formation mechanisms. The concentration of PAEs in the plastic-shed vegetable soils was regionalized and the contamination degree in different regions was related to soil microbial characteristics and soil enzyme activities. Phthalate ester is positively correlated with catalase and sucrase, and negatively correlated with dehydrogenase and urease. Furthermore, some tolerant and sensitive bacteria were selected, which possibly could be used as potential indicators of PAE contamination in soil. Dimethyl phthalate (DMP) and DBP also had greater effects on the soil microbial community than other PAEs. The results will provide essential data and support the control of PAEs in plastic-shed vegetable soils in China.

Screening the main factors affecting phthalate esters adsorption on soils, humic acid, and clay organo-mineral complexes

Phthalate esters (PAEs) are one of the most frequently detected organic pollutants in soils. In this work, the adsorption behaviors of di-ethyl phthalate (DEP) and dibutyl phthalate (DBP) on soils, humins (HM) and Clay organo-mineral complexes (Clay-OM) from four regions in China, Changchun (CC), Cangzhou (CZ), Yinchuan (YC), and Changsha (CS) were studied. The surface and structural properties of these sorbents were characterized using Brunauer-Emmett-Teller specific surface area, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, and ¹³C nuclear magnetic resonance methods. The results showed that the CC soil has the largest pore volume (PV) and specific surface area (SSA). PV, SSA, and aliphatic carbon content of the samples ranked as Clay-OM > HM > soil. Adsorption experiments indicated that the Clay-OM exhibited the strongest adsorption affinity for both DBP and DEP, followed by HM, and then the soil samples. Furthermore, DEP and DBP adsorption amounts on the samples declined as follows: CC > CS > CZ > YC. To illustrate the dominant mechanisms for PAEs adsorption onto soil, the soil organic carbon content normalized adsorption coefficient (LogK_oc) was correlated with several possible parameters using multiple parameter linear regression and significance testing. The R² values of the DBP and DEP in multi-regression equations were 0.825 and 0.741 respectively, and the significance test suggested that pore structure and specific surface area had crucial influences on the adsorption progress.

Mechanistic studies of congener-specific adsorption and bioaccumulation of polycyclic aromatic hydrocarbons and phthalates in soil by novel QSARs

Polycyclic aromatic hydrocarbons (PAHs) and phthalic acid esters (PAEs) which are structurally featured with one or more aromatic skeletons are often regarded as two important groups of organic pollutants due to the widespread distribution and notorious toxic effects in soils. Relative to the great number of structural analogues or congeners detected in soil, however, the soil adsorption and bioaccumulation of PAHs/PAEs by plant is far less studied for the insufficiency of experimental determinations or lack of insights into the inherent structural requirements. To mechanistically evaluate the congener-specific soil adsorption and bioaccumulation for PAHs/PAEs, the quantitative structure-activity relationships (QSARs) were successfully developed by density functional theory (DFT) computation and partial least squares (PLS) analysis. As verified with the higher cumulative variance coefficients and cross-validated correlation coefficients for strong stability, interpretability and predictability, the QSARs could be used for prediction of unknown adsorption potency or bioavailability within the specified applicability domain, respectively. It was indicated by QSAR that the structural requirements of PAHs/PAEs necessary for strengthening the soil adsorption were mainly attributed to the molecular polarizability and the associated dispersion interaction with soil. As regards the bioaccumulation by carrot, the aggravation of spherical polarity change of molecules and the involved electrostatic interaction with soil entity or electron transfer from the highest occupied molecular orbital (HOMO) of PAHs/PAEs was implied to be inherently decisive for the variance of bioavailability among congeners. Based on the holistic view of negative correlation relationship, the soil adsorption seemed to act as the forceful constraint in decreasing the bioaccumulation of PAHs/PAEs and could also be alternatively gauged as the preliminary evaluation of bioavailability and risks on soil ecosystem. It would thus help better understand the soil adsorption and bioaccumulation with the informative mechanistic insights and provide data support for ecological risk assessment of PAHs/PAEs in soils.

Major factors dominating the fate of dibutyl phthalate in agricultural soils

Dibutyl phthalate (DBP) is a ubiquitous soil contaminant. We have investigated the sorption, degradation and residue of DBP in 20 types of agricultural soils and aimed to identify the major soil properties that dominate the fate of DBP. Sorption isotherms of DBP in all soils were fitted well with the Freundlich model. The sorption coefficient (K_f) varied between 3.99 and 36.1 mg^1-1/nL^1/n/kg. Path analysis indicated that 59.9% of variation in K_f could be explained by the combination of pH, organic carbon (OC) and clay content. Degradation of DBP in the 20 soils was well described by the first-order kinetic model, with half-lives (t_1/2) ranging from 0.430 to 4.99 d. The residual DBP concentration after 60 d of incubation (R₆₀) ranged from 0.756 to 2.15 mg/kg and the residual rates ranged from 3.97% to 9.63%. The K_f value was significantly positively correlated with t_1/2 and R₆₀. Moreover, soil pH, microbial biomass carbon (C_mic) and OC were identified as dominating factors that explained 84.4% of variation in t_1/2. The R₆₀ data indicated 72.2% of its variability attributable to the combination of OC and C_mic. The orders of the relative importance of dominating factors on the K_f, t_1/2 and R₆₀ were OC > pH > clay, C_mic > pH > OC and OC > C_mic, respectively. This work contributes to better understand the fate of DBP in soils and make scientific decisions about accelerating its dissipation in different soils.

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.

Derivation of aquatic life criteria for four phthalate esters and their ecological risk assessment in Liao River

As a critical family of endocrine disruptors, phthalate esters (PAEs) attracted considerable attentions due to increasingly detected worldwide. Aquatic life criteria (ALC) for PAEs are crucial for their accurate ecological risk assessment (ERA) and have seldom been derived before. Given this concern, the purpose of the present study is to optimize the ALCs of four priority PAEs to estimate their ecological risks in Liao River. Reproductive endpoint was found to be more sensitive than other endpoints. Thus, reproduction related toxicity data were screened to derive ALCs applying species sensitivity distribution (SSD) method. ALCs of DEHP, DBP, BBP and DEP were calculated to be 0.04, 0.62, 4.71 and 41.9 μg L^-1, which indicated decreased toxicity in sequence. Then, the derived ALCs of the four PAEs were applied to estimate their ecological risks in Liao River. A total of 27 sampling sites were selected to detect and analyze the exposure concentrations of PAEs. ERA using the hazard quotient (HQ) method was conducted. The results demonstrated that DEHP exhibited higher risks at 92.6% of sampling sites, and risks posed by DBP were moderate at 63.0% sampling sites. However, risks posed by BBP were low at 70.4% of sampling sites, and there were no risks posed by DEP at 96.3% of sampling sites. The results of probabilistic ecological risk assessment (PERA) indicated that probabilities of exceeding effects thresholds on 5% of species were 60.41%, 0%, 0.12%, 14.28% for DEHP, DEP, BBP and DBP, respectively. The work provides useful information to protect aquatic species in Liao River.

Estrogenic Active Stilbene Derivatives as Anti-Cancer Agents: A DFT and QSAR Study

Exploring different quantum chemical quantities for lead compounds is an ongoing approach in identifying crucial structural activity related features that are contributing into their biological activities. Herein, activity-related quantum chemical calculations were performed for the selected estrogenic stilbene derivatives using density functional theory (DFT) with B3LYP functional and 6-311++G** basis set. In addition, specific activity-related geometry-independent drug-like properties are discussed for these derivatives. To obtain the mathematical model that correlates the chemical descriptors with their measured estrogenic activities, the quantitative structure activity relationship (QSAR) is established using multiple linear regression (MLR) and support vector regression (SVR) methods. Satisfactory fit with a reasonable regression correlation coefficient (${\rm{R}}^{2}= 0.78$R2=0.78) between predicted and experimental $pEC_{50}$pEC50 values is observed using MLR method. The present study identifies the essential physicochemical descriptors that effectively contribute in the estrogenic activity. The applied approach provides helpful insight into the designing novel estrogenic agents with improved anticancer activities.

Toxicity of phthalate esters to lettuce (Lactuca sativa) and the soil microbial community under different soil conditions

Phthalate esters (PAEs) are globally used plasticizers and typical endocrine disruptors that can readily accumulate in agricultural products and represent a substantial risk to human health via the food chain. The range of soil properties has an important influence on the expression of PAE toxicity, and the mechanisms by which soil physical and chemical properties affect the expression of toxicity of target PAEs to plants and microorganisms requires further investigation. Important soil factors affecting the eco-toxicological effects of two typical PAEs, di-n-butyl phthalate (DnBP) and bis (2-ethylhexyl) phthalate (DEHP), on lettuce (Lactuca sativa) in a spiked soil were investigated in the present study. Soil at various pH values was spiked with three PAE concentrations (1, 5 and 20 mg DnBP or DEHP kg-1 soil), organic matter contents and water holding contents to simulate the greenhouse soil environment for 30 days. Their influence on the biomass, photosynthetic pigment contents, various physiological changes and soil microbial communities was determined as endpoints. The toxicity to lettuce of DnBP was higher than that of DEHP in the soil and soil pH was the most important factor affecting their single toxicity, followed by soil organic matter content and soil moisture content in agreement with the Biolog test results. Under different soil conditions total protein, total soluble sugar and free amino acid contents were positively correlated with concentrations of the target PAEs, but leaf area, biomass, •O2- activity, vitamin C content and soil microbial diversity indices showed the opposite trend. Chlorophyll a and carotenoid contents were more inhibited by DnBP together with impacts on indices of soil microbial diversity. The results suggest that soil conditions in greenhouses directly explain the patterns of pollutant toxicity displayed and impact the quantity, quality and food safety of vegetables produced using highly intensive production systems.

How do root exudates of bok choy promote dibutyl phthalate adsorption on mollisol?

This study investigates the interaction between the bok choy root exudates and dibutyl phthalate (DBP) onto mollisol during the adsorption. The result elucidated that the adsorption reached equilibrium within 12 h, the adsorption capacity of rhizosphere mollisol containing root exudates and ordinary mollisol were 243.46 mg kg^-1 and 281.95 mg kg^-1, separately. The adsorption kinetics and isotherm model followed the pseudo-second order and the Frendlish model, respectively, which hinted that the adsorption process was multi-layer heterogeneous chemisorption. We characterized the root exudates and analyzed its effects on soil physical and chemical properties and structure. The result revealed that the root exudates contained hydrocarbons, sulfur compounds and acids. Root exudates made the dissolved organic matter (DOM) dissolution from soil and the increase of organic matter, which might be one of the reasons that root exudates promote DBP adsorption on mollisol. We selected three-dimensional excitation-emission matrix (3D-EEM), synchronous fluorescence and Fourier transform infrared spectroscopy (FTIR) to analyze the interactions between root exudates and DBP, DOM and DBP, respectively. Fluorescence spectrum revealed that the main component of root exudates was protein, for DOM was humic acid, the fluorescence of root exudates and DOM gradually disappeared with the increase of DBP concentration. FTIR revealed that -COO in root exudates and -CH₂ in DOM respectively reacted with DBP. The results of this study are of great importance to reveal that the root exudates are significant in the environmental behavior of DBP adsorption on mollisol, and also provide more useful information for phytoremediation of organic pollutants in the mollisol.

Extraneous dissolved organic matter enhanced adsorption of dibutyl phthalate in soils: Insights from kinetics and isotherms

The widespread use of plastic film, especially in agricultural practices, has resulted in phthalic acid esters (PAEs) pollution, which poses risks for greenhouse soils. Application of composted manure is a common agricultural practice that adds extraneous dissolved organic matter (DOM) to the soil, however, the effect of extraneous DOM on the behavior of PAEs in agricultural soil is not clear. Dibutyl phthalate (DBP) was used as a model compound to investigate the effect and mechanism of extraneous DOM on the adsorption kinetics and isotherms of PAEs in two types of soils, through batch experiments and characterization of extraneous DOM and soils using fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The equilibrium adsorption amount of DBP in black soil was higher than in red soil regardless of the presence of extraneous DOM, due to the higher organic matter content of black soil. Hydrophobic partition played a dominant role in the DBP adsorption process of soils with and without extraneous DOM. The addition of DOM enhanced the adsorption capacity of DBP through partition in the two soils, especially at high DBP concentrations. Additions of a lower concentration of DOM better enhanced the adsorption effect than the higher concentrated DOM, due to an increase in water solubility of DBP resulted from excessive extraneous DOM in aqueous phase. Differences in mineral composition of soils led to diverse adsorption mechanisms of DBP as affected by additions of extraneous DOM. The FTIR spectra indicated that the intra-molecular and intermolecular hydrogen bond interactions of carboxylic acids, aromatic CC and CO in amides were involved in DBP adsorption in soils. Therefore, addition of DOM may increase adsorption of DBP in soils and thus influence its bioavailability and transformation in soils.

QSPR modeling of the logKow and logKoc of polymethoxylated, polyhydroxylated diphenyl ethers and methoxylated-, hydroxylated-polychlorinated diphenyl ethers

In the present study, the structural parameters of 209 types of polymethoxylated diphenyl ethers (PMeODEs), 209 types of polyhydroxylated diphenyl ethers (PHODEs), seven types of methoxylated-polychlorinated diphenyl ethers (MeO-PCDEs) and seven types of hydroxylated-polychlorinated diphenyl ethers (HO-PCDEs) were calculated using the Gaussian 09 program at the B3LYP/6-311G** level. Using structural and positional parameters as descriptors, quantitative structure-property relationships (QSPR) models for the prediction of n-octanol/water partition coefficient (logK_ow) and soil sorption coefficient normalized to organic carbon (logK_oc) were established and verified. The position parameters N₂₍₆₎, N₃₍₅₎ and N₄ were the main positional factors influencing logK_ow and logK_oc of PMeODEs and PHODEs. The molecular polarizability α was entered into the QSPR models of the logK_ow and logK_oc of PMeODEs, PHODEs and MeO/HO-PCDEs, indicating that the molecular volume could influence the two environment-related properties of DEs significantly. All of the established QSPR models showed good goodness-of-fit, robustness, and predictive ability. The two models for all of the tested DEs are slightly inferior compared with the models for only a class of compounds. In addition, application domain analysis indicated that the models reliably predicted the logK_ow and logK_oc of the mon- to hexa-DEs.

Bamboo- and pig-derived biochars reduce leaching losses of dibutyl phthalate, cadmium, and lead from co-contaminated soils

Biochar effect on the potential mobility of dibutyl phthalate (DBP), cadmium (Cd), and lead (Pb) in co-contaminated soils is not well investigated. A laboratory leaching study was conducted to evaluate the effect of biochars derived from bamboo (BB) and pig (PB) on the leachability of DBP, Cd, and Pb through soil columns packed with two soils with low or high organic carbon content (LOC; 0.35% C: HOC; 2.24% C) and spiked with DBP, Cd, and Pb. Application of PB to the LOC soil significantly (P < 0.05) reduced the leaching loss by up to 88% for DBP, 38% for Cd, and 71% for Pb, whereas its impact was insignificant in the HOC soil. The higher efficacy of PB in reducing the leaching of DBP, Cd, and Pb in the LOC soil than that of BB might be related to PB's higher specific surface area, surface alkalinity, pH, and mineral contents compared to those of BB. Co-contamination of Cd and Pb enhanced leaching of DBP in the LOC soil treated with PB, possibly by competition for the sorption sites. Leaching of DBP, Cd, and Pb were significantly (P < 0.05) higher in the LOC soil than in the HOC soil. This study revealed that the effectiveness of biochars was dependent on the soil organic carbon content. Application of PB to the LOC soil was effective in reducing the leaching risk of DBP, Cd, and Pb.

Adsorption of polar organic molecules on sediments: Case-study on Callovian-Oxfordian claystone

The release and transport of anthropogenic organic matter through the geosphere is often an environmental criterion of safety. Sedimentary rocks are widely studied in this context as geological barriers for waste management. It is the case of Callovian-Oxfordian claystone (COx), for which several studies report adsorption of anthropogenic organic molecules. In this study, we evaluated and reviewed adsorption data of polar organic molecules on COx claystone. Experiments were performed on raw claystone, decarbonated and clay fractions. Adsorption isotherms were measured with adsorbates of various polarities: adipate, benzoate, ortho-phthalate, succinate, gluconate, oxalate, EDTA, citrate. A significant adsorption was observed for multidentate polycarboxylic acids as evidenced with phthalate, succinate, oxalate, gluconate, EDTA and citrate (R_d = 1.53, 3.52, 8.4, 8.8, 12.4, 54.7 L kg^-1 respectively). Multiple linear regression were performed as a statistical analysis to determine the predictors from these adsorption data. A linear correlation between adsorption data (R_d) and dipole moment (μ) of adsorbates was evidenced (R² = 0.91). Molecules with a high dipole moment, μ(D) > 2.5, displayed a significant adsorption, R_d≫1 L kg^-1. A qualitative correlation can be easily estimated using the water/octanol partition coefficient, P_ow, of adsorbates (R² = 0.77). In this case, two opposite trends were distinguished for polar and apolar molecules. The use of organic carbon content in sediments is relevant for predicting adsorption of apolar compounds, log (P_ow)>+1. The oxides/clays contents may be relevant regarding polar molecules, log (^apparentP_ow)<-1. The proposed scheme offers a general methodology for investigation of geo-barriers towards heterogeneous organic plumes.

Biosorption of diethyl phthalate ester by living and nonliving Burkholderia cepacia and the role of its cell surface components

In this study, the dibutyl phthalate (DBP) binding properties of a DBP-tolerant bacterium (B. cepacia) were characterized in terms of adsorption kinetics and isotherm. Living and nonliving cells both exhibited rapid removal of DBP, achieving more than 80% of maximum sorption within 30 min of contact and reached the equilibrium after 3 h. The adsorption isotherms were well fitted with the Sips model and the nonliving cells have greater biosorption capacity and affinity for DBP than the living cells. Furthermore, the absence of an active mechanism dependent on metabolism implied that the DBP bioaccumulation by living cells was mainly attribute to passive surface binding. The optimum pH for DBP adsorption by living and nonliving cells were both observed to be 6.0. The biosorptive mechanism of DBP binding by B. cepacia was further confirmed by FTIR analysis and various chemical treatments. FTIR results indicated that the phosphate and CH₂ groups on B. cepacia were the main bounding sites for DBP. Furthermore, 2.28, 2.15, 1.93 and 0.87 g of pretreated cells were obtained from 2.40 g of native cells via extracellular polymeric substances (EPS), superficial layer-capsule, lipids components and cell membrane removal treatments, respectively. Total binding amount of DBP on the native cells, EPS-removed cells, capsule-removed cells, lipids-extracted cells and membrane-removed cells were 26.69, 24.84, 24.93, 16.11 and 10.80 mg, respectively, suggesting that the cell wall lipids, proteins or peptidoglycan might play important roles in the sorption of DBP by B. cepacia. The information could be applied in understanding on the mobility, transport and ultimate fate of PAEs in soil and related environment.