Accumulation and translocation of traditional and novel organophosphate esters and phthalic acid esters in plants during the whole life cycle

Plant endophytic bacteria reduce phthalates accumulation in soil-crop-body system: a review

Phthalate esters (PAEs) represent a class of widely utilized plasticizers, resulting in their pervasive presence in soil and agricultural crops, which poses significant risks to human health. This review examines the current state of PAE pollution, the microbial resources available for PAE degradation, and the associated degradation pathways. It highlights the advantages of endophytic bacteria over environmental microorganisms, including the prolonged survival of inoculated strains, in vivo biodegradation of PAEs, and multifunctional capabilities. Furthermore, the mechanisms by which endophytic bacteria mitigate PAE accumulation across the three defense lines (soil, crops, and the human body) are elucidated. The integrated approach of employing both plants and microbial agents for the remediation of PAEs demonstrates considerable potential for ensuring the safety of agricultural products and safeguarding human health. This work offers new insights into addressing the challenges posed by organic pollutant contamination and reducing PAE accumulation in the human body.

Plasticizers: distribution and impact in aquatic and terrestrial environments

Plasticizers, essential additives for enhancing plastic properties, have emerged as significant environmental and health concerns due to their persistence and widespread use. This study provides an in-depth exploration of plasticizers, focusing on their types, structures, properties, production methods, environmental distribution, and associated risks. The findings reveal that petroleum-based phthalates, particularly di-(2-ethylhexyl) phthalate (DEHP), are prevalent in aquatic and terrestrial environments, primarily due to the gradual degradation of plastic polymers. In the analysis of 39 studies on water contamination during the period of 2022-2023, only 22 works could be extracted due to insufficient details on the numerical value of plasticizer concentrations. Similarly, soil and sediment contamination studies were fewer, with only 11 studies focusing on sediments. These studies reveal that high plasticizer concentrations, notably in industrial and urban areas, often exceed recommended environmental limits, posing risks to ecological integrity and human health through bioaccumulation. Bioaccumulation of these compounds in soil and water could negatively affect the microbial communities, nutrient cycling, and could destabilize the overall ecological integrity. Concerns about their direct uptake by plants and potential risks to human health and food safety are highlighted in this study due to the high concentrations exceeding the threshold values. The review evaluates current treatment technologies, including metal-organic frameworks, electrochemical systems, multi-walled carbon nanotubes, and microbial degradation, noting their potential and challenges related to cost and energy consumption. It underscores the need for improved detection protocols, cost-effective treatments, stricter regulations, public awareness, and collaborative research to mitigate the adverse impacts of plasticizers on ecosystems and human health.

Revealing the bioavailability and phytotoxicity of different particle size microplastics on diethyl phthalate (DEP) in rye (Secale cereale L.)

Understanding how widely distributed microplastics (MPs) and diethyl phthalate (DEP) interact with crops remains limited, despite their significant implications for human exposure. We used physiology, transcriptomics, adsorption kinetics, and computational chemistry to assess rye's molecular response to two sizes of MPs (200 nm and 5 µm) and DEP, both individually and in combination. Findings systematically highlight potential ecological risks from MPs and DEP, with ecotoxicity ranking as follows: CK (Control Check) < LMPs < SMPs < DEP < LMPs+DEP < SMPs+DEP. Fluorescence and scanning electron microscopy revealed SMP's translocation ability in rye and its potential to disrupt leaf cells. DEP increased the electronegativity on MPs, which enhanced their uptake by rye. DEP adsorption by MPs in hydroponics reduced DEP bioavailability in rye (18.17-46.91 %). Molecular docking studies showed DEP interacted with chlorophyll, superoxide dismutase, and glutathione S-transferases proteins' active sites. Transcriptomic analysis identified significant up-regulation of genes linked to mitogen-activated protein kinase signaling, phytohormones, and antioxidant systems in rye exposed to MPs and DEP, correlating with physiological changes. These findings deepen the understanding of how MPs can accumulate and translocate within rye, and their adsorption to DEP raises crop safety issues of greater environmental risk.

Characteristics, prediction, and risk assessment of phthalates, organophosphate esters, and polycyclic aromatic hydrocarbons in vegetables from plastic greenhouses of Northeast China

We investigated the contaminations of phthalates (PAEs), organophosphate esters (OPEs), and polycyclic aromatic hydrocarbons (PAHs) in the vegetables and their corresponding soils from 26 plastic greenhouses of Northeast China. PAEs, OPEs, and PAHs in the edible portion of vegetables were in the range of 2620-21800, 115-852, and 32.4-602 ng/g, while the levels of these chemicals in the greenhouse soils were 5770-18800, 196-935, and 109-1600 ng/g, respectively. PAEs are the main organic pollutants in greenhouses, which were 1-2 orders of magnitude higher than that of OPEs and PAHs. Leafy vegetables showed the highest contamination level, which is ∼1-3 times that of root and fruit vegetables. Bioaccumulation factors (BAFs) of chemicals are significantly negatively correlated with their physicochemical properties, e.g., octanol-water partition coefficient and organic carbon partition coefficient. The partition-limited model can accurately predict the contamination level of greenhouse vegetables to a certain extent based on the chemical's concentration in the corresponding soil. We assessed the hazard quotients of target compounds through daily intake of greenhouse vegetables, and found a low risk for di(2-ethylhexyl) phthalate. This research emphasized the potential dietary exposure risks caused by greenhouse leafy vegetables, and proposed a method for evaluating the risk of greenhouse vegetables through soil monitoring.

Traditional and Novel Organophosphate Esters in Plastic Greenhouse: Occurrence, Multimedia Migration, and Exposure Risk via Vegetable Consumption

The migration and risk of organophosphate esters (OPEs) in agricultural air-soil-plant multimedia systems due to plastic film application remain unclear. This study investigates the multimedia distribution of traditional OPEs (TOPEs), novel OPEs (NOPEs), and their transformation products (POPEs) in plastic and solar greenhouses. The total concentration of OPE-associated contaminants in air and airborne particles ranged from 594 to 1560 pg/m3 and 443 to 15600 ng/g, respectively. Significant correlations between air OPE concentrations and those in polyolefin film (P < 0.01) indicate plastic film as the primary source. Contaminants were also found in soils (96.8-9630 ng/g) and vegetables (197-7540 ng/g). The primary migration pathway for NOPEs was particle dry deposition onto the soil and leaf, followed by plant accumulation. Leaf absorption was the main uptake pathway for TOPEs and POPEs, influenced by vegetable specific leaf surface area. Moreover, total exposure to OPE-associated contaminants via vegetable intake was assessed at 2250 ng/kg bw/day for adults and 2900 ng/kg bw/day for children, with an acceptable hazard index. However, a high ecological risk was identified for NOPE compounds (median risk quotient, 975). This study provides the first evidence of the multimedia distribution and potential threat posed by OPE-associated contaminants in agricultural greenhouses.

The dissipation of organophosphate esters mediated by ryegrass root exudate oxalic acid in soil: Analysis of enzymes activities, microorganism

Complex rhizoremediation is the main mechanism of phytoremediation in organic-contaminated soil. Low molecular weight organic acids (LMWOAs) in root exudates have been shown to increase the bioavailability of contaminants and are essential for promoting the dissipation of contaminants. The effects of root exudates on the dissipation of organophosphate esters (OPEs) in soil are unclear. Consequently, we studied the combined effects of root exudates, soil enzymes and microorganisms on OPEs (tri (1-chloro-2-propyl) phosphate (TCPP) and triphenyl phosphate (TPP)) dissipation through pot experiments. Oxalic acid (OA) was confirmed to be the main component of LMWOAs in root exudates of ryegrass. The existence of OA increased the dissipation rate of OPEs by 6.04%-25.50%. Catalase and dehydrogenase activities were firstly activated and then inhibited in soil. While, urease activity was activated and alkaline phosphatase activity was inhibited during the exposure period. More bacteria enrichment (e.g., Sphingomonas, Pseudomonas, Flavisolibacter, Pontibacter, Methylophilus and Massilia) improved the biodegradation of OPEs. In addition, the transformation paths of OPEs hydrolysis and methylation under the action of root exudates were observed. This study provided theoretical insights into reducing the pollution risk of OPEs in the soil.

Single injection by LC-ESI-MS/MS for simultaneous determination of organophosphate tri- and di-esters in plant tissue based on ultrasonic-assisted sequential extraction and single-step purification

A novel methodology based on ultrasonic-assisted sequential extraction, dispersive-SPE purification, and single-injection on liquid chromatography-tandem mass spectrometry (LC-MS/MS) is proposed, for the first time, to simultaneously measure 14 tri-OPEs and 9 di-OPEs in plant tissues. The samples were successively ultrasonicated with a mixture of hexane:dichloromethane (1:1, v/v) and 8% acetic acid in acetonitrile for extracting tri- and di-OPEs purified with graphitized carbon black and quantitated on LC-MS/MS at the same time. The recoveries of targeted tri- and di-OPEs in the matrix spike ranged from 66% to 120% and 71% to 110% respectively. The proposed method was validated by processing eight types of common vegetables including spinach (Spinacia oleracea L.), lettuce (Lactuca sativa), carrot (Daucus carota var. sativa Hoffm.), sweet potato (Solanum tuberosum L.), cucumber (Cucumis sativus L.), tomato (Solanum lycopersicum L.), green beans (Phaseolus vulgaris), and cowpeas (Vigna unguiculata), with the recoveries of surrogates ranging from 84% to 98%.

Uptake and accumulation of di(2-ethylhexyl) phthalate (DEHP) in a soil-ginseng system and toxicological mechanisms on ginseng (Panax ginseng C.A. Meyer)

Di(2-ethylhexyl) phthalate (DEHP) is regarded as a priority environmental pollutant. This study explored the adsorption and accumulation of DEHP within the ginseng-soil system and the mechanism of DEHP toxicity to ginseng (Panax ginseng C.A. Meyer). Under exposure to 22.10 mg/kg DEHP in soil, DEHP mainly accumulated in ginseng leaves (20.28 mg/kg), stems (4.84 mg/kg) and roots (2.00 mg/kg) after 42 days. The oxidative damage, metabolism, protein express of ginseng were comprehensively measured and analyzed. The results revealed that MDA presented an activation trend in ginseng stems and leaves after 42 days of DEHP exposure, while the opposite trend was observed for POD. Levels of ginsenoside metabolites Rg2, Rg3, Rg5, Rd, Rf and CK decreased in the ginseng rhizosphere exudates under DEHP stress. Further investigations revealed that DEHP disrupts ginsenoside synthesis by inducing glycosyltransferase (GS) and squalene synthase (SS) protein interactions. Molecular docking indicated that DEHP could stably bind to GS and SS by intermolecular forces. These findings provide new information on the ecotoxicological effect of DEHP on ginseng root.

Nontarget Identification of Novel Organophosphorus Flame Retardants and Plasticizers in Rainfall Runoffs and Agricultural Soils around a Plastic Recycling Industrial Park

Plastic recycling and reprocessing activities may release organophosphate ester (OPE) flame retardants and plasticizers into the surrounding environment. However, the relevant contamination profiles and impacts remain not well studied. This study investigated the occurrence of 28 OPEs and their metabolites (mOPEs) in rainfall runoffs and agricultural soils around one of the largest plastic recycling industrial parks in North China and identified novel organophosphorus compounds (NOPs) using high-resolution mass spectrometry-based nontarget analysis. Twenty and twenty-seven OPEs were detected in runoff water and soil samples, with total concentrations of 86.0-2491 ng/L and 2.53-199 ng/g dw, respectively. Thirteen NOPs were identified, of which eight were reported in the environment for the first time, including a chlorine-containing OPE, an organophosphorus heterocycle, a phosphite, three novel OPE metabolites, and two oligomers. Triphenylphosphine oxide and diphenylphosphinic acid occurred ubiquitously in runoffs and soils, with concentrations up to 390 ng/L and 40.2 ng/g dw, respectively. The downwind areas of the industrial park showed elevated levels of OPEs and NOPs. The contribution of hydroxylated mOPEs was higher in soils than in runoffs. These findings suggest that plastic recycling and reprocessing activities are significant sources of OPEs and NOPs and that biotransformation may further increase the ecological and human exposure risk.

Biomagnification and elimination effects of persistent organic pollutants in a typical wetland food web from South China

This study investigated the quantitative sources of persistent organic pollutants (POPs), their biomagnification factors, and their effect on POP biomagnification in a typical waterbird (common kingfisher, Alcedo atthis) food web in South China. The median concentrations of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in kingfishers were 32,500 ng/g lw and 130 ng/g lw, respectively. The congener profiles of PBDEs and PCBs showed significant temporal changes because of the restriction time points and biomagnification potential of different contaminants. The concentrations of most bioaccumulative POPs, such as CBs 138 and 180 and BDEs 153 and 154, decreased at lower rates than those of other POPs. Pelagic fish (metzia lineata) and benthic fish (common carp) were the primary prey of kingfishers, as indicated by quantitative fatty acid signature analysis (QFASA) results. Pelagic and benthic prey species were the primary sources of low and high hydrophobic contaminants for kingfishers, respectively. Biomagnification factors (BMFs) and trophic magnification factors (TMFs) had parabolic relationships with log K_OW, with peak values of approximately 7. Significant negative correlations were found between the whole-body elimination rates of POPs in waterbirds and the log-transformed TMFs and BMFs, indicating that the strong metabolism of waterbirds could potentially affect POP biomagnification.

Translocation and metabolism of tricresyl phosphate in rice and microbiome system: Isomer-specific processes and overlooked metabolites

Tricresyl phosphate (TCP) is extensively used organophosphorus flame retardants and plasticizers that posed risks to organisms and human beings. In this study, the translocation and biotransformation behavior of isomers tri-p-cresyl phosphate (TpCP), tri-m-cresyl phosphate (TmCP), and tri-o-cresyl phosphate (ToCP) in rice and rhizosphere microbiome was explored by hydroponic exposure. TpCP and TmCP were found more liable to be translocated acropetally, compared with ToCP, although they have same molecular weight and similar K_ow. Rhizosphere microbiome named microbial consortium GY could reduce the uptake of TpCP, TmCP, and ToCP in rice tissues, and promote rice growth. New metabolites were successfully identified in rice and microbiome, including hydrolysis, hydroxylated, methylated, demethylated, methoxylated, and glucuronide- products. The methylation, demethylation, methoxylation, and glycosylation pathways of TCP isomers were observed for the first time in organisms. What is more important is that the demethylation of TCPs could be an important and overlooked source of triphenyl phosphate (TPHP), which broke the traditional understanding of the only manmade source of toxic TPHP in the environment. Active members of the microbial consortium GY during degradation were revealed and metagenomic analysis indicated that most of active populations contained TCP-degrading genes. It is noteworthy that the strains and function genes in microbial consortium GY that responsible for TCP isomers' transformation were different. These results can improve our understanding of the translocation and transformation of organic pollutant isomers in plants and rhizosphere microbiome.

Bioaccumulation and emission of organophosphate esters in plants affecting the atmosphere's phosphorus cycle

The imbalance of atmospheric, terrestrial and aquatic phosphorus budgets remains a research conundrum and global concern. In this work, the uptake, distribution, bioaccumulation and emission of organophosphate esters (OPEs) by clove trees (Syzygium aromaticum), lemon trees (Citrus limon) and cape jasmine trees (Gardenia jasminoides var. fortuniana) was investigated as conduits for phosphorus transfer or sinks and sources. The objective was to assess the role OPEs in soils play as atmospheric phosphorus sources through plant bioaccumulation and emission. Results demonstrated OPEs in experimental soil plots ranging from 0.01 to 81.0 ng g^-1 dry weight, were absorbed and transported through plants to the atmosphere. The total emission of OPEs varied greatly from 0.2 to 588.9 pg g^-1 L^-1 h^-1, with a mean of 47.6 pg g^-1 L^-1 h^-1. There was a negative linear relationship between the concentrations of total phosphorus and four OPEs, tri-iso-butyl phosphate, tri-n-butyl phosphate, tris (2-chloroisopropyl) phosphate and tripentyl phosphate. Trimethyl phosphate levels were positively correlated with total nitrogen, and the concentrations of tri-iso-butyl phosphate, tri-n-butyl phosphate, tris (2-chloroisopropyl) phosphate and tripentyl phosphate decreased along with available potassium in leaves after 72 h. There was a significantly positive linear relationship between higher emission concentrations of OPEs and the emission factor of OPEs concentration (F = 4.2, P = 0.002), with lower emissions of OPEs and the bioaccumulation of OPEs in leaves (F = 4.8, P = 0.004). OPEs releases to the atmosphere were enriched in aerosols, and participate in atmospheric chemical reactions like photolysis, thereby affecting the phosphorus balance and cycling in the atmosphere.