Universal occurrence of organophosphate tri-esters and di-esters in marine sediments: Evidence from the Okinawa Trough in the East China Sea.

Despite numerous data on organophosphate tri-esters (tri-OPEs) in the environment, literatures on organophosphate di-esters (di-OPEs) in field environment, especially marine sediments remain scarce. This study addresses this gap by analyzing 35 abyssal sediment samples from the middle Okinawa Trough in the East China Sea. A total of 25 tri-OPEs and 10 di-OPEs were determined, but 13 tri-OPEs and 2 di-OPEs were nondetectable in any of these sediment samples. The concentrations of ∑12tri-OPE and ∑8di-OPE were 0.108-32.2 ng/g (median 1.11 ng/g) and 0.548-15.0 ng/g (median 2.74 ng/g). Chlorinated (Cl) tri-OPEs were the dominant tri-esters, accounting for 47.5 % of total tri-OPEs on average, whereas chlorinated di-OPEs represented only 19.2 % of total di-OPEs. This discrepancy between the relatively higher percentage of Cl-tri-OPEs and lower abundance of Cl-di-OPEs may be ascribed to the stronger environmental persistence of chlorinated tri-OPEs. Source assessment suggested that di-OPEs were primarily originated from the degradation of tri-OPEs rather than industrial production. Long range waterborne transport facilitated by oceanic currents was an important input pathway for OPEs in sediments from the Okinawa Trough. These findings enhance the understanding of the sources and transport of OPEs in marine sediments, particularly in the Okinawa Trough.

Widespread Occurrence and Transport of p-Phenylenediamines and Their Quinones in Sediments across Urban Rivers, Estuaries, Coasts, and Deep-Sea Regions.

p-Phenylenediamines (PPDs) are widely used as antioxidants in tire rubber, and their derived quinone transformation products (PPD-Qs) may pose a threat to marine ecosystems. A compelling example is N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD)-derived quinone, called 6PPD-Q, as the causal toxicant for stormwater-linked acute mortality toward coho salmon. However, the knowledge of the co-occurrences of PPDs and PPD-Qs and their transport from freshwater to oceanic waterbodies on a large geographical scale remains unknown. Herein, we performed the first large-scale survey of these chemicals in sediments across urban rivers, estuaries, coasts, and deep-sea regions. Our results demonstrated that seven PPDs and four PPD-Qs are ubiquitously present in riverine, estuarine, and coastal sediments, and most of them also occur in deep-sea sediments. The most dominant chemicals of concern were identified as 6PPD and 6PPD-Q. Total sedimentary concentrations of PPDs and PPD-Qs presented a clear spatial trend with decreasing levels from urban rivers (medians: 39.7 and 15.2 ng/g) to estuaries (14.0 and 5.85 ng/g) and then toward coasts (9.47 and 2.97 ng/g) and deep-sea regions (5.24 and 3.96 ng/g). Interestingly, spatial variation in the ratios of 6PPD to 6PPD-Q (R6PPD/6PPD-Q) also presented a clear decreasing trend. Our field measurements implied that riverine outflows of PPDs and PPD-Qs may be an important route to transport these tire rubber-derived chemicals to coastal and open oceans.

Prevalence of Novel and Traditional Synthetic Phenolic Antioxidants in Baby Food from China: A Dominant Pathway for Infant Exposure.

Synthetic phenolic antioxidants (SPAs) are a group of ubiquitous contaminants with multiple toxicities. However, current knowledge on the occurrence of SPAs in baby food and associated infant exposure is lacking. Herein, we analyzed three categories of baby food from China: infant formula, cereal, and puree, for a broad suite of 11 traditional and 19 novel SPAs. In addition to 11 traditional SPAs, up to 13 novel SPAs were detected in the baby food samples. The median concentrations of novel SPAs for infant formula, cereal, and puree were 604, 218, and 24.1 ng/g, respectively, surpassing those of traditional SPAs (53.4, 62.1, and 10.0 ng/g). The prevalent SPAs in the samples were butylated hydroxytoluene, 2,4-di-tert-butylphenol, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (AO 1010), and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (AO 1076). Source analysis indicated that the prevalence of these four SPAs in baby food was associated with contamination of packaging materials, mechanical processing, or raw ingredients. Migration experiments demonstrated that contamination of plastic packaging constituted an important source. Exposure assessment suggested that there may be no appreciable health risk posed by the SPAs in baby food. Even so, baby food consumption was still a dominant pathway for infant exposure to SPAs, with a higher contribution than breast milk consumption, dust ingestion, dermal dust absorption, and air inhalation, which requires special attention.

Underlying Degradation of Phthalates via Microbials in Dust from Different Microenvironments.

Phthalate monoesters (me-PAEs) have been used as biomarkers for assessing human exposure to phthalate esters (PAEs) for a long time, and studies on the sources and distribution of me-PAEs in the environment are limited. In this study, dust samples from microenvironments were collected to measure the occurrence of PAEs and me-PAEs, as well as the bacterial diversity. The results indicated that me-PAEs coexisted with PAEs in different microenvironmental dust samples, with concentrations of nine PAEs and 16 me-PAEs ranging from 108 to 1450 µg/g (median range) and 6.00 to 21.6 µg/g, respectively. The concentrations of several low molecular weight me-PAEs (e.g., monomethyl phthalate and monoethyl phthalate) in dust were even significantly higher than those of their parents. The bacteria in the dust were mainly predominant with Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes (total abundance >90%). Bacteria from bus and air conditioning dust samples had the highest species richness and species diversity. Seven genes of suspected enzymes with the ability to degrade PAEs were selected, and the concentration of me-PAEs increased with increasing abundance of enzyme function. Our findings will provide useful information on the profiles of me-PAEs and their potential sources in indoor dusts, which will benefit the accurate estimation of human exposure.

Identification of Fluorescent Brighteners as Another Emerging Class of Abundant, Ubiquitous Pollutants in the Indoor Environment.

Fluorescent brighteners (FBs) are extensively used as important chemical additives in multiple industrial fields worldwide. The history of the use of global FBs spans over 60 years, but knowledge on their environmental occurrence and risks remains largely unknown. Here, we screened indoor dust and hand wipes from South China for a broad suite of 17 emerging FBs using a new comprehensive analytical method. All 17 FBs were detected in the indoor environment for the first time, most of them having been rarely investigated or never reported in prior environmental studies. Ionic FBs were found to be more abundant than nonionic ones. The median total concentrations of the 17 detectable FBs reached 11,000 ng/g in indoor dust and 2640 ng/m2 in hand wipes, comparable to or higher than those of well-known indoor pollutants. Human exposure assessment indicated that hand-to-mouth contact is a significant pathway for exposure to FBs, with a comparable contribution to that of dust ingestion. Most of the newly identified FBs are predicted to have persistent, bioaccumulative, or toxic properties. Our work demonstrates that FBs are another class of highly abundant, hazardous, and ubiquitous indoor pollutants that have been overlooked for decades and points to an emerging concern.

Identification of Triazine UV Filters as an Emerging Class of Abundant, Ubiquitous Pollutants in Indoor Dust and Air from South China: Call for More Concerns on Their Occurrence and Human Exposure.

Triazine UV filters are an important class of UV filters, but knowledge on their environmental occurrence and human exposure remains largely unknown. In this study, we performed a targeted analysis of 17 emerging triazine UV filters in indoor dust and indoor air from South China based on a newly developed LC-MS/MS method. A total of 12 of the 17 emerging triazine UV filters were first positively detected in the dust and air samples. Ethylhexyl triazone (EHT) and bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT) were identified as the most abundant compounds. The median total concentrations of triazine UV filters reached 3860 ng/g in indoor dust and 1590 pg/m3 in indoor air. Gas-particle partitioning analysis showed that triazine UV filters were predominant in the particle phase in ambient air. Significant concentration correlations were observed among most triazine UV filters. The estimated daily intake of triazine UV filters through dust ingestion and air inhalation for toddlers under high-end exposure scenarios was up to 839 ng/kg bw/day, but a lack of toxic thresholds hampers accurate risk assessment. Our work highlights another emerging class of UV filters that significantly contribute to indoor chemical mixtures and expresses concerns over their occurrence and human exposure.

Microplastics in take-out food: Are we over taking it?

Take-out food has become increasingly prevalent due to the fast pace of people's life. However, few study has been done on microplastics in take-out food. Contacting with disposable plastic containers, take-out food may be contaminated with microplastics. In the present study, abundance and characteristics of microplastics in total of 146 take-out food samples including solid food samples and beverage samples (bubble tea and coffee) were determined and identified. The mean abundance of microplastics in take-out food was 639 items kg-1, with the highest value in rice and the lowest value in coffee. Fragments shape, transparent color and sizes ≤ 500 µm were the main characteristics of microplastics in those food, and polyethylene was the main polymer type. Our results indicated that microplastics in take-out food was influenced by food categories and cooking methods, as well as food packaging materials. Approximately 170-638 items of microplastics may be consumed by people who order take-out food 1-2 times weekly.

Use of glioma to assess the distribution patterns of perfluoroalkyl and polyfluoroalkyl substances in human brain.

Human brain has a complex structure and is able to perform powerful functions. Blood-brain barrier blocks the entry of foreign substances and maintains the homeostasis of the brain. However, some exogenous substances are still able to pass through the blood-brain barrier, with distribution patterns yet to be clarified. Perfluoroalkyl and polyfluoroalkyl substances (PFASs), including perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonic acids (PFSAs), a precursor (perfluorooctane sulfonamide that can be degraded to other substances), and emerging PFASs, were analyzed for the first time in living human brain glioma. The target compounds were detected and quantified in 25 out of 26 glioma samples. The concentration range of ∑PFAS was < RL-51 ng g-1 wet weight (applied to all reported concentrations), with a median of 2.9 ng g-1. The most abundant compound was PFCAs (40%), followed by PFSAs (28%), emerging PFASs (22%), and perfluorooctane sulfonamide (10%). Abundant alternatives PFASs, including short-chain PFCAs, short-chain PFSAs, and emerging PFASs (52% of ∑PFAS), were found in the glioma samples, supporting the notion that low molecular weight exogenous compounds have high permeability to cross the blood-brain barrier and accumulate in brain tissue. Gender difference was not significant (p > 0.05) in the concentrations of PFASs in the glioma samples. Concentrations of PFASs increased with increasing age, from 0.61 ng g-1 (0-14 years old) to 1.6 ng g-1 (>48 years old), with no significant linear correlation with age. The present study suggested that glioma is an effective indicator for monitoring exogenous contaminants in brain tissues.

Plastics Are an Insignificant Carrier of Riverine Organic Pollutants to the Coastal Oceans.

Global rivers act as a dominant transport pathway for land-based plastic debris to the marine environment. Organic pollutants (OPs) affiliated with riverine plastics can also enter the global oceans, but their amounts remain unknown. Microplastic (MP) samples were collected in a one-year sampling event from the surface water of the eight main riverine outlets in the Pearl River Delta (PRD), China, and analyzed for OPs affiliated with MPs, including 16 polycyclic aromatic hydrocarbons (PAHs), eight polybrominated diphenyl ethers (PBDEs), and 14 polychlorinated biphenyls (PCBs). The mean concentrations of MP-affiliated ∑16PAH, ∑8PBDE, and ∑14PCB were 2010 (range: 25-40,100), 412 (range: 0.84-14,800), and 67.7 (range: 1.86-456) ng g-1, respectively. Based on these and previous results, the annual riverine outflows of MP-affiliated OPs were 148, 83, and 8.03 g for ∑16PAH, ∑8PBDE, and ∑14PCB, respectively. Assuming that plastic debris of different sizes contained the same concentrations of the target pollutants as MPs, the mean riverine outflows of plastic-bound ∑16PAH, ∑8PBDE, and ∑14PCB were 6.75, 3.77, and 0.37 kg year-1, respectively, which were insignificant compared with the riverine outflows of OPs through riverine water discharge (up to hundred tons per year). Apparently, plastics are an insignificant carrier of riverine OPs to the coastal oceans.

Global Riverine Plastic Outflows.

Global marine plastic pollution, which is derived mainly from the input of vast amounts of land-based plastic waste, has drawn increasing public attention. Riverine plastic outflows estimated using models based on the concept of mismanaged plastic waste (MPW) are substantially greater than reported field measurements. Herein, we formulate a robust model using the Human Development Index (HDI) as the main predictor, and the modeled riverine plastic outflows are calibrated and validated by available field data. A strong correlation is achieved between model estimates and field measurements, with a regression coefficient of r2 = 0.9. The model estimates that the global plastic outflows from 1518 main rivers were in the range of 57,000-265,000 (median: 134,000) MT year-1 in 2018, which were approximately one-tenth of the estimates by MPW-based models. With increased plastic production and human development, the global riverine plastic outflow is projected to peak in 2028 in a modeled trajectory of 2010-2050. The HDI is a better indicator than MPW to estimate global riverine plastic outflows, and plastic pollution can be effectively assessed and contained during human development processes. The much lower global riverine plastic outflows should substantially ease the public's concern about marine plastic pollution and financial pressure for remediation.

Riverine Microplastic Pollution in the Pearl River Delta, China: Are Modeled Estimates Accurate?

Plastic pollution has caused increasing global concern. Currently, model estimates of the riverine plastic inputs to the global oceans based on the concept of Mismanaged Plastic Waste (MPW) varied substantially, and no field measurements of riverine inputs were available. We conducted sampling at the eight major river outlets of the Pearl River Delta, South China with rapid economic growth and urbanization to provide field measured data for fine-tuning modeling results. Floating microplastics (MPs) were collected with a Manta net (mesh size of 0.33 mm) five times during 2018. Microplastic particles (0.3-5.0 mm) widely occurred in all sampling sites. The number and mass concentrations of MPs were in the ranges of 0.005-0.7 particles m-3 and 0.004-1.28 mg m-3 and were positively correlated with water discharges. The annual riverine input of MPs from the Pearl River Delta was estimated at 39 billion particles or 66 tons, which converts to 2400-3800 tons of plastic debris based on calculations described in Text S2. These values were substantially below the MPW-based model estimates (91,000-170,000 tons). The large difference between measured and modeling results may have derived from the large uncertainty in the MPW values assigned to the world's countries/regions.

Impact of Polymer Colonization on the Fate of Organic Contaminants in Sediment.

Plastic pellets and microbes are important constitutes in sediment, but the significance of microbes colonizing on plastic pellets to the environmental fate and transport of organic contaminants has not been adequately recognized and assessed. To address this issue, low-density polyethylene (LDPE), polyoxymethylene (POM) and polypropylene (PP) slices were preloaded with dichlorodiphenyltrichloroethanes (DDTs), polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) and incubated in abiotic and biotic sediment microcosms. Images from scanning electron microscope, Lysogeny Broth agar plates and confocal laser scanning microscope indicated that all polymer slices incubated in biotic sediments were colonized by microorganisms, particularly the LDPE slices. The occurrence of biofilms induced higher dissipation rates of DDTs and PAHs from the LDPE slice surfaces incubated in the biotic sediments than in the abiotic sediments. Plastic colonization on LDPE slice surfaces enhanced the biotransformation of DDT and some PAHs in both marine and river sediments, but had little impact on PCBs. By comparison, PP and POM with unique properties were shown to exert different impacts on the physical and microbial activities as compared to LDPE. These results clearly demonstrated that the significance of polymer surface affiliated microbes to the environmental fate and behavior of organic contaminants should be recognized.

Polybrominated diphenyl ethers (flame retardants) in mother-infant pairs in the Southeastern U.S.

Polybrominated diphenyl ethers (PBDEs) are commonly used flame retardants in foams, building material, electronics, and textiles. These chemicals leach into the environment, where they persist, and are found today in virtually every population worldwide. Several studies in recent years have detected the presence of PBDEs in maternal and infant samples. However, few of these studies were conducted in the U.S., and few examined paired or matched mother blood-cord blood samples. We analyzed serum from 10 mother-infant pairs for the presence of PBDEs in a patient population in the Southeastern U.S. Out of 35 measured PBDE congeners, five (BDE-28, -47, -99, -100, and -153) were present, with detection frequencies of 65-100 %. The total PBDE concentrations in maternal and infant sera were highly correlated (r2 = 0.710, p = 0.0043). The levels of BDE-47, -99, and -100 and of total PBDEs were higher in the infant cord sera when compared with those in maternal sera (p < 0.017), suggesting that fetuses and neonates might have higher circulating concentrations of these potentially neurotoxic and endocrine disrupting chemicals compared with their mothers. The primary focus henceforward should be whether there are any deleterious effects from exposure to these chemicals on human health.

Hair and Nails as Noninvasive Biomarkers of Human Exposure to Brominated and Organophosphate Flame Retardants.

After the phase-out of polybrominated diphenyl ethers (PBDEs), the use of alternative flame retardants (AFRs), such as FireMaster 550, and of organophosphate esters (OPEs) has increased. However, little is known about human exposure to these chemicals. This lack of biomonitoring studies is partially due to the absence of reliable noninvasive biomarkers of exposure. Human hair and nails can provide integrated exposure measurements, and as such, these matrices can potentially be used as noninvasive biomarkers of exposure to these flame retardants. Paired human hair, fingernail, toenail, and serum samples obtained from 50 adult participants recruited at Indiana University Bloomington campus were analyzed by gas chromatographic mass spectrometry for 36 PBDEs, 9 AFRs, and 12 OPEs. BDE-47, BDE-99, 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB), di(2-ethylhexyl) tetrabromophthalate (TBPH), tris(1,3-dichloro-2-propyl)phosphate (TDCIPP), and triphenyl phosphate (TPHP) were the most abundant compounds detected in almost all hair, fingernail, and toenail samples. The concentrations followed the order OPEs > TBB+TBPH > Σpenta-BDE. PBDE levels in the hair and nail samples were significantly correlated with their levels in serum (P < 0.05), suggesting that human hair and nails can be used as biomarkers to assess human exposure to PBDEs.

Halogenated flame retardants in baby food from the United States and from China and the estimated dietary intakes by infants.

Three categories of baby food (formula, cereal, and puree) were bought from United States and Chinese stores in 2013 and analyzed for polybrominated diphenyl ethers (PBDEs) and related flame retardants. The primary goal of this project was to investigate whether there were differences in the levels of flame retardants between these two nations' baby foods. The median concentrations of total PBDEs (sum of BDE-17, -28, -47, -49, -99, -100, -153, -183, and -209) were 21 and 36 pg/g fresh weight for the Unites States and Chinese baby foods, respectively. Among non-PBDE flame retardants, hexabromobenzene, Dechlorane Plus (DP), and decabromodiphenylethane were frequently detected (22-57%) with median concentrations of 1.6, 8.7, and 17 pg/g fresh weight for United States samples, and 1.3, 13, and 20 pg/g fresh weight for Chinese samples. In general, the flame retardant concentrations in the United States and Chinese samples were not statistically different, but very high DP concentrations were observed in one Chinese formula sample (4000 pg/g) and in one United States cereal sample (430 pg/g), possibly suggesting contamination of the raw materials or contamination during production of these two samples. A comparison of median estimated daily dietary intake rates of BDE-47, -99, and -153 with existing reference doses for neurodevelopmental toxicity and other existing criteria suggested no concerns for the consumption of these baby foods.

A review on micro- and nanoplastics in humans: Implication for their translocation of barriers and potential health effects.

As emerging contaminants, micro- and nanoplastics (MNPs) can absorb and leach various toxic chemicals and ultimately endanger the health of the ecological environment and humans. With extensive research on MNPs, knowledge about MNPs in humans, especially their translocation of barriers and potential health effects, is of utmost importance. In this review, we collected literature published from 2000 to 2023, focusing on MNPs on their occurrence in humans, penetrating characteristics in the placental, blood-brain, and blood-testis barriers, and exposure effects on mammalian health. The characteristics and distributions of MNPs in human samples were analyzed, and the results demonstrated that MNPs were ubiquitous in most human samples, except for kidneys and cerebrospinal fluid. In addition, the phenomenon of MNPs crossing barriers and their underlying mechanisms were discussed. We also summarized the potential factors that may affect the barrier crossing and health effects of MNPs, including characteristics of MNPs, exposure doses, administration routes, exposure durations, co-exposure to other pollutants, and genetic predisposition. Exposure to MNPs may cause cytotoxicity, neurotoxicity, and developmental and reproductive toxicity in mammals. People are encouraged to reduce their exposure to MNPs to prevent these adverse health effects. Finally, we discussed the shortcomings of current research on MNPs in humans, providing a valuable reference for understanding and evaluating the potential health risks from MNP exposure in mammals, including humans.

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%.

Per- and polyfluoroalkyl substances (PFAS) exposure in plasma and their blood-brain barrier transmission efficiency-A pilot study.

Per- and polyfluoroalkyl substances (PFAS) have been shown to penetrate the blood-brain barrier (BBB) and accumulate in human brain. The BBB transmission and accumulation efficiency of PFAS, as well as the potential health risks from human co-exposure to legacy and emerging PFAS due to differences in transport efficiency, need to be further elucidated. In the present pilot study, 23 plasma samples from glioma patients were analyzed for 17 PFAS. The concentrations of PFAS in six paired brain tissue and plasma samples were used to calculate the BBB transmission efficiency of PFAS (RPFAS). This RPFAS analysis was conducted with utmost care and consideration amid the limited availability of valuable paired samples. The results indicated that low molecular weight PFAS, including short-chain and emerging PFAS, may have a greater potential for accumulation in brain tissue than long-chain PFAS. As an alternative to perfluorooctane sulfonic acid (PFOS), 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) exhibited brain accumulation potential similar to that of PFOS, suggesting it may not be a suitable substitute concerning health risk in brain. The BBB transmission efficiencies of perfluorooctanoic acid, PFOS, and 6:2 Cl-PFESA showed similar trends with age, which may be an important factor influencing the entry of exogenous compounds into the brain. A favorable link between perfluorooctane sulfonamide (FOSA) and the development and/or progression of glioma may be implicated by a strong positive correlation (r2 = 0.94; p < 0.01) between RFOSA and Ki-67 (a molecular marker of glioma). However, a causal relationship between RFOSA and glioma incidence were not established in the present study. The present pilot study conducted the first examination of BBB transmission efficiency of PFAS from plasma to brain tissue and highlighted the importance of reducing and/or controlling exposure to PFAS.

Anthropogenic activities have contributed moderately to increased inputs of organic materials in marginal seas off China.

Sediment has been recognized as a gigantic sink of organic materials and therefore can record temporal input trends. To examine the impact of anthropogenic activities on the marginal seas off China, sediment cores were collected from the Yellow Sea, the inner shelf of the East China Sea (ECS), and the South China Sea (SCS) to investigate the sources and spatial and temporal variations of organic materials, i.e., total organic carbon (TOC) and aliphatic hydrocarbons. The concentration ranges of TOC were 0.5-1.29, 0.63-0.83, and 0.33-0.85%, while those of Σn-C14-35 (sum of n-alkanes with carbon numbers of 14-35) were 0.08-1.5, 0.13-1.97, and 0.35-0.96 µg/g dry weight in sediment cores from the Yellow Sea, ECS inner shelf, and the SCS, respectively. Terrestrial higher plants were an important source of aliphatic hydrocarbons in marine sediments off China. The spatial distribution of Σn-C14-35 concentrations and source diagnostic ratios suggested a greater load of terrestrial organic materials in the Yellow Sea than in the ECS and SCS. Temporally, TOC and Σn-C14-35 concentrations increased with time and peaked at either the surface or immediate subsurface layers. This increase was probably reflective of elevated inputs of organic materials to marginal seas off China in recent years, and attributed partly to the impacts of intensified anthropogenic activities in mainland China. Source diagnostics also suggested that aliphatic hydrocarbons were mainly derived from biogenic sources, with a minority in surface sediment layers from petroleum sources, consistent with the above-mentioned postulation.

Analysis and subcellular distribution of organophosphate esters (OPEs) in rice tissues.

Recent studies have identified the ability of plants to uptake and translocate organophosphate esters (OPEs) within cells. In response to the increasing interest in OPEs and their occurrence in paddy fields and rice, the current study aimed to present an effective and sensitive GC-MS based methodology for quantitative determination of 11 OPEs with octanol-water coefficients ranging from 1.6 to 10. Rice was sonicated with hexane and dichloromethane, and fractionated on two columns: one consisting of neutral alumina, and neutral silica, and the other consisting of graphitized carbon black. Method precision was validated using spiked rice (n = 30) and procedural blanks (n = 9). The mean recovery of matrix spikes for all target OPEs were within 78-110% with relative standard deviation lower than 25%, with a few exceptions. This method was applied to process the wild rice (O. sativa) in which tri-n-propyl phosphate was the dominant targeted OPE. The recoveries of surrogate standards were 81 ± 17% for d12- tris(2-chloroethyl) phosphate and 95 ± 8.8% for 13C12- triphenyl phosphate. The developed method was further used to examine the recoveries of target OPEs in the subcellular structure of rice tissues, including cell wall, cell organelles, cell water-soluble fractions, and cell residue. Recoveries of most target OPEs were in the range of 50-150%; however, ion enhancement was observed for four OPEs in root and shoot tissues. Hydrophobic OPEs accumulated in the cell wall, cell residue, and cell organelles while chlorinated OPEs mainly distributed in the cell water-soluble fraction. These results provide new insight for the ecological risk assessment of OPEs in an important food staple.