Freezing-Induced Bromate Reduction by Dissolved Organic Matter and the Formation of Organobromine Compounds.

The freezing-induced acceleration of bromate reduction by humic substances (HS) contributes to HS bromination and the formation of organobromine compounds (OBCs). Herein, we report the enhanced reduction of bromate by dissolved organic matter and the formation of large amounts of OBCs in freezing solutions. After 48 h of freezing process, 78.1-100% of bromate was reduced by DOM at different initial concentrations of bromate and DOM in acidic solutions (pH 3 and 4). Bromide was one of the main reduction products, and it accounted for 30.9-47.8% of the total bromine content. Except for bromide, a large amount of OBCs formed by brominating DOM with reactive bromine species, like hypobromite, were detected. The conversion of bromate to OBCs, calculated as the total organobromine content to the initial bromate content, ranged from 28.2 to 52.5% and was mainly dependent on the bromate/DOM content. About 110-603 species of OBCs were detected by Fourier transform ion cyclotron resonance mass spectrometry, and they were primarily highly unsaturated and phenolic compounds. By analyzing the spectral variation before and after the freezing process, we found the disappearance of 900 compounds containing only C, H, and O with a low carbon oxidation state that was regarded as the main reductant of bromate. Our findings call for further investigation of the processes and the effects of bromate formation in aqueous environments.

Bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in wild marine fish from the coastal waters of the northern South China Sea: Risk assessment for human health.

Little data are available on polycyclic aromatic hydrocarbons (PAHs) in marine fish associated with oil and gas activities from the South China Sea (SCS). Twenty-one wild marine fish species from the northern South China Sea were collected for analysis of the presence of polycyclic aromatic hydrocarbons (PAHs). The total concentration of the PAHs (∑16PAHs) ranged from 199 to 606 ng·g-1 d.w., indicating moderate contamination. PAHs in fish species found in the Pearl River Delta (PRD) were significantly higher than those from the Yachen (YC) gas fields (p < 0.05). Planktivorous fish exhibited significantly higher concentrations of PAHs than carnivorous and omnivorous fish (p < 0.05). The PAHs were dominated by three ring compounds. Source identification analyses indicated that the PAH pollution originated from petroleum inputs. The cancer and non-cancer risk assessments concluded that the probable risk associated with the intake of PAHs via fish consumption is minimal. Long-term monitoring is necessary to determine the ecological impacts of PAHs associated with oil and gas activities.

Characterization of Brominated Disinfection Byproducts Formed During the Chlorination of Aquaculture Seawater.

Although brominated disinfection byproducts (Br-DBPs) have been reported to form from reactions between bromide, dissolved organic matter (DOM), and disinfectants, their formation during the disinfection of aquaculture seawater via chlorination has been rarely studied. Herein, after 5 days of disinfection of raw aquaculture seawater samples with sodium dichloroisocyanurate (NaDDC), trichloroisocyanuric acid (TCCA) and chlorine dioxide (ClO2), 181, 179, and 37 Br-DBPs were characterized by ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Sunlight irradiation of the chlorinated aquaculture seawater with TCCA and NaDDC was found to reduce the formation of Br-DBPs, possibly due to the photodegradation of the important HBrO/HClO intermediate and the degradation of formed Br-DBPs. The formation of Br-DBPs chlorinated by ClO2 increased under sunlight irradiation. The number of Br-DBPs formed during chlorination processes agreed well with the total organic bromine (TOBr) content measured by inductively coupled plasma mass spectrometry (ICP-MS). Most of the Br-DBPs were highly unsaturated and phenolic compounds, which were primarily generated through electrophilic substitution by bromine coupled with other reactions. In addition, some emerging aromatic Br-DBPs with high relative intensities were also assigned, and these compounds might be highly lipophilic and could potentially accumulate in marine organisms. Our findings call for further focus on and investigation of the Br-DBPs produced in chlorinated aquaculture seawater.

Evaluating the inhalation bioaccessibility of traffic-impacted particulate matter-bound PAHs in a road tunnel by simulated lung fluids.

Polycyclic aromatic hydrocarbons (PAHs) are the most highly concerned pollutants bound on traffic-impacted particulate matter (TIPM). The inhaled TIPM-bound PAHs risk has attracted much attention, whereas the inhalation bioaccessibility, a method to refine the exposure risk assessment, has not yet been extensively introduced in the exposure risk assessment. Thus, in vitro assays using artificial lung fluids including artificial lysosomal fluid (ALF), Gamble's solution (GS), and modified GS (MGS) were conducted to assess the inhalation bioaccessibility of USEPA 16 PAHs in TIPM collected from an expressway tunnel, the influence factors of PAHs' inhalation bioaccessibility were explored, and the exposure risk of TIPM-bound PAHs was estimated based on inhalation bioaccessibility. Results showed that the average PAHs concentrations were 30.5 ± 12.9 ng/m3, 36.2 ± 5.19 ng/m3, and 39.9 ± 4.31 ng/m3 in the tunnel inlet PM2.5, TSP, and tunnel center PM2.5, respectively. Phe, Flt, Pyr, Nap, Chr, BbF, and BkF were found as the dominant species in TSP and PM2.5, indicating a dominant contribution of PAHs from diesel-fueled vehicular emissions. The bioaccessible fractions measured for different PAH species in tunnel PM2.5 and TSP were highly variable, which can be attributed to PAHs' physicochemical properties, size, and carbonaceous materials of TIPM. The addition of Tenax into SLF as an "adsorption sink" can greatly increase PAHs' inhalation bioaccessibility, but DPPC has a limited effect on tunnel PM-bound PAHs' bioaccessibility. The incremental lifetime carcinogenic risk (ILCR) of tunnel inlet PM2.5-bound PAHs evaluated according to their total mass concentration exceeded the threshold (1.0 × 10-6) set by the USEPA, whereas the ILCRs estimated based on the inhalation bioaccessibility were far below the threshold. Hence, it is vitally important to take into consideration of pollutant's bioaccessibility to refine health risk assessment.

Elevated occupational exposure to chlorinated phosphate esters at a construction materials manufacturing plant.

BACKGROUND: Numerous studies have documented that the general population is widely exposed to organophosphate esters (OPEs), yet studies on the emissions of OPEs in the industrial application processes and their occupational exposure are scarce. The aim of this study was to assess the exposure to OPEs for workers engaged in OPE-retarded construction material manufacturing plant in China. METHOD: Paired dust samples (12 samples each time) from an OPEs retarded building materials manufacturing plant during the plant uptime and downtime have been analyzed for tris(2-chloroethyl)-phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCPP), and other commonly used OPEs. Moreover, nine OPEs metabolites (mOPEs) in urine samples (n = 42) from fourteen workers who engaged in this plant were also measured. The daily exposure doses to OPEs were estimated from the measured urinary concentrations of corresponding mOPEs. RESULTS: Thirteen out of fourteen studied OPEs (except for tri-n-propyl phosphate, TnPP) were determined in all dust samples from the manufacturing plant, and TCEP and TCPP were the predominant compounds in dust collected from the plant uptime and downtime. Overall, the occupationally exposed population had significantly higher (p < 0.01) urinary levels of mOPE, especially for bis (2-chloroethyl) phosphate (BCEP), relative to the reference population. Workshop workers who directly involved in the production of OPEs treated products had higher OPEs exposure. Risk assessment revealed that cancer risk (1.5 × 10-6-8.5 × 10-4) for all workers was larger than 1 × 10-6 when levels of mOPEs in urine from workers were used for estimating OPEs exposure, revealing moderate to high potential cancer risk to workers from OPEs exposure. CONCLUSION: To our knowledge, this is the first study reporting emissions of OPEs in OPE-treated products manufacturing processes and the potential exposure of the occupationally exposed population. OPEs, especially for TCEP and TCPP, present at elevated levels and pose moderate to high potential health risks to the exposed workers, emphasizing the importance of strengthening occupational exposure prevention in similar industries.

Sorption and transport of aluminum dialkyl phosphinate flame retardants and their hydrolysates in soils.

Aluminum dialkyl phosphinates (ADPs) are a class of promising phosphorus-containing flame retardants, but their environmental fate is not well understood. Sorption and transport behaviors of ADPs, and their hydrolysates dialkyl phosphinic acids (DPAs) were studied by batch and column experiments. ADPs are less mobile in soil columns with more than half (>52.6%) of ADPs retained in the soil and residues in the topmost 2-cm layer account for more than 57% of total residues. Dissolution and dispersion of fine grain ADPs were responsible for the transport of ADPs. Sorption DPAs (logKoc) was significantly related to the lipophilicity of DPAs (logD) (p < 0.05). Soil pH and clay content were the dominant factors governing the sorption and transport of DPAs in soils, indicating the importance of electrostatic interactions. The retardation factors (R) of DPAs derived from leaching experiments were pH-dependent with larger R values in the acidic soil (pH = 4.0) where anionic and neutral species of DPAs coexisted. Both physical and chemical non-equilibrium convection-dispersion equations (CDE) yield appropriate modeling for DPAs transport. In most cases, R values estimated from column tests differed from those derived from the batch experiments, which might be attributed to non-equilibrium sorption processes in dynamic conditions.

Occurrence and distribution of oligomeric organophosphorus flame retardants in different treatment stages of a sewage treatment plant.

Oligomeric organophosphate esters (OOPEs) like 2,2-bis(chloromethyl)-propane-1,3-diyltetrakis (2-chloroethyl) bisphosphate (V6), resorcinol bis(diphenylphosphate) (RDP) and bisphenol A bis(diphenylphosphate) (BDP), are widely used as alternatives of Deca-BDE in plastic and electronic consumer products. However, studies on the environmental occurrence and fate of OOPEs are very scarce. This work studied the occurrence, distribution and fate of V6, BDP and RDP during the different treatment stages of a sewage treatment plant (STP) in Beijing, China. To accomplish this, a method to analyze trace V6, BDP and RDP in suspended solids samples and aqueous samples of sewage and sludge was developed by using liquid chromatography tandem mass spectrometry (LC-MS/MS). Using this method, BDP and RDP were detected for the first time in suspended solids of sewage and sludge with a concentration of 2.06-5.82 ng/g dry weight and 0.44-3.45 ng/g dry weight, respectively, whereas their concentration level in the aqueous phase of these samples were below the detection limits of the method. However, V6 was detected in all treatment stages of the STP, with concentrations in the range of 10.2-27.1 ng/L in aqueous phase and 0.40-1.73 ng/g dw in solid phase. Mass balance results indicated that 75.6% of the original V6 mass flow was discharged along with effluent, while 83.3% and 72.2% of the initial RDP and BDP mass flow were lost due to biodegradation, respectively. Nevertheless, compared to the 14 widely used monomeric organophosphate esters (MOPEs), the concentration levels of OOPEs in this studied STP were relatively low.

Developmental neurotoxicity of triphenyl phosphate in zebrafish larvae.

Triphenyl phosphate (TPhP), a typical organophosphate ester, is frequently detected in the environment and biota samples. It has been implicated as a neurotoxin as its structure is similar to neurotoxic organophosphate pesticides. The purpose of the present study was to investigate its potential developmental neurotoxicity in fish by using zebrafish larvae as a model. Zebrafish (Danio rerio) embryos were exposed to 0.8, 4, 20 and 100 µg/L of TPhP from 2 until 144 h post-fertilization. TPhP was found to have high bioconcentrations in zebrafish larvae after exposure. Further, it significantly reduced locomotor activity as well as the heart rate at the 100 µg/L concentration. TPhP exposure significantly altered the content of the neurotransmitters γ-aminobutyric and histamine. Downregulation of the genes related to central nervous system development (e.g., α1-tubulin, mbp, syn2a, shha, and elavl3) as well as the corresponding proteins (e.g., α1-tubulin, mbp, and syn2a) was observed, but the gap-43 protein was found to upregulated. Finally, marked inhibition of total acetylcholinesterase activity, which is considered as a biomarker of neurotoxicant exposure, was also observed in the larvae. Our results indicate that exposure to environmentally relevant concentrations of TPhP can affect different parameters related to center nervous system development, and thus contribute to developmental neurotoxicity in early developing zebrafish larvae.

Simultaneous determination of the lipophilicity and dissociation constants of dialkyl phosphinic acids by negligible depletion hollow fiber membrane-protected liquid-phase microextraction.

Determination of the physicochemical properties, especially the lipophilicity (expressed as the logarithm of distribution coefficient, log D) and dissociation constant (pKa), is of great importance in the early stage of environmental risk assessment for an ionizable compound without these data. Currently, the log D and pKa values of dialkyl phosphinic acids (DPAs), the environmental hydrolysates of aluminum dialkyl phosphinates (ADPs) that is one class of emerging phosphorus-containing flame retardants, are not available. In this study, the log D and pKa values of three DPAs including methylethylphosphinic acid (MEPA), diethylphosphinic acid (DEPA) and methylcyclohexyl phosphinic acid (MHPA), were simultaneously determined by negligible depletion hollow fiber supported liquid phase microextraction (nd-HF-LPME) followed by ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). The pKa and log D of DPAs were determined by curve-fitting the experimental data with equations derived on the basis of the Henderson-Hasselbalch equation and compared with model calculated data. For MEPA, DEPA and MHPA, the pKa values were close and around 3, but the log Ds were strongly pH-dependent with values from -5.01 to 1.01. The log KOW of the neutral form (logKOW,HA) and ionic form (logKOW,A) were in the range of -0.67-1.02 and -3.86--1.33, respectively. The experimentally determined pKa values were highly in good agreement with ACD/pKa predicted values and the measured log KOW,HA values were closely related to KOWWIN calculated ones, suggesting ACD/pKa and KOWWIN are good alternative methods to estimate pKa and log KOW of DPAs, respectively. As far as we know, this is the first report on the pKa and log D data for DPAs, which are fundamental for the product design and evaluating the environmental behavior and effects of DPAs and ADPs.

Tris(pentafluoroethyl)trifluorophosphate-basd ionic liquids as advantageous solid-phase micro-extraction coatings for the extraction of organophosphate esters in environmental waters.

Ionic liquids (ILs) containing the tris(pentafluoroethyl)trifluorophosphate [FAP] anion and various cations have great potential in sample preparation because of their excellent hydrophobicity, thermostability and low hydrolysity. In the present study, a [FAP]-based IL, 1-hexyl-3-methylimidazolium tris (pentafluoroethyl) trifluoro phosphate ([HMIM][FAP]), was used as coatings of solid-phase microextraction (SPME) for extracting organophosphate esters (OPEs) from environmental water samples. This SPME fiber was fabricated by coating a stainless steel wire substrate with [HMIM][FAP] via a simple direct dip-coating approach, and the extraction was conducted by the direct immersion solid phase microextraction. Coupling to gas chromatography mass spectrometry (GC-MS), the developed SPME method exhibited excellent selectivity and sensitivity towards the extraction of 11 OPEs from aqueous samples. Satisfactory linearity (R(2)≥0.99) of the calibration curves was obtained over the range of 0.05-50.0ngmL(-1) with the limits of detection (LODs, S/N=3) and limits of quantification (LOQs, S/N=10) ranged from 0.13-7.40ngL(-1) and 0.50-24.0ngL(-1), respectively. The proposed SPME method showed excellent extraction efficiency to OPEs with enrichment factors in the range of 168-2603, and acceptable reproducibility with relative standard deviations (RSDs) ≤15% for single fiber (n=7) and ≤16% for fiber-to-fiber (n=3×3) at a concentration level of 0.5ngmL(-1), respectively. The prepared IL-based fiber was successfully applied to determine eleven common used OPEs in tap water, influent and effluent of sewage treatment plant, with results are comparable to those determined by the reference (UPLC-MS/MS), and spiked recoveries in the range of 84.0-108%, 82.1-123% and 82.8-100%, respectively.