Contamination and Carcinogenic Risks of Lead in Lip Cosmetics in China.

There are growing concerns about elevated lead (Pb) levels in lip cosmetics, yet in China, the largest lip cosmetic market, recent Pb contamination in lip cosmetics and associated Pb exposure remain unclear. Here, we measured Pb levels of 29 popular lip cosmetics in China and conducted the bioaccessibility-corrected carcinogenic risk assessments and sensitivity analysis regarding Pb exposure for consumers using Monte Carlo simulation. The Pb concentrations of collected samples ranged from undetectable (< 0.05 µg/kg) to 0.21 mg/kg, all of which were well below the Pb concentration limit set for cosmetics in China (10 mg/kg). The 50th percentile incremental lifetime cancer risk (ILCR) of Pb in Chinese cosmetics (1.20E-07) was below the acceptable level (1E-06), indicating that the application of lip cosmetics and subsequent Pb exposure does not pose carcinogenic risks to consumers in most cases. The results of this study provide new insights into understanding the Pb risk in lip cosmetics.

Insights into the photocatalytic degradation of hydrophobic organic contaminants on the surface of nitrogen doped silica: New findings of the formation of silicon-based substitution products.

In this work, nitrogen-doped SiO2 (N-SiO2) was successfully synthesized to develop an "adsorption-photocatalytic degradation" water purification technology to remove hydrophobic organic contaminants (HOCs). As a representative of HOCs, decabromodiphenylethane (DBDPE) could be efficiently degraded under simulated sunlight after adsorption on the surface of N-SiO2. Due to the generation of reactive oxygen species (ROS) and silicon-based radicals, the photodegradation rate of DBDPE on water-SiO2 interface was 1.5-fold higher than that in water. Furthermore, the transformation pathways of DBDPE on N-SiO2 surface were compared with that in water. Bond breaking and debromination reactions were the common pathways, while hydroxylation and silicon-based substitution reactions were the specific transformation pathways for DBDPE on the surface of N-SiO2. Density functional theory (DFT) calculation was used to reveal the generation mechanism of silicon-based radicals and determine the rationality of the involvement of silicon-based radicals in DBDPE transformation. The energy barriers of silicon-based substitution reaction were comparable to that of hydroxylation and debromination reactions, which confirmed the plausibility of the generation of silicon-based substitution products. This study provides an efficient method for the disposal of HOCs, which also gives some new insights into the conversion mechanism of organic pollutants mediated by silicon-based radicals.

Enhanced removal of ammonia in Fe(VI)/Br- oxidation system: Kinetics, transformation mechanism and theoretical calculations.

This work systematically examined the capability of ferrate (Fe(VI)) for ammonia oxidation, revealing for the first time that bromide ions (Br-) played an important role in promoting the removal of ammonia in Fe(VI) system. In the presence of 10.0 mM Br-, the removal efficiency of ammonia was nearly 3.4 times that of the control, and 1.0 mM ammonia was almost completely removed after two rounds addition of 1.0 mM Fe(VI) in 60 min. PMSO probe test, electron paramagnetic resonance spectra and radical quenching experiments were employed to interpret the underlying promotion mechanism of Br-, and it was proposed that the formation of active bromine (HOBr/OBr-) played a dominant role in the enhanced oxidative removal of ammonia by Fe(VI). Further kinetic model simulations revealed that HOBr/OBr- and Fe(VI) were the two major reactive species in Fe(VI)/Br- system, accounting for 66.7% and 33.0% of ammonia removal, respectively. As the target contaminant, ammonia could quickly consume the generated HOBr/OBr-, thereby suppressing the formation of brominated disinfection byproducts. Finally, NO3- was identified as the dominant transformation product of ammonia, and density functional theory (DFT) calculations revealed that six reaction stages were involved in ammonia oxidation with the first step as the rate-limiting step. This work would enable the full use of coexisting bromides for effective removal of ammonia from natural waters or wastewaters by in situ Fe(VI) oxidation method.

Reproducibility and persistence of individual marks on 3000 fired bullets from five Chinese Norinco QSZ-92 9 × 19 mm pistols, and the search performance of Evofinder® to a 1000 firearm database of the same model firearm.

For firearm identification, foundational validity based on the reproducibility and persistence of characteristic marks must be established. We investigate the fired bullets of five Chinese Norinco QSZ-92 9 × 19 mm pistols over 3000 shots. The first 50 fired bullets are recovered, whereas every 50th fired bullet is recovered from the 51st to 3000th round. As such, 109 bullets are available for each pistol, and totally 545 bullets are introduced into the Evofinder® system. A large background database comprising 3000 bullets fired from 1000 registered QSZ92 9 × 19 mm pistols is used as interference. Both on-screen analysis and automatic comparison are performed. The first fired bullets from the five pistols are separately correlated with the database. The results show that although the similarity for known match bullets changes slightly as the shot number increases, the land-engraved area (LEA), groove-engraved area (GEA), and slippage marks can be reproducibly transferred to the fired bullets in consecutive shots. The Evofinder system ranks all known match bullets on the top of the correlation result with the combination of LEA, GEA, and slippage marks.

Insight into the interaction between Fe-based nanomaterials and maize (Zea mays) plants at metabolic level.

Properly understanding the fundamental interactions between engineered nanoparticles (NPs) and plants is crucial for nano-enabled agriculture. In this study, Fe and Fe3O4 (magnetite), which are naturally occurred nanosized crystals and minerals, were foliar applied to 4-week-old maize plants for 10 days to evaluate their impact on plant photosynthesis and growth. Hill reaction of isolated maize leaf chloroplasts was carried out to determine the performance of two Fe-based NPs on photosynthetic activities at cell level. Meanwhile, gas chromatography-mass spectrometry (GC-MS) based metabolomics was used to explore the deep insight into the interaction between Fe-based NPs and maize plants. Results showed that maize leaf net photosynthesis rate and chlorophyll content were significantly increased by Fe NPs for 19.9% and 19.3%; and Fe3O4 NPs for 27.5% and 26.1%, respectively. Accordingly, plant biomass has been significantly increased by Fe and Fe3O4 NPs by 31.8% and 34.6%, respectively. Metabolomics revealed that both Fe-based NPs induced metabolic reprogramming in maize leaves. The biosynthesis of some compatible solutes and antioxidant compounds were inhibited. In addition, exposure to Fe-based NPs tentatively shut down some energy consuming pathways, such as photorespiration, alanine metabolism, branch chain amino acid biosynthesis. The trade-off of energy consuming pathways might be alternative explanation for the enhanced photosynthesis. The results of this study exhibited the promising potential for Fe-based NPs to be used in nano-enabled agriculture to promote plant growth.

Molecular identification guided process design for advanced treatment of electroless nickel plating effluent.

It has been long desired but challenging to forward the advanced treatment of wastewater from empirical trials towards scientific design due to the lack of molecular insight into the pollutants of concern. Herein, we first established a systematic methodology to identify the ligands of Ni(II)-complexes in an electroless nickel (EN) plating effluent. The presence of N-containing groups in the ligands of most Ni(II)-complexes was verified by time-aligned ICP-MS and ESI-HRMS, implying the suitability of autocatalytic ozonation for efficient decomplexation. Thereby, a combined process was proposed on the basis of ozonation to achieve over 83% decomplexation of Ni(II) (initially at 0.36 mg/L), followed by selective Ni(II) sequestration for resource recovery. Combinational LC-MS systems revealed the ozonation-induced fragmentation or elimination of most Ni(II)-complexes as well as the structural change of the residual complexed molecules. The released free Ni(II) was further sequestrated by a nanocomposite of hydrated Zr(IV) oxide confined in a polymeric cation exchanger (nHZO@PCE). The fixed-bed working capacity of nHZO@PCE (∼550 BV) for the ozonated EN plating effluent was over 18 times that of the cation exchanger host (∼30 BV) at the breakthrough point of 0.10 mg Ni/L. More attractively, five adsorption-regeneration cycles demonstrated the great potential of the hybrid adsorbent for sustainable utilization. This study is believed to shed new light on how to design rational processes for advanced treatment of real wastewater based on molecular identification.

Combined Toxicity of Silver Nanoparticles with Hematite or Plastic Nanoparticles toward Two Freshwater Algae.

In the natural environment, the interactions of different types of nanoparticles (NPs) may alter their toxicity, thus masking their true environmental effects. This study investigated the toxicity of silver NPs (AgNPs) combined with hematite (HemNPs) or polystyrene (PsNPs) NPs toward the freshwater algae Chlamydomonas reinhardtii and Ochromonas danica. The former has a cell wall and cannot internalize these NPs, while the latter without a cell wall can. Therefore, the toxicity of AgNPs toward C. reinhardtii was attributed to the released Ag ions, while AgNPs had direct toxic effects on O. danica. Moreover, nontoxic HemNPs ameliorated AgNP toxicity toward C. reinhardtii, by decreasing the bioavailability of Ag ions through adsorption. Despite their role as Ag-ion carriers, HemNPs still reduced the toxicity of AgNPs toward O. danica by competitively inhibiting AgNP uptake. In both algae, Ag accumulation fully accounted for the combined toxicity of AgNPs and HemNPs. However, the combined toxicity of AgNPs and PsNPs was complicated by their significant individual toxicities and the synergistic interactions of these particles with the algae, regardless of differences in Ag accumulation. Overall, in environmental assessments, considerations of the combined toxicity of dissimilar NPs will allow more accurate assessments of their environmental risks.

Nickel speciation of spent electroless nickel plating effluent along the typical sequential treatment scheme.

The electroless nickel (EN) industry has suffered from the reduction in Ni concentration to lower than 0.1 mg/L. Hence, Ni speciation along a typical sequential treatment scheme has important implications to optimize the design of advanced treatment. For the first time, we revealed the Ni speciation in segmented EN outfall effluents by virtue of multiple analytical methods. After ensuring all the Ni-bearing complexes were completely dissolved by size-fractioned ultrafiltration trials, customized mass spectra analysis was conducted. In a series of ICP-MS assays, the potential polyatomic interfering species was primarily excluded. The chromatography hyphenated IC-ICP-MS and SEC-ICP-MS results demonstrated that the dominant Ni species in the EN effluents was similar to EDTA-Ni but with a smaller size. The LC-MS experiment further distinguished several typical Ni-bearing complexes. Although Ni concentration declined continuously along the treatment scheme, the number of detected Ni-bearing complexes gradually increased but with lower molecular weights. Most of the detected mononuclear complexes had higher indexes of hydrogen deficiency (IHD) than EDTA-Ni, whereas it was believed that the similar stereo ring shape was widespread in the EN effluent. Considering the efficient Ni decrease after the Fenton unit, further post-treatment approaches featuring higher active radical yields were suggested.

Fe(VI)-Mediated Single-Electron Coupling Processes for the Removal of Chlorophene: A Combined Experimental and Computational Study.

Potassium ferrate [Fe(VI)] is a promising oxidant widely used in water treatment for the elimination of organic pollutants. In this work, the reaction kinetics, products, and mechanisms of the antimicrobial agent chlorophene (CP) undergoing Fe(VI) oxidation in aqueous solutions were investigated. CP is very readily degraded by Fe(VI), with the apparent second-order rate constant, k, being 423.2 M-1 s-1 at pH 8.0. A total of 22 oxidation products were identified using liquid chromatography-quadrupole time-of-flight-mass spectrometry , and their structures were further elucidated using tandem mass spectrometry. According to the extracted peak areas in mass spectra, the main reaction products were the coupling products (dimers, trimers, and tetramers) that formed via single-electron coupling. Theoretical calculations demonstrated that hydrogen abstraction should easily occur at the hydroxyl group to produce reactive CP· radicals for subsequent polymerization. Cleavage of the C-C bridge bond, electrophilic substitution, hydroxylation, ring opening, and decarboxylation were also observed during the Fe(VI) oxidation process. In addition, the degradation of CP by Fe(VI) was also effective in real waters, which provides a basis for potential applications.

Photodegradation of 17ß-estradiol on silica gel and natural soil by UV treatment.

This paper evaluates the UV photodegradation of 17ß-estradiol (E2) on silica gel and in natural soil with different soil components. Silica gel was chosen as a stable and pure support to simulate the photochemical behavior of E2 on the surface of natural soil. Ultraviolet light, rather than visible light, was confirmed to play a decisive role in the photodegradation of E2 on silica gel. The effect of three soil components, including humic acid (HA), inorganic salts, and relative humidity (RH), on the photochemical behavior of E2 on silica gel or soil under UV irradiation was then evaluated. Two HA concentrations (10 and 20 mg g-1) and three salts (ferric sulfate, copper sulfate and sodium carbonate) were observed to obviously inhibit the degradation of E2 on silica gel. Interestingly, nitrate was found to obviously improve the removal efficiency of E2. Both too-dry and too-wet conditions obviously reduced the removal rate of E2, and the optimum relative humidity (RH) value was found to be approximately about 35% (30 °C). Furthermore, twenty intermediate products and two major pathways were proposed to describe the transformation processes of E2 treated by UV irradiation, among which oligomers were found to be the major intermediate products before complete mineralization. The efficient UV removal of E2 on silica gel and natural soil suggested a feasible strategy to remediate E2 contaminated soil.

Waterborne and Dietborne Toxicity of Inorganic Arsenic to the Freshwater Zooplankton Daphnia magna.

Waterborne and dietborne exposure are both important sources for the accumulation of inorganic arsenic (iAs) in aquatic organisms. Although the waterborne toxicity of iAs has been extensively investigated, its dietborne toxicity has received little attention. The present study examined the acute and chronic toxicity of arsenate (iAsV) and arsenite (iAsIII) to the freshwater zooplankton species Daphnia magna under both waterborne and dietborne exposure scenarios. The bioaccumulation, speciation, and tissue and subcellular distributions of arsenic were analyzed to understand the mechanisms accounting for differences in toxicity related to different arsenic species, exposure scenarios, and exposure duration. The toxicity of iAs increased with exposure time, and iAsIII was more toxic than iAsV. Moreover, although dietborne iAs had no acute effect on D. magna, it incurred significant toxicity in the chronic-exposure experiment. Nevertheless, the toxicity of dietborne iAs was still lower than that of waterborne iAs regardless of the exposure duration. This difference was found to be caused by the lower bioaccumulation of dietborne iAs, its higher distribution in the gut and in the biologically detoxified subcellular fraction, and greater transformation to the less toxic dimethylarsinic acid. Overall, the dietborne toxicity of iAs should be considered when evaluating the environmental risks posed by arsenic.

Potent removal of cyanobacteria with controlled release of toxic secondary metabolites by a titanium xerogel coagulant.

Cyanobacteria blooming is a serious environmental issue throughout the world. Removal of cyanobacterial cells from surface water with controlled release of cyanobacterial organic matter (COM), especially toxic microcystins (MCs), would potentially reduce the processing burden in follow-up water treatment. Coagulation is a key technique in water treatment. Herein, the potential application of a novel titanium xerogel coagulant (TXC) was evaluated for the treatment of cyanobacteria-laden water in terms of cyanobacteria removal efficiency, variation of cell viability, the release and evolution of COM in the floc accumulation and storage process. Under acidic to neutral conditions, TXC showed a higher removal efficiency of approximately 99% for cyanobacteria and a lower residual Ti concentration than the widely-used commercial polyferric sulfate (PFS) and polyaluminum chloride (PAC). Another advantage of TXC was the reduced MCs concentration caused by the released acetylacetone (AcAc) from the hydrolysis of TXC. Under solar irradiation, AcAc degraded the extracellular MCs from an initial concentration of 40 µg/L to a residual concentration of 7 µg/L during a 16-day floc storage process. The low residual Ti concentration (< 0.04 mg/L) and the efficient removal of COM/MCs following TXC coagulation reduced the toxicity to photobacteria. The results demonstrate that TXC is a promising dual-effect coagulant for treatment of cyanobacteria-laden water.

Inhibitory effects of rice residues amendment on Cd phytoavailability: A matter of Cd-organic matter interactions?

Incorporating crop residues into soils, a most common way of organic input into farmland soils, is being encouraged in many parts of the world, while its potential impacts on Cd phytoavailability are not well understood. Here, a Cd-contaminated soil was amended with rice residues (RR, i.e., straw + root mixture) or not (Control) and incubated for 81 days under laboratory-controlled conditions. During the incubation, key soil parameters (e.g., dissolved organic carbon and pH), Cd geochemical fractionation (by BCR sequential extraction), and CaCl2 extracted Cd in soils (by 0.01 M CaCl2 extraction) were quantified to explain the effects of RR amendment on Cd phytoavailability (assessed by 7 day-cultivation of rice seedling in soils). Besides, hydroponic experiments were designed to explore the effects of D-RR-OM (dissolved-RR-organic matter) on the uptake of Cd by rice seedlings (quantified by uptake constant rate, ku, using stable isotope tracing technique). Our results demonstrated that RR amendment reduced Cd phytoavailability by 17-92% compared with Control during incubation, which might be explained by the interactions between Cd and RR-OM (RR-organic matter) in soil or porewater: (1) Cd immobilization due to its association with solid-RR-OM in soils, (2) Cd mobilization by D-RR-OM, and (3) Cd complexation with D-RR-OM in porewater, and thus reduced ku of Cd. Our results suggested that dynamics of RR-OM (e.g., dissolution, decomposition and transformation) in soils, and thus interactions between Cd and solid/dissolved-RR-OM may control Cd phytoavailability under RR amendment. Information gained in this study would further our understanding about Cd phytoavailability in farming soils.

Aggregation Reverses the Carrier Effects of TiO2 Nanoparticles on Cadmium Accumulation in the Waterflea Daphnia magna.

Our previous study reported that the Ca-dependent aggregation of polyacrylate-coated TiO2 nanoparticles (PAA-TiO2-NPs) determines their routes of uptake by the waterflea Daphnia magna. Besides the effects of aggregation on NP bioaccumulation, how this process may influence the bioavailability of NP-adsorbed pollutants remains obscure. In the present study, the aggregation of PAA-TiO2-NPs was also adjusted through Ca. Then the accumulation and toxicity of Cd in D. magna were investigated in the presence and absence of the NPs. Although PAA-TiO2-NPs ameliorated Cd toxicity at both low and high Ca concentrations, the underlying mechanisms differed completely. At low Ca, the metal-NP complexes were accumulated by endocytosis and passive drinking, with both pollutants distributed throughout the daphnid. Nevertheless, Cd accumulation was reduced due to its rapid dissociation from the NPs during the endocytosis of the metal-NP complexes. At high Ca, the metal-NP complexes were actively ingested, Cd accumulation was induced, and both pollutants were concentrated in the daphnid gut. The aggregation-dependent effects of PAA-TiO2-NPs on Cd bioaccumulation were further evidenced by the distinct patterns of metal efflux from D. magna at different Ca concentrations. Overall, Cd adsorption by PAA-TiO2-NPs may either increase or reduce its bioaccumulation, as determined by the aggregation of the NPs.

TiO2 Nanoparticle Uptake by the Water Flea Daphnia magna via Different Routes is Calcium-Dependent.

Calcium plays versatile roles in aquatic ecosystems. In this study, we investigated its effects on the uptake of polyacrylate-coated TiO2 nanoparticles (PAA-TiO2-NPs) by the water flea (cladoceran) Daphnia magna. Particle distribution in these daphnids was also visualized using synchrotron radiation-based micro X-ray fluorescence spectroscopy, transmission electron microscopy, and scanning electron microscopy. At low ambient Ca concentrations in the experimental medium ([Ca]dis), PAA-TiO2-NPs were well dispersed and distributed throughout the daphnid; the particle concentration was highest in the abdominal zone and the gut, as a result of endocytosis and passive drinking of the nanoparticles, respectively. Further, Ca induced PAA-TiO2-NP uptake as a result of the increased Ca influx. At a high [Ca]dis, the PAA-TiO2-NPs formed micrometer-sized aggregates that were ingested by D. magna and concentrated only in its gut, independent of the Ca influx. Our results demonstrated the multiple effects of Ca on nanoparticle bioaccumulation. Specifically, well-dispersed nanoparticles were taken up by D. magna through endocytosis and passive drinking whereas the uptake of micrometer-sized aggregates relied on active ingestion.

Effect of different carbon nanotubes on cadmium toxicity to Daphnia magna: The role of catalyst impurities and adsorption capacity.

Experiments were conducted to investigate the effect of four different carbon nanotubes single- and multi-walled carbon nanotubes (SWCNTs and MWCNTs) and hydroxylated and carboxylated multi-walled carbon nanotubes (OH-MWCNTs and COOH-MWCNTs) on Cd toxicity to the aquatic organism Daphnia magna. The acute toxicity results indicated that all CNTs could enhance the toxicity of Cd to D. magna. Furthermore, the filtrate toxicity and adsorption tests showed that the toxicity-increasing effect of SWCNTs and MWCNTs in the overall system was mainly caused by catalysts impurities from the pristine CNTs, whereas the greater adsorption of Cd onto OH-MWCNTs (30.52 mg/g) and COOH-MWCNTs (24.93 mg/g) was the key factor contributing to the enhanced toxicity. This result raised a concern that the metal catalyst impurities, adsorption capacities, and accumulation of waterborne CNTs were responsible for the toxicity of Cd to aquatic organism.

Impact of carbon nanotubes on the toxicity of inorganic arsenic [AS(III) and AS(V)] to Daphnia magna: The role of certain arsenic species.

As a type of emerging nanomaterial, hydroxylated multiwalled carbon nanotubes (OH-MWCNTs) may interact with other pollutants in the aquatic environments and further influence their toxicity, transport, and fate. Thus, evaluation of toxicity to arsenic in the presence of CNTs needs to receive much more attention. The present study was conducted to explore the underlying mechanisms of OH-MWCNT-induced arsenic (As[III] and As[V]) toxicity changes in the aquatic organism Daphnia magna at different pH levels. The most toxic species for As(III) and As(V) to D. magna were found to be H2 AsO3 (-) and H2 AsO4 (-) . It appeared that the pH values were of greatest importance when the biological toxicity of As(III) and As(V) was compared. Furthermore, the effects of OH-MWCNTs on arsenic toxicity to D. magna indicated that the presence of OH-MWCNTs could enhance the toxicity of arsenic. The interactions of arsenic with OH-MWCNTs were further investigated by conducting adsorption experiments. The adsorption capacity of As(V) by OH-MWCNTs was found to be higher than that of As(III). To conclude, adsorption of certain arsenic species onto OH-MWCNTs is crucial for a reliable interpretation of enhanced toxicity. Environ Toxicol Chem 2016;35:1852-1859. © 2016 SETAC.

Effects of sulfate and selenite on mercury methylation in a mercury-contaminated rice paddy soil under anoxic conditions.

Biogeochemical cycling of sulfur and selenium (Se) could play an important role in methylmercury (MeHg) dynamics in soil, while their potential effects on MeHg production in rice paddy soil are less understood. The main objective of this study was to explore the effects of sulfate and selenite on net MeHg production in contaminated rice paddy soil, characterized with massive MeHg production and thus MeHg accumulation in rice. A series of microcosm incubation experiments were conducted using a contaminated paddy soil amended with sulfate and/or selenite, in which sulfate-reducing bacteria were mainly responsible for MeHg production. Our results demonstrated that sulfate addition reduced solid and dissolved MeHg levels in soils by ≤18 and ≤25 %, respectively. Compared to sulfate, selenite was more effective in inhibiting net MeHg production, and the inhibitory effect depended largely on amended selenite doses. Moreover, sulfate input played a dual role in affecting Hg-Se interactions in soil, which could be explained by the dynamics of sulfate under anoxic conditions. Therefore, the effects of sulfate and selenium input should be carefully considered when assessing risk of Hg in anoxic environments (e.g., rice paddy field and wetland).

Characterization of the thermolysis products of Nafion membrane: A potential source of perfluorinated compounds in the environment.

The thermal decomposition of Nafion N117 membrane, a typical perfluorosulfonic acid membrane that is widely used in various chemical technologies, was investigated in this study. Structural identification of thermolysis products in water and methanol was performed using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS). The fluoride release was studied using an ion-chromatography system, and the membrane thermal stability was characterized by thermogravimetric analysis. Notably, several types of perfluorinated compounds (PFCs) including perfluorocarboxylic acids were detected and identified. Based on these data, a thermolysis mechanism was proposed involving cleavage of both the polymer backbone and its side chains by attack of radical species. This is the first systematic report on the thermolysis products of Nafion by simulating its high-temperature operation and disposal process via incineration. The results of this study indicate that Nafion is a potential environmental source of PFCs, which have attracted growing interest and concern in recent years. Additionally, this study provides an analytical justification of the LC/ESI-MS/MS method for characterizing the degradation products of polymer electrolyte membranes. These identifications can substantially facilitate an understanding of their decomposition mechanisms and offer insight into the proper utilization and effective management on these membranes.

Experimental investigation on the soil sorption properties and hydrophobicity of polymethoxylated, polyhydroxylated diphenyl ethers and methoxylated-, hydroxylated-polychlorinated diphenyl ethers.

In the present study, twenty-six types of polymethoxylated diphenyl ethers (PMeODEs), twenty 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 synthesized. The logKow and logKoc values of all of the synthesized compounds were then determined using HPLC. The soil sorption properties of five types of selected substituted diphenyl ethers (DEs) were investigated. Sorption behavior studies suggested that rapid sorption played a primary role in the sorption process of the selected DEs and their sorption isotherms were fitted the Freundlich logarithmic model. For PMeODEs and PHODEs, with the increase in the number of substituents, both logKow and logKoc values exhibited linearly decreasing trends. Unlike PMeODEs and PHODEs, both logKow and logKoc values of MeO/HO-PCDEs were decreased linearly with the increasing number of chlorine atoms. The reason maybe that both methoxy and hydroxyl are hydrophilic groups, whereas the chlorine atom is hydrophobic group. Linear relationships were observed for the logKow and logKoc of all studied DEs. Moreover, the logKow of PMeODEs, PHODEs, MeO- and HO-PCDEs and their corresponding PCDEs showed good linearity.