[Effect of Sulfate on the Migration and Transformation of Methylmercury in Advanced Anaerobic Digestion of Sludge].

To study the migration and transformation of methylmercury during advanced anaerobic digestion of sludge and the role of sulfate, this study investigated the migration and transformation of methylmercury during different stages of sludge anaerobic digestion (AD) with thermal hydrolysis pretreatment and under different dosages of sulfate addition. The results showed that mercury methylation occurred in the initial stage of AD (Day 1-3), the ratio of methylmercury to total mercury increased from 0.024% (range of 0.019%-0.033%) to 0.038% (range of 0.030%-0.048%), and the net increment of methylmercury increased by 3.97, 6.09, 0.17, 3.71, and 1.66 times, respectively. In the following Day 3-5, the demethylation process occurred with the net yield of methylmercury decreased by 71.25% (ranging from 67.42% to 75.10%). Sulfate inhibited the methylation of mercury in the initial stage of AD, but had little effect on it in the late stage. This was related to the reduction of the bioavailability of neutral mercury complexes by charged groups of HgHS22- and HgS22-, as well as the immobilization of iron sulfide and mercury sulfide on S2- and bioavailable mercury. Redundancy analysis (RDA) showed that mercury methylation was affected by several factors:organic substances such as propionic acid, isobutyric acid, isovaleric acid, and Fe may promote mercury methylation, whereas protein and higher pH may be inhibitors of mercury methylation in AD of sludge.

Terrestrial mercury transformation in the Tibetan Plateau: New evidence from stable isotopes in upland buzzards.

Understanding the geochemical cycle of mercury (Hg) in the high-altitude Tibetan Plateau is of great value for studying the long-range transport of Hg. Herein, speciation and isotopic compositions of Hg in the muscle and feathers of upland buzzards (Buteo hemilasius) were studied to trace the terrestrial transformation of Hg in the Tibetan Plateau. Very low Hg content and relatively low δ202Hg values (feather: -0.77 ± 0.50‰, n = 9, muscle: -1.29 ± 0.29‰, n = 13, 1SD) were observed in upland buzzards. In contrast, the Δ199Hg values could be as high as 2.89‰ in collected samples. To our knowledge, this is the highest Δ199Hg value reported in avian tissues. Moreover, upland buzzards showed significantly different Δ199Hg values from fish collected from the same region, suggesting different generation and transformation processes of methylmercury (MeHg) in terrestrial and aquatic ecosystems. We speculated that different percentages of Hg undergoing photochemical reactions and contributions of atmospheric MeHg were possible reasons for observed differences. The results provide new clues for different circulation histories of Hg in terrestrial and aquatic ecosystems, which will be critical for further study of geochemical cycle and ecological risk of Hg in the environment.

Mercury isotope variations within the marine food web of Chinese Bohai Sea: Implications for mercury sources and biogeochemical cycling.

Mercury (Hg) speciation and isotopic compositions in a large-scale food web and seawater from Chinese Bohai Sea were analyzed to investigate methylmercury (MeHg) sources and Hg cycling. The biota showed ∼5‰ variation in mass dependent fractionation (MDF, -4.57 to 0.53‰ in δ202Hg) and mostly positive odd-isotope mass independent fractionation (odd-MIF, -0.01 to 1.21‰ in Δ199Hg). Both MDF and odd-MIF in coastal biota showed significant correlations with their trophic levels and MeHg fractions, likely reflecting a preferential trophic transfer of MeHg with higher δ202Hg and Δ199Hg than inorganic Hg. The MDF and odd-MIF of biota were largely affected by their feeding habits and living territories, and MeHg in pelagic food web was more photodegraded than in coastal food web (21-31% vs. 9-11%). From the Hg isotope signatures of pelagic biota and extrapolated coastal MeHg, we suggest that MeHg in the food webs was likely derived from sediments. Interestingly, we observed complementary even-MIF (mainly negative Δ200Hg of -0.36 to 0.08‰ and positive Δ204Hg of -0.05 to 0.82‰) in the biota and a significant linear slope of -0.5 for Δ200Hg/Δ204Hg. This leads us to speculate that atmospheric Hg0 is an important source to bioaccumulated MeHg, although the exact source-receptor relationships need further investigation.

PM2.5 induces vascular permeability increase through activating MAPK/ERK signaling pathway and ROS generation.

Although in-vivo exposure of PM2.5 has been suggested to initiate a disorder on vascular permeability, the effects and related mechanism has not been well defined. In this work, an obvious increase on vascular permeability has been confirmed in vivo by vein injection of PM2.5 into Balb/c mouse. Human umbilical vein vascular endothelial cells and the consisted ex-vivo vascular endothelium were used as model to investigate the effects of PM2.5 on the vascular permeability and the underlying molecular mechanism. Upon PM2.5 exposure, the vascular endothelial growth factor receptor 2 on cell membrane phosphorylates and activates the downstream mitogen-activated protein kinase (MAPK)/ERK signaling. The adherens junction protein VE-cadherin sheds and the intercellular junction opens, damaging the integrity of vascular endothelium via paracellular pathway. Besides, PM2.5 induces the intracellular reactive oxygen species (ROS) production and triggers the oxidative stress including activity decrease of superoxide dismutase, lactate dehydrogenase release and permeability increase of cell membrane. Taken together, the paracellular and transcellular permeability enhancement jointly contributes to the significant increase of endothelium permeability and thus vascular permeability upon PM2.5 exposure. This work provides an insight into molecular mechanism of PM2.5 associated cardiovascular disease and offered a real-time screening method for the health risk of PM2.5.

Significant contribution of metastable particulate organic matter to natural formation of silver nanoparticles in soils.

Particulate organic matter (POM) is distributed worldwide in high abundance. Although insoluble, it could serve as a redox mediator for microbial reductive dehalogenation and mineral transformation. Quantitative information on the role of POM in the natural occurrence of silver nanoparticles (AgNPs) is lacking, but is needed to re-evaluate the sources of AgNPs in soils, which are commonly considered to derive from anthropogenic inputs. Here we demonstrate that POM reduces silver ions to AgNPs under solar irradiation, by producing superoxide radicals from phenol-like groups. The contribution of POM to the naturally occurring AgNPs is estimated to be 11-31%. By providing fresh insight into the sources of AgNPs in soils, our study facilitates unbiased assessments of the fate and impacts of anthropogenic AgNPs. Moreover, the reducing role of POM is likely widespread within surface environments and is expected to significantly influence the biogeochemical cycling of Ag and other contaminants that are reactive towards phenol-like groups.

[Photolysis Mechanism of p-Nitrophenol by Nitrocellulose Membrane in Aqueous Solution].

To investigate the potential application of nitrocellulose membrane (NCM) in water treatment, this study examined the photolysis of p-nitrophenol, with NCM as the source of reactive oxygen species. Effects of solution pH, light conditions, and water dissolved substances on p-nitrophenol photolysis were investigated, and possible mechanisms were discussed. The results demonstrated that the quantum yield for hydroxyl radicals from the NCM was 1.30×10-4, which is approximately 1.86 times higher than that from TiO2. The photolysis rate of p-nitrophenol in the presence of NCM was 0.0055 min-1, which is much higher than that in pure water (9.52×10-4 min-1). This promotion was mainly caused by photo-induced generation of ·OH on NCM surface under light, in which UVA plays an important role in photolysis. The photolysis rate of p-nitrophenol increased with the increase of light intensity and membrane area. Acidic solution (pH=2.0) was preferred for the degradation of p-nitrophenol, with a photolysis rate of 0.0165 min-1; the corresponding degradation of p-nitrophenol exceeded 90% in 120 min. The effects of dissolved substances on photolysis were significantly different. NO3- promoted photolysis by generation of ·OH, and dissolved organic matter decreased photolysis through light attenuation. The intermediate products of gas chromatography-mass spectrometry analysis mainly included phenol, hydroquinone, malonic acid, and oxalic acid, and the possible photolysis pathway was given accordingly.

An Integrated Model for Input and Migration of Mercury in Chinese Coastal Sediments.

Coastal sediments are a major sink of the global mercury (Hg) biogeochemical cycle, bridging terrestrial Hg migration to the open ocean. It is thus of substantial interest to quantify the Hg contributors to coastal sediments and the extents to which the Hg sequestered into coastal sediments affects the ocean. Here, we measured concentrations and isotope compositions of Hg in Chinese coastal sediments and found that estuary sediments had distinctly higher δ202Hg and lower Δ199Hg values than marine sediments. Hg isotope compositions of marine sediments followed a latitudinal trend where δ202Hg decreases and Δ199Hg increases from north to south. An integrated model was developed based on a Hg isotope mixing model and urban distance factor (UDF), which revealed a significant difference in Hg source contributions among the estuary and marine sediments and a gradual change of dominant Hg sources from terrestrial inputs (riverine and industrial wastewater discharges) to atmospheric deposition with a decrease in urban impact. A UDF value of 306 ± 217 was established as the critical point where dominant Hg sources started to change from terrestrial inputs to atmospheric deposition. Our study helps explain the input and migration of Hg in Chinese marginal seas and provides critical insights for targeted environmental management.

Mutual detoxification of mercury and selenium in unicellular Tetrahymena.

Selenium (Se) is commonly recognized as a protective element with an antagonistic effect against mercury (Hg) toxicity. However, the mechanisms of this Hg-Se antagonism are complex and remain controversial. To gain insight into the Hg-Se antagonism, a type of unicellular eukaryotic protozoa (Tetrahymena malaccensis, T. malaccensis) was selected and individually or jointly exposed to two Hg and three Se species. We found that Se species showed different toxic effects on the proliferation of T. malaccensis with the toxicity following the order: selenite (Se(IV))>selenomethionine (SeMeth)>selenate (Se(VI)). The Hg-Se antagonism in Tetrahymena was observed because the joint toxicity significantly decreased under co-exposure to highly toxic dosages of Hg and Se versus individual toxicity. Unlike Se(IV) and Se(VI), non-toxic dosage of SeMeth significantly decreased the Hg toxicity, revealing the influence of the Se species and dosages on the Hg-Se antagonism. Unexpectedly, inorganic divalent Hg (Hg2+) and monomethylmercury (MeHg) also displayed detoxification towards extremely highly toxic dosages of Se, although their detoxifying efficiency was discrepant. These results suggested mutual Hg-Se detoxification in T. malaccensis, which was highly dependent on the dosages and species of both elements. As compared to other species, SeMeth and MeHg promoted the Hg-Se joint effects to a higher degree. Additionally, the Hg contents decreased for all the Hg-Se co-exposed groups, revealing a sequestering effect of Se towards Hg in T. malaccensis.

Tracing aquatic bioavailable Hg in three different regions of China using fish Hg isotopes.

To trace the most concerned bioavailable mercury (Hg) in aquatic environment, fish samples were collected from three typical regions in China, including 3 rivers and 1 lake in the Tibetan Plateau (TP, a high altitude background region with strong solar radiation), the Three Gorges Reservoir (TGR, the largest artificial freshwater reservoir in China), and the Chinese Bohai Sea (CBS, a heavily human-impacted semi-enclosed sea). The Hg isotopic compositions in fish muscles were analyzed. The results showed that anthropogenic emissions were the main sources of Hg in fish from TGR and CBS because of the observed negative δ202Hg and positive Δ199Hg in these two regions (TGR, δ202Hg: - 0.72 to - 0.29‰, Δ199Hg: 0.15 - 0.52‰; CBS, δ202Hg: - 2.09 to - 0.86‰, Δ199Hg: 0.07 - 0.52‰). The relatively higher δ202Hg and Δ199Hg (δ202Hg: - 0.37 - 0.08‰, Δ199Hg: 0.50 - 1.89‰) in fish from TP suggested the insignificant disturbance from local anthropogenic activities. The larger slopes of Δ199Hg/Δ201Hg in fish from TGR (1.29 ± 0.14, 1SD) and TP (1.25 ± 0.06, 1SD) indicated methylmercury (MeHg) was produced and photo-reduced in the water column before incorporation into the fish. In contrast, the photoreduction of Hg2+ was the main process in CBS (slope of Δ199Hg/Δ201Hg: 1.06 ± 0.06, 1SD). According to the fingerprint data of Hg isotopes, the most important source for aquatic bioavailable Hg in TP should be the long-range transported Hg, contrasting to the anthropogenic originated MeHg from surface sediments and runoffs in TGR and inorganic Hg from continental inputs in CBS. Therefore, the isotopic signatures of Hg in fish can provide novel clues in tracing sources and behaviors of bioavailable Hg in aquatic systems, which are critical for further understanding the biogeochemical cycling of Hg.

Single-drop gold nanoparticles for headspace microextraction and colorimetric assay of mercury (II) in environmental waters.

A novel headspace colorimetric nanosensor strategy for specific detection of Hg(II) was developed based upon analyte induced etching and amalgamation of gold nanoparticles (AuNPs). The Hg(II) was first selectively reduced to its volatile form, Hg(0), by stannous chloride (SnCl2) through chemical cold vapor generation (CVG) reaction. Then, the Hg(0) was headspace extracted into 37µL thioglycolic acid functionalized AuNP aqueous suspension containing 10% methanol as extractant and simultaneously reacted with AuNPs through the strong metallophilic Hg-Au interaction, resulting in a red-to-blue color change. Parameters influencing the chromogenic and chemical vapor generation reactions were optimized. The limit of detections were determined as 5nM through inspection by naked-eye and 1nM based on measurements by UV-Vis spectrometer, which are below the safe limit of Hg(II) in drinking water set by the US Environmental Protection Agency, showing excellent potential for monitoring ultralow levels of Hg(II) in environmental water samples. The assay was not interfered by the presence of other common metal ions even at 1000-fold excess over Hg(II) concentration. The outstanding selectivity results from the combined effect of selective reduction of Hg(II) by SnCl2, efficient separation of sample matrix through headspace extraction, and amalgamation process that occurs specifically between Hg and AuNPs. The method was successfully applied to the visual detection of Hg(II) in environmental water samples at a 10nM spiking level, with recoveries in the range of 86.8-99.8%. More importantly, compared to classical colorimetric assays for detection of Hg(II), this method is featured with simplicity, quite high sensitivity and excellent selectivity. The method is also superior to most colorimetric methods for detection of Hg(II) in terms of its applicability to matrix-rich real samples including wastewater.

Tracking the Transformation of Nanoparticulate and Ionic Silver at Environmentally Relevant Concentration Levels by Hollow Fiber Flow Field-Flow Fractionation Coupled to ICPMS.

It is a great challenge to monitor the physical and chemical transformation of nanoparticles at environmentally relevant concentration levels, mainly because the commonly used techniques like dynamic light scattering and transmission electron microscopy are unable to characterize and quantify trace level nanoparticles in complex matrices. Herein, we demonstrate the on-line coupled system of hollow fiber flow field-flow fractionation (HF5), minicolumn concentration, and inductively coupled plasma mass spectrometry (ICPMS) detection as an efficient approach to study the aggregation and chemical transformation of silver nanoparticles (AgNPs) and ionic Ag species in the aqueous environment at ng/mL levels. Taking advantage of the in-line dialysis of HF5, the selective capture of Ag(I) species by the resin in minicolumn, and the high selectivity and sensitivity of ICPMS detection, we recorded the aggregation of 10 ng/mL AgNPs in complex matrices (e.g., NOM, Na+/Ca2+), revealing an interesting tiny AgNPs formation process of photoreduction of trace level Ag(I) that is different from larger AgNPs generated at high concentration of Ag(I) by accurate characterization and respectively identifying and quantifying new thiol-complexed Ag(I) and residual Ag(I) in the intertransformation of Ag(I) and AgNPs in domestic wastewater by simultaneously detecting the S and Ag signals via ICPMS.

Toward full spectrum speciation of silver nanoparticles and ionic silver by on-line coupling of hollow fiber flow field-flow fractionation and minicolumn concentration with multiple detectors.

The intertransformation of silver nanoparticles (AgNPs) and ionic silver (Ag(I)) in the environment determines their transport, uptake, and toxicity, demanding methods to simultaneously separate and quantify AgNPs and Ag(I). For the first time, hollow fiber flow field-flow fractionation (HF5) and minicolumn concentration were on-line coupled together with multiple detectors (including UV-vis spectrometry, dynamic light scattering, and inductively coupled plasma mass spectrometry) for full spectrum separation, characterization, and quantification of various Ag(I) species (i.e., free Ag(I), weak and strong Ag(I) complexes) and differently sized AgNPs. While HF5 was employed for filtration and fractionation of AgNPs (>2 nm), the minicolumn packed with Amberlite IR120 resin functioned to trap free Ag(I) or weak Ag(I) complexes coming from the radial flow of HF5 together with the strong Ag(I) complexes and tiny AgNPs (<2 nm), which were further discriminated in a second run of focusing by oxidizing >90% of tiny AgNPs to free Ag(I) and trapped in the minicolumn. The excellent performance was verified by the good agreement of the characterization results of AgNPs determined by this method with that by transmission electron microscopy, and the satisfactory recoveries (70.7-108%) for seven Ag species, including Ag(I), the adduct of Ag(I) and cysteine, and five AgNPs with nominal diameters of 1.4 nm, 10 nm, 20 nm, 40 nm, and 60 nm in surface water samples.

Effects of molecular weight-dependent physicochemical heterogeneity of natural organic matter on the aggregation of fullerene nanoparticles in mono- and di-valent electrolyte solutions.

Given the wide presence of heterogeneous natural organic matter (NOM) and metal ions (Na(+)/Ca(2+)/Mg(2+)), as well as their significant role in governing nanoparticle stability in aqueous environments, it is of great importance to understand how the molecular weight (MW)-dependent physicochemical properties of NOM impact fundamental transportation processes like the aggregation of engineered nanoparticles (ENPs) in the presence of Na(+)/Ca(2+)/Mg(2+). Here, we report on the aggregation behavior of a model ENP, fullerene nanoparticles (nC60) in the presence of five MW fractions of Suwannee River NOM (Mf-SRNOMs, separated by ultrafiltration techniques) and three electrolytes (NaCl, CaCl2 and MgCl2). We found that in all NaCl treatments and low concentration CaCl2/MgCl2 treatments, the enhancement of nC60 stability positively correlated with the MW of Mf-SRNOMs. Whereas, the stability efficiency of identical Mf-SRNOM in different electrolytes followed an order of NaCl > MgCl2 > CaCl2, and the enhanced attachment of nC60-SRNOM associations was observed in high MW Mf-SRNOM (SRNOM>100 kD and SRNOM 30-100 kD) at high concentration CaCl2/MgCl2. Our results indicate that although the high MW NOM with large humic-like material is the key component for stabilizing nC60 in monovalent electrolyte, it could play a reversed role in promoting the attachment of nC60, especially in long term aggregations and at high concentrations of divalent cations. Therefore, a detailed understanding of the effects of heterogeneous NOM on the aggregation of ENPs should be highly valued, and properly assessed against different cation species and concentrations.

Colorimetric Au nanoparticle probe for speciation test of arsenite and arsenate inspired by selective interaction between phosphonium ionic liquid and arsenite.

The exposure of millions of people to unsafe levels of arsenite (AsIII) and arsenate (AsV) in drinking waters calls for the development of low-cost methods for on-site monitoring these two arsenic species in waters. Herein, for the first time, tetradecyl (trihexyl) phosphonium chloride ionic liquid was found to selectively bind with AsIII via extended X-ray absorption fine structure (EXAFS) analysis. Based on the finding, an AsIII-specific probe was developed by modifying gold nanoparticles with the ionic liquid. Futhermore, Hofmeister effect was primarily observed to significantly affect the sensitivity of gold nanoparticle probe. With the colorimetric probe, we developed a protocol for naked eye speciation test of AsIII and AsV at levels below the World Health Organization (WHO) guideline of 10 µg L(-1). This method featured with high tolerance to common coexisting ions such as 10 mM PO4(3-), and was validated by assaying certified reference and environmental water samples.

Highly dynamic PVP-coated silver nanoparticles in aquatic environments: chemical and morphology change induced by oxidation of Ag(0) and reduction of Ag(+).

The fast growing and abundant use of silver nanoparticles (AgNPs) in commercial products alerts us to be cautious of their unknown health and environmental risks. Because of the inherent redox instability of silver, AgNPs are highly dynamic in the aquatic system, and the cycle of chemical oxidation of AgNPs to release Ag(+) and reconstitution to form AgNPs is expected to occur in aquatic environments. This study investigated how inevitable environmentally relevant factors like sunlight, dissolved organic matter (DOM), pH, Ca(2+)/Mg(2+), Cl(-), and S(2-) individually or in combination affect the chemical transformation of AgNPs. It was demonstrated that simulated sunlight induced the aggregation of AgNPs, causing particle fusion or self-assembly to form larger structures and aggregates. Meanwhile, AgNPs were significantly stabilized by DOM, indicating that AgNPs may exist as single particles and be suspended in natural water for a long time or delivered far distances. Dissolution (ion release) kinetics of AgNPs in sunlit DOM-rich water showed that dissolved Ag concentration increased gradually first and then suddenly decreased with external light irradiation, along with the regeneration of new tiny AgNPs. pH variation and addition of Ca(2+) and Mg(2+) within environmental levels did not affect the tendency, showing that this phenomenon was general in real aquatic systems. Given that a great number of studies have proven the toxicity of dissolved Ag (commonly regarded as the source of AgNP toxicity) to many aquatic organisms, our finding that the effect of DOM and sunlight on AgNP dissolution can regulate AgNP toxicity under these conditions is important. The fact that the release of Ag(+) and regeneration of AgNPs could both happen in sunlit DOM-rich water implies that previous results of toxicity studies gained by focusing on the original nature of AgNPs should be reconsidered and highlights the necessity to monitor the fate and toxicity of AgNPs under more environmentally relevant conditions.

Quantification of the uptake of silver nanoparticles and ions to HepG2 cells.

The toxic mechanism of silver nanoparticles (AgNPs) is still debating, partially because of the common co-occurrence and the lack of methods for separation of AgNPs and Ag(+) in biological matrices. For the first time, Triton-X 114-based cloud point extraction (CPE) was proposed to separate AgNPs and Ag(+) in the cell lysates of exposed HepG2 cells. Cell lysates were subjected to CPE after adding Na2S2O3, which facilitated the transfer of AgNPs into the nether Triton X-114-rich phase by salt effect and the preserve of Ag(+) in the upper aqueous phase through the formation of hydrophilic complex. Then the AgNP and Ag(+) contents in the exposed cells were determined by ICP-MS after microwave digestion of the two phases, respectively. Under the optimized conditions, over 67% of AgNPs in cell lysates were extracted into the Triton X-114-rich phase while 94% of Ag(+) remained in the aqueous phase, and the limits of detection for AgNPs and Ag(+) were 2.94 µg/L and 2.40 µg/L, respectively. This developed analytical method was applied to quantify the uptake of AgNPs to the HepG2 cells. After exposure to 10 mg/L AgNPs for 24 h, about 67.8 ng Ag were assimilated per 10(4) cells, in which about 10.3% silver existed as Ag(+). Compared to the pristine AgNPs (with 5.2% Ag(+)) for exposure, the higher ratio of Ag(+) to AgNPs in the exposed cells (10.3% Ag(+)) suggests the transformation of AgNPs into Ag(+) in the cells and/or the higher uptake rate of Ag(+) than that of AgNPs. Given that the toxicity of Ag(+) is much higher than that of AgNPs, the substantial content of Ag(+) in the exposed cells suggests that the contribution of Ag(+) should be taken into account in evaluating the toxicity of AgNPs to organisms, and previous results obtained by regarding the total Ag content in organisms as AgNPs should be reconsidered.

Silver nanoparticles in the environment.

Silver nanoparticles (AgNPs) are well known for their excellent antibacterial ability and superior physical properties, and are widely used in a growing number of applications ranging from home disinfectants and medical devices to water purificants. However, with the accelerating production and introduction of AgNPs into commercial products, there is likelihood of release into the environment, which raises health and environmental concerns. This article provides a critical review of the state-of-knowledge about AgNPs, involving the history, analysis, source, fate and transport, and potential risks of AgNPs. Although great efforts have been made in each of these aspects, there are still many questions to be answered to reach a comprehensive understanding of the positive and negative effects of AgNPs. In order to fully investigate the fate and transport of AgNPs in the environment, appropriate methods for the preconcentration, separation and speciation of AgNPs should be developed, and analytical tools for the characterization and detection of AgNPs in complicated environmental samples are also urgently needed. To elucidate the environmental transformation of AgNPs, the behavior of AgNPs should be thoroughly monitored in complex environmental relevant conditions. Furthermore, additional in vivo toxicity studies should be carried out to understand the exact toxicity mechanism of AgNPs, and to predict the health effects to humans.

In vivo antioxidant activity of total flavonoids from indocalamus leaves in aging mice caused by D-galactose.

OBJECTIVE: The aim of this thesis is to explore antioxidant activity of total flavonoids extracted from indocalamus leaves. METHOD: Aging mice model was established by D-galactose induction. Three groups of mice were treated with total flavonoids extracted from indocalamus leaves at doses of 20, 40 and 80 mg/kg d bw respectively. The antioxidant status in the aging mice was measured by determining the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) and total anti-oxidant capability (T-AOC) in the serum and liver and malondialdehyde (MDA) content in the serum, liver and brain. RESULTS: Compared with control group, extracts of indocalamus leaves significantly enhanced activities of SOD, GSH-Px, CAT in the serum and liver, and decreased MDA content in the serum, liver and brain at the tested doses. CONCLUSION: Total flavonoids extracted from indocalamus leaves demonstrated the potent antioxidant activity.

Development of an ultra-high-performance liquid chromatography-tandem mass spectrometry method for high throughput determination of organophosphorus flame retardants in environmental water.

Widely used as flame retardants, organophosphate esters (OPEs) are now broadly present in the indoor and outdoor environments. Currently available liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods share some drawbacks with gas chromatography (GC) methods, including time consuming, limited target OPEs, incomplete separation capability for some OPEs and low throughput. In this study, a fast and high throughput LC-MS/MS method was developed. For the first time, all the twelve OPEs that have been studied in literature, ranging from the very polar and volatile trimethyl phosphate to the very hydrophobic and non-volatile tris(2-ethylhexyl) phosphate, were separated within 11 min. Different from previous studies, we found that the blank contamination was mainly from organic mobile phase rather than the enrichment process, and it can be efficiently eliminated by using acetonitrile rather than methanol as the organic phase of the mobile phase. The signal to noise ratio (S/N) was significantly improved by using 0.1% formic acid as an organic modifier. The method exhibited high throughput and sensitivity and can baseline separate 11 of the 12 OPEs studied within 11 min with LOQs ranging from 2 to 6 ng/L. The relative standard deviations were in the range of 2-10%. For both reagent water and river water, the spiked recoveries of OPEs ranged from 70 to 110%, except for the very polar and volatile trimethyl phosphate that has recovery below 10%. The developed procedure was successfully applied to study the OPE contamination of the Songhua River, and it was found that all the target OPEs were detected with total concentrations of around 1 µg/L in the river waters.

Speciation analysis of silver nanoparticles and silver ions in antibacterial products and environmental waters via cloud point extraction-based separation.

The rapid growth in commercial use of silver nanoparticles (AgNPs) will inevitably increase silver exposure in the environment and the general population. As the fate and toxic effects of AgNPs is related to the Ag(+) released from AgNPs and the transformation of Ag(+) into AgNPs, it is of great importance to develop methods for speciation analysis of AgNPs and Ag(+). This study reports the use of Triton X-114-based cloud point extraction as an efficient separation approach for the speciation analysis of AgNPs and Ag(+) in antibacterial products and environmental waters. AgNPs were quantified by determining the Ag content in the Triton X-114-rich phase with inductively coupled plasma mass spectrometry (ICPMS) after microwave digestion. The concentration of total Ag(+), which consists of the AgNP adsorbed, the matrix associated, and the freely dissolved, was obtained by subtracting the AgNP content from the total silver content that was determined by ICPMS after digestion. The limits of quantification (S/N = 10) for antibacterial products were 0.4 µg/kg and 0.2 µg/kg for AgNPs and total silver, respectively. The reliable quantification limit was 3 µg/kg for total Ag(+). The presence of Ag(+) at concentrations up to 2-fold that of AgNPs caused no effects on the determination of AgNPs. In the cloud point extraction of AgNPs in antibacterial products, the spiked recoveries of AgNPs were in the range of 71.7-103% while the extraction efficiencies of Ag(+) were in the range of 1.2-10%. The possible coextracted other silver containing nanoparticles in the cloud point extraction of AgNPs were distinguished by transmission electron microscopy (TEM), scanning electron microscopy (SEM)- energy dispersive spectroscopy (EDS), and UV-vis spectrum. Real sample analysis indicated that even though the manufacturers claimed nanosilver products, AgNPs were detected only in three of the six tested antibacterial products.