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Carbonyls have an important effect on atmospheric chemistry and human health because of their high electrophilicity. Here, high-throughput screening of carbonyl molecules in complex aerosol samples was achieved by combining targeted derivatization with non-targeted analysis using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Results showed that water-soluble organic matter (WSOM) in PM2.5 contains a large variety carbonyls (5147 in total), accounting for 17.6% of all identified organic molecules. Compared with non-carbonyl molecules, carbonyl molecules are more abundant in winter than in summer, and have unique molecular composition and chemical parameters. For the first time, a significant positive correlation was found between the abundance of carbonyl molecules and the dithiothreitol (DTT) activities of WSOM, and the elimination of the carbonyl group remarkably reduced the DTT activities, highlighting the pivotal role of carbonyls in determining the oxidative potential (OP) of organic aerosol. Among various molecules, oxidized aromatic compounds containing the carbonyl group produced in winter contributed more to the enhancement of DTT activity, which could be used as potential markers of atmospheric oxidative stress. This study improves our understanding of the chemical diversity and environmental health effects of atmospheric carbonyls, emphasizing the need for targeted strategies to mitigate the health risks associated with carbonyl-rich aerosols. [ABSTRACT FROM AUTHOR]

Natural organic matter (NOM) is a complex organic mixture and plays a crucial role in environmental processes. By using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), detailed molecular information on NOM could be achieved. In this paper, ion accumulation time (IAT), a key parameter of FTICR-MS for complex mixture detection, was the focus, and its effect on the molecular characterization of NOM by FTICR-MS was systematically investigated. A notable feature of selective detection of NOM molecules by FTICR-MS with different IAT was observed. Most of the polar molecules with high O/C ratio (O/C ratio >0.5) could be easily detected by FTICR-MS with a short IAT, but extending IAT led to the ion intensities of these molecules decreasing or even disappearing. Meanwhile, a large number of unsaturated and aromatic molecules with low O/C ratio (O/C ratio <0.6) and low polarity, all of which could not be observed with a short IAT, were remarkably detected by extending IAT. Results also revealed that the unsaturated and aromatic molecules, which could only be observed by extending the IAT, were not generated by the fragmentation of molecules in NOM or from the dissociation of NOM aggregations but originally existed in NOM samples. The selective detection of NOM molecules caused by IAT extension was possibly attributed to their different polarity and different stability in the collision cell. On the basis of these results, a novel strategy of combining mass spectrometric data of NOM obtained with different IAT by FTICR-MS was proposed. With this strategy, more than 4715 CHO-molecular formulas were assigned, where about 2000 more formulas were obtained in comparison with using a short IAT (2733 CHO-molecular formulas identified) solely. The strategy is simple and robust and can be used as an alternative method to obtain more molecular information on NOM in the environment. [ABSTRACT FROM AUTHOR]

Adsorption by minerals is a common geochemical process of dissolved organic matter (DOM) which may induce fractionation of DOM at the mineral-water interface. Here, we examine the molecular fractionation of DOM induced by adsorption onto three common iron oxyhydroxides using electrospray ionization coupled with Fouriertransform ion cyclotron resonance mass spectrometry (ESI-FT-ICRMS). Ferrihydrite exhibited higher affinity to DOM and induced more pronounced molecular fractionation of DOM than did goethite or lepidocrocite. High molecular weight (>500 Da) compounds and compounds high in unsaturation or rich in oxygen including polycyclic aromatics, polyphenols and carboxylic compounds had higher affinity to iron oxyhydroxides and especially to ferrihydrite. Low molecular weight compounds and compounds low in unsaturation or containing few oxygenated groups (mainly alcohols and ethers) were preferentially maintained in solution. This study confirms that the double bond equivalence and the number of oxygen atoms are valuable parameters indicating the selective fractionation of DOM at mineral and water interfaces. The results of this study provide important information for further understanding the behavior of DOM in the natural environment. [ABSTRACT FROM AUTHOR]

It is imperative to obtain information on the binding sites and distribution of organic contaminants in soils in order to understand their reactions and fates in soils. Here we propose a novel strategy that enables in situ observation at the micrometer scale of the spatial distribution of organobromine compounds and characterization of their associations with organic carbon (OC) forms (i.e., C-functional groups) in soils. According to the strategy, two complementary synchrotron radiation-based spectroscopic techniques (i.e., Fourier transform-infrared (FT-IR) and micro X-ray fluorescence (μ-XRF) spectromicroscopies) were applied to characterize the binding sites and distribution of Br (as a conservative tracer for organobromine compounds), OC forms, clay minerals, and other mineral elements within soil particles, respectively, at a 6-10 μm-scale spatial resolution. This study is the first in situ investigation on the microscale locations of organobromine compounds at environmental levels and their associations with OC forms and clay mineral/elements in natural soils. The strategy paves the way toward in situ characterization of the distribution, speciation, and binding sites of some organic contaminants, which is critical in understanding their associated environmental processes in soils. [ABSTRACT FROM AUTHOR]

Sulfur speciation under the influence of sample pretreatment and sewage sludge (SS) application in a continuously SS-amended soil was assessed by wet-chemical fractionation and S K-edge XANES spectroscopy. Distinct differences in S speciation among the following pretreatments including fresh, air-drying, anoxic freeze-drying, oven-drying, and conditioning (incubation at room temperature and 75% of water holding capacity for 2 wk) were detected in both topsoils and subsoils. Air-drying significantly increased available S content but decreased C-bonded S content in the soils compared with anoxic freeze-drying. Oven-drying and conditioning pretreatments showed a similar effect on S fractions to air-drying in the soils but to a lesser extent. X-ray adsorption near-edge structure analysis showed that both reduced and intermediate organic S tended to decrease while oxidized S obviously increased in the air-dried samples. In contrast, the conditioning pretreatment facilitated the transformation of intermediate S into reduced organic S. Continuous application of SS significantly increased total soil S, C-bonded S, and residual S contents but decreased available S content in the topsoil. Meanwhile, XANES analysis indicated that reduced organic S was markedly increased (over 50% of total S) in the SS-amended topsoil. No obvious effect of the application of SS on S speciation in the subsoil was observed except for the facilitated transportation of S into lower depth. Overall, our results suggest that anoxic atmospheres during the entire pretreatment process from sampling to drying, grinding, and analysis is crucial for the accurate speciation analysis of S in soils, and the anoxic freeze-drying is, therefore, highly recommended. [ABSTRACT FROM AUTHOR]

The toxicity and fate of nanoparticles (NPs) have been reported to be highly dependent on the chemistry of the medium, and the effects of phosphate have tended to be ignored despite the wide existence of phosphate contamination in aqueous environments. In the present study the influence of phosphate on the dissolution and microstructural transformation of ZnO NPs was investigated. Phosphate at a low concentration rapidly and substantially reduced the release of Zn2+ into aqueous solution. Synchrotron X-ray absorption spectroscopy and X-ray diffraction analysis reveal that interaction between ZnO NPs and phosphate induced the transformation of ZnO into zinc phosphate. Transmission electronic microscopy observation shows that the morphology of the particles changed from structurally uniform nanosized spherical to anomalous and porous material containing mixed amorphous and crystalline phases of ZnO and zinc phosphate in the presence of phosphate. To our knowledge, this is the first study in which the detailed process of phosphate-induced speciation and microstructural transformation of ZnO NPs has been analyzed. In view of the wide existence of phosphate contamination in water and its strong metal-complexation capability, phosphate-induced transformations may play an important role in the behaviors, fate, and toxicity of many other metal-based nanomaterials in the environment. [ABSTRACT FROM AUTHOR]

The adsorption kinetics, isotherms and thermodynamics of Cr(III) on graphene oxide (GO) were studied. The adsorption kinetic data were well described with pseudo-second-order model and the equilibrium data were well fitted by Langmuir model. The calculated thermodynamic parameters indicated that the adsorption of Cr(III) on GO was spontaneous and endothermic. The maximum adsorption capacity of Cr(III) on GO at pH 5.0 and T = 296 K was about 92.65 mg g-1, which was higher than other reported adsorbents. It was found that the adsorption of Cr(III) on GO was strongly dependent on solution pH, but weakly dependent on ionic strength. Fourier transform infrared (FTIR) spectra suggested that Cr(III) was adsorbed on GO mainly through the formation of inner-sphere complexes with the O-containing functional groups on GO surface. Results in this study suggested that GO was a suitable material for the preconcentration and removal of Cr(III) from water. [ABSTRACT FROM AUTHOR]