Investigation on the Structure of Water/AOT/IPM/Alcohols Reverse Micelles by Conductivity, Dynamic Light Scattering, and Small Angle X-ray Scattering

We have systematically investigated the effect of alcohols (ethanol, propanol, butanol, and pentanol) on the structure of the water/AOT/IPM system using conductivity, dynamic light scattering (DLS), and small-angle X-ray scattering (SAXS) techniques. The results show that no percolation phenomenon is observed in the water/AOT/IPM system, whereas the addition of ethanol (propanol and butanol) induces apparently percolation. The threshold water content (<i>W</i>_p) depends closely on the alcohol type and concentration. The effect of alcohols on the conductance behavior is discussed from the physical properties of alcohols, the interfacial flexibility, and the attractive interactions between droplets. The hydrodynamic diameter of droplets (<i>d</i>_H) obtained from DLS increases markedly with the increase in water content (<i>W</i>₀); however, it decreases gradually with increasing alcohol chain length and concentration. SAXS measurements display distinctly the shoulder, the low hump peaks, and the heavy tail phenomenon in the pair distance distribution function <i>p</i>(<i>r</i>) profile, which rely strongly on the alcohol species and its concentration. The gyration radius (<i>R</i>_g) increases with increasing <i>W</i>₀, and decreases with the increase of alcohol chain length and concentration. Schematic diagram of the conductance mechanism of water/AOT/IPM/alcohol systems is primarily depicted. Three different phases of the discrete droplets, the oligomers, and the isolated ellipsoidal droplets existed in the different <i>W</i>₀ ranges correspond to three different stages in the conductivity–<i>W</i>₀ curve. Coupling the structure characteristics of reverse micelles obtained from DLS and SAXS techniques with conductivity could be greatly helpful to deeply understand the percolation mechanism of water/AOT/IPM/alcohols systems

Pure Anisotropic Hydrogel with an Inherent Chiral Internal Structure Based on the Chiral Nematic Liquid Crystal Phase of Rodlike Viruses

Imparting ordered structures into otherwise amorphous hydrogels is expected to endow these popular materials with novel multiple-stimuli responsiveness that promises many applications. The current contribution reports a method to fabricate pure polymeric hydrogels with an inherent chiral internal structure by templating on the chiral nematic liquid crystal phase of a rodlike virus. A method was developed to form macroscopically homogeneous chiral templates by confinement induced self-assembly in the presence of monomers, cross-linkers and initiators. Polymerization induced gelation was performed without perturbing the elegant 3D chiral organization of the rodlike virus bearing double bonds. Furthermore, a suitable method was found to remove the organic virus template while keeping the desired polymeric replica intact, resulting in a pure polymeric hydrogel with a unique internal chiral feature that originates from the 3D chiral ordering of the cylindrical pores left by the virus. Multiple-stimuli responsiveness has been demonstrated and can be quantified by the change of the pitch of the chiral feature. The chiral structure endows the otherwise featureless hydrogel with a unique material property that might be used as a readout signal for sensing and acts as the basis for responsive, biomimetic nanostructured materials

Pure Anisotropic Hydrogel with an Inherent Chiral Internal Structure Based on the Chiral Nematic Liquid Crystal Phase of Rodlike Viruses

Imparting ordered structures into otherwise amorphous hydrogels is expected to endow these popular materials with novel multiple-stimuli responsiveness that promises many applications. The current contribution reports a method to fabricate pure polymeric hydrogels with an inherent chiral internal structure by templating on the chiral nematic liquid crystal phase of a rodlike virus. A method was developed to form macroscopically homogeneous chiral templates by confinement induced self-assembly in the presence of monomers, cross-linkers and initiators. Polymerization induced gelation was performed without perturbing the elegant 3D chiral organization of the rodlike virus bearing double bonds. Furthermore, a suitable method was found to remove the organic virus template while keeping the desired polymeric replica intact, resulting in a pure polymeric hydrogel with a unique internal chiral feature that originates from the 3D chiral ordering of the cylindrical pores left by the virus. Multiple-stimuli responsiveness has been demonstrated and can be quantified by the change of the pitch of the chiral feature. The chiral structure endows the otherwise featureless hydrogel with a unique material property that might be used as a readout signal for sensing and acts as the basis for responsive, biomimetic nanostructured materials

Air–Seawater Exchange of Organochlorine Pesticides along the Sediment Plume of a Large Contaminated River

Gaseous exchange fluxes of organochlorine pesticides (OCPs) across the air–water interface of the coastal East China Sea were determined in order to assess whether the contaminated plume of the Yangtze River could be an important regional source of OCPs to the atmosphere. Hexa­chloro­cyclo­hexanes (HCHs), chlordane compounds (CHLs), and dichloro­diphenyl­trichloro­ethanes (DDTs) were the most frequently detected OCPs in air and water. Air–water exchange was mainly characterized by net volatilization for all measured OCPs. The net gaseous exchange flux ranged 10–240 ng/(m²·day) for γ-HCH, 60–370 ng/(m²·day) for <i>trans</i>-CHL, 97–410 ng/(m²·day) for <i>cis</i>-CHL, and ∼0 (e.g., equilibrium) to 490 ng/(m²·day) for <i>p</i>,<i>p</i>′-DDE. We found that the plume of the large contaminated river can serve as a significant regional secondary atmospheric source of legacy contaminants released in the catchment. In particular, the sediment plume represented the relevant source of DDT compounds (especially <i>p</i>,<i>p</i>′-DDE) sustaining net degassing when clean air masses from the open ocean reached the plume area. In contrast, a mass balance showed that, for HCHs, contaminated river discharge (water and sediment) plumes were capable of sustaining volatilization throughout the year. These results demonstrate the inconsistencies in the fate of HCHs and DDTs in this large estuarine system with declining primary sources

Assessing and Forecasting Atmospheric Outflow of α-HCH from China on Intra-, Inter-, and Decadal Time Scales

Atmospheric outflow of α-HCH from China from 1952 to 2009 was investigated using Chinese Gridded Pesticide Emission and Residue Model (ChnGPERM). The model results show that the outflows via the northeast boundary (NEB, longitude 115–135 °E along 55 °N and latitude 37–55 °N along 135 °E) and the mid-south boundary (MSB, longitude 100–120 °E along 17 °N) of China account for 47% and 35% of the total outflow, respectively. Two climate indices based on the statistical association between the time series of modeled α-HCH outflow and atmospheric sea-level pressure were developed to predict the outflow on different time scales. The first index explains 70/83% and 10/46% of the intra-annual variability of the outflow via the NEB and MSB during the periods of 1952–1984 and 1985–2009, respectively. The second index explains 16% and 19% of the interannual and longer time scale variability in the outflow through the NEB during June–August and via the MSB during October–December for 1991–2009, respectively. Results also revealed that climate warming may potentially result in stronger outflow via the NEB than the MSB. The linkage between the outflow with large scale atmospheric circulation patterns and climate warming trend over China was also discussed

Assessing Cancer Risk in China from γ‑Hexachlorocyclohexane Emitted from Chinese and Indian Sources

Three models, including an atmospheric transport model, a multimedia exposure model, and a risk assessment model, were used to assess cancer risk in China caused by γ-HCH (gamma-hexachlorocyclohexane) emitted from Chinese and Indian sources. Extensive model investigations revealed the contribution of different sources to the cancer risk in China. Cancer risk in Eastern China was primarily attributable to γ-HCH contamination from Chinese sources, whereas cancer risk in Western China was caused mostly by Indian emissions. The contribution of fresh use of lindane in India to the cancer risk in China was almost 1 order of magnitude higher than that of the reemission of γ-HCH from Indian soils. Of total population, 58% (about 0.79 billion) residents in China were found to live in the environment with high levels of cancer risk exceeding the acceptable cancer risk of 10^–6, recommended by the United States Environmental Protection Agency (U.S. EPA). The cancer risk in China was mostly induced by the local contamination of γ-HCH emitted from Chinese sources, whereas fresh use of lindane in India will become a significant source of the cancer risk in China if Indian emissions maintain their current levels

Assessing Environmental Fate of β‑HCH in Asian Soil and Association with Environmental Factors

Chinese Gridded Pesticide Emission and Residue Model was applied to simulate long-term environmental fate of β-HCH in Asia spanning 1948–2009. The model captured well the spatiotemporal variation of β-HCH soil concentrations across the model domain. β-HCH use in different areas within the model domain was simulated respectively to assess the influence of the different sources of β-HCH on its environment fate. A mass center of soil residue (MCSR) was introduced and used to explore environmental factors contributing to the spatiotemporal variation of β-HCH soil residue. Results demonstrate that the primary emission dominates β-HCH soil residues during the use of this pesticide. After phase-out of the pesticide in 1999, the change in β-HCH soil residues has been associated with the Asian summer monsoon, featured by northward displacement of the MCSR. The displacement from several major sources in China and northeastern Asia shows a downward trend at a 95% confidence level, largely caused by environmental degradation and northward delivery of β-HCH under cold condition in northern area. The MCSRs away from the India and southern and southeastern Asia sources show a rapid northward displacement at a 99% confidence level, featuring the cold trapping effect of the Tibetan Plateau

First Assessment of NO_<i>x</i> Sources at a Regional Background Site in North China Using Isotopic Analysis Linked with Modeling

Nitrogen oxides (NO_<i>x</i>, including NO and NO₂) play an important role in the formation of atmospheric particles. Thus, NO_<i>x</i> emission reduction is critical for improving air quality, especially in severely air-polluted regions (e.g., North China). In this study, the source of NO_<i>x</i> was investigated by the isotopic composition (δ¹⁵N) of particulate nitrate (p-NO₃^–) at Beihuangcheng Island (BH), a regional background site in North China. It was found that the δ¹⁵N-NO₃^– (<i>n</i> = 120) values varied between −1.7‰ and +24.0‰ and the δ¹⁸O-NO₃^– values ranged from 49.4‰ to 103.9‰. On the basis of the Bayesian mixing model, 27.78 ± 8.89%, 36.53 ± 6.66%, 22.01 ± 6.92%, and 13.68 ± 3.16% of annual NO_<i>x</i> could be attributed to biomass burning, coal combustion, mobile sources, and biogenic soil emissions, respectively. Seasonally, the four sources were similar in spring and fall. Biogenic soil emissions were augmented in summer in association with the hot and rainy weather. Coal combustion increased significantly in winter with other sources showing an obvious decline. This study confirmed that isotope-modeling by δ¹⁵N-NO₃^– is a promising tool for partitioning NO_<i>x</i> sources and provides guidance to policymakers with regard to options for NO_<i>x</i> reduction in North China

High Time- and Size-Resolved Measurements of PM and Chemical Composition from Coal Combustion: Implications for the EC Formation Process

Inefficient coal combustion is a significant source of elemental carbon (EC) air pollution in China, but there is a limited understanding of EC’s formation processes. In this study, high time-resolved particle number size distributions (PNSDs) and size-resolved chemical compositions were obtained from the combustion of four bituminous coals burned in a quartz tube furnace at 500 and 800 °C. Based on the distinct characteristics of PNSD, the flaming stage was divided into the first-flaming stage (with a PNSD peak at 0.3–0.4 μm) and the second-flaming stage (with a PNSD peak at 0.1–0.15 μm). For the size-segregated EC and OC measurements, more soot-EC was observed in particles larger than 0.3 μm, whereas the smaller ones possessed more char-EC. The results indicated that gas-phase and direct-conversion EC generation mechanisms dominate different burning stages. The analysis of 16 parent PAHs showed more high-molecular-weight PAHs in the second-flaming stage particles, which supports the idea of different formation processes for char-EC and soot-EC. For all four coals, the PNSD and chemical compositions shared a similar trend, confirming that the different formation processes of EC in different flaming stages were common. This study provides novel information concerning EC formation

Residential Coal Combustion as a Source of Levoglucosan in China

Levoglucosan (LG) has been widely identified as a specific marker for biomass burning (BB) sources and frequently utilized in estimating the BB contribution to atmospheric fine particles all over the world. However, this study provides direct evidence to show that coal combustion (CC) is also a source of LG, especially in the wintertime in Northern China, based on both source testing and ambient measurement. Our results show that low-temperature residential CC could emit LG with emission factors (EF) ranging from 0.3 to 15.9 mg kg^–1. Ratios of LG to its isomers, mannosan and galactosan, differ between CC and BB emissions, and the wintertime ratios in Beijing ambient PM_2.5 and source-specific tracers including carbon isotopic signatures all indicated a significant contribution from CC to ambient levoglucosan in winter in Beijing. The results suggest that LG cannot be used as a distinct source marker for biomass burning in special cases such as some cities in the northern China, where coal is still widely used in the residential and industrial sectors. Biomass burning sources could be overestimated, although such an over-estimation could vary spatially and temporally