Indoor phthalate levels were investigated in 28 buildings, including 14 office and 14 residential buildings in Xi'an, China. Phthalate esters in the gas-, particle-, and dust- phase were measured ...separately. Four phthalates including dimethyl phthalate (DMP), diisobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP) and di(2-ethylhexyl) phthalate (DEHP) were detected. The detection frequency of DnBP and DEHP was more than 90%. The concentrations of total phthalate esters ranged from 0.20 to 8.29 μg m−3 for the gas- phase, from 0.09 to 14.77 μg m−3 for the particle- phase and from 123 to 9504 μg g−1 for the dust- phase. The individual phthalate with the highest concentrations of 6.17 μg m−3, 7.97 μg m−3 and 7228 μg g−1 respectively for gas-, particle- and dust- phase in all investigated rooms is all DiBP. The median concentration of the gas- and particle-phase DiBP (0.52 and 0.72 μg m−3) and dust-phase DEHP (582 μg g−1) were the highest. It was also found that the average concentrations of individual phthalates in residential buildings were often higher than in office buildings, and correlation analysis indicated that DiBP, DnBP and DEHP might come from the same sources. Based on the gas- and particle-phase concentrations measured, the particle-air partition coefficients of phthalates were estimated, and their logarithm values were found to be linearly correlated with the logarithm values of their octanol-air partition coefficients. Finally, the total daily exposure to indoor phthalates in air and dust was calculated, and ranged from 2.6 μg kg−1 day−1 (for adults) to 7.4 μg kg−1 day−1 (for toddlers).
•We measured indoor phthalates in air and dust from 28 buildings in Xi'an, China.•Di-n-butyl phthalate (DnBP) and di(2-ethylhexyl) phthalate (DEHP) are the most abundant phthalates indoors in Xi'an.•Correlation analysis shows indoor diisobutyl phthalate (DiBP), DnBP and DEHP might come from the same sources.•The daily exposure to indoor phthalates in Xi'an was estimated.
A mechanistic model that considers particle dynamics and their effects on surface emissions and sorptions was developed to predict the fate and transport of phthalates in indoor environments. A ...controlled case study was conducted in a test house to evaluate the model. The model‐predicted evolving concentrations of benzyl butyl phthalate in indoor air and settled dust and on interior surfaces are in good agreement with measurements. Sensitivity analysis was performed to quantify the effects of parameter uncertainties on model predictions. The model was then applied to a typical residential environment to investigate the fate of di‐2‐ethylhexyl phthalate (DEHP) and the factors that affect its transport. The predicted steady‐state DEHP concentrations were 0.14 μg/m3 in indoor air and ranged from 80 to 46 000 μg/g in settled dust on various surfaces, which are generally consistent with the measurements of previous studies in homes in different countries. An increase in the mass concentration of indoor particles may significantly enhance DEHP emission and its concentrations in air and on surfaces, whereas increasing ventilation has only a limited effect in reducing DEHP in indoor air. The influence of cleaning activities on reducing DEHP concentration in indoor air and on interior surfaces was quantified, and the results showed that DEHP exposure can be reduced by frequent and effective cleaning activities and the removal of existing sources, though it may take a relatively long period of time for the levels to drop significantly. Finally, the model was adjusted to identify the relative contributions of gaseous sorption and particulate‐bound deposition to the overall uptake of semi‐volatile organic compounds (SVOCs) by indoor surfaces as functions of time and the octanol‐air partition coefficient (Koa) of the chemical. Overall, the model clarifies the mechanisms that govern the emission of phthalates and the subsequent interactions among air, suspended particles, settled dust, and interior surfaces. This model can be easily extended to incorporate additional indoor source materials/products, sorption surfaces, particle sources, and room spaces. It can also be modified to predict the fate and transport of other SVOCs, such as phthalate‐alternative plasticizers, flame retardants, and biocides, and serves to improve our understanding of human exposure to SVOCs in indoor environments.
Abstract
With terahertz irradiation with a specific frequency, the fibrotic progression of β-amyloid oligomers is suppressed, which provides a potential therapeutic strategy for Alzheimer’s disease.
The unrestricted control of circularly polarized (CP) terahertz (THz) waves is important in science and applications, but conventional THz devices suffer from issues of bulky size and low efficiency. ...Although Pancharatnam-Berry (PB) metasurfaces have shown strong capabilities to control CP waves,
-mode PB devices realized in the THz regime are less efficient, limiting their applications in practice. Here, based on Jones matrix analysis, we design a tri-layer structure (thickness of ~λ/5) and experimentally demonstrate that the structure can serve as a highly efficient
meta-atom (relative efficiency of ~90%) to build PB metadevices for manipulating CP THz waves. Two ultrathin THz metadevices are fabricated and experimentally characterized with a
-scan THz imaging system. The first device can realize a photonic spin Hall effect with an experimentally demonstrated relative efficiency of ~90%, whereas the second device can generate a high-quality background-free CP Bessel beam with measured longitudinal and transverse field patterns that exhibit the nondiffracting characteristics of a Bessel beam. All the experimental results are in excellent agreement with full-wave simulations. Our results pave the way to freely manipulate CP THz beams, laying a solid basis for future applications such as biomolecular control and THz signal transportation.
The health of city inhabitants is considerably impacted by the urban park green spaces (UPGS). Existing studies lack an assessment of the UPGS equity from different perspectives and are limited to ...poor accuracy. This study reviews the definition and determination methods of UPGS, as well as UPGS accessibility and spatial equity related studies. Then, a spatial equity evaluation system is established from the dimensions of equity in providing UPGS services and equity in supply and demand matching. This study extrapolates from micro to macro analysis using network big data and census data to pinpoint the population down to the building level in the main urban area of Fuzhou City, China. The network analysis method, improved Gaussian floating catchment area method, Gini coefficient, and Lorenz curve measurement help to evaluate UPGS service euquity, explore the similarities and differences of UPGS fairness under different travel modes. It also helps to understand the service relationship between UPGS service and population demand under objective space, and to pinpoint the weak supply area using the locational entropy method. The results show that: (1) The overall accessibility and per capita accessibility show similar spatial distribution patterns under different travel modes, which are "high around and low in the middle" and "centered on the Minjiang River and dispersed to the north and south, respectively" in study area. (2) The supply of UPGS services in Fuzhou is relatively adequate and at a relatively equity level, while varies in the allocation of UPGS services among sub-districts. The spatial equity of different traveling modes varies widely. (3) The sub-districts on the periphery of the study area should be subject to increased UPGS and improvements to the road network and public infrastructure. Sub-district with high population density and old neighborhoods should implement micro-renewal and build community parks. Our study presents a new idea for spatial equity research.
Organolead trihalide perovskites have attracted great attention due to the stunning advances in both photovoltaic and light-emitting devices. However, the photophysical properties, especially the ...recombination dynamics of photogenerated carriers, of this class of materials are controversial. Here we report that under an excitation level close to the working regime of solar cells, the recombination of photogenerated carriers in solution-processed methylammonium-lead-halide films is dominated by excitons weakly localized in band tail states. This scenario is evidenced by experiments of spectral-dependent luminescence decay, excitation density-dependent luminescence and frequency-dependent terahertz photoconductivity. The exciton localization effect is found to be general for several solution-processed hybrid perovskite films prepared by different methods. Our results provide insights into the charge transport and recombination mechanism in perovskite films and help to unravel their potential for high-performance optoelectronic devices.
Abstract
Chlorine atoms (Cl) are highly reactive and can strongly influence the abundances of climate and air quality-relevant trace gases. Despite extensive research on molecular chlorine (Cl
2
), a ...Cl precursor, in the polar atmosphere, its sources in other regions are still poorly understood. Here we report the daytime Cl
2
concentrations of up to 1 ppbv observed in a coastal area of Hong Kong, revealing a large daytime source of Cl
2
(2.7 pptv s
−1
at noon). Field and laboratory experiments indicate that photodissociation of particulate nitrate by sunlight under acidic conditions (pH < 3.0) can activate chloride and account for the observed daytime Cl
2
production. The high Cl
2
concentrations significantly increased atmospheric oxidation. Given the ubiquitous existence of chloride, nitrate, and acidic aerosols, we propose that nitrate photolysis is a significant daytime chlorine source globally. This so far unaccounted for source of chlorine can have substantial impacts on atmospheric chemistry.
A new kind of self-dispersing silica nanoparticle was prepared and used to enhance oil recovery in spontaneous imbibition tests of low-permeability cores. To avoid the aggregation of silica ...nanoparticles, a new kind of silica nanoparticle was prepared through the surface modification with vinyltriethoxysilane and 2-mercaptobenzimidazole as modified agents. Transmission electron microscopy, Fourier transform infrared spectroscopy, dynamic light scattering, and ζ potential measurements were employed to characterize the modified silica nanoparticles. Dispersing experiments indicated that modified silica nanoparticles had superior dispersity and stability in alkaline water. To evaluate the performance of silica nanofluids for enhanced oil recovery compared to pH 10 alkaline water and 5 wt % NaCl solution, spontaneous imbibition tests in sandstone cores were conducted. The results indicated that silica nanofluids can evidently improve oil recovery. To investigate the mechanism of nanoparticles for enhanced oil recovery, the contact angle and interfacial tension were measured. The results showed that the adsorption of silica nanoparticles can change the surface wettability from oil-wet to water-wet and silica nanoparticles showed a little influence on oil/water interfacial tension. In addition, the change of the oil droplet shape on the hydrophobic surface was monitored through dynamic contact angle measurement. It was shown that silica nanoparticles can gradually detach the oil droplet from the hydrophobic surface, which is consistent with the structural disjoining pressure mechanism.
With steel fiber and basalt fiber volume dosing serving as variation parameters, a total of 200 d cycles of acid rain corrosion cycle tests were conducted on fiber concrete in this study. We selected ...three durability evaluation parameters to assess the degree of damage deterioration on fiber concrete, used scanning electron microscopy, mercury intrusion porosimetry, and a dimensional microhardness meter to analyze the concrete micromorphology, and established a GM(1,1)-Markov model for life prediction of its durability. Results reveal that the acid rain environment is the most sensitive to the influence of the relative dynamic elastic modulus evaluation parameter, and concrete has specimens that show failure damage under this parameter evaluation. Incorporation of fibers can reduce the amount of corrosion products inside the concrete, decrease the proportion of harmful pores, optimize the mean pore-size, and significantly improve the resistance to acid rain attack. Concrete with 2% steel fiber and 0.1% basalt fiber by volume has the least change in durability damage, and the predicted service life by GM(1,1)-Markov model is 322 d.
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