To improve the power of reference wavefront generated by reference wavefront source (RWS) based on silicon nitride (SiN) waveguide in point diffraction interferometer (PDI), we design the Y-branch ...coupler and grating coupler, and then compare the maximum coupling efficiency, 3 dB fabrication tolerance, 3 dB alignment tolerance and polarization dependent loss of two couplers. Our results show that grating coupler has higher coupling efficiency, lower etching difficulty and alignment difficulty, while Y-branch coupler has lower coating difficulty. To get the maximum efficiency, mode in the fiber must be TE mode no matter for grating coupler or Y-branch coupler. This paper improves the power of the wavefront by selecting appropriate fiber-to-waveguide couplers for waveguide RWS. PDI based on the power improved waveguide RWS is expected to be used in many measurement fields.
Traditionally, optical vortices (OVs) were generated with diffractive optical elements (DOEs) such as spiral phase plate (SPP), fork grating, spatial light modulator (SLM), and liquid crystal display ...(LCD). Here, a method was proposed for generating OVs by employing all-dielectric polarization-insensitive metasurfaces with cylinder arrays, which have high transmission efficiency. The polarization insensitivity of the metasurfaces was illustrated with the incidence of two pairs of orthogonal polarization, both the phase and transmission efficiency were consistent for the cylinder unit cell, and similar OVs were generated with the cylinder array. The topological charges of the generated OVs can be adjusted through the design of the metasurfaces. OVs with additional characteristics as vector beams, focused beams and Bessel beams were further generated. This work has potential applications in beam shaping, optical tweezers, and optical communication.
•Source-specific risks of synchronous PAHs and heavy metals at different PM levels were studied.•Industrial source caused high health risks (81% of HQ and 49% of R) even during ‘clean’ days.•Relative ...impacts of industrial source to risks declined by about 25% during haze.•Relative impacts of diesel and gasoline vehicles to R, and crustal dust to HQ increased during haze.
Synchronous heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) in inhalable particulate matter (PM10) were measured during 2009–2012 and 2015–2016 in a Chinese megacity (Chengdu) to understand the variations in source-specific health risks during haze episodes. Samples were divided into four mass concentration levels: PM10 ≤ 150 μg m−3 (L1), 150 μg m−3 < PM10 ≤ 250 μg m−3 (L2), 250 μg m−3 < PM10 ≤ 350 μg m−3 (L3), and PM10 > 350 μg m−3 (L4). The percentages of some HMs and PAHs (accounting for PM10) decreased from L1 to L4, indicating that they exhibited lower growth rates than other species during heavy pollution. The combined cancer risk (R) for HMs and PAHs was higher at L1 and L4, and the combined non-cancer risk (HQ) was significantly high at L4. The HMs and PAHs combined source-specific risk apportion (HP-SRA) model was employed to quantify the source-specific risks. The relative contributions of (i) diesel and gasoline vehicles to the R, and (ii) crustal dust to the HQ increased during heavy pollution (L3 and L4). The relative contribution of industrial source declined from 81% (L1) to 60% (L4) for the HQ, and from 49% (L1) to 36% (L4) for the R, implying that the control of industrial emissions during heavy pollution events could alleviate risk growth as a co-benefit of controlling PM mass concentration. However, the risks associated with industrial emissions should also be considered during ‘clean’ days.
Inhalation bioaccessibility and deposition in respiratory tracts of organic components in atmospheric particulate matter (PM) are key factors for accurately estimating health risks and understanding ...human exposures. This study evaluated the in-vitro inhalation bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) and PAH derivatives, phthalic acid esters (PAEs), polychlorinated biphenyls (PCBs), and organophosphate flame retardants (OPFRs) in size-resolved PM from a Chinese megacity. The bioaccessibility ranged from 0.2% to 77.8% in the heating period (HP), and from 0.7% to 94.2% in the non-heating period (NHP). Result suggests that less hydrophobic organics might be more bioaccessible. Bioaccessibility of medium logKow organics in sizes > 0.65 µm was significantly inhibited by high carbon fractions, indicating the co-effects. Then, this is the first study to explore effects of sources on inhalation bioaccessibility of organics. Coal and biomass combustion in HP and traffic emission in NHP negatively correlated with bioaccessibility. Secondary particles also negatively correlated with bioaccessibility of medium logKow organics. Incremental lifetime cancer risk (ILCR) and non-cancer risk (HQ) for all measured components in PM10 were estimated after considering the bioaccessibility and deposition efficiencies and the HQ and ILCR were within the acceptable range. BaP and DEHP were strong contributors to HQ and ILCR, respectively.
Display omitted
•Inhalation bioaccessibility of PM-bound multiple organics was measured.•The bioaccessibility of organics was higher in the non-heating period.•The bioaccessibility of hydrophilic organics was higher than hydrophobic organics.•High EC proportions of particles will reduce the bioaccessibility of organics.•Coal combustion and traffic emission negatively correlated with the bioaccessibility.
Gas/particle (G/P) partitioning is a determining factor that drives the behavior of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere. To comprehend the variations and impacts of PAHs G/P ...partitioning on inhalation risks from different sources, atmospheric PAHs in Chengdu were studied from January 2009 to January 2021. Chengdu's air quality demonstrated improvement, with a noticeable decline in PM10 (from 238 to 103 μg m−3), PM10-bound PAHs mass concentrations (from 0.08 to 0.01 μg m−3), as well as PAHs inhalation non-cancer (from 63.5 to 7.1) and cancer risks (from 6.2 × 10−5 to 7.7 × 10−6). Decreasing trends were also observed in the concentrations of organic carbon (OC) and the values of absorptive G/P partitioning coefficient (Kp, OM) from 2009 to 2020, indicating a slight decrease in the PM absorptive capacity. A positive matrix factorization (PMF) model utilized three distinct datasets: PMFpp (particle-phase PAHs only), PMFtot (total PAHs concentrations), and PMFpp/gas (particle-phase in parallel with gas-phase PAHs). PMFpp and PMFpp/gas provide reasonable source apportionment and source-specific risk results. However, daily variations in source contributions of PMFtot were found to be unreasonable. PMFpp/gas and PMFtot could identify a source of low molecular weight PAHs (LPAHs) related to temperature, and a significantly positive correlation between LPAHs and temperature was discovered. Gas/particle partitioning of PAHs showed a notable impact on source-specific risks associated with coal and biomass combustion (CC&BC). The findings contribute to our understanding of the variation in PAHs G/P partitioning and the PM absorptive capacity resulting from effective air pollution control in China. Additionally, they offer prerequisite information for incorporating semi-volatile organic compounds in source apportionment and source-specific risk assessment.
Display omitted
•A slight decrease of the PM absorptive capacity was observed from 2009 to 2020.•Including the gaseous PAHs in PMF can resolve the temperature-related source.•G/P partitioning had a great effect on specific risk of coal&biomass combustion.•Cancer and non-cancer risks of PAHs in PM10 showed a downward trend.•Traffic emissions played a dominant role in both cancer and non-cancer risks.
Toxic metals (TMs) and polycyclic aromatic hydrocarbons (PAHs) in size-segregated particles during common days (CD) and different heavy pollution (HP) episodes were measured during 2018–2021 in a ...Chinese megacity. The Multiple Path Particle Dosimetry Model (MPPD) was performed to estimate deposition efficiency, and then inhalation risks in the human pulmonary region during different types of HP were assessed and compared. The higher pulmonary deposition efficiency of PAHs and TMs during all types of HP than those during CD was confirmed. The accumulative incremental lifetime cancer risk (ILCR) of different HP were 2.42 × 10−5, 1.52 × 10−5, 1.39 × 10−5, 1.30 × 10−5 and 2.94 × 10−6 for HP4 (combustion sources HP), HP1 (ammonium nitrate HP), HP5 (mixed sources HP), HP3 (resuspended dust HP) and HP2 (ammonium sulfate HP), respectively. The accumulative hazard quotient (HQ) during different HP episodes decreased in the order of HP4 (0.32) > HP3 (0.24) > HP1 (0.22) > HP5 (0.18) > HP2 (0.05). The inhalation risks were dominated by Ni and Cr, what's more, the HQ of Ni and ILCR of Cr during the five HP episodes shared a similar size distribution pattern. However, the characteristic components during different HP episodes and their size distributions of them were distinctive. The size distribution of inhalation risks of the related components (Ni, Cr, BaP, and As) from the combustion process during HP4 peaked at fine mode (0.65–2.1 μm). The size distribution of inhalation risks of the dust-related components (Mn and V) and the components (As and BaP) that are likely to volatilize and re-distribution peaked at coarse mode (2.1–3.3 μm) during HP3. Notably, Mn and Co as catalysts at fine mode could increase the degree of secondary formation and toxicity.
Display omitted
•Size-segregated toxic metals and PAHs were measured in an industrial megacity.•Inhalation risks were assessed based on deposition concentrations.•HP characterized by combustion sources posed highest inhalation risks.•HP characterized by ammonium nitrate and resuspended dust posed moderate risks.•Mn and Co may have increased the degree of secondary formation and toxicity.
An oil/water separation mesh with high separation efficiency and intrusion pressure of water has been successfully developed by combining mussel-inspired chemistry and Michael addition reaction. The ...substrate of the stainless steel mesh was first coated with the adhesive polydopamine (PDA) film by simple immersion in an aqueous solution of dopamine at pH of 8.5. Then n-dodecyl mercaptan (NDM) was conjugated with PDA film through Michael addition reaction at ambient temperature. The as-prepared mesh showed highly hydrophobicity with the water contact angle of 144° and superoleophilicity with the oil contact angle of 0°. It can be used to separate a series of oil/water mixtures like gasoline, diesel, etc. The separation efficiency remains high after 30 times use (99.95% for hexane/water mixture). More importantly, the relatively high intrusion pressure (2.2 kPa) gives the opportunity to separation of large amount of oil and water mixtures. This study provides a new prospect to simply introduce multiple molecules on the adhesive PDA-based mesh to achieve various functional oil/water separation materials.
Display omitted
•Emission factors of multiple PM-bound PTCs from residential combustion was measured.•Most PAHs and derivatives of residential combustion originate from chemical reaction.•Absorption ...mechanism is the dominant mechanism for gas/particle partitioning of PTCs.•The health risks caused by potential toxic elements in clean coal cannot be ignored.•BaPeq of PM1-bound PTCs accounted for 82.91% of that of PM2.5 on average.
Particulate matter (PM) from residential combustion is an existential threat to human health. Emission factors (EFs) of multiple potential toxic components (PTCs) in size-resolved PM and gas from eight residential fuel combustion were measured, and size distribution, gas/particle partitioning and health risks of the PTCs were investigated. Average EFs from clean coal and anthracite coal were PTEs (sum of EFs of 11 Potential Toxic Elements, 6.62 mg/kg fuels) > PAHs (sum of 22 Polycyclic Aromatic Hydrocarbons, 1.12 mg/kg) > OPAHs (sum of 5 Oxygenated Polycyclic Aromatic Hydrocarbons, 0.45 mg/kg) > PAEs (sum of 6 Phthalate Esters, 0.11 mg/kg) > NPAHs (sum of 14 Nitropolycyclic Aromatic Hydrocarbons, 16.84 μg/kg) > OPEs (sum of 7 Organophosphate Esters, 7.57 μg/kg) > PCBs (sum of 6 Polychorinated Biphenyls, 0.07 μg/kg), which were 2–3 and 1–2 orders of magnitude lower than the EFs of PTCs (except PTEs) from bituminous coal and biomass. Most PAHs, OPAHs and NPAHs, which may mainly originate from chemical reactions, showed similar size distributions and averagely 85 % concentrated in PM1. PTEs, PAEs, OPEs and PCBs generated from the release from raw fuels may have a higher proportion, so their size distributions were more complex and varied with combustion temperature, volatility of compounds, binding mode of the raw fuels, and so on. In addition, clean coal and high-quality anthracite coal could reduce the health risks from the potential organic toxic components, but also reveal the stumbling block of PTEs in risk control.
PM2.5-bound heavy metals were measured in a Chinese megacity (Tianjin) in 2013, 2016 and 2019, and analyzed by a new RSDA method (source directional apportionment of risks). Through combining the ...receptor model, cluster analysis of back trajectories, and risk assessment, the RSDA was developed in this work to quantify source-specific risks from each direction. Concentrations of PM2.5 and most species (especially for heavy metals) underwent various reductions, and the incremental lifetime cancer risk (ILCR) and non-cancer risk (HQ) declined by more than 80% from 2013 to 2019. Pb was the highest contributor to the reduction of HMs mass concentration (58.6%), while Cr (85.5% for cancer risk) and As (26.0% for non-cancer risk) were more prominent for the reduction of HM risks. The coal combustion and industrial emissions were vital contributors to the reduction of both PM2.5 mass concentrations (contributed 34.0% and 7.8% to the reduction respectively) and health risks (contributed 36.1% and 25.7% to the cancer risk reduction respectively). Although the percentage mass contribution of traffic emissions increased (7.7% in 2013 and 21.9% in 2019), the associated risks decreased (contributed 26.8% to the cancer risk reduction). Furthermore, the results of RSDA consistently implied that coal combustion, industrial emissions and traffic emissions controls in the northeast/north-northeast, south and southwest of the studied area played important roles in the risk reductions, which mainly due to the risk reduction of air masses from NE/NNE, S and SW, and their strong influence to Tianjin. The RSDA method can quantify the health risks from different sources and directions, and the evaluation of contributors to the reductions of risks in this work would provide a meaningful reference for policy maker to control PM2.5 emissions and protect population health.
•An advanced method, source directional apportionment of health risks was developed.•Decrease of heavy metals risks was mainly due to the decrease of Cr and As.•Coal combustion from the south was main contributor to health risks reduction.
To understand rapid physicochemical changes and to explore how to better conduct PMF for source apportionment during haze episodes, EPA Positive Matrix Factorization (PMF) 5.0, including an ...assessment of uncertainties, was performed based on hourly measurements of PM2.5-bound species during a heating period in 2017–2018 in the Chinese megacity of Tianjin. Five haze episodes were the focus of this study. PMF was conducted using two modes (whole-based mode for the entire sampling period and episode-based mode for each episode), and some indicators, including bootstrap (BS), displacement of factor elements (DISP), E/M (ratios of estimated and measured concentrations), were then used to evaluate PMF performance. The contributions of secondary ions and secondary organic carbon (SOC) for episodes I and III were greater than 50% (which were defined as SPE: episodes strongly influenced by secondary particles). The coal combustion contribution in episode II (defined as coal combustion episode: CCE) was greater than in the other episodes, and fireworks burning were extracted in episode IV (defined as fireworks burning episode: FBE). The PMF solutions were poor for the regional transport episode (RTE), during which episode the species showed weak variations (low coefficients of variation) and similar patterns (high correlations). During SPE, E/M were 0.71–1.00 for episode-based mode and 0.65–1.28 for whole-based mode, indicating good performance for both modes; while during CCE and FBE, E/M were 0.53–0.99 for episode-based mode and 0.10–1.06 for whole-based mode, showing that estimation of some important markers were poor for the whole-based mode. Sensitivity tests were then conducted to systematically investigate the influence of heavy-pollution types on PMF and showed that PMF was insensitive to contribution variations but was strongly sensitive to variations in source profiles. Overall, episode-based mode of PMF is better for episodes with strong variations of primary sources (CCE and FBE), whereas whole-based mode can be used for SPE and RTE. This work will help us to accurately assess hourly source variations.
•Rapid changes of PM2.5 compositions and cycles during 5 haze episodes were pictured.•Episode-based mode of PMF is advised when source compositions change for a long time.•Whole-based mode of PMF is advised for secondary source and transport caused episodes.
PDF
