pH-responsive size-adjustable liposomes induce apoptosis of fibroblasts and macrophages for rheumatoid arthritis treatment.

In rheumatoid arthritis (RA), macrophages infiltrate joints, while fibroblast-like synovial cells proliferate abnormally, forming a barrier against drug delivery, which hinders effective drug delivery to joint focus. Here we firstly designed a pH-responsive size-adjustable nanoparticle, composed by methotrexate (MTX)-human serum albumin (HSA) complex coating with pH-responsive liposome (Lipo/MTX-HSA) for delivering drugs specifically to inflamed joints in acidic environments. We showed in vitro that the nanoparticles can induce mitochondrial dysfunction, promote apoptosis of fibroblast-like synoviocytes and macrophages, further reduce the secretion of inflammatory factors (TNF-α, IL-1ß, MMP-9), and regulate the inflammatory microenvironment. We also demonstrated similar effects in a rat model of arthritis, in which Lipo/MTX-HSA accumulated in arthritic joints, and at low pH, liposome phospholipid bilayer cleavage released small-sized MTX-HSA, which effectively reduced the number of fibroblast-synoviocytes and macrophages in joints, alleviated joint inflammation, and repaired bone erosion. These findings suggest that microenvironment-responsive size-adjustable nanoparticles show promise as a treatment against rheumatoid arthritis. STATEMENT OF SIGNIFICANCE: Abnormal proliferation of fibroblast synoviocytes poses a physical barrier to effective nanoparticle delivery. We designed size-adjustable nano-delivery systems by preparing liposomes with cholesterol hemisuccinate (CHEM), which were subsequently loaded with small-sized albumin nanoparticles encapsulating the cytotoxic drug MTX (MTX-HSA), termed Lipo/MTX-HSA. Upon tail vein injection, Lipo/MTX-HSA could be aggregated at the site of inflammation via the ELVIS effect in the inflamed joint microenvironment. Specifically, intracellular acidic pH-triggered dissociation of liposomes promoted the release of MTX-HSA, which was further targeted to fibroblasts or across fibroblasts to macrophages to exert anti-inflammatory effects. The results showed that liposomes with adjustable particle size achieved efficient drug delivery, penetration and retention in joint sites; the strategy exerted significant anti-inflammatory effects in the treatment of rheumatoid arthritis by inducing mitochondrial dysfunction to promote apoptosis in fibrosynoviocytes and macrophages.

Thyrotropin induces atherosclerosis by upregulating large conductance Ca2+-activated K+ channel subunits.

Hypothyroidism is associated with elevated levels of serum thyrotropin (TSH), which have been shown to promote abnormal proliferation of vascular smooth muscle cells and contribute to the development of atherosclerosis. However, the specific mechanisms underlying the TSH-induced abnormal proliferation of vascular smooth muscle cells remain unclear. The objective of this study was to investigate the role of TSH in the progression of atherosclerosis. Our research findings revealed that hypothyroidism can trigger early atherosclerotic changes in the aorta of Wistar rats. In alignment with our in vitro experiments, we observed that TSH induces abnormal proliferation of aortic smooth muscle cells by modulating the expression of α and ß1 subunits of large conductance Ca2+-activated K+ (BKCa) channels within these cells via the cAMP/PKA signaling pathway. These results collectively indicate that TSH acts through the cAMP/PKA signaling pathway to upregulate the expression of α and ß1 subunits of BKCa channels, thereby promoting abnormal proliferation of arterial smooth muscle cells. These findings may provide a basis for the clinical prevention and treatment of atherosclerosis caused by elevated TSH levels.

Significant Increase in Ammonia Emissions in China: Considering Nonagricultural Sectors Based on Isotopic Source Apportionment.

Isotopic source apportionment results revealed that nonagricultural sectors are significant sources of ammonia (NH3) emissions, particularly in urban areas. Unfortunately, nonagricultural sources have been substantially underrepresented in the current anthropogenic NH3 emission inventories (EIs). Here, we propose a novel approach to develop a gridded EI of nonagricultural NH3 in China for 2016 using a combination of isotopic source apportionment results and the emission ratios of carbon monoxide (CO) and NH3. We estimated that isotope-corrected nonagricultural NH3 emissions were 4370 Gg in China in 2016, accounting for an increase in the total NH3 emissions from 7 to 31%. As a result, compared to the original NH3 EI, the annual emissions of total NH3 increased by 35%. Thus, in comparison to the simulation driven by the original NH3 EI, the WRF-Chem model driven by the isotope-corrected NH3 EI has reduced the model biases in the surface concentrations and dry deposition flux of reduced nitrogen (NHx = gaseous NH3 + particulate NH4+) by 23 and 31%, respectively. This study may have wide-ranging implications for formulating targeted strategies for nonagricultural NH3 emissions controls, making it facilitate the achievement of simultaneously alleviating nitrogen deposition and atmospheric pollution in the future.

Contamination and health risks brought by arsenic, lead and cadmium in a water-soil-plant system nearby a non-ferrous metal mining area.

Heavy metal(loid)s contamination prevails in the water-soil-plant system around non-ferrous metal mining areas. The present study aimed to evaluate the heavy metal(loid)s contamination in Nandan Pb-Zn mining area (Guangxi, China). A total of 36 river water samples, 75 paired paddy soil and rice samples, and 128 paired upland soil and plant samples were collected from this area. The concentrations of arsenic (As), lead (Pb), and cadmium (Cd) in these samples were measured. Results showed that the average water quality indexes (WQIs) at the 12 sampling sites along the main river ranged from 41 to 5008, indicating the water qualities decreasing from "Excellent" to "Undrinkable". The WQIs nearby tailings or industrial park were significantly higher than those at the other sites. 34.0% and 64.5% of soil samples exceeded the risk screening values for As and Cd. The Pb and Cd concentrations in all rice samples exceeded the Chinese food safety limits by 18.7% and 82.7%, respectively. Leafy vegetables had a higher concentration of As, Pb, and Cd than other vegetables, exceeding the maximum permissible limits by 14.1%, 61.2%, and 40.0%, respectively. The biological accumulation coefficient (BAC) of Cd was the highest in rice and lettuce leaves. The hazard quotients (HQs) of As and Cd, indicating non-carcinogenic risks, were 4.15 and 1.76 in adult males, and 3.40 and 1.45 in adult females, all higher than the permitted level (1.0). The carcinogenic probabilities of As and Cd from rice and leafy vegetables consumption were all higher than 1 × 10-4. We conclude that metal(loid)s contamination of the water-soil-plant system has posed great non-carcinogenic and carcinogenic risks to the local population.

Size-distribution and driving factors of aerosol oxidative potential in rural kitchen microenvironments of northeastern India.

This study reports size-resolved dithiothreitol (DTT)-based oxidative potential (OP: total and water-soluble) in rural kitchens using liquefied petroleum gas (LPG), firewood (FW), and mixed biomass (MB) fuels in northeastern (NE) India. In comparison to LPG, volume-normalized total OP (OPtotal(v)DTT) was enhanced by a factor of ∼5 in biomass-using kitchens (74 ± 35 to 78 ± 42 nmol min-1 m-3); however, mass-normalized total OP (OPtotal(m)DTT) was similar between LPG and FW users and higher by a factor of 2 in MB-using kitchens. The water-insoluble OP (OPwi(v, m)DTT) fraction in OPtotal(v, m)DTT was greater than 50% across kitchens. Size distributions across kitchens and OPDTT categories ranged from unimodal to trimodal. OPws(v)DTT was driven by metals as well as organics across size fractions while OPwi(v)DTT was majorly constrained by metals with an increasing importance of organics in fine particles of biomass-using kitchens. Multiple linear regression analysis revealed that Cu and Ba explained 71% of the OPtotal(v)DTT variability in LPG-using kitchens, while water-soluble organic carbon (WSOC) and Ba were responsible for 44% variability in FW-using kitchens. Finally, the high internal dose of OPtotal(v)DTT (28-31 nmol min-1 m-3) in biomass-using kitchens established the severity of oxidative stress on the exposed population.

Different stimuli induce endothelial dysfunction and promote atherosclerosis through the Piezo1/YAP signaling axis.

Vascular endothelial dysfunction is the initial step in atherosclerosis (AS). AS tends to occur at vascular bifurcations and curves, and endothelial cells(ECs) are highly susceptible to injury due to mechanical forces induced by disturbed flow (DF) with inconsistent blood flow directions. However, the pathogenesis of endothelial cell dysfunction in AS remains unclear and needs further study. Here, we found that Piezo1 expression was significantly increased in DF- and oxidized low-density lipoprotein(ox-LDL)-treated HUVECs in vitro and a model of atherosclerotic plaque growth in ApoE-/- mice fed a Western diet. Furthermore, Piezo1 upregulated autophagy levels in the HUVECs model, which was reversed by Piezo1 knockdown with a lentivirus-mediated shRNA system. Mechanistically, the level of Yes-associated protein (YAP), a transcriptional coactivator in the Hippo pathway, was significantly elevated in the DF- and ox-LDL-induced HUVECs model, and this effect was further inhibited by Piezo1 knockdown. Moreover, the Piezo1 agonist Yoda1 inhibited the protein level of microtubule-associated protein 1 light chain 3-II(LC3-II) and increased the protein level of sequestosome1(p62/SQSTM1) in a dose-dependent manner, while significantly promoting the protein expression and nuclear translocation of YAP. The YAP inhibitor CA3 weakened Yoda1-mediated inhibition of autophagy. Our results suggest that Piezo1 may regulate endothelial autophagy by promoting YAP activation and nuclear translocation, thereby contributing to vascular endothelial dysfunction.

Advances in treatment strategies based on scavenging reactive oxygen species of nanoparticles for atherosclerosis.

The development of atherosclerosis (AS) is closely linked to changes in the plaque microenvironment, which consists primarily of the cells that form plaque and the associated factors they secrete. The onset of inflammation, lipid deposition, and various pathological changes in cellular metabolism that accompany the plaque microenvironment will promote the development of AS. Numerous studies have shown that oxidative stress is an important condition that promotes AS. The accumulation of reactive oxygen species (ROS) is oxidative stress's most important pathological change. In turn, the effects of ROS on the plaque microenvironment are complex and varied, and these effects are ultimately reflected in the promotion or inhibition of AS. This article reviews the effects of ROS on the microenvironment of atherosclerotic plaques and their impact on disease progression over the past five years and focuses on the progress of treatment strategies based on scavenging ROS of nanoparticles for AS. Finally, we also discuss the prospects and challenges of AS treatment.

Contribution of marine biological emissions to gaseous methylamines in the atmosphere: An emission inventory based on multi-source data sets.

Methylamines are a class of highly reactive organic alkaline gases in the atmosphere. At present, the gridded emission inventories of amines used in the atmospheric numerical model is mostly based on the amine/ammonia ratio method and do not consider the air-sea exchange of methylamines, which oversimplifies the emission scenario. Marine biological emissions (MBE), an important source of methylamines, has been insufficiently investigated. These shortcomings in the inventories can limit the simulation of amines by numerical models in the context of compound pollution in China. To acquire a more complete gridded inventory of amines (monomethylamine (MMA), dimethylamines (DMA), and trimethylamines (TMA)), we established a more reasonable MBE inventory of amines by using multi-source data sets (Sea Surface Temperature (SST), Chlorophyll-a (Chla), Sea Surface Salinity (SSS), NH3 column concentration (NH3), and Wind Speed (WS)), and merged it with the anthropogenic emissions (AE) inventory (by adopting the amine/ammonia ratio method and the Multi-resolution Emission Inventory for China (MEIC)). The new methodology can reveal the air-sea exchange fluxes and direction of different amines. Oceans can act as a sink for DMA and source for TMA while it can be either a source or sink for MMA. The concentration of amines above the coastal area increased significantly when the MBE was merged to the AE inventory. TMA and MMA showed significant increases, TMA increased by 43,917.0 %, and 804.0 %, in July 2015 and December 2019, respectively; while MMA increased by 2635.4 % and 0.37 % during the same periods; however, only slight changes were observed in the DMA concentration (-3.9 % in July 2015, and 1.1 % in December 2019). WS, Chla, and the total dissolved concentration of amines ([C+(s)tot]) were found to be the dominant factors affecting MBE fluxes. In addition, the emission fluxes and spatial distribution of AE, and wet deposition also affect the simulation of amines concentration.

Optical source apportionment of aqueous brown carbon (BrC) on a daytime and nighttime basis in the eastern Indo-Gangetic Plain (IGP) and insights from 13C and 15N isotopic signatures.

This study reports day-night and seasonal variations of aqueous brown carbon (BrCaq) and constituent humic-like substances (HULIS) (neutral and acidic HULIS: HULIS-n and HULIS-a) from the eastern Indo-Gangetic Plain (IGP) of India during 2019-2020. This is followed by the application of the receptor model positive matrix factorization (PMF) for optical source apportionment of BrCaq and the use of stable isotopic ratios (δ13C and δ15N) to understand atmospheric processing. Nighttime BrCaq absorption and mass absorption efficiencies (MAE) were enhanced by 40-150 % and 50-190 %, respectively, compared to the daytime across seasons, possibly as a combined effect from daytime photobleaching, dark-phase secondary formation, and increased nighttime emissions. MAE250 nm/MAE365 nm (i.e., E2/E3) ratios and Angstrom Exponents revealed that BrCaq and HULIS-n were relatively more aromatic and conjugated during the biomass burning-dominated periods while BrCaq and HULIS-a were comprised mostly of non-conjugated aliphatic structures from secondary processes during the photochemistry-dominated summer. The relative radiative forcing of BrCaq with respect to elemental carbon (EC) was 10-12 % in the post-monsoon and winter in the 300-400 nm range. Optical source apportionment using PMF revealed that BrCaq absorption at 300, 365 and 420 nm wavelengths in the eastern IGP is mostly from biomass burning (60-75 %), followed by combined marine and fossil fuel-derived sources (24-31 %), and secondary processes (up to 10 %). Source-specific MAEs at 365 nm were estimated to be the highest for the combined marine and fossil fuel source (1.34 m2 g-1) followed by biomass burning (0.78 m2 g-1) and secondary processing (0.13 m2 g-1). Finally, δ13C and δ15N isotopic analysis confirmed the importance of summertime photochemistry and wintertime NO3--dominated chemistry in constraining BrC characteristics. Overall, the quantitative apportionment of BrCaq sources and processing reported here can be expected to lead to targeted source-specific measurements and a better understanding of BrC climate forcing in the future.

[Characterization of Ambient Volatile Organic Compounds, Source Apportionment, and the Ozone-NOx-VOC Sensitivities in Liucheng County, Guangxi].

Liucheng county, as a suburb of Liuzhou City in Guangxi province, has a prominent ozone (O3) pollution problem; however, there have been no relevant analyses of the cause of local O3 pollution reported. In order to investigate the causes of O3 pollution, an online observation of 116 VOCs with a time resolution of 1 h was carried out in Liucheng county from October 1st to 15th, and the sensitivity of ozone to the relative changes in the NOx and VOCs was analyzed. The results showed that the average value of φï¼»total volatile organic compounds (TVOCs)ï¼½ during the observation period was 27.52×10-9, and the average value of φ(TVOCs) during the polluting process (October 1st to 6th) was 32.15×10-9, which was 32.79% higher than that of the non-pollution process (October 8th to 15th). In terms of species concentration, oxygenated volatile organic compounds (OVOCs) contributed the highest, accounting for 43.70%, followed by alkanes (23.00%), aromatics (11.75%), and halocarbons (7.35%). In terms of ozone formation potential (OFP), OVOCs contributed the highest (41.96%) to OFP, followed by aromatics (32.60%) and alkenes (17.92%). During the observation period, VOCs mainly came from motor vehicle emissions (32.44%), biomass combustion sources (29.31%), solvent use sources (16.43%), plant sources (11.34%), and chemical industry emissions (10.49%). The contribution ratios of solvent use sources and plant sources in the pollution process increased by 28.58% and 28.53%, respectively. The EKMA curve shows that, during the observation period, Liucheng county was in a synergistic control area for VOCs and nitric oxide (NOx). Therefore, in the high ozone-occurrence autumn of Liucheng county, the key will be to reduce both VOCs and NOx emissions.

Seasonal variations in aerosol acidity and its driving factors in the eastern Indo-Gangetic Plain: A quantitative analysis.

This study employs ISORROPIA-II for the evaluation of aerosol acidity and quantification of contributions from chemical species and meteorological parameters to acidity variation in the Indian context. PM2.5 samples collected during summer (April-July 2018), post-monsoon (September-November 2018), and winter (December 2018-January 2019) from a rural receptor location in the eastern Indo-Gangetic Plain (IGP) were analyzed for ionic species, water-soluble organic carbon (WSOC), and organic and elemental carbon (OC, EC) fractions. This was followed by estimation of the in situ aerosol pH and liquid water content (LWC) using the forward mode of ISORROPIA-II, which is less sensitive to measurement uncertainty compared to the reverse mode, for a K+-Ca2+-Mg2+-NH4+-Na+-SO42--NO3--Cl--H2O system. Aerosol pH was moderately acidic (summer: 2.93 ± 0.67; post-monsoon: 2.67 ± 0.23; winter: 3.15 ± 0.34) and was most sensitive to SO42- and total ammonium (TNH3) variation. The LWC of aerosol showed an increasing trend from summer (16.6 ± 13.6 µg m-3) through winter (32.9 ± 10.4 µg m-3). With summer as the baseline, the largest changes in aerosol pH during the other seasons was driven by SO42- (ΔpH: -0.70 to -0.82 units), followed by TNH3 (ΔpH: +0.25 to +0.38 units) with K+ and temperature being significant only during winter (ΔpH: +0.51 and + 0.46 units, respectively). The prevalent acidity regime provided three major insights: i) positive summertime Cl- depletion (49 ± 20%) as a consequence of SO42- substitution increased aerosol pH by 0.03 ± 0.20 units and decreased LWC by 2.4 ± 5.9 µg m-3; ii) the rate of strong acidity (H+str) neutralization and the [H+str]/[SO42-] molar ratio suggested the existence of bounded acidity in ammonium-rich (winter) conditions; and iii) significant correlations between LWC, WSOC, and secondary organics during post-monsoon and winter pointed towards a possible indirect role of WSOC in enhancing LWC of aerosol, thereby increasing pH. Given the inability of proxies such as H+str and charge ratios to accurately represent aerosol pH as demonstrated here, this study emphasizes the need for rigorous thermodynamic model-based evaluation of aerosol acidity in the Indian scenario.

Assessment of background ozone concentrations in China and implications for using region-specific volatile organic compounds emission abatement to mitigate air pollution.

Mitigation of ambient ozone (O3) pollution is a great challenge because it depends heavily on the background O3 which has been poorly evaluated in many regions, including in China. By establishing the relationship between O3 and air temperature near the surface, the mean background O3 mixing ratios in the clean and polluted seasons were determined to be 35-40 and 50-55 ppbv in China during 2013-2019, respectively. Simulations using the chemical transport model (i.e., the Weather Research and Forecasting coupled with Chemistry model, WRF/Chem) suggested that biogenic volatile organic compounds (VOC) emissions were the primary contributor to the increase in the background O3 in the polluted season (BOP) compared to the background O3 in the clean season (BOC), ranging from 8 ppbv to 16 ppbv. More importantly, the BOP continuously increased at a rate of 0.6-8.0 ppbv yr-1 during 2013-2019, while the non-BOP stopped increasing after 2017. Consequently, an additional 2%-16% reduction in anthropogenic VOC emissions is required to reverse the current O3 back to that measured in the period from 2013 to 2017. The results of this study emphasize the importance of the relative contribution of the background O3 to the observed total O3 concentration in the design of anthropogenic precursor emission control strategies for the attainment of O3 standards.

Are fireworks a significant episodic source of brown carbon?

We hypothesize that firework events involving the combustion of charcoal fuel, organic binders, metal salts, and cellulose-based wrapping material could be significant transient sources of aerosol brown carbon (BrC). To test this, we couple high time-resolution (1 min) measurements of black carbon (BC) and BrC absorption from a 7-wavelength aethalometer with time-integrated (12-24 h) measurements of filter extracts, i.e., UV-visible, fluorescence, and Fourier-transformed infrared (FT-IR) signatures of BrC, total and water-soluble organic carbon (OC and WSOC), ionic species, and firework tracer metals during a sampling campaign covering the Diwali fireworks episode in India. In sharp contrast to BC, BrC absorption shows a distinct and considerable rise of 2-4 times during the Diwali period, especially during the hours of peak firework activity, as compared to the background. Fluorescence profiles suggest enrichment of humic-like substances (HULIS) in the firework plume, while the enhancement of BrC absorption in the 400-500 nm range suggests the presence of nitroaromatic compounds (NACs). Considerable contributions of WSOC and secondary organics to OC (44.1% and 31.2%, respectively) and of the water-soluble fraction of BrC to total BrC absorption (71.0%) during the Diwali period point toward an atmospherically processed, polar signature of firework-related BrC, which is further confirmed by FT-IR profiles. This aqueous BrC exerts a short-lived but strong effect on atmospheric forcing (12.0% vis-à-vis BC in the UV spectrum), which could affect tropospheric chemistry via UV attenuation and lead to a stabilization of the post-Diwali atmosphere, resulting in enhanced pollutant build-up and exposure.

Significant contribution of lightning NOx to summertime surface O3 on the Tibetan Plateau.

Lightning generates nitrogen oxides (NOx) in the troposphere, an important precursor of tropospheric ozone (O3). The Tibetan Plateau (TP) is considered to be a global atmospheric background location with limited anthropogenic influences. However, the observed summertime surface O3 concentration on the TP is 25% higher than that in highly polluted regions (e.g., southern China). Previous studies have suggested that lightning-produced NOx (LNOx) can affect the concentration of surface O3. We used the Weather Research and Forecasting coupled with chemistry (WRF-Chem) model combined with satellite, ground-based, and airborne observations to evaluate the contribution of LNOx to the surface O3 budget on the TP. Our results showed that LNOx contributed approximately 15% of the surface NOx emission on the TP in summer. Accordingly, the contribution of LNOx to the summertime surface daily maximum 8-h average (MDA8) O3 on the TP was 9.3 ± 7.1 ppb, which was 17.5% ± 14.5% of the total concentration of the surface MDA8 O3. In addition, our study found that the number of moles of NO produced per lightning flash (LNOx production efficiency) significantly affected the surface concentration of NOx, OH, and MDA8 O3. Increasing the LNOx production efficiency (PE) from 0 to 330 mol NO flash-1 increased the concentration of MDA8 O3 by up to 20% on the TP. Our study revealed that lightning significantly affects the atmospheric chemical processes involving O3 on the TP.

Synergistic effects of biogenic volatile organic compounds and soil nitric oxide emissions on summertime ozone formation in China.

Natural emissions play a key role in modulating the formation of ground-level ozone (O3), especially emissions of biogenic volatile organic compounds (BVOCs) and soil nitric oxide (SNO), and their individual effects on O3 formation have been previously quantified and evaluated. However, their synergistic effects remain unclear and have not yet been well assessed. By applying the Weather Research and Forecasting (WRF) model coupled with the Chemistry-Model of Emissions of Gases and Aerosols from Nature (WRF/Chem-MEGAN) model, this study reveals that in the presence of sufficient BVOC emissions, which act as a fuel, SNO emissions act as a fuel additive and promote the chemical reactions of BVOCs and the subsequent production of O3. Consequently, the synergistic effects of BVOC and SNO emissions on summertime O3 production surpassed the sum of their individual effects by as much as 10-20 µg m-3 in eastern China in 2014. In order to reduce O3 concentration to a level corresponding to no natural emissions of BVOC or SNO (i.e., the BASE scenario), the anthropogenic volatile organic compound (AVOC) emissions in the scenario considers BVOC and SNO emissions must be reduced by 1.76 times that of the BASE scenario. This study demonstrates that the synergistic effects of BVOC and SNO emissions can impede ground-level O3 regulation and can subsequently impose stricter requirements on anthropogenic precursor emission control in China. The results of this study can also inform efforts in other regions that are still combating ground-level O3 pollution.

[Nonlinear Response Relationship Between Ozone and Precursor Emissions in the Pearl River Delta Region Under Different Transmission Channels].

With the rapid development of urbanization, ozone (O3) pollution is an ongoing occurrence in the Pearl River Delta (PRD) region in China. The effective control of O3 pollution is a great challenge owing to the nonlinear relationship between O3 and precursor emissions and the effect of meteorological conditions. Based on the regional air quality model CAMx-OSAT (ozone source apportionment technology), O3 formation regimes were determined, and inter-city transportation across PRD was quantified under different transmission channels. The results showed that spatial differences were observed for the O3 formation regimes under different transmission channels. The VOCs-sensitive regime was mainly located in the central areas of the PRD region, and the NOx-sensitive regime was distributed in the suburban areas of the PRD regions under calm wind conditions. When the northeast wind was prevailing, the polluted air mass of the urban agglomeration was transmitted southwesterly downward, resulting in the downwind areas being transformed to VOCs-sensitive; the upwind areas were still NOx-sensitive. Under the southeast wind, the VOCs-sensitive regime had a banding distribution along the southeast-northwest direction, and the remaining areas were NOx-sensitive. With the influence of transmission channels, downwind cities were significantly affected by the transmission of upwind urban agglomerations (41%-87%), whereas the local formation was the main contributor under the calm wind conditions (60%-87%). To explore the relationship between O3 and precursor emissions, a series of sensitivity tests were designed. The results showed that maximized areas (20%-36%) with reductions in O3 can be achieved by reducing VOCs and NOx in the corresponding sensitive regimes, and the maximized level with the reduction in O3 can be fulfilled by reducing VOCs in the VOCs-sensitive regime. For the typical city Jiangmen, the area that met the standard increased the most under the calm wind (11%) and southeast wind (8%) conditions when VOCs and NOx were reduced in the corresponding sensitive regimes. Additionally, under northeast wind conditions, reducing VOCs in the VOCs-sensitive regime can more effectively control O3, as the area up to the standard increased by 140%.

A New Index Developed for Fast Diagnosis of Meteorological Roles in Ground-Level Ozone Variations.

China experienced worsening ground-level ozone (O3) pollution from 2013 to 2019. In this study, meteorological parameters, including surface temperature (T 2 ), solar radiation (SW), and wind speed (WS), were classified into two aspects, (1) Photochemical Reaction Condition (PRC = T 2 × SW) and (2) Physical Dispersion Capacity (PDC = WS). In this way, a Meteorology Synthetic Index (MSI = PRC/PDC) was developed for the quantification of meteorology-induced ground-level O3 pollution. The positive linear relationship between the 90th percentile of MDA8 (maximum daily 8-h average) O3 concentration and MSI determined that the contribution of meteorological changes to ground-level O-3 varied on a latitudinal gradient, decreasing from ∼40% in southern China to 10%-20% in northern China. Favorable photochemical reaction conditions were more important for ground-level O3 pollution. This study proposes a universally applicable index for fast diagnosis of meteorological roles in ground-level O3 variability, which enables the assessment of the observed effects of precursor emissions reductions that can be used for designing future control policies. ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available in the online version of this article at 10.1007/s00376-021-1257-x.

Ozone control strategies for local formation- and regional transport-dominant scenarios in a manufacturing city in southern China.

Given the leveling off of fine particulate matter (PM2.5), ground-level ozone (O3) pollution has become one of the most significant atmospheric pollution issues in the Pearl River Delta (PRD) region in China, especially in the manufacturing city of Dongguan, which faces more severe O3 pollution. The development of strategies to control O3 precursor emissions, including volatile organic compounds (VOCs) and nitrogen oxide (NOx), depends to a large extent on the source region of the O3 pollution. In this study, by combining the Weather Research and Forecasting model coupled with chemistry (WRF-Chem), the Empirical Kinetic Modeling Approach (EKMA), and the Flexible Particle model (FLEXPART), more effective strategies of controlling O3 precursor emissions were identified under two typical types of O3 pollution episodes: local formation (LF)-dominant (8-12 September 2019) and regional transport (RT)-dominant (23-27 October 2017) episodes, distinguished by the WRF-FLEXPART model. During the LF-dominant episode, the EKMA revealed that the O3 formation in Dongguan was in a transitional regime, and the abatement of solvent use-VOCs emissions in the key area of Dongguan was more effective in reducing O3 levels, with an emission reduction benefit 1.7 times that of total VOCs emission sources throughout Dongguan. With respect to the RT-dominant episode, the reduction in VOCs emissions in the local region did not effectively curb O3 pollution, although the photochemical regime of the O3 formation in Dongguan was VOCs-limited. A 50% reduction in NOx emissions in the upwind regions (parts of Guangzhou and Huizhou) effectively decreased the O3 concentration in Dongguan by 17%. The results of this study emphasize the importance of the source region of O3 pollution in the implementation of effective O3 control strategies and provide valuable insights for region-specific precursor emission policy formulation, not only in Dongguan, but also in other regions facing severe O3 pollution.

Deposition of ambient particles in the human respiratory system based on single particle analysis: A case study in the Pearl River Delta, China.

It is important to evaluate how ambient particles are deposited in the human respiratory system in view of the adverse effects they pose to human health. Traditional methods of investigating human exposure to ambient particles suffer from drawbacks related either to the lack of chemical information from particle number-based measurements or to the poor time resolution of mass-based measurements. To address these issues, in this study, human exposure to ambient particulate matter was investigated using single particle analysis, which provided chemical information with a high time resolution. Based on single particle measurements conducted in the Pearl River Delta, China, nine particle types were identified, and EC (elemental carbon) particles were determined to be the most dominant type of particle. In general, the submicron size mode was dominant in terms of the number concentration for all of the particle types, except for Na-rich and dust particles. On average, around 34% of particles were deposited in the human respiratory system with 13.9%, 7.9%, and 12.6% being distributed in the head, tracheobronchial, and pulmonary regions, respectively. The amount of Na-rich particles deposited was the highest, followed by EC. The overall deposition efficiencies of the Na-rich and dust particles were higher than those of the other particle types due to their higher efficiencies in the head region, which could be caused by the greater sedimentation and impaction rates of larger particles. In the head region, the Na-rich particles made the largest contribution (30.5%) due to their high deposition efficiency, whereas in the tracheobronchial and pulmonary regions, EC made the largest contribution due to its high concentration. In summary, the findings of this initial trial demonstrate the applicability of single particle analysis to the assessment of human exposure to ambient particles and its potential to support traditional methods of analysis.