Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 182
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
J Environ Sci (China) ; 92: 187-199, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32430122

RESUMO

An intensive and persistent regional ozone pollution event occurred over eastern China from 25 June to 5 July 2017. 73 out of 96 selected cities, most located in the Beijing-Tianjin-Hebei and the surrounding area (BTHS), suffered severe ozone pollution. A north-south contrast ozone distribution, with higher ozone (199 ± 33 µg/m3) in the BTHS and lower ozone (118 ± 25 µg/m3) in the Yangtze River Delta (YRD), was found to be dominated by the position of the West Pacific Subtropical High (WPSH) and mid-high latitude wave activities. In the BTHS, the positive anomalies of geopotential height at 500 hPa and temperature at the surface indicated favorable meteorological conditions for local ozone formation. Prevailing northwesterly winds in the mid-high troposphere and warm advection induced by weak southerly winds in the low troposphere resulted in low-moderate relative humidity (RH), less total cloud cover (TCC), strong solar radiation and high temperatures. Moreover, southerly winds prevailing over the BTHS aggravated the pollution due to regional transportation of O3 and its precursors. On one hand, the deep sinking motion and inversion layer suppressed the dispersion of pollutants. On the other hand, O3-rich air in the upper layer was maintained at night due to temperature inversion, which facilitated O3 vertical transport to the surface in the next-day morning due to elevated convection. Generally, temperature, UV radiation, and RH showed good correlations with O3 in the BTHS, with rates of 8.51 (µg/m3)/°C (within the temperature range of 20-38°C), 59.54 (µg/m3)/(MJ/m2) and -1.93 (µg/m3)/%, respectively.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32382903

RESUMO

The aerosol samples of water-soluble inorganic ions (WSIs), including SO42-, NO3-, NH4+, Cl-, K+, Na+, Ca2+, and Mg2+ in size-segregated particulate matter (PM), were collected by an Anderson sampler (with 8 nominal cut-sizes ranged from 0.43 to 9.0 µm) in urban Tianjin during 2013-2014. The results showed that particulate matters in the fine mode (PM2.1, Dp < 2.1 µm) comprised large part of mass concentrations of aerosols, and the water-soluble ionic species in the fine mode were 47.07 ± 14.29 µg m-3 (spring), 67.87 ± 28.74 µg m-3 (summer), 86.60 ± 48.53 µg m-3 (autumn), and 104.16 ± 51.76 µg m-3 (winter), respectively, which accounted for 59.5%, 63.3%, 71.9%, and 71.4% of the PM2.1 mass concentrations. Secondary pollutants of SO42-, NO3-, and NH4+ (SNA) were the dominant contributors of WSIs, which showed a bimodal size distribution in each season, with the larger peak appeared in the size fraction of 0.65-1.1 µm and the smaller one in 3.3-5.8 µm fraction. SNA concentrations in lightly polluted days (LPD) and heavily polluted days (HPD) were observably higher than non-polluted days (NPD), especially in the fine mode, with the peak diameter moving from 0.43-0.65 µm on NPD to 0.65-1.1 µm on LPD and HPD. The correlation analysis between NH4+, NO3-, and SO42- suggested that almost all SO42- and NO3- for fine particles had been completely neutralized by NH4+, and primarily existed in the forms of (NH4)2SO4 and NH4NO3. The sulfur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR) on LPD and HPD in fine mode were observably higher than those on NPD, especially in the range of 0.65-1.1 µm and 1.1-2.1 µm. Furthermore, SOR and NOR values in the size fraction of 0.43-3.3 µm increase as the RH elevated, especially in 0.43-2.1 µm, where RH was significantly positive correlated with SOR and NOR, indicating the significant contributions of heterogeneous processes to the secondary formation of SO42- and NO3-. These results suggested an enhanced formation ability of secondary pollutants under high RH in the coast city. Therefore, controlling the precursors of SNA, such as SO2 and NOx, would be more effective to reduce the fine particulate pollution in the coast megacity of Tianjin.

3.
Sci Total Environ ; 720: 137617, 2020 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-32325589

RESUMO

The measurement of volatile organic compounds (VOCs) was carried out using an online GC-FID/MS at a rural site in North China Plain from 1 Nov. 2017 to 21 Jan. 2018. Their concentrations, emission ratios and source apportionment are investigated. During the entire experiment period, the average mixing ratio of VOCs was 69.5 ± 51.9 ppb, among which alkanes contributed the most (37% on average). Eight sources were identified in the non-negative matrix factorization (NMF) model as short-chain alkanes (13.3%), biomass burning (4.6%), solvent (10.8%), industry (3.7%), coal combustion (41.1%), background (4.5%), vehicular emission (7.7%) and secondary formation (14.2%). In addition to the formation of OVOCs through photochemical reactions, the primary sources, such as coal combustion, biomass burning, vehicular emission, solvent and industry, can also contribute to OVOCs emissions. High OVOCs emission ratios thus were observed at Wangdu site. Primary emission was estimated to contribute 50%, 45%, 73%, 77%, 40%, and 29% on average to acrolein, acetone, methylvinylketone (MVK), methylethylketone (MEK), methacrolein and n-hexanal according to NMF analysis, respectively, which was well consistent with the contribution from photochemical age method. Secondary organic aerosol formation potential (SOAFP) was evaluated by SOA yield, which was significantly higher under low-NOx condition (13.4 µg m-3 ppm-1) than that under high-NOx condition (3.2 µg m-3 ppm-1). Moreover, the photochemical reactivity and sources of VOCs showed differences in seven observed pollution episodes. Among, the largest OH loss rate and SOAFP were found in severe pollution plumes, which were induced primarily by coal combustion. Therefore, mitigation strategies for severe pollution formation should focus on reducing coal combustion emitted VOCs that lead to SOA formation.

4.
Proc Natl Acad Sci U S A ; 117(8): 3960-3966, 2020 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-32041887

RESUMO

Although regional haze adversely affects human health and possibly counteracts global warming from increasing levels of greenhouse gases, the formation and radiative forcing of regional haze on climate remain uncertain. By combining field measurements, laboratory experiments, and model simulations, we show a remarkable role of black carbon (BC) particles in driving the formation and trend of regional haze. Our analysis of long-term measurements in China indicates declined frequency of heavy haze events along with significantly reduced SO2, but negligibly alleviated haze severity. Also, no improving trend exists for moderate haze events. Our complementary laboratory experiments demonstrate that SO2 oxidation is efficiently catalyzed on BC particles in the presence of NO2 and NH3, even at low SO2 and intermediate relative humidity levels. Inclusion of the BC reaction accounts for about 90-100% and 30-50% of the sulfate production during moderate and heavy haze events, respectively. Calculations using a radiative transfer model and accounting for the sulfate formation on BC yield an invariant radiative forcing of nearly zero W m-2 on the top of the atmosphere throughout haze development, indicating small net climatic cooling/warming but large surface cooling, atmospheric heating, and air stagnation. This BC catalytic chemistry facilitates haze development and explains the observed trends of regional haze in China. Our results imply that reduction of SO2 alone is insufficient in mitigating haze occurrence and highlight the necessity of accurate representation of the BC chemical and radiative properties in predicting the formation and assessing the impacts of regional haze.

5.
Sci Total Environ ; 710: 136304, 2020 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-31927286

RESUMO

Crop residue burning in China increased significantly in the last decade, especially it took up a majority in Northeast China, which plays an important role of severe haze pollution. Hence, two main types of crop residues (corn and rice straw) were chosen to characterize the particle number concentration, chemical components of fine particulate matter and optical properties of carbonaceous aerosols by a suite of fast-response online portable instruments, together with offline sampling and analysis, during the field-based combustion experiments in Northeast China. For the range of 250 and 2500 nm, more particles were emitted from rice straw burning than those from corn straw burning, and the time-averaged number concentration of particles during the flaming process was approximately 2 times higher than that during the smoldering process for these two straws. Organic carbon (OC), elemental carbon (EC) and water-soluble ions were the most abundant components and accounted for 42.5 ± 7.5%, 7.7 ± 1.7% and 18.0 ± 3.4% of the PM2.5, respectively. Furthermore, rice straw burning emitted higher OC and lower Cl- and K+ than those from corn straw burning. The average absorption Ångström exponent (AAE) of carbonaceous aerosols was 2.1 ± 0.3, while the AAE of brown carbon (BrC) was 4.7 ± 0.4 during the whole burning process. On average, BrC contributed to 63% and 20% of the total light absorption at 375 nm and 625 nm, respectively. Parameterization of BrC absorption revealed that the fraction of absorption from BrC has a reasonably good correlation with EC/OC (-0.84) and AAE (0.94) at 375 nm. Generally, combustion conditions can affect the optical properties of carbonaceous aerosols, and a negative correlation (-0.77) was observed between the AAE and modified combustion efficiency; in addition, the percentage of absorption due to BrC were lower at the flaming phase.

6.
J Environ Sci (China) ; 89: 136-144, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31892386

RESUMO

Qualitative and quantitative analyses of derivatized phenols in Beijing and in Xinglong were performed from 2016 to 2017 using gas chromatography-mass spectrometry. The results showed substantially more severe pollution in Beijing. Of the 14 compounds detected, the total average concentration was 100 ng/m3 in Beijing, compared with 11.6 ng/m3 in Xinglong. More specifically, concentration of nitro-aromatic compounds (NACs) (81.9 ng/m3 in Beijing and 8.49 ng/m3 in Xinglong) was the highest, followed by aromatic acids (14.6 ng/m3 in Beijing and 2.42 ng/m3 in Xinglong) and aromatic aldehydes (3.62 ng/m3 in Beijing and 0.681 ng/m3 in Xinglong). In terms of seasonal variation, the highest concentrations were found for 4-nitrocatechol in winter in Beijing (79.1 ± 63.9 ng/m3) and 4-nitrophenol in winter in Xinglong (9.72 ± 8.94 ng/m3). The analysis also revealed diurnal variations across different seasons. Most compounds presented higher concentrations at night in winter because of the decreased boundary layer height and increased heating intensity. While some presented higher levels during the day, which attributed to the photo-oxidation process for summer and more biomass burning activities for autumn. Higher concentrations appeared in winter and autumn than in spring and summer, which resulted from more coal combustions and adverse meteorological conditions. The significant correlations among NACs indicated similar sources of pollution. Higher correlations presented within each subgroup than those between the subgroups. Good correlations between levoglucosan and nitrophenols, nitrocatechols, nitrosalicylic acids, with correlation coefficients (r) of 0.66, 0.69 and 0.69, respectively, indicating an important role of biomass burning among primary sources.


Assuntos
Poluentes Atmosféricos , Monitoramento Ambiental , Material Particulado , Fenóis/análise , Pequim , China , Estações do Ano
7.
Sci Total Environ ; 705: 135803, 2020 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-31972941

RESUMO

To investigate the regional transport and formation mechanisms of submicron aerosols in the North China Plan (NCP), for the first time, we conducted simultaneous combined observations of the non-refractory submicron aerosols (NR-PM1) chemical compositions using aerosol mass spectrometer at urban Beijing (BJ) and at regional background area of the NCP (XL), from November 2018 to January 2019. During the observation period, average mass concentrations of PM1 in BJ and XL were 26.6 ± 31.7 and 16.0 ± 18.7 µg m-3 respectively. The aerosol composition in XL showed a lower contribution of organic aerosol (33% vs. 43%) and higher fractions of nitrate (35% vs. 30%), ammonium (16% vs. 13%), and chlorine (2% vs. 1%) than in BJ. Additionally, a higher contribution of secondary organic aerosol (SOA) was also observed in XL, suggesting low primary emissions and highly oxidized OA in the background area. Nitrate displayed a significantly enhanced contribution with the aggravation of aerosol pollution in both BJ and XL, which was completely neutralized by excess ammonium at both sites, suggesting that the abundant ammonia emissions in the NCP favor nitrate formation on a regional scale. In addition, a higher proportion of nitrate in XL can be attributed to the more neutral and higher oxidation capacity of the background atmosphere. Heterogeneous aqueous reaction plays an important role in sulfate and SOA formation, and is more efficient in BJ which can be attributed to the higher aerosol surface areas at urban site. Regional transport from the southwestern regions of NCP showed a significant impact on the formation of haze episodes. Beside the invasion of transported pollutants, the abundant water vapor associated with the air mass to the downwind background area further enhanced local secondary transformation and expanded the regional scope of the haze pollution in the NCP.

8.
Environ Int ; 134: 105283, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31743806

RESUMO

In the last decade, North China (NC) has been one of the most populated and polluted regions in the world. The regional air pollution has had a serious impact on people's health; thus, all levels of government have implemented various pollution prevention measures since 2013. Based on multi-city in situ environmental and meteorological data, as well as the meteorological reanalysis dataset from 2013 to 2017, regional pollution characteristics and meteorological formation mechanisms were analyzed to provide a more comprehensive understanding of the evolution of PM2.5 in NC. The domain-averaged PM2.5 was 79 ±â€¯17 µg m-3 from 2013 to 2017, with a decreasing rate of 10 µg m-3 yr-1. Two automatic computer algorithms were established to identify 6 daily regional pollution types (DRPTs) and 48 persistent regional pollution events (PRPEs) over NC during 2014-2017. The average PM2.5 concentration for the Large-Region-Pollution type (including the Large-Moderate-Region-Pollution and Large-Severe-Region-Pollution types) was 113 ±â€¯40 µg m-3, and more than half of Large-Region-Pollution days and PRPEs occurred in winter. The PRPEs in NC mainly developed from the area south of Hebei. The number of Large-Region-Pollution days decreased notably from 2014 to 2017, the annual number of days varying between 194 and 97 days, whereas a slight decline was observed in winter. In addition, the averaged PM2.5 concentrations and the numbers and durations of the PRPEs decreased. Lamb-Jenkinson weather typing was used to reveal the impact of synoptic circulations on PM2.5 across NC. Generally, the contributions of the variations in circulation to the reduction in PM2.5 levels over NC between 2013 and 2017 were 64% and 45% in summer and winter, respectively. The three most highly polluted weather types were types C, S and E, with an average PM2.5 concentration of 137 ±â€¯40 µg m-3 in winter. Furthermore, three typical circulation dynamics were categorized in the peak stage of the PRPEs, namely, the southerly airflow pattern, the northerly airflow pattern and anticyclone pattern; the averaged relative humidity, recirculation index, wind speed and boundary layer height were 63%, 0.33, 2.0 m s-1 and 493 m, respectively. Our results imply that additional emission reduction measures should be implemented under unfavorable meteorological situations to attain ambient air quality standards in the future.

9.
Huan Jing Ke Xue ; 41(1): 82-89, 2020 Jan 08.
Artigo em Chinês | MEDLINE | ID: mdl-31854907

RESUMO

We study the seasonal variations of δ13C ratios in aerosol fine particulate matter (PM2.5) using 91 PM2.5 samples collected from Xinxiang, China, during the summer and winter in 2017. Mass concentrations of total carbon (TC), water soluble ions, and stable carbon isotope ratios (δ13C) were determined. The mean concentrations of TC in the summer and winter were 11.78 µg·m-3 and 26.6 µg·m-3, respectively. The δ13C ratio in the summer ranged from -27.70‰ to -25.22‰. The daily δ13C ratio fluctuated in the first half of the summer months (mean -26.96‰), whereas the δ13C ratio in the second half of the summer was relatively stable (mean -25.69‰). The number of fires in the study area during the first half of the summer was quite different to the number during the second half of the summer, meanwhile, there was a positive correlation between the Knss+ concentration and the TC mass concentration (R2=0.62, P<0.01). This indicates that biomass burning most likely contributed to variations in δ13C. During the winter there was a significant negative correlation between winter RH and the TC/PM2.5 mass ratio (R2=0.68, P<0.01), which suggests that SOA growth was dominant in the early stage of haze development, whereas the pollution period was dominated by SIA components. The ratio of δ13C ranged from -26.72‰ to -23.49‰, and there was a difference between the variation of the δ13C ratio in haze episode (when it was mainly enriched in the development stage) to that in the stage dominated by depletion.

10.
Huan Jing Ke Xue ; 40(6): 2493-2500, 2019 Jun 08.
Artigo em Chinês | MEDLINE | ID: mdl-31854638

RESUMO

To characterize the dry and wet deposition of atmospheric trace elements in urban Beijing, both active and passive samplers were used to collect bulk and wet sedimentation samples between May 2014 and April 2015.The concentrations of 19 trace elements (Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Cu, Zn, As, Se, Mo, Cd, Sb, Tl, Th, and U) in the samples were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The results show that the concentrations of metals in bulk deposition samples[7160.68 µg·L-1 (Ca)-0.02 µg·L-1 (Th)] were generally higher than those in wet deposition samples[4237.74 µg·L-1 (Ca)-0.01 µg·L-1 (Th)], but the enrichment factors of each metal in the two kinds of samples were less different. Of note, the enrichment factors of Cu, As, Tl, Zn, Cd, Se, and Sb were all larger than 100, thus indicating that these heavy metals were mainly from anthropogenic sources. The statistical analysis of the air mass trajectory shows that the precipitation chemistry in urban Beijing is mainly affected by southward air flows. The air mass originating from the southwest region always had higher concentrations of Ca, Mg, Fe, Al, Cu, Mo, U, and Th, whereas the air mass from the south had higher concentrations of K, Zn, Mn, Sb, Cd, and Tl. During the observation period, the bulk deposition fluxes of metals varied from 3591.35 mg·(m2·a)-1 (Ca)-0.01 mg·(m2·a)-1 (Th), and wet deposition fluxes varied from 1847.78 mg·(m2·a)-1 (Ca)-0.01 mg·(m2·a)-1 (Th). The dry deposition fluxes of the 19 metals varied from 1743.57 mg·(m2·a)-1 (Ca)-0.01 mg·(m2·a)-1 (Th). The particle size has important implications in the evaluation of the relative importance of dry deposition versus wet deposition during the scavenging of trace elements in air.

11.
Proc Natl Acad Sci U S A ; 116(49): 24463-24469, 2019 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-31740599

RESUMO

From 2013 to 2017, with the implementation of the toughest-ever clean air policy in China, significant declines in fine particle (PM2.5) concentrations occurred nationwide. Here we estimate the drivers of the improved PM2.5 air quality and the associated health benefits in China from 2013 to 2017 based on a measure-specific integrated evaluation approach, which combines a bottom-up emission inventory, a chemical transport model, and epidemiological exposure-response functions. The estimated national population-weighted annual mean PM2.5 concentrations decreased from 61.8 (95%CI: 53.3-70.0) to 42.0 µg/m3 (95% CI: 35.7-48.6) in 5 y, with dominant contributions from anthropogenic emission abatements. Although interannual meteorological variations could significantly alter PM2.5 concentrations, the corresponding effects on the 5-y trends were relatively small. The measure-by-measure evaluation indicated that strengthening industrial emission standards (power plants and emission-intensive industrial sectors), upgrades on industrial boilers, phasing out outdated industrial capacities, and promoting clean fuels in the residential sector were major effective measures in reducing PM2.5 pollution and health burdens. These measures were estimated to contribute to 6.6- (95% CI: 5.9-7.1), 4.4- (95% CI: 3.8-4.9), 2.8- (95% CI: 2.5-3.0), and 2.2- (95% CI: 2.0-2.5) µg/m3 declines in the national PM2.5 concentration in 2017, respectively, and further reduced PM2.5-attributable excess deaths by 0.37 million (95% CI: 0.35-0.39), or 92% of the total avoided deaths. Our study confirms the effectiveness of China's recent clean air actions, and the measure-by-measure evaluation provides insights into future clean air policy making in China and in other developing and polluting countries.

12.
Sci Total Environ ; 695: 133889, 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31426000

RESUMO

Volatile organic compounds (VOCs) have vital implications for secondary pollutants, atmospheric oxidation and human health. Ambient VOCs were investigated using an online system, gas chromatography-mass spectrometry/flame ionization detector (GC-MS/FID), at a suburban site in Xianghe in the North China Plain from 6 November 2017 to 29 January 2018. Positive matrix factorization (PMF) receptor model was applied to identify the major VOC contributing sources. Four-step health risk assessment method was used to estimate risks of all risk-posing VOC species. A total of 101 VOCs were quantified, and the mean concentration of total VOCs was 61.04 ±â€¯65.18 ppbv. The VOCs were dominated by alkanes (38.76%), followed by alkenes, aromatics, halocarbons, OVOCs, acetylene and acetonitrile. The results of PMF revealed that vehicle exhaust, industrial emissions, liquefied petroleum gas & natural gas, solvent utilization and secondary and long-lived species contributed 31.0%, 26.4%, 18.6%, 13.6% and 10.4%, respectively, to the total VOCs. Pollutant-specific and source-specific noncarcinogenic and carcinogenic risk estimates were conducted, which showed that acrolein and vehicle exhaust had evident noncarcinogenic risks of 4.9 and 0.9, respectively. The carcinogenic risks of specific species (1,3-butadiene, acetaldehyde, benzene, chloroform and 1,2-dichloroethane) and identified sources were above the United States Environmental Protection Agency (USEPA) acceptable level (1.0 × 10-6) but below the tolerable risk level (1.0 × 10-4). Vehicle exhaust was the largest contributor (56.2%) to noncarcinogenic risk, but solvent utilization (32.6%) to carcinogenic risk. Moreover, with the evolution of pollution levels, almost all VOC species, contributions of alkenes, aromatics, solvent utilization and vehicle exhaust, and pollutant-specific and source-specific risks increased continuously and noticeably. Collectively, our findings unraveled the importance of alkenes, aromatics, solvent utilization and vehicle exhaust in the evolution of pollution levels. Future studies should consider targeting these VOC groups and sources when focusing on effective reduction strategies and assessing public health risks.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Compostos Orgânicos Voláteis/análise , Poluição do Ar/estatística & dados numéricos , China , Humanos , Exposição por Inalação/estatística & dados numéricos , Medição de Risco
13.
Sci Total Environ ; 687: 1073-1086, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31412445

RESUMO

Fine particle explosive growth (FPEG) events are frequently observed in heavy haze episodes in Beijing, the characteristics and formation mechanism of which remain not fully understood. In this study, a five year (2013-2017) online observation was conducted in Beijing and the chemical evolution pattern of FPEG events was analyzed to understand its formation mechanism. A total of 132 FPEG events were identified, and steadily decreased from 39 events in 2013 to 19 events in 2017. More than 70% of the FPEG events occurred in winter and autumn, which coincides with adverse weather conditions and enhanced primary emissions. Organic matter (OM) was the dominated components (~30%) in PM2.5, but it only accounted for 10% of total FPEG events as a driven factor, because its contribution usually decreased when the FPEG events developed. In contrast, the secondary inorganic species were the dominated driven factors, and sulfate-driven events accounted >50%. During the period of 2013-2017, the contribution from regional sources decreased significantly mainly due to the reduction of emissions from regional sources, while the contribution from local sources remained largely unchanged, indicating that the local secondary transformation played a leading role in promoting the FPEG events. The low nitrogen oxidation rates (NOR, 0.12 ±â€¯0.07) and the weak increase trend of NOR with elevated RH were observed, indicating the formation of which might be promoted by the homogenous reaction between HNO3 and NH3. In contrast, a significant increase in sulfur oxidation rate (SOR, 0.50 ±â€¯0.19) was observed when RH > 50%, suggesting enhanced heterogeneous oxidation of SO2 in FPEG events. In addition, our analysis suggest the S (IV) heterogeneous oxidation rates in FPEG events depend mainly on the aerosol liquid water content (ALWC) in addition to the aerosol acidity. This study provides observational evidence for understanding the formation mechanism of FPEG events in Beijing.

14.
Sci Total Environ ; 692: 371-381, 2019 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-31351281

RESUMO

Based on the high-resolution observation of meteorological factors profiles, particulate matter concentration and aerosol radiative forcing (ARF) from 25 August to 17 November 2018 in Beijing, the feedback between ARF and the atmospheric boundary layer (ABL) stability was systematically investigated during air pollution episodes. There was the initial explosive growth in particulate matter (PM) concentration that PM2.5 sharply increased from ~8µgm-3 to ~100µgm-3, with aerosol optical depth (AOD) increasing from ~0.25 to ~0.58. This was the transport phase dominated by the southerly winds. As PM increased, the high aerosol loading scattered more solar radiation cooling the earth-atmosphere system (ARF at the top of the atmospheric column (TOA): from ~5Wm-2 to ~-52Wm-2). Meanwhile, high aerosol loading absorbed more solar radiation and heated the atmospheric layer with ARF at the interior of the atmospheric column (ATM) increasing from ~21Wm-2 to ~42Wm-2. The absorption and scattering effects of aerosol together cooled the surface (ARF at the surface of the atmospheric column (SFC): from ~-16Wm-2 to ~-90Wm-2). Thus, the ABL stability rapidly increased in the following cumulative phase and heavy pollution phase with a strong temperature inversion (inversion depth of ~300-1000m) occurring. In turn, the persistent temperature inversion caused the significant accumulation of moisture (water vapor density of ~5-10gm-3) and pollutants, and PM were prone to physicochemical reactions in the high-humidity environment, further increasing PM. It was the constant feedback effect between ARF and the ABL stability that continually reduced atmospheric environmental capacity and aggravated air pollution (PM2.5 and AOD reaching ~95-125µgm-3 and ~1.38-1.75, respectively). Finally, the feedback was broken by dry, clean and strong north winds appearing in Beijing in the dissipation phase.

15.
Sci Total Environ ; 692: 402-410, 2019 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-31351284

RESUMO

The Beijing-Tianjin-Hebei (BTH) region, which has the most severe air pollution in China, built a 10,000 km2 coal banning zone for pollution control in 2017. In this study, to evaluate the impact of banning coal zone on visibility (VIS), a chemical composition analysis, a chemical mass closure and the revised IMPROVE algorithm were applied to estimate the chemical components and lighting extinction coefficients (bext) of the fine particulate matter (PM2.5) collected at three urban sites (Beijing (BJ), Tianjin (TJ) and Shijiazhuang (SJZ)) and a regional background site (Xinglong (XL)) during autumn and winter of 2016-2017. Compared to measurements from 2016, the average PM2.5 from 2017 decreased by 44 µg m-3 (BJ), 37 µg m-3 (TJ), 69 µg m-3 (SJZ) and 10 µg m-3 (XL), respectively, accompanied by an improved VIS (3.2-4.6 km). The degradation of VIS caused by atmospheric aerosol is due to the light extinction. The bext clearly decreased by 58%, 51%, 56% and 54% at BJ, TJ, SJZ and XL, respectively. However, the reductions/improvements were more significant in winter than those in autumn, especially at BJ and TJ located in the coal banning zone. The decline (improvement) in PM2.5 (VIS) was 16%-37% (15%-27%) in autumn but 29%-60% (21%-83%) in winter. The reductions in SO42- (Cl-) in winter were 2.8 (3.2) and 7.4 (16.4) times larger than those in autumn at BJ and TJ, respectively. Reductions in ammonium sulfate, one of the main species of PM2.5 caused by coal burning, were particularly pronounced at three urban sites in winter (59%-68%). In addition, the reductions in bext in winter were 2.3 (BJ), 339.4 (TJ), 1.9 (SJZ) and 0.4 (XL) times larger than those in autumn. The results reveal that banning coal zone has a marked effect on controlling pollution in the BTH, especially in winter (scattering aerosol sulfate).

16.
Sci Total Environ ; 685: 116-123, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31174111

RESUMO

Polycyclic aromatic hydrocarbons (PAHs) associated with size-segregated particulate matter at 10 sampling sites over China which can be grouped into North China and South China, including urban site, sub-urban site, farmland site and background site, from January 2013 to December 2014 were analyzed by Gas Chromatography - Mass Spectrometry. This is the first time for comprehensive studies on the size-segregated PAHs at the national level. The spatial variations of particulate PAHs showed that Xinaghe (XH), Yucheng (YC) and Shenyang (SHY) in North China had higher particulate PAHs mass concentrations than other sampling sites. The seasonal variations of PAHs exhibited the highest mass concentrations in winter, which could be caused by the increase in emission, lower temperatures and weaker solar radiation. Particulate PAHs were found to be dominant in fine size range of <1.1 µm, the same as individual PAH compounds. The dominant species in particulate PAHs are benzo[b + k]fluoranthene (BBKF), indeno[1,2,3-cd]pyrene (IP) and benzo[g,h,i]perylene (BghiP), indicating that fossil fuel combustion could be an important source for PAHs over China. BaP, a carcinogen to humans, also had much higher mass concentrations at XH, SHY and YC in North China than other sites. Toxicity equivalent quantities (TEQ) and the lifetime excess cancer risk (ECR) analysis showed that XH, SHY and YC in North China suffered more serious health risk from PAHs than other sites. In addition, higher TEQ and higher ECR were found in the size range of <1.1 µm, indicating that finer particles are associated with higher toxicity.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Material Particulado/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , China , Humanos , Medição de Risco
17.
J Environ Sci (China) ; 83: 152-160, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31221378

RESUMO

The structure of the boundary layer affects the evolution of ozone (O3), and research into this structure will provide important insights for understanding photochemical pollution. In this study, we conducted a one-month observation (from June 15 to July 14, 2016) of the boundary layer meteorological factors as well as O3 and its precursors in Luancheng County, Shijiazhuang (37°53'N, 114°38'E). Our research showed that photochemical pollution in Shijiazhuang is serious, and the mean hourly maximum and mean 8-hr maximum O3 concentrations are 97.9 ±â€¯26.1 and 84.4 ±â€¯22.4 ppbV, respectively. Meteorological factors play a significant role in the formation of O3. High temperatures and southeasterly winds lead to elevated O3 values, and at moderate relative humidity (40%-50%) and medium boundary layer heights (1200-1500 m), O3 production sensitivity occurred in the transitional region between volatile organic compounds (VOC) and nitrogen oxides (NOx) limitations, and the O3 concentration was the highest. The vertical profiles of O3 were also measured by a tethered balloon. The results showed that a large amount of O3 was stored in the residual layer, and the concentration was positively correlated with the O3 concentration measured the previous day. During the daytime of the following day, the contribution of O3 stored in the residual layer to the boundary layer reached 27% ±â€¯7% on average.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Ozônio/análise , Ozônio Estratosférico , China , Óxidos de Nitrogênio/análise , Compostos Orgânicos Voláteis/análise
18.
Huan Jing Ke Xue ; 40(5): 2027-2035, 2019 May 08.
Artigo em Chinês | MEDLINE | ID: mdl-31087837

RESUMO

To study the pollution characteristics, sources, and transportation process of PM2.5 and its chemical compositions in the Zhengzhou-Xinxiang region, PM2.5 samples were collected using a middle volume sampler, in Zhengzhou and Xinxiang urban areas for 30 consecutive days during the winter of 2016. The mass concentration of PM2.5 was measured gravimetrically. 17 trace metals were determined by inductively coupled plasma-mass spectrometry (ICP-MS), and 7 water-soluble ions were determined by ion chromatography. The enrichment factor (EF) method and principal component analysis were employed to determine the source apportionment. The results showed that the daily mean PM2.5 mass concentration during the winter sampling period of 2016 in Xinxiang and Zhengzhou was 223.87 µg·m-3 and 226.67 µg·m-3, respectively, which indicated that pollution levels were relatively high in both cities. The concentration of three macro elements (Al, Ca, and Fe) accounted for 50% of the total metal elements in both cities, while the heavy metals concentration was higher in Xinxiang than in Zhengzhou. The EFs of Cd, Ag, and Pb in Xinxiang were far higher than 1000, while only Cd was higher than 1000 in Zhengzhou. NO3-, SO42-, and NH4+ were the main ions in the two cities. They exceeded 94% of total water-soluble ions and existed in the forms of (NH4)2SO4 and NH4NO3. The principle component analysis showed that the main contributors to PM2.5 were a mixture of biomass combustion and secondary aerosol in Xinxiang, and a mixture of coal combustion and traffic emissions in Zhengzhou, accounting for 34.94% and 33.99% of total PM2.5 emissions, respectively.

19.
Huan Jing Ke Xue ; 40(4): 1545-1552, 2019 Apr 08.
Artigo em Chinês | MEDLINE | ID: mdl-31087894

RESUMO

In order to explore the characteristics of PM2.5 concentration and water-soluble inorganic ions in Zhengzhou City, a total of 170 PM2.5 samples were collected in the spring, summer, autumn, and winter seasons of 2016, with 30 days continuous sampling during each season. The mass concentration of PM2.5 was analyzed gravimetrically, water-soluble inorganic ions were determined by ion chromatography, and principle component analysis was employed for source apportionment. The results showed that the mass concentration of PM2.5 was 150.72µg·m-3 during the sampling period. The mass concentration was highest in winter and lowest in summer, and that of autumn is higher was higher than that of spring. The ions SO42-, NO3-, and NH4+ were the major WSIs found in PM2.5, accounting for 92.55%, 92.94%, 93.06%, and 93.15% of the total amount of the seven ions found in spring, summer, autumn, and winter, respectively. The anion-to-cation ratio was 0.886, which indicated that PM2.5 was slightly alkaline in Zhengzhou. Secondary inorganic species, including NH4+, NO3-, and SO42- were the major components of the water-soluble ions. These ions most likely existed in the form of NH4NO3 and (NH4)2SO4 during spring and summer, while they were present as NH4NO3, (NH4)2SO4 and NH4HSO4 in autumn. In addition to these three forms, NH4Cl or other forms may exist in winter. Industrial emissions, combustion, secondary transformation, soil, and construction dust were the major sources of the water-soluble ions in PM2.5.

20.
Huan Jing Ke Xue ; 40(3): 1071-1081, 2019 Mar 08.
Artigo em Chinês | MEDLINE | ID: mdl-31087953

RESUMO

To study the interannual variations of chemical composition and source apportionment, a field campaign was carried out to collect the PM2.5 temperance sample during the winter of 2015 and the winter of 2016 in Xinxiang urban areas. PM2.5 mass concentration, metal elements, and the water-soluble ions were determined and meteorological factors were recorded simultaneously. The results showed that the daily mean concentrations of PM2.5 indicated serious pollution with values of 226 µg·m-3 and 224 µg·m-3 in 2015 and 2016, respectively. The Cd and Pb elements in PM2.5 were significantly enriched, with EF more than 1000. However, compared with 2015, the enrichment effect of most metal elements showed a trend of decrease in 2016. The water-soluble ions were mainly composed of SO42-, NO3-, and NH4+. The results showed a trade-off effect between metal elements and water-soluble ions in the two study periods. The results of PCA and PMF analyses show that there were four main emission sources in Xinxiang city in winter, namely dust, secondary source, industrial source, and fossil fuel combustion source. Moreover, the main sources of PM2.5 was the mixed source of soil and building dust and secondary aerosol pollution, with contributions of 37.46% and 34.94% in the winters of 2015 and 2016, respectively.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA