Volatile organic compounds (VOCs) were continuously observated in a northern suburb of Nanjing, a typical industrial area in the Yangtze River Delta, in a summer observation period from 15th May to ...31st August 2013. The average concentration of total VOCs was (34.40±25.20)ppbv, including alkanes (14.98±12.72)ppbv, alkenes (7.35±5.93)ppbv, aromatics (9.06±6.64)ppbv and alkynes (3.02±2.01)ppbv, respectively. Source apportionment via Positive Matrix Factorization was conducted, and six major sources of VOCs were identified. The industry-related sources, including industrial emissions and industrial solvent usage, occupied the highest proportion, accounting for about 51.26% of the VOCs. Vehicular emissions occupied the second highest proportion, accounting for about 34.08%. The rest accounted for about 14.66%, including vegetation emission and liquefied petroleum gas/natural gas usage. Contributions of VOCs to photochemical O3 formation were evaluated by the application of a detailed chemical mechanism model (NCAR MM). Alkenes were the dominant contributors to the O3 photochemical production, followed by aromatics and alkanes. Alkynes had a very small impact on photochemical O3 formation. Based on the outcomes of the source apportionment, a sensitivity analysis of relative O3 reduction efficiency (RORE), under different source removal regimes such as using the reduction of VOCs from 10% to 100% as input, was conducted. The RORE was the highest (~20%–40%) when the VOCs from solvent-related sources decreased by 40%. The highest RORE values for vegetation emissions, industrial emissions, vehicle exhaust, and LPG/NG usage were presented in the scenarios of 50%, 80%, 40% and 40%, respectively.
•Industry-related sources were dominant contributors to the VOCs in the industrial area of Nanjing.•The VOCs from solvent-related sources in the industrial area of Nanjing were higher than those in urban Nanjing.•Alkenes and aromatics were the top two contributors to the O3 photochemical production.•The most cost-effective approach for VOCs reduction in the industrial area of Nanjing was proposed.
Air pollution has become a top environmental concern in China. In the present study, 9 years of PM₁₀and PM₂.₅data from an urban monitoring station in Beijing was analyzed relative to other gaseous ...pollutants and several meteorological parameters. The levels and characteristics of particulate matters as well as the sources and factors affecting them were provided in the present study. During the 9-year observation period, PM₁₀and PM₂.₅showed high levels, with annual mean values of 138.5 ± 92.9 and 72.3 ± 54.4 μg/m³, respectively. Slight decreasing trends of annual mean PM₁₀and PM₂.₅were observed; autumn was the main season that contributed to the decrease in annual mean PM₁₀and PM₂.₅. Higher values for both PM fractions were generally observed in the spring and summer months, respectively, whereas lower values were found in the summer and spring months, respectively. Pronounced diurnal variations were found for PM₁₀and PM₂.₅, which both displayed a bimodal pattern with peaks between 7:00 and 8:00 a.m. as well as 7:00 and 11:00 p.m.; a minimum generally appeared at approximately noon. The seasonal and diurnal variations in particulate concentration are mostly dominated by the seasonal and diurnal variability of boundary layer and source emissions. A principal components analysis revealed that both the traffic-related emissions and combustion sources were major contributions to the particles; their contributions ranged between 35.5–75.1 %. Furthermore, a directional analysis shows a stronger association between particles and the southerly winds, the PM derived from sources south of Beijing, most likely secondary PM, significantly affects concentrations at the sampling site. To improve air quality in Beijing, mitigation measures including phasing out high energy-consuming industries and prioritize the use of clean energy sources should be designed to reduce emissions from both local and regional sources.
To address the complex trajectory tracking problem of AUH near the seabed when performing high-precision operations such as comprehensive underwater inspections for offshore engineering structures, a ...prescribed performance control strategy with a finite-time performance function (FTPF) and the fast terminal sliding surface is proposed. The influence of ocean current is fully considered by the combination of ocean current velocity estimated by a current observer and ocean current disturbance in the dynamic model. An arctan-type disturbance observer and neural network are designed to compensate for environmental disturbances, model uncertainty, and thruster failure effects on the system. The system stability is proven by the Lyapunov method, and the numerical simulation shows that the proposed scheme is effective, robust, and efficient, even under disturbances and thruster failure.
•Compared with the traditional finite-time terminal sliding mode control, the proposed fast finite-time prescribed performance method can obtain a quick convergence with high steady-state accuracy. At the same time, the transient response of the system can be adjusted by the performance function.•A novel finite-time performance function is proposed. It can make the system error reach a specific steady-state accuracy at the preset convergence time, which matches better with the fast finite-time method.•The proposed method does not rely on the fuzzy logic structure and can make the system meet the prescribed performance, and explicitly set the convergence time, which is more suitable for the high-precision work of AUHs.
In recent years, photochemical smog and gray haze-fog have frequently appeared over northern China. To determine the spatial distribution of volatile organic compounds (VOC) during a pollution ...period, tethered balloon flights were conducted over a suburban site on the North China Plain. Statistical analysis showed that the VOCs concentrations peaked at the surface, and decreased with altitude. A rapid decrease appeared from the surface to 400 m, with concnetrations of alkanes, alkenes, aromatics and halocarbons decreasing by 48.0%, 53.3%, 43.3% and 51.1%, respectively. At heights in the range of 500–1000 m, alkenes concnetrations decline by 40.2%; alkanes and halocarbons concnetrations only decreased by 24.8% and 6.4%, respectively; and aromatics increased slightly by 5.5%. High concentrations VOCs covered a higher range of height (400 m) on heavy pollution days due to lacking of diffusion power. The VOCs concentrations decreased by 50% at 200 m on light pollution days. The transport of air mass affected the composition and concentration of high-altitude VOCs, especially on lightly polluted days. These air masses originated in areas with abundant traffic and combustion sources. Reactive aromatics (kOH>20,000 ppm−1 min−1 and kOH<20,000 ppm−1 min−1) were the main contributor to the ozone formation, accounting for 37%, on the surface on light pollution days. The contribution increased to 52% with pollution aggravated, and increased to 64% with height. The contributions of reactive aromatics were influenced by the degree of air mass aging. Under the umbrella of aging air mass, the contribution of reactive aromatics increased with height.
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•Decreases in VOCs of 43–53% were observed below 400 m.•In a range of 500–1000 m, alkanes and halocarbons decreased by 24.8% and 6.4%, and aromatics concentrations increased 5.5%.•High-level atmospheric VOCs were more affected by traffic and combustion emissions.•The contribution of reactive aromatics to the ozone formation increased with pollution aggravated and height.
Aim at the effects of the coastal characteristic on ozone pollution in the Yangtze River Delta (YRD), a campaign was launched at the Ningbo, China in the summer of 2020, which mainly covered the ...monitoring of the vertical profiles of ozone (O3) concentration, three-dimensional wind field, temperature and humidity profiles and parameters of boundary layer dynamic-thermodynamic structure. At the coastal research station, a sea-land breeze (SLB) circulation accompanied by a concurrent coastal low-level jets (CLLJ) structure was observed and identified during 11–12 May 2020. The sea breeze first formed at 10:00 LT on 11 May, turned to land breeze at night, and returned to sea breeze again at 10:00 LT the next morning, prevailing at altitudes of 0–0.5 km and 0–0.3 km respectively. Land breeze at night carries O3 from the inland to the sea forming high ozone levels over the sea, and the shift of the sea breeze during daytime further blew pollution back to the land. Additionally, the conversion of SLB contributed to the occurrence of CLLJ at the altitudes of ~0.3–0.7 km by 02:00 and 06:00 LT, of which the center of wind speed reached ~13 m s−1. The CLLJ-induced turbulent activity decoupled the residual layer (RL) and stable boundary layer, leading to a reduction of RL-O3 levels and an increase of ~50 μg m−3 in surface-O3 concentration. The YRD's unique coastal characteristics make O3 pollution causes in coastal areas more complicated.
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•SLB and coastal LLJ were captured by high-resolution instruments on the coast.•A complete SLB conversion has a great influence on O3 transport along the coast.•The coastal LLJ contributes to the abnormally elevated surface-O3 levels at night.
The simultaneous observation and analysis of atmospheric fine particles (PM2.5) on a regional scale is an important approach to develop control strategies for haze pollution. In this study, samples ...of filtered PM2.5 were collected simultaneously at three urban sites (Beijing, Tianjin, and Shijiazhuang) and at a regional background site (Xinglong) in the Beijing–Tianjin–Hebei (BTH) region from June 2014 to April 2015. The PM2.5 at the four sites was mainly comprised of organic matter, secondary inorganic ions, and mineral dust. Positive matrix factorization (PMF) demonstrated that, on an annual basis, secondary inorganic aerosol was the largest PM2.5 source in this region, accounting for 29.2–40.5 % of the PM2.5 mass at the urban sites; the second-largest PM2.5 source was motor vehicle exhaust, particularly in Beijing (24.9 %), whereas coal combustion was also a large source in Tianjin (12.4 %) and Shijiazhuang (15.5 %), with particular dominance in winter. Secondary inorganic aerosol plays a vital role in the haze process, with the exception of the spring haze in Shijiazhuang and Tianjin, for which the dust source was crucial. In addition to secondary transformations, local direct emissions (coal combustion and motor vehicle exhaust) significantly contribute to the winter haze at the urban sites. Moreover, with the aggravation of haze pollution, the OC / EC mass ratio of PM2.5 decreased considerably and the nitrate-rich secondary aerosol increased during all four seasons in Beijing, both of which indicate that local motor vehicle emissions significantly contribute to the severe haze episodes in Beijing. To assess the impacts of regional transport on haze pollution, the PMF results were further processed with backward-trajectory cluster analysis, revealing that haze pollution usually occurred when air masses originating from polluted industrial regions in the south prevailed and is characterized by high PM2.5 loadings with considerable contributions from secondary aerosols. This study suggests that control strategies to mitigate haze pollution in the BTH region should focus on the reduction of gaseous precursor emissions from fossil fuel combustion (motor vehicle emissions in Beijing and coal combustion in Tianjin, Hebei, and nearby provinces).
The spatial and temporal distribution of atmospheric chloromethane (CH3Cl) in China was investigated between 2012 and 2014, and the sources of CH3Cl were evaluated by positive matrix factorization ...(PMF) according to PMF 5.0 (USEPA). Various concentrations of CH3Cl were found throughout China, ranging from 506.4 ± 110.5 to 1132.1 ± 523.3 pptv, showing the characteristics of high in the southeast and low in the northwest. The correlation between CH3Cl and chlorofluorocarbon-12 (CFC-12) at most sites was greater than 0.5 and presented regional characteristics. The distribution of CH3Cl in China is related to the degree of economic development, the high-concentration sites were located in the economically developed eastern region. The CH3Cl concentrations at western sites were similar to the global average and increased with latitude and altitude, indicating that this region was least affected by anthropogenic activities. The annual average concentrations of atmospheric CH3Cl in the northeastern region were below 730 pptv but had strong seasonal fluctuations. Chemical production was the main CH3Cl source in the northeast background areas (46%), while industrial combustion contributed 42% of the CH3Cl in the northeast urban areas. Large seasonal variations combined with a high relative standard deviation were observed in the southern region. Relative to the southwest, in the southeast, the onset of lower concentrations was delayed until September–October, and higher concentrations persisted for longer. Chemical production and biomass burning were the main sources in the southwest, while Chemical production and solvent use were the main contributors in the southeast. The Beijing area is discussed separately as a super megacity. No obvious seasonal fluctuations were observed in the Beijing area. According to the source analysis, chemical production contributed approximately 60% of the atmospheric CH3Cl in the Beijing area, while 15–24% was from solvent release.
•High concentrations of CH3Cl are concentrated in the central and eastern regions in China.•Chemical production is the main source of atmospheric CH3Cl in China.•Industrial combustion is the second source of the CH3Cl in the northeast.•Biomass burning and solvent use are important CH3Cl contributors in the southern region.
The secondary organic aerosol (SOA) concentration is generally underestimated by models. Recent studies suggest that the underprediction is related to underestimations of aromatic volatile organic ...compound (VOC) emissions and SOA yields in current models. Here, the impacts of these two factors in China were investigated with the regional air quality modeling system RAMS-CMAQ, referring to field observations during the episode from October 14 to November 14, 2014. Comparisons between the observed and modeled SOA of four sensitivity simulation cases indicated the significant impacts of the two underestimated factors on the SOA output. By considering these two aspects, the simulated mean SOA concentrations significantly increased by nearly 4 times with a good representation of the intensively temporal variations of concentrations, which were largely controlled by photochemical processes rather than meteorological conditions. The improvement in SOA compensated for the underestimations by approximately 23.5% and contributed to the mean fraction of SOA to organic aerosol (OA) by increasing the fraction from less than 7% to more than 25%, which was closer to the observed result. These results suggested a more reasonable and more realistic representation of SOA formation in the model after allowing for the two factors. Due to the better simulation of SOA, predictions of OA were correspondingly improved when the correlation coefficient increased from 0.57 to 0.73 and other bias parameters were reduced, which indicated the improved ability of our model to trace the temporal variations of OA. Based on the improved simulation throughout the episode, the mean SOA concentration was obviously higher in eastern China than in the west. The highest concentration appeared in the Sichuan Basin and Pearl River Delta (PRD) areas, with values of 6–11 μg/m3 and 8–17 μg/m3, respectively. Over the wide regions of central and eastern China, the dominant component in SOA was formed from anthropogenic sources (ASOA), generally accounting for more than 60%.
•Aromatic-derived SOA formations under different NOx concentrations are incorporated in the model.•The impacts of underestimated aromatic emissions and SOA yields on SOA production are evaluated.•By the considerations of two underestimated factors, modeled SOA concentrations increased by nearly 4 times.•Over 60% of SOA were formed from anthropogenic precursors in central and eastern China.
Key message
This study found that the intergenic circRNAs of wheat were more abundant than those of other plants. More importantly, a circRNA-mediated network associated with tillering was ...constructed for the first time.
Circular RNAs (circRNAs) are a class of endogenous non-coding RNAs with covalently closed circular structures, which play an important role in transcriptional and post-transcriptional regulation. Tiller is an important agronomic trait that determines plant morphological architecture and affects spike number in wheat. However, no studies on the characteristics and functions of circRNAs involved in the regulation of wheat tiller. Here, we performed a genome-wide identification of circRNAs using ribosomal-depleted RNA-seq from wheat tiller of two pairs near-isogenic lines. A total of 686 circRNAs were identified and distributed on 21 chromosomes of wheat, of which 537 were novel circRNAs. Unlike other plants, the majority of these circRNAs (61.8%) were derived from intergenic regions. One circRNA-mediated network associated with tillering was constructed through weighted gene co-expression network analysis, including 323 circRNAs, 117 miRNAs, and 968 mRNAs. GO and pathway enrichment analysis of mRNAs suggested that these circRNAs are involved in cell cycle, ncRNA export from nucleus, developmental process, plant hormone signal transduction, MAPK signaling pathway, RNA degradation. Of these circRNAs, ten circRNAs are associated with known tillering/branching genes in rice or
Arabidopsis thaliana
, including
OsCesA7
,
EBR1
,
DTE1
,
CRD1
,
LPA1
,
PAY1
,
LRK1
,
OsNR2
,
OsCCA1
,
OsBZR1
. In summary, we present the first study of the identification and characterization of circRNAs in wheat tiller, and the results suggest these circRNAs associated with tillering could play an important role in wheat tiller formation and development.
In 2017, a coal banning area of approximately 10,000 square kilometers was established in the Beijing-Tianjin-Hebei (BTH) region of China for the first time. This study compared the change of ...elemental concentrations during the autumn and winter of 2016 and 2017, and analyzed the environmental and health benefits of the coal banning policy. Result showed that compared to 2016, the reduction rate of atmospheric particulate matter with an aerodynamic diameter no larger than 2.5 μm (PM2.5) in 2017 was as high as 63.5% (p < 0.01), and that of the total elements in PM2.5 was up to 43% (p < 0.01). Coal consumption, transportation, industry, soil dust, and fuel consumption were the main sources of these elements in BTH. Coal consumption and industry accounted for 5.8–26.2% and 6.5–31.3%, respectively, of the total elements. After the coal banning area was established, the elements from coal consumption were reduced by 13.5–60.3% (the background station was reduced by 19.6%, p < 0.05), and those from industrial sources were reduced by 11–80.1%. The results of the health risk assessment showed that the carcinogenic risk of the coal consumption and industrial sources had been reduced by 30.7–48.3% in 2017. The policy of the coal banning is very effective in controlling the air pollution in urban agglomeration in developing countries and has resulted in great health and environmental benefits.
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•Coal Banning Area is the most efficient pollution control measure in BTH in 2017.•The measure cut down the bulk coal consumption by 10.2% in the 10,000 km2 region.•The measure has resulted in the high benefits of environment and health in BTH.•PM2.5 and total elements declined drastically by 63.5% and 43% in 2017.•The carcinogenic risk index of hazardous elements decreased by 36.3% in BTH.
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