Dissolved organic carbon (DOC) was measured in 483 precipitation samples collected at 10 sites in Northern China from December 2007 to November 2008. The annual volume-weighted mean (VWM) ...concentrations and wet deposition fluxes of DOC for 10 sites ranged from 2.4 to 3.9 mg C/L and 1.4 to 2.7 g C m
−2 yr
−1, respectively. The proportion of DOC to total organic carbon (TOC) was 79% on average, suggesting that a significant fraction of TOC was present as insoluble particulate organic carbon. Due to intensive domestic coal use for house heating and smaller dilution of scavenged organic carbon, higher VWM concentrations of DOC were observed during winter and spring than during summer and autumn. When precipitation events were classified via air mass back-trajectories, the mixed trajectories from SE and NW always corresponded to significantly higher DOC than those from SE or NW alone, coinciding with the centre of a low pressure system moved eastward and the wind direction changed from southeast to northwest. The results also showed that each site had a similar seasonal variation for DOC wet deposition flux. The largest flux occurred during the rainy season, and the lowest flux appeared during winter months. The product of the TC/DOC ratio and the DOC flux yielded an average TC wet deposition flux of 3.2 g C m
−2 yr
−1 in Northern China, accounting for 8.6% and 22% of the carbon sink magnitude (37 g C m
−2 yr
−1) in terrestrial ecosystems and anthropogenic carbon emissions (14 g C m
−2 yr
−1), respectively. This indicates that atmospheric wet deposition of TC is a significant carbon flux that cannot be neglected in regional models of the carbon cycle, and should be considered along with dry deposition in the removal mechanism for carbon from regional atmosphere.
To study the impacts of emission controls on aerosol physical and chemical properties, real-time measurements of size-resolved aerosol number concentration and chemical composition were conducted in ...urban Beijing during the 2014 Asia-Pacific Economic Cooperation (APEC) summit, in a period that a series of measures, for example shutting down or halting production from factories and power plants, and restricting the number of vehicles on the roads were implemented in Beijing and surrounding regions. Significantly, reductions in particle mass concentration (55% for PM
2.5
and 48% for PM
10
) were observed during the APEC summit. A clear decrease in secondary inorganic aerosols (SIA), such as sulphate, nitrate and ammonium, was found during APEC, with the reduction ranged from 65.7 to 72.2% for PM
1
, in which sulphate showed the largest decrease compared with periods before APEC. As a comparison, organics showed a much smaller decrease of 44.3% for PM
1
during APEC. These changes were mainly caused by large reductions in accumulation mode particles, which decreased by 36% compared with 19% for Aitken mode particles. The results from the positive matrix factorization (PMF) of particle number concentration indicate that regionally transported aerosols showed significant decreases (70%), similar to those of SIA during APEC, whereas primary factors from traffic and local combustion sources presented much smaller decreases, with the reduction ranged from 4 to 40%. The elevated contributions of these sources indicated the presence of strong local source emissions. The changes in particle chemical composition, size distribution and sources during the evolution of pollution episodes with and without emission controls are further illustrated. Our results highlight the importance of regional atmospheric transport in the formation of severe pollution episodes in Beijing, indicating that reducing the precursors of secondary aerosol over regional scales represent the key steps to reduce the urban particulate pollution. However, stricter emission controls on local source emissions are needed to further mitigate air pollution in Beijing.
Core Ideas
Variations in 16 seedling traits under normal and drought conditions were investigated.
Extremely resistant and sensitive accessions were identified for future analyses.
Under normal and ...drought conditions, 57 and 29 QTL were identified, respectively.
A total of 77 candidate genes were identified, and four were validated by qRT‐PCR.
Drought is one of the most important abiotic stressors affecting wheat (Triticum aestivum L.) production. To improve wheat yield, a better understanding of the genetic control of traits governing drought resistance is paramount. Here, using 645 wheat landraces, we evaluated 16 seedling traits related to root and shoot growth and water content under normal and drought (induced by polyethylene glycol) conditions. Extremely resistant and sensitive accessions were identified for future drought‐resistance breeding and further genetic analyses. A genome‐wide association study was performed for the 16 traits using 52,118 diversity arrays technology sequencing (DArT‐seq) markers. A total of 57 quantitative trait loci (QTL) were detected for seven traits under normal conditions, whereas 29 QTL were detected for eight traits under drought conditions. On the basis of these markers, we identified 56 candidate genes for six seedling traits under normal conditions, and 21 candidate genes for seven seedling traits under drought conditions. Four candidate genes were validated under normal and drought conditions using quantitative reverse transcription polymerase chain reaction (qRT‐PCR) data. The co‐localization of the flowering date and drought‐related traits indicates that the regulatory networks of flowering may also respond to drought stress or are associated with the correlated responses of these traits. The phenotypic and genetic elucidation of drought‐related traits will assist future gene discovery efforts and provide a basis for breeding drought‐resistant wheat cultivars.
Plant height (PH) plays a pivotal role in plant morphological architecture and is associated with yield potential in wheat. For the quantitative trait locus (QTL) analysis, a recombinant inbred line ...population was developed between varieties differing significantly in PH. Two major QTL were identified on chromosomes 4B (
) and 6D (
) in multiple environments, which were then validated in two different backgrounds by using closely linked markers.
explained 10.1-21.3% of the phenotypic variance, and the location corresponded to the dwarfing gene
.
might be a novel QTL for PH, explaining 6.6-13.6% of the phenotypic variance and affecting spike length, thousand-kernel weight, and spikelet compactness. Three candidate genes associated with plant growth and development were identified in the physical interval of
. Collectively, we identified a novel stable and major PH QTL,
, which could aid in the development of closely linked markers for marker-assisted breeding and cloning genes underlying this QTL.
The high-frequency monitoring of three-dimensional wind fields is crucial in planetary boundary layer meteorology. Doppler wind lidar and meteorological towers are the most important instruments for ...site observations of three-dimensional wind fields. This study systematically investigated and compared the performances of three wind measurement instruments: A Doppler wind lidar (Windcube 100s), cup anemometer/wind vane and sonic wind anemometer mounted on the 325 m meteorological tower in the polluted urban city of Beijing. The horizontal wind speed measurements of the Doppler wind lidar closely matched those of the cup anemometer and the sonic wind anemometer with high coefficients of determination (R2: 0.79–0.96 and 0.90–0.97, respectively). Moreover, the results also showed good agreement between the three measurements of the prevailing horizontal wind direction. Conversely, there were weak correlations between the vertical wind speeds of the Doppler wind lidar and sonic wind anemometer with low coefficients of determination (R2: 0.30–0.46). With increasing temporal scale, the consistency in the vertical wind increased. In addition, the Doppler wind lidar seemed to correlate better with the sonic wind anemometer at heights exceeding 300 m (R2: 0.48–0.77). Note that there was a remarkable difference between the Doppler wind lidar and 325 m meteorological tower observations as the aerosol concentrations changed rapidly. Different wind measurement instruments have unique advantages and are thus irreplaceable. The Doppler wind lidar is better at measuring larger turbulent eddies.
Grain number per spikelet (GNS) is a key determinant of grain yield in wheat. A recombinant inbred line population comprising 300 lines was developed from a cross between a high GNS variety H461 and ...Chinese Spring from which the reference genome assembly of bread wheat was obtained. Both parents and the recombinant inbred lines were genotyped using the wheat 55K single nucleotide polymorphism (SNP) array. A high-density genetic map containing 21,197 SNPs was obtained. These markers covered each of the 21 chromosomes with a total linkage distance of 3792.71 cM. Locations of these markers in this linkage map were highly consistent with their physical locations in the genome assembly of Chinese Spring. The two parents and the whole RIL population were assessed for GNS in two consecutive years at two different locations. Based on multi-environment phenotype data and best liner unbiased prediction values, three quantitative trait loci (QTL) for GNS were identified. One of them located on chromosomes 2B and the other two on 2D. Phenotypic variation explained by these loci varied from 3.07% to 26.57%. One of these QTL, QGns.sicau-2D-2, was identified in each of all trials conducted. Based on the best linear unbiased prediction values, this locus explained 19.59%–26.57% of phenotypic variation. A KASP (Kompetitive Allele-Specific PCR) marker closely linked with this locus was generated and used to validate the effects of this locus in three different genetic backgrounds. The identified QTL and the KASP marker developed for it will be highly valuable in fine-mapping the locus and in exploiting it for marker-assisted selection in wheat breeding programs.
Total spikelet number per spike (TSS) is one of the key components of grain yield in wheat. Chromosome (chr.) 2D contains numerous genes that control TSS. In this study, we evaluated 138 F8 ...recombinant inbred lines (RILs) derived from an F2 population of a synthetic hexaploid wheat line (SHW-L1) and a common wheat cultivar (Chuanmai 32) for TSS in six different environments. To identify quantitative trait loci (QTL) for TSS, we constructed an integrated high-density genetic map of chr. 2D containing two simple sequence repeats, 35 diversity array technology markers, and 143 single nucleotide polymorphisms. We identified three stable QTL for TSS that individually explained 9.7-19.2% of the phenotypic variation and predicted 23 putative candidate genes within the QTL mapping interval. Overall, our results provide insight into the genetic basis of TSS in synthetic hexaploid wheat that may be useful in breeding high-yielding wheat cultivars.
When gasoline is burned to power an automotive engine, a portion of the fuel remains unburned or is partially burned and leaves the engine as hydrocarbon and oxygenated compounds. In addition, a ...small portion of the fuel can escape the vehicle through evaporation. Changes in alkanes, olefins and aromatics each affect emissions differently, which could complicate control strategies for air pollution. In this study, we collected 31 gasoline samples over five provinces and cities（Beijing, Tianjin, Hebei, Shandong, and Shaanxi） in North China between 2012 and 2013. The organic composition of the gasoline samples was analyzed using the gas chromatography-mass spectrometry（GC-MS） method, and the aniline compounds were analyzed by solvent extraction and the GC-MS method. The ratios of alkanes, aromatics, olefins and other organic compounds in gasoline were 40.6%, 38.1%, 12.9% and 8.4%, respectively. The aromatic and benzene exceedances were 15 and 8 based on the China＇s gasoline standards（III）, and they accounted for 48.4% and 25.8% of all the gasoline samples, respectively. Strong carcinogen aniline compounds were detected in all 31 samples, and the content of aniline compounds in 3 samples exceeded 1%. The high proportion of aromatics and olefins in the gasoline increased the emissions of carbon monoxide（CO） and toxics, as well as the atmospheric photochemical reactivity of exhaust emissions, which could hasten the formation of secondary pollutants. Our results are helpful for redefining government strategies to control air pollution in North China and relevant for developing new refining technology throughout China.
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).
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.
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