Three field campaigns were conducted before, during, and after the 2010 World Expo in Shanghai, aiming to understand the response of secondary aerosol components to both control measures and human ...activities. In spring, PM2.5 (particulate matter) averaged 34.5 ± 20.9 μg m−3 with a severe pollution episode influenced by a floating dust originating from northwestern China on 26–28 April, right before the opening of the expo. With the approaching expo a significant increasing trend of SNA (SO42−, NO3−, and NH4+) concentrations was observed from 22 April to 2 May, attributed to the enhanced human activities. Nitrate had the most significant daily increasing rate of 1.1 μg m−3d−1 due to enhanced vehicle emission. In summer, two intensive pollution episodes were found to be a mixed pollution of SNA with biomass burning due to loose control of post-harvest straw burning. In the autumn phase of the expo, before the closing of the expo (20–30 October), the air quality over Shanghai was much better than ever before. However, the air quality rapidly plummeted as soon as the expo was announced closed. SNA increased 3–6 fold to be 42.1 and 68.2 μg m−3 on 31 October and 1 November, respectively, as compared to 20–30 October. Of which, nitrate increased most ~5–8 fold, indicating the serious impact from enhanced vehicle emission. Compared to the spring and summer of 2009, NO3− increased 12–15% while SO42− showed reductions of 15–30%. Continuous desulfurization of SO2 emission from power plants in recent years was responsible for the lowered SO42−, while increased traffic emission from the tremendous number of expo visitors was the major contributor to the increased NO3−. Compared to the autumn of 2009, all the ion components increased in 2010, owing to the lifting of emission control measures after the expo. SO42− was found least increased while NO3− and Ca2+ had tremendous increases of 150 and 320%, respectively. The anthropogenic Ca as a tracer from construction dust increased from 2.88 ± 1.85 μg m−3 during the expo to 6.98 ± 3.19 μg m−3 during the post-expo period, attributed to the resumption of construction works after the expo. The lack of successive control measures with the loose regulations after the expo were responsible for this jump of the bad quality. The ratio of NO3−/SO42− in PM2.5 over Shanghai had a significant increasing trend from ~0.3 in the early 2000s to more than 1.0 in 2010, indicating the increasing role of mobile sources. Reducing NOx emission will be China's priority in the future in order to improve the air quality over the megacities. In addition, lowering mineral aerosol components (e.g., Ca2+) was also demonstrated to be beneficial for alleviating air pollution in China. This study demonstrated that stringent emission control measures aiming at mega-events in China could achieve positive benefits on improving the air quality in a short term. However, persistent efforts of curbing the anthropogenic emission remain a long way to go in the future.
The South Pole Telescope (SPT) has systematically identified 81 high-redshift, strongly gravitationally lensed, dusty star-forming galaxies (DSFGs) in a 2500 square degree cosmological ...millimeter-wave survey. We present the final spectroscopic redshift survey of this flux-limited (S870 m > 25 mJy) sample, initially selected at 1.4 mm. The redshift survey was conducted with the Atacama Large Millimeter/submillimeter Array across the 3 mm spectral window, targeting carbon monoxide line emission. By combining these measurements with ancillary data, the SPT sample is now spectroscopically complete, with redshifts spanning 1.9 < z < 6.9 and a median of . We present the millimeter through far-infrared photometry and spectral energy density fits for all sources, along with their inferred intrinsic properties. Comparing the properties of the SPT sources to the unlensed DSFG population, we demonstrate that the SPT-selected DSFGs represent the most extreme infrared-luminous galaxies, even after accounting for strong gravitational lensing. The SPT sources have a median star formation rate of and a median dust mass of . However, the inferred gas depletion timescales of the SPT sources are comparable to those of unlensed DSFGs, once redshift is taken into account. This SPT sample contains roughly half of the known spectroscopically confirmed DSFGs at z > 5, making this the largest sample of high-redshift DSFGs to date, and enabling the "high-redshift tail" of extremely luminous DSFGs to be measured. Though galaxy formation models struggle to account for the SPT redshift distribution, the larger sample statistics from this complete and well-defined survey will help inform future theoretical efforts.
An innovative extended response surface modeling technique (ERSM v1.0) is developed to characterize the nonlinear response of fine particles (PM2.5) to large and simultaneous changes of multiple ...precursor emissions from multiple regions and sectors. The ERSM technique is developed based on the conventional response surface modeling (RSM) technique; it first quantifies the relationship between PM2.5 concentrations and the emissions of gaseous precursors from each single region using the conventional RSM technique, and then assesses the effects of inter-regional transport of PM2.5 and its gaseous precursors on PM2.5 concentrations in the target region. We apply this novel technique with a widely used regional chemical transport model (CTM) over the Yangtze River delta (YRD) region of China, and evaluate the response of PM2.5 and its inorganic components to the emissions of 36 pollutant–region–sector combinations. The predicted PM2.5 concentrations agree well with independent CTM simulations; the correlation coefficients are larger than 0.98 and 0.99, and the mean normalized errors (MNEs) are less than 1 and 2% for January and August, respectively. It is also demonstrated that the ERSM technique could reproduce fairly well the response of PM2.5 to continuous changes of precursor emission levels between zero and 150%. Employing this new technique, we identify the major sources contributing to PM2.5 and its inorganic components in the YRD region. The nonlinearity in the response of PM2.5 to emission changes is characterized and the underlying chemical processes are illustrated.
Regional trans-boundary air pollution has become an important issue in the field of air pollution modeling. This paper presents the results of the implementation of the MM5-CMAQ modeling system in ...the Yangtze River Delta (YRD) for the months of January and July of 2004. The meteorological parameters are obtained by using the MM5 model. A new regional emission inventory with spatial and temporal allocations based on local statistical data has been developed to provide input emissions data to the MM5-CMAQ modeling system. The pollutant concentrations obtained from the MM5-CMAQ modeling system have been compared with observational data from the national air pollution monitoring network. It is found that air quality in winter in the YRD is generally worse than in summer, due mainly to unfavorable meteorological dispersion conditions. In winter, the pollution transport from Northern China to the YRD reinforces the pollution caused by large local emissions. The monthly average concentration of SO2 in the YRD is 0.026 ± 0.011 mg m−3 in January and 0.017 ± 0.009 mg m−3 in July. Monthly average concentrations of NO2 in the YRD in January and July are 0.021 ± 0.009 mg m−3, and 0.014 ± 0.008 mg m−3, respectively. The monthly average concentration of PM10 in the YRD is 0.080 ± 0.028 mg m−3 in January and 0.025 ± 0.015 mg m−3 in July. Visibility is also a problem, with average deciview values of 26.4 ± 2.95 dcv in winter and 17.6 ± 3.3 dcv in summer. The ozone concentration in the downtown area of a city like Zhoushan can be very high, with the highest simulated value reaching 0.24 mg m−3. In January, the monthly average concentration of O3 in the YRD is 0.052 ± 0.011 mg m−3, and 0.054 ± 0.008 mg m−3 in July. Our results show that ozone and haze have become extremely important issues in the regional air quality. Thus, regional air pollution control is urgently needed to improve air quality in the YRD.
Abstract
Reconnection fronts, also known as dipolarization fronts (DFs), and kinetic Alfvén waves (KAWs) are two of the widely observed structures and waves in the terrestrial magnetotail, but their ...correlation remains elusive in previous spacecraft measurements. Using high-resolution Magnetospheric Multiscale data, here we provide the first observational identification of KAWs behind the DF. These low-frequency dispersive KAWs propagate quasi-perpendicular to the magnetic field at phase speeds slower than local Alfvén speed, and are highly correlated with high-frequency whistlers propagating obliquely to the magnetic field. Specifically, whistlers appear at local magnetic field minima (wave troughs of KAWs) and disappear at local magnetic field maxima (wave crests of KAWs), highly consistent with the source region of whistler waves previously reported near equator and dayside magnetopause. Our study also suggests that the KAWs behind DFs could originate from the diffusion region of magnetic reconnection. These findings improve our understanding of the relationship between DFs, KAWs, and whistler waves in terrestrial magnetotail.
Naringinase was mainly obtained by microbial fermentation, and mutagenesis was a major way for obtaining excellent mutants. The aim of this study was to screen out a high naringinase yielding mutant ...to enhance the potential application value of its industrialization and compare the effects of different mutagenic methods on the enzyme activity of the strain. A novel producing naringinase strain, Aspergillus tubingensis MN589840, was isolated from mildewed pomelo peel, later subjected to mutagenesis including UV, ARTP and UV‐ARTP. After five rounds iterative mutagenesis, the mutants U1, A6 and UA13 were screened out with 1448·49, 1848·71, 2475·16 U mg−1 enzyme activity, the naringinase productivity raised by 79·08, 123·56 and 206%, respectively. In addition, the naringinase activity of three mutants rose after each round of iterative mutagenesis. These results indicated that the mutagenesis efficiency of UV‐ARTP was higher than that of single ARTP, and both are better than UV. In summary, the iterative UV‐ARTP mutagenesis is an effective strategy for screening high naringinase‐producing strains.
Significance and impact of the study: The ‘delayed bitterness’ of naringin in citrus processing is a challenging problem restricting the development of citrus processing industry. Naringinase can transform naringin to naringenin for debittering. Therefore, it is significant to breed high naringinase‐producing strains suitable for industrialization. In this study, we screened a naringinase high‐yielding mutant, which had potential industrial application value and laid a foundation for the development of citrus processing industry. In addition, the method of iterative UV‐ARTP mutagenesis provided an effective strategy for breeding high‐yield naringinase‐producing mutants.
A new type of electron-scale coherent structure, referred to as electron vortex magnetic holes, was identified recently in the Earth's magnetosheath turbulent plasma. These electron-scale magnetic ...holes are characterized by magnetic field strength depression, electron density enhancement, temperature and temperature anisotropy increase (a significant increase in perpendicular temperature and a decrease in parallel temperature), and an electron vortex formed by the trapped electrons. The strong increase of electron temperature indicates that these magnetic holes have a strong connection with the energization of electrons. Here, using high time resolution in situ measurements from the MMS mission, it is further shown that electron-scale whistler waves coexist with electron-scale magnetic holes. These whistler waves were found not propagating from remote regions, but generated locally due to electron temperature anisotropy (Te /Te ) inside the magnetic holes. This study provides new insights into the electron-scale plasma dynamics in turbulent plasmas.
Given observed initial conditions, how well do coupled atmosphere-ocean models predict precipitation climatology with 1-month lead forecast? And how do the models' biases in climatology in turn ...affect prediction of seasonal anomalies? We address these questions based on analysis of 1-month lead retrospective predictions for 21 years of 1981-2001 made by 13 state-of-the-art coupled climate models and their multi-model ensemble (MME). The evaluation of the precipitation climatology is based on a newly designed metrics that consists of the annual mean, the solstitial mode and equinoctial asymmetric mode of the annual cycle, and the rainy season characteristics. We find that the 1-month lead seasonal prediction made by the 13-model ensemble has skills that are much higher than those in individual model ensemble predictions and approached to those in the ERA-40 and NCEP-2 reanalysis in terms of both the precipitation climatology and seasonal anomalies. We also demonstrate that the skill for individual coupled models in predicting seasonal precipitation anomalies is positively correlated with its performances on prediction of the annual mean and annual cycle of precipitation. In addition, the seasonal prediction skill for the tropical SST anomalies, which are the major predictability source of monsoon precipitation in the current coupled models, is closely link to the models' ability in simulating the SST mean state. Correction of the inherent bias in the mean state is critical for improving the long-lead seasonal prediction. Most individual coupled models reproduce realistically the long-term annual mean precipitation and the first annual cycle (solstitial mode), but they have difficulty in capturing the second annual (equinoctial asymmetric) mode faithfully, especially over the Indian Ocean (IO) and Western North Pacific (WNP) where the seasonal cycle in SST has significant biases. The coupled models replicate the monsoon rain domains very well except in the East Asian subtropical monsoon and the tropical WNP summer monsoon regions. The models also capture the gross features of the seasonal march of the rainy season including onset and withdraw of the Asian-Australian monsoon system over four major sub-domains, but striking deficiencies in the coupled model predictions are observed over the South China Sea and WNP region, where considerable biases exist in both the amplitude and phase of the annual cycle and the summer precipitation amount and its interannual variability are underestimated.
In this synthesis, we assess present research and anticipate future development needs in modeling water quality in watersheds. We first discuss areas of potential improvement in the representation of ...freshwater systems pertaining to water quality, including representation of environmental interfaces, in‐stream water quality and process interactions, soil health and land management, and (peri‐)urban areas. In addition, we provide insights into the contemporary challenges in the practices of watershed water quality modeling, including quality control of monitoring data, model parameterization and calibration, uncertainty management, scale mismatches, and provisioning of modeling tools. Finally, we make three recommendations to provide a path forward for improving watershed water quality modeling science, infrastructure, and practices. These include building stronger collaborations between experimentalists and modelers, bridging gaps between modelers and stakeholders, and cultivating and applying procedural knowledge to better govern and support water quality modeling processes within organizations.
Key Points
We assess four potential improvements in water quality modeling: environmental interfaces, in‐stream processes, soil health, and urban areas
Challenges include data quality control, model calibration, uncertainty management, scale mismatches, and model tool provision
Modelers need to strengthen connections with experimentalists and stakeholders and cultivate procedural knowledge for modeling processes
A new inventory of air pollutant emissions in Asia in the year 2006 is developed to support the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B) funded by the National Aeronautics and ...Space Administration (NASA). Emissions are estimated for all major anthropogenic sources, excluding biomass burning. We estimate total Asian anthropogenic emissions in the year 2006 as follows: 47.1 Tg SO2, 36.7 Tg NOx, 298.2 Tg CO, 54.6 Tg NMVOC, 29.2 Tg PM10, 22.2 Tg PM2.5, 2.97 Tg BC, and 6.57 Tg OC. We emphasize emissions from China because they dominate the Asia pollutant outflow to the Pacific and the increase of emissions from China since 2000 is of great concern. We have implemented a series of improved methodologies to gain a better understanding of emissions from China, including a detailed technology-based approach, a dynamic methodology representing rapid technology renewal, critical examination of energy statistics, and a new scheme of NMVOC speciation for model-ready emissions. We estimate China's anthropogenic emissions in the year 2006 to be as follows: 31.0 Tg SO2, 20.8 Tg NOx, 166.9 Tg CO, 23.2 Tg NMVOC, 18.2 Tg PM10, 13.3 Tg PM2.5, 1.8 Tg BC, and 3.2 Tg OC. We have also estimated 2001 emissions for China using the same methodology and found that all species show an increasing trend during 2001–2006: 36% increase for SO2, 55% for NOx, 18% for CO, 29% for VOC, 13% for PM10, and 14% for PM2.5, BC, and OC. Emissions are gridded at a resolution of 30 min×30 min and can be accessed at our web site (http://mic.greenresource.cn/intex-b2006).
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