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A dual-frequency, ground-based microwave radiometer (WVR-1100) is used to investigate the behavior of the atmosphere in terms of zenith brightness temperature ( T B ) at 23.8 and 31.4 GHz respectively. Some experimental findings in SKYNET Hefei site from September 2002 to August 2012 are presented. The cumulative distributions of T B at both frequencies for all sky conditions show four different regions, while only two regions can be identified for clear, lightly cloudy and cloudy condition. Annual cycle of T B at 23.8 GHz is apparently remarkable, indicating the large annual cycle of atmospheric water vapor. Regular seasonal variations of T B are observed with the strongest value in summer and the weakest in winter. [ABSTRACT FROM AUTHOR]

Highlights • The influence of the fluctuation of CO 2 concentration in the lower atmosphere is discussed in the measurement of XCO 2. • A weighting function optimized method is provided considering the actual CO 2 concentration profile and the proportion of the lower weighting function. • The method corrects the bias in the measurement and relaxes the atmosphere sensitivity to pressure. • More appropriate wavelengths have been provided for the further reference of development of an IPDA lidar. Abstract Weighting function can affect the retrieval of the column gas mixing ratio of integrated path differential absorption (IPDA) lidar because it contains the vertical distribution information of the target gas. In order to optimize the wavelengths within the 1.57 um spectral band for IPDA lidar for CO 2 measurement. The temperature, pressure and water vapor (TPH) sensitivity and the proportion of the weight function integration in the lower layer part to the total atmosphere layer (R) of each wavelength are calculated. The measurement errors of each wavelength are simulated with CO 2 fluctuation in the lower layer. The specific wavelength with the R value of 0.6 has been found to be a stable measurement bias which does not change with fluctuations, so the R value of 0.6 is used to optimize the wavelength for measurement CO 2. The simulation results show that the measurement error via wavelength is smaller than 0.05 ppm, when the TPH sensitivity is smaller than 0.95 and when R is about 0.6. This proposed method can be applicable for the further airborne or space-borne lidar development. [ABSTRACT FROM AUTHOR]

Abstract As one of the largest metropolitan areas in the world, Beijing has a high aerosol loading. Although the government has taken various measures to reduce emissions, the large-scale and intermittent occurrence of pollution is still a major issue. To understand the mechanisms and characteristics of pollution, Raman-Mie lidar and CE-318 sun photometer were used to study the aerosol vertical distribution and optical properties during dust, haze and clean periods in Beijing that occurred in September to October 2017. Combined with meteorological data, the sources and transmission paths of the pollution events were analyzed. The results are as follows. For the dust event, irregular particles with a large linear particle depolarization ratio played a leading role. The aerosol boundary layer height reached 3.5 km. The volume concentration of coarse particles was obviously larger in the volume size distribution. Strong northwest winds at high altitudes cause high-altitude long-distance transmission of pollutants. And this process can exacerbate air quality of Beijing. For the haze event, high-spherical water-soluble particles were dominant. The extinction coefficient exceeded 1 km−1 while the linear particle depolarization ratio was relatively small. The aerosol boundary layer height was <1 km. The range of aerosol optical depth at 440 nm varied between 0.8 and 2.4. Compared with the dust process, meteorological conditions contribute differently to the haze pollution. Aerosols from the south-west is one of the major resources of haze in Beijing. Combined with static weather such as low wind speed, the pollution level can be continuously increased. During the clean period, favorable weather conditions, such as high wind speed, provided good conditions for the diffusion of local particles. The extinction coefficient and the linear particle depolarization ratio were significantly lower. The single-scattering albedo fluctuated between 0.75 and 0.85, the scattering of light was weak and the visibility was generally high. Highlights • Dust pollution in autumn can exacerbate air quality of Beijing. • Aerosols from the south-west is one of the major resources of haze in Beijing. • Meteorological conditions contribute differently to the autumn pollution in Beijing. [ABSTRACT FROM AUTHOR]

With the aim of understanding the impact of aerosol particle size and chemical composition on CCN activity, the size-resolved cloud condensation nuclei (CCN) number concentration (N CCN ), particle number size distribution (PSD) (10–600 nm), and bulk chemical composition of particles with a diameter < 1.0 μm (PM 1 ) were measured simultaneously at Xinzhou, a suburban site in northern China, from 22 July to 26 August 2014. The N CCN was measured at five different supersaturations ( SS ) ranging from 0.075%–0.76%. Diurnal variations in the aerosol number concentration (N CN ), N CCN , the bulk aerosol activation ratio (AR), the hygroscopicity parameter ( κ chem ), and the ratio of 44 mass to charge ration ( m/z 44) to total organic signal in the component spectrum ( f 44 ), and the PSD were examined integrally to study the influence of particle size and chemical composition on CCN activation. We found that particle size was more related to the CCN activation ratios in the morning, whereas in the afternoon (~ 1400 LST), κ chem and f 44 were more closely associated with the bulk AR. Assuming the internal mixing of aerosol particles, N CCN was estimated using the bulk chemical composition and real-time PSD. We found that the predicted CCN number concentrations were underestimated by 20–30% at SS < 0.2% probably due to the measurement uncertainties. Estimates were more accurate at higher SS levels, suggesting that the hygroscopicity parameter based on bulk chemical composition information can provide a good estimate of CCN number concentrations. We studied the impacts of new particle formation (NPF) events on size-resolved CCN activity at the “growth” stage and “leveling-off” stage during a typical NPF event by comparing with the case during non-NPF event. It has been found that CCN activation was restrained at the “growth” stage during which larger particle diameters were needed to reach an activation diameter( D a ), and the bulk AR decreased as well. However, during the “leveling-off” stage, a lower D a was observed and CCN activation was greatly enhanced. [ABSTRACT FROM AUTHOR]

Lidar, radiosonde, and ground-based in situ nephelometer measurements made during an intensive field campaign carried out from July to September 2014 at the Xinzhou meteorological station were used to determine the aerosol hygroscopic growth effect in a cloud-capped, well-mixed boundary layer. Aerosol hygroscopic properties at 355 and 532 nm were examined for two cases with distinct aerosol layers. Lidar-derived maximum enhancement factors in terms of aerosol backscatter coefficient derived using a relative humidity ( RH ) reference value of 85% were 1.19 at 532 nm and 1.10 at 355 nm for Case I and 2.32 at 532 nm and 1.94 at 355 nm for Case II. To derive the aerosol particle hygroscopic growth factor at specific RH values, the Kasten and Hänel models were used. A comparison of the goodness of fit for the two models showed that the Kasten model performed better. The hygroscopic growth curve for RH >90% was much steeper than that for RH in the range of 85–90%. The slopes of the lidar-derived enhancement factor curve (measured from 85% to 95% RH ) and the nephelometer-derived enhancement factor curve (measured from 40% to 62% RH ) in Case I show similar trends, which lends confidence to using lidar measurements for studying aerosol particle hygroscopic growth. Data from a ground aerosol chemical speciation monitor showed that the larger values of aerosol hygroscopic enhancement factor in Case II corresponded to greater mass concentrations of sulfate and nitrate in the atmosphere. [ABSTRACT FROM AUTHOR]

Erythromycin residual, as a persistent, antibiotic pollutant, poses a serious threat to environmental and human health. Thus, developing effective technologies to eliminate erythromycin from the environment is urgent. In this study, a new fungus W1 identified as Aspergillus sydowii which can utilize erythromycin as its only carbon source was isolated from soil contaminated with erythromycin. The degradation efficiency of erythromycin by strain W1 was 84.05% within seven days under optimal conditions (30 °C, pH 6.0 and 100 mg L−1 erythromycin). The degradation pathway of erythromycin was proposed from four intermediates detected by HPLC-MS, and enzymes involved in erythromycin metabolism in strain W1 were preliminarily inferred. Notably, genomic and transcriptomic analysis also confirmed that strain W1 degrades erythromycin via glycoside hydrolase and esterase activity. This study demonstrated that A. sydowii W1 is a novel erythromycin-degrading strain, which has great potential for removing erythromycin from contaminated soils, and also provides a new perspective for other applications of this particular strain. [Display omitted] • A novel erythromycin-degrading fungus Aspergillus sydowii W1 was isolated from an erythromycin-contaminated sample. • The expression of 855 gene was relatively upregulated under erythromycin stress. • The erythromycin degradation pathway of A. sydowii W1 was illustrated based on the metabolites and transcriptomic data. • The esterase and glucoside hydrolase are the key enzymes involved the biodegradation process. [ABSTRACT FROM AUTHOR]

We have characterized the chemical composition and sources of submicron aerosol (PM 1 ) at a suburban site in Xinzhou in central China using an Aerosol Chemical Speciation Monitor from July 17 to September 5, 2014. The average (±1σ) PM 1 concentration was 35.4 (±20.8) μg/m 3 for the entire study period, indicating that Xinzhou was less polluted compared to the megacities in the North China Plain (NCP). The PM 1 was mainly composed of organic aerosol and sulfate, on average accounting for 33.1% and 32.4%, respectively, followed by nitrate (14.4%) and ammonium (11.8%). Higher sulfate and lower nitrate contributions than those in megacities in the NCP elucidated an important emission source of coal combustion in central China. Three organic aerosol (OA) factors, i.e., hydrocarbon-like OA (HOA), semi-volatile oxygenated OA (SV-OOA) and low-volatility OOA (LV-OOA), were identified using positive matrix factorization. Secondary OA (=SV-OOA + LV-OOA) dominated OA, on average accounting for 82%, indicating that OA at the Xinzhou site was overall oxidized. We also observed relatively similar aerosol bulk composition and OA composition at low and high mass loading periods, and also from the different source areas, indicating that aerosol species were homogeneously distributed over a regional scale near the site for most of the time during this study. Slightly higher mass concentrations and sulfate contributions from the southern air masses were likely due to the transport from the polluted cities, such as Taiyuan to the south. In addition, the daily variation of PM 1 in Xinzhou resembled that observed in Beijing, indicating that the wide-scale regional haze pollution often influences both the NCP and the central China. [ABSTRACT FROM AUTHOR]

The satellite-based estimation of dry PM 2.5 mass concentration near the surface is a big challenge in the aerosol remote sensing fields, but urgently needed by the environmental monitoring. We present an experimental validation of a physical PM 2.5 remote sensing (PMRS) method which is not dependent on geographical location, based on ground-based remote sensing measurements at Jinhua City, a typical middle size city in East of China. The PMRS method is designed to employ currently available satellite remote sensing parameters as many as possible, including aerosol optical depth (AOD), fine mode fraction (FMF), planetary boundary layer height (PBLH) and atmospheric relative humidity (RH), and thus be capable of deriving PM 2.5 from instantaneous remote sensing measurements under different pollution levels. The key processes of the PM 2.5 method including size cutting, volume visualization, bottom isolation and particle drying are directly validated by comparing with reference parameters. We found that the size cutting of the PMRS method has a significant bias (about 0.86) resulting from the use of fine mode fraction to estimate PM 2.5 among all size of aerosol particles, which should be systematically corrected. The validation results of the volume visualization and particle drying of the PMRS method are quite satisfied while the bottom isolation procedure brings currently the maximum uncertainty to the PM 2.5 remote sensing. The improved PMRS method shows good performance on the remote sensing of hourly PM 2.5 with an average error of about 38 μg/m 3 and relative error of about 31%. The correlation coefficient between remote sensing and in situ hourly PM 2.5 is about 0.67 with a linear slope of 1.03 and intercept of 11 μg/m 3 while the means are very close (110.7 μg/m 3 versus 118.6 μg/m 3 ). The validation study also helps find out future improvement directions and demonstrates the possible application to ground-based remote sensing data. [ABSTRACT FROM AUTHOR]

To explore the vertical distribution of the aerosol optical parameters over Jinhua City, southeast China, a Dual-wavelength Mie Polarization Raman Lidar (DMPRL) system was operated to obtain the atmospheric backscattering signals from June 2013 to May 2014. Profiles of aerosol occurrence frequency and aerosol optical parameters, including backscattering ratio, particle depolarization ratio, and color ratio, were retrieved from the lidar signals. The cases with a cloud base below 6 km and profiles on rainy days were eliminated. The multi-layer vertical aerosol structure was found in Jinhua area and the altitude-resolved optical properties varies with seasons. In autumn, winter and spring, the aerosol layer occurrence frequencies were higher than summer at 3–6 km, especially in spring. The mean particle depolarization ratio at 4–6 km exceeded 0.1 in autumn, winter, and spring, whereas it was <0.05 in summer. Aerosol with high color ratios appeared at 0–2 km in autumn. The analysis of one-year backward trajectories exhibits a dust dominating aerosol layer at 4–6 km in autumn, winter, and spring, a partially sea salt dominating aerosol layer at 0–2 km in autumn and a partially dust aerosol layer at 0–2 km in winter. Six cases were used to study the influence of aerosol advection and local sources vertical aerosol properties distribution. Through our analysis, aerosols at different altitudes are influenced by different sources, which are important for understanding the spatiotemporal characteristics of aerosol layers over Jinhua. The vertical distribution of aerosol properties in Jinhua area is affected by locally emitted aerosol , transported dust and ocean aerosol. • Multi-layer aerosol with corresponding properties observed by lidar over Jinhua. • High occurrences of aerosol layers were found at 3–6 km except summer. • Source-related aerosol vertical distribution dominated especially at 4–6 km. • Larger particles with high color ratios appeared at 0–2 km in autumn. • Regional and transported source aerosols affected the vertical aerosol properties. [ABSTRACT FROM AUTHOR]

Previous research has shown the significant transboundary air pollution (TAP) in China. Despite its adverse environmental and human health impacts, the characteristics and mechanisms of TAP have yet to be fully understood. This study comprehensively analyzed intensive ground and upper levels measurements along with the atmospheric modeling approach to determine the driving meteorological conditions responsible for the formation and evolution of a persistent severe PM 2.5 pollution episode in Central-East China (CEC, 112°E −118°E, 30°N −34°N) starting from 18:00 on Dec. 3 to 18:00 on Dec. 5, 2017, which had obvious characteristics of TAP and explosive increases in PM 2.5 concentration. We assessed and quantified contributions of local and nonlocal emissions to PM 2.5 in the region and different cities during the episode and determined the altitude level at which TAP occurred. Results show that PM 2.5 concentration in most cities in CEC region experienced two major increases: the first increase was due to the change in wind direction from south to north, transporting pollutants from north China to CEC; the second increase was driven by several important meteorological factors, including warm/cold advection at different altitudes, large-scale subsidence, and radiative cooling, jointly resulting in a deep (reaching around 800 m) and strong elevated temperature inversion with a significant reduction in mixing layer thickness and thus causing a rapid increase in PM 2.5 concentration in CEC region. On average, TAP accounted for 42% of total PM 2.5 concentration in the region during the event, in which the TAP impact varied by cities, ranging from ~26% to ~70%. Our findings demonstrate the synergetic effect of TAP and large-scale subsidence, providing a critical reference for air pollution forecast and assessment in the eastern China. • The formation of the studied episode was due to southward movement of a high pressure system, large-scale subsidence, and inversion of boundary layer temperature. • The slow-increase and rapid-increase phases in the episode were due to surface convergence and large-scale subsidence, respectively. • Air pollutants in North China can be transported to CEC at the ground level and in free troposphere, while the surface transport was the dominant. • Transboundary air pollution on average contributed 42% of the PM 2.5 concentration in the Central-East region in the episode. [ABSTRACT FROM AUTHOR]