Xu T.,Beijing Normal University |
Liu S.,Beijing Normal University |
Xu L.,Beijing Normal University |
Chen Y.,Beijing Normal University |
And 4 more authors.
Remote Sensing | Year: 2015
Currently, thermal remote sensing-based evapotranspiration (ET) models can only calculate instantaneous ET at the time of satellite overpass. Five temporal upscaling methods, namely, constant evaporative fraction (ConEF), corrected ConEF (CorEF), diurnal evaporative fraction (DiEF), constant solar radiation ratio (SolRad), and constant reference evaporative fraction (ConETrF), were selected to upscale the instantaneous ET to daily values. Moreover, five temporal reconstruction approaches, namely, data assimilation (ET_EnKF and ET_SCE_UA), surface resistance (ET_SR), reference evapotranspiration (ET_ETrF), and harmonic analysis of time series (ET_HANTS), were used to produce continuous daily ET with discrete clear-sky daily ET values. For clear-sky daily ET generation, SolRad and ConETrF produced the best estimates. In contrast, ConEF usually underestimated the daily ET. The optimum method, however, was found by combining SolRad and ConETrF, which produced the lowest root-mean-square error (RMSE) values. For continuous daily ET production, ET_ETrF and ET_SCE_UA performed the best, whereas the ET_SR and ET_HANTS methods had large errors. The annual ET distributions over the Beijing area were calculated with these methods. The spatial ET distributions from ET_ETrF and ET_SCE_UA had the same trend as ETWatch products, and had a smaller RMSE when compared with ET observations derived from the water balance method. © 2015 by the authors.
Wang J.,Nanjing University of Information Science and Technology |
Wang J.,Yangzhou Environmental Monitoring Center |
Ge X.,Nanjing University of Information Science and Technology |
Chen Y.,Nanjing University of Information Science and Technology |
And 8 more authors.
Atmospheric Chemistry and Physics | Year: 2016
In this work, the Aerodyne soot particle - aerosol mass spectrometer (SP-AMS) was deployed for the first time during the spring of 2015 in urban Nanjing, a megacity in the Yangtze River Delta (YRD) of China, for online characterization of the submicron aerosols (PM1). The SP-AMS enables real-time and fast quantification of refractory black carbon (rBC) simultaneously with other non-refractory species (ammonium, sulfate, nitrate, chloride, and organics). The average PM1 concentration was found to be 28.2ĝ€-μgĝ€-mĝ'3, with organics (45ĝ€-%) as the most abundant component, following by sulfate (19.3ĝ€-%), nitrate (13.6ĝ€-%), ammonium (11.1ĝ€-%), rBC (9.7ĝ€-%), and chloride (1.3ĝ€-%). These PM1 species together can reconstruct ĝ1/4ĝ€-44ĝ€-% of the light extinction during this campaign based on the IMPROVE method. Chemically resolved mass-based size distributions revealed that small particles especially ultrafine ones (<ĝ€-100ĝ€-nm vacuum aerodynamic diameter) were dominated by organics and rBC, while large particles had significant contributions from secondary inorganic species. Source apportionment of organic aerosols (OA) yielded four OA subcomponents, including hydrocarbon-like OA (HOA), cooking-related OA (COA), semi-volatile oxygenated OA (SV-OOA), and low-volatility oxygenated OA (LV-OOA). Overall, secondary organic aerosol (SOA, equal to the sum of SV-OOA and LV-OOA) dominated the total OA mass (55.5ĝ€-%), but primary organic aerosol (POA, equal to the sum of HOA and COA) can outweigh SOA in the early morning and evening due to enhanced human activities. High OA concentrations were often associated with high mass fractions of POA and rBC, indicating the important role of anthropogenic emissions during heavy pollution events. The diurnal cycles of nitrate, chloride, and SV-OOA both showed good anti-correlations with air temperatures, suggesting their variations were likely driven by thermodynamic equilibria and gas-to-particle partitioning. On the other hand, in contrast to other species, sulfate, and LV-OOA concentrations increased in the afternoon, and showed no positive correlations with relative humidity (RH), likely indicating the contribution from photochemical oxidation is dominant over that of aqueous-phase processing for their formations. The bivariate polar plots show that the SV-OOA was formed locally, and the variations of hydrogen-to-carbon (Hĝ€-ĝ•ĝ€-C) and oxygen-to-carbon (Oĝ€-ĝ•ĝ€-C) ratios in the Van Krevelen space further suggests an evolution pathway of SV-OOA to LV-OOA. Our findings regarding springtime aerosol chemistry in Nanjing may have important implications for the air quality remediation in the densely populated regions. © Author(s) 2016.
Yi R.,Yangzhou Environmental Monitoring Center |
Wang Y.,Yangzhou Environmental Monitoring Center |
Zhang Y.,China Environmental Monitoring Center |
Shi Y.,China Environmental Monitoring Center |
Li M.,China Environmental Monitoring Center
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2015
To investigate the pollution characteristics and influence factors of ozone, this article analyzed the data collected at national environmental and meteorological monitoring stations in 25 cities of Yangtze River Delta in 2013. Results showed that: (1) O3 concentrations in 24 cities exceeded the Class II Ambient Air Quality Standard (GB 3095-2012) to different degrees except Huai'an city. The O3 exceedance rate ranged from 1.6% to 15.1% with an average of 5.8%, which was below the rate of Pearl River Delta (8.9%) and Beijing-Tianjin-Hebei region (9.7%). (2) The pollution levels of O3 were the worst from May to August, but the pollution of PM is relatively mild in the same period with an opposite trend in monthly variation. (3) From the spatial distribution, the O3 pollution in Yangtze River Delta showed continuous distribution. Shanghai and the surrounding cities were more polluted. (4) The number of private cars was significantly related to the annual concentration of NO2 and the number of days with O3 nonattainment, and the correlation coefficients were 0.672 and 0.564 respectively. The peak of daily traffic flow was basically corresponded to O3 hourly concentration peak. (5) High temperature and long-time sunshine led to high O3 concentration. With the increasing of relative humidity and wind speed, O3 exceeded rate and average concentration showed a trend of firstly increasing and then decreasing. ©, 2015, Science Press. All right reserved.
Fang L.,CAS Anhui Institute of Optics and Fine Mechanics |
Zhao N.-J.,CAS Anhui Institute of Optics and Fine Mechanics |
Meng D.-S.,CAS Anhui Institute of Optics and Fine Mechanics |
Yuan J.,Yangzhou Environmental Monitoring Center |
And 9 more authors.
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis | Year: 2015
The standard addition method with laser induced breakdown spectroscopy was used to analyze an unknown sample taken from a lead battery factory. the matrix influence on the results was effectively avoided when the external or internal standard method was used, and the pretreatment of samples was simple and quick. The Nd:YAG pulse laser with wavelength 1 064 nm was used as the excitation source. The echelle spectroscopy with high resolution and wide spectral range was used as the spectral separation device, and the intensified charge coupled device (ICCD) as the spectral detection device in the experiment. The characteristic line at 405.78 nm was chosen as the analysis line to measure Pb concentration. FeI: 404.58 line was chosen as the internal standard. Pre-experiment was carried out to confirm the appropriate condition. Under the laser energy of 128.5 mJ, the delay time of 2.5 μs, and the gate width of 3 μs, it was determined that with the addition of Pb to the sample in the range of 0 and 25 000 mg·kg-1, there wasn't self-absorption. There was a good linear relationship between the intensity of the spectral line of 405.78 nm and the addition of Pb. The appropriate concentration of Pb added into the sample for analysis was determined by this series of samples. On this basis, four samples were prepared with three parallel samples for each sample in order to verify the repeatability and reliability of the method, i. e. 5 000, 10 000, 15 000, 20 000 mg·kg-1 Pb was added into the original sample. The results were compared with the result of ICP-MS. The twelve samples' relative errors were between -24.6% and 17.6%. The average result was 43 069 mg·kg-1 with the relative error -2.44%. ©, 2015, Science Press. All right reserved.