Hourly measurements of water-soluble inorganic ionic species in ambient atmospheric particles were conducted at Shanghai, Hangzhou, and Guangzhou sampling sites in China during the period of 2009-2011. The relation between sulfate and nitrate in particulate matter (PM 10 and PM 2.5 ) was examined based on these measurements. Results showed that the mass fraction of sulfate was strongly negatively correlated with that of nitrate in atmospheric particles on most of the sampling days, especially when sulfate and nitrate made up the vast majority of the total soluble anions and cations (Na + , K + , Ca 2+ , and Mg 2+ ) made a small contribution to the total water-soluble ions, revealing that the formation mechanisms of sulfate and nitrate in the atmosphere are highly correlated, and there exists a significant negative correlation trend between sulfate and nitrate mass fractions in the atmospheric particles. We found that local meteorological conditions presented opposite influences on the mass fractions of sulfate and nitrate. Further analysis indicated that the two mass fractions were modulated by the neutralizing level of atmospheric aerosols, and the negative correlation could be found in acidic atmospheric particles. Strong negative correlation was usually observed on clear days, hazy days, foggy days, and respirable particulate air pollution days, whereas poor negative correlation was often observed during cloud, rain, snow, dust storm, and suspended dust events. The results can help to better understand the formation mechanisms of atmospheric sulfate and nitrate during air pollution episodes and to better explain field results of atmospheric chemistry concerning sulfate and nitrate.
The potential impacts of agricultural fires (agri-fires) on regional air quality over China were examined using active fire products derived from satellite remote sensing and air mass trajectory modeling from 2009 to 2010. Agri-fires were found in most administrative areas. More than 80% of the agri-fires were in the heartlands of agricultural regions such as Anhui, Jiangsu, Shandong and Henan Provinces. Agri-fires had a seasonal pattern, with two distinct peaks in summer and autumn harvest periods, especially in June (61-86%) and October (5-14%). Agri-fire smoke was transported in the atmosphere on a continental scale in three directions, moving northeasterly, northwesterly and southwesterly away from source areas. Particles from agri-fire smoke contributed more than 35% of aerosol optical depth (AOD) over regions of the Jiaodong Peninsular, the North Plain, East China and other areas, and exceeded 60% in some areas of Shandong, Henan and Jiangsu Provinces. In the boundary layer atmosphere, particles from agri-fire smoke contributed more than 29% of PM 10 in parts of Anhui, Jiangsu and Shandong Provinces. Due to agri-fires the amount of PM 10 was highly correlated (R 2 = 0.6) with the smoke air masses in the main potential sink regions, and the mean PM 10 during the summer harvest of 2010 reached 0.24 mg/m 3 , far higher than the adjacent periods without smoke.
The sol-gel method is used to fabricate Fe crystalline powders coated with SiO 2 . By controlling the molar ratio R of diluted water to tetraethoxysilane (TEOS), Fe powders coated with SiO 2 with different morphological characteristics are fabricated. The influence of the core diameter on electromagnetic parameters is investigated. The effect of the amount of the coating material SiO 2 on electromagnetic parameters is given. Radar wave absorbing properties of Fe coated with SiO 2 and TiO 2 respectively are compared.
The model for the effective electromagnetic coefficients is established. The influence of the volume ratio of the outer layer and the inner on the absorption and the characteristic impedance is discussed. The microstructure of the coated absorbent is designed. Sol-gel method is used to prepare the coated radar absorbent. It is shown by the theoretical and experimental results that the absorbing ability of the coated magnetic absorbent has be improved greatly, and the absorbing band below -8 dB is about 9 GHz.
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