To investigate the chemical composition, size distribution, and mixing state of aerosol particles on heavy pollution days, single-particle aerosol mass spectrometry was conducted during 9–26 October 2015 in Xi’an, China. The measured particles were classified into six major categories: biomass burning (BB) particles, K-secondary particles, elemental carbon (EC)–related particles, metal-containing particles, dust, and organic carbon (OC) particles. BB and EC-related particles were the dominant types during the study period and mainly originated from biomass burning, vehicle emissions, and coal combustion. According to the ambient air quality index, two typical episodes were defined: clean days (CDs) and polluted days (PDs). Accumulation of BB particles and EC-related particles was the main reason for the pollution in Xi’an. Most types of particle size were larger on PDs than CDs. Each particle type was mixed with secondary species to different degrees on CDs and PDs, indicating that atmospheric aging occurred. The mixing state results demonstrated that the primary tracers were oxidized or vanished and that the amount of secondary species was increased on PDs. This study provides valuable information and a dataset to help control air pollution in the urban areas of Xi’an.
Current methods for testing the electricity generation capacity of isolates are time- and labor-consuming. This paper presents
a rapid voltage testing system of exoelectrogenic bacteria called Quickscreen, which is based on a microliter microbial fuel
cell (MFC). Geobacter sulfurreducens and Shewanella baltica were used as the model exoelectrogenic bacteria; Escherichia coli that cannot generate electricity was used as a negative control. It was found that the electricity generation capacity of
the isolates could be determined within about five hours by using Quickscreen, and that its time was relatively rapid compared
with the time needed by using larger MFCs. A parallel, stable, and low background voltage was achieved using titanium as a
current collector in the blank run. The external resistance had little impact on the blank run during the initial period.
The cathode with a five-hole configuration, used to hydrate the carbon cathode, gave higher cathode potential than that with
a one-hole configuration. Steady discharge and current interrupt methods showed that the anode mostly contributed to the large
internal resistance of the Quickscreen system. However, the addition of graphite felt decreased the resistance from 18 to
5 kΩ. This device was proved to be useful to rapidly evaluate the electricity generation capacity of different bacteria. 相似文献