Guangli Xiu

Simultaneous monitoring and compositions analysis of PM1 and PM2.5 in Shanghai: Implications for characterization of haze pollution and source apportionment.

A year-long simultaneous observation of PM1 and PM2.5 were conducted at ECUST campus in Shanghai, the compositions were analyzed and compared. Results showed that PM2.5 was dominated by PM1 on clear days while the contribution of PM1-2.5 to PM2.5 increased on haze days, indicating that PM2.5 should be given priority to characterize or predict haze pollution. On haze days, accumulation of organic carbon (OC), elemental carbon (EC) and primary organic carbon (POC) in PM1-2.5 was faster than that in PM1. Humic-like substances carbon (Hulis-C) in both PM2.5 and PM1 formed faster than water soluble organic carbon (WSOC) on haze days, hence Hulis-C/WSOC increased with the intensification of haze pollution. In terms of water soluble ions, NO3(-)/SO4(2-) in PM1 increased with the aggravation of haze pollution, implying that mobile sources dominated on haze days, so is nitrogen oxidation ratio (NOR). Liquid water content (LWC) in both PM1 and PM2.5 had positive correlations with relative humidity (RH) but negative correlations with visibility, implying that hygroscopic growth might be a factor for visibility impairment, especially LWC in PM1. By comparison with multi-linear equations of LWC in PM1 and PM2.5, NO3(-) exerted a higher influence on hygroscopicity of PM1 than PM2.5, while RH, WSOC, SO4(2-) and NH4(+) had higher effects on PM2.5, especially WSOC. Source apportionment of PM2.5 was also investigated to provide reference for policy making. Cluster analysis by HYSPLIT (HYbrid Single Particle Lagrangian Integrated Trajectory) model showed that PM2.5 originated from marine aerosols, middle-scale transportation and large-scale transportation. Furthermore, PM2.5 on haze days was dominated by middle-scale transportation. In line with source apportionment by positive matrix factorization (PMF) model, PM2.5 was attributed to secondary inorganics, aged sea salt, combustion emissions, hygroscopic growth and secondary organics. Secondary formation was the principle source of PM2.5. Furthermore, the contribution of combustion emissions to PM2.5 increased with the intensification of haze pollution, which was just opposite to hygroscopic growth, while that of secondary formation kept quite stable on clear days and haze days.

Temporal Variations and Source Apportionment of Hulis-C in PM2.5 in Urban Shanghai

Humic-like substances (Hulis), the hydrophobic part of water-soluble organic compounds, have been recognized to play important roles in environmental behavior of PM2.5 in atmosphere. In this study, Hulis and other components of PM2.5, collected in urban Shanghai from September 2013 to August 2014 were analyzed. The annual average concentration of Hulis carbon (Hulis-C) was (2.61±2.58) μg/m(3), accounting for about 50% of water-soluble organic carbon (WSOC). The monthly average Hulis-C concentration peaked in December while the lowest was in summer, coinciding with the high and low of levoglucosan and secondary inorganic aerosol (SIA). Biomass burning and secondary formation were both important sources of Hulis-C, and their contributions showed obvious seasonality. In late autumn and winter, the strong inter-correlations among Hulis-C concentrations, NO3(-)/SO4(2-) mass ratios and nitrogen oxidation ratios (NOR) were found, suggesting the atmospheric oxidation of NOx to nitrate and related gas-phase reactions may be inter-linked with Hulis-C formation. In summer, photochemical reaction was clearly the major source of Hulis-C. The investigation by backward trajectory analysis showed that the long-range transport from the Northwest brought large amounts of PM2.5 and enhanced Hulis-C and levoglucosan level, indicating biomass burning as a significant source of Hulis-C under this type of synoptic weather conditions. In comparison, Hulis formation associated with the NOx oxidation pathway was mainly associated with the short-range transport from the neighboring cities. Marine aerosol was relatively clean and had little effects on Hulis-C. The CWT (concentration weighted trajectory) model results suggested that the Yangtze River Delta (YRD) region was an important source region of Hulis-C, while the effect of some northwestern areas was not negligible.

An Ultrasensitive Plasmonic Nanosensor for Aldehydes

Glucose is the most common but important aldehyde, and it is necessary to create biosensors with high sensitivity and anti-interference to detect it. Under the existence of silver ions and aldehyde compounds, single gold nanoparticles and freshly formed silver atoms could respectively act as core and shell, which finally form a core-shell structure. By observing the reaction between glucose and Tollens reagent, metallic silver was found to be reduced on the surface of gold nanoparticles and formed Au@Ag nanoparticles that lead to a direct wavelength shift. Based on this principle and combined with in situ plasmon resonance scattering spectra, a plasmonic nanosensor was successfully applied in identifying aldehyde compounds with excellent sensitivity and specificity. This ultrasensitive sensor was successfully further utilized to detect blood glucose in mice serum samples, exhibiting good anti-interference ability and great promise for future clinical application.

Secondary ion mass spectrometry: The application in the analysis of atmospheric particulate matter

Currently, considerable attention has been paid to atmospheric particulate matter (PM) investigation due to its importance in human health and global climate change. Surface characterization, single particle analysis and depth profiling of PM is important for a better understanding of its formation processes and predicting its impact on the environment and human being. Secondary ion mass spectrometry (SIMS) is a surface technique with high surface sensitivity, high spatial resolution chemical imaging and unique depth profiling capabilities. Recent research shows that SIMS has great potential in analyzing both surface and bulk chemical information of PM. In this review, we give a brief introduction of SIMS working principle and survey recent applications of SIMS in PM characterization. Particularly, analyses from different types of PM sources by various SIMS techniques were discussed concerning their advantages and limitations. The future development and needs of SIMS in atmospheric aerosol measurement are proposed with a perspective in broader environmental sciences.