Brown carbon (BrC) has recently received much attention because of its light absorption features. The chemical compositions, optical properties, and sources of fine aerosol at a high-elevation mountain observatory (4730 m a.s.l.) in the central Tibetan Plateau were measured between 31 May and 1 July 2015. A low flow-rate sampler was used to collect 24-h average fine particulate matter (PM) filter samples. Water-soluble ions, organic carbon (OC), elemental carbon, water-soluble organic carbon (WSOC), and light absorption by water-soluble BrC were determined for 26 filter samples. The mean (± 1σ) OC and WSOC concentrations were 0.76 ± 0.43 and 0.39 ± 0.15 μgC/m, respectively, and the mean WSOC/OC mass ratio was 0.59 ± 0.22. The OC and WSOC concentrations were relatively higher (0.59-1.80 and 0.33-0.83 μgC/m, respectively) during the pre-monsoon period (2-13 June) and were relatively lower (0.27-0.77 and 0.12-0.50 μgC/m, respectively) during the monsoon period (14 June to 1 July), probably because of wet scavenging of aerosols during long-range transport and the presence of cleaner marine air masses during the monsoon period. The absorption spectra of PM water extracts smoothly increase from visible range to ultraviolet range. The absorption Ångström exponent, which describes the wavelength dependence of water-soluble BrC, was 2.74-10.61 (mean 6.19 ± 1.70), and its value was similar in the pre-monsoon period (6.57 ± 0.56) to that in the monsoon period (5.91 ± 2.14). The water-soluble BrC mass absorption efficiency, 0.38 ± 0.16 m/(g C), was much lower than those observed in most urban areas but similar to those in other remote sites. Absorption coefficient at 365 nm, typically used as a proxy for water-soluble BrC, correlated well with the WSOC concentration (R = 0.57), K concentration (R = 0.75), and organic aerosol biomass burning markers characterized by an Aerodyne aerosol mass spectrometer (CHO + CHO, R = 0.60). It can be inferred that biomass burning was an important source of water-soluble BrC in the study area combined with air mass back trajectory analysis using the NOAA HYSPLIT as well as MODIS data of fire dots and aerosol optical depths. The water-soluble BrC to BC light absorption (at 365 nm) coefficient ratios were 9-27%.
BiOI nanolamellas and BiSI nanowires were synthesized using Bi(NO3)3·5H2O, (NH2)2CS and I2 as reactants in the solvothermal process with ethanol as the system media. The as-prepared samples were characterized by X-ray powder diffraction (XRD), scanning electronic microscopy (SEM), Energy-Dispersive X-ray Spectrometer (EDS). The competitive growth of BiOI and BiSI were investigated by changing the quantity of (NH2)2CS. A possible reaction mechanism was proposed.
Saline soil is widely distributed in Jilin seasonally frozen zone. Many engineering hazards are associated closely related to moisture migration with freezing-thawing cycles. Soil salinization in the region is mainly due to migration of soil moisture and salinity caused by the temperature gradient with soil freezing process in this area. Adopt self-developed experiment instrument for measuring the freezing experiments of saline soil in Sanzhigou. Constract and analyze the transformation of moisture content and soluble salt before and after the freeze, and quantify the moisture and salinity substance migration in the freezing process.
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