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We conducted a comprehensive field campaign on exploring the optical characteristics of mineral dust in Dunhuang farmland nearby the Gobi deserts of northwest China during spring of 2012. The day-to-day and diurnal variations of dust aerosol showed prominent features throughout the experiment, primarily attributable to frequent dust events and local anthropogenic emissions. The overall average mass concentration of the particulate matter with an aerodynamic diameter less than 10 μm (PM10), light scattering coefficient (Σsp,670), absorption coefficient (Σap,670), and single-scattering albedo (SSA670) were 113±169 μgm-3, 53.3 ± 74.8 Mm-1, 3.2± 2.4 Mm-1, and 0.913 ± 0.05, which were comparable to the background levels in southern United States, but smaller than that in the eastern and other northwestern China. The anthropogenic dust produced by agricultural cultivations (e.g., land planning, plowing, and disking) exerted a significant superimposed effect on high dust concentrations in Dunhuang farmland prior to the growing season (i.e., from 1 April to 10 May). Strong south valley wind and vertical mixing in daytime scavenged the pollution and weak northeast mountain wind and stable inversion layer at night favorably accumulated the air pollutants near the surface. In the afternoon (13:00-18:00 LT), mean SSA670 was 0.945 ± 0.04 that was predominant by dust particles, whereas finer particles and lower SSA670 values (~ 0.90-0.92) were measured at night, suggesting the potential influence by the mixed dust-pollutants. During a typical biomass burning event on 4 April 2012, Σap,670 changed from ~ 2.0 Mm-1 to 4.75 Mm-1 and SSA670 changed from ~ 0.90 to ~ 0.83, implying remarkable modification of aerosol absorptive properties induced by human activities. The findings of this study would help to advance an in-depth understanding of the interaction among dust aerosol, atmospheric chemistry, and climate change in desert source region. [ABSTRACT FROM AUTHOR]

A survey was performed to collect 92 seasonal snow samples across northern China in January 2014. The results show that mixing ratios of black carbon (BC), organic carbon (OC), and anthropogenic dust (AD) range from 60 to 4200 ng g-1, 280 to 32 000 ng g-1, and 1300 to 5800 ng g-1 in surface snow, respectively. A relatively high correlation (R² = 0.87, n = 13) between OC and BC in surface snow is observed, indicating similar emission sources, and high OC/BC ratios suggest that biomass burning may be a major contributor at most snow sampling sites. In addition to the BC and AD parameters in the Snow, Ice, and Aerosol Radiation (SNICAR) model, the OC content in snow is considered an initial parameter for calculating snow albedo through a new radiative transfer model (Spectral Albedo Model for Dirty Snow, or SAMDS). The spectral albedo of snow reduction caused by OC (20 μg g-1) is up to a factor of 3 for a snow grain size of 800 μm compared to 100 μm. We find a larger difference in snow albedo levels between the model simulations and surface measurements for higher insoluble light-absorbing impurities (ILAPs) using the measured snow grain radii. However, using the optical effective radii (Reff), snow albedos modeled through both the SNICAR and SAMDS models are consistent with surface measurements, especially in the case of near-infrared wavelengths. [ABSTRACT FROM AUTHOR]