Abstract. An empirical algorithm is developed for calculating bulk dry deposition velocity (V d ) of fine (PM 2.5 -particles having a diameter of ≤ 2.5 µm), coarse (PM 2.5−10 -particles having a diameter of 2.5-10 µm), and giant (PM 10+ -particles having a diameter of > 10 µm) atmospheric particles. The algorithm is developed from an empirical fit of V d data calculated using the size-resolved V d scheme of Zhang et al. (2001) with assumed lognormal size distributions of PM 2.5 , PM 2.5−10 and PM 10+ . In the new algorithm, the surface deposition velocity (V ds ) is parameterized as a simple linear function of friction velocity (u * ) for PM 2.5 and as a polynomial function of u * for both PM 2.5−10 and PM 10+ over all the 26 land use categories (LUCs). An adjustment factor as an exponential function of u * and leaf area index (LAI) is also applied to V ds of PM 2.5−10 and PM 10+ over 9 of the 26 LUCs that have variable LAI. Constant gravitational settling velocities are provided for PM 2.5 , PM 2.5−10 and PM 10+ . Aerodynamic resistance between a reference height and the surface can be calculated using available analytical formulas from the literature. The bulk V d of PM 2.5 , PM 2.5−10 and PM 10+ at the reference height can then be calculated by combining the gravitational settling velocity, aerodynamic resistance and the parameterized V ds . V d values calculated using the new algorithm are within ±20 % of those using the original size-resolved scheme for fine, coarse and giant particles. Uncertainties in V d values from the new algorithm due to the pre-assumed size distributions are on the order of 20 % for fine particles and on the order of a factor of 2.0 for coarse and giant particles. The new algorithm provides an alternative approach for calculating V d of bulk aerosol particles. V d of any particulate species can be simply estimated using this scheme as long as the mass fractions in fine, coarse and giant particles are known or can be assumed.

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Arbuscular mycorrhizal fungi (AMF) play an essential role in complex ecosystems. However, the species diversity and composition of AMF communities remain unclear in semi-arid mountains. Further, it is not well understood if the characteristics of AMF community assemblies differ for different habitat types, e.g., agricultural arable land, artificial forest land, natural grassland, and bush/wood land. Here, using the high-throughput technology by Illumina sequencing on the MiSeq platform, we explored the species diversity and composition of soil AMF communities among different habitat types in a semi-arid mountain (Taihang Mountain, Mid-western region of China). Then, we analyzed the effect of nutrient composition and soil texture on AMF community assembly. Our results showed that members of the Glomus genera were predominated in all soil types. The distance-based redundancy analysis indicated that the content of water, available phosphorus, and available potassium were the most crucial geochemical factors that significantly affected AMF communities (p < 0.05). The analysis of the soil texture confirmed that AMF diversity was negatively correlated with soil clay content. The comparison of AMF diversity among the various habitat types revealed that the artificial forest land had the lowest AMF diversity in comparison with other land types. Our findings suggest that there were differences in species diversity and composition of soil AMF communities among different habitat types. These findings shed new light on the characteristics of community structure and drivers of community assembly in AMF in semi-arid mountains, and point to the potential importance of different habitat types on AMF communities.

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