An Investigation into the Processes and Quantity of Dust Emissions over Gravel and Sand Deserts in North-Western China

Abstract

Year-long field observations have shown that there are spatial and temporal variations in the quantity of dust emissions for particulate matter ${<}$10 $\upmu \hbox {m}$ (PM10), particulate matter ${<}$63 $\upmu \hbox {m}$ (PM63) and vertical dust flux over different gravel surfaces (with loose sand, without loose sand, with a crust, and without a crust), with the greatest emissions occurring in the spring. The largest quantity of PM10 and PM63 emissions occurred over gravel with a loose sand surface ($1.1 \times 10^{-3}$ and $10.2 \times 10^{-3 }\hbox { kg m}^{-1}\hbox { day}^{-1}$, respectively). The gravel surface without loose sand and without a crust presents the lowest values of PM63 ($1.6 \times 10^{-3 }\hbox { kg m}^{-1}\hbox { day}^{-1}$) and PM10 ($3.3 \times 10^{-4}\hbox { kg m}^{-1}\hbox { day}^{-1}$). However, the vertical dust flux was largest at over sandy surface ($373 \times 10^{-3 }\hbox { kg m}^{-2}\hbox { day}^{-1}$). Multivariate correlation analysis indicates that the quantity of PM10 is strongly negatively correlated to gravel coverage ($R^{2 }= 0.55$). The quantity of PM10 dust emissions over a gravel surface with loose sand is approximately three times greater than that of a gravel surface with a crust. The mean quantity of PM10, PM63 and vertical dust flux over a gravel surface decreased with increasing gravel coverage. By comparing the quantity of PM10 dust emissions over gravel and sandy deserts, we found that gravel deserts and sandy deserts are both major sources of dust for dust storms in this region.