Dust Emission from Gobi under Different Dust Content Conditions: A Wind Tunnel Study atop the Mogao Grottoes

Dust emission from the Gobi desert is one of the major sources of global atmospheric aerosols. However, the main factors affecting dust emission from Gobi remain poorly understood. In this paper, field wind tunnel experiments were performed atop the Mogao Grottoes to determine the variation characteristics of the vertical dust flux (F) of particulate matter less than 10 μm (PM10) for Gobi surfaces with different dust content and wind speeds under external sand supply. The results demonstrate that F obeyed a power function with increasing friction velocity (U∗), and increased exponentially with the increasing surface dust content (C). The index of n-value in the formula F∝U∗n is taken in the range of 2.02–2.63 under the surface of 27.3–47.3% dust content (<100 µm), and the dust emission rate was significantly enhanced when the surface dust content exceeded approximately 37%. This study indicates that wind force is the primary dynamic condition affecting Gobi dust emission, and that surface dust content is a significant factor in determining the quantity of dust emission. Furthermore, the contribution of wind force to PM10 emission is greater than the surface dust content, and the higher the height, the greater the weight of friction velocity.

The relationship between indoor environment, outdoor environment, and behavior on indoor air quality and health

We should be concerned about the impact of indoor air quality on health because in the United States, people spend most of their time indoors. While earlier studies have characterized the odds of developing illness based on the home environment, they have not investigated the behaviors that can ameliorate the negative effect of indoor, outdoor, and behavioral sources. The purpose of this study was to 1) investigate the contributions of indoor, outdoor, and behavioral sources of pollutants on health symptoms, and 2) to identify the behaviors that can worsen or mitigate the number of health symptoms. Data came from two surveys (n=83,284) and include questions on home conditions, outdoor conditions, occupants’ behaviors, and health symptoms. I used negative binomial regression and identified that demographics and outdoor characteristics explain 2% of the variability in health symptoms, and maintenance behaviors explain 8% of the variability in health symptoms. Next, structural equation modeling (SEM) was used to examine the behaviors that can mitigate or worsen the number of health symptoms. The results show that maintenance issue such as mold result in significantly more health symptoms (β = .12, p &lt;.001). and factors such as leaks, and frequent long shower may result in an increase in mold. Leaks may cause water stains (β = .39, p &lt;.001) which could lead to molds (β = .47, p &lt;.001). While frequent long shower can result in an increase in mold (β = .05, p &lt;.001), the use of a bathroom exhaust during shower may help to reduce molds (β = -.04, p &lt;.001). In terms of personal behaviors, the presence of carpet (β = .08, p &lt;.001), and smoking also result in an increase in surface dust (β = .17`, p &lt;.001) but frequent vacuuming could mitigate the impact of surface dust on health symptoms (β = -.12, p &lt;.001). Home occupants who live near environmental hazards are also likely to use air purifier (β = .03, p &lt;.001); however, air purifier is associated with more health symptoms (β = .05, p &lt;.001). Based on the findings, it is recommended that home occupants engage in periodic maintenance to prevent issues such as leaks from escalating to molds, regular vacuuming to reduce the accumulation of surface dust. Regarding air purifier, it could be that participants who experienced more health symptoms were more likely to use an air purifier. However, some air purifiers are sources of ozone, therefore home occupants should err on the side of caution when it comes to air purifier (Britigan et al., 2006; Cestonaro et al., 2017).