Variation Trends of Dust Storms in Relation to Meteorological Conditions and Anthropogenic Impacts in the Northeast Edge of the Taklimakan Desert, China

To reveal the multivariate relationships between man-made and meteorological factors on dust storm frequency, the LUCC data, NDVI remote sensing data and meteorological data for the period of 1983-2013 were combined with dust storm frequency data, and the possible impacts of meteorological and anthropogenic factors on dust storm frequency were analyzed by using regression analysis and PCA (Principal Component Analysis). Results show that the inter-annual dust storm frequency increased gradually. In particular, an increasing trend in recent years, after 2009, is conspicuous. The monthly frequency of dust storms shows higher values between the months of February and May, with the highest mean number of events occurring in April, which accounts for 29% of the annual dust storm frequency. The annual dust storm frequency is positively correlated with wind speed and negatively correlated with precipitation;the monthly dust storm frequency is positively correlated with wind speed, but no significant correlation can be found with precipitation. The relationship between temperature and dust storms is not simply linear, however, a certain correlation with an unremarkable statistical significance can be found between them. Human activities also affect the dynamics of dust storms indirectly via changing vegetation coverage and direct dust emissions. The multivariate analysis further confirmed the association between dust storm frequency and meteorological factors and NDVI. The high loadings of dust storm frequency, wind speed, precipitation and NDVI on a PC indicate that the increased precipitation and NDVI will decrease dust storm frequency, and increased wind speed will increase dust storm frequency.

Polycyclic aromatic hydrocarbons from rural household biomass burning in a typical Chinese village

Biomass energy sources are still popular in the rural areas of developing countries for cooking and space heating. Since the incomplete combustion of agricultural residues in home-made ranges might lead to both outdoor and indoor air pollution and cause potential health threat to the rural population, we monitored the ambient levels of 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) at a typical rural site. Ambient particulate PAH samples (PM2.5 and PM10) were taken during both cooking and non-cooking periods. Source emission monitoring was also conducted for both improved and tra- ditional cooking stoves used in the area. Ambient PAHs had a significant increase during the cooking periods and varied from 72.1 to 554.4 ng/m3. The highest total PAH levels were found during the supper cooking time, in which five- and six-ring species accounted for a large proportion. The observed PAH levels during cooking periods at this rural site were even higher than those in urban areas. A good correlation was found between the benzo[a]pyrene level and the total PAH concentration (r=0.98), making benzo[a]pyrene a potential molecular marker for PAH pollution in the rural areas, where bio- mass burning is typical. The profiles of the particulate PAHs in both ambient air and source emissions showed a high proportion of high molecular-mass PAHs. In addition, emission factors of 16 PAHs from an improved household stove were found to be significantly lower than those from traditional stoves used in China and in other Asian countries.