Dust deposition and ambient PM.sub.10 concentration in northwest China: spatial and temporal variability

Eolian dust transport and deposition are important geophysical processes which influence global bio-geochemical cycles. Currently, reliable deposition data are scarce in central and east Asia. Located at the boundary of central and east Asia, Xinjiang Province of northwestern China has long played a strategic role in cultural and economic trade between Asia and Europe. In this paper, we investigated the spatial distribution and temporal variation in dust deposition and ambient PM.sub.10 (particulate matter in aerodynamic diameter  ≤  10 µm) concentration from 2000 to 2013 in Xinjiang Province. This variation was assessed using environmental monitoring records from 14 stations in the province. Over the 14 years, annual average dust deposition across stations in the province ranged from 255.7 to 421.4 t km.sup.-2 . Annual dust deposition was greater in southern Xinjiang (663.6 t km.sup.-2) than northern (147.8 t km.sup.-2) and eastern Xinjiang (194.9 t km.sup.-2). Annual average PM.sub.10 concentration across stations in the province varied from 100 to 196 µg m.sup.-3 and was 70, 115 and 239 µg m.sup.-3 in northern, eastern and southern Xinjiang, respectively. The highest annual dust deposition (1394.1 t km.sup.-2) and ambient PM.sub.10 concentration (352 µg m.sup.-3) were observed in Hotan, which is located in southern Xinjiang and at the southern boundary of the Taklamakan Desert. Dust deposition was more intense during the spring and summer than other seasons. PM.sub.10 was the main air pollutant that significantly influenced regional air quality. Annual average dust deposition increased logarithmically with ambient PM.sub.10 concentration (R.sup.2  ≥  0.81). While the annual average dust storm frequency remained unchanged from 2000 to 2013, there was a positive relationship between dust storm days and dust deposition and PM.sub.10 concentration across stations. This study suggests that sand storms are a major factor affecting the temporal variability and spatial distribution of dust deposition in northwest China.