Characteristics of dust deposited along a transect between central Iran and
theZagros Mountains
abstract
Few studies have been reported on the characteristics of dust particles
deposited in arid regions of the Middle East. The objective of this study was
to identify the variations in physical, chemical, and mineralogical
composition of dust particles deposited along an elevational transect lying
between central Iran and the Zagros Mountains in the west. Dust samples
were collected at 12 localities during September 2008 and July 2009 with
and without transboundary dust storms, respectively. Samples were
examined for their grain size distribution, and their mineralogical and
chemical composition. Surface soils were also sampled from the vicinity of
the dust sampling sites and their total elemental compositions were
determined. The results indicated that dust deposition rate, mean particle
diameter, and concentration of soluble ions in samples from both sampling
periods decreased with altitude, with a significantly lower gradient for
samples of July 2009 than for those of September 2008. The similarity
observed in dust samples taken during September 2008 and those reported
by previous studies or measured in local soils and sediments suggests that
local soils greatlycontribute to the atmospheric dust along the transect in
periods with no dust storms. During such periods,dust deposits in the high
altitude Zagros Mountains, where annual precipitation is higher and
temperature lower, only receive a minor contribution from arid soils of
central Iran. However, in July 2009, when aheavy dust storm took place,
significant differences were observed between local soils and dust samples
along the transect, particularly at high altitudes, in terms of their
physicochemical and mineralogical characteristics.
These findings, together with satellite images and patterns of wind frequency
and direction, clearlyindicate the major contribution of a transboundary dust
storm, probably originating from Iraqi aridland, to atmospheric deposition in
the Zagros area and central Iran. When dust storms blow from across the
borders,the contribution of local soils and sediments to aerosols drastically
decreaseswithelevation. If dust stormsoriginating from outside the country
continue to occur, not only will they influence the surface soil properties in
the Zagros region but will also induce environmental problems in the region.
Keywords:
Particle size distribution Palygorskite Mineralogy Dust