**4. Droughts in the Sistan**

168 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics

**Figure 3.** Geological map of the Sistan Basin and southern Afghanistan *[61-63].*

**Figure 4.** Position of the Hamoun Lakes in Iran and Afghanistan, showing a maximum inundation

period.

The Sistan Basin has recently experienced an unusually long 10-year drought starting in 2000 [10]. Combined with war and severe political disruption over the past 2 decades, the 10-year drought has created conditions of widespread famine that affected many people in eastern Iran and southwestern Afghanistan. A suggested, climatic forcing mechanism has been proposed for the recent drought by Barlow and others (2002). A prolonged ENSO (El Niño-Southern oscillation) cold phase (known as La Niña) from 1998 to 2001 and unusually warm ocean waters in the western Pacific appear to have contributed to the prolonged drought. The unusually warm waters (warm pool) resulted in positive precipitation anomalies in the Indian Ocean and negative anomalies over central Afghanistan [64], thus contributing to the drying of the Hamoun Basin. The contrast between a relatively wet year in 1976 and the nearly dry Hamoun lakes in 2001 is shown in Figs. 2 and 4. Millions of fish and untold numbers of wildlife and cattle died. Agricultural fields and approximately 100 villages were abandoned, and many succumbed to blowing sand and moving dunes [65].

Most of the Sistan population lives near the Hamoun lakes and is employed in agricultural, fishery, handicrafts and other jobs. To counter the effects of droughts, the Iranian government prepares facilities such as food and flour supplies, medicine and health services and employment in the region to prevent the forced emigration of people, but the continuous and extreme droughts have forced some people to leave the Sistan region. Long droughts at the end of the 1960s, middle of the 1980s, and from 1999 to 2010 affected the Sistan region significantly and resulted in desiccation of the Hamoun lakes, making the surrounding lands saline and disturbing their soil fertility, while some places became barren (see Fig. 5). The most important findings in Fig. 5 are: (1) in 1976, the Hamoun lakes were still thriving. Dense reed beds appear as dark green, while tamarisk thickets fringing the margins of the upper lakes show up as pink shades in the satellite images (Fig. 5). Bright green patches represent irrigated agricultural lands, mainly wheat and barley. The lakes flood to an average depth of half a meter, denoted by lighter shades of blue, while dark blue

**Figure 5.** Satellite (Landsat) images of the Hamoun Basin in spring of different years. Hamoun lakes are fed primarily by water catchments in neighbouring Afghanistan. In 1976, when rivers in Afghanistan were flowing regularly, the lake's water level was relatively high. Between 1999 and 2011, however, drought conditions caused frequent dryness of the Hamoun lakes that almost disappeared in 2001 after a 3-year intense drought period [65].

to black indicates deeper waters, which, however, do not exceed four meters. (2) By 2001, the Hamoun lakes had vanished since central and southwest Asia were hit by the largest persistent drought anywhere in the world. The only sign of water in this scorched landscape of extensive salt flats (white) is the Chah Nimeh reservoir in the southern part of Sistan (not shown on the satellite image), which is now only used for drinking water. Degraded reed stands in muddy soil are visible as dark green hues at the southern end of Hamoun-i Puzak. In 2003 the Hamoun Basin was covered with water again, but with significantly lower coverage than in the mid-1970s [65].

Changes of Permanent Lake Surfaces, and Their Consequences for Dust Aerosols and Air Quality: The Hamoun Lakes of the Sistan Area, Iran 171

investigate the chemical and mineralogical characteristics of dust, relevance of inferred

These samples were analyzed for major and trace elements and for minerals by applying X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) techniques, respectively. The samples were prepared for XRD analysis using a back loading preparation method. They were analyzed using a PANalytical X'Pert Pro powder diffractometer with X'Celerator detector and variable divergence and receiving slits with Fe filtered Co-Kα radiation. The phases were identified using X'Pert High score plus software. The relative phase amounts (weights %) were estimated using the Rietveld method (Autoquan Program). Mineral analysis by XRD is the single most important non-destructive technique for the characterization of minerals such as quartz, feldspars, calcite, dolomite, clay, silt and iron oxides in fine dust. Mineral phase analysis by XRD is one of the few techniques that are phase sensitive, rather than chemically sensitive, as is the case with XRF spectrometry. Quantitative mineralogical analyses using the XRD technique have been performed by a number of scientists over the

The sample preparation for XRF is made up of two methods, pressed powders and fusions. The former samples were prepared for trace element analyses and the latter for major

sources and contributions to air pollution.

1

m

12 cm

6 cm

2.5

Air Flow

Dust

Air Flow

Dust trap Dust trap

**Figure 6.** Schematic diagram of the dust sampler system.

globe [e.g., 68-70, 44, 71-72].
