**10. Air quality index (AQI)**

In order to identify the impact of air pollution on human health, air pollution indices are commonly used, of which the AQI is the most well known [86-88]. As a consequence, the AQI is a powerful prenatainarry tool to ensure public health protection [86].

Changes of Permanent Lake Surfaces, and Their Consequences for Dust Aerosols and Air Quality: The Hamoun Lakes of the Sistan Area, Iran 183

reporting that on 273 days in 2001 the values were higher than those set for the air quality standards; 13% of the days were considered as very unhealthy and 0.27% were classified as dangerous. [52] found that 15 % of the days were unhealthy for sensitive people in the city of Zahedan thatwas affected by Sistan dust storms, while 2 % were associated with a high

Comparing the present results with those of the above-mentioned studies, it is concluded that the Sistan region experiences much higher PM concentration levels. Assessment of air quality in Zabol shows that 243 days out of 370 (65%) exhibit air pollution levels of above the air quality standards (>155 μg.m-3), a fraction that is much higher than that (26.5%) reported for Zahedan city located also in Sistan about 200 km south of Zabol [52]. The most significant finding is the 129 days (34.9%) that are characterized as hazardous (Table 4), which in combination with the adverse effects on human health, make it clear that environmental conditions in the Sistan region are rather poor for human well-being. On the other hand, only 5.7% of the days are associated with low pollution levels when the air quality is considered satisfactory and air pollution poses little or no risk. Several studies have shown that ambient air pollution is highly correlated with respiratory morbidity, mainly amongst children [94, 36, 95]. The results gathered from hospitals in the Sistan region showed that during dust storms respiratory patients increased significantly, especially those affected by chronic obstructive pulmonary disease and asthma. The percentage of these diseases increases in summer (June and July) [53]. Apart from the dust storms, re-suspended dust within the urban environment is a strong source of PM10 concentrations, while urban-anthropogenic and industrial activities are considered to have a much lower

The mean diurnal variation of PM10 concentrations for each season in Zabol indicates a clear pattern for all seasons except winter, with the maximum of the diurnal variation being observed in the middle of the day (~08:00-11 LST) while in winter PM10 values reach a maximum in the afternoon hours to early morning (~16:00 – 02:00 LST). In general, solar heating and vertical mixing of pollutants are the main factors for the reduction of PM10 levels at local noon to early afternoon hours. However, the maximum PM10 concentrations normally occur between 08:00 and 11:00 (LST) over Sistan. The diurnal PM10 variability in all seasons, except winter, is closely associated with the intensity of the wind speed measured at the Zabol meteorological station (see Fig. 16). This wind, being northerly in direction, carries large quantities of dust from the Hamoun dry lake bed. The mean diurnal wind speed variation is similar for all seasons; however, the wind favors the increase of aerosol load in summer and autumn (maximum PM10 for higher wind speeds). Note that the Hirmand River and some other ephemeral channels provide little water in winter and spring to the Hamoun lake beds. Therefore, in early summer, the Hamoun lakes are wet and at the end of summer and early autumn are always completely dried out. On the other hand, the Levar winds continue also in September and so high wind speeds cause huge

health risk or were even hazardous.

effect on the air pollution over Zabol.

dust storms.

The AQI is divided into six categories, varying from 0 to 500, with different health impacts [86] as listed in Table 4. The two first AQI categories (good and moderate, <155 PM10 μg.m−3) have no impact on health, while the last AQI category (hazardous, >424 PM10 μg.m−3) is associated with a serious risk of respiratory symptoms and aggravation of lung disease, such as asthma, for sensitive groups and with respiratory effects likely in the general population [89, 87]. The AQI for Zabol was calculated for the period September 2010 to July 2011.


**Table 4.** Health quality as determined by the Air Quality Index (AQI), PM10 and number of days with severe pollution in Zabol during the period September 2010 to July 2011.

Based on the technological rules related to AQI, the following formula was used to derive the PM10 concentration from AQI [90, 88]:

$$\text{I} = \frac{\text{I}\_{\text{high}} - \text{I}\_{\text{low}}}{\text{C}\_{\text{high}} - \text{C}\_{\text{low}}} (\text{C} - \text{C}\_{\text{low}}) + \text{I}\_{\text{low}}$$

Where I is the concentration of PM10, Ilow and Ihigh are AQI grading limited values that are lower and larger than I (AQI index), respectively, and Chigh and Clow denote the PM10 concentrations corresponding to Ihigh and Ilow, respectively.

Provisional studies focusing on air quality and dust over Iran have already been carried out. For example, amongst others, [91] performed a comparative study of air quality in Tehran during the period 1997 to 1998. The results revealed that in 1997 the air quality on 32% of the days was unhealthy, and on 5% of the days it could be regarded as very unhealthy, whereas in 1998 the unhealthy and very unhealthy days increased to 34% and 6%, respectively. [92] studied the air quality in Tehran and Isfahan and offered solutions for its improvement using the AQI. It was found that on 329 days of the year in Tehran, and on 34 of the days in Isfahan, the AQI departed beyond 100. [93] also studied AQI in Tehran reporting that on 273 days in 2001 the values were higher than those set for the air quality standards; 13% of the days were considered as very unhealthy and 0.27% were classified as dangerous. [52] found that 15 % of the days were unhealthy for sensitive people in the city of Zahedan thatwas affected by Sistan dust storms, while 2 % were associated with a high health risk or were even hazardous.

182 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics

In order to identify the impact of air pollution on human health, air pollution indices are commonly used, of which the AQI is the most well known [86-88]. As a consequence, the

The AQI is divided into six categories, varying from 0 to 500, with different health impacts [86] as listed in Table 4. The two first AQI categories (good and moderate, <155 PM10 μg.m−3) have no impact on health, while the last AQI category (hazardous, >424 PM10 μg.m−3) is associated with a serious risk of respiratory symptoms and aggravation of lung disease, such as asthma, for sensitive groups and with respiratory effects likely in the general population [89, 87]. The AQI for Zabol was calculated for the period September 2010 to

**Health Quality AQI PM10 (μg.m-3) Days (%) Good** 0-50 0-54 21 5.7 **Moderate** 51-100 55-154 106 28.6

**people** 101-150 155-254 66 17.8 **Unhealthy** 151-200 254-354 36 9.7 **Very unhealthy** 201-300 355-424 12 3.2 **Hazardous** 301-500 425< 129 34.9 **Table 4.** Health quality as determined by the Air Quality Index (AQI), PM10 and number of days with

Based on the technological rules related to AQI, the following formula was used to derive

high low <sup>I</sup> (C C ) I C C low low

Where I is the concentration of PM10, Ilow and Ihigh are AQI grading limited values that are lower and larger than I (AQI index), respectively, and Chigh and Clow denote the PM10

Provisional studies focusing on air quality and dust over Iran have already been carried out. For example, amongst others, [91] performed a comparative study of air quality in Tehran during the period 1997 to 1998. The results revealed that in 1997 the air quality on 32% of the days was unhealthy, and on 5% of the days it could be regarded as very unhealthy, whereas in 1998 the unhealthy and very unhealthy days increased to 34% and 6%, respectively. [92] studied the air quality in Tehran and Isfahan and offered solutions for its improvement using the AQI. It was found that on 329 days of the year in Tehran, and on 34 of the days in Isfahan, the AQI departed beyond 100. [93] also studied AQI in Tehran

severe pollution in Zabol during the period September 2010 to July 2011.

concentrations corresponding to Ihigh and Ilow, respectively.

I I

high low

AQI is a powerful prenatainarry tool to ensure public health protection [86].

**10. Air quality index (AQI)** 

July 2011.

**Unhealthy for sensitive** 

the PM10 concentration from AQI [90, 88]:

Comparing the present results with those of the above-mentioned studies, it is concluded that the Sistan region experiences much higher PM concentration levels. Assessment of air quality in Zabol shows that 243 days out of 370 (65%) exhibit air pollution levels of above the air quality standards (>155 μg.m-3), a fraction that is much higher than that (26.5%) reported for Zahedan city located also in Sistan about 200 km south of Zabol [52]. The most significant finding is the 129 days (34.9%) that are characterized as hazardous (Table 4), which in combination with the adverse effects on human health, make it clear that environmental conditions in the Sistan region are rather poor for human well-being. On the other hand, only 5.7% of the days are associated with low pollution levels when the air quality is considered satisfactory and air pollution poses little or no risk. Several studies have shown that ambient air pollution is highly correlated with respiratory morbidity, mainly amongst children [94, 36, 95]. The results gathered from hospitals in the Sistan region showed that during dust storms respiratory patients increased significantly, especially those affected by chronic obstructive pulmonary disease and asthma. The percentage of these diseases increases in summer (June and July) [53]. Apart from the dust storms, re-suspended dust within the urban environment is a strong source of PM10 concentrations, while urban-anthropogenic and industrial activities are considered to have a much lower effect on the air pollution over Zabol.

The mean diurnal variation of PM10 concentrations for each season in Zabol indicates a clear pattern for all seasons except winter, with the maximum of the diurnal variation being observed in the middle of the day (~08:00-11 LST) while in winter PM10 values reach a maximum in the afternoon hours to early morning (~16:00 – 02:00 LST). In general, solar heating and vertical mixing of pollutants are the main factors for the reduction of PM10 levels at local noon to early afternoon hours. However, the maximum PM10 concentrations normally occur between 08:00 and 11:00 (LST) over Sistan. The diurnal PM10 variability in all seasons, except winter, is closely associated with the intensity of the wind speed measured at the Zabol meteorological station (see Fig. 16). This wind, being northerly in direction, carries large quantities of dust from the Hamoun dry lake bed. The mean diurnal wind speed variation is similar for all seasons; however, the wind favors the increase of aerosol load in summer and autumn (maximum PM10 for higher wind speeds). Note that the Hirmand River and some other ephemeral channels provide little water in winter and spring to the Hamoun lake beds. Therefore, in early summer, the Hamoun lakes are wet and at the end of summer and early autumn are always completely dried out. On the other hand, the Levar winds continue also in September and so high wind speeds cause huge dust storms.

Changes of Permanent Lake Surfaces, and Their Consequences for Dust Aerosols and Air Quality: The Hamoun Lakes of the Sistan Area, Iran 185

mineralogical component over the site with average mass percentage of 22%, while micas (muscovite) contribute 13% and plagioclase (albite), 11%. The remaining components contribute much less to the dust mass, while chlorite (6.3%) is apparent in all dust samples for all days. The others, i.e. dolomite, enstatite, gypsum, halite, etc are present only in some samples with various percentages. It is quite interesting to note that quartz is much more

(a)

common over Sistan than the feldspars (plagioclase, microcline and orthoclase).

**Figure 17. a.** Mineralogical composition as obtained from XRD analysis for airborne dust samples

(b)

11/15/2009

1/7/2010

7/8/2010

23/8/2010

 Quartz Calcite Chlorite Dolomite Enstatite Hornblende Na-Ca Microcline Gypsum Halite Orthoclase Muscovite Plagioclase Albite Diopside

collected on different days in station A. **b.** Same as in Figure 17a, but for the station B.

9/5/2009

**Mass percentage (%)**

9/9/2009

9/16/2009

10/9/2009

11/7/2009

**Date**

**Figure 16.** Mean hourly variation of the PM10 (left panel) and wind speed (right panel) for each season in Zabol.

## **11. Mineralogical characteristics of dust**

In order to understand the influence of dust on the atmospheric environment, climatic system and health and to establish effective remedial policies and strategies, it is regarded as necessary to investigate the compositional (chemical and mineralogy) characteristics of airborne and soil dust over Sistan. To the best of our knowledge there are currently no published studies about the geochemical characteristics and dust mineralogy in this region. Moreover, nearby locations, Bagram and Khowst in Afghanistan, were selected for analyzing the mineralogical dust composition, major and trace elements within the framework of the Enhanced Particulate Matter Surveillance Program (EPMSP) campaign [44]. Furthermore, mineralogical and geochemical characteristics of dust were recently examined at Khuzestan province in southwestern Iran [72].

In this Chapter, an overview of the geological-geochemical characteristics of airborne and soil dust in the Sistan region is given for airborne and soil samples collected during the period August 2009 to August 2010. The chemical constituents during major dust storms over the region are analyzed at two locations (Fig. 2), also investigating the relationship between the chemical constituents of the dust storms and those of the inferred (Hamoun) source soils. The mineralogy percentage composition averaged at all heights for each day is shown in Fig. 17a, b for stations A and B, respectively. The chemical formulas of the main mineralogical components are given in [96], as well as the chemical reactions of dust with atmospheric constituents and trace gases during the dust life cycle. The mineralogical composition corresponds to screened samples with diameter <75 μm and can constitute an indication of both regional geology and wind transported dust that is deposited in local soils [44].

Emphasizing the dust mineralogy at station A, it is seen that the airborne dust is mainly composed of quartz, which is the dominant component (26-40%) for all the days of observations. Calcareous particles, mainly consisting of calcite, are the second dominant mineralogical component over the site with average mass percentage of 22%, while micas (muscovite) contribute 13% and plagioclase (albite), 11%. The remaining components contribute much less to the dust mass, while chlorite (6.3%) is apparent in all dust samples for all days. The others, i.e. dolomite, enstatite, gypsum, halite, etc are present only in some samples with various percentages. It is quite interesting to note that quartz is much more common over Sistan than the feldspars (plagioclase, microcline and orthoclase).

184 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics

 Summer Autumn Winter Spring

**11. Mineralogical characteristics of dust** 

**Hour (LST)**

0 2 4 6 8 10 12 14 16 18 20 22 24

examined at Khuzestan province in southwestern Iran [72].

in Zabol.

**PM10 (g / m3)**

**Figure 16.** Mean hourly variation of the PM10 (left panel) and wind speed (right panel) for each season

**Wind speed (m/s)**

0 2 4 6 8 10 12 14 16 18 20 22

 Summer Autumn Winter Spring annual

**Hour (LST)**

In order to understand the influence of dust on the atmospheric environment, climatic system and health and to establish effective remedial policies and strategies, it is regarded as necessary to investigate the compositional (chemical and mineralogy) characteristics of airborne and soil dust over Sistan. To the best of our knowledge there are currently no published studies about the geochemical characteristics and dust mineralogy in this region. Moreover, nearby locations, Bagram and Khowst in Afghanistan, were selected for analyzing the mineralogical dust composition, major and trace elements within the framework of the Enhanced Particulate Matter Surveillance Program (EPMSP) campaign [44]. Furthermore, mineralogical and geochemical characteristics of dust were recently

In this Chapter, an overview of the geological-geochemical characteristics of airborne and soil dust in the Sistan region is given for airborne and soil samples collected during the period August 2009 to August 2010. The chemical constituents during major dust storms over the region are analyzed at two locations (Fig. 2), also investigating the relationship between the chemical constituents of the dust storms and those of the inferred (Hamoun) source soils. The mineralogy percentage composition averaged at all heights for each day is shown in Fig. 17a, b for stations A and B, respectively. The chemical formulas of the main mineralogical components are given in [96], as well as the chemical reactions of dust with atmospheric constituents and trace gases during the dust life cycle. The mineralogical composition corresponds to screened samples with diameter <75 μm and can constitute an indication of

both regional geology and wind transported dust that is deposited in local soils [44].

Emphasizing the dust mineralogy at station A, it is seen that the airborne dust is mainly composed of quartz, which is the dominant component (26-40%) for all the days of observations. Calcareous particles, mainly consisting of calcite, are the second dominant

**Figure 17. a.** Mineralogical composition as obtained from XRD analysis for airborne dust samples collected on different days in station A. **b.** Same as in Figure 17a, but for the station B.

The mineralogical analysis for the 9-days recorded data at station B (Fig. 16b) shows more or less similar results to those obtained for station A and, therefore, any discussion will be given on their comparison (Fig. 19). The mineralogical composition has the same descending order as in station A, i.e. quartz (39.8±4.4%), calcite (18.8±3.5%), plagioclase (albite) (12.7±1.4%) and muscovite (10.1±3.2%). On the other hand, dust deposition may influence biogeochemical cycling in terrestrial ecosystems, while dust accumulation in soils can influence texture, element composition and acid neutralizing capacity [97-98]. Furthermore, the chemical and mineralogical composition of soil dust provides useful information about its provenance [99], radiative forcing implications [100] and human health effects [101]. For these reasons, in addition to the airborne dust samples, soil samples were collected at 16 locations around Sistan and Hamoun, at depths ranging from 0 to 5 cm from the soil crust. The results of soil sample mineralogy are summarized in Fig. 18. From an initial consideration of these results, it is established that the soil samples exhibit similar mineralogy to the airborne dust at both stations, thus suggesting similarity in sources for both airborne and soil dust. On the other hand, some soils in the Sistan region have been primarily formed from dust transported from the Hamoun lakes, presenting large similarities in mineralogy and chemical composition to airborne dust. However, atmospheric chemical reactions involving dust and aerosols of other types can alter the chemical characteristics of dust before its deposition [102]. Therefore, the mineralogy of the soil samples may differ significantly in comparison to the results obtained for airborne dust at stations A and B, since some of the soil samples (11 samples) were collected in the Hamoun dried lakes and others (five samples) around stations A and B.

Changes of Permanent Lake Surfaces, and Their Consequences for Dust Aerosols and Air Quality: The Hamoun Lakes of the Sistan Area, Iran 187

soil samples. The distance from the source region from whence dust is deposited also influences the particle size distribution, mineralogy and chemical composition of dust. Therefore, generally speaking, at local scales quartz clearly dominates with fractions up to ~50%, while as the distance from the dust source increases, feldspars (plagioclase, microcline) and phyllosilicate minerals (illite and kaolinite) present increased fractions [103, 42]. However, in our study the dust samples were all obtained within the same area and, therefore, are mineralogically similar. Nevertheless, station B, which is located closer to the Hamoun basin, the source of dust exposures, exhibits higher percentages of quartz, while station A (near to Zabol city) exhibits higher concentrations of calcite and muscovite compared to station B. On the other hand, the soil samples exhibit a lower mean percentage for quartz (27.7±4.7) and higher percentages for calcite, chlorite, halite and muscovite

compared to the airborne samples.

Quartz

0

deviation from the mean.

5

10

15

20

**Mass percentage (%)**

25

30

35

40

45

Calcite

Chlorite

Dolomite

Enstatite

Hornblende

Microcline

**Mineralogy components**

**Figure 19.** Average mineralogy components for airborne dust samples at stations A and B and for soil samples obtained at various locations in Hamoun Basin. The vertical bars express one standard

These mineralogical airborne dust and soil compositions, derived essentially from the Hamoun source region, reflect the composition of the material available from this provenance as well as the relevant grain size characteristics, enabling the wind storms to entrain this material into the lower atmosphere. While most of the minerals (quartz, feldspars of various types, muscovite) can easily be tied to basement-type lithology of generally gneissic-granitic character, others (chlorite, pyroxenes and hornblende) rather

Gypsum

 Station A Station B Soil samples

Halite

Orthoclase

Muscovite

Plagioclase

Diopside

**Figure 18.** Mineralogical composition as obtained from XRD analysis for soil samples collected at various locations in the Hamoun Basin.

Figure 19 summarizes the results from the mineralogical analysis of samples taken at the two stations and from the soil samples, allowing a quantitative comparison between them. The vertical bars correspond to one standard deviation from the mean for both airborne and soil samples. The distance from the source region from whence dust is deposited also influences the particle size distribution, mineralogy and chemical composition of dust. Therefore, generally speaking, at local scales quartz clearly dominates with fractions up to ~50%, while as the distance from the dust source increases, feldspars (plagioclase, microcline) and phyllosilicate minerals (illite and kaolinite) present increased fractions [103, 42]. However, in our study the dust samples were all obtained within the same area and, therefore, are mineralogically similar. Nevertheless, station B, which is located closer to the Hamoun basin, the source of dust exposures, exhibits higher percentages of quartz, while station A (near to Zabol city) exhibits higher concentrations of calcite and muscovite compared to station B. On the other hand, the soil samples exhibit a lower mean percentage for quartz (27.7±4.7) and higher percentages for calcite, chlorite, halite and muscovite compared to the airborne samples.

186 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics

Hamoun dried lakes and others (five samples) around stations A and B.

**Figure 18.** Mineralogical composition as obtained from XRD analysis for soil samples collected at

Figure 19 summarizes the results from the mineralogical analysis of samples taken at the two stations and from the soil samples, allowing a quantitative comparison between them. The vertical bars correspond to one standard deviation from the mean for both airborne and

various locations in the Hamoun Basin.

The mineralogical analysis for the 9-days recorded data at station B (Fig. 16b) shows more or less similar results to those obtained for station A and, therefore, any discussion will be given on their comparison (Fig. 19). The mineralogical composition has the same descending order as in station A, i.e. quartz (39.8±4.4%), calcite (18.8±3.5%), plagioclase (albite) (12.7±1.4%) and muscovite (10.1±3.2%). On the other hand, dust deposition may influence biogeochemical cycling in terrestrial ecosystems, while dust accumulation in soils can influence texture, element composition and acid neutralizing capacity [97-98]. Furthermore, the chemical and mineralogical composition of soil dust provides useful information about its provenance [99], radiative forcing implications [100] and human health effects [101]. For these reasons, in addition to the airborne dust samples, soil samples were collected at 16 locations around Sistan and Hamoun, at depths ranging from 0 to 5 cm from the soil crust. The results of soil sample mineralogy are summarized in Fig. 18. From an initial consideration of these results, it is established that the soil samples exhibit similar mineralogy to the airborne dust at both stations, thus suggesting similarity in sources for both airborne and soil dust. On the other hand, some soils in the Sistan region have been primarily formed from dust transported from the Hamoun lakes, presenting large similarities in mineralogy and chemical composition to airborne dust. However, atmospheric chemical reactions involving dust and aerosols of other types can alter the chemical characteristics of dust before its deposition [102]. Therefore, the mineralogy of the soil samples may differ significantly in comparison to the results obtained for airborne dust at stations A and B, since some of the soil samples (11 samples) were collected in the

**Figure 19.** Average mineralogy components for airborne dust samples at stations A and B and for soil samples obtained at various locations in Hamoun Basin. The vertical bars express one standard deviation from the mean.

These mineralogical airborne dust and soil compositions, derived essentially from the Hamoun source region, reflect the composition of the material available from this provenance as well as the relevant grain size characteristics, enabling the wind storms to entrain this material into the lower atmosphere. While most of the minerals (quartz, feldspars of various types, muscovite) can easily be tied to basement-type lithology of generally gneissic-granitic character, others (chlorite, pyroxenes and hornblende) rather

suggest mafic parent rocks, as can be inferred from basic mineralogical analysis [e.g.,104] . However, the calcite, dolomite, halite and gypsum suggest evaporate minerals, although both calcite and dolomite can also reflect alteration products of primary acid or mafic rock constituents. The inferred evaporate minerals reflect local derivation of salt from desiccating water bodies in the Hamoun lakes, originally formed from altered transported components via the Hirmand river system. Thus, the semi-quantitative mineral determinations for the airborne dust over the Sistan region support derivation of the particles from well weathered and well eroded (transported) argillaceous alluvium from the extensive Hirmand river system draining Afghanistan and terminating in the Hamoun Basin. The general geology of Afghanistan encompasses extensive terrains of both acidic and mafic rocks, while similar mineralogical composition of dust (i.e. dominance of quartz, but lower percentage of calcite) was found at the Bagram and Khowst sites located in eastern Afghanistan [44]. More specifically, they found that these sites are underlain by loess (wind deposited silt), sand, clay and alluvium containing gravel. As shown in Fig. 2, as well as in other studies [44, 51, 12], nearly the whole of Afghanistan is affected by the dust storms originating from Hamoun, since the dust plume usually follows a counter-clockwise direction, carrying wind-blown dust towards eastern Afghanistan. Similarly to our findings, the airborne dust at selected locations in southwestern Iran was found to be composed mainly from quartz and calcite, suggesting detritus sedimentary origin, followed by kaolinite and a minor percentage of gypsum [72]. Furthermore, [44] found that airborne dust samples derived from poorly drained rivers and lakes in central and southern Iraq contain substantial calcite (33– 48%), quartz and feldspar with minor chlorite and clay minerals. Previous studies [105- 106], have shown that silicate minerals (quartz, feldspars) and phyllosilicates (illite, kaolinite, smectite/montmorillonite clays, chlorite) dominate aeolian dust. Dust samples may also contain substantial amounts of carbonates, oxides, gypsum, halite and soluble salts, but the quantity and percentage of these minerals are quite variable from site to site.

Changes of Permanent Lake Surfaces, and Their Consequences for Dust Aerosols and Air Quality: The Hamoun Lakes of the Sistan Area, Iran 189

> SiO2 Cao Al2 O3 MgO Fe2 O3 Na2 O TiO2 P2 O5 MnO K2 O Tr. elem.

> > SiO2 CaO Al2 O3 MgO Fe2 O3 Na2 O TiO2 P2 O5 MnO K2 O Tr. elem.

**Figure 20. a.** Major elements (oxides) for airborne dust samples obtained on different days at Station A

(b)

11/15/2009

1/7/2010

7/8/2010

23/8/2010

11/7/2009

**Date**

(a)

7/11/2009

15/11/2009

7/1/2010

9/1/2010

23/01/2010

8/7/2010

23/08/2010

and Al2O3 (10.4-10.8%) contributions; a few percent of Na2O (4.2-5.4%), MgO (4.3%) and total iron as Fe2O3 (3.8-4.1%), as well as trace amounts (<1%) of TiO2, K2O, P2O5 and MnO, while the remaining major elements (Cr2O3, NiO, V2O5, ZrO2) were not detected by XRF analysis (Figs. 20a, b). When compared to various average shale analyses in the literature (Geosynclinal Average Shale and Platform Average Shale from [107] ; Average Shale from [108]; North American Shale Composite from [109], the Sistan dust is significantly depleted

analysed by means of XRF. **b.** Same as in Fig. 20a, but for the station B.

9/16/2009

10/9/2009

18/08/2009

9/5/2009

**Mass percentage** (%)

9/9/2009

**Mass percentage (%)**

25/08/2009

5/9/2009

9/9/2009

16/09/2009

25/09/2009

9/10/2009

16/10/2009

**Date**

## **12. Elemental composition of dust**

Knowledge of the chemical composition of airborne dust is necessary for clarifying the likely source regions and is important for quantitative climate modelling, in understanding possible effects on human health, precipitation, ocean biogeochemistry and weathering phenomena [50]. Chemical analysis of dust provides valuable information about potentially harmful trace elements such as lead, arsenic and heavy metals (Co, Cr, Cu, Ni, Pb). On the other hand, the major-element and ion-chemistry analyses provide estimates of mineral components, which themselves may be hazardous to human health and ecosystems and which can act as carriers of other toxic substances. The chemical analysis of dust samples at both stations was performed via XRF analysis for the major oxides (Figs. 20a, b).

In general, the analysis reveals that all samples at both stations contain major amounts of SiO2, mainly in the mineral quartz, variable amounts of CaO in the mineral calcite, plagioclase feldspar and to a limited extent in dolomite, as well as substantial Al2O3 concentrations. More specifically, average major elements of airborne dust at both stations indicate a predominant SiO2 mass component (46.8 – 47.8%) with significant CaO (12-12.2%)

**12. Elemental composition of dust** 

suggest mafic parent rocks, as can be inferred from basic mineralogical analysis [e.g.,104] . However, the calcite, dolomite, halite and gypsum suggest evaporate minerals, although both calcite and dolomite can also reflect alteration products of primary acid or mafic rock constituents. The inferred evaporate minerals reflect local derivation of salt from desiccating water bodies in the Hamoun lakes, originally formed from altered transported components via the Hirmand river system. Thus, the semi-quantitative mineral determinations for the airborne dust over the Sistan region support derivation of the particles from well weathered and well eroded (transported) argillaceous alluvium from the extensive Hirmand river system draining Afghanistan and terminating in the Hamoun Basin. The general geology of Afghanistan encompasses extensive terrains of both acidic and mafic rocks, while similar mineralogical composition of dust (i.e. dominance of quartz, but lower percentage of calcite) was found at the Bagram and Khowst sites located in eastern Afghanistan [44]. More specifically, they found that these sites are underlain by loess (wind deposited silt), sand, clay and alluvium containing gravel. As shown in Fig. 2, as well as in other studies [44, 51, 12], nearly the whole of Afghanistan is affected by the dust storms originating from Hamoun, since the dust plume usually follows a counter-clockwise direction, carrying wind-blown dust towards eastern Afghanistan. Similarly to our findings, the airborne dust at selected locations in southwestern Iran was found to be composed mainly from quartz and calcite, suggesting detritus sedimentary origin, followed by kaolinite and a minor percentage of gypsum [72]. Furthermore, [44] found that airborne dust samples derived from poorly drained rivers and lakes in central and southern Iraq contain substantial calcite (33– 48%), quartz and feldspar with minor chlorite and clay minerals. Previous studies [105- 106], have shown that silicate minerals (quartz, feldspars) and phyllosilicates (illite, kaolinite, smectite/montmorillonite clays, chlorite) dominate aeolian dust. Dust samples may also contain substantial amounts of carbonates, oxides, gypsum, halite and soluble salts, but the quantity and percentage of these minerals are quite variable from site to site.

Knowledge of the chemical composition of airborne dust is necessary for clarifying the likely source regions and is important for quantitative climate modelling, in understanding possible effects on human health, precipitation, ocean biogeochemistry and weathering phenomena [50]. Chemical analysis of dust provides valuable information about potentially harmful trace elements such as lead, arsenic and heavy metals (Co, Cr, Cu, Ni, Pb). On the other hand, the major-element and ion-chemistry analyses provide estimates of mineral components, which themselves may be hazardous to human health and ecosystems and which can act as carriers of other toxic substances. The chemical analysis of dust samples at

In general, the analysis reveals that all samples at both stations contain major amounts of SiO2, mainly in the mineral quartz, variable amounts of CaO in the mineral calcite, plagioclase feldspar and to a limited extent in dolomite, as well as substantial Al2O3 concentrations. More specifically, average major elements of airborne dust at both stations indicate a predominant SiO2 mass component (46.8 – 47.8%) with significant CaO (12-12.2%)

both stations was performed via XRF analysis for the major oxides (Figs. 20a, b).

**Figure 20. a.** Major elements (oxides) for airborne dust samples obtained on different days at Station A analysed by means of XRF. **b.** Same as in Fig. 20a, but for the station B.

and Al2O3 (10.4-10.8%) contributions; a few percent of Na2O (4.2-5.4%), MgO (4.3%) and total iron as Fe2O3 (3.8-4.1%), as well as trace amounts (<1%) of TiO2, K2O, P2O5 and MnO, while the remaining major elements (Cr2O3, NiO, V2O5, ZrO2) were not detected by XRF analysis (Figs. 20a, b). When compared to various average shale analyses in the literature (Geosynclinal Average Shale and Platform Average Shale from [107] ; Average Shale from [108]; North American Shale Composite from [109], the Sistan dust is significantly depleted

in SiO2, Al2O3, K2O and total Fe and significantly enriched in CaO, Na2O and MgO. The MgO is largely contained in dolomite and, to a lesser extent, in clay minerals such as palygorskite and montmorillonite [78, 44]. These components can be ascribed to the importance of evaporate minerals such as calcite, dolomite, halite and gypsum (as also suggested by the mineralogical analysis) inferred to have come from the desiccation taking place in the Hamoun dust source region. Furthermore, the elevated values for the trace elements Cl, F and S (Table 5) support the latter postulate as it would be expected from an evaporate-rich source for deflation of dust [e.g.,110]. Similar to the elemental composition of dust over Sistan, [44] determined a high fraction of SiO2 in silt, less CaO in calcite and slightly more Al2O3 in clay minerals at the Khowst site. At both Afghanistan sites (Bagram and Khowst), the SiO2 was dominant with fractions of about 50-55%, followed by Al2O3, CaO and MgO.

Changes of Permanent Lake Surfaces, and Their Consequences for Dust Aerosols and Air Quality: The Hamoun Lakes of the Sistan Area, Iran 191

**Figure 21.** Average X-ray fluorescence (XRF) results for major dust elements in stations A and B. Similar results obtained in Khuzestan Province, southwestern Iran [71-72] are also shown for

The Earth's crust is dominated by silicon and aluminum oxides. Numerous studies [78, 50 and references therein] reviewing the elemental composition of airborne dust over the globe report that mineral dust is composed of ~60% SiO2 and 10-15% Al2O3. The contribution of other oxides, i.e. Fe2O3 (~7%), MgO (~2.5%) and CaO (~4%), are, in general, more variable depending on source location. Furthermore, the review study of [96] showed that airborne dust samples collected over the globe have fairly small variations in elemental composition. The CaO concentrations over Sistan are found to be much higher than those (5.5%)

The average concentrations of trace elements (in ppm) in dust samples collected during major dust storms at stations A and B are summarized in Table 5, as obtained from XRF analysis. The results show that the dominant trace elements over Sistan are F and Cl, with the former being dominant in the vast majority of the dust events at station A. However, on two days (8/7/2010 and 23/8/2010) the Cl concentrations were extremely large, thus controlling the average value; there is a lack of observations at station B on 23/8/2010, thus the lower average Cl concentration. Note that on both these days, the SiO2 component is large, while MgO and Na2O are low (Fig. 20a). The dominance of chlorine indicates soil salinization in the Hamoun basin and along the Hirmand river and its tributaries. Furthermore, S exhibits higher concentration at station A, while for the other elements the concentrations between the two stations are more or less similar. The concentrations of potentially harmful and toxic elements, like Cs, Pb and As are, in general, low at both

On the other hand, the analysis of the major element ratios provides essential knowledge of the dust chemical composition and source region. The ratios of Si/Al at stations A and B are

stations; however, Ba, Cr and Zn present moderate concentrations.

comparison reasons.

summarized in [96].

**13. Trace elements** 

By comparing the major elements of different dust storms, some interesting relationships have been found. More specifically, on days (e.g. 15/11/2009, 7/1/2010, 23/1/2010) (Fig. 20a) when airborne dust was relatively depleted in SiO2, enhanced MgO and, particularly, Na2O values were recorded. Conversely, when SiO2 values were higher (e.g. 8/7/2010, 23/8/2010), both MgO and Na2O contributions dropped. This suggests that certain intense dust storms were richer in evaporate source material (i.e., elevated MgO and Na2O) coming from Hamoun dried lake beds, while others had more silica, reflecting weathered rock detritus from the Hirmand river and Afghanistan mountains. An explanation of these variable chemical compositions of dust samples is a real challenge, but it is postulated here that they may reflect local desiccation cycles and, possibly, even micro-climatic changes in the Hamoun-lakes dust source region. Excessive desiccation of the lakes would enhance potential evaporate minerals for deflation in drier periods, while in wetter periods, airborne dust would logically have been derived more from weathered fluvial detritus rich in SiO2.

Figure 21 summarizes the results of the elemental compositions determined by XRF analysis at both stations. For comparison reasons, the mean elemental composition found for several sites in southwestern Iran (Khuzestan province) [71-72] is also shown. The vertical bars express one standard deviation from the mean. Concerning the major elemental oxides over Sistan, both stations exhibit similar results, well within the standard deviations, suggesting that the transported dust over Sistan is locally or regionally produced with similarity in source region. In contrast, the mean elemental composition of airborne dust over Khuzestan province exhibits remarkable differences from that over Sistan, revealing various source regions and dust mineralogy. More specifically, the SiO2 percentage is significantly lower and highly variable over Khuzestan, which is also characterized by higher contributions of Na2O, MgO and K2O compared to Sistan. The dust storms over southwestern Iran may originate from local sources as well as being transported over medium- and long-ranges from different sources located in Iraq as well as in the Arabian Peninsula. A comparative study of the mineralogy and elemental composition of airborne dust at several locations in Iraq, Kuwait and the Arabian Peninsula [44] has shown significantly variable contributions, suggesting differences in overall geology, lithology and mineralogy of these regions. In further contrast, airborne dust over Sistan seems to have its individual characteristics originating from local and well-defined sources.

**Figure 21.** Average X-ray fluorescence (XRF) results for major dust elements in stations A and B. Similar results obtained in Khuzestan Province, southwestern Iran [71-72] are also shown for comparison reasons.

The Earth's crust is dominated by silicon and aluminum oxides. Numerous studies [78, 50 and references therein] reviewing the elemental composition of airborne dust over the globe report that mineral dust is composed of ~60% SiO2 and 10-15% Al2O3. The contribution of other oxides, i.e. Fe2O3 (~7%), MgO (~2.5%) and CaO (~4%), are, in general, more variable depending on source location. Furthermore, the review study of [96] showed that airborne dust samples collected over the globe have fairly small variations in elemental composition. The CaO concentrations over Sistan are found to be much higher than those (5.5%) summarized in [96].
