چكيده به لاتين
The significant reduction in Hoor-Al-Azim area in recent years turns this water body into an active dust source in the Middle East. The results obtained from satellite observations indicate that Hoor-Al-Azim’s area dropped by 84 percent in 2000 compared with 1973, and it reaches its minimum area in recent years (606 km2). The results also indicate that the wetland area has slightly increased between 2000 and 2017 and recovered 29 percent of its previously dried part. In this study, the HYSPLIT model is driven by Re-analysis and GDAS data to calculate to potential transport routes of dust emanating from Al-Azim wetland. To this end, trajectories were calculated from 100 m a.g.l four times a day between 2000 and 2017. The air parcels density maps were computed in 6 different levels: 0-100 m a.g.l., 100-500 m a.g.l., 500-1000 m a.g.l., 1000-1500 m a.g.l., 1500-2000 m a.g.l., 2000-3000 m a.g.l., 3000-5000 m a.g.l. The results show that the transport routes of dust vary seasonally. The transport pattern of the wetland’s dust is similar in spring, autumn, and winter and it is different in summer. The dust is transported mainly toward northeast and southeast of Hoor-Al-Azim in spring, autumn, and winter, but active corridor in summer is northeast, southeast, and southwest routs. The results of source apportionment of Middle Eastern dust sources delineate that the Hoor-Al-Azim wetland and its adjacent sources contribute to 22 percent of dust sources occurred in Ahvaz in 2016 and 2017. The prediction results show that the Hoor-Al-Azim is highly active during autumn seasons, and in this season the accumulative PM10 in Shadegan may reach 11334 ug/m3. The influence of threshold friction velocity reduction also examined in this study. The results indicate that if the threshold friction velocity reduces 20 percent, the average PM10 concentration will augment 4, 6, 2 and 4.5 in the spring, summer, autumn, and winter, respectively. The investigation also reveals that if the Hoor-Al-Azim were dried completely in 2016, the total amount of deposited dust would be 1000 kton.
