تحلیل زمانی و مکانی غبارآلودگی ناشی از رخدادهای فرسایش بادی در استان فارس

فرسایش بادی یکی از مهم ترین عوامل تخریب زمین در مناطق خشک و نیمه خشک جهان است که آلودگی ناشی از آن، اثرات نامطلوبی را بر کیفیت هوای این مناطق برجاگذاشته است. بنابراین، بررسی مداوم این پدیده و کشف روند تغییرات آن می ‌تواند گامی موثر در جهت کاهش خطرات زیست محیطی رخدادهای فرسایش بادی و توفان ‌های گردوغبار باشد. هدف اصلی این مطالعه، تحلیل روند تغییرات زمانی و مکانی آلودگی ناشی از این رخدادها در استان فارس است. بدین منظور، برای محاسبه شاخص آلودگی توفان گردوغبار (pdsi) از داده ‌های ساعتی مربوط به کد رخدادهای گردوغبار و دید افقی سال های 1379 تا 1397 استفاده شد. روند تغییرات زمانی pdsi، با استفاده از آزمون من کندال و الگوی پراکنش مکانی غبارآلودگی هوا، با استفاده از نقشه ‌های تهیه شده از روش وزن ‌دهی فاصله معکوس تحلیل شد. نتایج نشان داد که مقدار متوسط غبارآلودگی هوا در دوره مطالعاتی برای ایستگاه های آباده، اقلید، ایزدخواست، داراب، درودزن، زرقان، شیراز، فسا، لار، لامرد و نیریز به ترتیب 46.8، 15.1، 17، 133.2، 12.9، 49.3، 217.5، 266.6، 171.9 و 140.9 بوده ‌است. بر اساس آماره منکندال، روند تغییرات افزایشی معنی دار (1.96+z) اغلب در مهرماه مشاهده شد. روند تغییرات فصلی و سالانه آلودگی ناشی از توفان ‌های گردوغبار در بیش از 70 % ایستگاه ‌های مطالعاتی، افزایشی بود. همچنین نتایج نشان داد که ایستگاه ‌های داراب و لار، روند تغییرات کاهشی معنی ‌داری را در سال ‌های اخیر تجربه کرده‌ اند. از نظر مکانی، بیشترین الگوی توزیع ذرات گردوغبار در نواحی مرکزی، جنوب غربی و جنوب شرقی استان فارس (120

Temporal and spatial analysis of dust pollution caused by wind erosion events in Fars province

Extended abstract1 IntroductionOne of the environmental crises that have caused a lot of concern in recent years is the pollution caused by wind erosion in arid and semiarid regions, especially in Iran. Recently, it has been reported that about 26% of changes in atmospheric dust concentrations occurred due to changes in the drought index resulting from changes in precipitation to evapotranspiration. Increasing air pollutants concentrations, especially dust particles, had negative effects on agricultural production, human health, and the environment. Therefore, temporal and spatial analysis and continuous monitoring of these events in different regions, especially in arid and semiarid regions, are of great importance. Accordingly, the main purpose of this study is to analyze the trend of dust pollution caused by wind erosion at different time scales and to investigate the spatial distribution of dust particles in Fars province, southwestern Iran, during the years 2000 to 2018.2 MethodologyIn this study, using the pollution of dust storm index (PDSI), the pollution caused by wind erosion events in eleven synoptic stations located in Fars province was calculated. The frequency of local, moderate, and severe dust events was used to calculate this index. Then, the MannKendall test was used to analyze the trend of monthly, seasonal, and annual changes. The trend of changes was calculated separately for the study stations. Furthermore, the map of spatial changes of air pollution in Fars province from 2000 to 2018 was prepared using the reverse distance weighting method. Finally, areas more sensitive to wind erosion were identified based on the generated maps using this method.3 Results Analyzing the trend of monthly changes in PDSI using the MannKendall test showed that the most incremental and significant changes in dust pollution occurred in April, May, and February in Fasa, Shiraz, Dorodzan, and Zarghan stations. Meanwhile, the trend of decreasing and significant changes in PDSI has occurred mainly in Lar and Darab stations and from May to October. The results of the seasonal change trend showed that regardless of the confidence level, more than 70% of the study stations have experienced an upward trend in spring, summer, and autumn. In winter, all stations except Darab station have experienced increasing changes in air pollution. On an annual scale, the trend of decreasing changes was observed only in Darab and Lar stations, while the trend of changes in other stations of Fars province was increasing. The pattern of the spatial distribution of dust particles in Fars province showed that in 2003 and 2005, more than twothirds of Fars province and mainly the central to southeast areas were faced with high dust concentrations. In recent years, and especially in 2017 and 2018, the distribution of dust particles has changed. In recent years, residents of the central to southwestern Fars province have suffered more from reduced air quality due to increased concentrations of atmospheric dust particles.4 Discussion ConclusionsThe growing trend of dust pollution caused by wind erosion events in recent decades has raised major concerns at various regional, national and global levels. Therefore, it is necessary to understand the trend of temporal and spatial changes of pollution caused by these events to reduce their adverse consequences in different regions. Based on the findings of this study, the trend of temporal changes in dust events and the pattern of dust particle distribution in the southern half of Fars province is also worrying because, in most cities of Fars province, an increasing trend in air pollution was observed. In addition, according to PDSI maps, a large part of the province is exposed to the dangers of dust storms and air pollution. Considering that PDSI is calculated based on the frequency of local to severe events, it can be concluded that the frequency of wind erosion events has increased in most cities of Fars province. In other words, these findings indicate the intensification of dust events and pollution caused by it in this province. Our results also showed that in the longterm (20002018), the southern half of Fars province, compared to the northern half, was more sensitive to dust events and, as a result, played a major role in dust production across the province. One of the reasons is drying the bed of BakhteganTashk, Maharloo, and Parishan wetlands, located in the southern half of the province, and have acted as dust generating sources, especially in recent years. As a whole, the results of this study can help managers and planners to prioritize managerial and executive measures to combat the risk of desertification and reduce the adverse impacts of dust storms in dusty areas.