رابطه بین تحوّلات زمین های الگودار با تغییرات زمانی و مکانی غلظت ترکیبات شیمیایی کفه نمکی پلایای سهل‌آباد (مطالعه موردی: استان خراسان جنوبی)

محیط حسّاس پلایا به‌مثابه یکی از بزرگ‌ترین منابع معدنی، جایگاه ویژه ای در فعّالیّت‌های اقتصادی دارد. ترکیبات شیمیایی موجود در پلایا برای خاک بسیار ضروری بوده و به منظور حاصلخیزی خاک کشاورزی مورد بهره‌برداری قرار می‌گیرد. پلایای سهل آباد در استان خراسان جنوبی به سبب داشتن دریاچه های اتّفاقی شور، اراضی مرطوب، پوسته های نمکی، توده های نمک سطحی و زمین های الگودار، چشم‌انداز ژئومورفولوژیک ویژه ای ایجاد کرده و از سوی ساکنان مورد بهره‌برداری‌های معدنی و کشاورزی قرار می گیرد. مسئله بهره‌برداری غیر اصولی و بیش‌ازحد منابع معدنی پلایای سهل آباد، ضمن بروز تحوّلات غیر طبیعی در چشم‌انداز ژئومورفولوژی پلایا می‌تواند باعث تشدید مخاطرات ناشی از فرسایش بادی ازطریق افزایش بار رسوب قابل حمل شود. در این بررسی درصد تغییرات برخی از عناصر شیمیایی شامل کلرید سدیم، سدیم و ژیپس با کمک داده های ماهواره ای در طی دو دوره زمانی محاسبه شده است. درصد تغییرات زمین های الگودار نیز با کمک تجزیه و تحلیل الگو و بافت اوّلین جزء اصلی تصاویر ماهواره ای محاسبه‌شده است. درنهایت، رابطه همبستگی بین این دو گروه از تغییرات در سطح کفه نمکی پلایا بررسی شده است. نتایج نشان می‌دهد که توده های نمک در سطح خاک پلایا غالباً از کلرید سدیم و ژیپس تشکیل شده‌ و یکنواخت نبودن توزیع موادّ شیمیایی محلول در محدوده چشم انداز پلایا سبب تنوّع در تشکیل زمین های الگودار شده است؛ همچنین بررسی رابطه بین تغییرات به وجودآمده در غلظت ترکیبات شیمیایی مورد بررسی با یکدیگر همبستگی ضعیفی را نشان می دهد. درنهایت بررسی رابطه بین تغییرات ترکیبات شیمیایی با تغییرات به وجودآمده در زمین های الگودار کفه پلایا وجود همبستگی از نوع مثبت و ضعیف در سطح معنی‌داری 0.05 = α را نشان می‌دهد. بیشترین اثرگذاری در بین ترکیبات شیمیایی مورد بررسی بر تحوّلات زمین های الگودار کفه پلایا مربوط به تغییرات غلظت ترکیب شیمیایی سدیم با مقدار همبستگی حدود 0.35 است.

Relationship between Patterned Grounds Evolutions and Spatial and Temporal Changes in the Chemical Compounds of SAHL ABAD Playa Salt Flats (Case Study: Khorasan province)

The sensitive environment of Playa, as one of the largest mineral resources, has a special place in economic activities. Chemical compounds available in Playa are essential for soil which are used to fertilize agricultural soil. SAHL ABAD playa in the south Khorasan province, have special geomorphologic landscape by the presence of ephemeral saline lakes, wetlands, salt crusts, surface accumulations of salt and zones of pattern ground and it is always inhabited by mineral and agricultural exploitation. The issue of incorrect exploitation and excessive mineral resources of the Sahl Abad playa with the occurrence of abnormal changes in the playa geomorphology perspective can exacerbate the risks of wind erosion by increasing the sediment load. In this study, percent changes in some of the chemical compounds such as sodium chloride, sodium and gypsum in the playa were calculated with the aim of satellite data for two periods. Besides, using texture and pattern analysis of the PCA1, percent changes in the surface pattern grounds of the playa was calculated. Finally, we study the relationship between these two groups of changes in the playa surface. It was found that soilsurface salt accumulations are dominated by sodium chloride and gypsum and distribution of chemical soluble is not uniform across the playa landscape resulting in the variety form of pattern ground. Moreover, chemical compounds, are correlated with each other. There is positive relationship between percentage changes in patterned grounds and the percentage of changes in the chemical compounds at a significant level. The greatest effect on the chemical compounds studied on the evolution of pattern grounds of playa surfaces is related to changes in the concentration of sodium chemical composition with a correlation of about 0.35.Extended Abstract1IntroductionPlaya is a closed drainage system with a shallow water mass, which is strongly influenced by evaporation due to the drought conditions in its environment. The sensitive environment of Playa, as one of the largest mineral resources, has a special place in economic activities. Chemical compounds available in Playa are also essential for soil and are used to fertilize agricultural soil. SAHL ABAD playa in the south Khorasan province, have special geomorphologic landscape by the presence of ephemeral saline lakes, wetlands, salt crusts, surface accumulations of salt and zones of pattern ground and it is always inhabited by mineral and agricultural exploitation. The issue of incorrect exploitation and excessive mineral resources of the Sahl Abad playa with the occurrence of abnormal changes in the playa geomorphology perspective can exacerbate the risks of wind erosion by increasing the sediment load.2Materials and MethodsIn this study, changes in the concentration of chemical compounds of playa surface as independent variables and morphological changes of pattern grounds are considered as dependent variables. Percent changes in the chemical compounds such as sodium chloride, sodium and gypsum in the playa were calculated with the aim of satellite data for two periods. Besides, using texture and pattern analysis of the PCA1, percent changes in the surface pattern grounds of the playa were calculated. Finally, we study the relationship between these two groups of changes in the playa surface.3Results and DiscussionIt was found that soilsurface salt accumulations are dominated by sodium chloride and gypsum. Besides, the distribution of chemical soluble is not uniform across the playa landscape resulting in the various forms of patterned grounds. Furthermore, chemical compounds, are correlated with each other. There is positive relationship between percentage changes in patterned grounds and the percentage of changes in the chemical compounds at a significant level. The greatest effect on the chemical compounds studied on the evolution of pattern grounds of the playa surfaces is related to changes in the concentration of sodium chemical composition with a correlation of about 0.35. Therefore, the most unstable pattern grounds are found in the zones where sodium and sodium chloride chemical compounds predominate. In fact, the zones of the playa surface, covered by salt shells and masses, exposed and exhibited a few prominent patterns, are patterned grounds with the predominance of chemical compounds of sodium and sodium chloride in the region. These zones are considered in the group of patterned grounds with severe regional changes. The least correlation between chemical variables and texture of the pattern grounds is related to gypsum chemical compounds. Due to the low rainfall and humidity of the region and the less tendency for this chemical composition to the process of dissolving, the time required to create the most prominent pattern grounds with the presence of this chemical composition in the playa surface is provided. Therefore, in pattern grounds, with less changes or relatively stable of the playa surface, the chemical composition of gypsum is overcome, with the most significant patterns due to the presence of gypsum chemical composition.4ConclusionThe evaluation of pattern grounds according to the changes made in chemical compounds to detect environmental changes or other changes in the playa surface is an important issue that can indicate the desertification status and the severity of the risks of the expansion of the playa. In general, the results of this study indicate a correlation between the changes in the concentration of chemical compounds with the changes in the patterned areas of the study area. Investigating the chemical changes of the Sahl Abad playa surface indicates a slow and limited trend in the expansion of the playa during the study period. In these studies, data deficits are one of the most important problems, while the satellite data can be replaced by field observations if it is possible to provide reliable interpretations of the spectrum. Therefore, we can assess the relationship between the effective variables in the Playa expansion process, and given the fact that the process of satellite imaging is a sequential process, one can create relationships in previous studies in a region and with the advancements in technology, it instantly optimized.