| چکیده انگلیسی مقاله |
Controlling soil erosion and sediment production mitigates both local and regional impacts of wind erosion, thereby promoting environmental sustainability. This study assessed the effectiveness of weathering indices in identifying and differentiating sediment sources and their respective contributions to wind-blown deposits in the Daranjir Desert, located in Bafq. A total of 21 samples were collected from potential sediment sources—including alluvial fans, agricultural lands, and clay plains—alongside 7 samples from sand dunes representing the annual sediment yield. Fifty-four weathering indices were calculated. Using statistical analysis, four indices—Fe/Al, Bases to Alumina, Chemical Proxy of Alteration (CPA), and K/Al—were identified as optimal tracers, demonstrating 100% accuracy in distinguishing sediment sources. According to a Bayesian mixing model, the estimated contributions to sediment production were 86% from clay plains, 9.5% from alluvial fans, and 9.5% from agricultural lands. Simulations using a virtual sediment model revealed strong concordance between predicted and observed data. These findings underscore the utility of weathering indices as reliable tracers for source attribution in wind-blown sediments, offering valuable insights for erosion control and sustainable environmental management. Extended Abstract 1-Introduction Wind erosion is a widespread environmental challenge that significantly impacts arid and semi-arid regions across the globe. Situated within the global arid and semi-arid belt, Iran is recognized as a major contributor to dust generation. Approximately two-thirds of Iran's land area falls within these climatic zones, and regions affected by wind erosion account for more than one-third of the Earth's terrestrial surface. Consequently, the implementation of soil conservation and sediment control strategies, the acquisition of data on the relative significance of sediment sources, and the identification of critical erosion-prone areas are of vital importance. To evaluate erosion rates and sediment yield, researchers have employed a variety of methods and techniques. Among these, sediment fingerprinting has emerged over the past two decades as a particularly innovative and effective approach. This technique estimates the contribution of individual sediment sources to basin-wide sediment output by comparing the properties of eroded soils from various sources with those of the accumulated sediment. The underlying principle is that distinct sediment sources can be identified using a suite of geochemical or mineralogical tracers. By matching the characteristics of sediment samples with those of potential source soils, it becomes possible to quantify the contribution and significance of each source to overall sediment production. The primary aim of this study is to evaluate the effectiveness of weathering indices in tracing the provenance of aeolian sediments on an annual scale in the Daranjir Desert, located in Bafq. The research was conducted over a yearly cycle to capture variations and trends in wind-driven sediment production. By focusing on annual data, the study enhances the accuracy of source identification and enables a more precise assessment of each source's contribution to aeolian sediment yield. 2-Materials and Methods In this study, sampling was conducted using two complementary approaches: one targeting sediment sources and the other focusing on the deposited sediment. A total of 28 samples were collected across the study area using systematic random sampling. These included 7 target sediment samples and 21 source samples, comprising 9 from alluvial fans, 5 from agricultural lands, and 7 from clay plains. Following the calculation of weathering indices, two statistical tests were applied to evaluate the suitability of conservative tracers. Composite fingerprints were selected using the Kruskal–Wallis test (significance threshold: 0.05) and discriminant analysis. Tracers with p-values below 0.05 were deemed effective in distinguishing among sediment sources and were subsequently incorporated into the discriminant function. These analytical methods successfully identified tracers capable of reliably discriminating sediment origins. The relative contributions of sediment sources were quantified using a Bayesian mixing model, while model uncertainty was assessed through virtual sediment simulations. Based on the evaluation of 14 datasets, performance metrics—including Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and Agreement Index (d)—were calculated to validate the model’s predictive accuracy. 3- Results and Discussion In this study, four weathering indices—Fe/Al, Bases to Alumina, Chemical Proxy of Alteration (CPA), and K/Al—were selected as optimal tracers from an initial pool of 54 indices. The results revealed that clay plains contributed the highest share of sediment production, accounting for 86%. Field surveys and investigations confirmed that clay plains are the dominant sediment source in the study area. This predominance is attributed to the region’s extreme diurnal temperature fluctuations, which induce repeated expansion and contraction in clay soils. Due to their expansive nature—primarily driven by the presence of smectite minerals—these soils develop deep cracks upon rapid drying. Such fissures expose fine particles from subsurface layers, which are easily mobilized by wind. The clay plains are covered by a hard yet fragile duricrust composed of carbonates and salts, offering temporary protection against erosion. However, this crust is vulnerable to disruption by natural forces such as sharp temperature shifts, sporadic light rainfall (which breaks the crust through raindrop impact), and anthropogenic activities. Once compromised, the underlying fine particles—less than 2 microns in size—become highly susceptible to wind erosion. Additionally, throughout the year, physical weathering processes (e.g., salt crystallization and aeolian abrasion) and chemical weathering (e.g., clay mineral decomposition) continuously generate fine particles. These materials accumulate in the clay plains, forming a readily available reservoir for wind transport. This study demonstrates that integrating weathering indices as geochemical fingerprints with statistical modeling techniques yields a robust framework for tracing sediment provenance. Such an approach offers valuable insights for managing aeolian sediment dynamics and implementing effective erosion control strategies in arid environments. 4- Conclusion Wind erosion is a major driver of environmental degradation in arid and semi-arid regions, with far-reaching consequences for ecological sustainability and human livelihoods. The need to investigate aeolian sediments and identify their sources prompted this study, which explores sediment provenance using geochemical weathering indices. Notably, this research represents the first attempt to trace aeolian sediment sources in the Darangir Desert, Bafq, through the application of geochemical tracers and weathering indices. To quantify the contribution of different sediment sources, a Bayesian mixing model was employed. The results offer a foundational framework for erosion mitigation and sediment control strategies in the region. By accurately identifying the dominant sediment sources, targeted management and conservation measures can be developed and implemented. Despite its strengths, sediment source identification research faces inherent limitations. Budget constraints often restrict the number of samples collected from both source areas and target sediments. Nonetheless, this study stands out for its novelty and practical relevance, utilizing cost-effective and environmentally friendly tracers alongside a precise and reliable provenance tracing method. A key unresolved question is whether the type and relative contribution of sediment sources vary across seasons, influenced by changes in wind speed and direction. Therefore, future studies are encouraged to incorporate wind dynamics—particularly sand drift potential across different seasons—into sediment source identification frameworks for wind erosion research. |