نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم و مهندسی محیطزیست، دانشکده جغرافیا و علوم محیطی، دانشگاه حکیم سبزواری، سبزوار، ایران
2 گروه جغرافیای طبیعی، دانشکده علوم جغرافیایی و برنامهریزی، دانشگاه اصفهان، اصفهان، ایران
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Introduction: Given the growing and alarming trend of land cover changes-primarily driven by unsustainable Development in agricultural, urban, and industrial sectors-surface water resources, especially rivers, are increasingly threatened by various pollutants. Among the most critical of these are heavy and toxic metals, which pose serious risks to human and ecological health by directly or indirectly entering the food chain. As a vital transboundary water resource for the northwestern provinces of Iran, the Aras River is exposed to such threats. Accordingly, this study aims to perform a spatiotemporal analysis of land cover changes and investigate their relationship with variations in heavy metal concentrations in the Aras River. The primary focus is on identifying spatial patterns of overlap between land use transformation and chemically polluted hotspots, as well as evaluating the ecological risk potential of toxic elements entering the food web.
Material and methods: To analyze land cover change trends from 2001 to 2024, time-series satellite imagery from the MODIS sensor (MCD12Q1 product) was utilized. Land cover dynamics were extracted and analyzed for three key years: 2001, 2012, and 2024. Concurrently, field sampling was conducted at 13 selected stations along the Aras River during two seasonal intervals (May and August 2024). The collected water samples were acidified and prepared following standard protocols, and were chemically analyzed using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Target metals included lead (Pb), arsenic (As), nickel (Ni), cadmium (Cd), mercury (Hg), and chromium (Cr), which were evaluated in terms of concentration, spatial distribution, and compliance with national and international standards (FAO, WHO, EPA).
Results and discussion: Land cover analysis revealed that rangelands and agricultural lands experienced the highest rates of change throughout the study period. Chemical analysis of the water samples in May showed that concentrations of lead, arsenic, and nickel exceeded international permissible limits in several stations. In August, although lead concentrations relatively decreased, other elements including arsenic, cadmium, mercury, nickel, and chromium maintained relatively uniform levels across most stations-often approaching ecological risk thresholds. While some metal concentrations remained within safe limits for agricultural irrigation, livestock consumption, and aquatic tissue accumulation, they were deemed unsuitable for aquatic life. Long-term human exposure through consumption of contaminated agricultural, livestock, or aquatic products could pose serious toxicological risks due to bioaccumulation.
Conclusion: The results indicated a significant and meaningful correlation between land use change and increased concentrations of toxic heavy metals in surface waters. These findings underscore the urgent need to revise land management policies, enforce stricter controls on the discharge of untreated effluents, and enhance continuous water quality monitoring systems. By integrating remote sensing data with laboratory-based environmental assessments, this.
کلیدواژهها [English]
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