Bangladesh Atomic Energy Commission

The Asia–Pacific region encompasses hydrologically diverse and climate-vulnerable systems, where groundwater security is increasingly threatened by over-exploitation, climate change, urbanization, and salinization. This regional synthesis, developed under the IAEA Technical Cooperation Project RAS7040, integrates environmental isotopes (δ¹⁸O, δ²H, d-excess, ³H), hydrochemical indicators, and numerical modeling to delineate groundwater recharge processes, surface–groundwater interactions, and salinization mechanisms across contrasting hydroclimatic settings, including coastal, urban, alpine, riverine, and arid basins. Multi-country case studies from Lao PDR, Pakistan, Mongolia, China, Bangladesh, Indonesia, Vietnam, Australia, and the Philippines demonstrate the robustness of isotope-based diagnostics for resolving complex groundwater systems. Across the region, results consistently identify local meteoric precipitation as the dominant recharge source, while revealing pronounced contrasts in recharge timing, aquifer vulnerability, and salinity evolution governed by climate variability, land use, and geological framework. In densely populated coastal plains, such as Bangladesh, shallow aquifers exhibit active seawater intrusion, clearly traced by diagnostic Cl⁻–δ¹⁸O mixing relationships, whereas deeper confined aquifers commonly contain isolated paleo-salinity or remain largely protected from modern marine ingress. In high-altitude glacier-fed catchments (e.g., the Mingyong Basin, China), isotope-based hydrograph separation quantifies increasing seasonal meltwater contributions to river discharge, highlighting climate-driven shifts in runoff generation and long-term water storage. In Mongolia’s Kherlen River Basin, groundwater and surface water plot close to the Global Meteoric Water Line, indicating minimal evaporative modification prior to recharge. Strong seasonal contrasts in precipitation isotopes—from highly depleted winter values (δ¹⁸O ≈ −30‰) to enriched summer rainfall (δ¹⁸O ≈ −12‰)—demonstrate that groundwater recharge is dominated by warm-season precipitation, with clear isotopic evidence of river–groundwater exchange in alluvial reaches. In arid to semi-arid regions of Pakistan, stable isotopes are critical for quantifying evaporation losses, identifying recharge zones, and distinguishing irrigation return flow from natural recharge in intensively managed aquifer systems. In Australia, isotope (δ¹⁸O, δ²H, ³H) and hydrochemical investigations of the Thirlmere Lakes conclusively identify evaporation as the dominant mechanism driving lake-level decline, with a secondary, multi-decadal groundwater recharge component. Urban aquifers in major cities (e.g., Hyderabad, Metro Manila, Karachi) show heightened vulnerability to anthropogenic contamination and reduced recharge, diagnosed through isotopic enrichment patterns and complementary tracers such as nitrate isotopes. In the riverine systems of Lao PDR and Vietnam, isotopic apportionment clarifies Mekong and Red River connectivity with adjacent alluvial aquifers, providing essential insights for transboundary water management. When coupled with Bayesian mixing models and variable-density flow simulations, the integrated isotope–geochemical approach effectively differentiates modern seawater intrusion from relic salinity, quantifies river–aquifer interactions, and constrains recharge source elevations and catchment domains. This synthesis underscores the value of regional scientific coordination to harmonize methodologies, identify transboundary groundwater linkages, and upscale local findings. Overall, it demonstrates that isotope-based evidence is indispensable for science-informed policy, supporting managed aquifer recharge, regulation of abstraction, and early-warning systems for salinization and water-quality degradation, thereby advancing climate-resilient water governance across the Asia–Pacific region. Key words: Isotope Hydrology, Groundwater Recharge, Seawater Intrusion, Aquifer Vulnerability, Water Resource Management, Asia–Pacific Region

Tephritid fruit flies are major pests of fruits and vegetables in tropical regions, causing significant economic losses. Effective monitoring using male lure-based traps, such as methyl eugenol (ME) and cue-lure (CL), is essential for integrated pest management. This study evaluated the influence of lure type, trap height, storage condition, and seasonal dynamics on fruit fly captures at two sites (AERE and Jahangirnagar University) in the Savar region of Bangladesh. Methyl eugenol (ME) and cue-lure (CL) traps were deployed at three heights (2, 3, and 5 ft) over a one-year period (August 2023-July 2024). A total of 36,107 male fruit flies, representing nine Bactrocera, Dacus and Zeugodacus species, were recorded. ME traps consistently captured significantly more males than CL traps (p < 0.05), confirming strong lure-specific selectivity—B. dorsalis and B. zonata dominated ME catches, whereas Z. cucurbitae and Z. tau predominated in CL traps. Trap height showed no significant effect on captures, suggesting that low-level deployment (~1-1.5 m) is adequate for field monitoring. Fruit fly abundance peaked during summer (June-July) and declined in winter (December-February), reflecting climatic influences on population activity. Lure longevity tests demonstrated that cold storage (4°C) substantially prolonged lure efficacy compared to storage at room temperature or sunlight exposure. Collectively, these findings highlight that lure type, seasonal timing, and proper storage are key determinants of trapping success, while trap height plays a minor role. The results provide practical recommendations for optimizing fruit fly surveillance and integrated pest management strategies in Bangladesh.

In this work, a sustainable and cost-effective approach was developed to synthesize a ternary composite (NiMn2O4/TiO2-Chitosan) via an eco-friendly method using coconut cotyledon extract as a reducing agent. This environmentally friendly synthesis route successfully developed a nanocomposite with distinct structural and morphological characteristics. XRD analysis confirmed the formation of a highly crystalline phase, while FESEM revealed mixed and irregular morphologies. EDAX spectrum qualitatively verified the presence of Ni, Mn, Ti, C and O in the composite. HRSTEM further displayed a disordered cubic structure, indicating nanoscale complexity. The optical band gap of the composite was determined to be 2.93[Formula: see text]eV, suggesting potential for semiconducting applications. Electrochemical evaluation in a three-electrode system using KOH electrolyte demonstrated a remarkable specific capacitance of 1089.41[Formula: see text]F g[Formula: see text] at a current density of 1[Formula: see text]mA g[Formula: see text]. Furthermore, the electrode exhibited an excellent energy density of 45.77[Formula: see text]Wh kg[Formula: see text] with a power density of 275[Formula: see text]W kg[Formula: see text], underscoring its superior energy storage performance. These results confirm the successful fabrication of highly efficient electrode material through a green, economical and facile method. The unique architecture and outstanding supercapacitor behavior of NiMn 2 O 4 /TiO 2 -Chitosan composite make it a promising candidate for advanced energy storage applications.

In this paper, a high-efficiency solar water pumping drivetrain system is presented for off-grid rural irrigation in Bangladesh. The system integrates a Kalman Filter-based Maximum Power Point Tracking (MPPT) algorithm, silicon carbide (SiC) power electronic converters, and Direct Torque Control (DTC) for induction motor drive regulation. The proposed MPPT method ensures stable maximum power extraction under rapidly varying irradiance, while SiC devices reduce switching losses and heat sink volume. DTC provides fast and robust torque response without conventional PI-loop limitations. Simulation studies and embedded implementation on a TI C2000 platform demonstrate improved efficiency, reduced converter losses, and enhanced operational reliability.