Variation of Air Dose Rate Between Residual Moist Soil and Host Rocks in a Dried Hamamok Small Dam Environment, Koy Sanjaq District, Kurdistan Region, Iraq

Naturally occurring radioisotopes (radionuclides) such as ²³⁸U, ²³²Th, and ⁴⁰K, along with their decay products, contribute significantly to external gamma radiation in the environment. The present geological study investigates the variation of outdoor gamma air dose rates in the drought-affected Hamamok Dam basin soil compare to surrounding virgin soils (weathered host rocks) in the Koy Sanjaq District-Iraq. Due to extremely low rainfall in the past two years, the dam is nearly empty, exposing extensive soil deposits and enabling direct field assessment. Air dose rate measurements were conducted using a Thermo Scientific RIIDEye-G handheld detector along two transects: accumulated soils within the dam basin (Dip direction) and undisturbed virgin soils (Strike line). Results showed that dose rates in the dam basin ranged from 40.8 to 55.3 nSv h⁻¹, with a mean of 47.53 nSv h⁻¹, while virgin soils recorded 30.2–45.3 nSv h⁻¹, averaging 34.83 nSv h⁻¹. Radiological risk analysis revealed that the mean annual effective dose AED (0.083 mSv yr⁻¹) and excess lifetime cancer risk ELCR (2.91 × 10⁻⁴) remain below international safety thresholds, though slightly elevated compared to natural background levels. These findings highlight the influence of upstream sediment deposition and current mineral composition on radionuclide accumulation in dam environments. This study underscores the importance of regular monitoring of natural radionuclide activity in upstream deposits to ensure consumer safety.