Technogenic nature of radionuclide distribution at operating uranium sorption sites in Uzbekistan: a comprehensive assessment of air, surface, and soil compartments

In the arid landscapes of Central Asia, beneath the shifting sands of the Kyzylkum desert, lie vast deposits of uranium. This element, a heavy metal found naturally in the Earth's crust, is the fuel that powers nuclear energy. To extract it, mining companies often use a method called in-situ leaching. Instead of digging massive open pits or tunneling deep underground, they pump a special liquid solution into the ground to dissolve the uranium directly from the rock. The liquid, now carrying the dissolved metal, is pumped back to the surface. There, it passes through a filtration system where the uranium is captured on special beads, much like a sponge soaking up water, leaving the rest of the liquid behind. This process is efficient and leaves the surface largely undisturbed, but it brings a hidden challenge: the uranium solution releases a colorless, odorless gas called radon, and tiny particles of radioactive dust can become airborne. Because these substances are invisible, scientists must measure them carefully to understand if the mining operation is creating a radiation hazard for the workers and the nearby communities, or if the levels are simply part of the natural background radiation that exists everywhere on Earth.

A team of researchers from universities in Uzbekistan set out to solve this puzzle at six active uranium sorption sites in the Samarkand region. Their goal was to determine whether the radiation levels found around these facilities were caused by the mining technology itself or by the natural geology of the area. To do this, they did not rely on a single measurement. Instead, they conducted a comprehensive survey that looked at the air, the ground, the surfaces of the machinery, and the soil. They measured the concentration of radon gas and its decay products in the air, checked the level of gamma radiation—the kind that can penetrate walls and reach the human body—around the equipment, and tested the surfaces of the machinery for radioactive contamination. They also dug up soil samples to analyze the natural radioactive elements present in the ground. Crucially, they compared all these measurements against data collected from eight control points in nearby residential villages, far away from the industrial activity, to establish a baseline of what the environment looks like without the influence of the mine.

The results painted a clear picture of where the radiation was coming from. Inside the operational zones, particularly at the resin exchange platform where the uranium is separated from the liquid and at the sorption columns where the process happens, the air was significantly more radioactive than in the surrounding villages. The concentration of radon gas and long-lived radioactive dust in these specific work areas was nearly four times higher than the background levels found in the control villages. Similarly, the radiation dose rate from the ground and equipment in these zones was up to five times higher than the natural background. The researchers also found that the surfaces of the machinery, especially the pumps and the exchange platforms, were contaminated with radioactive material. In several instances, the contamination on these surfaces exceeded the safety limits set by international standards for low-toxicity materials. This pattern was consistent: the closer the measurement point was to the active processing of the uranium solution, the higher the radiation levels.

However, the story changed when the researchers looked at the soil. If the mining process were spreading radioactive material widely into the earth, the soil near the factories should have shown much higher levels of natural radioactive elements than the soil in the villages. The data showed a different reality. While the soil near the uranium sites did have slightly higher levels of natural radionuclides than the control villages, the difference was small—only about eighteen percent. More importantly, the levels of radiation in the soil, even at the sites, remained well below the international safety limits recommended for the general population. The researchers calculated various safety indices based on the soil composition, and every single one came out as safe. This finding was critical because it ruled out the idea that the geological background of the area was the primary cause of the high radiation readings found in the air and on the equipment. The soil was relatively uniform, meaning the dramatic spikes in air and surface radiation could not be blamed on the natural geology.

By combining these different lines of evidence, the study concluded that the elevated radiation levels were a direct result of the technological process. The strong connection between the high radon levels, the radioactive dust, the gamma radiation, and the surface contamination all pointed to the same source: the handling of the uranium-bearing solutions. The fact that these high levels were confined to the specific zones where the technology operated, while the soil remained relatively clean and safe, confirmed that the radiation was not a natural feature of the landscape but a byproduct of the industrial activity. The study also used statistical methods to show that these different radiation indicators moved together; when one was high, the others were high too, reinforcing the idea that they shared a common origin.

The implications of these findings are specific and practical. The research indicates that the primary risk to human health at these facilities is not from the ground beneath their feet, but from the air they breathe and the surfaces they touch within the industrial zones. The workers operating the resin exchange platforms and the sorption columns are the ones most exposed to these elevated levels. The study suggests that radiation protection efforts should focus intensely on these specific areas, ensuring that workers are properly shielded and that ventilation systems effectively remove the radioactive gas and dust. While the surrounding environment and the soil remain safe, the operational zones require strict management to keep the workers' exposure within safe limits. This work provides a detailed map of where the radiation is and where it is not, offering a scientific basis for protecting the people who keep the uranium production running.