Uranium presence in water

Uranium, with the symbol U and atomic number 92, sits on the periodic table as a naturally occurring radioactive element. This means its nucleus spontaneously decays, releasing energy and particles like alpha or beta rays. Each uranium atom has 92 protons within its nucleus, balanced by 92 electrons orbiting around it. These electrons are arranged in specific energy levels, with the outermost six being the valence electrons. These valence electrons are crucial as they determine an element's chemical behavior and its ability to form bonds with other elements.

The unique electronic configuration of uranium plays a critical role in its suitability for nuclear applications. The six valence electrons contribute to uranium's fissionability, which is its ability to split apart when bombarded by neutrons readily. This fission process releases tremendous energy, harnessed in nuclear reactors to generate electricity ( Department of Energy. )

A Heavyweight Champion:

Uranium isn't just radioactive; it's also the heaviest naturally occurring element on Earth. This hefty title comes from its high atomic weight, which is the sum of the protons and neutrons in its nucleus. Uranium's natural abundance primarily consists of the isotope U-238, meaning it has 238 neutrons in its nucleus, contributing significantly to its overall weight.

The high density of uranium becomes crucial during nuclear fuel design and reactor operation. This density allows for a compact fuel assembly, packing much energy into a smaller volume than other fuels. Additionally, uranium's density moderates the fission rate within a reactor, ensuring a controlled and stable energy release ( World Nuclear Association .)

Freshly mined or refined uranium boasts a silvery-white metallic luster. However, its beauty fades quickly. Uranium is chemically reactive, readily forming a black oxide layer when exposed to air. This process, called tarnishing, is an example of uranium losing electrons to oxygen in the atmosphere  (Geoscience Australia.) 

Furthermore, finely divided uranium exhibits a surprising property: pyrophoricity. When finely ground, the large surface area of the particles allows for rapid oxidation, generating enough heat to ignite the uranium spontaneously  (Britannica.)  This pyrophoric nature necessitates carefully handling and storing uranium in its finely divided form  (NRC.) 

Unlocking Energy: The Power of Fission

The true magic of uranium lies in its ability to undergo nuclear fission. When a neutron collides with a U-235 nucleus (a rare isotope of uranium), it triggers a chain reaction  (energy.gov.)  The nucleus splits, releasing enormous amounts of energy, several neutrons, and fission products. These neutrons can then go on to fission other U-235 nuclei, perpetuating the chain reaction and generating a sustained release of energy. This process forms the core principle behind nuclear power plants, where controlled fission reactions provide a reliable source of electricity for over 60 years  (BKV energy.) 

Nuclear Fission: The Core of the Process

Nuclear power plants produce renewable, clean energy. They do not pollute the air or release greenhouse gases. They can be built in urban or rural areas and do not radically alter the environment around them  (NatGeo.)  Nuclear power plants generate electricity by harnessing the energy released during nuclear fission. This heat is then used to create steam, which drives turbines to generate electricity. The heart of a nuclear power plant is the reactor  (energy.gov.)  It's a heavily shielded container that houses the fuel rods, control rods, and coolant:

• Fuel Rods: These long, slender rods contain uranium pellets enriched with uranium-235, the fissile isotope (capable of readily undergoing fission).
• Control Rods: Made of materials that absorb neutrons, control rods regulate the fission rate within the reactor core. Inserting control rods slows down the fission process while withdrawing them speeds it up. This allows for precise control over the reactor's power output.
• Coolant: A circulating fluid, typically water, absorbs the heat generated from fission within the reactor core. This heated coolant carries the thermal energy throughout the plant  (NatGeo.) 

The hot coolant exiting the reactor core doesn't directly come into contact with the water used to generate steam for the turbines. A heat exchanger, also known as a steam generator, plays a crucial role in this process. Inside the heat exchanger, the hot reactor coolant transfers its thermal energy to a separate water loop, converting the water in this secondary loop into high-pressure steam. This pressurized steam is then directed to the turbine section of the plant. The high-pressure steam hits the turbine's blades, causing it to spin at high speeds. The rotating turbine shaft is connected to a generator, which converts the mechanical energy of the spinning turbine into electricity through the principle of electromagnetic induction.

Safety Measures

Nuclear power plants incorporate multiple safety systems to ensure safe operation and prevent accidents  (CDC.)  These include:

• Emergency shutdown systems: These systems can automatically shut down the reactor in case of any abnormalities or malfunctions.
• Containment structures: A robust containment structure surrounds the reactor core, designed to prevent the release of radioactive material in case of an accident.

Beyond the Weight: Applications in Medicine and Research

While primarily known for its role in nuclear power, uranium's unique properties find applications in other fields. In medicine, low-dose radiation from specific uranium isotopes is used in certain types of bone scans to diagnose bone diseases like osteoporosis. Additionally, uranium's ability to shield against radiation makes it useful in radiotherapy equipment used to treat cancer  (NISA.) 

Beyond the medical field, uranium's isotopes play a crucial role in radiometric dating, a technique used to determine the age of rocks and other geological formations. This technique exploits the predictable radioactive decay of uranium isotopes into other elements, allowing scientists to estimate the time elapsed since the formation of a rock or mineral  (PBS.) 

Who Discovered Radioactivity and the Story Behind It

In 1895, Wilhelm Röntgen had just unveiled his groundbreaking discovery of X-rays  (DPMA) . This sparked Henri Becquerel's interest, who, inheriting his father's passion for phosphorescence, wondered if there was a connection between X-rays and the phenomenon of glowing materials. He decided to investigate if fluorescent materials, like uranium salts known to emit light after exposure to sunlight, could also emit X-rays when exposed to sunlight. Becquerel prepared several experiments, wrapping photographic plates with black paper and placing various fluorescent materials on top. He then exposed the setup to sunlight, expecting the materials to emit X-rays that would penetrate the paper and fog the plates  (APS.) 

However, on February 24, 1896, a cloudy day turned his plans upside down. Unable to expose his setups to sunlight, Becquerel decided to develop the plates anyway, just in case. To his surprise, the developed plates showed silhouettes of the uranium salts used, even though they hadn't been exposed to sunlight. This unexpected finding piqued Becquerel's curiosity. He conducted further experiments, proving that the radiation causing the fogging was not dependent on sunlight and could pass through materials like paper and aluminum. He named this phenomenon "becquerel rays," later known as radioactivity  (ANS.) 

Becquerel continued his research, discovering that other materials besides uranium exhibited radioactivity. However, it was Marie and Pierre Curie's subsequent work on pitchblende, a uranium ore, that ultimately led to the isolation of radium and polonium, further solidifying the understanding of radioactivity  (Nobel Prize.) 

Radioactivity, the spontaneous decay of atomic nuclei, poses a threat to our health because it disrupts the delicate balance within our cells at the molecular level. When radioactive atoms decay, they release energetic particles or radiation (alpha, beta, or gamma rays). These high-energy particles can directly ionize molecules in our body's tissues. Ionization occurs when an atom or molecule gains or loses an electron, altering its chemical behavior  (  Reisz  et al., 2014.) This molecular disruption can have several detrimental effects:

• DNA Damage: Cellular DNA, the blueprint for life, is particularly vulnerable to radiation. Ionization can break vital bonds within the DNA structure, leading to mutations or errors in the genetic code. These mutations can cause uncontrolled cell growth (cancer) or even cell death  (Borrego-Soto et al., 2015.)  
• Disruption of Cellular Processes: Radiation can also ionize other vital molecules within cells, like enzymes or proteins responsible for critical cellular functions. This disruption can hinder essential processes like cell repair, metabolism, and cell division  (Reisz et al., 2014.)  
• Tissue Damage: In high doses, radiation can directly damage tissues and organs. This can lead to radiation sickness, characterized by nausea, vomiting, hair loss, and even death in extreme cases  (Reisz et al., 2014.)  

The severity of the damage depends on several factors, including the type and amount of radiation exposure, the duration of exposure, and the individual's overall health. While our bodies have some natural repair mechanisms for DNA damage, prolonged or high-dose exposure can overwhelm these processes and produce detrimental changes  (MedlinePlus.) 

Unfortunately, uranium, a naturally occurring radioactive element, can find its way into groundwater supplies, posing a potential health risk. Here are a few pathways of its intrusion into the groundwater:

Rock Dissolution: Uranium is present in various rock formations, often in trace amounts. However, its concentration can vary depending on the specific rock type. Granites and sandstones are common examples of rocks containing uranium. Groundwater, the hidden treasure beneath our feet, is the dissolving agent in this scenario. As water percolates through rock layers over extended periods (potentially thousands or even millions of years), it interacts with the minerals within the rock. These reactions involve the breakdown of mineral bonds, allowing the dissolved components to be carried away by the flowing water  (NatGeo.) 

Uranium tends to be more soluble in acidic environments (lower pH). This means it dissolves more readily into the flowing water, potentially leading to higher uranium concentrations in the groundwater. Minerals like carbonates can neutralize the acidity and reduce uranium solubility. In some cases, uranium can interact with other dissolved minerals in the water to form less soluble compounds. For instance, iron oxides can bind uranium, limiting its mobility and reducing its presence in the resulting groundwater  (  Stagg et al., 2022. )

Uranium Mining: The mining process involves extracting uranium ore from the ground, often through crushing and grinding activities. This can generate airborne uranium dust, posing a respiratory health risk to miners and potentially contaminating nearby soil and water bodies if not adequately controlled. Processing the extracted ore to separate the uranium further increases the risk. The use of chemicals and water in this process can dissolve soluble uranium compounds, creating a contaminated liquid waste stream. If not properly contained and treated, this wastewater can seep into the ground, eventually reaching groundwater supplies  (Ma et al., 2020.) 

Phosphate Fertilizers: Phosphate rock, the primary source material for many fertilizers, often contains trace amounts of uranium as a natural impurity. While the concentration is generally low, the widespread use of phosphate fertilizers across vast agricultural areas can contribute to uranium accumulation in the soil over time. As water percolates through the soil layers, it can slowly dissolve the trace uranium present in the applied fertilizers. Over extended periods, this dissolved uranium can gradually seep into underlying groundwater sources, potentially leading to contamination  (Sun et al., 2020.) 

Industrial Activities: Nuclear power plants rely on uranium as fuel. While these facilities are designed with elaborate safety measures to contain radioactive materials, accidents or malfunctions, however unlikely, can lead to the release of uranium into the environment, potentially contaminating nearby groundwater. Facilities involved in processing uranium for nuclear fuel or weapons production require stringent safety protocols. Leaks or spills during these processes can introduce uranium into the surrounding environment, potentially contaminating groundwater if not properly contained and remediated  (CNSC.) 

In soil and rock, Uranium, a naturally occurring radioactive element present in soil and rock, undergoes radioactive decay. This decay involves the breakdown of its unstable nucleus, releasing various forms of radiation and daughter elements. One crucial daughter element in this process is radon.

Uranium doesn't decay directly into radon. It goes through several steps, each releasing radiation and forming a new element  (EPA.)   A key step involves the decay of uranium-238 to radium-226. Radium-226, in turn, undergoes further decay to release radon-222, a gas, into the surrounding environment. Over time, groundwater can dissolve some of the uranium present in rocks and soil. Radon, being a gas, is not very soluble in water. This means it tends to escape from the water and become airborne. Air bubbles within the groundwater are pumped to the surface and can facilitate this release.

The primary culprit in uranium poisoning is the emission of alpha particles. These alpha particles are relatively large and energetic, but their range is limited. Unlike other forms of radiation, alpha particles cannot penetrate very deeply into tissues. However, the damage they cause is highly localized and severe. When ingested, uranium accumulates in certain organs, particularly the kidneys and bones. As alpha particles are emitted within these organs, they directly ionize nearby molecules within cells  (ATSDR.) 

Molecular Mayhem: The ionization caused by alpha particles disrupts the delicate balance within cells. This can damage critical cellular components like DNA, proteins, and enzymes. DNA, the blueprint for life, is particularly vulnerable. Alpha particles can break DNA strands, leading to mutations  (Roobol et al., 2020.)  Damage to proteins and enzymes can impair essential cellular processes like metabolism, repair mechanisms, and cell division. This disruption can lead to a decline in overall cell function and organ health.

Organ-Specific Effects: The kidneys are particularly susceptible to uranium accumulation. Direct cellular damage caused by alpha particles can lead to inflammation, reduced kidney function, and, ultimately, kidney failure in severe cases. The kidneys' primary function is to filter waste products from the blood. This filtration process involves reabsorbing essential elements and minerals the body needs while excreting waste products in urine. Unfortunately, uranium, when ingested, also gets filtered by the kidneys ( Guéguen, 2022 .) The slightly acidic environment within the kidneys can further influence uranium retention, as uranium tends to be more soluble in acidic conditions ( Zalyapin, 2008 ).

Uranium shares some chemical similarities with certain necessary elements like phosphates. This can lead to the kidneys mistakenly reabsorbing uranium alongside these essential components, allowing it to accumulate in the kidney tissue. Due to its size and charge, uranium has difficulty being efficiently excreted by the kidneys. While some uranium gets eliminated through urine, a portion remains trapped within the kidney tissue. As blood continuously flows through the kidneys, uranium gets filtered repeatedly. Over time, this repeated filtration process leads to a gradual uranium concentration within the kidney tissue  (Briner, 2010.) 

Despite its size, Uranium can cross the placenta to a limited extent. This means that a pregnant woman consuming water with high uranium levels can expose the developing fetus to the radioactive element. Studies in animals suggest that high uranium exposure during pregnancy can lead to birth defects ( Mirderikvand, 2014 .) The specific types of birth defects may vary, but they can affect various organ systems. Exposure to radiation, including alpha particles emitted by uranium, in utero may increase the child's risk of developing certain cancers later in life. Uranium exposure during critical stages of fetal development could potentially disrupt normal growth and development, leading to delays in cognitive or physical development  (John Hopkins Medicine.) 

Since radon is a gas, it can easily enter buildings through cracks in foundations, basements, or crawlspaces. Once inside, the gas can accumulate to high levels, posing a significant health risk.

Radon is the leading cause of lung cancer among non-smokers, according to the  World Health Organization (WHO) . When inhaled, radon gas enters the lungs, where it continues to decay, releasing alpha particles that can damage lung cells and increase the risk of cancer development. The risk of lung cancer from radon exposure is significantly higher for smokers. The combined effects of radiation and carcinogens from smoking create a synergistic effect, greatly amplifying the cancer risk ( CDC .)

Radon-222, the most common isotope of radon gas, is itself radioactive. However, the primary threat comes from its short-lived decay products, like polonium-218 and polonium-214. These daughter elements also decay rapidly, releasing bursts of highly energetic alpha particles. Once inhaled, alpha particles primarily damage cells within the lung tissue where they are inhaled and deposited. As alpha particles travel through lung tissue, they collide with molecules, directly causing ionization. Cellular damage caused by alpha particles can trigger an inflammatory response within the lungs. This inflammation can further damage lung tissue and impair its ability to function properly ( Belete et al., 2021 .)

The Navajo Nation, a large indigenous territory spanning parts of Arizona, Utah, and New Mexico, has a long and complex history with uranium mining. During the Cold War (1947-1991), the US government heavily relied on uranium for nuclear weapons production. Unfortunately, much of this uranium came from mines located on Navajo lands  (Dawson, 2011.) 

The urgency to obtain uranium during the Cold War often overshadowed environmental concerns. Mining practices at the time lacked proper regulations and safeguards against radioactive dust and contaminated water, which led to generating large quantities of airborne uranium dust. Inadequate dust suppression measures allowed this radioactive dust to settle on surrounding land, contaminating grazing areas, homes, and even playgrounds. Waste materials left over after uranium extraction, known as mine tailings, were often poorly managed. Rainwater and wind erosion carried radioactive contaminants from these tailings into nearby streams and aquifers, polluting vital water sources for the Navajo people  (Arnold, 2014.) 

The US government has acknowledged the negative consequences of uranium mining on the Navajo Nation  (EPA.)  However, the road to remediation has been slow and fraught with challenges:

• Incomplete Cleanup Efforts: The cleanup efforts undertaken by the government have been criticized for being insufficient. Many contaminated sites remain unaddressed, leaving communities vulnerable to ongoing exposure.
• Limited Resources and Infrastructure: The Navajo Nation faces a lack of resources and infrastructure necessary for a comprehensive cleanup. Providing the necessary support and funding is crucial for effective remediation.

The legacy of uranium mining continues to cast a long shadow on the health of the Navajo people. Navajo communities continue to experience higher rates of cancer, including lung cancer, kidney cancer, and bone cancer, compared to the national average. Additionally, exposure to uranium dust can lead to respiratory problems like chronic obstructive pulmonary disease (COPD). The prevalence of such respiratory illnesses is higher among the Navajo population  (Dawson, 2011.) 

Established Techniques to remove Uranium from water:

• Reverse Osmosis (RO): RO is a highly effective and widely used method. It utilizes a semi-permeable membrane that allows water molecules to pass through due to their small size. However, larger contaminants like uranium ions are rejected and remain on the concentrated side of the membrane. RO systems typically require pre-treatment steps like coagulation and filtration to remove suspended particles that could clog the membrane. While effective for uranium removal, RO can generate a brine stream containing concentrated contaminants, which requires proper disposal  (Romeyn et al., 2016.) 

• Ion Exchange (IX): This technique utilizes specialized resins containing exchange sites that attract and bind specific ions from the water passing through them. Specific resins with a high affinity for uranium ions are used for uranium removal. As contaminated water flows through the resin bed, uranium ions are captured onto the resin, while other ions like essential minerals, pass through relatively unaffected. When the resin becomes saturated with uranium, it must be regenerated or replaced to maintain treatment effectiveness. Regeneration typically involves using a concentrated salt solution to desorb the uranium from the resin. The spent regenerant solution, high in uranium content, requires proper management and disposal  (Vaaramaa et al., 2000.) 

• Electrodeionization (EDI): This method combines electrodialysis with ion exchange resins for a more efficient removal of ionic contaminants like uranium. It utilizes an electrical current to drive the migration of charged ions through ion exchange membranes. Contaminated water flows through a series of alternating compartments containing anion and cation exchange membranes. The electric current separates the ions, allowing water molecules to pass through while concentrating the contaminants in designated chambers. EDI can be a good option for high-salinity water where RO might be less effective  (Eurowater.) 

• Adsorption onto Novel Materials: Research is ongoing in developing new, highly selective adsorbent materials for uranium removal. These materials can be engineered to have a high affinity for uranium ions, potentially offering a more efficient and targeted approach compared to traditional ion exchange resins. Examples include functionalized nanoparticles, aerogel-based adsorbents, magnetic adsorbents, and bio-inspired materials  (Georgiou et al., 2023.) 

Pelham High School's well water testing project sparked a multi-year journey of awareness and education for students and the community from 2016 to the present. Originally focused on general water quality parameters, the project took a crucial turn when initial testing revealed the presence of arsenic and uranium. This discovery, particularly uranium, proved to be a wake-up call for many residents  (AAA.) 

Students, initially unaware of the potential dangers lurking in their own wells, became active ambassadors for water safety. Their surprise at finding these contaminants mirrored by the lack of awareness among some parents was a significant hurdle. Some parents, fearing negative test results impacting property values, resisted testing altogether. Students, determined to bridge this gap, actively engaged the community on this matter. They manned booths at events, presented data to the Board of Selectman, and utilized social media to spread awareness. A key turning point came when students compared public anxieties about arsenic, a well-known poison, to the relative obscurity of uranium in drinking water. By simply mentioning uranium, they witnessed a surge in testing requests, demonstrating the power of knowledge and clear communication.

The project's impact wasn't limited to the student body. Teachers themselves, particularly science instructors, expressed surprise at the prevalence of arsenic and uranium in local wells. Chemistry teachers delved deeper, researching the local presence of these elements. This high awareness rippled outwards, fostering a collective sense of responsibility for water safety within the Pelham community  (AAA.) 

While some samples revealed concerning levels of both arsenic and uranium, the presence of uranium truly underscored the potential dangers. Less than a fourth of all samples samples exceeded the maximum contaminant level (MCL) set by the EPA, with one reaching a staggering 1645 micrograms per liter. This extreme case served as a stark reminder of the potential health risks associated with contaminated well water.

Pelham High School's project transcended the purpose of a simple monitoring experiment. It catalyzed community-wide education and action on a critical environmental issue. By arming themselves with knowledge and a commitment to public health, students learned about water quality and became empowered agents of change in their community.