From Tap to Tide: Tracking Contaminants Across Five Major Water Sources

1 We benefit from water’s solubility every day – from our morning cup of tea or coffee, to washing our hands, clothes or dishes – but water’s propensity for dissolving substances also poses a problem. Some contaminants readily dissolve in water, while others remain suspended as insoluble particles. These soluble contaminants include fertilizers, nitrates, pharmaceuticals and per- and polyfluoroalkyl substances (PFAS), and are often found in groundwater and surface water, while insoluble pollutants such as microplastics and pathogens are frequently detected in seawater, rainwater and lakes. These substances can disrupt aquatic ecosystems, cause disease outbreaks and enter the food chain, threatening both environmental and human health. Furthermore, the nature of the water cycle means that contaminants travel and accumulate between different water sources. Analytical techniques like ion chromatography, quantitative PCR, and gas chromatography-mass spectrometry (GC-MS) are routinely used by researchers and regulators to detect threats, such as excess nutrient levels producing algal blooms or microplastic bioaccumulation. This listicle will highlight how the primary contaminants affecting various water sources are detected by such analytical technology, which enables timely interventions that help protect our water sources and the broader environment. 1. Seawater: Petroleum hydrocarbons, sewage and microplastics Petroleum hydrocarbons (PHCs) introduced into marine waters through, for example, oil spills, can be lethal to oceanic wildlife. For instance, pelagic birds that get entrapped in oil slicks are unable to fly and ultimately drown, while ingestion of PHCs slowly poisons other marine life. Although only major spills are widely publicized, such as the 2010 Deepwater Horizon incident that released over 200 million gallons into the Gulf of Mexico,1 smaller spills are also common, with thousands reported annually in US waters. Detecting PHCs helps assess their concentration and bioaccumulation potential, both of which affect marine ecosystems and human health. PHC analysis is typically performed using gas chromatography with flame ionization detection (GC-FID), which separates hydrocarbons based on volatility and quantifies them by measuring ions produced during combustion. This technique provides essential data for assessing environmental impact, regulatory compliance and cleanup effectiveness. From Tap to Tide: Tracking Contaminants Across Five Major Water Sources Laura Hemmingham, PhD Listicle FROM TAP TO TIDE: TRACKING CONTAMINANTS ACROSS FIVE MAJOR WATER SOURCES 2 Listicle Additional contaminants in seawater include excess nutrients from sewage dumping and agricultural practices. Substances like nitrates and phosphates from agricultural runoff can lead to algal blooms on the ocean surface, which block sunlight, reduce oxygen levels and hinder the growth of seabed plants. These factors ultimately disrupt the marine food chain. Detection techniques for these substances include flow injection analysis (FIA), whereby a water sample is exposed to a stream of chemicals that react with the target compound (e.g., nitrates). The mixture then flows through a detector, where a color change indicates the level of nitrates, allowing scientists to monitor pollution sources and protect marine ecosystems. Lastly, some of the most prevalent and most researched seawater contaminants are microplastics and smaller nanoplastics. Widespread throughout the water cycle, microplastics originate from discarded plastic waste, breaking down into particles smaller than five millimeters that enter and accumulate in the food chain. Their presence in biological tissues, including in humans, is of great concern and has been linked to health risks from organ dysfunction and neurotoxicity to reproductive and developmental disorders.2, 3 However, increasingly efficient and sophisticated detection techniques are continuously being developed, often combining spectroscopy – Fourier transform infrared spectroscopy (FTIR) and Raman – and microscopy (light and scanning electron) to monitor both health and environmental risks. 2. Rainwater: Microplastics and airborne pollutants During evaporation, oceanic microplastics become trapped in water droplets, gather in clouds and fall with precipitation across the globe, with terrestrial environments estimated to have between 4–23 times more microplastic deposition than marine environments.4 They are ubiquitous, from the peak of Everest to the depths of the Amazon basin, entering water sources and even the air we breathe. Though detectable by spectroscopy and microscopy, their widespread, fragmenting nature makes their removal a global challenge. Due to the plastics’ resistance to degradation, if left unaddressed, current pollution in our environment will persist for hundreds or even thousands of years.4 Removal strategies include physical (e.g., adsorption, filtration), chemical (e.g., chlorination, photodegradation) and biological (e.g., biodegradation, ingestion) approaches.4 Rainwater is also affected by airborne pollutants, including gases like sulfur dioxide (SO2) and nitrogen oxides (NOx), which are emitted primarily through fossil fuel combustion. These gases dissolve into precipitation and form acid rain (pH <5.6), with the most acidic rain, comparable to stomach acid (pH 1.87), recorded in the Scottish Highlands in 1983. Acid rain damages ecosystems by lowering soil and water pH, weakening trees, consequently increasing their disease vulnerability.5 It can be monitored with ion chromatography, which converts SO2 in rainwater to sulfate ions, separates them in a column and measures their concentration using a conductivity detector. Though the prevalence of acid rain has declined in many regions, monitoring remains essential. 3. Surface water: From pathogens to pesticides In addition to pollutants arriving by precipitation, other surface water contaminants, from pathogens to pesticides, also endanger environmental and human health. Pathogens such as E. coli and Salmonella can enter lakes, rivers and ponds through unmanaged septic waste dumping as well as animal waste exposure, with waterborne diseases resulting in almost two million deaths annually.6 FROM TAP TO TIDE: TRACKING CONTAMINANTS ACROSS FIVE MAJOR WATER SOURCES 3 Listicle Detection methods such as qPCR are widely used, allowing scientists to amplify and quantify microbial DNA, even at very low concentrations. This makes it possible to detect contamination before outbreaks occur. For instance, water-based surveillance of COVID-19 in Canadian long-term care facilities showed the application of qPCR to detect pathogens in site-specific wastewater, serving as an early-warning signal.7 In addition to molecular diagnostics, labs also employ chromogenic and fluorogenic culture techniques, which use specialized growth media to visually differentiate pathogenic strains based on enzyme activity. These methods provide a complementary and cost-effective approach for monitoring routine water samples. Other analytical solutions include immunoassays, such as enzyme-linked immunosorbent assays (ELISA) and biochemical panels such as an analytical profile index (API), which together offer a comprehensive toolkit for identifying a broad range of microbial threats in environmental water. Taken together, these technologies allow for sensitive, scalable and reliable pathogen surveillance, helping protect both public health and aquatic ecosystems. Surface water is also prone to pesticide contamination. Pesticides are commonly used in agriculture and can be carried by runoff into rivers and lakes. These chemicals disrupt aquatic ecosystems and have been associated with developmental and hormonal issues in wildlife and humans.8 ELISA and liquid chromatography- mass spectrometry (LC-MS) are frequently used to monitor these compounds. ELISA uses antibodies to detect specific molecules, while LC-MS offers high sensitivity and specificity by separating and identifying molecules based on their mass and structure. 4. Groundwater: Fertilizers, heavy metals and PFAS Similarly to their effect in marine environments, fertilizers pose a major problem for groundwater as they leach through soil into underlying water sources. From there, they can enter drinking water and cause conditions like cancers and methemoglobinemia,9 making careful monitoring vital. This can be done using techniques such as FIA and ion chromatography. Heavy metal contamination in groundwater can result from geogenic processes (weathering, rock leaching) and human activities (mining, industrial emissions), involving elements like zinc, arsenic, lead, mercury, iron and copper. Monitoring and removal help prevent environmental infiltration and accumulation, protect ecological and human health and avoid conditions such as hypertension, cancer and lung disease.10 Inductively coupled plasma mass spectrometry (ICP-MS) offers high sensitivity, detecting metals at parts-per-trillion levels by ionizing samples and measuring mass-to-charge ratios. Atomic absorption spectrometry (AAS), while less sensitive, remains widely used for quantifying metals due to its simplicity, reliability and cost-effectiveness. PFAS, also known as forever chemicals, are man-made chemicals that are highly persistent in the environment due to their resistance to degradation. They enter groundwater through landfill runoff, industrial sites and firefighting foams, and long-term exposure is associated with thyroid disorders, immune system suppression and cancer. LC-MS/MS (liquid chromatography-tandem mass spectrometry) is commonly used to detect and quantify PFAS compounds due to the technique’s high specificity and sensitivity, even in complex matrices like groundwater. 5. Tap water: Heavy metals and PFAS Despite identification by ICP-MS and resulting treatment, tap water may still contain residual contaminants, particularly in regions with aging infrastructure or limited regulation. Lead, copper and other heavy FROM TAP TO TIDE: TRACKING CONTAMINANTS ACROSS FIVE MAJOR WATER SOURCES 4 Listicle metals can leach from old plumbing systems and accumulate, posing risks such as neurodevelopmental disorders in children and kidney damage in adults.11 Therefore, it is also important to use the aforementioned detection techniques in tap water analysis. Similarly, despite monitoring groundwater sources, PFAS contamination in tap water is another major concern, especially in surrounding industrial areas. Their strong carbon-fluorine bonds allow them to persist through conventional water treatment processes.12 Consequently, LC-MS/MS is required for further PFAS analysis in treated water, helping to inform regulatory action and mitigation efforts. Conclusion: A clearer view of water contaminants Water's ability to dissolve and transport substances makes it essential to monitor contaminants across all stages of the water cycle. From seawater and rain to groundwater and household taps, pollutants like microplastics, heavy metals and PFAS pose serious risks to ecosystems and human health. Fortunately, modern analytical techniques, including chromatography, spectroscopy and microscopy, enable scientists to detect and respond to these threats. Nevertheless, continued surveillance, research and innovation are crucial to ensuring our water sources remain safe and sustainable for future generations. Sponsored by References 1. Ramseur JL. Deepwater Horizon Oil Spill: The Fate of the Oil. 2011. https://digital.library.unt.edu/ark:/67531/ metadc491467/m1/1/high_res_d/R41531_2011Jan05.pdf 2. Dubey I, Khan S, Kushwaha S. Developmental and reproductive toxic effects of exposure to microplastics: A review of associated signaling pathways. Front Toxicol. 2022;4. doi: 10.3389/ftox.2022.901798 3. Wang M, Wu Y, Li G, Xiong Y, Zhang Y, Zhang M. The hidden threat: Unraveling the impact of microplastics on reproductive health. Sci Total Environ. 2024;935:173177. doi: 10.1016/j.scitotenv.2024.173177 4. Ahmed R, Hamid A, Krebsbach S, He J, Wang D. Critical review of microplastics removal from the environment. Chemosphere. 2022;293(133557). doi: 10.1016/j.chemosphere.2022.133557 5. Singh A, Agrawal M. Acid rain and its ecological consequences. J Environ Biol. 2008;29(1):15-24. PMID: 18831326 6. Manetu WM, Karanja AM. Waterborne disease risk factors and intervention practices: A review. Open Access Library Journal. 2021;8: e7401. doi: 10.4236/oalib.1107401 7. Pang X, Lee BE, Gao T, et al. Early warning COVID-19 outbreak in long-term care facilities using wastewater surveillance: correlation, prediction, and interaction with clinical and serological statuses. Lancet Microbe. 2024;5(10):100894. doi: 10.1016/s2666-5247(24)00126-5 8. Colborn T, Saal FSV, Soto AM. Developmental effects of endocrine-disrupting chemicals in wildlife and humans. Environ Health Perspect. 1993;101(5):378. doi: 10.2307/3431890 9. Ward MH. Too much of a good thing? Nitrate from nitrogen fertilizers and cancer. Rev Environ Health. 2009;24(4). doi: 10.1515/reveh.2009.24.4.357 10. Ullah Z, Rashid A, Ghani J, et al. Groundwater contamination through potentially harmful metals and its implications in groundwater management. Front Environ Sci. 2022;10. doi: 10.3389/fenvs.2022.1021596 11. Nkwunonwo UC, Odika PO, Onyia NI. A review of the health implications of heavy metals in food chain in Nigeria. Sci World J. 2020;2020:1-11. doi: 10.1155/2020/6594109 12. Tshangana CS, Nhlengethwa ST, Glass S, et al. Technology status to treat PFAS-contaminated water and limiting factors for their effective full-scale application. Npj Clean Water. 2025;8(1). doi: 10.1038/s41545-025-00457-3 About the author: Laura Hemmingham is a scientific content producer for Technology Networks. She holds a PhD in Environmental Sciences from Royal Holloway, University of London. Her academic journey has been fueled by a broad interest in the life sciences and her work aims to support scientific literacy while highlighting the real-world impact of research and innovation.