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Latest Issue
Oct 2023

Photonics flows into freshwater monitoring

Amid the climate-change-driven stories about drought in California and floods in the Nevada desert, the New York Times recently reported that decades of agriculture and residential development have drained groundwater from U.S. aquifers faster than it could be naturally restored.

Water has even become a growing undercurrent in the media buzz surrounding AI language generators, such as ChatGPT. Research led by the University of California at Riverside and published in the journal arXiv aimed to quantify AI’s growing water footprint. In their abstract, the researchers claimed that merely training GPT-3 in Microsoft’s state-of-the-art data centers can directly consume 700,000 L or ~185,000 gal of clean fresh water. The paper further asserts that in 2021, Google’s self-operated U.S. data centers consumed 12.7 billion liters of fresh, potable water, equating to ~3.4 billion gallons, for on-site cooling.

As media headlines regarding the accelerating consumption of clean drinking water have multiplied, so have those concerning the safety and quality of the water. Dire shorthand terms like “forever chemicals” have become increasingly familiar. In June, for example, 3M agreed to pay between $10.3 and $12.5 billion over 13 years to resolve claims that state it has polluted drinking water supplies with per- and polyfluorinated substances (PFAS), which have both been linked to health problems and do not naturally degrade in the environment.

Such settlements provide a cautionary tale, not only for the general population that relies on clean water, but also for corporations and industries that are introducing other health-adverse materials into our supply. Some analysts believe that microplastics could become the next PFAS equivalent, though, unlike PFAS, microplastics will not yield an obvious source on which to pin the blame.

Defined as particles of plastic measuring between 100 nm and 5000 µm, the microplastics in our environment primarily derive from the laundering of synthetic clothing, the wear on automotive tires, and the exfoliants in personal care products. Though the degradation of plastic bags and bottles is considered to be a secondary source, it is blamed for the majority of microplastics found in the oceans.

Barring the option to stop microplastics at their source, government officials have instead focused on gathering more data and monitoring how, where, and in what volumes microplastics are appearing in the globe’s freshwater sources.

In this issue, contributing editor James Schlett explores how photonic technologies and techniques are contributing to this endeavor. In California, for example, state water officials recruited two dozen laboratories to evaluate analytical methods for detecting waterborne microplastics. Several photonic technologies proved their efficacy, including fiber sensors, hyperspectral imaging, optical photothermal IR spectroscopy, among others. But both Raman and IR spectroscopy floated to the top of the list.

In its next phase, California’s initiative will begin collecting sampling data from about 30 large water systems. Meanwhile, New Jersey and New York City are lending further momentum with similar microplastics-monitoring proposals. The growing demand for accurate in situ water monitoring will yield a rising tide of demand for photonic tools.