Per- and polyfluoroalkyl substances, commonly known as PFAS, are a class of chemicals included in many commercial products. However, they raise serious concern for their potential environmental and health impacts. This has led to the introduction of stringent regulations in both the United States and Europe, which create substantial challenges for current wastewater treatment technology. The image on the cover represents the two most common PFAS, namely PFOS and PFOA, dispersed in water.

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Lake surface water temperature is rising across the globe. Less than half of lake warming is due to surface air temperature (SAT) change, and accelerated evaporation causes slower lake warming compared to SAT. The image on the cover shows a composite of two Landsat images captured in July of different years (1987 for northeast and 2016 for southwest) from the same location (Ozero Neyto, Russia, and its surrounding sprawling lakes).

See Tong et al.

Cyanobacterial toxins such as microcystin produced by these blooms threaten water resources around the globe. Regions with the highest risk for elevated microcystin concentrations are expected to shift to higher latitudes under global warming. The image on the cover shows cyanobacterial scum from a harmful algal bloom in Milford Lake, located in Kansas, USA.

See Merder et al.

Most of the global lithium is produced from brine using large evaporation ponds, which negatively impacts ecosystems and limits production. Chen and colleagues report an interfacial evaporation method for swift and selective extraction of lithium from saline water using twisted cellulose fibre crystallizers. The cover image depicts the mineral crystals formed on the fibres.

See Chen et al.

The image on the cover shows one of the many ceramic drainage pipes that have been unearthed from the late-Neolithic walled site of Pingliangtai in Henan, China. Although small in size, mostly 20–30 cm in diameter and 30–40 cm in length, these pipes are valuable fossil evidence of the extraordinary technological response to the monsoonal floods in prehistoric China.

See Li et al.

A hand-held device filled with a porous metal–organic framework, MOF-303, is capable of harvesting water from desert air without any power or energy input aside from the ambient sunlight at Death Valley, a location known for being the hottest place on Earth and the driest desert in North America. The cover shows a prototype of the device positioned at Dante’s View — within Death Valley — in California.

See Song et al.

Conventional techniques for precipitating highly soluble salts (for brine reduction or elimination) typically require phase change of water via evaporation or freezing, which is energy intensive. Zhang and colleagues report a process, namely electrodialysis crystallization, to precipitate soluble salts via forcing the salt concentration beyond solubility by the mechanism of electrodialysis. The cover image shows the sodium sulfate crystals forming in electrodialytic crystallization.

See Zhang et al.

Despite having been around for several decades, wastewater-based epidemiology only came to prominence only during the COVID-19 pandemic, during which it has been used across the globe to monitor the spread of the infection. The approach could potentially be extended to study the spread of other pathogens but also the lifestyle of entire populations, including drug use or dietary habits. The image on the cover shows the amount of viruses and chemicals that can be found in wastewater.

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Access to safe and reliable drinking water is essential for public health. However, aging infrastructure combined with years of disinvestment has led to fragile water systems in many areas, causing a range of impacts on community residents and society as a whole. Boil water alerts (BWAs) are used to notify residents when the drinking water is or could be contaminated with pathogens. In areas with poor water systems, a high frequency of BWA may add additional challenges to residents already facing disproportionate burdens. Kim and colleagues examined the relationship between BWAs and the attendance rate in public schools in Jackson, Mississippi, and found that unexcused absence rates increase by 1–10% each time a BWA is issued. The image on the cover shows impacted areas across Jackson, Mississippi.

See Kim et al.

Water is central to sustainable development, and is crucial for public health as well as socio-economic development and healthy ecosystems. Yet progress on water-related goals and targets is nowhere near where it should be. On 22–24 March 2023, the world will gather in New York for the UN 2023 Water Conference to create momentum for accelerated action to combat the global water challenges. The cover image, with the word water in some of the different languages spoken throughout the United Nations, represents the unifying power of our global water resources.

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Groundwater is an essential resource for humans and society, providing drinking water, irrigation and other services. Unfortunately, it may also contain contaminants such as arsenic. Arsenic mobilisation and mobility in groundwater can have a significant impact on human health and the environment. Low-arsenic, high-iron aquifers are often considered contamination-free and a feasible exploitation option. Nghiem and colleagues show that limited sulfate reduction can accelerate groundwater arsenic contamination, even in high-iron aquifers. The image on the cover shows pumping groundwater used to irrigate one typical paddy soil farmland in Bangladesh, which is where the data by Nghiem and colleagues were collected.

See Nghiem et al. and News & Views by Planer-Friedrich

Water is not only necessary for life. It is also at the heart of human civilization. Throughout history, societies have progressed by improving access to clean water for drinking, sanitation and agriculture as well as by removing contaminants from water to reduce the effects on the environment and to improve public health. We now face new challenges due to reduced water availability and increasing demand. Challenges that can only be addressed by the integrated contribution of natural, social sciences and engineering. The image on the cover was chosen to represent the complex interaction of humans with water in the changing environment.

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