This review confirms positive impacts of sanitation on aspects of health. Evidence gaps remain and point to the need for research that rigorously describes sanitation implementation and type of sanitation interventions.
Solute–free zones, termed “exclusion zones” are routinely seen next to hydrophilic surfaces in aqueous solution. Here we report similar zones next to various metals. The largest, approximately 200 µm in width, was found adjacent to zinc. Other reactive metals, including aluminum, tin, lead, and tungsten exhibited distinct but smaller exclusion zones, while precious metals such as platinum and gold did not produce any. Electrical potential measurements showed positive potentials within the exclusion zones, while pH measurements revealed an abundance of OH− groups in the aqueous regions beyond the exclusion zones. A correspondence was found between exclusion-zone size and the respective metal’s position within the galvanic series. The presence of these interfacial exclusion zones is unexpected, and may shed new light on electrochemical processes taking place at metal interfaces.
Earlier, we reported solute-free “exclusion zones” in aqueous media next to various metal surfaces. Here we explore the effect of connecting zinc, which ordinarily shows a large exclusion zone, to platinum, which ordinarily does not. We found the connecting the two metals diminished the exclusion zone next to zinc, while it increased the exclusion zone next to platinum. Disconnecting resulted in return to control values. These effects were largest when the metals were juxtaposed relatively closely, and became smaller with increasing separation. The underlying mechanisms are considered.
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