A true random‐number generator (TRNG) and a nonlinear feedback shift register (NFSR) are combined to create a new type of TRNG. This TRNG is based on the intrinsic stochasticity of threshold switching behavior in a Pt/HfO2/TiN memristor and an NFSR circuit. Considering the transition rate of the hopping process, the stochasticity of the delay time can be attributed to the phonon‐assisted hopping process. This novel TRNG passes all 15 National Institute of Standards and Technology randomness tests without post‐processing steps, proving its performance as a hardware security application. By combining the TRNG with the NFSR, the bit generation rate is further improved, allowing it to be used for high‐speed applications.

Elemental mercury, Hg(0), is ubiquitous in water and involved in key Hg biogeochemical processes. It is extensively studied as a purgeable dissolved species, termed dissolved gaseous mercury (DGM). Little information is available regarding nonpurgeable particulate Hg(0) in water, Hg(0) bound to suspended particulate matter (SPM), which is presumably present due to high affinity of Hg(0) adsorption on solids. By employing stable isotope tracer and isotope dilution (ID) techniques, we investigated the occurrence and quantification of particulate Hg(0) after Hg(0) being spiked into natural waters, aiming to provide firsthand information on particulate Hg(0) in water. A considerable fraction of 201 Hg(0) spiked in water (about 70% after 4 h equilibration) was bound to SPM and nonpurgeable, suggesting the occurrence of particulate Hg(0) in natural waters. A scheme, involving isotope dilution, purge and trap, and inductively coupled plasma mass spectrometry detection, was proposed to quantify particulate Hg(0) by the difference between DGM and total Hg(0), determined immediately and at equilibration after spiking ID Hg isotope, respectively. The application of this newly established method revealed the presence of particulate Hg(0) in Florida Everglades water, as the determined DGM levels (0.14 to 0.22 ng L −1 ) were remarkably lower than total Hg(0) (0.41 to 0.75 ng L −1 ). ■ INTRODUCTIONMercury (Hg), as a global pollutant, has received great attention due to accumulation and biomagnification of its methylation product, methylmercury (MeHg), through aquatic food chains. Elemental mercury, Hg(0), is an important species in Hg cycling, as considerable levels of Hg(0) are present in all environmental media, including the atmosphere (up to 95% of Hg being Hg(0)), 1,2 soil 3 and sediment, 4 and water. 5 Previous studies have shown that dissolved gaseous Hg (DGM), being mainly composed of Hg(0), is a ubiquitous form of inorganic Hg in seawater, 5,6 fresh water, 7−9 and groundwater. 10,11 Hg(0) in water is involved in key processes of Hg biogeochemical cycling including air−water exchange, 12 oxidation−reduction, 8 and methylation−demethylation. 13 Hg(0) can be oxidized to Hg(II) by both chemical and biological processes in aquatic environments, 6,7,14−17 and reduction of Hg(II) can produce Hg(0) in water, through photochemical processes, 6,18−20 enzymatic catalysis by mercury-resistant microorganisms, 7,21−23 or geochemical reactions involving humic acids and mineral-associated ferrous ion. 24−27 It was recently observed that dissolved Hg(0) could be methylated by Desulfovibrio desulf uricans ND132 to form MeHg, 13,14 which was a previously unrecognized pathway in Hg cycling. MeHg photodegradation in natural waters could also produce Hg(0) as an end product. 28−30 It should be noted that Hg(0) can be present in two forms in water, liquid Hg(0) droplet and aqueous Hg(0) (denoted as Hg(0) aq for distinction in some cases), with the former being rarely observed in uncontaminated natural waters and the latter being u...

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