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Cadmium is a chemical element; it has symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of its compounds, and like mercury, it has a lower melting point than the transition metals in groups 3 through 11. Cadmium and its congeners in group 12 are often not considered transition metals, in that they do not have partly filled d or f electron shells in the elemental or common oxidation states. The average concentration of cadmium in Earth's crust is between 0.1 and 0.5 parts per million (ppm). It was discovered in 1817 simultaneously by Stromeyer and Hermann, both in Germany, as an impurity in zinc carbonate.
A pigment is a powder used to add color or change visual appearance. Pigments are completely or nearly insoluble and chemically unreactive in water or another medium; in contrast, dyes are colored substances which are soluble or go into solution at some stage in their use. Dyes are often organic compounds whereas pigments are often inorganic. Pigments of prehistoric and historic value include ochre, charcoal, and lapis lazuli.
A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or visible light, and cathodoluminescent substances which glow when struck by an electron beam in a cathode-ray tube.
Cadmium sulfide is the inorganic compound with the formula CdS. Cadmium sulfide is a yellow salt. It occurs in nature with two different crystal structures as the rare minerals greenockite and hawleyite, but is more prevalent as an impurity substituent in the similarly structured zinc ores sphalerite and wurtzite, which are the major economic sources of cadmium. As a compound that is easy to isolate and purify, it is the principal source of cadmium for all commercial applications. Its vivid yellow color led to its adoption as a pigment for the yellow paint "cadmium yellow" in the 1800s.
Lycopodium is a genus of clubmosses, also known as ground pines or creeping cedars, in the family Lycopodiaceae. Two very different circumscriptions of the genus are in use. In the Pteridophyte Phylogeny Group classification of 2016, Lycopodium is one of nine genera in the subfamily Lycopodioideae, and has from nine to 15 species. In other classifications, the genus is equivalent to the whole of the subfamily, since it includes all of the other genera. More than 40 species are accepted.
Cadmium is a naturally occurring toxic metal with common exposure in industrial workplaces, plant soils, and from smoking. Due to its low permissible exposure in humans, overexposure may occur even in situations where only trace quantities of cadmium are found. Cadmium is used extensively in electroplating, although the nature of the operation does not generally lead to overexposure. Cadmium is also found in some industrial paints and may represent a hazard when sprayed. Operations involving removal of cadmium paints by scraping or blasting may pose a significant hazard. The primary use of cadmium is in the manufacturing of NiCd rechargeable batteries. The primary source for cadmium is as a byproduct of refining zinc metal. Exposures to cadmium are addressed in specific standards for the general industry, shipyard employment, the construction industry, and the agricultural industry.
Cadmium telluride (CdTe) is a stable crystalline compound formed from cadmium and tellurium. It is mainly used as the semiconducting material in cadmium telluride photovoltaics and an infrared optical window. It is usually sandwiched with cadmium sulfide to form a p–n junction solar PV cell.
Nanotoxicology is the study of the toxicity of nanomaterials. Because of quantum size effects and large surface area to volume ratio, nanomaterials have unique properties compared with their larger counterparts that affect their toxicity. Of the possible hazards, inhalation exposure appears to present the most concern, with animal studies showing pulmonary effects such as inflammation, fibrosis, and carcinogenicity for some nanomaterials. Skin contact and ingestion exposure are also a concern.
USS Tercel (AM-386) was an Auk-class minesweeper acquired by the United States Navy for the dangerous task of removing mines from minefields laid in the water to prevent ships from passing.
Nanomaterials can be both incidental and engineered. Engineered nanomaterials (ENMs) are nanoparticles that are made for use, are defined as materials with dimensions between 1 and 100nm, for example in cosmetics or pharmaceuticals like zinc oxide and TiO2 as well as microplastics. Incidental nanomaterials are found from sources such as cigarette smoke and building demolition. Engineered nanoparticles have become increasingly important for many applications in consumer and industrial products, which has resulted in an increased presence in the environment. This proliferation has instigated a growing body of research into the effects of nanoparticles on the environment. Natural nanoparticles include particles from natural processes like dust storms, volcanic eruptions, forest fires, and ocean water evaporation.
Operation LAC was a United States Army Chemical Corps operation which dispersed microscopic zinc cadmium sulfide (ZnCdS) particles over much of the United States and Canada in order to test dispersal patterns and the geographic range of chemical or biological weapons.
Zinc cadmium sulfide is a mixture of zinc sulfide (ZnS) and cadmium sulfide (CdS). It is used for its fluorescent properties. Bioaccumulation of this chemical may occur along the food chain, for example in plants and in seafood. Long-term or repeated exposures are expected to have harmful effects on the kidneys, bones, and respiratory tract, resulting in kidney impairment, osteoporosis, and chronic inflammation of the respiratory tract.
The E48 particulate bomb was a U.S. biological sub-munition designed during the 1950s for use with the E96 cluster bomb.
Operation Polka Dot was a U.S. Army test of a biological cluster bomb during the early 1950s.
Operation Night Train was part of a series of chemical and biological warfare tests overseen by the Deseret Test Center as part of Project 112. The test was conducted near Fort Greely, Alaska from November 1963 to January 1964. The primary purpose of Night Train was to study the penetration of an arctic inversion by a biological aerosol cloud. The test's first purpose was to study the downwind travel and diffusion of this cloud when disseminated into different arctic meteorological regimes. All documents about Night Train were considered classified by the US military until 2002, when the Department of Defense (DOD) released medically relevant information of all the chemical and biological warfare agent tests conducted under Project 112.
Simultaneously extracted metals/Acid-volatile sulfide (SEM-AVS) is an approach used in the field of aquatic toxicology to assess the potential for metal ions found in sediment to cause toxic effects in organisms dwelling in the sediment. In this approach, the amounts of several heavy metals in a sediment sample are measured in a laboratory; at the same time, the amount of acid-volatile sulfide is determined. Based on the chemical interactions between heavy metals (SEM) and acid-volatile sulfide (AVS), the concentrations of these two components can be used to assess the potential for toxicity to sediment-dwelling organisms.
The Dorset Biological Warfare Experiments were a series of experiments conducted between 1953 and 1975 to determine the extent to which a single ship or aircraft could dispense biological warfare agents over the United Kingdom. The tests between 1971 and 1975 were known as the DICE trials. The tests were conducted by scientists from Porton Down, initially using zinc cadmium sulfide (ZnCdS) as a simulated agent. Early results clearly showed that one aircraft flying along the coast while spraying its agent could contaminate a target over 100 miles away, over an area of 10,000 square miles. This method of biological warfare attack and the test program to study it was known as the Large Area Coverage (LAC) concept.
Operation Sea-Spray was a 1950 U.S. Navy secret biological warfare experiment in which Serratia marcescens and Bacillus globigii bacteria were sprayed over the San Francisco Bay Area in California, in order to determine how vulnerable a city like San Francisco may be to a bioweapon attack.
Quantum dots (QDs) are semiconductor nanoparticles with a size less than 10 nm. They exhibited size-dependent properties especially in the optical absorption and the photoluminescence (PL). Typically, the fluorescence emission peak of the QDs can be tuned by changing their diameters. So far, QDs were consisted of different group elements such as CdTe, CdSe, CdS in the II-VI category, InP or InAs in the III-V category, CuInS2 or AgInS2 in the I–III–VI2 category, and PbSe/PbS in the IV-VI category. These QDs are promising candidates as fluorescent labels in various biological applications such as bioimaging, biosensing and drug delivery.
The cadmium cycle is a biogeochemical cycle of dispersion and deposition of cadmium through the atmosphere, biosphere, pedosphere, and hydrosphere. Cadmium typically exists in the environment with an oxidation state of +2 but can be found with an oxidation state of +1.
References
- U.S. National Research Council, Subcommittee on Zinc Cadmium Sulfide. Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion, (Google Books), National Academies Press, 1997,( ISBN 0309057833).