China
Africa
Explore chapters and articles related to this topic
Arsenic
Published in Pankaj Chowdhary, Abhay Raj, Contaminants and Clean Technologies, 2020
Kiran Gupta, Alka Srivastava, Amit Kumar
Arsenic occurs in soil as inorganic and organic forms in which the inorganic forms are more prevalent. Most of the inorganic forms are found in minerals. The major part of As in soil occurs as mineral forms. However, the organic form of As is mostly present in living organisms because of the intake of As minerals. There are about 300 forms of As-enriched minerals, viz., arsenates, sulfides, sulfosalts, arsenites, arsenides, native elements, including metal alloys. The major mineral forms of As are depicted in Table 10.1. Among them, sulfide (e.g., arsenopyrite, pyrite, realgar, and loellingite) and arsenate minerals (e.g., scorodite, yukonite, and beudantite) are the mostly occurring soil-bound mineral forms (Kossoff and Hudson-Edwards, 2012), while other minerals are formed during the weathering process. When organo As compounds enter the food chain, inorganic arsenic gets converted into less-toxic organic methylated forms such as monomethyl arsine (MMA), dimethylarsine (DMA), and trimethylarsine (TMA) (Kossoff and Hudson-Edwards, 2012). Some other organic forms were also generated during World War I, suchas lewisite, cacodylic acid, and adamsite (Ellison, 2007). Other forms of organic arsenic are found in seafood, like arsenobetaine and arsenocholine (Hopenhayn, 2006).
List of Chemical Substances
Published in T.S.S. Dikshith, and Safety, 2016
Arsenate minerals are minerals containing the arsenate (AsO43-) anion group—arsenic acid, calcium arsenate, chromated copper arsenate, copper(II) arsenate, lead hydrogen arsenate, monosodium methyl arsenate, potassium arsenate, arsenates, arsenic minerals, arsenical herbicides, arsenides, and arsenites. Arsenate resembles phosphate in many respects, since arsenic and phosphorus occur in the same group.
Surficial arsenic redistribution above gold-mineralised zones in East Otago, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2019
Frances Blake, Kacee Grant, Doug MacKenzie, James Scott, Dave Craw
Arsenolite can precipitate from As(III) bearing solutions, but typically only after evaporative concentration in a setting such as that of East Otago (Figure 10A–C; 11; Kerr et al. 2015; Craw 2017). Further oxidation produces As(V) ions, which is the most common form of dissolved As in the surficial environment, and this As can be adsorbed to HFO, co-precipitate with that HFO, and/or precipitate as a ferric arsenate mineral. The principal ferric arsenate mineral is variably-crystalline scorodite (FeAsO4.2H2O), which is common in oxidised As-rich rocks in Otago Schist (Figure 8B; Craw et al. 2003; Craw and Kerr 2017; Craw 2017). Evaporative concentration of As(V) solutions can be important for precipitation of scorodite at high pH (>7), but under weakly acidic conditions, scorodite and associated ferric arsenate compounds are relatively insoluble (Krause and Ettel 1989). In contrast, HFO is highly insoluble at any pH >3 and so adsorption or co-precipitation of As(V) with HFO can occur under most conditions likely to have prevailed in groundwaters near the East Otago unconformities where circumneutral pH prevailed (Craw and Kerr 2017).