Antimony in soil

M. J. Cal-Prieto, A. Carlosena, J. M. Andrade, S. Muniategui, P. Lopez-Mahia and D. Prada, Study of chemical modifiers for the direct determination of antimony in soils and sediments by ultrasonic slurry sampling-ETAAS with D2 compensation, At. Spectrosc., 21(3), 2000, 93-99. 

This book is rooted in an informal discussion with three researchers. Dr Alatzne Carlosena, Dr Monica Felipe and Dr Maria Jesus Cal, after they had some problems measuring antimony in soils and sediments by electrothermal atomic absorption spectrometry. While we reviewed the results and debated possible problems, much like in a brainstorming session, I realized that some of their difficulties were highly similar to those found in molecular spectrometry (mid-IR spectroscopy, where I had some experience), namely a lack of peak reproducibility, noise, uncontrollable amounts of concomitants, possible matrix interferences, etc. 

Mierzwa and Dobrowolski [39 ] determined selenium using combined slurry sampling, microwave-assisted extraction and hydride atomic absorption spectrometry. Lopez-Garcia et al. [40] also used slurry sampling in the determination of arsenic and antimony in soil. 

Chikhalikar et al. [ 18,19] have discussed the speciation of antimony in soil extracts and soils. Asami et al. [20] have reviewed methods for the determination of antimony in soils. 

Merry and Zarcinas [33] have described a silver diethyldithiocarbamate method for the determination of arsenic and antimony in soil. The method involves the addition of sodium tetrahydroborate to an acid-digested sample which has been treated with hydroxylammonium chloride to prevent the formation of insoluble antimony compounds. The generated arsine and stib-ine react with a solution of silver diethyldithiocarbamate in pyridine in a gas washtube. Absorbance is measured twice at wavelengths of 600 and 504 nm. 

Chikhalikar et al. [18] have studied the speciation of thallium (and antimony) in soil. Lukaszewski and Zembrzuski [221] and Sagar [222] have discussed the determination of thallium in soils. 

Fuentes, E., Pinochet, H., De Gregori, L, and Potin-Gautier, M. (2003). Redox speciation analysis of antimony in soil extracts by hydride generation atomic fluorescence spectrometry. Spectrochim. Acta B 58, 1279-1289. 

Hammel W, Debus I and Steubing L (2000) Mobility of antimony in soil and its availability to plants. Chemosphere 41 1791-1798. 

Antimony is a rather rare element in nature. Its abundance in the earth s crust is about 0.2 ppm and the highest values among rocks are found in clays (1.5 ppm). There is usually a higher concentration of antimony in soils than in the parent materials (Kabata-Pendias and Pendias, 1984). According to Ainsworth et al. (1990a, 1991), it is a largely immobile element. The latter study also reported that close to an antimony smelter 80-90% of the total Sb contained in the soil was in an immobile chemical form which accumulated in a thin (<5 cm) shallow horizon. Only a small fraction moved downward after being converted to a mobile form. 

Nixon277 compared atomic absorption spectroscopy, flame photometry, mass spectroscopy, and neutron activation analysis as methods for the determination of some 21 trace elements (<100 ppm) in hard dental tissue and dental plaque silver, aluminum, arsenic, gold, barium, chromium, copper, fluoride, iron, lithium, manganese, molybdenum, nickel, lead, rubidium, antimony, selenium, tin, strontium, vanadium, and zinc. Brunelle 278) also described procedures for the determination of about 20 elements in soil using a combination of atomic absorption spectroscopy and neutron activation analysis. 

This technique has been applied to the determination of arsenic, selenium, organocompounds of arsenic, mercury and tin in soils, carbohydrates, total sulphur, arsenic, antimony, bismuth, selenium and organocompounds of mercury, tin and silicon in non-saline sediments, arsenic, bismuth, selenium or organotin compounds in saline sediments and arsenic and selenium in sludges. 

It is seen by examination of Table 1.11(b) that a wide variety of techniques have been employed including spectrophotometry (four determinants), combustion and wet digestion methods and inductively coupled plasma atomic emission spectrometry (three determinants each), atomic absorption spectrometry, potentiometric methods, molecular absorption spectrometry and gas chromatography (two determinants each), and flow-injection analysis and neutron activation analysis (one determinant each). Between them these techniques are capable of determining boron, halogens, total and particulate carbon, nitrogen, phosphorus, sulphur, silicon, selenium, arsenic antimony and bismuth in soils. 

The optimal reaction conditions for the generation of the hydrides can be quite different for the various elements. The type of acid and its concentration in the sample solution often have a marked effect on sensitivity. Additional complications arise because many of the hydrideforming elements exist in two oxidation states which are not equally amenable to borohydride reduction. For example, potassium iodide is often used to pre-reduce AsV and SbV to the 3+ oxidation state for maximum sensitivity, but this can also cause reduction of Se IV to elemental selenium from which no hydride is formed. For this and other reasons Thompson et al. [132] found it necessary to develop a separate procedure for the determination of selenium in soils and sediments although arsenic, antimony and bismuth could be determined simultaneously [133]. A method for simultaneous determination of As III, Sb III and Se IV has been reported in which the problem of reduction of Se IV to Se O by potassium iodide was circumvented by adding the potassium iodide after the addition of sodium borohydride [134], Goulden et al. [123] have reported the simultaneous determination of arsenic, antimony, selenium, tin and bismuth, but it appears that in this case the generation of arsine and stibene occurs from the 5+ oxidation state. 

Arsenic and antimony are Group VB elements and both occur in soils predominantly in - -3 and - -5 oxidation states and they have similar redox and sorption behaviour. The oxidized forms are rather insoluble in soils and the reduced forms much more soluble. 

Serfor-Armah, Y., Nyarko, B.J.B., Adotey, D.K. et al. (2006) Levels of arsenic and antimony in water and sediment from Prestea, a gold mining town in Ghana and its environs. Water Air and Soil Pollution, 175(1-4), 181-92. 

Other basic dyes have been used in the determination of thallium in soils [61], antimony and cadmium [27], lead and its alloys [29,31], zinc and its alloys [28], and tungsten [32]. 

Antimony has geochemical behavior similar to arsenic, as it occurs most commonly in the +3 (antimonite) and +5 (antimonate) oxidation states and also tends to associate with sulfides in rocks, sediments, and soils. In soil solutions, the Sb and Sb oxidation states are stable under reducing and oxidizing conditions, respectively. 

In oxidizing soil solutions, Sb is likely to form the anionic molecule Sb(OH)6, above pH 4, and SbCOH) in more acid solution. As an anion, Sb(OH)6 may adsorb by ligand exchange on oxides and silicate clays. Antimony associates with ferric hydroxide in soils, perhaps a result of chemisorption of the anion on this mineral. 

Antimony is a common pollutant of soils in industrial and mining sites. Its mobility in soils is rated as medium, with reducing conditions associated with poor drainage probably lessening mobility. 

Silver is the sixty-third most abnndant metal in Earth s crust the average concentration of silver in water is 0.5 ppb, in soil it is 10 ppb. It is fotmd naturally as native metal or in ores in which it is complexed with lead, copper, tellurium, mercury, arsenic, or antimony. Silver is fonnd mainly throughont the Americas, Japan, Anstraha, and central Europe. Extraction is by amalgamation and displacement (nsing mercnry), solution, or smelting methods. 

Gel chromatography, which depends primarily on molecular weight differences, has been used (a) to separate mono-, di-, and tri-alkylated phosphates and (b) for the estimation of organic phosphates in soil. It is interesting to note a reversal of roles tri-n-octylphosphine oxide-treated cellulose has successfully separated gold, antimony, and thallium. ... 

Antimony oxides are released into the environment from smelters, coal-fired power plants and volcanoes (Zoller 1984). Lantzy and Mackenzie (1979) estimated that 3.8x 10 g per year were released globally into the environment from anthropogenic activities. Another important source is vehicle emissions (Dietl etal. 1996). Antimony is transported in the atmosphere over long distances - for instance, from Central Europe to Norway - and accumulates there in soils, plants, mosses, etc. (Steinnes 1997). About 4 tons of antimony are deposited on the Arctic from northern Europe annually... 

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