Arsenic in soil

The procedure followed describes methods for the determination of total levels, and in certain cases, available amounts of trace elements in soils. The determination of arsenic in soil by hydride generation AAS is included. 

The mobility of arsenic compounds in soils is affected by sorp-tion/desorption on/from soil components or co-precipitation with metal ions. The importance of oxides (mainly Fe-oxides) in controlling the mobility and concentration of arsenic in natural environments has been studied for a long time (Livesey and Huang 1981 Frankenberger 2002 and references there in Smedley and Kinniburgh 2002). Because the elements which correlate best with arsenic in soils and sediments are iron, aluminum and manganese, the use of Fe salts (as well as Al and Mn salts) is a common practice in water treatment for the removal of arsenic. The coprecipitation of arsenic with ferric or aluminum hydroxide has been a practical and effective technique to remove this toxic element from polluted waters... 

Smith E, Naidu R, Alston AM (2002) Chemistry of inorganic arsenic in soils II Effect of phosphorus, sodium, and calcium on arsenic sorption. J Environ Qual 31 557-563... 

Although arsenic is not an essential plant nutrient, small yield increases have sometimes been observed at low soil arsenic levels, especially for tolerant crops such as potatoes, com, rye, and wheat (Woolson 1975). Arsenic phytotoxicity of soils is reduced with increasing lime, organic matter, iron, zinc, and phosphates (NRCC 1978). In most soil systems, the chemistry of As becomes the chemistry of arsenate the estimated half-time of arsenic in soils is about 6.5 years, although losses of 60% in 3 years and 67% in 7 years have been reported (Woolson 1975). Additional research is warranted on the role of arsenic in crop production, and in nutrition, with special reference to essentiality for aquatic and terrestrial wildlife. 

Attention focused on inorganic arsenical pesticides after accumulations of arsenic in soils eventually became toxic to several agricultural crops, especially in former orchards and cotton fields. Once toxicity is observed, it persists for several years even if no additional arsenic treatment is made (Woolson 1975). Poor crop growth was associated with bioavailability of arsenic in soils. For example, alfalfa (Medicago sativa) and barley (Hordeum vulgare) grew poorly in soils con-... 

Soils amended with arsenic-contaminated plant tissues were not measurably affected in C02 evolution and nitrification, suggesting that the effects of adding arsenic to soils does not influence the decomposition rate of plant tissues by soil microorganisms (Wang et al. 1984). The half-life of cacodylic acid is about 20 days in untreated soils and 31 days in arsenic-amended soils (Hood 1985). Estimates of the half-time of inorganic arsenicals in soils are much longer, ranging from 6.5 years for arsenic trioxide to 16 years for lead arsenate (NRCC 1978). 

This technique has been applied to the determination of boron, total phosphorus and arsenic in soil, antimony and organosilicon compounds in non-saline sediments, arsenic in saline sediments and silicon and arsenic in sludges. 

Odanake et al. [1] have reported the application of gas chromatography with multiple ion detection after hydride generation with sodium borohydride to the determination of mono and dimethyl arsenic compounds, trimethyl arsenic oxide and inorganic arsenic in soil and sediments. Recoveries in spiking experiments were 100-102% (mono and dimethyl arsenic compounds and inorganic arsenic) and 72% (trimethyl arsenic oxide). 

One factor has been overlooked in this reversion to seaweed use. Seaweed naturally contains high levels of arsenic, typically between 20 and 100 mg kg" dry weight (dw). Thus, sustained use of seaweed may lead to the buildup of arsenic in soils. The dominant species of arsenic in these seaweeds are in the form of arsenoribofuranosides (arsenosugars). These are assumed to be relatively nontoxic to humans and animals as compared to inorganic species. The arsenosugars are metabolized to different organo-arsenic species but mainly to DMA(V) (dimethylarsinic acid) when consumed as a food source. (Adapted from Castlehouse et ah, 2003)... 

This method for determining arsenic is particularly useful in biological and toxicological studies.8 The material under test is oxidised with a mixture of sulphuric and nitric acids and perhydrol, the arsenic is precipitated as sulphide, which is then oxidised and the arsenic determined colorimetrically after addition of sodium molybdate and stannous chloride. The formation of the molybdenum blue compound is also applied to the micro-determination of arsenic in soil extracts.9... 

Pollution studies is another area where XPS showed promising results. T. Novakov 65) demonstrated the potential of XPS for air pollution studies 157), while other investigations l38) detected arsenic in soil samples. Also the polywater controversy was revealed to be in reality a pollution problem 64). 

Pouschat, P. and Zagury, G.J. (2006) In vitro gastrointestinal bioavailability of arsenic in soils collected near CCA-treated utility poles. Environmental Science and Technology, 40(13), 4317-23. 

The pedosphere contains around 0.6-1.7 x 109 t of arsenic. The residence time of arsenic in soils in climates with moderate temperatures and precipitation is about 1000-3000 years (Matschullat, 2000), 303. Uncontaminated soils derived from the in situ weathering of bedrock usually inherent arsenic from... 

Like sediments, colloids are often important in sorbing and transporting arsenic in soils (Sadiq, 1997 Waychunas, Kim and Banheld, 2005). Colloids may consist of clay minerals, organic matter, calcium carbonate, and various aluminum, manganese, and iron (oxy)(hydr)oxides (Sadiq, 1997). Important iron (oxy)(hydr)oxides include goethite, akaganeite (/J-FeO(OH)), hematite, ferrihydrites, and schwertman-... 

Baroni, F., Boscagli, A., Di Leila, L.A. et al. (2004) Arsenic in soil and vegetation of contaminated areas in southern Tuscany (Italy). Journal of Geochemical Exploration, 81(1-3), 1-14. 

Morrell, J.J., Keefe, D. and Baileys, R.T. (2003) Copper, zinc, and arsenic in soil surrounding douglas-fir poles treated with ammoniacal copper zinc arsenate (ACZA). Journal of Environmental Quality, 32(6), 2095-99. 

Palumbo-Roe, B., Cave, M.R., Klinck, B.A. et al. (2005) Bioaccessibility of arsenic in soils developed over Jurassic ironstones in eastern England. Environmental Geochemistry and Health, 27(2), 121-30. 

Freeman, G.B., Johnson, J.D., Killinger, J.M. et al. (1993) Bioavailability of arsenic in soil impacted by smelter activities following oral administration in rabbits. Fundamental and Applied Toxicology, 21(1), 83-88. 

Peryea, F.J. and Creger, T.L. (1994) Vertical distribution of lead and arsenic in soils contaminated with lead arsenate pesticide residues. Water, Air, and Soil Pollution, 78(3-4), 297-306. 

Corwin, D.L., David, A. and Goldberg, S. (1999) Mobility of arsenic in soil from the Rocky Mountain Arsenal area. Journal of Contaminant Hydrology, 39(1-2), 35-58. 

Rutherford, D.W., Bednar, A.J., Garbarino, J.R. et al. (2003) Environmental fate of roxarsone in poultry litter. Part II. Mobility of arsenic in soils amended with poultry litter. Environmental Science and Technology, 37(8), 1515-20. 

Best demonstrated available technology (BDAT) According to the US Environmental Protection Agency, the best commercial technology for treating a specific hazardous waste. For example, vitrification is the BDAT for treating arsenic in soils (see Chapter 7). 

---