Soil solution extractants

Table 3.3. Concentrations of trace elements in soil solutions extracted by saturated paste from two metal salt-spiked Israeli soils incubated at the saturated paste regime...

Eaton F.M., Elarding R.B., Ganje T.J. Soil solution extractions at tenth-bar moisture percentages. Soil Sc 1960 90 253-258. 

The major ion composition of dispersed soil solutions and saturation extracts from selected soils in California, U.S. Concentrations of trace elements in soil solutions of the California soils that received sludge applications. Concentrations of trace elements in soil solutions extracted by saturated paste from two metal salt-spiked Israeli soils incubated at saturated regime. 

Koopmans GF, Groenenberg JE. Effects of soil oven-drying on concentrations and speciation of trace metals and dissolved organic matter in soil solution extracts of sandy soils. Geoderma 2011 161 147-158. 

It is difficult to obtain reliable measurements of En and hence pe in soils. Strictly, only measurements made with the electrodes in soil solution extracts rather than directly in soil are thermodynamically meaningful, and these are also subject to various errors, particularly due to the presence of mixed redox systems. Nonetheless it is a useful parameter and is the only single electrochemical property that can distinguish submerged soils from well-drained ones. 

Hance, R.J. and S.J. Embling (1979). Effect of soil water content at the time of application on herbicide content in the soil solution extracted in a pressure membrane apparatus. Weed Res., 19 201-205. 

Eaton, F.M., Harding, R.B. and Ganje, T.J. (1960) Soil solution extracts at tenth-bar moisture percentage. Soil Sci., 90, 253-258. 

Dahlgren, R. A. (1993). Comparison of soil solution extraction procedures Effect on solute chemistry. 

Tiensing, T., Preston, S., Strachan, N., and Paton, G. I. (2001). Soil solution extraction techniques for microbial ecotoxicity testing A comparative evaluation. J. Environ. Monit. 3(1), 91—96. 

Shand, C.A., Macklon, A.E.S., Edwards, A.C. and Smith, S. (1 994) Inorganic and organic P in soil solutions from three upland soils. I. Effects of soil solution extraction conditions, soil type and season. Plant and Soil 1 59, 255-254. 

This method can also be used to analyse soil samples. For instance, fenpropi-morph, which is a non-polar pesticide with good UV sensitivity but poor selectivity, has, after treatment, been determined in soil samples (31). In this example, an amount of soil was extracted overnight with acetonitrile this was then poured into a Buchner filter and rinsed with the same solvent. The acetonitrile solution was concentrated and, prior to LC analysis, the extract was diluted with water and 100 p.1 were then injected into the LC system. 

R. Kuchenbuch and A. Jungk, A method for determining concentration profiles at the soil root interface by thin slicing rhizosphere. soil. Plant Soil 68 39 (1982). D. Zabowski, Limited release of soluble organics from roots during the centrifugal extraction of soil solutions. Soil Sci. Soc. Am. J. 53 911 (1989). 

For wheat grain, extract the concentrate three times with 10 mL of chloroform-methanol (3 1, v/v). For the soil sample, extract the aqueous layer after washing with n-hexane twice with 60 mL of chloroform-methanol (3 1, v/v). Dry the chloroform-methanol layer with anhydrous sodium sulfate [for wheat grain, use a small amount (about 8 g) of anhydrous sodium sulfate] and collect the dried solution in a 200-mL round-bottom flask. Evaporate the solvent under reduced pressure and proceed to ion-exchange column chromatography. 

Transfer the concentrate from Section 6.1 to a 200-mL separatory funnel with 50 mL of water and add 10 mL of saturated aqueous sodium chloride solution. Extract twice with 100 mL of n-hexane. Dry the n-hexane extract by passing through about 80 g of anhydrous sodium sulfate on a glass funnel into a 500-mL separatory funnel for the rice samples and into a 500-mL round-bottom flask for the soil sample. Wash the anhydrous sodium sulfate with 30 mL of n-hexane and combine the washings into the vessel. The n-hexane extract of soil sample is evaporated to dryness under reduced pressure, then the soil residue is processed as described in Section 6.3.2. 

Soil is extracted twice with methanol-1 N hydrochloric acid (3 1, v/v), centrifuging between each extraction. An aliquot of the combined soil extract is diluted with acidified (pH 1)5% (w/v) sodium chloride solution and subjected to liquid-liquid partitioning with dichloromethane. The dichloromethane extract is evaporated and the residue is dissolved in mobile phase prior to quantitation by LC/MS/MS. 

The adsorption solutions from the highest concentrations runs were extracted with ether. The ether extracts were concentrated and analyzed by TLC. Similarly, the corresponding soils were extracted with ether and the ether extracts were analyzed by TLC. Other soil samples were analyzed by combustion in order to determine directly the amount of adsorbed herbicide. 

Table 3.1. The major ion composition of dispersed soil solutions and saturation extracts from selected soils in California, U.S. 

Figure 3.3. Changes of Cd speciation in soil solutions of Cd nitrate-treated Domino soil from California (data extracted from Candelaria and Chang, 1997)...

Figure 3.5. Effects of Cl concentrations (NaCl or CaCl2) on Cd solution speciation in a California soil (data extracted from Bingham et al., 1983)...

Residual. This fraction mainly contains primary and secondary minerals, which hold elements within their crystal structure. This fraction also contains trace elements remained from the extraction of all previous fractions (e.g., humin bound). These metals/trace elements are not expected to be released into soil solutions over a reasonable time span under conditions normally encountered in nature. 

Extraction of the CARB fraction by the NaOAc-HOAc solution at various pHs resulted in the larger differences obtained in the subsequent fractions, i.e., ERO fraction, OM fraction, and to some extent, the RO fraction (Figs. 4.4 and 4.5). Extraction of the CARB fraction by NaOAc-HOAc solutions at pH 6.0 and 7.0 usually led to higher contents of major and trace elements in the ERO fraction than that by the buffer solutions at pH 4.0 and 5.0. This was especially obvious for Ca and Mg in calcareous soils. Metal extraction from the OM and RO fractions after extraction of the CARB fraction by the NaOAc-HOAc solutions at pH 7.0 and 6.0 were also higher than those extracted by the buffer solutions at pH 4.0 and 5.0, as shown in Figs. 4.4 and 4.5. 

---