Soil extracts aqua regia

Rowbottom, W. H. (1991). Determination of ammonium acetate extractable molybdenum in soil, and aqua regia (hydrochloric acid and nitric acid,... 

Two commercial partial extraction techniques improve anomaly contrast in B horizon soil samples compared to aqua regia-ICPMS for Cu and Au. However, whereas the MMIsm and Bio LeachSM Cu profiles are similar, the MMIsm Au signal is much larger than that for Bio LeachSM. Analysis of samples at different depths down the B soil horizon profile indicates that the geochemical response from these methods is depth dependant. 

Soil samples were analyzed for 53, aqua regia extractable elements by ICP-MS/ES. Cadmium, uranium and molybdenum are anomalous over part of the Lisbon field and most of the Lightning Draw Southeast field (Fig. 4). Mercury, lead and organic carbon are also anomalous over both fields. 

Soil samples were analyzed for 53 aqua regia extractable elements by Inductively Coupled Plasma Mass Spectrometry and... 

The subsamples were split and sent to different laboratories to be subjected to ten commonly-used and proprietary leach/digestion techniques (a) aqua regia partial digestion method at Acme Analytical Laboratories (b) sodium pyrophosphate and cold hydroxylamine leaches at ALS Chemex (c) enzyme and TerraSol leach methods at Skyline Labs (d) Bioleach and soil gas hydrocarbon analyses at Activation Laboratories (e) Mobile metal ion (MMI) extraction at SGS Minerals (f) 4-acid near-total and sodium peroxide sinter total digestions (under the uses contract) at SGS Minerals and (g) de-ionized water leach at the USGS laboratories. 

Berrow, M.L. and Stein, W.M. (1983) Extraction of metals from soils and sewage sludges by refluxing with aqua regia. Analyst, 108, 277-285. 

For soil samples ultrasonication in 1 1 diluted aqua regia was found to give excellent recovery of As, Cd, Pb, and Ag from reference samples. The results were comparable to those obtained by microwave digestion, and the speed of extraction and sample throughput were better with the ultrasonication. The samples were ultrasonicated for three periods of 3 minutes each and shaken by hand between untrasound treatments. A batch of 50 samples could be sonicated simultaneously [23],... 

Aqua regia extraction is a strong partial extraction method that dissolves carbonates, most sulphide minerals, some silicates like olivine and trioctahedral micas, clay minerals and primary and secondary salts and hydroxides (Salminen, 1995). It can be considered a quasi-total extraction method, since actual total concentrations can be higher. On the other hand, this leaching method overestimates the bioavailable amount of toxic elements in a soil since metals trapped in the silicate lattice are released very slowly in the environment and are not easily involved in plant nutrition processes. 

Extraction methods based on solutions of chelating agents, such as EDTA and DTPA, or salts of weak acids, such as ammonium acetate (CH3COONH4) (Lakanen and Ervio, 1971 Lindsay and Norwell, 1969), can be used to assess plant-available trace element contents of soils and to evaluate more robustly human exposure to environmental risks in an urban context. A study carried out in the main cities of Campania region in southern Italy (Albanese, 2008) demonstrated how the bioavailable concentrations of some trace elements such as Zn, Pb and Cu in soils, determined using ammonium acetate-EDTA extraction, are much lower than the elemental concentrations determined by an aqua regia extraction on the same samples (Table 8.1). 

For quality control, the residue from step 3 has to be digested in aqua regia ( step 4 ) and the cumulative amount of metal extracted [i.e. 2(step 1 + step 2 + step 3 + step 4 )] is compared with the pseudototal amount of metal obtained by aqua regia digestion of a separate 1-g soil sample. In the modified BCR procedure, a 0.5 M hydroxylamine hydrochloride solution at pH 1.5 is applied in step 2. 

But there is no specific FAAS standard method specially evaluated or approved for polluted soil samples there is the EPA methods (SW-846 EPA (2000)) or one ISO standard (ISO 11047). This standard is connected with the determination of several metals in aqua regia extracts. It provides a method for the determination of Cd, Cu, Co, Pb, Mn, Ni and Zn by flame and electrothermal atomic absorption spectrometric methods. 

ISO (1995) Soil Quality - Extraction of trace elements soluble in aqua regia. International standard... 

ISO (2001) Soil Quality - Determination of mercury in aqua regia soil extracts with cold-vapour atomic spectrometry or cold vapour atomic fluorescence spectrometry, ISO/DIS 16772. 

ISO (2001) Soil Quality — Determination of arsenic, antimony and selenium in aqua regia soil extracts with electrothermal or hydride generation atomic absorption spectrometry, draft ISO/CD 20280. ISO/DIS 17294, Water Quality — Application of inductively coupled plasma mass spectrometry (ICP-MS) - Part 1 General guideline Part 2 Determination of 61 elements (in preparation). 

ISO/CD 20280 Soil quality - Determination of arsenic, antimony and selenium -Method by extraction in aqua regia and atomic absorption spectrometry. 

Total soil element concentrations determined in aqua regia. b Extraction with 0.43 N HNO3. 

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