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Title:
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Evaluation of the Single Dilute (0.43 M) Nitric Acid Extraction to Determine Geochemically Reactive Elements in Soil
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Author(s):
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Groenenberg, J.E.; Romkens, P.F.A.M.; Zomeren, A. van; Rodrigues, S.M.; Comans, R.N.J.
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Published by:
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Publication date:
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ECN
Environment & Energy Engineering
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24-8-2017
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ECN report number:
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Document type:
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ECN-W--17-019
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Article (scientific)
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Number of pages:
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8
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Published in: Environmental Science & Technology (American Chemical Society), , 2017, Vol.51, p.2246-2253.
Abstract:
Recently a dilute nitric acid extraction (0.43 M) was adopted by ISO (ISO17586:2016)as standard for extraction of geochemically reactive elements in soil and soil like materials. Here we evaluate the performance of this extraction for a wide range of elements by mechanistic geochemical modeling. Model predictions indicate that the extraction recovers the reactive concentration quantitatively (>90%). However, at low ratios of element to reactive surfaces the extraction underestimates reactive Cu, Cr, As, and Mo, that is, elements with a particularly high a?nity for organic matter or oxides. The 0.43 M HNO3 together with more dilute and concentrated acid extractions were evaluated by comparing model-predicted and measured dissolved concentrations in CaCl2 soil extracts, using the di?erent extractions as alternative model-input. Mean errors of the predictions based on 0.43 M HNO3 are generally within a factor three, while Mo is underestimated and Co, Ni and Zn in soils with pH > 6 are overestimated, for which possible causes are discussed. Model predictions using 0.43 M HNO3 are superior to those using 0.1 M HNO3 or Aqua Regia that under- and overestimate the reactive element contents, respectively. Low concentrations of oxyanions in our data set and structural underestimation of their reactive concentrations warrant further investigation.
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