Comparison of methods for determining the total contents of main and trace elements in soils

Description

Comparison between total grades and royal water extractable grades carried out as part of the study project “Heavy metals in mineral soil samples from the BZE project”. Financially, the comparison of methods was funded by the Ministry of Environment and Nature Conservation, Agriculture and Consumer Protection (MUNLV) of the State of North Rhine-Westphalia. In soil science practice, the question of the comparability of data is increasingly raised. This is especially true where data is collected and evaluated from different sources. The transformation of different data to a reference level could help condense information, improve statistical collateral, and reduce analytical costs by using multiple data sources. In the investigation of trace and main elements in looser and solid rocks, different total and partial digestion methods are used depending on the objective of the study. The latter, as the name suggests, only capture proportions of the total concentration of an element. Overall, these grades are often referred to as total content, total concentration or total fraction, which applies in particular to the range of partial digestion methods. The comparability of the methods is best characterised by correlation calculation using B-value (determination measure R2 from 0 – 100 %). For each relationship, the B-value determined by calibration and the scope of validity (minimum and maximum of the element content obtained per method and sample collective) should be indicated. A good method should achieve at least 90 % B-values, with the regression equation referring to a wide matrix of differently compounded and polluted soil samples. Relationships with less meaningfulness are, at least in part, still useful for indicative values. In the field of geosciences, the determination of true total contents is the usual procedure, as only on this basis can correct accounting be carried out. For this purpose, X-ray fluorescence spectroscopy with melt digestion or pressing or wet chemical (pressure) digestion with hydrofluoric acid or mixture and AAS and ICP spectroscopy is used. In the area of the environment, due to existing regulatory frameworks, it is necessary to use for the determination of total element levels in the soils of the Royal Water (KW) extract (DIN 38414 Part 7); although the method only indicates the total content for a few elements and does not directly reflect the plant-available and relocable element content. For example, the Federal Republic of Germany enacted the Waste Sewage Sludge Ordinance (AbfKlärV 1982, 1992) to protect soils from excessive exposure to heavy metals by spreading sewage sludge. It regulates the application quantity of dry sludge per surface area and prescribes legally established maximum limits (limit values) for heavy metals in soils and in the sludge dry matter. Also in the draft of the sub-legislation of the Federal Soil Protection Act (BBodSchG, 1998), the precautionary values specified therein are based on royal water extractable element contents. In addition, the royal water extract is used in the field of forest soil analysis. According to the Federal Instructions on Soil State Survey in Forests (BZE, 1994), humus samples are preferably examined using this method. In the case of permanent observation areas under forest, however, the determination of the material stock in mineral soils is again based on real total digestion processes. In soil science practice, therefore, a comparability of the data is urgently required. Statements to this end require (I) evaluations on a wide range of differently compounded and polluted soil samples, (II) the use of standardised digestion and measurement methods, and (III) the application and documentation of recognised statistical methods. The research carried out on behalf of the Ministry of Environment, Spatial Planning and Agriculture in North Rhine-Westphalia aims to provide technical methods for the use of values that have not been obtained according to the method of the Federal-Soil Protection Act. The aim of the work was to make statements on the comparability of two commonly used wet chemical processes, hydrofluoric acid digestion and royal water extract, under the most cost-effective conditions and use of existing data. The results of the comparison of methods were submitted to the MUNLV in an 113-page report on 31 August 2002. A PDF file available for download (5 256 KB) reflects the examination report in abbreviated form and is limited to the representation of the elements lead (Pb), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), thalium (Tl) and zinc (Zn). The complete investigation report can be obtained by request to the Geological Service NRW – Landesbetrieb.

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  • regression
  • land-use
  • totalaufschluss
  • königswasser
  • abfall-klärschlamm-verordnung
  • literatur
  • gesamtgehalt
  • bodenbewertung
  • veröffentlichung
  • bodeninventur
  • buch
  • umweltliteratur
  • thalium
  • teilaufschluss
  • bericht
  • publikation
  • bundesarbeitsanleitung-zur-bodenzustandserhebung-im-wald
  • hauptelement
  • röntgenfloureszenz

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  • TECH

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