ISO/TC 190/SC 3/WG 10 - Screening methods

This document provides guidance on the selection and application of screening methods for assessing soil quality and waste characterization, including distribution of target parameters in soil and soil‑like material. The aim of this document is to set up criteria as to when the different kind of screening methods can be applied for the analysis of a certain parameter in soil, including soil‑like material, and waste, and which steps are required to prove their suitability. This document does not recommend any particular screening method but confirms the principles of their selection and application.

This document specifies methods for the measurements of magnetic susceptibility of soils (κ) as an indicator of potential soil pollution/contamination with trace elements associated with technogenic magnetic particles (TMPs) and describes related procedures, protocols and guidelines to be applied as a screening geophysical method of determination of soil pollution with trace elements. The results of measurements are used for preparing the maps of magnetic susceptibility of soils in the area of interest. From these maps, the areas of elevated and high magnetic susceptibility indicating high trace element total pollution load are discriminated for further identification of pollutants by geochemical methods. This document is applicable to screening all TMPs-related anthropogenic emission sources including long-range transport of airborne elements, of which TMPs are carriers and indicators. Such emission sources comprise the majority of high-temperature industrial processes, where iron is present in any mineralogical form in raw materials, additives or fuels, is transformed into ferrimagnetic iron oxides (e.g. fossil solid and liquid fuels combustion, metallurgy, cement and ceramics industry, coke production, industrial waste landfills, land transport). This document is not applicable to screening anthropogenic emissions not associated with TMPs, e.g. organic pollutants or emissions from agricultural sources. NOTE 1 Copper, zinc and other non-ferrous metal ores also contain iron (in many sulfides) as this element is abundant in almost all environments. During smelting, the iron occurring in sulfides is transformed into ferrimagnetic oxides (TMPs). However, in such cases, the proportion of TMPs and related PTEs is usually less than at coal combustion or iron metallurgy, for example, and not all PTEs are physically associated and transported by TMPs. Non-airborne elements are deposited in the close proximity of the emission source, while TMPs can be used in these cases as indicators of airborne elements and of the spatial distribution of the total element deposition from a smelter in the area. In rare cases, some soils are developed on bedrock exhibiting geogenically high magnetism, which can cause false-positive results. This influence can, however, be easily indicated by measurements of magnetic susceptibility along soil profiles. This method is not applicable when the bedrock exhibits extremely high magnetic signals. NOTE 2 Such cases are rare.

This document specifies a method for rapid determination of water content in soils. The method is based on refractive index measurement of a sucrose solution after it is mixed with a soil sample. It is applicable to the determination of water content in geological or geotechnical research as well as geotechnical engineering. In addition, it can be used for commercial work in a variety of fields, e.g. agriculture and civil engineering. The working range is up to approximately 50 % moisture content. The precision of the method typically ranges between 0,5 % and 1 % and depends on the type of refractometer that is used. The result of this method is strongly influenced by soil matrices. Higher contents of clay and/or organic matter will lead to significant lower values for water content compared to standard methods such as that described in ISO 11465.

ISO 17183:2016 specifies the procedure to screen highly contaminated soils to detect organic compounds extractable with isopropanol, including a wide range of fuels, oils, and greases. The method is useful for finding hot spots. It is applicable both in laboratories and for site screening in the field. The working range is approximately 0,01 to 0,3 in absorbance units, corresponding to approximately 500 mg/kg to 10 000 mg/kg of isopropanol-extractable organic compounds in soil. The light attenuation due to light scattering/absorption approach in this method is designed to quickly screen soil samples using calibration with the most appropriate substance(s) likely to be present on a given site to indicate the concentration levels. This screening technique is applicable for a broad spectrum of organic compounds, mainly hydrocarbons. Organic compounds are a very broadly defined mixture of compounds, which show their own specific emulsification indices (see Annex A) and a gross emulsification index in a mixture sample, defined primarily by their insolubility in water. The more insoluble the compounds (e.g. non-polar compounds), the higher the response. Hydrocarbons are generally less-reactive and have little polarity. Determination of emulsification indexes uses their non-polar nature to detect organic compounds including a wide range of hydrocarbons from about C8 to about C36. NOTE This method can also be applied to biological substances such as vegetable oils. This method is not applicable for determination of specific organic compounds or groups of compounds that may be part of a larger organic compound mixture. As with other screening techniques, it is advisable to confirm a certain percentage of both positive and negative test results, especially when near or above a regulatory action limit or when the presence of background or when interfering organic compounds such as surface active substances are suspected to be present. This method does not address the evaporation of any volatile organic compound mixtures (i.e., gasoline) during sampling, preparation and detection. Although the screening method can be used for the quantitative detection of volatile hydrocarbons, it is not intended that the method be used for the quantitative determination of volatile petroleum hydrocarbons unless evaporation during sample handling is addressed; the response factor be appropriately corrected, or the method performance be demonstrated on real samples. If emulsifiers or surface active substances (e.g. detergents) are present, significantly negatively-biased or false negative results can be obtained. If there is any evidence for the presence of surfactances in the soil, this method cannot be applied.

ISO 17184:2014 specifies a method for the determination of carbon and nitrogen in soils by direct measurement of sample spectra in the near-infrared spectral region. The spectra are evaluated by a suitable calibration model derived from the results obtained by reference methods.

ISO 18227:2014 specifies the procedure for a quantitative determination of major and trace element concentrations in homogeneous solid waste, soil, and soil-like material by energy dispersive X-ray fluorescence (EDXRF) spectrometry or wavelength dispersive X-ray fluorescence (WDXRF) spectrometry using a calibration with matrix-matched standards. ISO 18227:2014 is applicable for the following elements: Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, Sn, Sb, Te, I, Cs, Ba, Ta, W, Hg, Tl, Pb, Bi, Th, and U. Concentration levels between approximately 0,000 1 % and 100 % can be determined depending on the element and the instrument used.

ISO 13196:2013 specifies the procedure for screening soils and soil-like materials for selected elements when handheld or portable energy-dispersive XRF spectrometers are used. This quick method is assumed to be applied on-site to obtain qualitative or semiquantitative data that assists decisions on further sampling strategy for assessing soil quality. The higher the efforts for pretreatment used on soil samples, the better the analytical results can be expected. ISO 13196:2013 does not explicitly specify elements for which it is applicable, since the applicability depends on the performance of the apparatus and the objective of the screening. The elements which can be determined are limited by the performance of the instruments used, the concentration of the element present in the soil, and the requirements of the investigation (e.g. guideline value). For Hg, Cd, Co, Mo, V and Sb, a majority of instruments are not sensitive enough to reach sufficiently low limits of quantification (LOQ) to meet the requirements (limit or threshold values) set in the ordinances of different countries. In this case, other methods need to be employed to measure these low concentrations. Usually, wet chemical methods are used, based on aqua regia extracts, in combination with optical or mass spectrometric (MS) methods like atomic absorption spectrometry (AAS), inductively coupled plasma/optical emission spectrometry (ICP/OES) or ICP/MS.

This International Standard provides guidance on the selection and application of screening methods for assessing soil quality. Guidance is given to choose an appropriate screening method for a specific parameter and defines the conditions under which they can be used. This International Standard does not recommend any particular screening method, but confirms the principles of their selection and application.