Overview of Selected Soil Pore Water Extraction Methods for the Determination of Potentially Toxic Elements in Contaminated Soils: Operational and Technical Aspects

Abstract

Chemical elements that are either present naturally in the soil or introduced by pollution are more usefully estimated in terms of 'availability' of the element, since it is this property that can be related to mobility and uptake by plants. A good estimation of 'availability' can be achieved by measuring the concentration of the element in soil pore water. Recent achievements in analytical techniques allowed to expand the range of interest to trace elements, which play a crucial role both in contaminated and uncontaminated soils and include those defined as potentially toxic elements (PTE) in environmental studies. A complete chemical analysis of soil pore water represents a powerful diagnostic tool for the interpretation of many soil chemical phenomena relating to soil fertility, mineralogy, and environmental fate. This chapter describes some of the current methodologies used to extract soil pore water. In particular, four laboratory-based methods, i) high speed centrifugation-filtration, (ii) low (negative-) pressure Rhizon™ samplers, (iii) high pressure soil squeezing and (iv) equilibration of dilute soil suspensions, are described and discussed in detail. A number of operational factors are presented: pressure applicable (i.e., pore size involved), moisture pre-requisites of the soil, pore water yielding, efficiency, duration of extraction, materials and possible contaminations for PTE studies. Some consideration is then taken to assess advantages and disadvantages of the methods, including costs and materials availability.

Field sampling of soil pore water to evaluate the mobile fraction of trace elements in the Iglesiente area (SW Sardinia, Italy)

“…From many studies (Impelliteri et al, 2003;Tye et al, 2003;Cui et al, 2014), it is well established that total soil/waste metal content alone is not an adequate measure of the potential mobility of a (toxic) element and, consequently, of its possible uptake by plants (Vig et al, 2003;Di Bonito et al, 2008;Barbafieri et al, 2011). Therefore, chemical methods to determine trace metal phytoavailability in soils are usually based on the measurement of the extractable or labile fractions of those elements (De Siervi et al, 2004).…”

“…The Netherlands) (Tye et al, 2003;Di Bonito et al, 2008). Using this device, pore water solution is extracted by inserting it into the soil, and connecting a syringe for applying the vacuum and then a suction.…”

Intercomparison of soil pore water extraction methods for stable isotope analysis and interpretation of hillslope runoff sources

“…The centrifugation set‐up and tubes were prepared following di Bonito, Breward, Crout, Smith, and Young () and Orlowski et al (). Two 15‐ml tubes were prepared as “filter tubes” for each sample, with Whatman® Grade 1 filter paper placed over the exit hole of the first tube containing the soil sample.…”

Validation of Cryogenic Vacuum Extraction of Pore Water from Volcanic Soils for Isotopic Analysis

“…In this regard [13] used CVE in well-developed Andosols, but to our knowledge, this work is the first to explore two contrasting soil types: Arenosols and Andosols, at five soil water retention energies. Even though the literature reports success on extracting water from sandy soils using centrifugation [14,16] or suction cups [20], it is worth noting that it was not possible to extract water from our samples using the cited methods due to their volcanic nature of soils, either at wet or dry moisture levels.…”

“…There is a plethora of methods to extract water from soil pores, from mechanical procedures, such as centrifugation, to methods that involve water phase change and subsequent recovery of water vapor, such as vapor equilibrium and cryogenic vacuum extraction. Di Bonito et al [14], Millar et al [15] and Orlowski et al [16] give detailed assessments and comparison of methods. Among these listed techniques, cryogenic vacuum extraction (CVE) is widely used due to its easy setup and operation [17][18][19].…”