Proposed modification to avoidance test with Eisenia fetida to assess metal toxicity in agricultural soils affected by mining activities

Abstract

Use of avoidance tests is a quick and cost-effective method of assessing contaminants in soils. One option for assessing earthworm avoidance behavior is a two-section test, which consists of earthworms being given the choice to move between a test soil and a control substrate. For ecological relevance, tested soils should be field-contaminated soils. For practical reasons, artificial soils are commonly used as the control substrate. Interpretation of the test results compromised when the test soil and the artificial substrate differ in their physico-chemical properties other than just contaminants. In this study we identified the physico-chemical properties that influence avoidance response and evaluated the usefulness of adjusting these in the control substrate in order to isolate metal-driven avoidance of field soils by earthworms. A standardized two-section avoidance test with Eisenia fetida was performed on 52 uncontaminated and contaminated (Cu >155mgkg, As >19mgkg) agricultural soils from the Aconcagua River basin and the Puchuncaví Valley in Chile. Regression analysis indicated that the avoidance response was determined by soil organic matter (OM), electrical conductivity (EC) and total soil Cu. Organic matter content of the artificial substrate was altered by peat additions and EC by NaCl so that these properties matched those of the field soils. The resultant EC for avoidance (indicative of soils of "limited habitat") was 433mg Cu kg (339 - 528mgkg 95% confidence intervals). The earthworm avoidance test can be used to assess metal toxicity in field-contaminated soils by adjusting physico-chemical properties (OM and EC) of the artificial control substrate in order to mimic those of the field-collected soil.

Role of Leaf Litter on the Incorporation of Copper-Containing Pesticides into Soils Under Fruit Production: a Review

“…Surprisingly, we found that there is little data available on Cu toxicity thresholds-like effective concentration (ECx), lowest observed effect concentration (LOEC), and no observed effect concentration (NOEC)-for fieldcontaminated soils. Six studies were found for plants (Hamels et al 2014;Kolbas et al 2014;Kolbas et al 2018;Lillo-Robles et al 2020;Mondaca et al 2017;Verdejo et al 2015), five for earthworms (Delgadillo et al 2017;Konečný et al 2014;Mirmonsef et al 2017;Scott-Fordsmand et al 2000;Van Zwieten et al 2004), and only three for soil microorganisms (Arthur et al 2012;Oorts et al 2006;Sauvé 2006). A specific EC x value for a given species, endpoint, and bioassay exposition time may have limited relevance from an agricultural or ecological point of view (Delgadillo et al 2017;Mondaca et al 2017).…”

“…Geometric means are preferable to arithmetic ones, since the data is often log-normally distributed (Checkai et al 2014). Therefore, geometric means were calculated for each study presented in Table 1 (with the exception of Delgadillo et al (2017), Konečný et al (2014), and Oorts et al (2006) who present a unique value for their respective ECx) to have a better idea of Cu toxicity thresholds in plants, earthworms, and soil microorganisms.…”

Use of Zinc Carbonate Spiking to Obtain Phytotoxicity Thresholds Comparable to Those in Field‐Collected Soils

“…In field-collected soils, contamination may have happened decades ago and the "aging" process has already occurred (Smolders et al 2009;McBride and Cai 2016). Considering these facts, in our previous studies, we argued that environmental assessment and soil quality decision-making should not be based on toxicity experiments performed on metal-spiked soils but should consider studies performed on field-collected soils (Verdejo et al 2015;Delgadillo et al 2017;Mondaca et al 2017;Neaman et al 2017;Stowhas et al 2018).…”

Evaluating Earthworms’ Potential for Remediating Soils Contaminated with Olive Mill Waste Sediments

“…This is a threshold value that defines the soil habitat limit, as suggested by Hund-Rinke et al [39]. Many studies have used the ABR test to evaluate the potential toxicity of soils contaminated by metals [40], pesticides [41,42], cyanotoxins [43], veterinary pharmaceuticals [44], microplastics [45] or soil additives such as biochar [46,47]. Although the ABR test guidelines recommend the use of the epigeic earthworms Eisenia fetida or E. andrei [19], soil-dwelling earthworm species such as L. terrestris are now adopted in standardized methods such as the ABR test [48].…”