Phytoassays may be applied for ecotoxicity evaluation of treated soils amended
with organic matter if the soil additions do not exhibit toxic response to plants.
Germination tests may employ different plant species. For TPH-contaminated soil,
the recommended specie is the cress specie Lepidium sativum (Maila and Cloete
2005; Mao et al. 2009; Gargouri et al. 2014). This specie was also successfully
applied for quality evaluation of composted digestate (Bustamante et al. 2013).
Phytoassays with the use of Lepidium sativum on artificial soil amended with
digestate in ratio below 1:20 showed no signs of toxicity but a positive effect on
plant growth (Pivato et al. 2016).
The studies on composted digestate have demonstrated lower level of phytotoxicity in comparison with non-treated digestate (Abdullahi et al. 2008; Bustamante
et al. 2013). In the study of Abdullahi et al. (2008) composted digestate improved the
germination rate in comparison with non-amended soil. The study of Tambone et al.
(2015) revealed no signs of phytotoxicity of plants cultivated on water extracts from
composted digestates. The final quality of compost obtained from digestate may
differ depending on the properties of the feedstock as well as operating parameters of
digestion process and the management of final product (Holm-Nielsen et al. 2009).
5.4.3.3 Invertebrate Assays
Common bioassays based on invertebrates often use earthworm or less frequently
springtails. Earthworm bioassays are based on mortality, biomass loss, and behavior
of invertebrates after contact with contaminated soil or diluted pollutant (Schaefer
2003; Mao et al. 2009; Hentati et al. 2013). An example of earthworm bioassays is
the avoidance test which results are expressed as EC 50 (Loureiro et al. 2005).
Because of proximity with soil particles, invertebrates are considered as good
indicators for contaminated sites (Jager et al. 2005). Standards recommended by
International Organization for Standardization (ISO) for determining the effect of
chemicals on behavior such as avoidance of invertebrates suggest species of earthworms like Eisenia fetida and Eisenia andrei or springtails as Folsomia candida
(Hentati et al. 2013). E. fetida is also recommended for acute toxicity tests by OECD
guidelines (OECD 207 1984). Existing OECD guidelines are more suitable for
testing general toxicity of chemicals as the use of standard soil is recommended
and may be applied in experiments with spiked soil. In case of the evaluation of real
contaminated soil the standard of ISO are more suitable as avoidance tests on real
soil are considered in comparison with standard soil.
Some species of Eisenia are often used in studies concerning TPH-contaminated
soil (Salanitro et al. 1997; Hubálek et al. 2007; Mao et al. 2009; Frutos et al. 2012;
Hentati et al. 2013). Earthworms are exposed to contaminant through dermal uptake
due to thin and permeable cuticle and alimentary uptake due to large amounts of soil
consumed (Jager et al. 2005). The study on E. fetida showed the ability to transform
digestate improved with bulking agent into quality vermin compost (Krishnasamy
et al. 2014). The tests on artificial soil mixed with digestate also showed no toxicity
toward E. fetida up to 15% of added amendment (Pivato et al. 2016). However,
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with organic matter if the soil additions do not exhibit toxic response to plants.
Germination tests may employ different plant species. For TPH-contaminated soil,
the recommended specie is the cress specie Lepidium sativum (Maila and Cloete
2005; Mao et al. 2009; Gargouri et al. 2014). This specie was also successfully
applied for quality evaluation of composted digestate (Bustamante et al. 2013).
Phytoassays with the use of Lepidium sativum on artificial soil amended with
digestate in ratio below 1:20 showed no signs of toxicity but a positive effect on
plant growth (Pivato et al. 2016).
The studies on composted digestate have demonstrated lower level of phytotoxicity in comparison with non-treated digestate (Abdullahi et al. 2008; Bustamante
et al. 2013). In the study of Abdullahi et al. (2008) composted digestate improved the
germination rate in comparison with non-amended soil. The study of Tambone et al.
(2015) revealed no signs of phytotoxicity of plants cultivated on water extracts from
composted digestates. The final quality of compost obtained from digestate may
differ depending on the properties of the feedstock as well as operating parameters of
digestion process and the management of final product (Holm-Nielsen et al. 2009).
5.4.3.3 Invertebrate Assays
Common bioassays based on invertebrates often use earthworm or less frequently
springtails. Earthworm bioassays are based on mortality, biomass loss, and behavior
of invertebrates after contact with contaminated soil or diluted pollutant (Schaefer
2003; Mao et al. 2009; Hentati et al. 2013). An example of earthworm bioassays is
the avoidance test which results are expressed as EC 50 (Loureiro et al. 2005).
Because of proximity with soil particles, invertebrates are considered as good
indicators for contaminated sites (Jager et al. 2005). Standards recommended by
International Organization for Standardization (ISO) for determining the effect of
chemicals on behavior such as avoidance of invertebrates suggest species of earthworms like Eisenia fetida and Eisenia andrei or springtails as Folsomia candida
(Hentati et al. 2013). E. fetida is also recommended for acute toxicity tests by OECD
guidelines (OECD 207 1984). Existing OECD guidelines are more suitable for
testing general toxicity of chemicals as the use of standard soil is recommended
and may be applied in experiments with spiked soil. In case of the evaluation of real
contaminated soil the standard of ISO are more suitable as avoidance tests on real
soil are considered in comparison with standard soil.
Some species of Eisenia are often used in studies concerning TPH-contaminated
soil (Salanitro et al. 1997; Hubálek et al. 2007; Mao et al. 2009; Frutos et al. 2012;
Hentati et al. 2013). Earthworms are exposed to contaminant through dermal uptake
due to thin and permeable cuticle and alimentary uptake due to large amounts of soil
consumed (Jager et al. 2005). The study on E. fetida showed the ability to transform
digestate improved with bulking agent into quality vermin compost (Krishnasamy
et al. 2014). The tests on artificial soil mixed with digestate also showed no toxicity
toward E. fetida up to 15% of added amendment (Pivato et al. 2016). However,
272
A. Gielnik et al.