extracellular enzymes linked to C-, P-, and S-cycling, which were bound onto
biochar surface [187]. The earthworm mucus produced by the skin mucous cells
and the gastrointestinal epithelium was postulated as the main mechanism of enzymatic activation of biochar [73]. The functional system created by the co-application
of earthworms and biochar was proposed as a strategy for removing organic pollutants from contaminated soils and feedstocks [164]. We propose an identical model
for the in situ degradation or immobilisation of APIs in agricultural soils (Fig. 4).
Whether or not this bioremediation strategy is viable will depend mainly on the
following variables, which require further investigation:
1. Earthworm species and exotic species. Figure 2 illustrates the feeding strategies
of epigeic, anecic and endogeic earthworms. Both anecic and endogeic species
are soil engineering organisms because of their intensive burrowing activity
[39]. Moreover, some laboratory experiments have shown that anecic and
endogeic species can co-exist in a limited volume of soil. For example, the
burrowing activity of L. terrestris was not affected by the presence of
A. caliginosa, although the depth of the burrow system created by the anecic
species was shorter than the burrow structure created when the species was
incubated alone [188]. Moreover, the burrowing activity of A. caliginosa was
favoured by the presence of the anecic earthworm Aporrectodea giardi; the
organic matter-rich walls of the burrows created by A. giardi served as a food
source to A. caliginosa [188]. These examples suggest that co-application of
earthworms of different ecological strategies to soils contaminated with APIs
could be the best option for obtaining the maximal benefit from earthworm
activity on API dissipation. Environmental fate of APIs should be, therefore,
investigated in soils holding a wide representation of the most common earthworms found in agricultural soils [92–94], ideally covering the three ecological
groups of earthworms (Fig. 2). In our model of in situ vermiremediation, particular concern should be put on the introduction of earthworm exotic species (the
term refers to not naturally occurring species, so-called alien species, in the
location in which it is found [189]). Indeed, one of the objectives of the United
Nations Sustainable Development Goal no. 15 (Life on land, www.undp.org) is
“to prevent the introduction and significantly reduce the impact of invasive alien
species on land and water ecosystems...”. Therefore, care must be taken when we
chose in situ vermiremediation. Endogenous and exogenous features of earthworms such as feeding behaviour (epigeic, endogeic and anecic), tolerance to
environmental changes (phenotypic plasticity), reproductive characteristics, morphological characteristics and locomotion as well as environmental variables
(edaphic and climatic conditions, presence of predators, and substantial and
continue surface litter layers, among others) are important invasiveness traits to
be considered before adding earthworms to agricultural soils [70].
2. Earthworm tolerance to biochar. Many studies have investigated the potential
toxicity of biochar upon earthworms. Doses of biochar 2.0% (w/w) generally
are tolerated by different earthworm species as indicated by the absence of
significant avoidance response to biochar-amended soils [190]. However, signs
Vermiremediation of Pharmaceutical-Contaminated Soils and Organic Amendments
361
biochar surface [187]. The earthworm mucus produced by the skin mucous cells
and the gastrointestinal epithelium was postulated as the main mechanism of enzymatic activation of biochar [73]. The functional system created by the co-application
of earthworms and biochar was proposed as a strategy for removing organic pollutants from contaminated soils and feedstocks [164]. We propose an identical model
for the in situ degradation or immobilisation of APIs in agricultural soils (Fig. 4).
Whether or not this bioremediation strategy is viable will depend mainly on the
following variables, which require further investigation:
1. Earthworm species and exotic species. Figure 2 illustrates the feeding strategies
of epigeic, anecic and endogeic earthworms. Both anecic and endogeic species
are soil engineering organisms because of their intensive burrowing activity
[39]. Moreover, some laboratory experiments have shown that anecic and
endogeic species can co-exist in a limited volume of soil. For example, the
burrowing activity of L. terrestris was not affected by the presence of
A. caliginosa, although the depth of the burrow system created by the anecic
species was shorter than the burrow structure created when the species was
incubated alone [188]. Moreover, the burrowing activity of A. caliginosa was
favoured by the presence of the anecic earthworm Aporrectodea giardi; the
organic matter-rich walls of the burrows created by A. giardi served as a food
source to A. caliginosa [188]. These examples suggest that co-application of
earthworms of different ecological strategies to soils contaminated with APIs
could be the best option for obtaining the maximal benefit from earthworm
activity on API dissipation. Environmental fate of APIs should be, therefore,
investigated in soils holding a wide representation of the most common earthworms found in agricultural soils [92–94], ideally covering the three ecological
groups of earthworms (Fig. 2). In our model of in situ vermiremediation, particular concern should be put on the introduction of earthworm exotic species (the
term refers to not naturally occurring species, so-called alien species, in the
location in which it is found [189]). Indeed, one of the objectives of the United
Nations Sustainable Development Goal no. 15 (Life on land, www.undp.org) is
“to prevent the introduction and significantly reduce the impact of invasive alien
species on land and water ecosystems...”. Therefore, care must be taken when we
chose in situ vermiremediation. Endogenous and exogenous features of earthworms such as feeding behaviour (epigeic, endogeic and anecic), tolerance to
environmental changes (phenotypic plasticity), reproductive characteristics, morphological characteristics and locomotion as well as environmental variables
(edaphic and climatic conditions, presence of predators, and substantial and
continue surface litter layers, among others) are important invasiveness traits to
be considered before adding earthworms to agricultural soils [70].
2. Earthworm tolerance to biochar. Many studies have investigated the potential
toxicity of biochar upon earthworms. Doses of biochar 2.0% (w/w) generally
are tolerated by different earthworm species as indicated by the absence of
significant avoidance response to biochar-amended soils [190]. However, signs
Vermiremediation of Pharmaceutical-Contaminated Soils and Organic Amendments
361