It is now widely recognised that API accumulation in agricultural soils may be
a serious threat to non-target organisms and natural resources. For example,
ketoprofen, carbamazepine and caffeine were detected in groundwater samples
from Europe at concentrations of 2.88, 3.60 and 4.50 μg/L, respectively [16],
suggesting a high mobility of these chemicals in soil. Likewise, many studies have
demonstrated that edible plants growing in API-contaminated soils accumulate and
translocate APIs to aerial parts [11]. Furthermore, APIs may cause biochemical and
physiological adverse effects in plants, negatively affecting their growth and development [7]. As a result, non-target organisms including human beings may be
exposed to API through the consumption of contaminated edible plants. For example, bee exposure to pharmaceuticals accumulated in pollen and nectar from zucchini
flowers was modelled for carbamazepine, and outcomes revealed that honeybee
colonies as well as the bee behaviour could be seriously affected by moderate
hydrophobic APIs [21]. Nevertheless, field surveys are still needed to draw solid
conclusions about exposure levels of wildlife to API-contaminated plants.
Soil functioning is also altered by APIs. Although biodegradation is the major
dissipation route [22, 23], these chemicals are able to alter soil microbial activity and
community [19] and soil enzyme activities [24–26]. Because soil enzyme activities
catalyse most chemical reactions involved in the transformation and decomposition
of organic matter, and nutrient cycling [27], their alteration by APIs could lead to soil
degradation. Therefore, affordable mitigating measures and remediation strategies
should be taken into account to reduce the potential environmental risks of APIs. In
this context, the use of earthworms emerges as a promising strategy for reducing API
concentration and toxicity at the source (treatment of biosolids and manure) and in
agricultural soils receiving continual input of APIs.
This chapter describes the mechanisms and technical aspects linked to earthworms’ capacity to remediate API-contaminated soils and amendments. The first
section makes a brief overview of the earthworm effects on soil functioning,
therefore providing insights into the importance of these organisms in API degradation (Sect. 2). The third section provides data on toxic effects of APIs in earthworms: a knowledge needed to propose these organisms as biological vectors of API
biodegradation. The fourth and fifth sections consider two options for using earthworms in managing API residues: vermicomposting of organic residues such as
biosolids and manure (ex situ vermiremediation) and inoculation of soils with
earthworms (in situ vermiremediation). The sixth section discuss how to improve
API vermiremediation by using biochar. The last section will identify knowledge
gaps that require further research to boost the use of earthworms for enhancing the
natural attenuation of agricultural soil against APIs and other organic pollutants.
2 Impact of Earthworms on Soil Quality
The term soil quality defines the “capacity of a specific kind of soil to function,
within natural or managed ecosystem boundaries, to sustain plant and animal
productivity, maintain or enhance water and air quality, and support human health
342
J. C. Sanchez-Hernandez
a serious threat to non-target organisms and natural resources. For example,
ketoprofen, carbamazepine and caffeine were detected in groundwater samples
from Europe at concentrations of 2.88, 3.60 and 4.50 μg/L, respectively [16],
suggesting a high mobility of these chemicals in soil. Likewise, many studies have
demonstrated that edible plants growing in API-contaminated soils accumulate and
translocate APIs to aerial parts [11]. Furthermore, APIs may cause biochemical and
physiological adverse effects in plants, negatively affecting their growth and development [7]. As a result, non-target organisms including human beings may be
exposed to API through the consumption of contaminated edible plants. For example, bee exposure to pharmaceuticals accumulated in pollen and nectar from zucchini
flowers was modelled for carbamazepine, and outcomes revealed that honeybee
colonies as well as the bee behaviour could be seriously affected by moderate
hydrophobic APIs [21]. Nevertheless, field surveys are still needed to draw solid
conclusions about exposure levels of wildlife to API-contaminated plants.
Soil functioning is also altered by APIs. Although biodegradation is the major
dissipation route [22, 23], these chemicals are able to alter soil microbial activity and
community [19] and soil enzyme activities [24–26]. Because soil enzyme activities
catalyse most chemical reactions involved in the transformation and decomposition
of organic matter, and nutrient cycling [27], their alteration by APIs could lead to soil
degradation. Therefore, affordable mitigating measures and remediation strategies
should be taken into account to reduce the potential environmental risks of APIs. In
this context, the use of earthworms emerges as a promising strategy for reducing API
concentration and toxicity at the source (treatment of biosolids and manure) and in
agricultural soils receiving continual input of APIs.
This chapter describes the mechanisms and technical aspects linked to earthworms’ capacity to remediate API-contaminated soils and amendments. The first
section makes a brief overview of the earthworm effects on soil functioning,
therefore providing insights into the importance of these organisms in API degradation (Sect. 2). The third section provides data on toxic effects of APIs in earthworms: a knowledge needed to propose these organisms as biological vectors of API
biodegradation. The fourth and fifth sections consider two options for using earthworms in managing API residues: vermicomposting of organic residues such as
biosolids and manure (ex situ vermiremediation) and inoculation of soils with
earthworms (in situ vermiremediation). The sixth section discuss how to improve
API vermiremediation by using biochar. The last section will identify knowledge
gaps that require further research to boost the use of earthworms for enhancing the
natural attenuation of agricultural soil against APIs and other organic pollutants.
2 Impact of Earthworms on Soil Quality
The term soil quality defines the “capacity of a specific kind of soil to function,
within natural or managed ecosystem boundaries, to sustain plant and animal
productivity, maintain or enhance water and air quality, and support human health
342
J. C. Sanchez-Hernandez