of triclosan (1, 10 and 100 mg/kg) in soils varied between 5.8 and 6.5%
(cumulative recovery of
14 CO 2 ) over a period of 42 days [80]. The finding
suggests that metabolites may persist in soil with potential toxicity on soil
organisms and soil function. For example, triclosan is photochemically
decomposed into the toxic metabolites 2,8-dichlorodibenzo-p-dioxin
(2,8-DCDD) and 2,4-dichlorophenol (2,4-DCP), which are very unstable in
aqueous solutions [196], but their organic carbon-adsorption coefficients (K OC )
suggest a high affinity for the soil organic matter (log K OC ¼ 3.2 for 2,8-DCDD
and log K OC ¼ 2.8 for 2,4-DCP; estimated values generated using the EPISuite™
software, USEPA, www.chemspider.com).
5. Synergistic effects of APIs and other environmental contaminants. A vast variety
of organic and inorganic pollutants may occur in agricultural soils. For example,
PAHs, PCBs, polybrominated diphenyl ethers and phthalates are frequently
detected in agricultural soils irrigated with reclaimed wastewater or fertilised
with biosolids or municipal composts [197–200]. Additionally, chemical control
of agricultural pests may lead to accumulation of pesticides in soil. Therefore,
toxic effects and degradation of APIs should be investigated in a context of
pollutant mixture, which is the most realistic scenario in the agroecosystem.
Furthermore, the high capacity of biochar to retain environmental pollutants,
including APIs [176, 201], may result in toxic biochar at long term because of
high concentrations of pollutants onto its surface. Therefore, this concern must be
clarified in detail to know whether biochar could behave as a secondary source of
soil pollution under specific soil conditions (e.g. changes in pH, moisture or
biodiversity).
6. Life cycle assessment for earthworm-biochar bioremediation technology. Life
cycle assessment (LCA) consists of a set of standardised and robust tools for
appraising the efficiencies of methodologies and processes aimed to attend the
decision-making related to environment protection and efficiency of the process
(ISO14040:2006, ISO 2006). In the case of bioremediation of contaminated sites,
LCA has been used to identify adverse impacts from the application of remediation strategies and consequently to take alternative remediation actions
[202]. LCA can be used before initiating the remediation action (predictive) to
select the best option according to technical, economic and environmental variables or when the remediation action is completed (prospective LCA). In the latter
case, the scope of LCA is to know the environmental impacts derived from the
applied remediation technology. For example, an LCA study of systems for
biochar production revealed that some issues such as costs related to the pyrolysis
process as well as feedstock selection, management and transportation hampered
the economic viability of biochar technology, therefore compromising its affordability as a strategy for climate change mitigation [203]. The systematic review by
Matustík et al. [204] on LCA of biochar technology evidenced that although the
application of biochar to agricultural soils provides important environmental and
economic benefits, there are still some issues that require further understanding
and improvements such as the mechanisms underpinning the biochar effects
on soil quality and crop yield and the use of low-tech pyrolysis systems
Vermiremediation of Pharmaceutical-Contaminated Soils and Organic Amendments
363
(cumulative recovery of
14 CO 2 ) over a period of 42 days [80]. The finding
suggests that metabolites may persist in soil with potential toxicity on soil
organisms and soil function. For example, triclosan is photochemically
decomposed into the toxic metabolites 2,8-dichlorodibenzo-p-dioxin
(2,8-DCDD) and 2,4-dichlorophenol (2,4-DCP), which are very unstable in
aqueous solutions [196], but their organic carbon-adsorption coefficients (K OC )
suggest a high affinity for the soil organic matter (log K OC ¼ 3.2 for 2,8-DCDD
and log K OC ¼ 2.8 for 2,4-DCP; estimated values generated using the EPISuite™
software, USEPA, www.chemspider.com).
5. Synergistic effects of APIs and other environmental contaminants. A vast variety
of organic and inorganic pollutants may occur in agricultural soils. For example,
PAHs, PCBs, polybrominated diphenyl ethers and phthalates are frequently
detected in agricultural soils irrigated with reclaimed wastewater or fertilised
with biosolids or municipal composts [197–200]. Additionally, chemical control
of agricultural pests may lead to accumulation of pesticides in soil. Therefore,
toxic effects and degradation of APIs should be investigated in a context of
pollutant mixture, which is the most realistic scenario in the agroecosystem.
Furthermore, the high capacity of biochar to retain environmental pollutants,
including APIs [176, 201], may result in toxic biochar at long term because of
high concentrations of pollutants onto its surface. Therefore, this concern must be
clarified in detail to know whether biochar could behave as a secondary source of
soil pollution under specific soil conditions (e.g. changes in pH, moisture or
biodiversity).
6. Life cycle assessment for earthworm-biochar bioremediation technology. Life
cycle assessment (LCA) consists of a set of standardised and robust tools for
appraising the efficiencies of methodologies and processes aimed to attend the
decision-making related to environment protection and efficiency of the process
(ISO14040:2006, ISO 2006). In the case of bioremediation of contaminated sites,
LCA has been used to identify adverse impacts from the application of remediation strategies and consequently to take alternative remediation actions
[202]. LCA can be used before initiating the remediation action (predictive) to
select the best option according to technical, economic and environmental variables or when the remediation action is completed (prospective LCA). In the latter
case, the scope of LCA is to know the environmental impacts derived from the
applied remediation technology. For example, an LCA study of systems for
biochar production revealed that some issues such as costs related to the pyrolysis
process as well as feedstock selection, management and transportation hampered
the economic viability of biochar technology, therefore compromising its affordability as a strategy for climate change mitigation [203]. The systematic review by
Matustík et al. [204] on LCA of biochar technology evidenced that although the
application of biochar to agricultural soils provides important environmental and
economic benefits, there are still some issues that require further understanding
and improvements such as the mechanisms underpinning the biochar effects
on soil quality and crop yield and the use of low-tech pyrolysis systems
Vermiremediation of Pharmaceutical-Contaminated Soils and Organic Amendments
363