dihydroxycarbamazepine) on 13 different soils. This phenomenon with low carbamazepine sorption may cause adverse effects on the environment due the possibility
to leaching to groundwater. Similar behavior was observed by Butler and co-workers
[40] on the fate of triclosan and its major metabolite methyl-triclosan that is more
lipophilic and potentially more persistent than the parent compound [46]. After
1 year, both triclosan and methyl-triclosan remained in the top 10 cm layer in all
three investigated agricultural soils.
Sorption of PhACs and personal care products to soil is influenced by the soil
pore water chemistry and the type of mineral and organic sorbents [47]. The
retention of some analytes may reflect the interactions of PhAC physicochemical
properties and soil characteristics with the different locations, and it is not only
consequences of their high abundance in wastewater.
To understand the fate of PhACs in soil, it is necessary to investigate all processes
that can be involved such as biodegradation, sorption, and the formation of NER, as
well as to understand what parameters can influence these processes (e.g., pH, soil
texture, particulate and dissolved organic matter, ion exchange capacity, hydrophobicity of PhACs, and their charge).
2.2.1 Biodegradation
Biotransformation of PhACs is the most important and effective way for their
removal in soil. Microorganisms have the ability to interact with chemicals, both
chemically and physically, leading to structural changes or to complete degradation
of the target molecules. For example, after 45-d incubation time, the fraction of
degraded clofibric acid and diclofenac in non-sterile and sterilized agricultural soils
was 88–100% (non-sterile) and 33–43% (sterilized), respectively, indicating a significant role of microorganisms in degrading these pharmaceuticals. The degradation
rate decreased at increasing initial chemical concentrations in soil, implying that the
microbial activity was inhibited with high chemical loading levels [48]. In soil,
microorganisms metabolize PhACs aerobically and/or anaerobically. For instance,
Thelusmond et al. [49] reported the biodegradation of diclofenac, carbamazepine,
and triclocarban in four agricultural soils. Rapid degradation of diclofenac was
observed under aerobic conditions with respect to carbamazepine and triclocarban.
Specific phylotypes were found to be associated with the biodegradation processes.
Pan and Chu [50] observed anaerobic and aerobic adsorption and degradation of five
antibiotics. All antibiotics presented higher degradation under aerobic conditions
with half-lives ranging between 2.9 and 43.3 days in non-sterilized soil and 40.8 to
86.6 days in sterilized soil. This study highlighted that biodegradation depends on
antibiotic physicochemical proprieties, soil texture, and microbial activity as well as
oxygen content. This was also confirmed by Biel-Maeso [41], who demonstrated
that
nine
PhACs
(nadolol,
sulfamethizole,
sulfamethoxazole,
sulfamethoxypyridazine, carbamazepine, ibuprofen, diclofenac, hydrochlorothiazide, and gemfibrozil) and four artificial sweeteners (acesulfame, saccharin, cyclamate and sucralose) in soil had a high degradation rate under aerobic conditions, but
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to leaching to groundwater. Similar behavior was observed by Butler and co-workers
[40] on the fate of triclosan and its major metabolite methyl-triclosan that is more
lipophilic and potentially more persistent than the parent compound [46]. After
1 year, both triclosan and methyl-triclosan remained in the top 10 cm layer in all
three investigated agricultural soils.
Sorption of PhACs and personal care products to soil is influenced by the soil
pore water chemistry and the type of mineral and organic sorbents [47]. The
retention of some analytes may reflect the interactions of PhAC physicochemical
properties and soil characteristics with the different locations, and it is not only
consequences of their high abundance in wastewater.
To understand the fate of PhACs in soil, it is necessary to investigate all processes
that can be involved such as biodegradation, sorption, and the formation of NER, as
well as to understand what parameters can influence these processes (e.g., pH, soil
texture, particulate and dissolved organic matter, ion exchange capacity, hydrophobicity of PhACs, and their charge).
2.2.1 Biodegradation
Biotransformation of PhACs is the most important and effective way for their
removal in soil. Microorganisms have the ability to interact with chemicals, both
chemically and physically, leading to structural changes or to complete degradation
of the target molecules. For example, after 45-d incubation time, the fraction of
degraded clofibric acid and diclofenac in non-sterile and sterilized agricultural soils
was 88–100% (non-sterile) and 33–43% (sterilized), respectively, indicating a significant role of microorganisms in degrading these pharmaceuticals. The degradation
rate decreased at increasing initial chemical concentrations in soil, implying that the
microbial activity was inhibited with high chemical loading levels [48]. In soil,
microorganisms metabolize PhACs aerobically and/or anaerobically. For instance,
Thelusmond et al. [49] reported the biodegradation of diclofenac, carbamazepine,
and triclocarban in four agricultural soils. Rapid degradation of diclofenac was
observed under aerobic conditions with respect to carbamazepine and triclocarban.
Specific phylotypes were found to be associated with the biodegradation processes.
Pan and Chu [50] observed anaerobic and aerobic adsorption and degradation of five
antibiotics. All antibiotics presented higher degradation under aerobic conditions
with half-lives ranging between 2.9 and 43.3 days in non-sterilized soil and 40.8 to
86.6 days in sterilized soil. This study highlighted that biodegradation depends on
antibiotic physicochemical proprieties, soil texture, and microbial activity as well as
oxygen content. This was also confirmed by Biel-Maeso [41], who demonstrated
that
nine
PhACs
(nadolol,
sulfamethizole,
sulfamethoxazole,
sulfamethoxypyridazine, carbamazepine, ibuprofen, diclofenac, hydrochlorothiazide, and gemfibrozil) and four artificial sweeteners (acesulfame, saccharin, cyclamate and sucralose) in soil had a high degradation rate under aerobic conditions, but
156
M. Brienza et al.