they were relatively persistent under anaerobic conditions. For instance, over 90% of
nadolol was degraded in aerobic soils after 4 days of incubation, while only 18–24%
was lost in the absence of oxygen after 1 month, resulting in half-life values between
95 and 103 days. Biosolid amendments also tend to contribute to PhACs accumulation in soil. Biodegradation of PhACs is correlated with soil properties, and it is
well known that the application of biosolids have effects on the soil properties
[48]. It was reported that biosolid amendments could inhibit PhAC degradation
due to an increase of the organic matter content in soil, leading to increase sorption
of PhACs to soil and prolonging their persistence [36].
2.2.2 Sorption
Sorption has often been the most studied process because it determines the mobility
of PhACs in the porous media. Doretto et al. [51] studied the behavior of sulfonamides (sulfadimethoxine, sulfaquinoxaline, and sulfamethazine) in the 0–20-cm
upper layer of four different soils in Brazil. The PhAC adsorption/desorption data
fitted the Freundlich isotherms well in the logarithmic form. The adsorption coefficients obtained suggesting that all target PhACs were weakly adsorbed on the soils.
The Freundlich desorption coefficients suggest that the sulfonamides tend to leached
from soil whit high sand and low organic carbon contents. These results suggest that
there is potential groundwater contamination by sulfonamides. Biel-Maeso et al. [41]
have also reported the sorption of PhACs and artificial sweeteners in two soils under
aerobic and anaerobic conditions. Equilibrium sorption data fitted well to a
Freundlich isotherm model [41, 48]. The higher K f was determined for cyclamate
(162 L kg
À1 ) and acesulfame (156 L kg
À1 ), while the lowest sorption coefficients
were measured for ibuprofen (1–7 L kg
À1 ). Pan and Chu [50] evaluated the
adsorption of five antibiotics in sterilized and non-sterilized agricultural soils
under aerobic and anaerobic conditions. The five antibiotics exhibited adsorption
affinities on soil in the descending order: tetracycline > norfloxacin > erythromycin > chloramphenicol > sulfamethazine. Sulfamethazine was the most mobile
antibiotic in soil among the five compounds, while tetracycline was the least mobile.
Mobility depends on the presence of soil organic matter (SOM) and chemical and
environmental properties [47, 52]. There is limited information on how the physicochemical properties of different soils can influence the sorption of PhACs, and
prediction is elusive due to the complexity of interactions specifically between polar
ionic contaminants and mineral surfaces in the presence of DOM.
2.2.3 Non-extractable Residues (NER)
Contaminants entering the environment undergo various processes already
described, such as sorption and biodegradation, but in addition, a proportion will
be immobilized in soil by NER. Conforming to the IUPAC definition [53], NER in
plants and soil are defined as chemical substances that remain in soil or sediment
Soil Sorption and Degradation Studies of Pharmaceutical Compounds Present in. . .
157
nadolol was degraded in aerobic soils after 4 days of incubation, while only 18–24%
was lost in the absence of oxygen after 1 month, resulting in half-life values between
95 and 103 days. Biosolid amendments also tend to contribute to PhACs accumulation in soil. Biodegradation of PhACs is correlated with soil properties, and it is
well known that the application of biosolids have effects on the soil properties
[48]. It was reported that biosolid amendments could inhibit PhAC degradation
due to an increase of the organic matter content in soil, leading to increase sorption
of PhACs to soil and prolonging their persistence [36].
2.2.2 Sorption
Sorption has often been the most studied process because it determines the mobility
of PhACs in the porous media. Doretto et al. [51] studied the behavior of sulfonamides (sulfadimethoxine, sulfaquinoxaline, and sulfamethazine) in the 0–20-cm
upper layer of four different soils in Brazil. The PhAC adsorption/desorption data
fitted the Freundlich isotherms well in the logarithmic form. The adsorption coefficients obtained suggesting that all target PhACs were weakly adsorbed on the soils.
The Freundlich desorption coefficients suggest that the sulfonamides tend to leached
from soil whit high sand and low organic carbon contents. These results suggest that
there is potential groundwater contamination by sulfonamides. Biel-Maeso et al. [41]
have also reported the sorption of PhACs and artificial sweeteners in two soils under
aerobic and anaerobic conditions. Equilibrium sorption data fitted well to a
Freundlich isotherm model [41, 48]. The higher K f was determined for cyclamate
(162 L kg
À1 ) and acesulfame (156 L kg
À1 ), while the lowest sorption coefficients
were measured for ibuprofen (1–7 L kg
À1 ). Pan and Chu [50] evaluated the
adsorption of five antibiotics in sterilized and non-sterilized agricultural soils
under aerobic and anaerobic conditions. The five antibiotics exhibited adsorption
affinities on soil in the descending order: tetracycline > norfloxacin > erythromycin > chloramphenicol > sulfamethazine. Sulfamethazine was the most mobile
antibiotic in soil among the five compounds, while tetracycline was the least mobile.
Mobility depends on the presence of soil organic matter (SOM) and chemical and
environmental properties [47, 52]. There is limited information on how the physicochemical properties of different soils can influence the sorption of PhACs, and
prediction is elusive due to the complexity of interactions specifically between polar
ionic contaminants and mineral surfaces in the presence of DOM.
2.2.3 Non-extractable Residues (NER)
Contaminants entering the environment undergo various processes already
described, such as sorption and biodegradation, but in addition, a proportion will
be immobilized in soil by NER. Conforming to the IUPAC definition [53], NER in
plants and soil are defined as chemical substances that remain in soil or sediment
Soil Sorption and Degradation Studies of Pharmaceutical Compounds Present in. . .
157