2.2 Occurrence in Soil
Data on the concentration of PhACs in agricultural soil is sparse. Table 1 shows the
more prevalent contaminants detected in agricultural soils irrigated with TWW. On
this topic, a recent study on the occurrence of pharmaceuticals in soils irrigated with
reclaimed wastewater conducted by Biel-Maeso et al. [25] showed the prevalence of
analgesic and anti-inflammatories, followed by antibiotics and psychiatric drugs on
surface soils (0–20 cm). All the PhAC concentrations summed up in soils were
between 2 and 15 ng g
À1 d.w. The highest concentrations were detected for the
compounds diclofenac and caffeine, followed by hydrochlorothiazide, mefenamic
acid, flumequine, and carbamazepine. Biel-Maeso group [41] demonstrated the
occurrence of a wide number of PhACs in vertical soil profiles up to 175 cm,
demonstrating also potential leaching. Gielen et al. [42] reported the impact of soil
type on the removal or leaching of PhACs such as carbamazepine, caffeine, ibuprofen, naproxen, and salicylic acid. Only carbamazepine and caffeine were discovered
in the soil-water leachates. Carbamazepine behaved very conservatively in the sand
soil, and it was largely removed in the investigated volcanic soil. Lamotrigine has
similar pharmacological activity, while carbamazepine, however, has distinct chemical structure and properties that can affect its environmental behavior. In fact, Paz
and co-workers [43] reported a high sorption affinity of lamotrigine to soil with
respect to carbamazepine. The triazine ring and amino group give the ability of the
molecules to form hydrogen bonds with functional groups on polar soil organic
matter. Borgman and Chefetz [44] demonstrated the importance of organic matter
content for lamotrigine sorption to soil, increasing it when biosoilds were added to
sandy soil. The accumulation of carbamazepine, sulfamethoxazole, and ciprofloxacin after long-term irrigation of soils with untreated wastewater was also reported by
Dalkmann and co-workers [28]. The accumulation of sulfamethoxazole and ciprofloxacin in soil was not accompanied by an increase of relative abundance of
respective resistance genes. Also, Kinney et al. [19] found that carbamazepine,
acetaminophen, fluoxetine, caffeine, and erythromycin accumulated in the upper
30-cm soil layer. In arid zones, wastewater irrigation is extensively applied, which
can lead to accumulation of PhACs in soil and leaching to groundwater. However,
not all compounds present in wastewater effluent accumulated in soil. For example,
Durán-Alvarez et al. [31] reported the concentrations of acidic pharmaceuticals in
soil irrigated by untreated wastewater for 90 years were less than 1 ng g
À1 . In a study
developed in Mexico by Gibson et al. [33], carbamazepine and triclosan had
accumulated by a factor of 603–942% and 519–858%, respectively. In contrast,
diclofenac, naproxen, and bezafibrate were not retained and therefore did not
accumulate in soil. The persistence of PhACs can potentially enrich the reservoir
of antimicrobial resistance genes in soils [45].
Besides the accumulation of PhACs, the possible formation of stable transformation products (TPs) in soil was reported in few studies (see Table 1). For instance,
Koda et al. [35] reported the persistence of carbamazepine and its metabolites
(10,11-epoxide; 10,11-dihydrocarbamazepine; and trans-10,11-dihydro-10,11Soil Sorption and Degradation Studies of Pharmaceutical Compounds Present in. . .
147
Data on the concentration of PhACs in agricultural soil is sparse. Table 1 shows the
more prevalent contaminants detected in agricultural soils irrigated with TWW. On
this topic, a recent study on the occurrence of pharmaceuticals in soils irrigated with
reclaimed wastewater conducted by Biel-Maeso et al. [25] showed the prevalence of
analgesic and anti-inflammatories, followed by antibiotics and psychiatric drugs on
surface soils (0–20 cm). All the PhAC concentrations summed up in soils were
between 2 and 15 ng g
À1 d.w. The highest concentrations were detected for the
compounds diclofenac and caffeine, followed by hydrochlorothiazide, mefenamic
acid, flumequine, and carbamazepine. Biel-Maeso group [41] demonstrated the
occurrence of a wide number of PhACs in vertical soil profiles up to 175 cm,
demonstrating also potential leaching. Gielen et al. [42] reported the impact of soil
type on the removal or leaching of PhACs such as carbamazepine, caffeine, ibuprofen, naproxen, and salicylic acid. Only carbamazepine and caffeine were discovered
in the soil-water leachates. Carbamazepine behaved very conservatively in the sand
soil, and it was largely removed in the investigated volcanic soil. Lamotrigine has
similar pharmacological activity, while carbamazepine, however, has distinct chemical structure and properties that can affect its environmental behavior. In fact, Paz
and co-workers [43] reported a high sorption affinity of lamotrigine to soil with
respect to carbamazepine. The triazine ring and amino group give the ability of the
molecules to form hydrogen bonds with functional groups on polar soil organic
matter. Borgman and Chefetz [44] demonstrated the importance of organic matter
content for lamotrigine sorption to soil, increasing it when biosoilds were added to
sandy soil. The accumulation of carbamazepine, sulfamethoxazole, and ciprofloxacin after long-term irrigation of soils with untreated wastewater was also reported by
Dalkmann and co-workers [28]. The accumulation of sulfamethoxazole and ciprofloxacin in soil was not accompanied by an increase of relative abundance of
respective resistance genes. Also, Kinney et al. [19] found that carbamazepine,
acetaminophen, fluoxetine, caffeine, and erythromycin accumulated in the upper
30-cm soil layer. In arid zones, wastewater irrigation is extensively applied, which
can lead to accumulation of PhACs in soil and leaching to groundwater. However,
not all compounds present in wastewater effluent accumulated in soil. For example,
Durán-Alvarez et al. [31] reported the concentrations of acidic pharmaceuticals in
soil irrigated by untreated wastewater for 90 years were less than 1 ng g
À1 . In a study
developed in Mexico by Gibson et al. [33], carbamazepine and triclosan had
accumulated by a factor of 603–942% and 519–858%, respectively. In contrast,
diclofenac, naproxen, and bezafibrate were not retained and therefore did not
accumulate in soil. The persistence of PhACs can potentially enrich the reservoir
of antimicrobial resistance genes in soils [45].
Besides the accumulation of PhACs, the possible formation of stable transformation products (TPs) in soil was reported in few studies (see Table 1). For instance,
Koda et al. [35] reported the persistence of carbamazepine and its metabolites
(10,11-epoxide; 10,11-dihydrocarbamazepine; and trans-10,11-dihydro-10,11Soil Sorption and Degradation Studies of Pharmaceutical Compounds Present in. . .
147