Degradation Kinetics and Metabolites of Carbamazepine in Soil

Abstract

The antiepileptic drug carbamazepine (CBZ) is one of the most frequently detected human pharmaceuticals in wastewater effluents and biosolids. Soil is a primary environmental compartment receiving CBZ through wastewater irrigation and biosolid application. In this study, we explored the transformation of CBZ to biologically active intermediates in soil. Both (14)C labeling and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to track transformation kinetics and identify major degradation intermediates. Through 120 days of incubation under aerobic conditions, mineralization of CBZ did not exceed 2% of the spiked rate in different soils. Amendment of biosolids further suppressed mineralization. The fraction of non-extractable (i.e., bound) residue also remained negligible (<5%). On the other hand, CBZ was transformed to a range of degradation intermediates, including 10,11-dihydro-10-hydroxycarbamazepine, carbamazepine-10,11-epoxide, acridone-N-carbaldehyde, 4-aldehyde-9-acridone, and acridine, of which acridone-N-carbaldehyde was formed in a large fraction and appeared to be recalcitrant to further degradation. Electrocyclization, ring cleavage, hydrogen shift, carbonylation, and decarbonylation contributed to CBZ transformative reactions in soil, producing biologically active products. The persistence of the parent compound and formation of incomplete intermediates suggest that CBZ has a high risk for off-site transport from soil, such as accumulation into plants and contamination of groundwater.

Dissipation of triclosan, triclocarban, carbamazepine and naproxen in agricultural soil following surface or sub-surface application of dewatered municipal biosolids

“…This result is consistent with greater recalcitrance of CBZ to biodegradation. Carbamazepine was reported to be dissipated only very slowly in three different soils with the half-life ranging from 46 to 173 days (Li et al, 2013). In this study, over a 120-day laboratory incubation with only negligible amounts of 14 C-CBZ were mineralized or formed non-extractable residues, recovery of 14 C in the form of extractable parent and various transformation products was almost stoichiometric.…”

“…In Canada, an estimated 53-62 tons are sold annually (McLaughlin and Belknap, 2008). Based on previous experience, we anticipated that CBZ would be persistent, and NAP rapidly dissipated in soil under permissive conditions (Li et al, 2013;Topp et al, 2008a).…”

Plant uptake of pharmaceutical and personal care products from recycled water and biosolids: a review

“…14 C-naproxen and 14 C-diclofenac were found to be mainly (up to 50-80%) mineralized to 14 CO 2 in different soils (Dodgen et al, 2014;Topp et al, 2008), while only a small part of 14 C-carbamazepine (b1.2%) and 14 C-acetaminophen (17%) were mineralized . Some metabolites of pharmaceuticals in soils were identified by using a combination of techniques, including 14 C labeling, LC fractionation, and LC-MS/MS structural elucidation (Dodgen et al, 2014;Li et al, 2013Li et al, , 2014. It was reported that acetaminophen was rapidly converted to various metabolites in soils , while slow and limited transformation was observed for carbamazepine .…”

“…It was reported that irrigation with treated wastewater had no discernable effect on the biodegradation of PPCPs in soil (Grossberger et al, 2014), whereas biosolids amendment generally inhibited the degradation of PPCPs (Monteiro and Boxall, 2009;Li et al, 2013Li et al, , 2014, therefore prolonging their persistence in soil. The reason for this inhibition of degradation may be that biosolids amendment usually increases the organic matter content in soil, leading to increased sorption of PPCPs to soil (and hence decreased bioavailability) .…”

Occurrence of pharmaceuticals in municipal wastewater, in the recipient water, and sedimented particles of northern Lake Päijänne

“…This is most likely caused by the fact that carbamazepine forms a range of degradation intermediates in soil which further reduce the amount of parent compound (Li et al 2013). Additionally, relatively small amount of carbamazepine is annually used in Finland (3200 kg), and therefore, small concentrations are released from the WWTP (Table 1).…”