Fate of triclosan and triclocarban in soil columns with and without biosolids surface application

Abstract

The leaching and transformation behaviors of triclosan (TCS) and triclocarban (TCC) in soil columns (20 cm high, 4 cm in diameter) packed with an agricultural soil (Roxana very fine sandy loam) with and without biosolids surface application were investigated. The column leachates and soil samples were analyzed for TCS, TCC, and their transformation products. Significantly more TCS was transformed compared with TCC. Surface application of biosolids significantly retarded their transformation. Downward movement of TCS and TCC occurred within a 10-cm soil depth. Methyl-TCS was not detectable in the leachates but was detected in the top 5-cm soil layer, with more appearing in the biosolids-applied soil. At the end of the column study, carbanilide (CBA) was the only detectable TCC reductive dechlorination product in the soil. No TCC reductive dechlorination products were detectable in the leachates. Detection of 3,4-dichloroaniline (3,4-DCA) and 4-chloroaniline (4-CA) suggested the occurrence of TCC hydrolysis. Rapid leaching of 4-CA through the soil column was observed. The 3,4-DCA was detected throughout the entire 20-cm depth of the soil column but not in the leachates. The fact that only small percentages of the transformed TCS and TCC appeared, after a 101-d column study, in the forms of the products analyzed suggested that either the investigated transformation pathways were minor pathways or further rapid transformation of those products had occurred.

Partitioning and Degradation of Triclosan and Formation of Methyl-Triclosan in Water-Sediment Systems

“…In agricultural soils receiving sewage sludge, 39-66 % of the TCS was found transformed to M-TCS under field conditions (Butler et al 2012). However, Kwon and Xia (2012) reported that only 12.1 and 1.67 % of transformed TCS molecules were in the methylated form in the soil column with and without surface application of biosolids, respectively. Biosolid application significantly reduced the TCS transformation rate while enhanced the biological methylation TCS.…”

Effect of composting and soil type on dissipation of veterinary antibiotics in land-applied manures

“…Although there is limited information comparing the environmental fate of manure-borne versus spiked antibiotics, studies of biosolids have demonstrated significantly faster dissipation rates of the antimicrobial triclosan when spiked directly into soils compared to when it is biosolids-borne (Kwon and Xia, 2012). Thus, decreased diffusion, increased sorption, and reduced bioavailability of organic amendment-borne could contribute to prolonged persistence, compared to predicted values and those determined using spiked soils.…”

Transformation Products and Human Metabolites of Triclocarban and Triclosan in Sewage Sludge Across the United States

“…17,43 The former process is speculated to occur under anaerobic, reducing conditions 16 through the action of exclusively anaerobic dechlorinating microorganisms, 11 analogous to anaerobic reductive dechlorination of trichloroethene. 44 Previously, it has been shown that TCC dechlorination products can be detected in freshwater and brackish sediments downstream of effluent discharge sites, 1,11,45 but it remains unknown whether dechlorination occurs before and/or after environmental discharge.…”

“…43,47−51 Even though MeTCS retains some toxicity for microbial activity, 52 the methylation of TCS will mitigate microbial growth inhibition and avert ultraviolet light-driven dioxin formation. 52−54 MeTCS is also more persistent than its parent compound and is more prone to bioaccumulate in fish; 55 a more detailed (eco)toxicological evaluation of MeTCS is therefore warranted.Even though TCC and TCS transformation mechanisms have been described previously and attributed to different stages of WWTPs, little to no research has been performed relating to their geographical distribution, significance at different sites, and stability over time.…”