|LOZANO, N - University Of Maryland|
|RAMIREZ, M - District Of Columbia Water & Sewer Authority (DCWASA)|
|TORRENTS, A - University Of Maryland|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/17/2013
Publication Date: N/A
Technical Abstract: Biosolids contain synthetic chemicals such as Triclosan (TCS) which is heavily used as an antibacterial compound with endocrine disruptor properties. Thus, TCS has the potential to alter soil microbial communities and disrupt endocrine functions if they move offsite. Due to its low solubility and relatively high Kow, it’s levels remain high in biosolids. Land application of biosolids represents an important route for the introduction of TCS into the environment. This study investigates the persistence of triclosan (TCS), and its biodegradation product, Methyltriclosan (MeTCS) in an experimental agricultural plot after land application of biosolids. For this study, biosolids from a well-characterized source were applied to a small agricultural field (0.24 ha). The experimental plot was gridded and a total of 42 surface soil samples were collected at pre-determined times over 3 years and analyzed for TCS and MeTCS. Soil-assimilated concentration of TCS slowly increased to a maximum average level of 63.7 ± 14.1 ng g-1 dry wt. which was far below the predicted maximum concentration of 307.5 ng g-1 dry wt. TCS disappearance corresponded with MeTCS appearance, suggesting in-situ biodegradation. The results suggest that soil incorporation and degradation processes are taking place simultaneously and that TCS background levels are achieved within two years. TCS half-life (t0.5) was determined as 104 d and MeTCS t0.5, was estimated at 443 d. Using the MeTCS t0.5 value, we estimate that even 4 years after application (which is the average recommended time between repeated biosolids applications), MeTCS is still present at above background levels (7.1 ng g-1 dry wt.). Hence, MeTCS would have the ability to build up in the soils after multiple biosolids applications. Our estimates suggest that it would take 7.2 years for soil MeTCS levels to reach background concentrations.