Fate of triclocarban in agricultural soils after biosolid applications

Authors: LOZANO, NURIA - University Of Cantabria; Rice, Clifford; RAMIREZ, MARK - District Of Columbia Water & Sewer Authority (DCWASA); TORRENTS, ALBA - University Of Maryland

Submitted to: Environmental Science and Pollution Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2017
Publication Date: 1/1/2018
Citation: Lozano, N., Rice, C., Ramirez, M., Torrents, A. 2018. Fate of triclocarban in agricultural soils after biosolid applications. Environmental Science and Pollution Research. 25:222-223.

Interpretive Summary: Triclocarban (TCC) is a commonly used antibacterial ingredient in consumer soaps. Because of the concern for the harmful properties of TCC to animal life, this use is being banned starting September 7, 2017. The chemical however, is very resistant to degradation and binds strongly to solids as they pass through waste water treatment plants. These waste treatment plant biosolids are popularly utilized as soil amendments to agricultural fields. It was discovered that TCC persists in these fields after treatment with biosolids and even build up in soils receiving multiple applications of biosolids over time. The two most important parameters controlling TCC top soil concentrations were the biosolids application rates and the amounts of time after application. TCC concentration analyzed 7 and 8 years after biosolids application were often elevated above concentrations in untreated fields. The estimated time for one-half of the initial concentrations in the treated soils to be removed was 288 days for farms receiving only one application of biosolids. These dissipation half lives are much longer than values estimated from laboratory incubations. Therefore, environmental exposure from biosolid-treated fields could be a problem especially from a microbiome perspective. This information will be useful to scientists and policymakers.

Technical Abstract: Triclocarban [N-(4-chlorophenyl)-N-(3,4-dichlorophenyl) urea] (TCC), is an antimicrobial agent utilized in a variety of consumer products. It is commonly released into domestic wastewaters and is not fully removed in the waste water treatment plants (WWTP). Most of the TCC is still present after the water treatment and attached to the biosolids where it ends up in the environment when agricultural land is fertilized with biosolids. This study examines the occurrence of TCC in biosolids and its fate in biosolid-treated soils. TCC level in the biosolids sampled periodically in a large WWTP over two years was 18.8 ± 0.68 mg kg-1 dry wt. (mean ± SE). Surface soil samples were collected in 26 farms located in northern Virginia, US. The types of farms were selected for sampling; farms receiving no biosolids, farms with single biosolid applications, and those receiving multiple biosolid applications starting in 1992. Application of TCC-laden biosolids caused elevated concentrations of TCC to occur in all of the soils. No TCC removal was observed in farms receiving single biosolids application after 7-9 months. TCC is present in the soils several years after biosolids application for farms receiving single and multiple biosolids applications. The two most important parameters controlling TCC top soil concentrations were the biosolids application rates and the period after application. TCC concentration analyzed 7 and 8 years after biosolids application were 45.8 ± 6.09 and 72.4 ± 15.3 ng g-1 dry wt., respectively, showing its high persistence in soils and a TCC build-up. A soil TCC half life of 287.5 ± 45.5 d. was estimated in the farms that received single biosolid applications.