Journal of Environmental Management 269 (2020) 110838 Available online 30 May 2020 0301-4797/© 2020 Elsevier Ltd. All rights reserved. Research article Use of biomass ash to reduce toxicity affecting soil bacterial community growth due to tetracycline antibiotics V. Sant� as-Miguel a, * , M.J. Fern� andez-Sanjurjo b , A. Nú~ nez-Delgado b , E. � Alvarez-Rodríguez b , M. Díaz-Ravi ~ na c , M. Arias-Est� evez a , D. Fern� andez-Calvi ~ no a a � Area de Edafoloxía e Química Agrícola, Facultade de Ciencias, Universidade de Vigo, As Lagoas 1, 32004, Ourense, Spain b Departamento de Edafoloxía e Química Agrícola, Escola Polit� ecnica Superior de Enxe~ naría, Universidade de Santiago de Compostela, Campus Univ, 27002, Lugo, Spain c Departamento de Bioquímica del Suelo, Instituto de Investigaciones Agrobiol� ogicas de Galicia (IIAG/CSIC), Santiago de Compostela, Spain A R T I C L E INFO Keywords: Biomass ash Chlortetracycline Leucine incorporation Oxytetracycline Tetracycline ABSTRACT Tetracycline antibiotics (TA) used in veterinary medicine reach terrestrial ecosystems mostly via the repeated applications of animal manures and slurries on agricultural soils, where they may cause toxic effects on bacterial communities. In the current work, we studied the effcacy of adding doses of 0, 6, 24 and 48 g kg 1 of biomass ash (BA) to four different soils to reduce potential negative effects of tetracycline antibiotics. Specifcally, soil samples were polluted with different concentrations of tetracycline, oxytetracycline or chlortetracycline, and the bacterial community growth was estimated using the 3 H leucine incorporation technique. Soil amendment with BA increased soil pH (1.3–4.8 units), total carbon (0.7–5.8 g kg 1 ) and Fe and Al oxides concentrations (0.25–3.98 g kg 1 ), as well as bacterial activity (1–9 times compared to the control). In addition, BA amendment at high doses (24 or 48 g kg 1 ) resulted in a similar toxicity decrease for the three antibiotics, but with variations among soils. The reductions in antibiotics toxicity were very variable, ranging between 5% and 100% (total recovery). In view of that, the spreading of BA could be interesting as management practice to reduce risks of soil pollution and subsequent toxicity on bacterial communities due to tetracycline antibiotics. 1. Introduction Veterinary antibiotics are widely used for animal health, and even as animal growth promoters in countries where this parallel use is not banned (Anderson et al., 2005). These antibiotics reach terrestrial eco- systems via the repeated applications of animal manures and slurries as amendments on agricultural soils (Pan and Chu, 2017). Once in the soil, veterinary antibiotics may cause harmful effects on non-target organ- isms, such as soil bacterial communities (Warman, 1980). The presence of antibiotics in the soil may cause a reduction in microbial biodiversity (Thiele-Bruhn and Beck, 2005; Hammesfahr et al., 2008), infuence the growth and enzymatic activities of bacterial communities (Liu et al., 2009; Ma et al., 2016; Song et al., 2017; Sant� as-Miguel et al., 2020), and hence, ecological functions and functional stability (Zielezny et al., 2006; Demoling and Bååth, 2008; Pallecchi et al., 2008; Toth et al., 2011). Tetracyclines are the antibiotics most used in the European Union, especially tetracycline, oxytetracycline and chlortetracycline (European Medicines Agency. European Surveillance of Veterinary Antimicrobial Consumption, 2016), which motivated that previous studies have focused on the effects of tetracycline residues on soil microbial functions (Thiele-Bruhn, 2005; Yang et al., 2010; Liu et al., 2012; Ma et al., 2016; Song et al., 2017). It has been established that the main agents responsible for the sustainability of soils are microorganisms (Pulleman et al., 2012), since they are involved in nutrient cycles and renewal of organic matter (Thiele-Bruhn et al., 2012). Therefore, the correct growth of soil bacterial communities will help to maintain an optimal soil fertility and organic matter turnover. However, there are only few studies estimating the effects of tetracycline antibiotics on soil bacterial community growth (Rousk et al., 2008, 2009a; Sant� as-Miguel et al., 2020). These studies have shown a marked toxicity due to tetracycline antibiotics, which was highly dependent on soil characteristics. In order to prevent harmful effects of antibiotics accumulated into soils, the use of appropriate waste and/or by-products as soil amend- ments may be a low cost alternative aiding to decrease undesirable toxicity affecting soil bacterial communities. It has been previously * Corresponding author. E-mail address: vsantas@uvigo.es (V. Sant� as-Miguel). Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: http://www.elsevier.com/locate/jenvman https://doi.org/10.1016/j.jenvman.2020.110838 Received 18 February 2020; Received in revised form 11 May 2020; Accepted 24 May 2020