Photodegradation of polycyclic aromatic hydrocarbons in soils under a climate change base scenario Montse Marqu  es a, b , Montse Mari a, b , Carme Audí-Mir  o c , Jordi Sierra b, d , Albert Soler c , Martí Nadal a, * , Jos  e L. Domingo a a Laboratory of Toxicology and Environmental Health, School of Medicine, IISPV, Universitat Rovira i Virgili, Sant Llorenç 21, 43201 Reus, Catalonia, Spain b Environmental Engineering Laboratory, Departament d'Enginyeria Quimica, Universitat Rovira i Virgili, Av. Països Catalans 26, 43007 Tarragona, Catalonia, Spain c Grup de Mineralogia Aplicada i Geoquímica de Fluids, Departament de Cristal·lografia, Mineralogia i Dip osits Minerals, Facultat de Geologia, SIMGEO UB- CSIC, Universitat de Barcelona UB, Martí Franqu es s/n, 08028 Barcelona, Spain d Laboratory of Soil Science, Faculty of Pharmacy, Universitat de Barcelona, Av. Joan XXIII s/n, 08028 Barcelona, Catalonia, Spain highlights  PAH photodegradation depends on exposure time, molecular weight and soil texture.  Semiconductor minerals in fine-textured regosol soil enhance PAH photodegradation.  Microtox ® shows a higher detoxification over time in fine-textured soil.  d 2 H confirmed benzo(a)pyrene degradation, highlighting the potential of CSIA. article info Article history: Received 9 May 2015 Received in revised form 16 November 2015 Accepted 18 January 2016 Available online 4 February 2016 Handling Editor: Frederic Leusch Keywords: Polycyclic aromatic hydrocarbons (PAHs) Photodegradation Soil Ecotoxicity Hydrogen isotopes abstract The photodegradation of polycyclic aromatic hydrocarbons (PAHs) in two typical Mediterranean soils, either coarse- or fine-textured, was here investigated. Soil samples, spiked with the 16 US EPA priority PAHs, were incubated in a climate chamber at stable conditions of temperature (20  C) and light (9.6 W m 2 ) for 28 days, simulating a climate change base scenario. PAH concentrations in soils were analyzed throughout the experiment, and correlated with data obtained by means of Microtox ® eco- toxicity test. Photodegradation was found to be dependent on exposure time, molecular weight of each hydrocarbon, and soil texture. Fine-textured soil was able to enhance sorption, being PAHs more pho- todegraded than in coarse-textured soil. According to the EC 50 values reported by Microtox ® , a higher detoxification was observed in fine-textured soil, being correlated with the outcomes of the analytical study. Significant photodegradation rates were detected for a number of PAHs, namely phenanthrene, anthracene, benzo(a)pyrene, and indeno(123-cd)pyrene. Benzo(a)pyrene, commonly used as an indicator for PAH pollution, was completely removed after 7 days of light exposure. In addition to the PAH chemical analysis and the ecotoxicity tests, a hydrogen isotope analysis of benzo(a)pyrene was also carried out. The degradation of this specific compound was associated to a high enrichment in 2 H, obtaining a maximum d 2 H isotopic shift of þ232‰. This strong isotopic effect observed in benzo(a) pyrene suggests that compound-specific isotope analysis (CSIA) may be a powerful tool to monitor in situ degradation of PAHs. Moreover, hydrogen isotopes of benzo(a)pyrene evidenced a degradation process of unknown origin occurring in the darkness. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Polycyclic aromatic hydrocarbons (PAHs) are a large group of semi-volatile organic compounds composed of two or more fused aromatic rings. Although these chemicals are mostly released to air, soil is considered as one of the major sinks of atmospheric PAHs * Corresponding author. E-mail address: marti.nadal@urv.cat (M. Nadal). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere http://dx.doi.org/10.1016/j.chemosphere.2016.01.069 0045-6535/© 2016 Elsevier Ltd. All rights reserved. Chemosphere 148 (2016) 495e503