Applied Soil Ecology 64 (2013) 77–83 Contents lists available at SciVerse ScienceDirect Applied Soil Ecology journal homepage: www.elsevier.com/locate/apsoil Effects of nonylphenols on soil microbial activity and water retention G. Ojeda a,∗ , J. Patrício a , H. Navajas b , L. Comellas b , J.M. Alca ˜ niz c,d , O. Ortiz c,d , E. Marks c , T. Natal-da-Luz a , J.P. Sousa a a IMAR – Institute of Marine Research, c/o Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, 3004-517 Coimbra, Portugal b IQS Technical College, Ramon Llull University, 08017 Barcelona, Spain c CREAF, Cerdanyola del Vallès 08193, Spain d Universitat Autònoma de Barcelona, Cerdanyola del Vallès 08193, Spain article info Article history: Received 30 March 2012 Received in revised form 24 October 2012 Accepted 26 October 2012 Keywords: Nonylphenol Peat Water retention Soil microbial activity abstract The main aim of this study is to analyze the influence of 4-nonylphenol (NP) on soil water retention and biological activity. Two doses of 4-nonylphenol (25 and 50 mg kg -1 ) were tested in a loam soil with and without peat amendment. In general, one week after the start of the experiment, the soil water content retained at -0.75 MPa of soil suction was 18% higher in the soil amended and its basal respiration (BR) was 15% higher than soil without peat. In contrast, the microbial activity indices (CM: coefficient of mineralization or BR:total organic carbon (TOC) ratio; Cmic:Corg: microbial biomass carbon (MBC):TOC ratio; qCO 2 : metabolic quotient or BR:MBC ratio) were higher in the soil without peat, compared to the soil amended with peat. On the other hand, the addition of NP to soil was able to modify soil biological but not physical (water retention, desorption) properties. When soil was amended with peat, MBC was reduced one week after applying NP. In contrast, no effects of NP on MBC were observed in the soil without peat. BR was reduced by 16% one week after applying 50 mg kg -1 of NP to soil with peat, and was increased by 46% one week after applying 25 mg kg -1 of NP to soil without peat. The effects of NP on MBC and BR could be associated more with the adsorption of NP by soil organic matter, while changes in CM or Cmic:Corg ratio were more closely related to changes in soil water retention. The potential toxic effects of NP (high qCO 2 values) were only observed in the absence of peat amendments. Peat addition reduced NP toxic effects on microorganisms. © 2012 Elsevier B.V. All rights reserved. 1. Introduction 4-Nonylphenol (NP) is the main degradation product of a group of non-ionic surfactants known as alkylphenol polyethoxylates, which have been a common component of domestic and indus- trial cleaning products (Roberts et al., 2006). The environmental occurrence of alkylphenols, such as NP, has been established since the late 1970s (Sheldon and Hites, 1978), with a worldwide pro- duction of about 500 Gg (Petrovic and Barceló, 2001). NP originates from the biodegradation of nonylphenol ethoxylates, which include other chemical forms of nonylphenol ethoxylates (nonylphe- nol, nonylphenol monoethoxylate, nonylphenol diethoxylate) and nonylphenol carboxy acids (4-nonylphenoxy acetic acid, nonylphe- noxy ethoxy acetic acid) (Domene et al., 2010). In general, NP could be adsorbed in soil particles by hydrophilic interaction with min- eral components and hydrophobic interaction with organic matter ∗ Corresponding author. Tel.: +351 239855760x415; fax: +351 239823603. E-mail address: g ojeda@student.zoo.uc.pt (G. Ojeda). in sediments, as observed by John et al. (2000) or by closely binding to humic acids in soils (Höllrigl-Rosta et al., 2003). Estrogenic, toxic and carcinogenic effects of NP in various teleost fish species, birds and mammals have been reported by several researchers over the last decade, at doses as low as 0.05–0.1 mg L -1 in water (Soares et al., 2008; Sayed et al., 2012). Thus, in order to fight NP pollution, the European Union (EU) has published Direc- tives aimed at environmental protection. The Water Framework Directive (European Commission, 2000) includes limitations for nonylphenol and today most of their uses are regulated (European Commission, 2003) due to the fact that they are considered to be priority hazardous substances (PHS) (Soares et al., 2008). Although critical levels of nonylphenol ethoxylates have been proposed or fixed for sewage sludge (50 mg kg -1 )(European Communities, 2000), freshwater (28 gL -1 ) or saltwater (28 gL -1 ) ecosystems (EPA, 2005), soil ecosystems are still not regulated in terms of NP concentration in soil. NP has been detected in rain and snow, prob- ably as a result of NP evaporation from water surfaces, soil bodies and vegetation (Friesa and Puttman, 2004; Nelson et al., 1998). Surface waters, sediments, groundwater, air and soil are the environmental compartments where NP is commonly found 0929-1393/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apsoil.2012.10.012