The effect of long-term wastewater irrigation on accumulation and transfer of heavy metals in Cupressus sempervirens leaves and adjacent soils Emad Farahat a,b, ⁎, Hans W. Linderholm b a Botany and Microbiology Department, Faculty of Science, Helwan University, Cairo, Egypt b Regional Climate Group, Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden HIGHLIGHTS • We studied the impacts of treated wastewater (TWW) on nutrients concentrations in green and senesced leaves of Cupressus sempervirens and soil in three de- sert plantations • The species accumulated high amounts of Zn, Mn, Cu and Cd in senesced leaves compared to green • Transfer factor of Zn and Cu from soil to trees was 2-15 times > that reported for forage crops • Stoichiometric ratios were decreased under TWW irrigation • A considerable amount of heavy metals return by senesced leaves to soil abstract article info Article history: Received 8 December 2014 Received in revised form 7 January 2015 Accepted 13 January 2015 Available online xxxx Editor: Charlotte Poschenrieder Keywords: Cupressus sempervirens Wastewater irrigation Senesced tissues Macro-nutrients Heavy metals Transfer and enrichment factor Wastewater reuse for agriculture is an important management strategy in areas with limited freshwater re- sources, yielding potential economic and environmental benefits. Here the effects of long-term irrigation with wastewater on the nutrient contents of green and senesced leaves of Cupressus sempervirens L. were assessed for three planted forests in Egypt. Stoichiometric ratios, transfer factors for nutrients from soil to plant and enrich- ment factors in contaminated soils were estimated and compared to a ground water irrigated control site. Under wastewater irrigation, C. sempervirens transferred most of the estimated nutrients, particularly heavy metals, from green to senesced leaves. This could be a self-protecting mechanism under continuous wastewater irriga- tion. The accumulation of four metals (Zn, Mn, Cu and Cd) with transfer factors N 1 for wastewater-irrigated trees, indicated the ability for metal accumulation of C. sempervirens. Stoichiometric ratios decreased under wastewater irrigation compared to the control site and global trends, which suggests nutrient disorders in these plants. The values of enrichment factors in the wastewater-irrigated soils showed remarkable availability and distribution of metals. Decreased resorption of metals by senesced leaves of C. sempervirens will add consid- erable amount of these metals to the soils, which will likely have adverse affects on the desert ecosystem components. © 2015 Elsevier B.V. All rights reserved. 1. Introduction In Mediterranean countries, natural water resources are limited, whereas their demand is constantly increasing. Thus, in this region, and other arid and semi-arid regions confronted with increasing water shortages, treated municipal wastewater is a valuable source for recycling and reuse of water, and commonly used in agriculture (Pedrero et al., 2012). Consequently, there is a considerable interest in the long-term effects of treated wastewater on the quality of crops intended for human consumption (Klay et al., 2010; Belaida et al., 2012; Pedrero et al., 2012). Wastewater can provide an important sup- plementary of some nutrients which have favorable effect on the growth of certain crops. However, it can also cause soil quality modifi- cation by structure deterioration and soil pollution by hazardous ele- ments such as metals (Bahri, 1995; Pedrero et al., 2010; Belaida et al., 2012). The rate of metal uptake by plants remains difficult to forecast, since it depends on a great number of factors, including metal specia- tion in soil and plant species (Belaida et al., 2012). Despite this being a problem that may have direct impacts on consumer's health and the Science of the Total Environment 512–513 (2015) 1–7 ⁎ Corresponding author at: Botany and Microbiology Department, Faculty of Science, Helwan University, Cairo, Egypt. E-mail addresses: Emad23_1999@yahoo.com (E. Farahat), Hansl@gvc.gu.se (H.W. Linderholm). http://dx.doi.org/10.1016/j.scitotenv.2015.01.032 0048-9697/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv