The accumulation of La, Ce and Y by Lemna minor and Lemna gibba in the Keban gallery water, Elazig Turkey Merve Sasmaz 1 , Erdal Obek 2 & Ahmet Sasmaz 3 1 Department of Civil and Structural Engineering, The University of Sheffield, Sheffield S1 3JD, UK; 2 Department of Bioengineering, Firat University, Elazı g 23119, Turkey; and 3 Department of Geological Engineering, Firat University, Elazı g 23119, Turkey Keywords accumulation; aquatic plants; cerium; gallery water; lanthanum; yttrium. Correspondence A. Sasmaz, Department of Geological Engineering, Firat University, Elazı g 23119, Turkey. Email: asasmaz@gmail.com doi:10.1111/wej.12301 Abstract This study investigated the phytoremediation ability of Lemna minor and Lemna gibba to accumulate lanthanum, cerium and yttrium from gallery water polluted by metals. L. minor and L. gibba were settled in the mining water and adapted to separate reac- tors. During the experiment, the water and plant samples were daily taken and the temperature, electric conductivity and pH of the water were daily measured in situ. These plants were firstly washed, dried in and then ashed at 3008C for 24 h in an oven. Both water and ashed plant samples were measured by ICP-MS to detect the concen- trations of lanthanum (La), cerium (Ce) and yttrium (Y). Although these elements are at low concentrations in gallery water, they were accumulated at the highest levels in L. gibba and in L. minor. This study showed that both plants have high ability to remove lanthanum, cerium and yttrium in gallery water polluted by different elements. Introduction Lanthanum (La) and cerium (Ce) are members of the rare earth elements (REEs) from lanthanum to lutetium including yttrium (Y) and scandium (Sc). Their average abundances in continental crust are 30 p.p.m. for La, 60 p.p.m. for Ce and 24 p.p.m. for Y (Wedepohl 1995). The REEs occurred usually together with fluorides, silicates, carbonates and phos- phates and especially in granites and pegmatites. They rarely form mineral deposits and enrich in some phosphate minerals such as apatite and monazite. Yttrium is often replaced by lanthanides in xenotime (Alex et al. 1998; Masau et al. 2000). They have similar physicochemical properties with La and Ce. In recent years, more REE concentrations have been emitted to the water and soil environment due to medical and high-tech applications and the common use of fertilizers in forestry and agriculture (Oral et al. 2010). Actual studies have focused on biogeochemical behaviours, bioa- vailability and the environmental effects of lanthanum, cerium and yttrium in water -sediment––biota (Weltje et al. 2002). REEs have limited toxicity to the environment. But, Thomas et al. (2014) suggested that REE’s low concentra- tions could be problematic for clean environment. Toxico- logical studies showed that REE accumulations might be negative effects on aquatic biota (Oral et al. 2010). All REEs are known to be toxic for cell metabolism; however, there are no more available data about their restrictive effects on plants (Kabata-Pendias 2011). Surface and underground waters normally contain very low concentration of REEs (Sultan & Shazili 2009). High concentrations of REEs go into the water bodies in two sources such as the industrial waste- water and the leaching process in soils polluted with REEs. As a result, REE levels were significantly increased in clean waters. Aquatic plants occur in habitats like river and lakes and were often used in assessment and monitoring of water quality (Ratushnyak & Trushin 2007). Lemna gibba and Lemna minor among the aquatic macrophytes have a high growth ratio on the water (Dirilgen 2011) and they directly take metals from water and put away them in their bodies. Lemna gibba and Lemna minor have also high ability to accu- mulate toxic elements and pollutants from aquatic environ- ments. Therefore, they have been often used as model plants for ecotoxicological and phytoremediation studies (Obek 2009; Chandra & Yadav 2011; Sasmaz & Obek 2009, 2012; Sood et al. 2012; Chaudhuri et al. 2014; Goswami et al. 2014; Tatar & Obek 2014; Sasmaz et al. 2015). In this way, toxic metals cause adverse impacts by releasing into the environment. Therefore, most of studies in recent years have focused on the effects of toxic metals in mining areas (Teng et al. 2004; Natarajan et al. 2006), whereas a small number of researches have concentrated on the behaviour of REE (Wang et al. 2007; Xu et al. 2008, 2012; Ippolito et al. 2010). Hirano and Suzuki (1996) have detected the harmful effects of REEs to human in long-term exposure. This study was designed firstly to determine lanthanum, cerium and 75 Water and Environment Journal 32 (2018) 75–83 V C 2017 CIWEM. Water and Environment Journal. Print ISSN 1747-6585