Arsenic accumulation by edible aquatic macrophytes K.A. Falinski a,n , R.S. Yost a , E. Sampaga b,1 , J. Peard c a Department of Tropical Plant and Soil Sciences, University of Hawaii at Manoa, 3190 Maile Way, Honolulu, HI 96822, United States b Hilo High School, Hilo, HI 96811, United States c Hazard and Emergency Environmental Response Office, Hawaii Department of Health, Hilo, HI, United States article info Article history: Received 13 June 2013 Received in revised form 26 September 2013 Accepted 2 October 2013 Available online 5 November 2013 Keywords: Arsenic Aquatic macrophytes Plant uptake Soil contamination abstract Edible aquatic macrophytes grown in arsenic (As)-contaminated soil and sediment were investigated to determine the extent of As accumulation and potential risk to humans when consumed. Nasturtium officinale (watercress) and Diplazium esculentum (warabi) are two aquatic macrophytes grown and consumed in Hawaii. Neither has been assessed for potential to accumulate As when grown in As-contaminated soil. Some former sugarcane plantation soils in eastern Hawaii have been shown to have concentrations of total As over 500 mg kg 1 . It was hypothesized that both species will accumulate more As in contaminated soils than in non-contaminated soils. N. officinale and D. esculentum were collected in areas with and without As-contaminated soil and sediment. High soil As concentrations averaged 356 mg kg 1 , while low soil As concentrations were 0.75 mg kg 1 . Average N. officinale and D. esculentum total As concentrations were 0.572 mg kg 1 and 0.075 mg kg 1 , respectively, corresponding to hazard indices of 0.12 and 0.03 for adults. Unlike previous studies where watercress was grown in As-contaminated water, N. officinale did not show properties of a hyperaccumulator, yet plant concentrations in high As areas were more than double those in low As areas. There was a slight correlation between high total As in sediment and soil and total As concentrations in watercress leaves and stems, resulting in a plant uptake factor of 0.010, an order of magnitude higher than previous studies. D. esculentum did not show signs of accumulating As in the edible fiddleheads. Hawaii is unique in having volcanic ash soils with extremely high sorption characteristics of As and P that limit release into groundwater. This study presents a case where soils and sediments were significantly enriched in total As concentration, but the water As concentration was below detection limits. & 2013 Elsevier Inc. All rights reserved. 1. Introduction The accumulation of arsenic (As) from contaminated soils, sediments and water into edible plants presents a possible route for exposure to humans. Arsenic is a well-known human carcino- gen affecting numerous organs, and As toxicity is associated with multisystem disease (Ratnaike, 2003). Exposure is usually from absorption through the small intestine, through ingestion of As in water, food or contaminated soil particles. Potential human health risks due to ingestion of plants containing As have recently received attention, especially for rice (Zhao et al., 2010). Additional studies documenting As uptake in vegetables, including vegetables irrigated with contaminated well water (Baig and Kazi, 2012) or grown on contaminated soil (McBride et al., 2013), and taro grown in contaminated soil and water (Kurosawa et al., 2008), further outline the possible risk of As through plant consumption. The accumulation of As is also important in wetland species, where there is a potential for reducing conditions to release As into the soil solution (Ha et al., 2009; Rahman and Hasegawa, 2011), or for co-deposition of As with Fe hydroxides adsorbed to the plant's surface (Zhao et al., 2002). A wide range of aquatic macrophytes have commonly been used for their role in phytoremediation of organic and inorganic pollutants, including As, because of their capacity to accumulate metals in their tissues (Dhir et al., 2009; Rahman and Hasegawa, 2011). There is a potential risk to human health due to consumption of contaminants accumulated by edible aquatic macrophytes, such as watercress and edible ferns. Robinson et al. (1995) found As levels of up to 500 mg kg 1 dry weight (DW) in the leaves of Cerato- phyllum demersum (commonly called watercress), an aquatic, flowering plant found in a river system in New Zealand. Research- ers were unable to conclude, however, whether the uptake was due to elevated concentrations of As in dissolved form in river water or in the sediments in which the watercress was grown. In a greenhouse experiment, they reported that watercress preferen- tially stores As in its leaves rather than in the stems (Robinson et al., 2003). Two reports have considered using the commonly Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/ecoenv Ecotoxicology and Environmental Safety 0147-6513/$ - see front matter & 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ecoenv.2013.10.008 n Corresponding author. E-mail addresses: kimfalinski@gmail.com, falinski@hawaii.edu (K.A. Falinski). 1 Currently at: University of Washington, Department of Earth and Space Sciences, Seattle, WA 98195, United States. Ecotoxicology and Environmental Safety 99 (2014) 74–81