Contents lists available at ScienceDirect Ecological Engineering journal homepage: www.elsevier.com/locate/ecoleng Biofilters for urban agriculture: Metal uptake of vegetables irrigated with stormwater K.T. Ng a , P. Herrero b , B. Hatt a , M. Farrelly c , D. McCarthy a, ⁎ a Environmental and Public Health Microbiology Laboratory (EPHM Lab), Department of Civil Engineering, Monash University, Clayton, VIC 3800, Australia b Department of Civil Engineering and Urbanism, INSA Lyon, 20 Avenue Albert Einstein, 69621 Villeurbanne Cedex, France c Monash Water for Liveability, Department of Social Sciences, Monash University, Clayton, VIC 3800, Australia ARTICLE INFO Keywords: Stormwater management Metal accumulation Heavy metals Bioretention ABSTRACT In an era where increasing urbanization is resulting in issues such as urban poverty, malnutrition and un- employment, urban agriculture is increasingly regarded as a multi-functional approach to addressing these is- sues. However, increasing water scarcity limits the feasibility of urban agriculture and hence alternative water sources for irrigation are required. While stormwater has the potential to be used for urban agricultural irri- gation, stormwater contaminants can pose potential health risks. Thus, a column study was conducted to (1) determine whether biofilters planted with vegetable crops are capable of treating urban stormwater, and (2) identify the level of heavy metal uptake into various vegetable crops when irrigated with stormwater. The column study was conducted over nine weeks with nine vegetable species (broad beans (Vicia faba), kohlrabi (Brassica oleracea Gongylodes Group), kale (Brassica oleracea Acephala Group), lettuce (Lactuca sativa), mint (Mentha spicata), mustard spinach (Brassica juncea), radish (Raphanus sativus), spinach (Spinacia oleracea) and sweet corn (Zea mays)) irrigated with stormwater. The treatment function of the system was not compromised by the use of vegetable crops. 70% concentration reduction was achieved for Cu, Pb, Zn, Mn and Ni. The con- centration of total nitrogen and total phosphorus in the effluent was reduce by up to 47% and 69%, respectively. Heavy metal accumulation was limited in the edible portions but the levels of Cd and Pb concentration exceeded the Food Standards for Australia and New Zealand and World Health Organization guideline values, deeming it unsafe for consumption. Cultivating vegetable crops in biofilters did not affect plant growth and the biofilter’s stormwater treatment functions. However, heavy metal concentrations within plants does raise potential health concerns, requiring further studies to improve crop safety. 1. Introduction Urban agriculture is a practice located within urban areas and in- volves various crops as well as the rearing of livestock (FAO, 2008). It often uses water, land and waste materials obtained from urban areas as inputs (FAO, 2008). Urban agriculture has been practiced for many centuries, with roots in the development of ancient civilisations and is currently being revived in many parts of the world in an attempt to provide direct access to food, employment opportunities, community engagement and healthier food options (Moglia, 2014). The practice of urban agriculture is constrained by increasing water scarcity which is further compounded by increasing water demands from rapid urbani- zation and population growth (Moglia, 2014). To reduce the pressures on potable water supplies whilst also meeting the irrigation require- ments for urban agriculture, alternative water sources such as wastewater, greywater and stormwater are increasingly being ad- vocated and utilised (Finley et al., 2009, Nnadi et al., 2015, van Lier and Huibers, 2010). However, such water sources contain pollutants such as heavy metals, organic micropollutants and pathogens which render them unsuitable for irrigation without pre-treatment (van Lier and Huibers, 2010, Tom et al., 2013). The effects of improper use of recycled water on the contamination of crops by heavy metals have been demonstrated and the potential health risks of overconsumption of such metals have also been high- lighted (Tom et al., 2014). Studies on metal accumulation in the edible portions of vegetables found that metal concentrations often exceeded guideline limits (Muchuweti et al., 2006, Tom et al., 2014). For ex- ample, one laboratory-scale study on vegetable metal accumulation in a system irrigated with stormwater found that Pb concentrations in plants exceeded the guideline limits set by the Food Standards for Australia https://doi.org/10.1016/j.ecoleng.2018.07.033 Received 27 April 2018; Received in revised form 23 July 2018; Accepted 29 July 2018 ⁎ Corresponding author. E-mail address: david.mccarthy@monash.edu (D. McCarthy). Ecological Engineering 122 (2018) 177–186 0925-8574/ © 2018 Elsevier B.V. All rights reserved. T