Urban runoff has become an emergent ecotoxicity risk for the environment and recognized as a substantial source of pollutants to receiving waters (Davis et al. 2001; Müller et al. 2020). Runoff contains various substances, including heavy metals (HMs) like nickel (Ni), lead (Pb), chromium (Cr), cadmium (Cd), copper (Cu), zinc (Zn), mercury (Hg) and others (Reddy et al. 2014). Heavy metals (HMs) or "trace metals" are defined as a group of elements that are associated with environmental pollution (Prasad 2004). Although, some of the mentioned HMs like Zn represent the so-called micronutrients, which contribute to several cellular and physiological activities of plants and promote plant growth and development. Their presence in water in concentrations higher than necessary can have a toxic effect on flora, fauna, and humans (Hamzah et al. 2022). Sources of Zn in stormwater runoff are mostly derived from human activities, roads related to traffic, fluid leaks, brake and tire wear, paints, coatings, galvanized materials, etc. spills and leachates, various surface deposits and atmospheric deposits (Davis 2007; Müller et al. 2020). Exposure and risk of Zn toxicity on surface waters have been widely conducted, within a number of investigators that have found significant levels of Zn in runoff, in both residential and industrial areas (Davis et al. 2001; Mosley and Peake 2001; Joshi and Balasubramanian 2010; Li and Zuo 2013; Shajib et al. 2019). With increasing emissions, Zn might pose great ecological risk to aquatic organisms, which are sensitive to this metal, especially by the fact that the global production of Zn in aquatic environments is ranked in the top three compared to other metals (Fu et al. 2016).
Mentioned concerns over water contamination have prompted environmental monitoring and sustainable environmental management technologies. Phytoremediation is a cost effective, noninvasive, and publicly acceptable method of removing environmental contaminants than most chemical and physical methods, since it uses vegetation to remediate contaminants from water, soil and sediments (Ruby and Appleton 2010; Yan et al. 2020). Five types of phytoremediation technologies have often been employed for decontamination: phytostabilization, phytodegradation, rhizofiltration, phytoextraction and phytovolatilization (Nedjimi, 2021). The use of metal-accumulating plants to clean soil and water contaminated with toxic metals is the most rapidly developing component of this environmentally friendly and cost-effective technology (Raskin et al. 1997). Along with constructed wetlands (CWs), bioretention systems (BRs) are known as one of the low cost alternatives to conventional cleanup techniques, positively improving remediation of contaminants, storing runoff water, reducing peak-flow, nutrient cycling, sequestering HMs and also providing supplementary benefits such as recreational facilities (Malaviya et al. 2019; Morash et al. 2019). Their performance and high effectiveness in removing pollutants found in urban runoff has been confirmed both by laboratory and field research (Davis et al. 2003; Hunt et al. 2006; Davis 2007; David et al. 2014) suggesting that BRs are effective for urban water quality improvement.
In BRs, plants are exposed to high levels of diverse pollutants. The selection of vegetation for phytoremediation of urban runoff with BRs is, therefore, primarily based on their ability to survive in potentially stressful growing conditions and their ability to absorb nutrients (nitrogen, phosphorus, etc.), HMs (Pb, Zn, Cu) and other pollutants (Hunt et al. 2015; Dagenais et al. 2018). A range of plant species has been investigated for phytoremediation, both soil and water (Zhang et al. 2012; Figueira et al. 2012; Ladislas et al. 2013; Pérez-Sirvent et al. 2017). For example, Typha angustifolia, Colocasia esculenta and Cyperus malaccensis, are known as plants for phytoremediation of Cd and Zn. All three species under hydroponic conditions for 15 days showed 100% of survival (Chayapan et al. 2015). Phragmites australis and Typha latifolia grown in the CWs that used to treat highway runoff in Ireland have accumulated a considerable amount of different HMs in sediment and plants, associated with road runoff, whereas, the highest removal efficiencies in the CW were for 86% for Zn (Gill et al. 2017). Species Phragmites australis, Iris pseudacorus, Canna indica, Alissma plantago, Menianthes trifoliata and Iris sibirica showed a potential for accumulation of Cr and Ni in their below-ground parts grown in floating treatment wetlands (Čule et al. 2021).The results clearly indicated that Canna indica, Pontederia cordata and Thalia dealbata are among species that were the most suitable species for CWs (Barco and Borin 2020). In a study with an artificial pond constructed with two topsoils collected from the Portman Bay (SE Spain), species Juncus effusus L. and Iris pseudacorus L. were highly recommended for remediation purposes.
Hydroponic experiments are one of the desirable alternative methods for examining the tolerance characteristics of plants to HMs on short timescales, providing HMs accumulation in plant species with greater precision than soil studies (Chayapan et al. 2015; Liu et al. 2018). In this study, we investigated the accumulation of Zn in two different plant species, namely Juncus effusus L. and Iris pseudacorus L. Plants were grown hydroponically in jars with Hoagland nutrient and different Zn concentrations, in order to provide a contribution in determining plants suitable for phytoremediation of urban runoff. In this study, Zn was selected for phytoremediation, based on previous research on the quality of the runoff samples at the analyzed locations in the city of Novi Sad, Serbia, which were singled out as locations with the problem of urban flooding (Greksa et al. 2019). The results of this analysis demonstrated the presence of high Zn concentrations in urban runoff, which can be identified as potential threats to natural aquatic ecosystems. The aim of this work is therefore, to recommend plants as a part of BRs for phytoremediation of urban runoff as well as provide information of plant species which might be useful for phytoremediation of polluted waters in general.