Chloride accumulation in aboveground biomass of three macrophytes (Phragmites australis, Juncus maritimus, and Typha latifolia) depending on their growth stages and salinity exposure: application for Cl removal and phytodesalinization.

Anthropogenic activities can be the source of saline solid wastes that need to be treated to reduce their salt load to meet the purposes of reuse, valorization or storage. In this context, chloride remediation can be achieved using high-salt accumulating plants. However, there is very limited information on the comparative potential of different species in the same environment, and only scarce data concerning their efficiency as a function of growth stage. In order to rationalize these selection criteria, three macrophytes i.e., common reed (Phragmites australis), sea rush (Juncus maritimus), and cattail (Typha latifolia), were cultivated at two growth stages (6-months old and 1-year old) for 65 days in Cl spiked substrates (from 0 up to 24 ‰ NaCl). The plants' survival and potential capacity for removal of Cl from substrates and accumulation in shoots were investigated. For the three studied species, mature and juvenile plants display a high tolerance to salinity. However, mature specimens with higher shoot biomass and Cl contents are capable of greater chloride removal than juvenile plants. The sole exception is P. australis which displays just the same phytoremediation potential for both mature and juvenile specimens. Moreover, P. australis has the lowest potential when compared with other species, being 1.5 and 3 times lower than for J. maritimus and T. latifolia. When considering the plant growth and the shoot biomass production, chloride removal rates from the substrate point that mature J. maritimus should preferentially be used to design an operational chloride remediation system. The results highlight the relevance of considering the growth stage of plants used for Cl removal. HIGHLIGHTS: 1) Mature and juvenile specimens of J. maritimus, P. australis, and T. latifolia have high salinity tolerance in solid media spiked up to 24 ‰ NaCl. 2) Mature plants have generally better Cl removal and phytoremediation performances than juvenile specimens. 3) J. maritimus is the most effective species for chloride phytoremediation with high survival and high Cl sequestration in shoots. 4) T. latifolia has high Cl removal in shoots and good remediation capacities but also shows sign of stress. 5) P. australis shows low Cl sequestration and is a poor candidate for chloride remediation from substrate.