Effects of waterlogging on pollutant availability in iron mining tailings and the tolerance response of Typha domingensis Pers

Abstract

Soil flooding can increase nutrient and pollutant availability to plants; however, the effects in iron mining tailings are still unclear. This work hypothesizes that waterlogging increases the availability of elements present in iron mining tailings, but tolerant aquatic plants can survive under these conditions, showing potential for phytoremediation. This work investigated how flooding affects the availability of essential elements and metal pollutants in iron mining tailings and how this affects the growth, root anatomy, and pollutant content in the aquatic plant Typha domingensis (cattail). Cattail clones were grown in pots containing iron mining tailings under two irrigation conditions: field capacity and waterlogged. The experimental design was completely randomized with 18 replicates and two treatments ( n = 36), and the experiment was conducted for 180 days. The pH, electrical conductivity, and total dissolved solids were measured from the iron mining tailings and the plant contents of Al, Cd, Cr, Pb, Fe, and Ca, as well as their growth and root anatomy were evaluated. Waterlogging increased the pH (from 6 to 7), total dissolved solids (from 61.9 to 140.8 ppm), and the electrical conductivity (from 113.2 to 282.1 µs cm −1 ) of iron mining tailings, suggesting higher ion availability in the water. Waterlogging of iron mining tailings also increased the elemental uptake, ranging from 50 to 178% depending on the element considered. No growth limitation was observed since waterlogging also increased the root dry and fresh masses, the root:shoot ratio, the root biomass allocation, and plant dry mass from cattail. Waterlogging of iron mining tailings also increased the root cortex area, the exodermis thickness, and the vascular cylinder area. Results suggest that waterlogging of iron mining tailings increases the availability and uptake of elements by T. domingensis , which, nevertheless, suffers no significant growth limitations and shows relevant potential for the remediation of iron mining tailings when the pollutant is present in natural wetlands and when the species is used in remediation systems.

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