Distribution of metals in four spontaneous plants and soils from swales and detention basins along roadways in the Edwards Aquifer recharge zone, Central Texas

Spontaneous vegetation in swales and detention ponds represent novel ecosystems. This study evaluated metals in soils and spontaneous plants from swales (n = 3) and detention basins (n = 3) in Central Texas. Four native roadside plants (Phyla nodiflora, Ratibida columnifera, Ruellia nudiflora, and Tridens albescens) were found to be accumulators of metals. Plant uptake of metals from highest to lowest concentrations was zinc (Zn) > lead (Pb) > copper (Cu) > nickel (Ni) > chromium (Cr) > cadmium (Cd). Zn ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mover><mml:mi>x</mml:mi> <mml:mo>¯</mml:mo></mml:mover> <mml:annotation>$\bar{x}$</mml:annotation></mml:semantics> </mml:math> = 75.4) and Pb ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mover><mml:mi>x</mml:mi> <mml:mo>¯</mml:mo></mml:mover> <mml:annotation>$\bar{x}$</mml:annotation></mml:semantics> </mml:math> = 34.9) concentrations (mg kg^-1) in shoots were highest in P. nodiflora. In roots, Zn ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mover><mml:mi>x</mml:mi> <mml:mo>¯</mml:mo></mml:mover> <mml:annotation>$\bar{x}$</mml:annotation></mml:semantics> </mml:math> = 78.8) concentrations was highest in T. albescens ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mover><mml:mi>x</mml:mi> <mml:mo>¯</mml:mo></mml:mover> <mml:annotation>$\bar{x}$</mml:annotation></mml:semantics> </mml:math> = 78.8), while Pb ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mover><mml:mi>x</mml:mi> <mml:mo>¯</mml:mo></mml:mover> <mml:annotation>$\bar{x}$</mml:annotation></mml:semantics> </mml:math> = 31.1) concentrations were highest in P. nodiflora. Plant parts contained greater concentrations of metals than soils. Metals in soils from highest to lowest concentrations (mg kg^-1) were Zn > Pb > Cu > Cr) > Ni, with no Cd being detected in soils. Concentrations of Zn (23.9-252.1 mg kg^-1) and Pb (8.5-22.6 mg kg^-1) were most common in the soil profile from 0 to 30 cm, while the concentrations of Ni (0.0 mg kg^-1), Cr (0.0-1.9 mg kg^-1), and Cu (0.0-8.6 mg kg^-1) were low and primarily limited to the upper 0-10 cm of the soil. The results of this study indicate that spontaneous native plants found in stormwater retention areas are capable of taking in a variety of metals and can be accumulators of metals.