Arsenic chemistry in the rhizosphere of Pteris vittata L. and Nephrolepis exaltata L.

Abstract

This greenhouse experiment evaluated the influence of arsenic uptake by arsenic hyperaccumulator Pteris vittata L. and non-arsenic hyperaccumulator Nephrolepis exaltata L. on arsenic chemistry in bulk and rhizosphere soil. The plants were grown for 8 weeks in a rhizopot with a soil containing 105 mg kg −1 arsenic. The soil arsenic was fractionated into five fractions with decreasing availability: non-specifically bound (N), specifically bound (S), amorphous hydrous-oxide bound (A), crystalline hydrous-oxide bound (C), and residual (R). P. vittata produced larger plant biomass (7.38 vs. 2.32 mg plant −1) and removed more arsenic (2.61 vs. 0.09 mg pot −1 arsenic) than N. exaltata. Plant growth reduced water-soluble arsenic, and increased soil pH ( P. vittata only) in the rhizosphere soil. P. vittata was more efficient than N. exaltata to access arsenic from all fractions (39–64% vs. 5–39% reduction). However, most of the arsenic taken up by both plants was from the A fraction (67–77%) in the rhizosphere soil, the most abundant (61.5%) instead of the most available (N fraction).