Using Plants to Immobilize and Stabilize Arsenic in the Soil

12/14/2017

Microscale X-ray fluorescence imaging of a 30 μm thick P. juliflora root thin section from a plant grown at the IKMHSS tailings amended with 15% compost and lime for one year

A microscale X-ray fluorescence image of a Prosopis juliflora root grown in arsenic-contaminated mine tailings shows detoxification of the soil by plant roots. [Image credit: Environ. Sci. Technol. 52, 1156−1164 (2018).]

Phytostabilization is a cost-effective long-term bioremediation technique for the immobilization of metalliferous mine tailings. However, the biogeochemical processes affecting metal(loid) molecular stabilization and mobility in the root zone remain poorly resolved.

In this study, the roots of Prosopis juliflora were grown for up to 36 months in compost-amended pyritic mine tailings from a federal Superfund site and then investigated by microscale and bulk synchrotron X-ray absorption spectroscopy and multiple energy micro-X-ray fluorescence imaging to determine iron, arsenic, and sulfur speciation, abundance, and spatial distribution.

Two distinct mechanisms of arsenic detoxification were identified: (1) As(V) bound to ferric sulfate plaques on root surfaces and (2) As(III) complexes in root vacuoles.

References

Hammond, C. M., et al. 2018. “Mechanisms of Arsenic Sequestration by Prosopis juliflora During the Phytostabilization of Metalliferous Mine Tailing,” Environmental Science & Technology 52, 1156−64. [DOI:10.1021/acs.est.7b04363]