Localized
Flux Maxima of Arsenic, Lead, and Iron around
Root Apices in Flooded Lowland Rice
Paul N. Williams
Jakob Santner
Morten Larsen
Niklas
J. Lehto
Eva Oburger
Walter Wenzel
Ronnie N. Glud
William Davison
Hao Zhang
10.1021/es501127k.s001
https://acs.figshare.com/articles/journal_contribution/Localized_Flux_Maxima_of_Arsenic_Lead_and_Iron_around_Root_Apices_in_Flooded_Lowland_Rice/2039397
In
wetland-adapted plants, such as rice, it is typically root apexes,
sites of rapid entry for water/nutrients, where radial oxygen losses
(ROLs) are highest. Nutrient/toxic metal uptake therefore largely
occurs through oxidized zones and pH microgradients. However, the
processes controlling the acquisition of trace elements in rice have
been difficult to explore experimentally because of a lack of techniques
for simultaneously measuring labile trace elements and O<sub>2</sub>/pH. Here, we use new diffusive gradients in thin films (DGT)/planar
optode sandwich sensors deployed <i>in situ</i> on rice
roots to demonstrate a new geochemical niche of greatly enhanced As,
Pb, and Fe(II) mobilization into solution immediately adjacent to
the root tips characterized by O<sub>2</sub> enrichment and low pH.
Fe(II) mobilization was congruent to that of the peripheral edge of
the aerobic root zone, demonstrating that the Fe(II) mobilization
maximum only developed in a narrow O<sub>2</sub> range as the oxidation
front penetrates the reducing soil. The Fe flux to the DGT resin at
the root apexes was 3-fold higher than the anaerobic bulk soil and
27 times greater than the aerobic rooting zone. These results provide
new evidence for the importance of coupled diffusion and oxidation
of Fe in modulating trace metal solubilization, dispersion, and plant
uptake.
2015-12-17 04:16:23
root apexes
uptake
O 2 range
ROL
oxidation
O 2 enrichment
trace elements
pH
mobilization
Fe
DGT
Localized Flux Maxima
modulating trace metal solubilization