2.1 Study site and sampling
This
study was conducted in
Hoxud
County in the Xinjiang Uyghur Autonomous Region of China (91°45′42″E,
40°39′75″N). This region experiences a semi-arid climate with a mean
annual temperature of 12.56 °C and a mean annual precipitation of 591
mm. The sampling sites are located in the watershed area of seasonal
floods from radiation-contaminated region with 137Cs
accumulation. The soil had a salt content above 2% in the surface layer
(< 20 cm deep) and a radionuclide level 3-5 fold that of
normal soil. K. schrenkianum was the dominant population of the
local habitat. Plant materials and soil samples were collected from four
sites with different environmental radioactivity levels during August
and September 2017 (Table S1). Five plants (15 m apart) were uprooted
from each site. Whole plants were placed in large autoclaved paper
envelopes, labelled, transported to laboratory in an icebox, and stored
at -80 °C until further process. Five soil samples were collected with
shovels from the surface soil (0-20 cm deep) of each site. Soil samples
from each site were sieved to remove rocks and plant litter, pooled,
packed and labelled in cloth bags, and stored at 4 °C to transport to
the laboratory. The
geochemical
characteristics, such as pH, electrical conductivity (EC), organic
matter (OM), total
nitrogen
(TN), soluble nitrogen (SN), available phosphorus (P), available
potassium (K), salt (Sal), chloride ion (Cl), sulfate (Sulf), calcium
ion (Ca), magnesium ion (Mg), and sodium ion (Na), were measured in the
Institute of Quality Standards & Testing Technology for Agro-Products,
Xinjiang Academy of Agricultural Sciences.