Temporal variability in trace metal solubility in a paddy soil not reflected in uptake by rice (Oryza sativa L.)

Abstract

Alternating flooding and drainage conditions have a strong influence on redox chemistry and the solubility of trace metals in paddy soils. However, current knowledge of how the effects of water management on trace metal solubility are linked to trace metal uptake by rice plants over time is still limited. Here, a field-contaminated paddy soil was subjected to two flooding and drainage cycles in a pot experiment with two rice plant cultivars, exhibiting either high or low Cd accumulation characteristics. Flooding led to a strong vertical gradient in the redox potential (Eh). The pH and Mn, Fe, and dissolved organic carbon concentrations increased with decreasing Eh and vice versa. During flooding, trace metal solubility decreased markedly, probably due to sulfide mineral precipitation. Despite its low solubility, the Cd content in rice grains exceeded the food quality standards for both cultivars. Trace metal contents in different rice plant tissues (roots, stem, and leaves) increased at a constant rate during the first flooding and drainage cycle but decreased after reaching a maximum during the second cycle. As such, the high temporal variability in trace metal solubility was not reflected in trace metal uptake by rice plants over time. This might be due to the presence of aerobic conditions and a consequent higher trace metal solubility near the root surface, even during flooding. Trace metal solubility in the rhizosphere should be considered when linking water management to trace metal uptake by rice over time.

Overexpression of a High-Affinity Nitrate Transporter OsNRT2.1 Increases Yield and Manganese Accumulation in Rice Under Alternating Wet and Dry Condition

“…In this study, we performed hydroponic experiments in MES buffered nutrient medium (to control pH) and nutrient treatments were replaced every 2 days. Furthermore, the Mn content in grain from field experiments should not be influenced by pH as the rhizosphere ranges from pH 5.5 to 6.0 in paddy soil ( Pan et al, 2016 ). Thus, any effects of soil alkalization were excluded.…”

Derivation of regional risk screening values and intervention values for cadmium‐contaminated agricultural land in the Guizhou Plateau

“…Derivation of local soil criteria requires predictive models that take account of Cd (bio)availability. There are many factors that affect Cd (bio)availability in soils and the uptake by plants including soil texture, mineralogy, soil physiochemical properties such as pH and organic matter (OM) content, and crop species (Efroymson, Sample, & Suter, ; Hooda, McNulty, Alloway, & Aitken, ; McBride, ; Pan et al, ). Of these influencing factors, soil pH is the most important as validated by previous studies (Adams, Zhao, McGrath, Nicholson, & Chambers, ; McBride, ).…”

Reducing cadmium bioaccumulation in Theobroma cacao using biochar: basis for scaling-up to field

“…Cadmium pools in soils were determined at 130 days using three single-step extraction methods as shown in Table 2 . Water-soluble and easily exchangeable Cd (CaCl 2 -Cd) and exchangeable Cd (NH 4 OAc-Cd) represent the directly bioavailable and reactive pools of Cd in the soil, respectively, while HCl-Cd represents the least available pool ( Pan et al., 2016 ). Quinoa-BC at 2% significantly decreased soluble and exchangeable Cd pools in soils by ∼71% ( Table 2 ).…”