Overview
Desalew and Mehari quantified ten elements (Ca, Mg, Fe, Zn, Mn, Cu, nickel (Ni), chromium (Cr), cadmium (Cd), Pb) in rice grains collected from the three major production regions of Ethiopia (Fogera, Metema, Pawe) and their corresponding field soils, using flame atomic absorption spectroscopy (FAAS). The rice-results section reports chromium, nickel and cadmium as detected below the method’s quantification limit and lead as not detected. These method-limited findings do not establish absence of contamination or a numeric upper bound without the applicable reporting limits.
Key numbers
- Sampling unit: 9 area composites (3 per region), each combining three farmer samples of 0.5 kg; 27 farmer contributions are not 27 independent composites
- Method: FAAS with HNO3/HClO4/H2O2 acid digestion; accuracy 87–113% recovery
- Cd: detected below LOQ; no numerical limit inferred here
- lead (Pb): not detected in the rice-results section
- Cr: detected below LOQ
- Ni: detected below LOQ
- Most abundant element in rice: Mg (414–561 mg/kg dw), followed by Fe (49.4–168 mg/kg dw)
- Fe in rice differed significantly by region: Fogera contained more than double the Fe of the other regions
- Cu in rice from Pawe was less than half that from other regions
- Soil concentrations for all elements were higher than in grain, indicating absence of bioaccumulation
- Only Cu showed a strong positive correlation between soil and grain (r = 0.991); other elements did not correlate significantly
Methods (brief)
FAAS on acid-digested samples. Digestion optimized for reagent volumes (HNO3, HClO4, H2O2), temperature, and time. Three sampling areas per region; composite samples from three different farmers per area. Accuracy validation by certified reference material comparison (87–113%). Loq threshold not explicitly stated for toxic metals; Cd, Pb, and Cr reported as “below the limit of quantitation of the method.”
Implications
Occurrence: The sampled farmland composites extend the geographic coverage of rice evidence. Non-quantification cannot establish compliance with a numerical limit unless the analytical reporting limit and applicable scope are known.
Courses: Illustrates geographic variability in rice elemental profiles; contrast with known high-arsenic Asian rice geographies.
Interpretation: Preserve detected-below-LOQ and not-detected results separately. Neither is a measured zero or a population-wide finding for this origin.
Related evidence
Update history
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