Augustine et al. 2020 - Lafia irrigated farmland soil

Augustine and colleagues measured lead and cobalt in surface soils from an irrigated vegetable farmland near the Amba River in Lafia, Nigeria. The source is not utensils or finished-product occurrence evidence: it is upstream irrigation/farmland pathway evidence for metals in soil where vegetables are grown.

Key numbers

The sampling site was a vegetable irrigated farmland in Tundun Amba, close to the State Water Board intake in Lafia metropolis and near the Amba River. Three representative soil samples were collected at 0-15 m, 15-30 m, and 30-45 m from the irrigation-water source, using surface soil from 0-30 cm depth.

Soil physicochemical parameters in Table 2 were: pH-H2O 6.35, 5.81, and 5.60 for samples A, B, and C; pH-CaCl2 5.23, 5.35, and 4.78; electrical conductivity 100, 240, and 210 µS/cm; exchangeable acidity 0.83, 1.0, and 0.50 Meq/100g; organic carbon 1.40%, 1.49%, and 1.45%; organic matter 2.40%, 2.57%, and 2.50%; and texture classes sandy loam, sandy loam, and loamy sand.

Table 3 reports heavy-metal concentrations using aqua regia digestion, in mg/kg:

Table 4 reports heavy-metal concentrations using nitric acid digestion, in mg/kg:

The results text summarizes aqua-regia-extractable Co as 0.083-0.105 mg/kg and Pb as 1.473-1.573 mg/kg, and nitric-acid-extractable Co as 0.060-0.086 mg/kg and Pb as 1.363-1.512 mg/kg. Pb ranked higher than Co under both digestion methods.

The authors attribute the higher Pb signal to activities carried out on the Amba River, including automobile washing, discharge into the water body from the Lafia water-works treatment plant, and other anthropogenic activities. The conclusion states that all measured Pb and Co concentrations were below the cited DPR-EGASPIN and US EPA farmland-soil limits.

Methods (brief)

Surface soils were air-dried for one week, pulverized, sieved through 2.0 mm mesh for pH and total-metal analysis, and further pulverized through 0.5 mm mesh for organic matter. Pb and Co were extracted in parallel by aqua regia digestion (30.0 mL HCl plus 10.0 mL HNO3 added to 1.0 g soil and left 24 h, then heated at 140 C) and nitric acid digestion (1.0 g soil with HNO3, heated to a clear solution). Concentrations were determined by atomic absorption spectrometry from calibration curves.

Implications

Certification: Do not use these values as vegetable, utensil, or finished-product occurrence data. They are site-specific farmland-soil measurements that document an upstream irrigation-water/river pathway into agricultural soil.

Courses: Useful for explaining why irrigation-source activities and water-body contamination can become soil exposure context before any edible crop measurement is available.

App: Context only. The page can support pathway and source-attribution narrative for irrigated vegetable farming near mixed anthropogenic river inputs, but it does not estimate crop concentrations or consumer exposure.

Wiki pages this source may touch

• irrigation-and-soil-amendments
• soil-to-plant-transfer
• source-attribution-environmental-burden-apportionment
• lead
• cobalt

Verification notes

Recovered from skip:not-food-occurrence under the 2026-06-10 inclusion-by-default rule. The old skip treated the paper as out of scope because it lacked finished-food or utensil occurrence values. On reading, it is in-scope a3 pathway evidence because it measures Pb and Co in irrigated vegetable-farmland soil and links the soil context to Amba River irrigation inputs.

Numbers were checked against the extracted PDF text, especially the abstract, sampling section, Table 1, Table 2, Table 3, Table 4, the heavy-metals discussion, and the conclusion. Units and digestion methods are preserved as printed. The page does not infer crop concentrations from soil values, and no brand or product route is created.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.