Salawu et al. 2015 - metals in spinach and irrigation water in Zamfara

Salawu and coauthors analyzed Pb, Cd, Fe, Cu, and Zn in spinach and irrigation water from the Samaru Area of Gusau Metropolis, Nigeria. The source is routeable to spinach because it reports numeric concentrations for the edible matrix and its irrigation water. The study provides a paired water/vegetable context rather than a broad market sample.

Key numbers

All values are mean ± SD from triplicate AAS measurements (n=3). Spinach values are on a dry-weight basis (shade-dried 72 h before grinding, sieving, and digestion per the Materials and Methods, Salawu et al. 2015 p. 77). Irrigation water values are on a wet basis. Table 1 (p. 78) reports both rows under a single “mg kg-1” header, but the paper text on p. 78 references the water Cu value against a “2.0 mg/L” comparator, confirming that the water row is per-liter (mg/L) and the spinach row is per kilogram dry weight (mg/kg dw).

• Irrigation water (mg/L): Pb 1.639 ± 0.0016, Cd 0.037 ± 0.0021, Fe 10.046 ± 0.0003, Cu 0.295 ± 0.0022, Zn 4.236 ± 0.0017 (Table 1, p. 78).
• Spinach (mg/kg dw): Pb 0.613 ± 0.0009, Cd 0.022 ± 0.0014, Fe 25.666 ± 0.0011, Cu 1.934 ± 0.0007, Zn 1.842 ± 0.0003 (Table 1, p. 78).
• Pb, Cd, and Zn are higher in the irrigation water than in the spinach; Fe and Cu are higher in the spinach than in the irrigation water (Table 1). The paper’s abstract summarizes the contrast as “the heavy metal in the waste-water sample is higher than the spinach,” which is not strictly accurate for Fe and Cu and should not be propagated downstream as a paired-uptake claim without that caveat.
• Comparison to WHO/FAO guideline values for vegetable mg/kg (Table 3, p. 78): Fe in spinach (25.666) exceeds the cited 5.00 guideline; Cu in spinach (1.934) exceeds the cited 0.20 guideline; Cd in spinach (0.022) exceeds the cited 0.01 guideline; Pb (0.613 vs 5.00) and Zn (1.842 vs 2.00) do not exceed their cited guidelines.

Methods (brief)

• Sampling: spinach and grey irrigation wastewater collected October–November 2014 at the Samaru irrigation area, Gusau Metropolis, Zamfara State, Nigeria (p. 77).
• Sample preparation: water acidified with concentrated HNO3 in the field; spinach washed, shade-dried 72 h, ground in a mortar, passed through a 2 mm sieve, stored at room temperature (p. 77).
• Water digestion: 50 mL of acidified water evaporated to ~20 mL, 10 mL of 8 M HNO3 (98%) added and evaporated to near dryness, residue transferred with HNO3 to a 250 mL flask, 20 mL HClO4 added and boiled to white fumes, cooled, diluted to 100 mL with deionized water (p. 77).
• Plant digestion: USEPA 3050 method (Miller and McFee 1983, as reported in Odoh and Kolawole 2011): 1 g spinach in 125 cm³ conical flask, 10 cm³ HNO3, 30 min at 100 °C; +5 cm³ HNO3, 1 h at 100 °C; reduced by boiling; +5 cm³ deionized water and 10 cm³ H2O2 (60%), 30 min; filtered and made up to 50 cm³ (p. 77).
• Quantification: atomic absorption spectrophotometer (AAS); no instrument vendor, reference material, LOD, or recovery values are reported in the paper (p. 77).
• Replication: each measurement repeated 3 times; mean and SD calculated (p. 77).
• Statistics: Student’s t-test and ANOVA reported no significant difference (p > 0.05) between wastewater, spinach, and WHO/FAO guideline values (p. 79).

Implications

The paper contributes occurrence data for Pb, Cd, Fe, Cu, and Zn in shade-dried spinach grown on grey-wastewater irrigation in Zamfara State, Nigeria, plus the paired irrigation-water concentrations. The data are usable as Nigeria/Zamfara occurrence context on a dry-weight basis; conversion to fresh-weight basis for pooling with as-consumed studies requires an assumed spinach moisture content (the paper does not report fresh weight, percent moisture, or a dw→fw factor).

Wiki pages this source may touch

• Spinach
• Spinach
• Lead
• Cadmium
• Iron
• Copper
• Zinc

Verification notes

• Spinach basis confirmed dry-weight from p. 77 methods (shade-dried 72 h before digestion); paper does not report fresh-weight equivalents or moisture content, so any dry-to-fresh conversion downstream must use an external assumption.
• Table 1 header reads “mg kg-1” for both rows; paper text on p. 78 (“Cu which was a little less than the 2.0 mg/L”) confirms the water row is mg/L. Treat the Table 1 water header as a paper-side notation error.
• Paper-side internal inconsistency: Table 2 and Table 3 list “Cu 1.842” for the wastewater row, which contradicts Table 1’s wastewater Cu of 0.295 and the discussion text on p. 78 (“Cu which was a little less than the 2.0 mg/L”). Use Table 1 (Cu wastewater 0.295 mg/L) as authoritative; the “1.842” entry in the Cu row of Tables 2 and 3 is a paper-side transcription error (it matches Table 1’s spinach Zn value).
• Reproducibility detail in the paper is limited: no AAS instrument vendor/model, no certified reference material, no method LODs, and no recovery values are reported. Flag as a B-tier reproducibility profile inside an A-tier publication when synthesis pools this source.
• No brand-level data and no regulatory-event subject in the source; Part 12 review clean.

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.