Ali 2024 — Microbial and heavy metal contamination in leeks, Thi-Qar, Iraq

Ali measured microbial contamination (Escherichia coli, Klebsiella) and three heavy metals (Ni, Cu, Pb) in 100 leek samples and in soil at three agricultural stations in Thi-Qar governorate, southern Iraq, across winter and summer seasons. The study reports soil and leek-tissue concentrations separately, documents a seasonal pattern (higher concentrations in summer) and a spatial gradient (markets and district samples higher than city-center samples and farm samples), and links the elevated Station 2 metals to proximity to a thermal electric station, traffic emissions, and small industrial activity. This is a conference proceedings paper (Seminar Nasional & Call Paper, SENASAINS 7th, Universitas Muhammadiyah Sidoarjo, Procedia of Engineering and Life Science Vol. 7, 2024); B-tier.

Key numbers

Soil (µg/g dry weight; mean of three stations):

• Winter: Ni 94.99, Cu 44.82, Pb 20.68 (p. 712)
• Summer: Ni 101.03, Cu 62.10, Pb 21.25 (p. 712)
• Station 2 (near thermal station, traffic, small industry) had the highest concentrations in both seasons (p. 712)
• Pb in soil reported as within the 100 µg/g dry-weight reference cited as “allowed concentration” by the author; Ni in soil exceeds 94 µg/g in both seasons (p. 712)

Leek tissue (µg/g dry weight):

• Summer market sample (highest): Ni 28.41, Cu 22.08, Pb 6.73 (p. 713)
• Winter farm sample (lowest): Ni 18.05, Cu 15.42, Pb 4.25 (p. 713)
• Rank across sampling sources: market > restaurant > farmer in both seasons (p. 713)
• Pb concentrations in leek exceeded the WHO permissible level of 5 µg/g dry weight in both seasons (p. 713)
• Ni and Cu reported as below the stated permissible limit by the author

Microbial (% of samples positive):

• E. coli, city-center markets: 29.51% positive; districts markets: 44.26% (p. 711, Table 1)
• E. coli, city-center farms: 4.29%; districts farms: 11.48% (p. 711, Table 1)
• E. coli, city-center restaurants: 3.28%; districts restaurants: 6.56% (p. 711, Table 1; X² = 82.40, df = 4, P = 0.00)
• Klebsiella, city-center markets: 37.50%; districts markets: 40.63% (p. 712, Table 2)
• Klebsiella, city-center farms: 3.13%; districts farms: 6.25% (p. 712, Table 2)
• Klebsiella, city-center restaurants: 4.69%; districts restaurants: 7.81% (p. 712, Table 2; X² = 92.60, df = 4, P = 0.00)

Methods (brief)

Heavy metals: 1 g soil digested with 15 mL hydrochloric acid plus 5 mL nitric acid in a sand bath at 80 °C for 45–60 minutes; after cooling, an additional 5 mL HCl and 50 mL distilled water added; heated, filtered, diluted to 100 mL. Plant samples washed with distilled and deionized water, dried at room temperature, ground, sieved, and digested per method cited as [17] (Barman et al. 2000). Final extracts analyzed by flame atomic absorption spectrophotometry; specific instrument vendor and model not stated in text. LODs and LOQs not reported. Microbial: 1 g samples in peptone water, serial dilutions 10⁻¹ to 10⁻⁶ plated on MacConkey and EMB agar, incubated 37 °C for 24 h; phenotypic colony identification and VITEK 2 confirmation. Three stations sampled; plant samples taken with three replicates per station; sampling January–May.

Limitations

Conference proceedings, B-tier; no DOI assigned. The abstract and one discussion sentence refer to “zinc” as a measured analyte (the abstract attributes “28.41 ppm during the summer” to zinc), but the methods, results text, all four figures of metal data (Figs. 4–7), and the explicit numeric tuples in the body identify the three measured metals as Ni, Cu, and Pb — the 28.41 µg/g summer value is Ni in market-sourced leek tissue. This is treated here as a paper-internal labeling error rather than a fourth analyte; zinc is not represented in the metals frontmatter. Analytical instrument vendor/model not specified. LOD/LOQ not stated. Numeric leek-tissue results are reported only as min/max tuples in the text plus three small bar charts (Figs. 6 and 7); per-station means by source-type are not tabulated and cannot be recovered from the figures with the precision needed for occurrence-distribution work. The “allowed concentration” of 100 µg/g for soil and 5 µg/g for leek Pb are stated by the author with reference to WHO but without specific citation. The city-center farmer E. coli rate is printed as 4.29% in Table 1 (3 positive of 8 samples) but as 4.92% in the corresponding bar in Figure 2 (p. 711); the table value (4.29%) is used here as the authoritative tabulation. Iraq, single-governorate, single-Allium-crop scope.

Implications

Direct evidence for Pb, Ni, and Cu occurrence in leek (an Allium leafy vegetable) grown near industrial point sources in southern Iraq; Pb in leek tissue exceeded the WHO 5 µg/g reference in both seasons across all three sampling-source types (market, farm, restaurant). The seasonal pattern (summer > winter) and the spatial gradient (Station 2 near thermal station > Stations 1 and 3) contribute geographic-variance context for leafy-vegetables in MENA-region market gardening systems. Microbial findings are out of scope for the heavy-metals wiki but are noted in the source page for completeness.

Verification notes

• 2026-05-18 (Claude session, merge-enhance): Re-read full PDF (8 pages, all tables and figures) against the prior page version (updated: 2026-05-15, raw_handle: papers-cube).
• raw_handle: corrected from the legacy placeholder papers-cube to the current convention PCMF_article-2-copy-5 (filename-derived).
• raw_sha256: added (955437466fd803f30490b920b3ba17a11222d212ea92ee36e7e232e9dc0369df).
• metals: corrected from [Pb, Ni, Zn, Cu] to [Pb, Ni, Cu]. The paper’s abstract names “zinc, copper, and lead” and attributes “28.41 ppm” to zinc, but the methods section, the three-element tuples in the soil and leek results, and Figures 4–7 (all labeled Ni, Cu, Pb on the x-axis) consistently report only Ni, Cu, and Pb. The 28.41 µg/g value is identified in the body as Ni in summer market leek, not Zn. The “Zn”/“zinc” mentions are treated as paper-internal labeling errors, not a fourth measured analyte.
• matrices: corrected from [plant-tissue, soil, leek, vegetable] to [leafy-vegetable, soil] to align with the controlled-vocabulary convention seen on sibling leafy-vegetable contamination source pages.
• Key numbers: prior page reported “Highest Zn concentration: 28.41 ppm during summer (from abstract; plant tissue data)” — corrected to the body’s actual attribution (Ni 28.41 µg/g, Cu 22.08, Pb 6.73 in summer market leek) and added the winter farm minima (Ni 18.05, Cu 15.42, Pb 4.25). Prior page said “Cu within WHO limits; Zn exceeds the permissible limit in both seasons” — corrected: Zn is not measured; the elevated-versus-WHO finding the paper actually makes is for Pb in leek tissue (5 µg/g reference exceeded in both seasons).
• Microbial findings (E. coli and Klebsiella percentages by source-type and location, with chi-square statistics from Tables 1 and 2) added to Key numbers; absent from prior page.
• Methods section expanded with the digestion protocol details actually stated in the paper (HCl/HNO₃ volumes, sand-bath temperature/duration, dilution scheme; flame AAS; VITEK 2 for microbial confirmation).
• Implications section: invalid wikilink [[supply-chain/soil]] (no such page) removed. Implications narrowed to what the paper supports (geographic-variance context for leafy vegetables) without inventing supply-chain claims.
• Note on products: []: leek is not currently in either the ingredient or product taxonomy (only [[ingredients/leafy-vegetables]] covers it). Routing audit lists this source under routing_malformed.csv with severity advisory only (“Source is missing optional routing-input fields; the routing layer falls back to broad scope where possible”) — not a blocking defect. If a future ingredients/leek page is created (≥5 papers on leek-specific contamination), this source’s frontmatter should be updated then.
• Audit subagent 2026-05-18 flagged a Figure 2 / Table 1 inconsistency on the city-center farmer E. coli rate (4.92% in chart, 4.29% in table); verified against PDF p. 711 — this is a paper-internal printing inconsistency. The table value (4.29%, 3 of 8 positive) is the authoritative tabulation and is what the page reports; a one-line acknowledgment added to Limitations.

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.