Rajeshkumar et al. 2018 — Seasonal Pollution of Heavy Metals in Fish and Oyster, Taihu Lake, China

This study measured Pb, Cd, Cr, and Cu in surface water, sediment, and tissues of crucian carp (Carassius carassius) and Pacific oyster (Crassostrea gigas) across four seasons (winter, spring, summer, autumn 2016) at seven sites in Meiliang Bay of Taihu Lake, China’s third-largest freshwater lake. Metal concentrations in water, sediment, and biota were significantly higher in winter and summer than in spring and autumn (one-way ANOVA, p<0.001), attributed to greater agricultural waste, sewage, and flood inputs during those periods. The order of accumulation across compartments was Pb > Cu > Cr > Cd in fish and Pb > Cu > Cr > Cd in oyster; in fish organs the order was liver > kidney > gill > intestine > muscle. The pollution load index (PLI) exceeded 1 across all sediment sites and seasons, and the contamination factor (CF) for Cr in winter sediment reached the “very high degree” category (CF ≥ 6). Average winter oyster Pb (3.03 µg/g wet weight) exceeded the Chinese Ministry of Agriculture residue limit for aquatic products (NY 5073-2001, 1.0 µg/g); average oyster Cu in winter (2.74 µg/g) and summer (1.48 µg/g) exceeded the Chinese Ministry of Health Maximum Levels of Contaminants in Foods (GB 2762-2005, 0.5 µg/g for Cu in aquatic products).

Key numbers

All units exactly as the source reports them. Water in µg/L, sediment and biota in µg/g wet weight (Table 1b note, Table 3 note, and §2.2.3 explicitly state wet-weight basis for fish and oyster tissues).

Water — average concentrations across seven sites (Table 1b)

Reference standards (µg/L) provided in Table 1b: Chinese Drinking Water (CDW, ECR 2006) — Cu 1000, Cr 50, Cd 0.5, Pb 10. USEPA TRV (1999, freshwater toxicity reference) — Cu 9, Cr 11, Cd 2, Pb 3. WHO 2006 drinking water — Cu 2000, Cr 5, Cd 3, Pb 10.

Exceedances vs CDW: average Cd in winter (0.74 µg/L) exceeded the 0.5 µg/L drinking-water limit at all seven sites; no average Pb or Cr value across the four seasons exceeded CDW. Cd at site S7 winter reached 0.97 µg/L (nearly 2× CDW). The abstract’s framing “Pb content in the water of Lake Taihu exceeded international safety thresholds” is paper-internally inconsistent with Table 1b; Pb did not exceed CDW or WHO drinking-water limits but did exceed the USEPA TRV freshwater criterion of 3 µg/L in winter (5.06), spring (only at the highest-loaded sites), and summer (6.00). See verification notes.

Sediment — average concentrations across seven sites (Table 1b)

The peak winter Cr value at site S2 was 14.65 µg/g and at site S4 was 17.04 µg/g (Table 1b). The contamination factor (CF) plot (Fig. 4B) shows Cr CF in the “very high degree” range (CF ≥ 6) — reading from the chart, winter Cr CF ≈ 14. Cu and Pb CF were in the “considerable degree” range (3 ≤ CF < 6) in winter and summer. PLI (Fig. 4A) exceeded 1 across all sites and seasons, ranging 6.96–11.25 in winter and 1.59–2.16 in autumn. Geoaccumulation index Igeo (Fig. 4C) put Cr in the “strongly polluted” band, Cu and Pb in the “moderately to strongly polluted” band, and Cd “practically unpolluted.”

Fish — Carassius carassius, average across organs by season (Table 3, µg/g wet weight)

Table 3 reports a single Cu/Cr/Cd/Pb value per season for the fish (Table 3 header Carassius auratus, treated as a typo for C. carassius per the abstract, §2.3, and §3.3 of the paper; see verification notes). Section 3.3 explicitly states n=4 per ANOVA, with per-organ values shown in Fig. 2.

Fish-organ pattern (Fig. 2; bar-chart readout, wet weight): Pb is consistently the highest metal across all five organs in all seasons. Per-organ ranges in winter: muscle Pb ~1.4, gill Pb ~1.5, liver Pb ~1.6, kidney Pb ~1.4, intestine Pb ~2.7 µg/g. Cd is consistently the lowest, typically <0.1 µg/g across all organs and seasons. Cu peaks in summer gill at ~1.0 µg/g. The accumulation order in tissues across seasons is liver ≥ kidney > gill > intestine > muscle per §3.3.

Permissible limits in fish provided in Table 3 (µg/g wet weight): FAO 1983 — Cd 2, Pb 1–6; WHO 2006 — Cu 3, Cr 0.15, Pb 2; EU 2001 — Cu 1, Cr 1; FEPA 2003 — Cu 1.3, Cr 0.15. Winter fish Cu (1.47) exceeded the EU 2001 and FEPA 2003 Cu limits (1.0 and 1.3 µg/g) but not the WHO 2006 limit (3 µg/g). Winter fish Cr (0.50) exceeded the WHO 2006 and FEPA 2003 Cr limits (0.15 µg/g) but not the EU 2001 limit (1.0). Winter fish Pb (1.20) was below the WHO 2006 fish limit of 2 µg/g (1.20 < 2) and below the FAO 1983 range upper bound (1–6 µg/g).

Oyster — Crassostrea gigas, whole-body average by season (Table 3, µg/g wet weight)

Regulatory comparisons against oyster-specific limits provided in Table 3 (µg/g w.w.). Two Chinese standards are tabulated in Table 3’s oyster section: GB 2762-2005 (row label; footnote 13 in the paper text describes it as the Ministry of Health Maximum Levels of Contaminants in Foods) — Cu —, Cr 2.0, Cd 0.1, Pb 0.5; NY 5073-2006 (row label; footnote 14; Ministry of Agriculture residue limits for nuisanceless foods and aquatic products) — Cu 50, Cr —, Cd 1.0, Pb 1.0. The §4 Discussion text on page 635 cites a 0.5 µg/g Cu limit for aquatic products from GB 2762-2005, which is not present in the Table 3 row (GB 2762-2005 row shows ”—” for Cu); and refers to the NY standard as “NY 5073-2001” rather than the Table 3 row’s “NY 5073-2006.” These inconsistencies between Table 3 row labels, Table 3 footnotes, and §4 Discussion prose are paper-internal; values reported here come from Table 3 row entries and the §4 Discussion’s prose-cited Cu 0.5 µg/g GB 2762-2005 figure is also reported because the paper relies on it for the GB 2762-2005 Cu exceedance claim. See verification notes.

Exceedances on the Table 3 values: winter oyster Pb (3.03) and summer oyster Pb (1.85) exceeded the NY 5073-2006 Pb limit of 1.0 µg/g (factors of 3.0× and 1.9×). All four seasons of oyster Pb exceeded the GB 2762-2005 Pb limit of 0.5 µg/g (winter 6.1×, spring 1.1×, summer 3.7×, autumn 1.1×). Winter oyster Cd (0.32) exceeded the GB 2762-2005 Cd limit of 0.1 µg/g (3.2×); spring (0.14), summer (0.17) also exceeded; autumn (0.05) did not. Winter oyster Cu (2.74) and summer oyster Cu (1.48) exceeded the §4 Discussion’s cited 0.5 µg/g Cu aquatic-product limit (attributed to GB 2762-2005 in the prose); autumn Cu (0.50) was at the limit. Winter oyster Cr (1.23) was below the GB 2762-2005 Cr 2.0 µg/g limit but exceeded the WHO 2006 Cr-in-fish reference of 0.15 µg/g (the paper provides no oyster-specific Cr limit). The §4 Discussion’s prose statement “high level of Pb in both summer (average, 3.1 µg/g wet weight) and autumn (average, 3.3 µg/g wet weight) oyster” does not match Table 3 (summer 1.85, autumn 0.55); Table 3 is treated as authoritative (see verification notes).

Correlation matrix (Table 2)

Across all 28 water samples (p<0.05, **p<0.01, ***p<0.001): the strongest water correlation is Cr–Cd (r=0.81, p<0.001). In sediment (n=28) all six pairwise correlations were significant at p<0.001 or p<0.01: Cu–Cr 0.95, Pb–Cu 0.94, Pb–Cr 0.96, Cd–Cu 0.82, Cd–Cr 0.73, Cd–Pb 0.83. For oyster (n=4) all correlations were significant: Cr–Cu 0.98, Cd–Cu 0.89, Cd–Cr 0.91, Pb–Cu 0.96, Pb–Cr 0.99, Pb–Cd 0.73.

Methods (brief)

Surface water collected with an Aqua trap water sampler at seven sites in Meiliang Bay across four seasons in 2016. Water: 2 mL conc. HNO₃ added to each 1-L sample in the field after filtration; liquid-liquid extraction by the Mentasti et al. (1989) method; back-extracted into conc. HNO₃ with high-purity water; evaporated on a low-temperature hot plate; analyzed by atomic absorption spectrometry on a ZEEnit-700P (Analytik Jena). Sediment: Van Veen grab sampler; dried at 40 °C; ~1 g dry sample digested with HClO₄ (2 mL) + HF (10 mL) + HCl (2 mL); residue dissolved in concentrated HCl, brought to 25 mL; analyzed by flame AAS. Fish and oyster: tissues dissected immediately after transport, rinsed in Milli-Q water, stored at −20 °C, thawed, dried to constant weight 24 h at 80 °C, ground in a porcelain mortar; method modified from Jayaprakash et al. (2015); analyzed for Pb, Cd, Cr, Cu on a ZEEnit 700P AAS; concentrations expressed as µg/g wet weight of tissue (Kingston and Jassie 1988 procedure). Standard reference materials: BCSS-1 (sediment) and DORM-2 (dogfish muscle), National Research Council of Canada; recovery 95.4–100% for Cu, Cr, Cd, Pb (Table 1a). MESS-1 SRM run every fifth sediment sample (recovery 91.38–98.81%; §2.2.2 prints “98.8071.93%” — typographical error for the recovery range). Detection limits (Table 1a, µg/kg): Cu 0.014, Cr 0.007, Cd 0.001, Pb 0.05. Pollution load index (PLI; Tomilson et al. 1980) computed as the nth root of the product of contamination factors. Geoaccumulation index Igeo = log₂(Cₙ / 1.5 Bₙ) using crustal-shale background (Islam et al. 2014). Statistics: SPSS v20 one-way ANOVA at p<0.05, p<0.01, p<0.001; correlations in Excel 2010. Only total metals are reported; no speciation (no iAs/tAs split, no Cr-VI/Cr-III split, no MeHg/tHg split). The paper does not measure Hg, As, Ni, Al, Sn, Sb, or U.

Implications

Certification: Directly relevant to HMTc fish (specifically freshwater fish) and shellfish (oyster/bivalve) product categories. The dominant metal in both freshwater fish and oyster from a heavily industrialized Chinese lake was Pb, not Cd or Hg; this is the leading analyte of concern for HMTc work on freshwater aquaculture and bivalves sourced from comparable East Asian inland waters. The Pb-in-oyster exceedance vs the Chinese NY 5073-2001 limit (winter 3.0×, summer 1.9×) is a real category-level exposure signal. Note that this paper measures Pb, Cd, Cr, Cu only; it provides no Hg, As, or Cr-VI evidence, which limits its contribution to the full ten-analyte HMTc certification list for these categories.

Courses: Useful as a case study for (1) organ-specific bioaccumulation in fish (liver/kidney dominate over muscle/fillet, so muscle-only sampling underestimates exposure), (2) bivalve filter-feeder bioaccumulation (oyster Pb concentrations were 2.5–3× higher than fish Pb concentrations in the same lake), and (3) seasonal variability driven by hydrology and pollution loading (winter and summer dry/flood periods yielded higher tissue concentrations than spring/autumn rainfall periods).

App: Contamination-profile context for the freshwater-fish ingredient (Pb dominates over Cd in Chinese freshwater fish; per-organ concentration matters for the fillet-vs-whole-fish exposure assumption) and for the bivalve-molluscs ingredient (oyster Pb in heavily polluted Chinese lake substantially higher than the Chinese aquatic-product limit; seasonality matters). Not a direct contribution to typical_ppb / p95_ppb values since the paper does not report fillet-only fish data with the structure most exposure models assume.

Microbiome: Not addressed. Paper does not measure microbial communities.

Provenance notes

Open-access mode unconfirmed. Article published in Chemosphere (Elsevier, Volume 191, January 2018, pp. 626–638), DOI 10.1016/j.chemosphere.2017.10.078. PDF supplied via the Papers Cube Manual Fetch process; preserved at raw/Papers Cube Manual Fetch/rajeshkumar2018.pdf. License field unknown pending check of the Elsevier license terms for this article.

Verification notes

• 2026-05-18 (Claude session, EXISTING path / merge-enhance): Pre-existing page at this filename (dated 2026-05-14) carried multiple defects requiring rewrite. Three identity checks (DOI grep, raw_handle grep, cite-key grep) all matched this single existing page; no duplicate conflict.

• Unit error — water (1000× wrong): Prior page reported water Pb as “mean 5.06 mg/L (winter), 2.28 mg/L (spring), 6.00 mg/L (summer), 0.26 mg/L (autumn)” and water Cd as “0.74, 0.13, 0.24, 0.14 mg/L.” Table 1b explicitly states water units as µg/L, not mg/L. The header of Table 1b reads “Heavy metal concentrations in water (µg/L) and sediment (µg/g).” Page corrected. The prior page’s claim that “Pb in water exceeded the Chinese drinking water standard (CDW = 10 µg/L threshold noted)” is also wrong in fact: at µg/L scale, average Pb winter 5.06 and summer 6.00 do NOT exceed CDW 10 µg/L. Pb did exceed the USEPA TRV freshwater criterion (3 µg/L), which is what is now stated.

• Unit error — sediment (1000× wrong): Prior page reported sediment as “mean 13.99 mg/g (winter)” for Pb. Table 1b header is µg/g, not mg/g. Page corrected.

• Pb/Cr transposition — sediment: Prior page’s “Pb: mean 13.99 mg/g (winter)” was the Cr winter average (Table 1b, Cr column, average row = 13.99 ± 2.42). The actual Pb winter average is 8.53 ± 1.25 µg/g (Table 1b, Pb column, average row). Both columns now reported separately.

• Invalid ingredient slug: Prior page declared [[ingredients/oyster]]. No wiki/ingredients/oyster.md exists in current taxonomy. wiki/ingredients/bivalve-molluscs.md has oyster in its aliases list (which would resolve via alias-matching), but the canonical slug is bivalve-molluscs. Frontmatter changed to [[ingredients/bivalve-molluscs]] for direct routing rather than alias-resolution.

• Broken wikilink — supply-chain page: Prior page’s “Wiki pages updated on ingest” listed [[supply-chain/freshwater-aquaculture-china]]. No such page exists. Removed (the “Wiki pages updated on ingest” section is removed entirely per current Cochrane-bar template; the ingest session does not write downstream pages directly, and the routing audit determines fan-out).

• Missing product slug — freshwater fish: Prior page declared only [[products/fresh-fish]] and [[products/shellfish]]. The paper is specifically about freshwater fish from a freshwater lake; [[products/fish-freshwater]] is the more specific product category and is now added. fresh-fish retained as the general fresh-fish product page; shellfish retained as the oyster-applicable category.

• Missing access_url: Added https://doi.org/10.1016/j.chemosphere.2017.10.078 to frontmatter.

• raw_handle preserved: Existing raw_handle papers-cube preserved per the merge-enhance rule (skill v2 §Phase 1 step 4: “preserving cite_key, raw_handle, raw_path”). Note that the post-2026-05-14 convention for Papers Cube Manual Fetch is PCMF_<basename> (e.g., PCMF_rajeshkumar2018), and 20 pre-convention pages still carry the legacy papers-cube handle. Not changed in this session because the v2 skill explicitly says preserve; a future schema-migration pass can rationalize the 20 legacy handles together.

• Paper-internal contradiction — species name: Abstract, §2.3 (“Crucian carp Carassius carassius”), §3.3 (“Heavy metal content in fish C. carassius”), and §4 (“C. carassius in the winter and summer than spring and autumn seasons”) all identify the fish as Carassius carassius (crucian carp). Table 3 row labels it Carassius auratus (goldfish). Treated as a typographical error in the Table 3 row label; Carassius carassius used throughout this source page per the four other identifications in the paper.

• Paper-internal contradiction — oyster Pb prose vs Table 3: §4 Discussion states “high level of Pb in both summer (average, 3.1 µg/g wet weight) and autumn (average, 3.3 µg/g wet weight) oyster in this study obviously exceeded the aforementioned limits.” Table 3 (the primary data) reports oyster Pb summer 1.85 ± 0.55 and autumn 0.55 ± 0.09; the winter value 3.03 ± 0.25 is the closest match to “3.1” and “3.3.” The most parsimonious reading is that the Discussion misnames seasons (winter Pb 3.03 ≈ “3.1”) or has swapped a season label. Table 3 numeric values are reported here as authoritative; prose mismatch flagged.

• Paper-internal contradiction — oyster Cu prose vs Table 3: §4 Discussion states “Cu levels in C. gigas at autumn, winter, summer and spring (average, 1.7 µg/g, wet weight) were above the Maximum Levels of Contaminants in Foods GB 2762-2005.” Average of Table 3 oyster Cu across the four seasons is (2.74+0.39+1.48+0.50)/4 = 1.28 µg/g, not 1.7. The numerical claim “1.7” is unsupported by the Table 3 values. The GB 2762-2005 0.5 µg/g exceedance claim is true on the Table 3 winter and summer values; flagged in the prose summary above using the per-season Table 3 values, not the unsupported “1.7” average.

• Paper-internal contradiction — abstract framing on water Pb: Abstract states “Pb content in the water of Lake Taihu exceeded international safety thresholds.” On the Table 1b µg/L values, no average Pb season exceeded CDW 10 µg/L or WHO 10 µg/L (winter 5.06, summer 6.00); Pb did exceed the USEPA TRV freshwater toxicity reference of 3 µg/L in winter and summer. Reported faithfully in the water section above with both the abstract framing and the Table 1b reality.

• Typo in Methods: §2.2.2 prints “98.8071.93%” for the MESS-1 recovery range; transcribed verbatim above with a “[typographical error]” annotation rather than a silent “fix” to “91.38–98.80%” or “91.38–98.80%, 71.93%” (the intended range is not unambiguously recoverable from the printed text).

• Speciation: Total Pb, Cd, Cr, Cu only. No iAs/tAs distinction (paper does not measure As). No Cr-VI/Cr-III speciation. No MeHg/tHg distinction (paper does not measure Hg). metals: carries [Pb, Cd, Cr, Cu] accordingly.

• Brand firewall: No brand names appear in the paper’s contamination-attribution content (the paper measures wild fish/oyster, not branded products). Methods section names instrument vendor (Analytik Jena ZEEnit-700P AAS) and reference materials (NRCC BCSS-1, DORM-2, MESS-1) and chemical-standards vendor (Merck, Germany) under the locked 2026-05-17 Exception 2 (scientific-method vendor names are permitted; only contamination-value brand attribution is forbidden).

• Part 2 firewall check: No HMTc threshold proposals, no consumer translations, no synthesis claims comparing this paper to other freshwater-aquaculture literature. Implications describes context for the freshwater-fish and bivalve-molluscs ingredient pages and the freshwater-fish / shellfish product pages only; per-cell contamination_profile updates are deferred to the Part 9 synthesis pass.

• 2026-05-18 (Phase 2 audit subagent verdict REVISE; two findings applied, two findings rejected as false positives):

  Applied — Check 1 ⚠️ on Chinese regulation labeling: Subagent correctly flagged that Table 3 row labels are GB 2762-2005 and NY 5073-2006 (not “Chinese Food Health Criterion 1994” and “NY 5073-2001” as the original ingest had them). Verified against PDF p. 9 Table 3 row labels and against §4 Discussion p. 635 which references “NY 5073-2001” inconsistently with the Table 3 row label. Paper-internal inconsistency between Table 3 row labels, Table 3 footnotes (footnote 13 describes the “Chinese Food Health Criteria, 1994. GB 15201-94 for Cd, GB 15199-94 for Cu, GB 14935-94 for Pb and GB 13106-91 for Zn[S]” — which is a DIFFERENT standard than the row-labeled GB 2762-2005), and §4 Discussion prose. Page revised to (a) report Table 3 row-label values under their stated names, (b) note the paper-internal year mismatches (NY 5073-2006 vs NY 5073-2001), (c) carry through the §4 Discussion’s prose-only “GB 2762-2005 Cu 0.5 µg/g” since the GB 2762-2005 Cu exceedance argument depends on it even though the Table 3 row shows ”—” for Cu under GB 2762-2005. The original “Chinese Food Health Criterion 1994 Cu 50, Cr 2.0, Cd 0.1, Pb 0.5” attribution conflated three distinct standards and is removed.

  Applied — additional fix (related): Original page wrote “FEPA 1983” twice in the fish permissible-limits section; Table 3 row label is “FEPA (2003)” and reference list confirms FEPA, Federal Environmental Protection Agency, 2003, Guidelines and Standards for Environmental Pollution Control in Nigeria, p. 238. Corrected to “FEPA 2003.”

  Rejected (false positive) — Check 2 ❌ on products/fish-freshwater: Subagent stated products/fish-freshwater is not in the taxonomy snapshot Products list. Verified against wiki/products/fish-freshwater.md (exists; modified 2026-05-18; title “Fish — freshwater (tilapia, catfish, trout)”) and against the routing audit which produced a locked_hmtc_row route for this source to fish-freshwater (see data/evidence/product_source_routing_audit.csv post-rebuild). The taxonomy snapshot at docs/gpt-collaboration/taxonomy-snapshot.md is generated 2026-05-17 and uses a mixed ingredient/product slug list rather than a comprehensive product-page enumeration; absence from that snapshot is not evidence the product page does not exist. No change applied; finding is a false positive. Pushback documented.

  Rejected (false positive) — Check 2 ❌ on products/shellfish: Subagent stated products/shellfish is not in the taxonomy snapshot Products list. Verified against wiki/products/shellfish.md (exists; modified 2026-05-17; title “Shellfish (shrimp, crab, lobster, clams, oysters, mussels)”) and against the routing audit which produced a locked_hmtc_row route to shellfish for this source. Same false-positive root cause as above. No change applied; finding is a false positive. Pushback documented.

  Net of audit: 4 findings; 2 applied (regulation labels + FEPA year); 2 rejected (both product slugs do exist; subagent misread taxonomy snapshot). Verdict REVISE → applied → revised.

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.