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 water, sediment, and tissues of crucian carp (Carassius carassius) and Pacific oyster (Crassostrea gigas) across four seasons at seven sites in the heavily polluted Meiliang Bay of Taihu Lake, China’s third-largest freshwater lake. Metal concentrations in fish and oyster tissues were significantly higher in winter and summer than in spring and autumn, attributed to greater agricultural waste, sewage, and flood inputs during those periods. Pb was the dominant metal in both fish and oyster tissues (order: Pb > Cu > Cr > Cd), with liver and kidney accumulating the highest concentrations relative to muscle, gill, and intestine. The pollution load index (PLI) values exceeded 1.0 in sediments across all seasons, indicating progressive deterioration, and contamination factors confirmed moderate-to-high Pb and Cr enrichment.
Key numbers
Fish (Carassius carassius) — organ tissue concentrations (mg/kg wet weight): Metal accumulation order in fish organs: liver > kidney > gill > intestine > muscle.
From Figure 2 data summaries and Table 3 (selected organ means across seasons):
- Pb in muscle: ranged from approximately 0.13 to 2.80 mg/kg wet weight; higher in winter and summer
- Pb in liver: highest among organs in winter and summer seasons
- Cd: lowest of all four metals across all organs and seasons
- Cr: intermediate; liver and gill showed higher accumulation relative to muscle
Oyster (Crassostrea gigas) — whole body concentrations (mg/kg wet weight): From Figure 3 summaries:
- Pb > Cu > Cr > Cd; highest concentrations in winter and summer
- Cd in oyster was consistently the lowest metal by concentration but showed significant species-level discrepancy (ANOVA: F = 10.166, p < 0.001), suggesting oyster-specific accumulation dynamics for Cd
Water:
- Mean Pb: 5.06 mg/L (winter), 2.28 mg/L (spring), 6.00 mg/L (summer), 0.26 mg/L (autumn)
- Mean Cd: 0.74, 0.13, 0.24, 0.14 mg/L across seasons; all below WHO drinking water standard
- Pb in water exceeded the Chinese drinking water standard (CDW = 10 µg/L threshold noted) at several sites and seasons
Sediment:
- Pb: mean 13.99 mg/g (winter), 0.14, 1.91, 1.10 mg/g spring-summer-autumn; very high winter values
- Cr: mean 8.53 mg/g (winter); contamination factor classified moderate to high
- PLI > 1 across all sites and seasons, indicating advanced quality decline
- Igeo values for Pb and Cr indicated moderately to strongly polluted sediment
Methods (brief)
Seasonal sampling across winter, spring, summer, and autumn 2016. Water: liquid-liquid extraction, AAS (ZEEnit-700P). Sediment: acid digestion (HClO4/HF/HCl), flame AAS. Fish and oyster: dissected tissues dried at 80°C, acid digestion per Jayaprakash et al. (2015), AAS. Certified reference materials BCSS-1 and DORM-2 (National Research Council Canada) used for QA; recovery 95.4–100% for Cu, Cr, Cd, Pb. Detection limits: Cu 0.014, Cr 0.007, Cd 0.001, Pb 0.05 mg/kg. Total metals only; no speciation.
Implications
Certification: Directly relevant to the HMT&C fish and shellfish (oyster) product categories. Demonstrates that Pb dominates over Cd and Cr in freshwater fish and oyster from a heavily industrialized Chinese lake — the leading species of concern is Pb, not Cd or mercury. The seasonal pattern (higher in winter and summer) provides context for why lot-level testing matters for seafood imported from affected regions.
Courses: Model case study for metal bioaccumulation in aquatic food chains; illustrates organ-specific accumulation (liver/kidney > muscle) and why fillet vs. whole fish comparisons matter for exposure assessment.
App: Fish (freshwater, Chinese origin) ingredient contamination profile contribution: Pb is the primary analyte of concern; Cd and Cr are secondary. Oyster shows similar pattern.