Kovacik et al. 2024 — Microelements and fatty acids in grass carp muscle, Slovak Republic
Kovacik et al. measured 16 microelements plus total mercury in dorsal muscle of 36 grass carp (Ctenopharyngodon idella) harvested from a university experimental pond in Kolinany, Slovakia during summer (n=18) and autumn (n=18) seasons. The pond is adjacent to intensive agricultural activity and connected to a wastewater treatment plant. All metals were measured by ICP-OES (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Ni, Pb, Se, Sr, Zn); total mercury was measured separately by CV-AAS. Cadmium and cobalt were below the limit of quantification in all samples; arsenic was below LOQ in more than 88% of samples; lead was below LOQ in more than 66% of samples; selenium was below LOQ in approximately 50% of samples. The overall elemental ranking was Fe > Zn > Al > Sr > Ba > Ni > Se > Cr > Cu > Mn > Pb > As > Li > Hg. Total hazard quotient (TTHQ) ranged 0.27–0.76, below 1 in all individuals; mercury and nickel jointly accounted for 49% of the TTHQ and were identified as the elements of most concern.
Key numbers
All concentrations are in mg/kg wet weight (mean ± SD; n=18 per season).
| Element | Summer | Autumn | p value |
|---|---|---|---|
| Al | 17.38 ± 4.95 | 28.92 ± 5.63 | <0.0001 |
| As | <LOQ (most samples) | <LOQ | — |
| Ba | 5.94 ± 1.08 | 5.59 ± 0.98 | 0.024 |
| Cd | <LOQ | <LOQ | — |
| Co | <LOQ | <LOQ | — |
| Cr | 0.75 ± 0.15 | 1.57 ± 0.71 | <0.0001 |
| Cu | 1.07 ± 0.31 | 1.11 ± 0.16 | 0.192 |
| Fe | 21.10 ± 4.99 | 36.99 ± 9.35 | <0.0001 |
| Hg (tHg, CV-AAS) | 0.030 ± 0.013 | 0.020 ± 0.004 | 0.061 |
| Li | 0.06 ± 0.05 | 0.02 ± 0.01 | <0.0001 |
| Mn | 0.81 ± 0.13 | 0.78 ± 0.26 | 0.079 |
| Ni | 2.13 ± 1.24 | 4.29 ± 1.85 | 0.0002 |
| Pb | <LOQ (>66% samples) | <LOQ | — |
| Se | <LOQ (~50% samples) | <LOQ | — |
| Sr | 10.02 ± 1.45 | 8.64 ± 2.41 | 0.006 |
| Zn | 28.17 ± 6.59 | 26.41 ± 4.47 | 0.355 |
ICP-OES LOD (µg/L): Al 0.20, As 1.50, Cd 0.05, Cr 0.15, Cu 0.30, Fe 0.10, Ni 0.30, Pb 0.80; CV-AAS tHg detection limit 1.5 ng/kg.
TTHQ range: 0.27–0.76 (THQ < 1 for all individuals). Main contributors to TTHQ: Hg + Ni = 49%.
Methods (brief)
ICP-OES (Agilent ICP OES 720) after closed-vessel microwave acid digestion (HNO3/H2O2). CV-AAS (AMA-254; Altec) for total Hg by direct solid analysis. Certified reference materials ERM CE278K, ERM-BB184, BCR-274 for QA; recoveries 89–99%. All As reported is total arsenic (ICP-OES, no speciation); iAs/tAs split not available.
Implications
Certification: Grass carp from this Slovak agricultural pond show Cd and Co below LOQ in all samples; tHg (0.012–0.053 mg/kg) is well below EU/Codex limits for fish (0.5 mg/kg). Ni (up to ~6 mg/kg in autumn) is the primary metal of concern alongside Hg. No EU MRL exceedances are reported, but the Ni concentrations are notable given the agricultural context.
Courses: Illustrates how freshwater fish grown near wastewater treatment plants and intensive agriculture can accumulate Ni and Al; seasonal variation (higher in autumn) is ecologically significant.
App: Provides baseline ranges for multiple metals in freshwater fish (grass carp, SK); Cd and As confirmed at or below detection in this species/location.