Fingerprinting Environmental Contaminants in Lemna Dumpsites: A Biomarker-Based Approach for Assessing Ecological Risk in Tropical Regions

This study evaluated environmental contamination and biological stress at the Lemna dumpsite in Calabar Municipality, Nigeria, through integrated biochemical and physicochemical analyses. Soil and water samples were assessed for oxidative stress biomarkers, DNA damage, lipid peroxidation, and contaminant levels. Enzymatic activities of catalase (4.82 ± 0.21 U/mg protein), peroxidase (2.91 ± 0.17 U/mg protein), and glutathione S-transferase (5.34 ± 0.22 U/mg protein) were significantly elevated in soil samples compared to water (3.15 ± 0.18, 1.87 ± 0.14, and 3.92 ± 0.19 U/mg protein, respectively), indicating increased oxidative stress in soil microbial communities exposed to heavy metals and organic pollutants. The comet assay revealed pronounced DNA fragmentation in soil microbes, with tail length of 38.6 ± 2.4 µm and 52.4 ± 3.1% DNA in tail, compared to water samples (27.2 ± 2.1 µm and 40.8 ± 2.7%). Lipid peroxidation, measured by malondialdehyde concentration, was also higher in soil samples (8.12 ± 0.31 nmol MDA/g) than in water (5.76 ± 0.29 nmol MDA/g), confirming oxidative membrane damage. Physicochemical analyses showed acidic soil pH (5.4 ± 0.2), elevated total organic carbon (4.3 ± 0.5%), and heavy metal concentrations of lead (62.5 ± 3.2 mg/kg), cadmium (3.1 ± 0.2 mg/kg), and chromium (77.2 ± 4.1 mg/kg), all exceeding WHO permissible limits. Water quality assessment indicated slightly acidic pH (6.2 ± 0.3), high turbidity (22.5 ± 1.7 NTU), and significant microbial pollution with total coliforms at 920 MPN/100 mL and positive E. coli presence, reflecting fecal contamination likely from leachate. These findings demonstrate severe environmental degradation at the dumpsite, with clear biological effects on soil microorganisms and public health risks from contaminated water. The study underscores the urgent need for remediation strategies, improved waste management, and continuous environmental monitoring to mitigate ecological and human health impacts.