Geospatial assessment of heavy metal contamination and metal-resistant bacteria in Qarun Lake, Egypt

Abstract

Background

Qarun Lake is experiencing multiple environmental challenges, notably heavy metal pollution originating from agricultural drainage water. This study presents an integrated approach that combines remote sensing and geospatial analysis of heavy metal contamination with microbiological investigations of indigenous metal-resistant bacteria.

Methods

Representative water samples were collected and analyzed for heavy metal content using atomic absorption spectroscopy. The samples were analyzed for lead (Pb), cadmium (Cd), nickel (Ni), and chromium (Cr) concentrations. The study employed Geographic Information System (GIS) techniques, specifically Inverse Distance Weighted (IDW) interpolation methods, to produce maps depicting heavy metal pollution indices and implementing spatial analysis, making use of ArcGIS (version 10.7.1). Water samples were subcultured on nutrient agar plates augmented with heavy metals. Bacterial colonies that showed high tolerance to heavy metals were identified using MALDI-TOF–MS and 16S rRNA gene sequencing.

Results

The concentrations of heavy metals Pb, Ni, Cd, and Cr ranged between 0.22 and 0.62, 0.05 and 0.31, 0.03 and 0.1, and 0.02 and 0.06 mg/L, respectively. Among seven pollution indices assessed for heavy metal concentrations, the heavy metal pollution index (HPI) varied from 265.26 to 958.60, and the pollution load index (PLI) ranged between 0.34 and 1.11. Spatial distribution maps representing the specified pollution indices in the surface waters of Lake Qarun were produced. Six isolates that showed high resistance to multiple heavy metals were identified as Actinokineospora fastidiosa, Streptomyces thermolilacinus, Enterococcus hirae, Bacillus cereus, Bacillus altitudinis, and Pseudomonas oleovorans.

Conclusions

The research demonstrates that Qarun Lake is highly contaminated with heavy metals because of agricultural and industrial waste discharge. Bacillus altitudinis, Bacillus cereus, and Actinokineospora fastidiosa are among the most potent bacterial strains capable of tolerating heavy metals. This study validates the use of isolated strains biomass as a cost-effective and efficient biosorbing agent for the removal of heavy metals from aqueous environments. Geospatial techniques have enabled geographic analyses of heavy metals in Qarun Lake. These techniques can predict metal levels following biological treatment, thus offering a method to evaluate the effectiveness of bioremediation.