Heavy Metals and Microbiological Assessment of the Soil–Plant System of Flooded Areas Applied on Chard ( <i>Beta vulgaris</i> )

Sewage, animal feces, heavy metals, pathogenic microbes, and other pollutants can contaminate floodwater. Fresh vegetables that have been submerged in floodwater or that might have been exposed to contaminated water are not safe to consume. Pollutants may enter plant tissues in addition to being on the outside of fruits and vegetables. In the autumn of 2024, there were great floods in central Bosnia and Herzegovina. The aim of this study was to determine the effect of floods on heavy metals and microbe content in the soil and plant tissue. Twenty-one samples of soil and sludge were prepared by extraction with aqua regia and EDTA, for the measurement of pseudo-total and available amounts of metals. Samples of chard were taken from flooded areas and from areas outside of floods (controls). The chard samples were divided into roots, stems, and leaves. The quantity of nine heavy metals (Cu, Zn, Ni, Co, Pb, Cd, Fe, Cr, and Mn) was measured by means of Atomic Absorption Spectroscopy with flame atomization (FAAS). Statistical evaluation included descriptive statistics (maximum, minimum, and average), principal component analysis (PCA), correlations, bioaccumulation factor, and translocation factor. The total bacterial count was determined using R2A agar, while the Most Probable Number method was applied for quantifying total coliforms and spore-forming bacteria. The CN analyzer measured the total content of C and N. The average concentrations of metals followed the sequence Cd < Co < Cr < Cu < Ni < Zn < Pb < Mn < Fe. The sludge had the highest average content of Pb, Fe, Cu, and Zn. Soil samples showed high background concentrations of Pb and Cd, and in some cases, concentrations were higher than permissible amounts. In plants, the highest concentrations of heavy metals were found in roots and leaves. Zn, Mn, and Co had positive (root/shoot) translocation factors in all cases. The highest total bacterial count, exceeding log 11, was observed in three soil samples. In contrast, two samples of sludge exhibited a significantly lower bacterial abundance, falling below log 6. Chard showed high ability to accumulate Cu, Zn, Ni, Fe, Mn, and Co. In some cases, chard has amounts of Cd higher than permissible, but it is not a consequence of flooding. Although high concentrations of lead are found in the soil samples, it is mostly kept within the root system.