Heavy metals and microbiological assessment of soil-plant system of flooded areas applied on the chard (Beta vulgaris)

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 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. 20 samples of soil and sludge were prepared by extraction with agua regia and DTPA, for measurement of pseudo-total and available amounts of metals. Samples of chard were taken from flooded area and from area outside of floods (controls). The chard samples were divided to roots stems and leafs. The quantity of seven heavy metals (Cu, Zn, Ni, Co, Pb, Cd, Fe, Cr and Mn) were measured by means of Atomic Absorption Spectroscopy with flame atomization (FAAS). The total bacterial count was determined using R2A agar, while the Most Probable Number (MPN) method was applied for quantifying total coliforms and spore-forming bacteria. CN analyzer measured 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 mostly was not higher in heavy metals than soil, but it had higher amounts of C, N, Ni and Co. Soil samples showed high background concentrations of Pb and Cd and in some cases concentrations were higher than permissible amounts. In plants, highest concentrations of heavy metals were found in roots and leafs. Zn, Mn and Co had positive (root/shoot) translocation factor in all cases. The highest total bacterial count, exceeding log 8, was observed in three soil samples. In contrast, two samples of sludge exhibited a significantly lower bacterial abundance, falling below log 3. In some cases, chard had amounts of Cd higher than permissible, but it is not a consequence of flooding. Flooding increased C, N, Ni and Co and decreased bacterial count.