Heavy metal content and microbial population in the soil of Riyadh Region, Saudi Arabia

Abstract

Heavy metal content, soil moisture, organic matter, pH, electrical conductivity, and the population of bacteria and fungi in the soil were all investigated. In the Riyadh region of Saudi Arabia, soil samples were collected from Al Muzahmiyya, Al-Moqbel, Wadi Hanifa, the Sadus Dam area, Al Uyaynah, and Bawdah. The amount of Fe, Zn, Ni, Cr, Cu, Co, Pb, Cdin soil samples was measured using ICP-MS. The bacteria and fungi population was determined using the soil plate count method. The correlations between the variables were evaluated using principal component analysis, aggregative hierarchical clustering, and Pearson's correlation. The data reveals that the soil pH, electrical conductivity, moisture content, and organic matter ranged from 8 to 8.9, 1.7 to 37.4 ds/m, 3.3 to 26.7%, and 5.9 to 2.0%, respectively. The mean quantity of heavy metals was detected in the following order: Fe > Zn > Ni > Cr > Cu > Co > Pb > Cd. The quantity of all heavy metals was less than the pollution level. The population of bacteria ranged from 6.54 CFU log/g to 7.07 CFU log/g, whereas the fungi population was between 4.19 and 4.67 CFU log/g. From the soil samples, Aspergillus, Penicillium, Mucor, Fusarium, Alternaria, Trichoderma, Rhizopus, and Botrytis were identified. The soil pH and the population of bacteria and fungus had a strong negative correlation. A negative correlation was also found between Cd and the population of bacteria and fungi. A positive correlation was noticed between fungi and Zn. The effect of soil properties on fungal diversity was also noticed. Thus, it can be concluded that the soil properties in this area vary greatly. The soil of this region is mild to very alkaline, with a moderate to high salinity. The findings demonstrate that soil factors have an impact on the region's microbiota. Although the heavy metal content in this region is not yet above the pollution threshold, a timely evaluation is suggested.