Interactive Impacts of Heavy Metals and Soil Amendments on Enzymatic Activities and Microbial Biomass

Imran Ahmad; Muhammad Ibrar

Authors

Imran Ahmad Department of Geology, University of Malakand, Chakdara 18800, Dir (Lower), Pakistan
Muhammad Ibrar Department of Geology, University of Malakand, Chakdara 18800, Dir (Lower), Pakistan

Keywords:

Lead, Cadmium, Soil Additives, Microbial Biomass, Enzymatic Activity

Abstract

Both organic and inorganic soil additives are frequently used to increase the bioavailability of lead (Pb) and cadmium (Cd) in polluted soils, but these amendments may also affect microbial activity in soils by modifying heavy metal solubility. This research assessed the influence of different soil additives on enzymatic activity and the solubility of Pb and Cd in spiked soils. Soils were spiked with Pb (0, 1000, 1500 mg kg⁻¹) and Cd (0, 100, 150 mg kg⁻¹) artificially. Incubation experiments were carried out with various amendments, such as citric acid (CA; 0, 10 mmol kg⁻¹), ammonium nitrate (AN; 0, 10 mmol kg⁻¹), EDTA (0, 5 mmol kg⁻¹), compost (CO; 0, 10%), and titanium dioxide nanoparticles (TNPs; 0, 100 mg kg⁻¹). The microbial biomass carbon (Cmic) and dehydrogenase activity (DHA) declined by 66% and 47% in Pb₁₅₀₀, and by 54% and 35% in Cd₁₅₀ treatments, respectively. In control soil, compost addition gave the highest value of Cmic and DHA, followed by TNPs, CA, AN, and EDTA. But the mixed application of Pb, Cd, and soil additives caused an overall reduction in microbial activity. Among all the treatments, EDTA alone and in combination with Pb and Cd showed maximum toxicity to soil microorganisms.

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