[Effects of Silver Nanoparticles and Silver Ions on Soil Nitrification Microorganisms and Ammoxidation]

In order to study the effect of nanosilver on soil nitrification microorganisms and nitrogen transformation, soil culture experiments were carried out. Yellow brown soil and paddy soil were first spiked with different doses of nanosilver (10, 50, 100 mg·kg^-1) and silver ions (1, 5, 10 mg·kg^-1). Then, the number of nitrifying bacteria, activity of soil invertase, amoA gene abundance, NH₄⁺-N content, NO₃^--N content, and soil potential ammonia oxidation rate were determined. The results showed that the number of nitrite bacteria and nitrate bacteria decreased significantly when the soils were treated with nanosilver and silver ions. Soil invertases were inhibited, and the effect on urease was greater than that on catalase. The amoA gene abundances of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) decreased, and the effect on the gene abundance of AOB was greater than that of AOA. When (NH₄)₂SO₄ was added to the soil, nanosilver and silver ion pollutants caused NH₄⁺-N to accumulate, and the contents of NO₃^--N were reduced, the rate of ammonia oxidation decreased, and the transformation of ammonium nitrogen to nitrate nitrogen was inhibited. This research suggests that nanosilver and silver ions can have toxic effects on soil nitrification microorganisms and ammonium nitrogen conversion, and the degree of influence was found to be related to the soil physical and chemical properties.