纳米银和银离子对土壤中硝化微生物及其氨氧化速率的影响

为研究纳米银对土壤硝化微生物及其氮转化的影响,采用土壤培养方式,对不同剂量纳米银(10、50、100 mg·kg~(-1))和银离子(1、5、10 mg·kg~(-1))暴露下黄棕壤和水稻土硝化细菌数量、土壤酶活性、amoA基因丰度、NH_4~+-N与NO_3~--N含量变化以及土壤潜在氨氧化速率进行研究.结果表明,纳米银和银离子暴露后,2种土壤亚硝酸细菌和硝酸细菌数量显著减少;土壤酶活性受到抑制,对脲酶的影响大于过氧化氢酶;土壤氨氧化细菌(AOB)和氨氧化古菌(AOA)的amoA基因丰度均降低,对AOB基因丰度的影响大于AOA.在2种土壤中外源添加(NH_4)_2SO_4时,随着纳米银和银离子暴露剂量增加,土壤NH_4~+-N含量累积,NO_3~--N含量减少,氨氧化速率降低,铵态氮向硝态氮的转化受阻.综上所述,纳米银和银离子对土壤硝化微生物产生毒害作用并影响铵态氮转化,且影响程度与土壤理化性质有关.

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.