Effects of Nitrogen Fertilizer Application on Soil Properties and Arsenic Mobilization in Paddy Soil

Anthropogenic nitrogen (N) fertilization may substantially alter arsenic (As) behavior in the soil. However, a comprehensive understanding of how the soil As cycle responds to external N addition remains elusive. This study investigates the effects of various N fertilizers on soil properties and As mobility in paddy soil. Regardless of N sources, the concentrations of soluble As and SPLP-extractable As decreased with all N applications. Similarly, soil acidification occurred and dissolved iron (Fe) increased in most treatments, except for KNO3 addition. However, only the KNO3 application could reduce As desorption from soil minerals based on phosphate extraction. Also, KNO3 enhanced both soil catalase (S-CAT) and dehydrogenase (S-DEH) activities. Other N treatments decreased S-CAT activities, but increased S-DEH activities. Principal components analysis indicated that phosphate extractable As was associated with NH4+-N concentration and S-DEH activity, while the concentrations of soluble As and SPLP-extractable As were associated with pH, S-CAT activity, and dissolved Fe. These results demonstrated that the soil properties induced by the N application are the main drivers of As desorption in paddy soil and that KNO3 application is more eco-friendly than other N sources in As-contaminated paddy soil. This study shed light on the reasonable application of N-bearing fertilizers and the importance of soil properties to assess As mobility in As-contaminated paddy soil.