[Characteristics of NO Release and Influencing Factors in Grass-type and Algae-type Zones of Taihu Lake During Summer].

Spatial heterogeneity of NO generation and emissions in multi-ecotype lakes limited the accurate estimation of the NO fluxes in lakes, but few studies on the characteristics of NO generation and emissions have been conducted. In this study, NO flux at the water-gas interface, dissolved NO concentration in the water column, and NO flux at the sediment-water interface in typical grass-type and algal-type zones of Taihu Lake were analyzed during summer, and indoor micro-environment experiments were conducted to illustrate the main factors affecting the generation and emissions of NO. The results showed that the NO fluxes at the water-gas interface, dissolved NO concentration, and NO fluxes at the sediment-water interface of the emergent macrophyte type area was higher than the algae-type area and submerged macrophyte area during the summer., with NO fluxes at the water-gas interface of (115.807±7.583), (79.768±1.842), and (3.685±0.295) μmol ·(m ·h), respectively. The dissolved NO concentration in the water column were (0.051±0), (0.029±0.001), and (0.018±0) μmol ·L, respectively; and the NO fluxes at the sediment-water interface were (178.275±3.666), (160.685±0.642), and (75.665±1.016) μmol ·(m ·h), respectively. The spatial difference could be attributed to dominant plants and the concentration of inorganic nitrogen in the water column. The results of micro-environment experiments showed that nitrate and organic carbon sources could significantly increase the NO production potential of sediments, the high concentration of NH-N in the water column might inhibit the NO production in sediments, and the production rates of NO in the sediment increased remarkably when the incubation temperature increased, suggesting that the generation and emissions of NO were mainly restricted by nitrate, organic carbon, and temperature in summer.