We combine field observations, microcosm, stoichiometry, and molecular and stable isotope techniques to quantify N2O generation processes in an intensively managed low carbon calcareous fluvo-aquic soil. All the evidence points to ammonia oxidation and linked nitrifier denitrification (ND) being the major processes generating N2O. When NH4+-based fertilizers are applied the soil will produce high N2O peaks which are inhibited almost completely by adding nitrification inhibitors. During ammonia oxidation with high NH4+ concentrations (>80 mg N kg−1) the soil matrix will actively consume oxygen and accumulate high concentrations of NO2−, leading to suboxic conditions inducing ND. Calculated N2O isotopomer data show that nitrification and ND accounted for 35–53% and 44–58% of total N2O emissions, respectively. We propose that slowing down nitrification and avoiding high ammonium concentrations in the soil matrix are important measures to reduce N2O emissions per unit of NH4+-based N input from this type of intensively managed soil globally.

No abstract

No abstract

To investigate the fire behavior under low pressure, four configurations of cardboard box fires were comparatively tested in a sea-level city, Hefei, and a high-altitude city, Lhasa. During each test, mass burning rate, total heat release rate, multipoint flame temperature, and radiative heat flux were measured. From the experimental data, some specific fire behavior was observed that (1) the mass burning rate divided by fire base dimension can be correlated against the production of pressure-squared times length-cubed (P 2 L 3) to the power of 0.31, (2) the heat of combustion is lower in Lhasa probably due to the incomplete solid pyrolysis limited by oxygen, (3) the dimensionless plume temperature is correlated against the dimensionless flame height with a pressure term to the power of 22.0, and (4) the relative flame temperature estimated from the radiative heat flux indicated that the overall flame temperature is higher in Lhasa.

No abstract