Oxidation of Nitrite to Nitrate in a Soil Column

Abstract

A previously derived model for disappearance of nitrite with depth in an open soil system was tested with an especially built column filled with a sand‐soil mixture. Apparent rate constants for nitrification increased with an increase of population of nitrifiers as was expected. Nitrifiers increased almost logistically during two months in the upper portion of the column and reached a maximum population, but numbers fluctuated below the maximum population at lower depths. A decline in population density after a maximum was reached at a lower depth is attributed to partial starvation, owing to nearly complete oxidation of nitrite in the upper regions and to oxygen depletion.

Effects of urea fertilization and liming on nitrification in cerrados soils (Brazil)

“…Several studies have indicated that the supply of ammoniacal fertilizers to soil can increase the populations of Nitrosomonas (McLaren 1971;Ardakani et al 1974). Similar results for Nitrobacter have also been reported (Ardakani et al 1973). On the other hand, the soil pH is known to be a limiting factor for nitrification.…”

Calculation of kinetic rate constants from steady‐state soil profile concentration measurements

“…have been carried out using equation (8) with g1 = co, i.e. the effect of dispersion has been ignored both in the transport equation (1) and in the surface boundary condition (5a), i.e. condition (5b) has been used.…”

“…Clearly, the zero-and first-order rates are limiting cases of the Michaelis-Menten rate. The main difference between these limiting cases and the Michaelis-Menten rate is that the latter is non-linear in c, as is the governing transport equation (1). Unlilke linear rates, exact solutions for non-linear rates are rarely available even for the steady-state transport equation (1).…”

“…The effect of different choices for the exit boundary condition has been discussed in detail e l~e w h e r e .~~-~O Of interest here is the fact that if the column Peclet number, Pe( = ul/D), is greater than 4, then the concentration profile in the region x z I is influenced by a boundary layer of width O(D/v),4' where 0 means 'of the order of and the ratio D/v is termed the dispersivity. In Figure 1 we display the effect of the boundary layer for the case of a zero-order sink term, i.e.f=fo in equation (1). The curves in the figure, calculated for P, = 10, are for soil profiles that are (I) semi-infinite; (11) finite with boundary condition (6); and (111) finite with boundary condition (7).…”

Nitrification Studies at Non-limiting Substrate Concentrations

“…Macura & Kunc (1965) passed ammonium ions continuously through a soil column and analysed the effluent for ammonium, nitrite and nitrate ions. Ardakani, Rehbock & McLaren (1973) extended this system by having sample ports to observe behaviour at different depths within the column. Bazin & Saunders (1973) replaced the soil with glass beads and provided an inorganic medium containing ammonium ions after inoculation of the beads with pure cultures of nitrifying bacteria.…”