Factors affecting nitric oxide and nitrous oxide emissions from ...

levels) were destructively sampled. Calculation of the theoretical HNO2 concentration was
determined as noted below (section 4.2.5) based on the soil surface pH.
4.2.4 N2O and NO Sampling and analyses
Nitrous oxide and NOx sampling and respective flux determinations were performed as
described above (section. 3.3- 3.5). Measurements for NOx were taken on the following days
0, 1, 2, 4, 7, 11, 14, 15, 16, 18, 21, 22, 23, 25, 28, 29, 30, and 32 while N2O fluxes were
measured on days 0, 4, 7, 11, 18, 21, 25, 28, 30 and 36.
4.2.5 HNO2 calculation
Concentrations of HNO2 were calculated using the measured total NO2 - -N concentrations,
surface soil pH and the acid dissociation constant (pKa = 3.3) as follows (Van Cleemput &
Samater, 1996):
NO HNO
2
2
HNO 2 (4-1)
( pH pKa)
1
10
4.2.6 Statistical analyses
All statistical analyses were performed using Minitab (V15). A repeated measure ANOVA
was performed to test for the differences of means at the 0.05 level of significance. When data
did not follow a normal distribution they were log10(value + 1) transformed prior to analysis.
Pearson correlation and multiple linear regression analyses were also performed.
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