Fig. 3. Methane emission rates for 9 Sept. 1999 calculated using the tracer and integrated horizontal flux (IHF) methods. Closed circles, tracer method by ratio; open circles, tracer method by regression; open squares, IHF method. The individual points are offset on the x axis for clarity. The error bars are the relative precision (1) errors on each point propagated through Eq. [1] assuming absolute errors of 0.5 nmol mol^–1 for each N₂O measurement, 4 nmol mol^–1 for CH₄, and 5% for the N₂O release rate.