compute_flux: Compute respiration flux from concentration data.

In PNNL-TES/picarro.data: Parse and Compute on Picarro Analyzer Files

Description

Compute respiration flux from concentration data.

Usage

compute_flux(time, gas_ppm, volume_cm3, tair_C, pressure_kPa = 101.325,
  debug_plot = FALSE)

Arguments

time	Time (typically in seconds); numeric vector
gas_ppm	Gas (e.g. CO2 or CH4) concentrations, ppmv; numeric vector
volume_cm3	System volume, cm3; numeric
tair_C	Air temperature, C; numeric
pressure_kPa	Air pressure, kPa; numeric
debug_plot	Produce a plot of data and fitted model? Logical

Details

We derive the rate of concentration change via the slope of the linear regression of all data points of concentrations versus time. One problem with this method is that the linearity attributed to the regression is incorrect in a strict sense, since the gradients in water vapor and CO2 decrease over time in a closed chamber (see discussion in Steduto et al. below). This method should thus not be used for long measurement periods.

Value

The gas flux, µmol per unit time.

Note

The computed is not area- or mass-corrected.

References

• Steduto et al. (2002), "Automated closed-system canopy-chamber for continuous field-crop monitoring of CO2 and H2O fluxes" AFM 111:171-186 http://dx.doi.org/10.1016/S0168-1923(02)00023-0.

• Campbell and Normal (1998), An Introduction to Environmental Biophysics, ISBN 978-1-4612-1626-1. New York: Springer-Verlag, 286 pp.

• LI-COR Biosciences (2015), Using the LI-8100A Soil Gas Flux System & the LI-8150 Multiplexer, 984-11123. 238 pp.

Examples

# ten-second CO2 rise at room temperature
compute_flux(1:10, 401:410, volume_cm3 = 2000, tair_C = 20)

PNNL-TES/picarro.data documentation built on Nov. 14, 2019, 11:03 p.m.