process.Ag: Process raw optical depth to CDOM spectra and analyse the...

In belasi01/RspectroAbs: Processing absorbance spectra from spectrophotometer

Description

Spectrophotometer measures opttical density (depth) (OD) or Absorbance (A), which are unit less. This program converts OD into absorption coefficent in per meter. Then a series of spectral analyses is performed.

Usage

process.Ag(sample, ID, Station, Depth, Date, pathlength, DilutionFactor = 1)

Arguments

sample	is a data frame return by read.LAMBDA850 or read.ULTRAPATH. It contains two 2 columns for wavelength (wl) and Optical Depth (OD).
ID	is the sample ID.
Station	is the station code (optional).
Depth	is the depth of the sample in meters (optional).
Date	is the date of sampling.
pathlength	is the pathlength of the cuvette in meters.
DilutionFactor	Is a multiplication factor to adjust the final Ag value if dilution was performed in the lab (default=1).

Details

The processing steps includes:

1) Ag = 2.303*OD/pathlenght.

2) Apply a null correction assuming Ag(690+/-5) = 0. If a(500) is negative after the applicatioc of the NULL correction, then the minimum a values between 500 and 690 is assume for the null correction. So Ag.offset = Ag - NULL.POINT

3) Fit an exponential model to Ag.offset for the 350 to 500 nm range: Ag.fitted = Ag(440) exp(-S*(440-lambda)) + K. This is done using cdom_fit_exponential.

4) Compute spectral slope for the 275-295 and 350-400 ranges. Compute slope ratio using cdom_slope_ratio.

5) Compute spectral curvature using cdom_spectral_curve.

Value

A list with all the computed parameters decribed above is return.

Author(s)

Simon Belanger

See Also

The cdom package for more details on the CDOM spectral analysis.

belasi01/RspectroAbs documentation built on July 27, 2020, 9:52 p.m.