calc_SedimentationRate: CF:CS model to estimate sedimentation rate from 210Pb...

In tzerk/leadR: Sediment Deposition and Accumulation Rates Determined by 210Pb Isotope Methods

Description

This function fits a "Constant Flux Constant Sedimentation Rate" (CF:CS) model to 210Pb activity data from different soil depths to estimate the sedimentation rate of the profile.

Usage

calc_SedimentationRate(x, reverse = TRUE, fix_a0 = FALSE,
  verbose = TRUE, ...)

Arguments

x	data.frame (required): Measured 210Pb activity at different soil depths with the following structure: | depth (cm )| activity (Bq/kg) | | [ ,1] | [ ,2] | |------------|------------------| [1, ]| ~~~~ | ~~~~ | [2, ]| ~~~~ | ~~~~ | ... | ... | ... | [x, ]| ~~~~ | ~~~~ |
reverse	logical (optional): Plot the y-axis in ascending order so that the soil surface is on top. Defaults to TRUE.
fix_a0	logical (optional): In the fitted model parameter a0 is the 210Pb activity at depth z=0. If the argument fix_a0 is TRUE, this function will take the first activity value (i.e., the value closest to the surface) as a fixed value in the equation. For fix_a0=FALSE parameter a0 is estimated by the model. Defaults to FALSE.
verbose	logical (optional):
...	Futher arguments passed to plot.

Details

Model

y = a0 * exp((l/s) * x)

• y = 210Pb activity at depth x (cm)

• a0 = 210Pb activity at depth x=0

• l = 210Pb decay constant (= 0.03114 a-1)

• s = sedimentation rate (cm/a)

• x = depth below surface (cm)

Value

A list with the following structure:

Element	Data type	Description
$summary	data.frame	summary table of important model results
$data	data.frame	original input data
$model	nls	model output generated by minpack.lm::nlsLM

Author(s)

Christoph Burow, University of Cologne

References

Szmytkiewicz, A., Zalewska, T., 2014. Sediment deposition and accumulation rates determined by sediment trap and 210Pb isotope methods in the Outer Puck Bay (Baltic Sea). Oceanologia 56(1), 85-106.

Examples

# Load example data (synthetic)
data(Pb)

# Apply the model
results <- calc_SedimentationRate(x = Pb,
                                  reverse = TRUE,
                                  fix_a0 = FALSE,
                                  verbose = TRUE)

tzerk/leadR documentation built on May 4, 2019, 3:10 a.m.