Calculating Concentrations

To calculate concentrations of pollen, diatoms, or other microfossils in samples, a spike of tracers is added to the sample during preparation. These tracers are typically plastic microspheres or an exotic spore or pollen taxon. Of the latter, Lycopodium spores and Eucalyptus pollen have most commonly been used. Microspheres are usually added as a suspension; while exotic spores or pollen are added either as a suspension or as tablets. A known quantity of tracers is added to the sample, and during analysis the tracers are counted along with microfossils. The concentration of the microfossils is determined

In order to calculate concentration data, you must enter the necessary data in the spreadsheet. Tilia can calculate concentrations in three different ways:

Method 1:

Quantity of sample (volume or mass)
Quantity of spike medium added (volume of suspension or number of tablets)
Concentration of spike medium (number of tracers per ml or tablet)
Number of tracers counted during analysis.

Method 2:

Quantity of sample (volume or mass)
Quantity of spike (number of tracers) added to sample (usually calculated as the product of 2 and 3 in Method 1)
Number of tracers counted during analysis

Method 3:

Quantity of sample examined (A known quantity of the original sample is placed on a slide, and either the entire slide is counted or a known fraction of the slide is counted. Thus, concentration is directly calculated as (number of microfossils counted)/(quantity of sample examined.)

All variables added to the spreadsheet for calculating concentrations should be assigned to the CONC group. The codes and names of the CONC variables can be anything; however, if standard codes, as described below, are used, Tilia can automatically assign the CONC variables to the appropriate parameters described above.

The examples of CONC variables below are for different variations of Method 1, which is the most common method.

Example with microsphere suspension:

Code	Name	Element	Units	Group
mic.susp:quantity added:ml	Microsphere suspension	quantity added	ml	CONC
mic.susp:concentration:number/ml	Microsphere suspension	concentration	number/ml	CONC
mic:counted:number	Microspheres	counted	number	CONC
samp.quant:volume:ml	Sample quantity	volume	ml	CONC

Example with Lycopodium tablets; quantity is number of tablets:

Code	Name	Element	Units	Group
Lyc.tab:quantity added:number	Lycopodium tablets	quantity added	number	CONC
Lyc.tab:concentration:number/tablet	Lycopodium tablets	concentration	number/tablet	CONC
Lyc.spik:counted:number	Lycopodium spike	counted	number	CONC
samp.quant:volume:ml	Sample quantity	volume	ml	CONC

Example with Eucalyptus tablets; quantity is grams of tablets added:

Code	Name	Element	Units	Group
Euc.tab:quantity added:g	Eucalyptus tablets	quantity added	g	CONC
Euc.tab:concentration:number/g	Eucalyptus tablets	concentration	number/g	CONC
Euc.spik:counted:number	Eucalyptus spike	counted	number	CONC
samp.quant:volume:ml	Sample quantity	volume	ml	CONC

Example with Lycopodium tablets; quantity is number of tablets, sample quantity in grams:

Code	Name	Element	Units	Group
Lyc.tab:quantity added:number	Lycopodium tablets	quantity added	number	CONC
Lyc.tab:concentration:number/tablet	Lycopodium tablets	concentration	number/tablet	CONC
Lyc.spik:counted:number	Lycopodium spike	counted	number	CONC
samp.quant:mass:g	Sample quantity	mass	g	CONC

Neotoma has default codes for taxa names and uses SI abbreviations for measurement units. However, Neotoma does not have default codes for elements and non-SI units, and, therefore, uses the complete element and measurement unit names in the codes. However, abbreviations can be used. Some sensible abbreviations are:

quantity added quant.add

concentration conc

number n

tablet tab

volume vol

For example:

Code	Name	Element	Units	Group
Lyc.tab:quant.add:n	Lycopodium tablets	quantity added	number	CONC
Lyc.tab:conc:n/tab	Lycopodium tablets	concentration	number/ml	CONC
Lyc.spik:counted:n	Lycopodium spike	counted	number	CONC
samp.quant:vol:ml	Sample quantity	volume	ml	CONC

After the necessary CONC data are added to the spreadsheet, concentrations may be calculated in two different ways. The following examples will use Method 1 with a microsphere suspension entered in this spreadsheet:

Select either:

Calc > Concentrations

Insert > Worksheet > Concentrations

Which will display this message dialog:

Selecting Yes will give the same result as Calc > Concentrations.

If No is selected, an empty Concentrations worksheet will appear, in which, for example, concentration results from Excel could be pasted.

Calc > Concentrations or Insert > Worksheet > Concentrations > Yes will display the Concentrations dialog box:

The Methods listed are those described above.

The Groups to include box lists the taxa groups in the spreadsheet. Select the ones you wish to convert to concentrations. Click the Include All button to include all groups.

On the right are boxes for the CONC variables in the spreadsheet. Select the appropriate variable in each box for the selected Method. Alternatively, if default CONC codes were used, click the Default Codes button, and Tilia will attempt to select the appropriate variables.

The Null Values box indicates whether null values (blank cells) in the spreadsheet should be treated as null (no data) or as zero values.

In this example, Include All and Default Codes were checked, and null values are to be treated as zeros.

Click the Ok button to calculate concentrations, which will appear an a new worksheet.

The .tlx file used in this example may be downloaded from here (Gonzales & Grimm 2009).

Crystal Lake .tlx file

CrystalLake.zip

Compressed Archive in ZIP Format 24.6 KB

Download