Additional Information

Accurate interpretation of 210Pb concentration versus depth profile requires additional pieces of information about the cores.  This information should be provided by email when the cores are sent.  The 210Pb measurements on the cores cannot be interpreted until the information is received.  A data sheet from MyCore is available.  When completed, this sheet provides us with the information we need to complete analysis of the core. 

  1. Date the core was collected.  This is used to ascertain whether the isotopes of 210Pb and 210Po are in secular equilibrium and to correct for radioactive decay that has occurred since the core was collected. 
  2. Area of the core.  This is used to calculate the rate of sediment accumulation in the core per unit area. 
  3. Dry Weight of each section.  This is needed to correct for the amount of compaction in the core and to date the core using the CRS model.  Cumulative dry weight over the entire core is calculated so that the weight is needed for each section; not just those on which dating are performed.  This information can be obtained by several techniques. The most common methods are:
    1. Drying the entire section of the core and measuring the weight of the section
    2. Measuring the total wet weight of each section and determine the dry weight of a sub-sample of known wet weight.  This enables one to calculate the dry weight of the section from the dry weight to wet weight ratio of each section and leave most of the material untouched.
    3. Measuring (or calculating) the volume of each section and determining the wet weight from the volume of the section.  Then proceed as in b.  The conversion from wet to dry weight and wet weight must be measured very accurately since only a small fraction of the surface sections of the core are dry material.
    4. Measuring (or calculating) the volume of each section and using the bulk density of the sediment to calculate the dry mass in the section.  This method is very inaccurate unless the bulk density is known with good precision. 
  4. Depth of sample(s).    The top and the bottom of the core section that the sample originated from. 
  5. Metal concentrations or Pollen counts.  This information is not essential. However it is very useful to have since it enables one to examine the top ~5cm of the cores and to determine whether the core has been mixed (homogenized).  If the core has been mixed then the age of the sections may need to be adjusted.   
  6. Organic matter content. This information is not essential. It is very useful to check and ensure that the material in the core is of similar origin and whether the background concentration of supported Pb-210 is constant in the core.