Soil Sampling Protocol for DDTs in the Ramford County
A series of soil cores are to be collected using random sampling methods such as computer generated selection or random-selection cards. The cores should be 3-12 inches in length and 1 inch wide, and should be sealed immediately after collection.
These cores, in conjunction with aerial photographs, determine the boundaries of the contaminated soils and indicate the concentrations of pesticides present through laboratory analysis. Although a minimum amount of samples is designated, collectors should be careful not to ship an excessive amount above that minimum.
Samples that weigh less or are smaller in size than PDP requirements are not acceptable. If a sample will be analyzed by more than one laboratory location, it may be necessary for the collector to pick-up duplicate amounts of the sample for shipment to each appropriate laboratory.
Laboratory Testing of DDT and other pesticide levels in various commodities
For all commodities, the entire sample shall be homogenized. For any produce, the sample should first be washed for 15-20 seconds to assure all surfaces have been rinsed. If the entire sample does not fit into the homogenizer/chopper at one time, then the sample may be homogenized in portions. All portions shall be mixed together in a clean container to assure an evenly mixed sample.
An adequate portion of homogenized sample shall be held in reserve if reanalysis and/or confirmation are needed. This portion shall be distributed among several small containers (polypropylene or Styrofoam recommended) rather than one large container. One or more portions shall be pre-weighed according to the analytical methodology. The laboratory internal SOP shall define “adequate portion” and the distribution.
An appropriate amount of homogenized sample shall be weighed for analysis. The laboratory internal SOP shall define the sample weight and the necessary precision. Then the determined portion of the homogenized sample can be chemically analyzed to determine the levels of pesticides contained.