BEST PRACTICES FOR COLLECTION OF LUMINESCENCE SAMPLES AND ESTIMATING WATER CONTENT FOR DOSE-RATE DETERMINATION: WHY SAMPLE SELECTION, COLLECTION TECHNIQUE AND WATER CONTENT MATTERS
In addition to the collection of sediment in a light-proof container (for equivalent dose calculation, DE), additional samples are needed for determining the radioactivity of the surrounding sediment (environmental dose rate, DR) and water content, which attenuates the DR. While measurement of the DR is equally important as the DE (Lumin. Age = DE/DR), sample collection for these measurements is commonly overlooked.
Most uncertainty in DR calculation is related to the water content of the sample. Generally dependent on weather conditions, sediment-air interface (outcrop drying effects), compaction/ mineral precipitation, and local water table fluctuations, in-situ moisture content samples may under or over represent average soil moisture content through geologic time. We describe how grain-size characteristics for sand to clay-dominated samples can be used in a pedotransfer function model to estimate soil hydraulic data and water retention parameters. In conjunction with mean annual water state determination, this approach allows for estimation of water content variation over changing sediment saturation conditions.