METHOD FOR ESTIMATING BULK-DENSITY OF SOFT-BOTTOM SEDIMENT CORES

Soft-bottom highly porous sediment samples can be frozen to facilitate handling, preservation, and especially separation of sediment layers before laboratory analysis, Due to core expansion upon freezing, bulk density measurements are biased (underestimation of up to 8.9% for pur e water), but bulk density in separate sediment layers can only be mea sured after freezing, Therefore, the objective of this study was to de velop a methodology that allows the actual field bulk density to be es timated from measurements on frozen cores in the laboratory, Homogeneo us soft-bottom undisturbed sediment cores (single layer) were sampled with a transparent cylindrical device in the Everglades Agricultural A rea. The bulk density of the undisturbed, unfrozen sediment cores (fie ld bulk density) was calculated by measurement of the volume and weigh t of sediment cores, After freezing, the solids fraction and frozen bu lk density on a met-basis were determined, From the collected data, th e field (i.e., before freezing) bulk density could adequately be predi cted from the frozen bulk density and the solids fraction, The method described in this paper allows field bulk density of separate sediment layers to be estimated from parameters easily measured on frozen sedi ment cores, and is therefore useful when different sediment layers req uire delineation.