Sedimentary Records of Environmental Change Lab

Biogenic-silica content (wet-alkaline extraction) quantifies the weight percent of algal remains in sediment. It can be used to infer past changes in aquatic productivity and, in some cases, serves as a useful climate proxy.  Sediment can be analyzed rapidly at high resolution. For example, McKay et al. (2008) found that BSi content in lake sediment from south-central Alaska was correlated with summer air temperature. BSi is extracted from ~100 mg of sediment with 10% Na2CO3 and the concentration is determined with molybdate-blue reduction and spectrophotometry following the procedure of Mortlock and Froelich (1989). Contact the lab for pricing information.

Particle-size distribution (Coulter LS13-320 laser diffraction) of sediment is controlled by the prevailing environmental conditions of drainage basin, and by the dynamics of the sediment-transport and depositional systems. The particle-size distribution therefore is a fundamental characteristic of sediment (and soils) that has been used widely to track environmental changes. The distribution can be summarized as the relative proportions of sand, silt and clay. The Coulter LS13 320 laser diffraction with automated sample loader measures particle sizes with continuous resolution from 0.04 to 2000 µm.

The pre-treatment procedure isolates the minerogenic component of the sediment (or soil) from biogenic material, and uses a laser-diffraction particle-size analyzer to measure the particle-size distribution. The particle-size distribution is determined by the relative proportion of grain sizes from 0.04 µm to 2 mm, the mean grain size, and the sorting. Contact the lab for pricing information.

Hyperspectral core imaging (specim). Reflectance spectroscopy in the visible and near infrared range (400-1000 nm) can be used to identify organic substances and minerals in sediments on the basis of their diagnostic color absorption properties. The core scanner consists of sample tray that automatically moves a sediment surface through an illumination chamber below the hyperspectral camera. The spectral resolutionis 0.8 nm and the spatial resolution is 38 x 38 μm. Data analysis uses remote sensing software.