density fractionation

Knowledge graph centered on density fractionation with 70 nodes and 164 connections. Top connected: Potentilla, leaf water content, carbon cycling, Gunnison County, soil organic carbon stabilization.

Method synopsis

Separation of sediment organic carbon into free light fraction (FLF), occluded light fraction (OLF), and heavy fraction (HF) using sodium polytungstate density separation at 1.65 g/mL with sonication to disrupt aggregates.

Synthesized from method descriptions across 3 papers using this protocol.

Procedure from a recent peer-reviewed implementation

Steps below were extracted from the most recent peer-reviewed implementation of this protocol in the corpus — Quantifying the effect of petrogenic carbon on SOC turnover for two Rocky Mountain soils: when are petrogenic carbon corrections required? (2025), Journal of Geophysical Research: Biogeosciences. Implementations in other papers (listed below) may differ.

1. Density fractionation
   Unground aliquots separated into three density fractions using modified methods. Soils fractionated using 1.65 g/mL sodium polytungstate solution, yielding free light fraction (LF) of particulate unprotected SOM, occluded light fraction (OF) of particulate SOM physically protected within aggregates, and heavy fraction (HF) of SOM closely associated with soil minerals.
   Quantities: 1.65 g/mL sodium polytungstate solution, 3 density fractions per sampleDuration: 45 min settling, 1 hr centrifugation at 2583 RCFConditions: Laboratory conditions
   Equipment: 250 mL centrifuge bottle, 75 mL SPT, Branson Digital Sonifier 450

Typical Equipment

• sodium polytungstate (SPT-0)
• swinging bucket rotor
• benchtop mixer (GCU05R)
• Branson 450 Sonifier
• MilliQ water

Output Measurements

• mass percent of each fraction
• organic carbon concentration
• nitrogen concentration
• C/N ratios
• radiocarbon age

Papers Using This Protocol (3)

Species Studied With This Protocol

Places Where Used