A System for Quantifying Biological Oxygen Demand
Introduction:
In this study, the researchers show the techniques and instruments they used to study biological oxygen demand. They both discuss methods other researchers have used and create their own system for measuring changes in oxygen. Respiratory changes can help people understand “global carbon cycles, microbial metabolism, postharvest quality, and compost stability.” These researchers measure how oxygen decreases in a closed system to show respiratory adjustments.
Set Up:
The researchers create a simple system using a galvanic cell oxygen electrode with a system that collected the information. This system uses Apogee Instruments’ galvanic-cell oxygen probes (SO-110), which measure the partial pressure of oxygen. The probes are attached to a standard canning jar lid that can be fitted to any size jar, and they used different sized jars (125 mL to 2 liters). Additionally, canning jar lids are modified to include a hole to accommodate the sensor. To make sure the hole is airtight, they also used a custom nut from Apogee Instruments (AO-003).
Results:
Smaller jars cause faster changes in oxygen levels and therefore excel for objects or organisms with low oxygen consumption rates. Larger jars work better for longer studies because oxygen takes longer to deplete, and the jars can remain sealed longer before oxygen needs to be replenished. There are many ways to adapt this system in researching respiration.
Conclusion:
This study and reflection of best practices covers many different techniques to improve a study of oxygen depletion.
Image 2. Six galvanic-cell oxygen probes attached to the lid of one-Liter canning jars. A datalogger is shown in the background. In this example photo, hydrated media was placed in an upright position to allow drainage and increase aeration. After inserting the media and sealing the lids, the jars are placed in an insulated box to stabilize temperature.
Image 1. Photo by S N Pattenden; Green forest
- Paul Kusuma
- Bruce Bugbee