|Lou testing the field equipment during a wet and|
windy November morning
Interestingly, streams and rivers are one of the many natural sources of CO2. Biological activity, mainly respiration, produces CO2 in soils, streams and rivers, which is eventually lost into the atmosphere. In order to calculate the amount of CO2 that is lost from streams, the rate of gas loss from the water needs to be measured. It is this process that Lou Maurice and I investigated using tracer tests.
|Yes it is as cold and wet as it looks!|
Gareth collects elevation survey data to
calculate the slope of a stream
The first step was to measure the flow of water in the stream. We did this using a method called ‘salt dilution’, which involves adding small amounts of salt upstream at a known and constant rate, and measuring the peak concentration downstream. After a few calculations, we can compute the velocity of the stream.
|Lou collects a sample using a syringe and special |
metal gas sample container. the water is injected
from the bottom to ensure any air bubbles are removed,
then they are taken to the BGS labs in Wallingford
where they are processed
Our initial results look promising and we hope to be able to show differences between CO2 loss from streams with steep and shallow gradients, under both high and low flow conditions. In the future we hope to be able to ‘scale up’ these findings to calculate CO2 loss from streams and rivers across the UK.
|We need to understand how different flow conditions affect the loss of CO2 from streams so we visited the same stream sections in low flow conditions e.g. summer (left) and then again in high flow conditions e.g. autumn (right)|