Now that I almost have my E.coli markers (Almost), it is time to do something useful with them. The Seaton Sluice bathing water is Good/Excellent quality, but often flirts with being classified as sufficient. A previous study identified the bathing water as having a high chance of failure under new bathing water regulations. We need to know:
- What are the main sources of the problem?
- Where are the problems located?
- What are the options to mediate the problem?
To help us answer some of these questions the summer of 2016 saw me running around the Seaton Sluice catchment to take 14 samples just before the Environment Agency’s sampling team grabbed their bathing water sample 20 times throughout the summer. The 14 sample points were chosen to cover the whole of the catchment, and be above and below the urban areas so we can try and determine where the problem areas might be. These samples will be subject to the two methods of microbial source tracking I have been working with: 16s sequencing with SourceTracker and E.coli biomarkers. The next couple of months will be filled with lab time getting through all of these samples.
While I hope the single (grab) samples will give a nice picture of the biological sources of pollution in the catchment, I have two other approaches which I would like to explore:
- Modelling rainfall events.
- High frequency sampling.
To enable the modelling, a while ago I installed a piece of equipment at the bottom of the catchment to monitor the flow of water in the catchment. The BaroTroll 500 senses pressure, and is suspended just above the bottom of the riverbed. This tells us the pressure from the depth of the water as well as the air pressure. An air pressure sensor gives us only the air pressure allowing the depth of the water to be calculated. This gives a reading of depth every 15 minutes and stores the information on an in built data-logger.
Turning the depth into the rate of flow is the fun part, I measure the flow at 0.5m intervals across the river using an Electromagnetic gauge. I try to do this at a range of depths to give a good idea of how the depth relates to the flow.
The high frequency sampling is being undertaken by a brave MSc student, Thibault Petitpont, from the Environmental Engineering dept. We are hoping to take some measurements during an average dry day and before, during and after a heavy rainfall event. The hoping is because March and April 2017 have been incredibly dry! Fortunately we have borrowed an auto-sampler to save us camping out in a storm, fingers crossed all goes well!