More surprises: details along the dyke

Nearly two weeks ago I took samples along the dyke (Oostvaardersdijk) from Lelystad, via Almere to Zeewolde. The post about this set of samples showed a map with pH values. Somewhere at the beginning of the parking IJmeerdijk the pH value was rather high: 8.7 Previously the same high value also came up, so now I was looking for more detail. This time I planned to look at the other side of the bridge as well. We live in the “new land” (polder), but after crossing the bridge the “old land” is reached. Would things be different there?

To be honest, I didn’t think it would be possible to defeat the high pH score of the Hoornse Plas in the province of Groningen (9.57), but this time things were even more extreme. Again it was in an area where people are chilling out at the beach (a very small beach), SUP-ing (Stand-Up Paddle-boarding –  I didn’t know it was an abbreviation), rowing or swimming.

The cause of the high pH is probably not at the Almere side after all, because there the pH values over there were much lower. Here the top-score was 9.70 – soapy water again! I still don’t know if this is caused by human presence.

Yet it was a bit strange that about 750 metres away from the small beach the pH was still 9.63! Because the sampling was done at this point first, I wondered whether it could be the shells at the beach. After mixing a sample of those with some demineralised water, the pH I got was only 8.08. Surely not an explanation.

The good news is that – despite the high pH – a lot of little fish were swimming in all the Muiderberg-locations. At least this would mean the water was not toxic. Most likely the ammonia-concentration was low. Of course the pH will go up when the weather is hot, but now it was only around 25oC

Getting samples was not easy this time and I had to walk at some of the locations, looking for a good spot (not at a beach or harbour itself, but closer to open water). Again the pH-values are plotted on a map.

Again all values are the average of three samples (third one kept) and again I measured the values of the third sample again when back at home – also checking the reference buffers before and after. Standard deviations (of the samples) were 0.015 or less. The reference values were never more than 0.03 off, so the measurements are reliable. Of course the values remeasured at home were about 0.05 – 0.2 lower, as explained in a previous post.

By now it is time to move on and investigate soil as well. Conductivity will also be added in the future and hopefully some other analytical values.

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