Study finds changing dissolved organic carbon in Maine lakes key to maintaining drinking water quality
Transcript
Jasmine Saros:
We looked at six lakes in the state. We partnered with different drinking water districts. All six of these lakes are drinking water sources.
We were interested in trying to understand how storms affect these lake ecosystems. In particular, we’re trying to understand how something called dissolved organic carbon is changing in Maine’s lakes. It’s one of the most important substances in lake ecosystems, but it’s not talked about that often.
Dissolved organic carbon is a natural material. It comes from the forest, essentially, and from soils. It comes as leaves and needles degrade, for example. The concentration of that material has been increasing in lakes of Maine over the last two decades or so. We think that’s a good sign. We think it’s recovery from acid deposition, but there may be another driver involved here as well.
We know that the frequency and severity of storms has been increasing over the last 60 years in Maine. We’re trying to understand to what extent do those storms play a role in these increases in dissolved organic carbon.
Dissolved organic carbon is important in drinking water lakes because it can interact with some of the treatment processes that drinking water districts use. It can then form some harmful by‑products, so it’s important that we monitor what’s happening with this material, so that we can adapt our treatment strategies, if needed, with storms.
There were three different patterns of response. We found that some lakes showed no response to storms. They’re pretty large lakes, they hold a lot of water, and storms don’t have a big impact on them.
Then there were two other categories of response. We saw a flashier response where, right after a storm, there was a big spike in dissolved organic carbon. After a few days, it declined back to the same value as before the storm.
Then we also saw what we called a sustained response where we didn’t see as big of a spike in those systems, but we saw that the concentration of DOC increased, and it stayed higher after the storm.
That type of information can be useful for the water district because they can understand whether they’ll need to modify their treatment strategies with storms.