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Podcast #8 transcript: GEOSMIN in South Carolina Waters, What is it?
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Subject: USGS Water Quality Specialist Celeste Journey discusses Geosmin. What is it? What causes it? and Will it harm you?
To listen to this podcast:
[Intro]: Audio and mix– Geosmin in the news - Tens of thousands of upstate homeowners may have noticed a funny taste or smell in their water recently.
Douglas: There's something about clean water that engages our aesthetic instinct. When you pour nice cold glass of water from the tap, you expect to be clean, and clear and well, certainly not to have any unpleasant odor. But if it does, humans are able to detect it at unbelievably low levels.
[Intro-Reprise]: Audio and mix– Geosmin in the news - You may have noticed the water from you tap doesn't smell or taste right. Music: It tastes like dirt, like you smell dirt. An organic compound called GEOSMIN was likely washed into the lake.
Douglas: Today on our program Geosmin in South Carolina's waters, where it comes from and will it harm you. I'm Ray Douglas and this is Water Science for a Changing World.
Douglas: Celeste Journey is Water Quality Specialist for the South Carolina Water Science Center. Celeste thanks for joining us today.
Journey: Oh it's great to be here.
Douglas: Basically what is Geosmin?
Journey: If you have ever gone to a garden that has been freshly tilled and you grab a handful of the freshly tilled earth and take a smell and you smell that earthy smell, that's actually Geosmin.
Douglas: OK, so how and where does it occur?
Journey: Geosmin is naturally produced in both the soil and lakes, and reservoirs and streams. In the soil it is often produced by a bacteria. This bacteria is called actinomycetes.
Douglas: Ok, actinomycetes, can you expand on those, what are they?
Journey: One of the genera of actinomycetes is streptomycetes it is actually bacteria that produces the streptomycin an antibiotic that we commonly use. But in the lakes, and rivers and streams often it's not that bacteria, but instead blue-green algae.
Douglas: Isn't blue-green algae the type of algae that you hear about in the lake warnings in the midwest?
Journey: That's correct. These are more like the weeds of the algae community, they are the ones that are often considered nuisance algae.
Douglas: OK, so the Geosmin, the stuff you can smell, is it harmful?
Journey: Geosmin in itself is not harmful it is simply a compound that humans can detect at very low levels. The human detection threshold is considered ten parts-per trillion, which is a very low amount.
Douglas: OK, wait a minute. You have raised two points of concern. First the human detection threshold is ten parts-per trillion. Can you explain just how small of an amount that actually is?
Journey: A nanogram per liter or part of per trillion is an extremely small amount, we are talking about just a drop in an olympic size swimming pool and people are able to detect it.
Douglas: Obviously that is a very low concentration and you've said that Geosmin is not a human health threat and it is naturally occurring. So what's the problem with Geosmin?
Journey: The problem is that water treatment plants can not remove it from their system, and so people start tasting this earthy taste in their drinking water and, it is not a very pleasing thing. It is more of an aesthetic problem, not a harmful problem.
Douglas: Aesthetics, that can be kind of subjective. So there has to be a lot more to Geosmin than that. Why is Geosmin so important, and why is it important enough that the USGS would be involved?
Journey: Geosmin can co-occur with toxins, and toxins are harmful to humans. They are also harmful to aquatic life and they are harmful to pets who may be swimming in water when they are present.
Douglas: So, the presence of Geosmin is sort of a warning sign. It is a symptom that may be more harmful bacteria could emerge. So what USGS work is being done here in South Carolina?
Journey: There's an interest to know more about Geosmin by many water utilities and specifically in the Spartanburg area of South Carolina. A water utility wanted to know more about this sporadic occurrence of Geosmin in their water system.
Douglas: So what was the main reason for this study?
Journey: One of the focuses was to determine if the source of Geosmin was actually happening in the lake because of production by algae, or if it was coming from the water shed being delivered in soils with the bacteria on the soils.
Douglas: So what was the answer USGS came up with?
Journey: What we found for those reservoirs is that the source was actually occurring in the lake by algae production. Specifically by blue-green algae. There are certain species of blue-green algae that produce Geosmin and they also can produce toxins.
Douglas: I understand that blue-green algae at its worst can produce algal blooms, really nasty looking stuff on the surface of the water. Was that about to occur?
Journey: In the two lakes we studied this was not a problem, alga blooms were not apparent and were observed, but we did know that the blue-green algae were present in the reservoir at the time of sampling and when Geosmin occurred.
Douglas: So were the findings helpful to the cooperator and how are they using your findings?
Journey: This study was very beneficial to Spartanburg Water they know now that their nutrient management strategies in their water shed are being very effective and they are controlling blue-green algae occurrence in these reservoirs, and preventing the concurrence of toxins with Geosmin occurrence.
Douglas: But again, we are talking about highly diluted concentrations. Is there anything that we can change, is there anything that residents can do to prevent this from happening?
Journey: The watershed does contribute nutrients and of course people live in the watershed. One of the things residents within the water shed and around the lake can do to support the good water quality in Lake Bowan and reservoir number one is to: maintain their lawns effectively; reduce the amount of fertilizer applied and when they apply it; and also making sure that their septic tanks are well maintained according to code. This will reduce the amount of nutrients and help keep the level of nutrients entering the lake at a low level, and provide long-term water quality in these lakes.
Douglas: Will the results from this study be the same for other lakes in South Carolina?
Journey: The findings from this study are unique to this reservoir and we are not really sure how applicable this would be within other lakes in South Carolina. It definitely does not fit the conditions that we see in the midwestern reservoirs and it would be a great question to try and answer to see how applicable this natural phenomenon of Geosmin occurrence is to other reservoirs in South Carolina and in the southeast.
Douglas: Celeste, Thanks for taking time to be with us today and for all the great work you and your team do here in South Carolina.
Journey: Thank You! I really enjoyed being here and getting a chance to get to show some the great research we were able to do recently.
Douglas: That was Celeste Journey USGS Water Quality Specialist for the South Carolina Water Science Center. For more information on Geosmin visit us on the web at sc.water.usgs.gov. Click on publications and look for fact sheet number 2009-3043.
[Close]: Audio and mix– from Geosmin in the news - You may have noticed the water from you tap doesn't smell or taste quite right. The local water company says there is a reason. An organic compound called GEOSMIN. It tastes like dirt, like you smell dirt. An organic compound called GEOSMIN. Tens of thousands of upstate homeowners may have noticed a funny taste or smell in their water recently but water officials say the water is.
Water Science for a changing world is a product of the U.S. Geological Survey's South Carolina Water Science Center.