Megan Hall: Welcome to Possibly, where we take on huge problems like the future of our planet and break them down into small questions with unexpected answers. I’m Megan Hall.
Last week, we looked at how Providence rivers have been contaminated with metals. We know humans are a major source of these metals, but could climate change be making the problem worse?
To find out, we talked to Sarah Kramer and Leo Nachamie from our Possibly Team.
Sarah Kramer: Hey Megan!
Leo Nachamie: Hello!
Megan Hall: Can you tell me why there are metals in rivers again?
Sarah Kramer: Of course! All rivers naturally contain some metals from the bedrocks they flow over. But in urban rivers like those in Providence, a lot of the metals in the water come from human sources.
Leo Nachamie: These contaminants include things like runoff from cars, asphalt, landfills, and industrial buildings like factories or power plants.
Sarah Kramer: Many contaminants are also left behind by much older activities and infrastructure. Over time, industrial sites and old homes seep metals like lead into the surrounding soil, which then gets washed into waterways.
Megan Hall: So even pollution from decades ago is still affecting us rivers today?
Sarah Kramer: Yep!
Megan Hall: Will you remind me what kinds of metals we’re talking about…
Dan Ibarra: in the Northeast, it is generally lead, but we're also concerned with other metals that come from infrastructure like copper, iron, zinc, cobalt, and there are some levels of historical uses of things like mercury
Leo Nachamie: That's Dr Dan Ibarra, a professor of Earth, Environmental, and Planetary Science and Environment and Society at Brown University. His lab studies how these metals move from soils into waterways.
Megan Hall: So how do they?
Sarah Kramer: Well, one way is during storms! Dan’s team studies Providence rivers after heavy rainfall. He says, storms flush lots of pollutants into the waterways.
Dan Ibarra: The storms tap into a system that's within the city infrastructure called the combined sewer overflow, or often called the CSO.
Leo Nachamie: The “combined” in “combined sewage overflow” means water that leaves your house ends up in the same pipe as the water that goes down storm drains on streets and parking lots.
Sarah Kramer: And these systems can fill up during heavy rains, pouring water into rivers and the bay.
Dan Ibarra: What we found is that they tend to contribute a large amount to the overall metal fluxes that we observe in the rivers
Sarah Kramer: But the sewage overflow isn’t the only source of contaminants. The stormwater also picks up metals along the way, as it runs down dirty streets and sidewalks.
Dan Ibarra: And so the storm waters serve to basically flush the system of various metals through various processes that release the metals, and so we often see elevated concentrations in the waterways when we see storm events.
Megan Hall: So how does climate change fit into all of this?
Leo Nachamie: Well climate change causes warmer temperatures, and warmer air can hold more moisture, which leads to more intense rainfall and, potentially, more frequent storms.
Megan Hall: So, climate change can cause heavier rainfall, more metals in the sewer system, AND more sewer overflow?
Sarah Kramer: Exactly! It’s really a “perfect storm”!
Megan Hall: Ok, but how worried should we be?
Leo Nachamie: All Providence residents should follow the latest public health advice about swimming or fishing in the rivers.
Sarah Kramer: And just to be clear---drinking water and river water are not the same thing. Providence drinking water is managed to keep lead levels below the legal limit.
Leo Nachamie: Dan says that pretty much all New England cities have high lead in their soil, from centuries of using lead paint and leaded gasoline. Plus, all of the manufacturing that happened here.
Sarah Kramer: But if you’re worried about how much metal is in the area where you live, you can get your soil tested.
Megan Hall: Got it! Thanks, Sarah and Leo!
That’s it for today. You can find more information, or ask a question about the way your choices affect our planet, at ask possibly dot org. You can also subscribe to Possibly wherever you get your podcasts or follow us on social media at “ask possibly”
Possibly is a co-production of Brown University's Institute for Environment and Society, Ocean State Media and WBRU.
