funding for this program is brought to you by the arts and cultural heritage fund and the citizens of minnesota [Music] it's a neurotoxin it's an element so it can't be broken down it's found all over the earth's surface in the air and in the water and it's a substance that tends to be especially prevalent in the st louis river estuary mercury is the reason why we need to limit the number of fish we eat nathan johnson is a professor of engineering at umd he specializes in coming up with ways to manage contaminants in the environment and knows a lot about mercury he has also mentored students including myself at fond du lac tribal and community college let's see if he can help break it down for us mercury is a really hard chemical to understand and deal with because it's not it's just an element and so it can't degrade into something that's not toxic it's just it's always going to be there you can't destroy mercury a lot of the mercury that makes its way into our ecosystem comes from the burning of fossil fuels and then the mercury gets into the atmosphere and can kind of blow around the whole world it's it kind of mixes up in the atmosphere and so some of the mercury a lot of the mercury that ends up in minnesota fish has originated from outside the state of minnesota i mean there has been a lot of industrial activity that has happened in the harbor over the last hundred years and so there are some kind of hot spots of mercury where it's it's more than just what you would expect blowing in out of the atmosphere and those might be contributing to why there's elevated mercury in the fish particularly in the estuary really the estuary is kind of like a backwater part of lake superior it rises and falls with the levels of the lake and it's kind of where the river crashes down over the hill and then slows down a lot and so there could be some other sort of ecosystem factors that affects the way that mercury cycles around in addition to there being local sources there's also kind of a really complicated ecosystem that might also be contributing to why there appears to be more rapid bioaccumulation in the fish and so the fish in the estuary have even higher concentrations than those upstream or out in the lake so there are two contaminants in the river mercury and pcbs um the important message here is that they're carcinogen they can be at relatively low concentrations in sediment but both these compounds are of scientific interest because they bio-magnify in the food web you know the plants at the bottom of the food web actually have more of it than the sediment and then the animals that eat the plants have even more by higher concentration and the animals that eat them even more so then the fish at the top of the food web even more so and so that's the concern with mercury pcbs is that because a lot of the fish that we like to eat like walleye are at the top of the food web they have high concentrations of mercury and pcbs and so the state has posted guidelines for what is safe fish consumption you can eat some but we don't ask you to eat much and we ask you to target the smaller individuals because the smaller individuals are less contaminated than the big individuals and that's a concern at the u.s seal site just as it is through many portions of the river julie mccor is the director of environmental services at wlssd julie is always looking for ways to reduce the mercury levels we learn more and more better ways to run the plant how to keep more solids in the plant technologies that might help us remove pollutants that we don't want in this waste stream in the first place and we not only apply that to ourselves but we work with the industries that discharge to us so that they too can reduce how much of these pollutants they're sending us the best pollution prevention is stopping that pollutant from coming here in the first place for example getting those mercury thermometers out of use and replacing them with the digital thermometers and then as far as what we're doing primarily with wastewater which is where most of my work is if you find an industry that has a mercury load we'll look through their processes with them what kind of chemicals are you using at times you can find a replacement chemical an example we often talk about is sulfuric acid which was used in one of the industries that we regulate in our pre-treatment program and they were a substantial load of mercury to our plant and what they were able to do is begin purchasing a better quality sulfuric acid which had a lower level of mercury in it and that way a lot less mercury came to wssd in the first place methods have been developed that can detect really low levels of mercury um we're looking at our like one part per trillion which is a really tiny amount that's the same as nanograms per liter one nanogram per liter is comparable to one second in 31 000 years so we're looking at very small amounts because in waters it's been determined that those very small amounts are detrimental so we kind of picked the low-hanging fruit and the things that were easy to find and now we're circling back and looking for more it sounds to me like we have a pretty good handle on how to limit the amount of mercury in the waste stream preventing it from entering the waste stream is clearly the best and easiest option but it also sounds like we can expect to have fish advisories well into the future because it's not just going to go away what else can we do to protect ourselves and the environment for mercury contamination [Music] programming is supported by western lake superior's sanitary district innovating solutions and reducing mercury pollution in the st louis river through research and community programs online at wlssd.com