Author: Stephen Ornes / Source: Science News for Students

On a clear, sunny Tuesday afternoon, last August, Andreas Fath climbed out of a river in Paducah, Ky.
A small crowd was on hand to witness his setting a new world record. This man had just finished swimming the entire length of the Tennessee River — 1,049 kilometers (652 miles). And he did it in just 34 days!The 52-year-old man had taken on this Herculean swim for science. A chemist from Hochshule Furtwangen University in Germany’s Black Forest, Fath’s month-long swim was part publicity stunt and part ongoing science. His primary goal was not to get his name into Guinness World Records. What really drove this aquatic trek was a desire to bring attention to water pollution.

Fath’s crew included his family. They, along with students and other researchers, often took part in the grand adventure. Sometimes they swam with Fath. Other times they cruised nearby on a 6-meter (18-foot) pontoon boat. Every day, that crew collected samples of the water. So did Fath. The wetsuit he wore had a sensor to detect pollutants.
Martin Knoll, who helped organize Fath’s swim, also took part. Knoll is an environmental scientist at the University of the South, in Sewanee, Tenn. He describes this 2017 swim as “a vehicle for getting people interested in water quality” and how we sometimes pollute water without realizing it. He says, “It’s good for people to be aware of all these things.”
Like other scientists, Knoll and Fath are worried about the health of rivers, oceans and other bodies of water. Toxic chemicals, such as pesticides, run off of the land and collect in streams and coastal waters. So do other wastes.
Among them are plastics. One 2016 study suggested that within another 35 years, the oceans could host more plastic (by weight) than fish. Other scientists think that may be an exaggeration. But either way, plastic clearly is a big problem. This and other pollutants affect not just oceans and rivers — like the Tennessee — but all the living things that depend on those bodies of water.
If people knew more about the role that freshwaters play in the health of the overall environment, Fath says, they might think more about the role their activities play in polluting the aquatic world. As a scientist, Fath has published papers on water pollution. That’s a good way to reach other scientists, he says. But to make a bigger splash, he’s turned to staging dramatic adventures. For the public, he notes, “I’ve learned that it’s better to do it this way.”
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First, the Rhine
The Tennessee wasn’t Fath’s first big swim. Three years earlier, he plunged into Switzerland’s Lake Toma. It marks the starting point of the Rhine River. At 1,231 kilometers (765 miles), the Rhine is somewhat longer than the Tennessee. It’s also international. Its water flows through Switzerland, Germany and the Netherlands. It also hugs parts of the borders of France, Lichtenstein and Austria. Eventually, it empties into the North Sea.

It took Fath 28 days to swim the Rhine’s length. Along the way, his crew took measurements of the water’s temperature and pH. (Measuring pH tells scientists how acidic or alkaline a substance is.) They also recorded weather and the speed of the river’s current. As with the Tennessee, they collected daily water samples. A small plastic device attached to one leg of Fath’s wetsuit sampled the chemical pollutants through which he swam.
That journey, Fath points out, “mixed an adventure story with hard data.”
For instance, Fath and his collaborators screened for more than 600 different chemicals in the collected water samples. To do this they used a variety of tools. Mass spectrometry (Speck-TRAH-meh-tree), for instance, bombards a sample with electrons. (Electrons are negatively charged particles.) The resulting particle soup can reveal what chemicals were in the sample. The scientists also used liquid chromatography (KRO-muh-TAH-gruh-fee). This tool identifies the parts of a mixture by how they interact with other chemicals.
The team described their Rhine data at a meeting of water scientists in November 2014. Their analyses had turned up many different insoluble materials (ones that won’t dissolve in water). How much of each pollutant is present gives clues about the people who live…
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