Pollution Researchers Follow the Coffee : Ecology: Caffeine, it turns out, is an excellent tracer of waste movement.

There’s a good new way to track the flow of domestic waste into the nation’s streams and rivers, scientists say: Follow the coffee trail.

It turns out caffeine does more than keep the scientists awake. The ingredient found in coffee, tea and cola is an excellent tracer of waste movement.

And while discovering the new research tool, scientists uncovered both good news and a surprise, said Larry B. Barber II, a U.S. Geological Survey researcher.

The good news: Water quality in the Mississippi River is improving.

The surprise: Pollution is more concentrated in the upper part of the river than the lower reaches.

Barber said the team of scientists was trying to track the movement of chemicals along the river and needed a way to sort the domestic waste from industrial, farm and other chemicals.

When they tested water near cities, caffeine kept turning up, and “that turned the light bulb on that here is an important chemical,” he said.

Since caffeine moves through people and water treatment systems relatively unchanged, the chemical compound became the scientists’ tracer for urban waste.

By comparing how much caffeine is present with the amounts of particular chemicals that occur both in domestic and industrial waste, they were able to calculate what share of the pollution in an area came from domestic sources and what share was industrial or farm-related.

Knowing that will allow researchers to see if there are changes in these ratios in the future, which would indicate if anti-pollution projects are working.

Caffeine showed up in high concentrations near the Minneapolis-St. Paul area in Minnesota, around the confluence of the Illinois River carrying the flow from Chicago, and near cities such as St. Louis.

The water experts analyzed 450 samples of Mississippi River water collected in 1991 and 1992, seeking to measure the amounts of pollution in the river and its patterns of change over the seasons.

Barber said the team is going back this summer to take samples of river bed sediments. They want to compare the chemicals in the sediments now with those they found in 1992, to see what effect last summer’s floods had.

In the earlier river water studies, they found 32 different organic compounds in the river, with at least some of the pollutants turning up in about one-quarter of the water samples.

But significant concentrations were found in only three areas: below the Minneapolis-St. Paul area; below the confluence of the Ohio and Mississippi at Cairo, Ill.; and between New Orleans and Baton Rouge, La.

Barber said none of the chemicals detected was concentrated enough to be hazardous.

Most of the chemicals found in the river are byproducts of waste water discharge by cities, urban runoff, power plant cooling water discharge, pulp mill waste, feed lot runoff, river traffic, refueling spills and industrial discharge.

“Frequently, it’s thought that water quality decreases as you move down river, and there is some truth to that, but there is so much more water that chemical concentrations are very low,” Barber said.

“People think New Orleans’ water quality is low because of all the waste from up above, but the most susceptible part of river seemed to be above St. Louis, where it’s a relatively small river,” Barber said. “It’s no cliche that dilution is the solution.”

In addition to natural processes, improved waste water treatment and reductions in discharges into the river are helping improve water quality.

“If we look back to records of the 1800s and even 1920s and 1950s, our general conclusion is that the water quality of the Mississippi is much better today than it was 20 or 50 years ago,” Barber said.