Water quality under assault
By Robyn Sanders
A Baylor study has shown that drought conditions worsen the toxicity of chemicals in streams and could prove harmful to aquatic life.
“Texas is special in a lot of ways, one of which being that we have periods where we have too much water, and then periods where we have not enough,” Dr. Ryan King, associate professor of biology, said. “Understanding how these extremes ultimately affect our ability to manage aquatic resources was the reason for looking into this.”
The study was conducted by King; Dr. Ted Valenti, a former Ph.D. student at Baylor and graduate of Baylor’s Institute of Ecological Earth Environmental Sciences program; Dr. Bryan Brooks, professor of environmental science and biomedical studies and director of the environmental health science program; and Jason Taylor and Jeff Back, both Baylor doctoral students.
The study appeared this month in the online journal Integrated Environmental Assessment, a publication by the Society of Environmental Toxicology and Chemistry.
King said he and Brooks received a grant from the U.S. Environmental Protection Agency to study how nutrients affect aquatic life in Central Texas streams and to determine whether nutrient pollution was at levels capable of causing death among aquatic organisms. One of the other aspects of the study, King said, was looking at how flood and drought conditions would interact with the nutrients.
“During drought conditions, when there’s very little flow in the streams and the water gets very warm and there’s a lot of sun hitting it, you get these really big changes in pH during the course of the day,” King said. “pH is a basic water chemistry parameter and it controls the toxicity of a lot of chemicals.”
Valenti said the two summers during which the research was conducted displayed two very different climate conditions; the summer of 2006 was a record drought year at the time (until 2011), and the summer of 2007 was a record rainfall year.
“We had these two extremes,” Valenti said. “What this allowed us was kind of just a snapshot of maybe some worst-case scenarios.”
The researchers sampled 23 Central Texas streams in the course of the study. King said data was collected through instruments placed in the water for a period of 48 hours that would take a water chemistry measurement every 15 minutes.
“In a nutshell, Ted [Valenti] showed, using our data, that nutrients and drought can combine to create really toxic conditions in streams,” King said.
Valenti said the researchers saw many more fluctuations in pH during the drought year.
“One of the things we weren’t really anticipating was how variable pH was at a given site over the course of a day,” Valenti said.
Another aspect of the study was the possible impact of pharmaceuticals from wastewater treatment plants entering the water.
“There’s the potential to have a worst-case scenario in terms of exposure to pharmaceuticals,” Valenti said, “and one of the things we’re trying to say is, in addition to thinking about the overall load — the actual concentration of particular pharmaceuticals — you may want to start thinking about some of these site-specific water quality parameters.”
King said that during seasons of little rainfall, much of what is flowing in streams is treated water from wastewater treatment plants.
“They’re discharging treated water back into a stream, which normally is a small amount of the real flow,” King said, “but when it hasn’t rained for three months, the streams almost go dry, and the only thing that’s flowing is this effluent, which has a lot of other chemicals mixed in with it, including things like pharmaceuticals that we pass through our bodies.”
Some of the changes that may need to be made, King said, involve releasing less treated wastewater to account for drought conditions.
“The implication of this is that when you have a drought, then you’re going to have higher fractions of the water column being wastewater,” King said. “Essentially the idea is that risk assessment needs to account for natural fluctuations in the environment and not just assume that it’s going to be constant like it is when it leaves the pipe at the wastewater treatment plant.”
Brooks said the researchers were able to see the importance of changes in climate from the information they gathered.
“What it suggests is that we need to be more cognizant of subtle influences of climatic changes on water quality,” Brooks said.