Measuring radium isotope levels of ocean water may sound like a daunting task for some, but not for a USF St. Petersburg geology professor and three students.
Undergraduate Alanna Lecher, graduate students Erik Oij and Leslie Wallace, and professor Jim Krest were aboard a research vessel with six other researchers from the University of Southern Mississippi and the Dauphin Island Sea Lab. They set out to study the mixing zones where the Mississippi and Atchafalaya Rivers enter the Gulf of Mexico from the Louisiana coastline.
The research team left Louisiana on May 1 for the eight-day research trip, setting up stations in different areas of the Gulf to take water and sediment samples.
Krest said knowing what happens to the river water when it enters the Gulf can be very important to the local fisheries.
“The phosphate and nitrate which come down the river are great in small doses, and probably actually drive the highly productive fisheries. However, if there is too much of these chemicals, perhaps from fertilizers, it can lead to a process called eutrophication, where the oxygen in the water gets used up, and which can lead to fish kills,” Krest said.
About every summer, he said, this process occurs in an area called the Mississippi Dead Zone.
“It’s important to understand how it is caused, how much is natural, and how much is caused by humans. Eventually our work will lead towards answering some of these questions, but right now we’re focusing on the basic, underlying mixing processes,” Krest said.
In each water sample, he looked at radium isotope levels, because radium can easily be measured in river water and groundwater.
“Their (radium) concentrations are much higher in these source waters, and I can use their radioactive decay to watch how they mix with the offshore waters from the Gulf of Mexico,” Krest said. “Using some simple models, we can estimate how fast the river water moves and gets mixed in.”
The team is also interested in studying the amount of chemicals released from the underlying groundwater and the continental shelf from the deep water of the Gulf. They will also look at how much wastewater comes from the petroleum industry.
“Pumping wells also brings up large volumes of water from deep in the sediments, called production water,” Krest said. “The production water typically has very high concentrations of lots of chemicals. This water is required to be pumped back, deep into the ground, but we are curious as to whether it comes back up anywhere, and therefore if it contributes to the amount of chemicals in the coastal waters.”
Lecher, a junior majoring in environmental science, said her days during the trip began early.
“We usually got up around 6 o’clock, and then we did about six stations a day where we pulled samples at, and then we usually went to bed between midnight and 1 a.m.,” Lecher said.
At different stations, Lecher and the other students used pumps to gather water samples in large barrels. They ran these samples across a machine that measured the radium levels.
To collect sediment samples, the team dropped a sediment collecting device called a box corer into the water.
“It’s this big metal contraption that has lead weights on it, so it pushes down to the sediment and then the bottom closes,” Lecher said. “Then you can bring up this large piece of sediment that we can test for radium.”
Between taking samples, Lecher posted blog entries on http://mag-mix.blogspot.com. The site allowed elementary school students to keep in touch with the team as they made their journey.
“We had a daily blog where we talked about what we were doing that day, where we were, what kind of samples we were collecting that day,” Lecher said. “The schools were able to communicate back to us and kind of go through the entire trip with us.”
This was the first of three trips to the Gulf.
Lecher said the same researchers will go back to the Gulf in November and again in July 2009 to look at the mixing zones during different times of the year.
Krest, however, was able to make some inferences from the first set of samples collected.
“At every station we measured temperature, salinity and oxygen through the water column, and one thing we noticed is that there is a very strong stratification between the surface water and the deep water,” he said. “Essentially, the deep water is cut off from the surface water, and very little mixing is occurring. We feel pretty strongly that this stratification will lead to very low oxygen concentrations in the bottom water of the shelf – and therefore, a very large dead zone this summer.”
Although the days were long and the crew battled with severe weather, Lecher said the overall experience was nice.
“It’s related to what I want to do as a career. It was a good experience and I’m definitely looking forward to the next two,” Lecher said.
Krest said this research will help other studies related to the formation of the dead zone and also aid in the management of the fertilizers and contaminants in the rivers before they reach the Gulf.
“These trips are really exhausting, but they are energizing at the same time. Being able to focus on the science for 24 hours a day and working alongside other people who are focused on related projects really brings the science to life,” Krest said. “I expect that a lot of my experiences will make their way back into my lectures, and this will bring some new energy to that part of my life as well.”