Macros and Multivariate Analysis Help Researchers Keep Tabs on Florida Water Quality
It’s summer and maybe you’re traveling to Florida’s coast for a beach vacation (or just wishing you were, like I am)! I got the chance to talk to Dr. Henry Briceño from the Southeast Environmental Research Center (SERC) about how he and his team use statistics to monitor Florida’s water quality.
The center’s research projects throughout South Florida have provided a basis for management decisions for sustaining these fragile resources. Combining data from all of the center’s projects gave the researchers an opportunity to develop a unique, high-level view of conditions throughout South Florida waterways—but joining and analyzing 20 years worth of water quality data collected from hundreds of water monitoring stations was a major challenge.
Several water quality parameters, such as contaminant concentration and temperature, were measured in order to help researchers analyze pollution levels over time. Some of these observations were found to be “nondetects”—meaning the contaminants in these samples fell below the reporting limits of the measurement instruments.
Nondetects are important to consider because even low-level contaminants can prove to be an integral part of the data as a whole. This posed a challenge for the researchers, because it wasn’t clear how to account for nondetects using standard statistical procedures, particularly given the huge quantity of data involved.
SERC enlisted the help of Dr. Dennis Helsel from Practical Stats, who specializes in statistics for data with low-level contaminants. He adapted Minitab’s censored data techniques to write macros that helped to account for SERC’s nondetectable data.
From here, Dr. Briceño and his team easily used Dr. Helsel’s macros and Minitab to analyze the water quality at each monitoring station. Using Minitab Multivariate Analysis tools, SERC grouped monitoring stations into different “water types” and made detailed maps of their geographical distribution. SERC researchers were then able to formulate innovative methodologies to derive protective nutrient criteria for each individual water body.
Dr. Briceño says this project has shown that South Florida water quality is excellent, and that’s great news for this summer’s visitors to the Florida coast!
You can read more about Florida’s water quality in Minitab Case Studies and Testimonials.