Groundwater in the Floridan Aquifer is the source for more than 1,000 springs in North and Central Florida. It also provides water for over 90 percent of the people who live there. Even though this water lies hundreds of feet below the ground, it is not entirely protected from sources of pollution at the surface. Nitrate-nitrogen is one pollutant that has contaminated much of the water in the Floridan Aquifer. Nitrates are nutrients necessary for plant growth; however, when water with elevated levels of nitrate-nitrogen flows out of the aquifer into our springs it is harmful to their environmental health. Elevated groundwater nitrate concentrations can cause algal blooms, which may lead to a lack of oxygen, negatively affecting fish and other aquatic creatures.
Nitrates in drinking water also have negative health impacts on humans. The EPA has mandated that public water supplies must maintain nitrate levels below 10 milligrams per liter (mg/L). Drinking water with nitrate levels above 10 mg/L can reduce the oxygen carrying capacity of blood, causing methemoglobinemia, or blue baby syndrome, which is harmful or fatal for young children and the elderly.
Epidemiological research conducted by the National Cancer Institute has provided strong evidence that drinking water with elevated nitrate levels is associated with increased risk of certain cancers and birth defects, even at concentrations much lower than 10 mg/L. Nitrites, created from nitrates, react in the stomach to form what are called N-nitroso compounds. These compounds are the main carcinogen in cigarettes and they have been shown to cause multiple forms of cancer in every animal species tested.
We know that nitrate levels are rising in our springs. The Florida Department of Environmental Protection has set 0.35 mg/L as the numeric nutrient limit for healthy springs. About 80% of Florida’s springs exceed this standard and are considered by the State to be impaired. But what about nitrates in our drinking water?
The Howard T. Odum Florida Springs Institute has tested samples of drinking water from 23 cities in North Florida. Two rounds of testing were performed, one in 2016 and one in 2018. During each of these sampling events, FSI compared tap water and bottled Florida spring water. The average of the results from these tests are shown in the following figures.
BOTTLED FLORIDA SPRING WATER NITRATE ANALYSIS- MARCH 2016 TO AUGUST 2018 (average of 1 to 3 samples)
NORTH CENTRAL FLORIDA DRINKING WATER NITRATE ANALYSIS- MARCH 2016 TO AUGUST 2018 (average of 1 to 3 samples)
All of the bottled spring water tested was above the springs nitrate standard of 0.35 mg/L. Municipal drinking water scored better overall than bottled spring water. Many people buy bottled spring water because they feel it is a safer and cleaner alternative to tap water. However, regarding nitrates, this is not the case.
Factors that contribute to the nitrate contamination of groundwater are the amount and type of nitrogen sources in the area and the vulnerability of the underlying aquifer. Fertilizers (urban and agricultural), intensive livestock operations, and septic tanks are significant sources of nitrate-nitrogen contaminating the Floridan Aquifer.
In places where the aquifer is ‘protected’ by a thick layer of less permeable clay or rock, contamination from nitrates is less. The map below shows confined and unconfined areas of the Floridan aquifer. Most of the west side of north and central Florida, the area where these samples were collected, lies on the unconfined aquifer. Cities like Bronson (2.87 mg/L) and Chiefland (1.45 mg/L), located in the heavily farmed areas near the Suwannee River tended to have higher nitrates than cities to the east, where the aquifer is less vulnerable.
Some municipalities, like the city of Gainesville (nitrate-nitrogen <0.05 mg/L), get their water from deep wells that are protected by the clayey Hawthorn Formation and are less likely to contain surface contaminants. Other wells, such as those at Newberry’s water treatment plant, are less protected by impervious soils and are shallower. This vulnerability and surrounding agricultural land uses contribute to Newberry’s elevated nitrate concentration of 1.82 mg/L.
We need to act now to protect our springs and our health. Reducing the amount of nitrogen fertilizer and wastewater we put on the ground is the most cost-effective way of decreasing aquifer pollution. Whether you are a fan of healthy springs or healthy people you should insist on strict enforcement of laws that are intended to prevent this pollution of the Floridan Aquifer. What will happen to Florida’s economy and quality of life if no one wants to visit our springs or drink our water?
ALL WATER SAMPLES WERE ANALYZED AND VERIFIED BY AN INDEPENDENT LABORATORY. ALL SAMPLES WERE PURCHASED OR COLLECTED IN THE FOLLOWING FLORIDA COUNTIES: ALACHUA, COLUMBIA, DIXIE, GILCHRIST, LAFAYETTE, LEVY, AND MARION. TO THE BEST OF OUR KNOWLEDGE, ALL INFORMATION CONTAINED HEREIN IS TRUE AND ACCURATE.