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Nitrate is a molecule that consists of one nitrogen atom and three oxygen atoms. Nitrates from chemical fertilizers or animal manures applied to agricultural land can contaminate waterways, including lakes and stream. Any nitrogen in excess of what is taken up by plants can oxidize as nitrate, which easily passes through the soil and contaminates both surface and groundwater.

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WHAT IS NITRATE?

WHAT IS NITRATE?

Photo by Douglas Gayeton

WHAT IS NITRATE?

Nitrate is an organic compound. It can be harmful for humans if it exceeds 10mg/L. or ten parts per million in drinking water. Nitrate has been detected in both surface water and groundwater across Minnesota. Its presence can indicate runoff or leakage from cropland (72%), atmospheric effects (9%), municipal wastewater (9%), forests (7%), septic systems (2%), urban stormwater (1%), animal feedlots, and landfills.

WHY IS NITRATE HARMFUL?
Exposure to high levels of nitrate leads to methemoglobinemia, a condition caused by lack of oxygen in infants ("blue baby syndrome"). Other symptoms connected to methemoglobinemia include decreases in blood pressure, increased heart rate, headaches, stomach cramps, and vomiting.

Water samples to test for nitrate are taken by MDH staff and collectors from municipalities across Minnesota. They are stored in this walk-in fridge at a carefully maintained temperature (between 2-6 degree C) to minimize any potential chemical or biological breakdown of the analyte (the stuff in the bottles).

ELEVATED NITRATE LEVELS HAVE BEEN DETECTED IN BOTH SURFACE AND GROUNDWATER ACROSS MINNESOTA. WHILE IT’S DIFFICULT TO PINPOINT WHERE NITRATE COMES FROM, IT’S NOT DIFFICULT TO MEASURE ONCE IT’S THERE.
In 1974, the Safe Drinking Water Act established maximum contaminant levels for physical, chemical, biological or radiological contaminants found in water. The MCL for nitrate, for example, is 10 mg/L or 10 parts per million. Such elevated nitrate levels may harm fish and aquatic life, and because nitrate moves primarily through groundwater (and not surface runoff), it can also pollute drinking water wells. Nitrate leaving Minnesota via the Mississippi River contributes to the oxygen-depleted dead zone in the Gulf of Mexico.

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