| Nitrate Pollution |  |
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One
of the major nonpoint source pollutants in Illinois, as in other parts
of the Midwest, is nitrate-nitrogen. Concentrations of this chemical in
drinking water supplies for several Illinois communities periodically
exceed the Federal drinking water standard of 10 mg-N/L. This standard
is based on the prevention of methemoglobinemia or blue baby syndrome, a
condition in which nitrate interferes with the transport of oxygen in
babies. However, more recent research would seem to indicate that
nitrate has other deleterious effects on humans and the environment. One
study conducted in 1997 reported that nitrate levels in excess
of 4 mg-N/L were found to be highly correlated with increased risk of
non-Hodgkins lymphoma in rural areas. Another study, which was reported
in 1993, found
that nitrosoatrazine, a compound that can be formed from metabolic
conversion of nitrate and atrazine, a much used herbicide in corn
production, is genotoxic at concentrations as low as 0.01 ppb. High
nitrate levels have also been linked to environmental problems such as
hypoxia in the Gulf of Mexico and Pfiesteria piscimorte in streams and
rivers on the East Coast, but more research is needed to substantiate
these claims. In general, however, the reduction of nitrate levels in
water bodies appears to be a worthwhile and urgent environmental goal.
It is generally believed that the main source of nitrate-nitrogen in water bodies is from agriculture. Recent data obtained from a study in the Upper Embarras River watershed is in line with this belief, and another source has reported nitrate-nitrogen losses of 15 to 41 kg/ha/yr from cropped fields, depending on the management system. In tile drained areas in particular, tiles act as preferential pathways that transfer contaminated water directly to water bodies without this water being subjected to soil processes that attenuate nitrate concentrations . There are some 10 million acres in Illinois that are tiled, representing 35% of the total agricultural land in the state. Most of this acreage is located in the so-called "tile-shed," a 22-county region generally bounded by I-80 on the north, I-70 on the south, I-55 on the west, and the Illinois/Indiana boundary on the east. It is, therefore, not much of a surprise to find that high nitrate concentrations have been found in the drinking water supplies of communities such as Decatur, Georgetown, Danville, and Bloomington.
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