A recent article in WaterWorld describes how nitrates found in groundwater may take decades to get filtered out.  USGS researchers discovered that groundwater nitrate levels were above expected levels, despite the reduction of nitrogen-based fertilizer in the areas tested.

“In this study, USGS scientists closely examined surface and ground waters at seven study sites from across the nation to determine the portion of stream nitrate derived from groundwater… The slow release of groundwater nitrate to streams may also affect the water quality of large rivers. For example, increases in nitrate concentrations during low and moderate flows in large rivers in the Mississippi River Basin have been observed to be greater than or comparable to increases in nitrate concentrations during high flows.”

Nitrate is a naturally occurring form of nitrogen found in soil. It is also often found in fertilizer, since most crop plants require high levels of nitrates to produce high yields. Issues can arise when water runoff carries excess nitrates from agricultural and urban sources Continue reading →