Nitrate (NO3) and Nitrite (NO2)Status and TrendsNitrite plus nitrate (NO23) is determined in an analysis separate from NO2 and NO3. NO23 is analyzed at all 54 stations of the non-tidal network whereas NO2 and NO3 are determined only at stations 13-49 (inclusive). NO23 represents the combined concentration of oxidized nitrogen compounds in the sample and TKN represents the sum of all reduced compounds of nitrogen. The sum of these two concentration values is how total nitrogen is, presently, determined at non-tidal Core/Trend stations. |
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Median NO23 concentration ranged from 0.41 mg/L on Town Creek to 4.51 mg/L on Antietam Creek at Poffenberger Road. NO23 was most concentrated at stations in agricultural and urban regions of the state. Streams having highest median concentration were 30% of all stations. Stations with the lowest median NO23 concentrations were predominantly in western Maryland. These represented 33% of all stations. Decreasing trends in concentration were observed at 56% of stations and the single station on the Choptank River had an increasing trend. NO23 correlated positively with TKN at Braddock Run and the lowest station on the Patuxent. TKN and NO23 were inversely correlated at Deer Creek, the upper and lower stations on the Gunpowder River, in Jones Falls, all three stations on the Patapsco, Whites Ferry on the Potomac and the upper two stations on the Patuxent. A common source for the two forms of nitrogen is suggested when they act in concert (positively correlated) and the opposite is implied when they move in opposite directions as the do in the latter group of stations. Nitrate data for sampled locations are summarized in these plots. |
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