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In-stream monitor measures dissolved nitrate flowing into estuary

An in-stream monitor provided data WED scientists can use to estimating the load of dissolved nitrate that water carries into Oregonís Yaquina Bay from surrounding land. The instrument furnished hourly data, collected over an 18-month period, on the concentration of dissolved nitrate nitrogen in the Yaquina River. Besides providing data to calculate the annual budget of dissolved nitrogen flowing into the Yaquina estuary, the data indicate that the highest values occur during high river flows of winter whereas the lowest values occur during low flows of late summer. In late summer co-variations in values for nitrate, specific conductance, temperature, and alkalinity suggest that part of the nitrate may be coming from downstream sources; however, during winter, data indicate that the surrounding watershed is the nitrate source. WED scientists also measure nitrite, ammonia, phosphate and silica, in the riverís water, but not with the in-stream instrument. (Contact A.C. Sigleo, 541-867-5022; sigleo.anne@epa.gov)

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