Filters: Tags: nitrate isotopes (X)
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Coupled measurements of nitrate (NO3 −), nitrogen (N), and oxygen (O) isotopic composition (δ 15NNO3 and δ 18ONO3) were made in surface waters of Monterey Bay to investigate multiple N cycling processes occurring within surface waters. Profiles collected throughout the year at three sites exhibit a wide range of values, suggesting simultaneous and variable influence of both phytoplankton NO3 − assimilation and nitrification within the euphotic zone. Specifically, increases in δ 18ONO3 were consistently greater than those in δ 15NNO3. A coupled isotope steady state box model was used to estimate the amount of NO3 − supplied by nitrification in surface waters relative to that supplied from deeper water. The model...
The sources of nitrate (NO3−) in groundwater of the shallow karst aquifer in southwestern Illinois' sinkhole plain were investigated using chemical and isotopic techniques. The groundwater in this aquifer is an important source of potable water for about half of the residents of the sinkhole plain area. Previous work has shown that groundwater from approximately 18% of the wells in the sinkhole plain has NO3− concentrations in excess of the USEPA's drinking water standard of 10 mg N/l. Relative to background levels, the NO3− concentrations in water from 52% of the wells, and probably all of the springs in the study area, are anomalously high, suggesting that sources other than naturally occurring soil organic matter...
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Fertilizers,
Groundwater,
Groundwater chemistry,
Karst springs,
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