The pollution of the hydrosphere and the atmosphere by compounds of nitrogen is a serious problem that is a population-increase driven component of global change.  Effluents from modern farming practices including row-cultivated fields and food-animal production facilities along with industrial wastes, domestic sewage, and storm sewer runoff from urbanized areas has resulted in elevated nitrate concentrations in surface-
and groundwaters on the North Carolina Coastal Plain.  Of particular concern are the rapidly expanding industrial size swine production facilities with 6000-10,000 animals per farm.  Showers et al. (1990) measured the isotopic signal from different point and nonpoint sources in the Neuse River basin.  Fertilizers fell near the 0 per mil range,
nonpoint source runoff from cultivated fields fell in the +6 to +9 per mil range, and MSTP effluent fell in the +11 to +14 per mil range.  Recent measurements from industrial farms in the Neuse and Cape Fear River basin show that animal waste lagoon nitrogen is significantly enriched in 15N.  Swine lagoon nitrogen falls in the +16 to +19 per mil range, dairy lagoon nitrogen is +20 to +23 per mil, and poultry lagoon nitrogen is +27 per mil. Ammonia volatilization concentrates 15N in these animal waste lagoon
systems.  Nitrate contamination of groundwater in other states is almost synonymous with highly productive row-crop agriculture (Komor et al., 1966) and leaky septic tanks in rural areas not serviced by municipal sewage systems (Aravena et al., 1993).  The 15N composition of contaminated groundwaters in Sampson County, NC which has one of the highest concentration of animal production facilities in the state shows that the
groundwater in the Keener area has elevated nitrate levels associated with fertilizer nitrate, septic nitrate and waste lagoon nitrate.  These groundwater results indicate that unlike other states, multiple sources of nitrogen contaminate groundwaters in the North Carolina Coastal Plain, and suggest that the greatest impact of open waste lagoon systems may be to atmospheric transport with wet and dry deposition.

In North Carolina, public awareness has recently been focused on the potential for eutrophication of the lower portions of the Neuse, Cape Fear and Tar-Pamlico river basins and the Albemarle and Pamlico Sounds. Greatest concern has been directed toward the consequences of run-off from livestock operations, municipal sewage treatment system failures and sedimentation from construction in the rapidly expanding urban areas in the upper portions of these river basins.  The potential severity of the
situation was emphasized by the catastrophic failure of several hog waste lagoons in 1995 and the subsequent fish-kills in near-by waterways.  While run-off controls are being addressed by various state, federal and university groups, awareness has been building of the potential significance of the role of atmospheric deposition in the eutrophication
process.  Central to this awareness is the role of ammonia (NH3).  Ammonia comprises more than 40% of the total N emissions in North Carolina.  While emissions of nitrogen oxides (NOx), mainly from large boilers (classed as point sources) and vehicle traffic, tend to be spread over the urban areas of the Piedmont from Raleigh to Charlotte, NH3 emissions are almost exclusively associated with agricultural activities, particularly intensive livestock operations in the eastern coastal plain.  The environmental
consequences of this large nitrogen source in Eastern North Carolina, and the role atmosphere plays as a vector in the transport, transformation and deposition of nitrogen compounds to the sensitive ecosystems will be addressed.

 Both surface and subsurface drainage water from all land contains some nutrients.  These nutrients are necessary for life in surface waters and only become a problem when they are present in excessive amounts.  The nutrients which are responsible for most water quality problems are nitrogen and phosphorus in surface water and nitrate-nitrogen in ground water.  North Carolina soils were originally low in both nitrogen and phosphorus so these nutrients had to be added to soils to grow a good field crop or lawn.
The addition of these nutrients to soils for increased plant growth increases their concentration in the water which drains from the land and increases the nitrate concentration in the shallow groundwater below most fields.

 The efficiency of crop utilization of nitrogen fertilizers by most crops is 50 to 60% - that is, a little over half of the fertilizer nitrogen added to crops is ultimately harvested with the crop.  The remaining nitrogen fertilizer generally moves with the water to the shallow ground water.  Thus the nitrate-nitrogen concentration in the shallow groundwater below most agricultural fields fertilized according to agronomic recommendations is 10 to 20 milligrams per liter. The only way to prevent this nitrogen from ultimately reaching surface waters and causing problems is for the water to
travel through saturated soils containing organic matter (controlled drainage, riparian buffers, etc.)  All productive agricultural systems have a tendency to be leaky with regard to nitrogen even when all best management practices are followed in the field.

 When phosphorus is added to soils as fertilizers, it reacts with the soil and does not move readily with percolating water.  Thus nearly all phosphorus lost to surface waters is lost via surface runoff.  This usually is a problem only when sediment losses from fertilized areas are high or large amounts of phosphorus are added to soils so that surface runoff water contains more dissolved phosphorus.  It is much easier to contain phosphorus in a field than it is nitrogen although smaller amounts of phosphorus are
required to cause surface water quality problems.

The first step in developing any nitrogen management plan is to determine the
amount of nitrogen that the water body of interest can assimilate or accept and maintain the water quality standards and uses to be made of that water.  The estuarine water quality model that is discussed by other researchers will help DWQ better estimate this allowable nitrogen loading for the Neuse River estuary.

Once the allowable nitrogen loading is estimated, the load must be divided among the various sources of nitrogen in the basin.  Good estimates of nitrogen load must be estimated from the various point sources, agricultural activities, urban areas, forested areas and atmosphere. Point source nitrogen can be quantified easily since individual wastewater treatment plants collect data on their effluent.  Nonpoint source loading is much more difficult to quantify, and data from a few studies must often be used to estimate nonpoint source loads throughout the basin.  Better data on land use and management practices as well as atmospheric sources and estimated loads from each category are needed to identify the largest nitrogen sources in the basin.

Finally, many of the nitrogen sources are located miles upstream of the estuary.  Much of the nitrogen may be lost as it is transported to the surface water and subsequently downstream.  Nitrogen fate and transport models are needed to quantify this nitrogen loss.  An understanding of the fate and transport processes will enable the Division to identify more cost-effective solutions for controlling nitrogen in the basin.

While there is much research that is ongoing in many of these categories, it will probably be years before all needed data are available.  Therefore, DWQ will make the best decisions it can with available data, continue to review ongoing research, and perform follow-up monitoring to determine if the nitrogen management strategies need to modified in any way.

In the spring of 1997 the North Carolina Department of Environment and Natural Resources together with the Water Resources Research Institute funded an interdisciplinary group of 14 scientists from around the state to (1) develop a MODel that can be used by state regulators to help make water quality decisions in the Neuse River Estuary and (2) support this model with a coordinated MONitoring effort.   Part of the modeling effort utilizes the CEQUAL-W2 water quality/circulation model which has been set up and preliminary runs completed using best available historical data for the Neuse.  A second part of the modeling effort is to develop a decision support framework for the Neuse.  The monitoring component includes collecting water quality, chemical, sediment, circulation, and fisheries data in the system.  I will outline the MODMON project in further detail and present a current status report for the project.  Ongoing progress can be accessed from the MODMON home page at http://www.marine.unc.edu/neuse/modmon/