Nitrogen In The Rocky River: Early Summer 2014
John Fountain, Adam Lee, Megan Howard, Jason McCray and Chanelle McArthur; Department
of Marine Earth and Atmospheric Sciences, North Carolina State University.
Abstract
The objective of this project was to determine the major sources of nitrogen in the Rocky River
and their relative magnitudes. Our research group collected over 100 water samples from the
Rocky River and its major tributaries between May 23, 2014 and July 22, 2014 and had them
analyzed for total nitrogen and inorganic nitrogen (nitrate+nitrite). The dissolved organic
nitrogen in selected samples was also characterized by our group members to help determine its
source. Historical analyses from NC DENR and from a former group member, James Rudder,
were compiled and compared to our data. All our samples, with the exception of the last day of
sampling, were obtained at times of very low flow in the Rocky River and its tributaries. During
the low (base flow) conditions, the Rocky River above Highway 64 at Siler City and all major
tributaries except Loves Creek, had low abundances of total nitrogen (less than 2 ppm). High
concentrations of total nitrogen and inorganic nitrogen from the Siler City Waste Water
Treatment Plant (more than 10 ppm) produced high concentrations in Loves Creek and in the
Rocky River below its confluence with Loves Creek. The concentration of nitrogen in the Rocky
River decreases steadily downstream from Loves Creek persumably due to dilution. These data
show that the Siler City Waste Water Treatment Plant is the only major nitrogen source in the
Rocky River Drainage Basin during times of base flow. The last day we sampled, July 22,
2014, followed a period of significant rain and had much higher flow rates (discharge). The
data from this single event show that during high flow following precipitation, both total
nitrogen and organic nitrogen concentrations increased by a factor or more than 3. Organic
nitrogen concentrations were elevated in mulitple tributaries. These data suggest that event flow
may introduce large amounts of organic nitrogen into the watershed and that the sources are
widespread nonpoint sources.
BACKGROUND
In the summer of 2014 a group of North Carolins State and Wake Tech
Community College students working under the direction of John Fountain, of NC
State’s Marine Earth and Atmospheric Sciences Department, undertook
continuation of a project that a former student, James Rudder had begun. Rudder
and Fountain had been studying water quality in the Rocky River and had decided,
based upon analytical data, that nitrogen was the contaminant of particular concern
(sediment is also an issue but the science behind sources and control of sediment
are fairly well known). The students undertook strategic sampling of the Rocky
River and its tributaries with the objective of determining the major sources of
nitrogen and their magnitudes. The project began in late May of 2014 and ended
on July 20, 2014.
Historical Data:
Data on the concentrations of inorganic nitrogen (nitrate and nitrite) on the Rocky River at US
64, at Rives Chapel Church Road and at NC 902 are available from the North Carolina
Department of the Environment and Natural Resources (NC DENR). In addition, James Rudder
obtained samples at the same locations in a prior phase of this study. Figure 1 shows these
sample locations and Figure 2 shows the historic inorganic nitrogen data.
Figure 1: Sampling Locations along the Rocky River
Inorganic Nitrogen Below Lower Reservoir
Pilgrims Pride
Poulty shuts
down on May
24, 2008.
40
35
Inorganic Nitrogen mg/L
30
Townsend
Farms shuts
down on
October 4,
2011
25
20
15
10
5
0
9/1/2002
1/14/2004 5/28/2005 10/10/2006 2/22/2008
7/6/2009 11/18/2010 4/1/2012
DENR US 64
DENR Rives Chp Ch Rd.
DENR NC 902
Jim Rudder US 64
JRUD Rives Chp Ch Rd
JRUD NC 902
Figure 2: Historical Inorganic Nitrogen Data.
8/14/2013
Analyses of samples taken at US 64, which is below the Siler City Reservoirs, show that
inorganic nitrogen concentrations have been low in all samples, at least since 2004.
In contrast, data from samples taken at the next sampling point downstream, at Rives Chapel
Church Road have shown elevated levels of nitrogen at least since 2000. Nitrogen
concentrations at this site remained high through 2008 and then decreased at the time the
Pilgrim’s Pride processing plant shut down. Nitrogen concentrations then decreased again in
2011 at the time Townsend’s plant closed. Since late October 2011, nitrogen concentrations
have remained below 5 ppm at the Rives Chapel Church Road site. Nitrogen concentrations at
the next site downriver, at highway 902, showed the same concentration trends found at Rives
Chapel Church Road, but were always lower, presumably due to dilution. These data indicate
the historically there has been very little nitrogen transported to the lower Rocky River (below
the reservoirs) from the upper Rocky River and by inference, that the Siler City Waste Water
Treatment Plant, which empties into Loves Creek, which joins the Rocky River below US64 and
above Rives Chapel Church Road, was the primary source of nitrogen in the lower Rocky River.
Sampling Strategy For This Project
Our study began with sampling of each major tributary in the upper Rocky River drainage area
and multiple locations along the upper Rocky River and the North Prong (Figure 3).
Figure 3: Upper Rocky River Sample Sites
In this phase, and throughout the project, we sampled each location at least twice (on two
different days). If duplicate samples showed similar nitrogen concentrations, and the
concentrations were low, future sampling was concentrated on other sites.
The same strategy was then employed in the lower Rocky (below the Siler City reservoirs), each
large tributary was sampled at least twice, and when nitrogen concentrations were low for both
analyses, additional sampling was concentrated elsewhere.
Once detailed sampling of tributaries was completed, each subsequent round of sampling
included a series of sampling points in the Rocky River below the reservoirs (Figure 4). In each
sampling round, all samples were taken on the same day, and over a period of 5 hours or less. In
no case did discharge change significantly over the sampling period.
Figure 4. Sampling Locations on the Lower Rocky River
Note that the bridge on Rives Chapel Church Road, the first location below the confluence with Loves
Creek where historic samples were taken, was closed during the study, thus we sampled from the bank
just below the bridge, gaining access from Carolina Hill Road.
A subset of samples was selected for analysis of the dissolved organic nitrogen , based on
calculated organic nitrogen content. Total nitrogen includes inorganic nitrogen (nitrate and
nitrite) and organic nitrogen. Organic nitrogen content was determined by subtracting the
amount of inorganic nitrogen from the total nitrogen content.
METHODS
Analyses for total nitrogen and inorganic nitrogen were performed at the Environmental Analysis Testing
Laboratory at N.C. State University using standard methods. Analytical methods, including sampling
methods, are detailed in the appendix. Analyses of dissoved organic matter were performed by our team
members in the laboratory of Dr. Chris Osburn at N.C. State University. Experimental methods are given
in the appendix.
RESULTS
Background for discussion of results
We have separated discussion of inorganic nitrogen (nitrate and nitrite) from organic nitrogen in the study
as they may have very different sources. Nitrogen is a major component of fertalizer, including manure
and sewater sludge. Generally nitrogen is applied in a reduced form (e.g. ammonia NH3) but can be
readily oxidized by bacteria to nitrate (NO3 -). Nitrate is soluble in water and can move downward in the
soil to the water table where it can be carried to a nearby stream by groundwater. Nitrate is also the
primary form of nitrogen produced by the Siler City Waste Water Treatment Plant. In contrast, organic
nitrogen may have mulitple sources including runoff from agricultural fields, erosion from soil on river
banks and channels and production in a water body. The different sources of organic nitrogen can
sometimes be identified by comparing their fluorescence spectra to known samples.
Uppper Rocky River
Figure 5. Total Nitrogen in the upper Rocky River and Tributaries
Above the Upper Siler City Reservoir, the Rocky includes two branches, the Rocky River and the
North Prong of the Rocky River. In addition, Greenbriar Creek comprises a third major contibutor to the
upper reservoir. We sampled three locations on each of these tributaries (Figure 1). Total Nitrogen was
between 1 and 2 mg/L in virtually all samples (Figure 5). There was no trend downstream; the three
stations on the upper Rocky River showed essentially identical results. Similarly the three North Prong
sites showed no significant differences (there was a suggestion of a trend, of less than 0.5 mg/L change,
on 5/23, but it was not present on 5/30). The three locations on Greenbrier Creek were nearly identical
with no trend downstream. Samples from Mud Lick Creek and the edges of the reservoir showed
concentrations similar to all other samples in the Upper Rocky.
Figure 6. Inorganic Nitrogen in the Upper Rocky Drainage Area
Separating inorganic and organic nitrogen does not reveal any trends either (Figures 6 and 7). All organic
analyses were less than 1 mg/L (Figure 7) while inorganic nitrogen was about 1 mg/L in both the Rocky
River and the North Prong (Figure 6).
It is worth noting that duplicate analyses, taken at least a week apart, always agree within 1 mg/L and
analyses along a given stream (Rocky, N. Prong and Greenbrier), also agree within 1 mg/L suggesting the
analyses are representative.
Figure 7. Organic Nitrogen in the Upper Rocky River Drainage Area.
Lower Rocky River
Figures 8,9 and 10 show the results of sampling the same five locations on the lower Rocky
River on four successive sampling rounds over a period of five weeks. The data show a very
consistent pattern. Total nitrogen concentration (Figure 8) was about 1 mg/L at Siler City Snow
Camp Rd (just upstream of US 64), increased to more than 2 mg/L at the next sampling site
downriver (Carolina Hill Rd at Rives Chapel Church Rd) and then decreased progressively
downstream (Highway 902, and Pittsboro Goldston Rd, and Chatham Church Rd.
Inorganic nitrogen (Figure 9) showed identical trends as total nitrogen, less than 1 mg/L at Siler
City Snow Camp Road, over 2 mg/L at Carolina Hill Rd (Rives Chapel Church Rd.) and
decreasing from their downstream. In contrast, organic nitrogen (Figure 10), did not display a
similar trend; organic nitrogen was low (less than 1 mg/L) in all samples on all days, and did not
display a consistent downstream decrease.
Figure 8. Total Nitrogen in the Lower Rocky River. Each set of data shows samples taken on
a single day, beginning with the sample at Siler City Snow Camp Rd, and moving progressively
downstream to Carolina Hill Rd, Hwy 902, Pittsboro Goldston Rd., and Chatham Church Rd.
Figure 9. Inorganic Nitrogen in the Lower Rocky River
Figure 10. Organic Nitrogen in the Lower Rocky River
Lower Rocky Tributaries
Eight tributaries to the lower Rocky River were sampled to assess their contribution to the
nitrogen budget; sample locations are shown in Figure 11. Loves Creek was sampled above and
below the Siler City Waste Water Treatment Plant (WWTP) and at two locations on S. Chatham
Ave. above the point the creek divides into two branches.
The total nitrogen concentrations from the tributary samples are shown on Figure 12. It is
immediately apparent that the concentration in Loves Creek at Progress Blvd., which is
immediately below the WWTP, is far higher than any other tributary. That this is due to effluent
from the WWTP is apparent from the increase in concentration from above the plant (at 2nd St.)
to below the plant (at Progress Blvd.).
The unnamed stream sampled from Loves Creek Church Rd. also showed elevated
concentrations. This very small stream which had total nitrogen concentrations between 4 and 5
mg/L, has a very small drainage area and had virtually no flow. Thus its total contribution of
nitrogen to the Rocky is very small.
Figure11: Lower Rocky River Tributaries Sample Sites.
Figure 12. Total Nitrogen from Lower Rocky Tributaries
Figure 13. Inorganic Nitrogen from Lower Rocky Tributaries
Figure 14. Organic Nitrogen from Lower Rocky Tributaries.
Separating Inorganic and Organic Nitrogen (Figs. 13 and 14) shows that the trends discussed for
total nitrogen are explained almost entirely by inorganic nitrogen. The only significant exception
is for the unnamed creek at Loves Creek Church Rd, which shows a predominance of organic
nitrogen. The fields sloping to this creek have cattle grazing on one side and a number of trailers
that do not appear to be connected to the city sewer on the other side; either of which could be a
source of organic nitrogen; however, as previously mentioned, the flow in this creek is very
small.
Our analyses show more than 1 mg/L of organic nitrogen in Loves Creek below the WWTP,
which is in contrast to Siler City analyses that show their effluent typically has total nitrogen
equal to inorganic nitrogen (data from WWTP weekly analyses reported on their NPDES
reports). The difference could be due either to analytical methods or to in-stream reactions
between the plant and Progress Blvd.
Event Flow
In the last week of our study Chatham County received extensive rain for the first time in our
study period. As a result, the discharge (flow rate) in the Rocky River and its tributaries
increased by more than an order of magnitude. Figure 15 shows the discharge from the United
States Geological Survey’s (USGS) gage station on the upper Rocky River during the study
period. The arrows show the approximate discharge at the time of each of our sampling events.
As the figure shows, the flow was much higher during our last sampling, on July 22, than in
previous events. Flow before the rain event was about 0.5 cubic feet per second; it reached
close to 1000 cubic feet per second at the peak of the storm and was still elevated during our
sampling.
Figure 12: Discharge in the Upper Rocky: Source: USGS
National Water Information System
There are three major sources of water to a river, groundwater, discharge from point sources
(such as waste water treatment plants) and runoff. In dry periods, such as occurred for most of
this study, groundwater and discharge from the Siler City Waste Water Treatment Plant (the
only major point source in the area) are the major sources of water in the Rocky River.
However, after a rain event, water flows relatively quickly to local streams through a variety of
pathways, this flow is termed event flow (the term runoff is often used informally to refer to
event flow, although it may also be for specific pathways in event flow); the magnitude and
timing of event flow depends upon multiple factors including size of the drainage basin, amount
and duration of rainfall and saturation of the ground prior to the event. In the Rocky River
drainage basin, discharge (the rate of flow) rises very rapidly with the start of precipitation, and
drops steeply within a day or two after the rain stops. If there are several rain events close to one
another, it may take several weeks to return to pre-event discharge. This can clearly be seen in
Figure 12.
On August 22, flow in the Rocky and its tributaries was much higher than in previous sampling
events. The results of the analyses from this sampling round were very different from previous
samples. Figure 13 shows that total nitrogen increased to almost 4 mg/L in both the North Prong
of the Rocky and in Greenbrier Creek.
Figure 13. Total Nitrogen in the Upper Rocky River. The purple bars show samples from
August 22, the day with high discharge
Figure 14. Inorganic Nitrogen in the Rocky River, Including August 22, 2014
Figure 15: Organic Nitrogen in the Upper Rocky River, Including August 22, 1014
Figure 14 shows that inorganic nitrogen did not increase significantly on August 22 in the
tributaries on the upper Rocky River while Figure 15 shows that organic nitrogen did increase.
Thus the increase in total nitrogen shown in Figure 13 can be attributed almost entirely to
organic nitrogen.
Figure 16. Total Nitrogen in the Lower Rocky River, Including August 22, 2014
Even larger changes in nitrogen concentration were seen in the lower Rocky River. Figure 16
shows that the consistent patter seen in the previous five weeks of sampling was not repeated on
the 22nd. Total nitrogen coming from the reservoir (measured at Siler City Snow Camp Rd.)
increased to nearly 2 mg/L and concentrations increased downstream with the sample from
Highway 902 exceeding that from Rives Chapel Church Rd (measured from Carolina Hill Rd.).
Figure 17 shows that inorganic nitrogen was much lower than in previous sampling rounds,
essentially showing the normal trends with low concentrations coming from the reservoir,
increase below Loves Creek and then decline downstream from there. This is the pattern that
would be produced by dilution from rainwater; lowered concentrations with similar trends to
those observed during dry conditions.
However Figure 18 shows that organic nitrogen does not show trends consistent with simple
dilution. Organic nitrogen is much higher than in dry conditions and stays high in all samples.
The trends seen in total nitrogen for August 22 are thus explained almost entirely by organic
nitrogen.
Figure 17. Inorganic Nitrogen in the Lower Rocky, Including August 22, 2014
Figure 18. Organic Nitrogen from the Lower Rocky, Including August 22, 2014
Characterization of Organic Nitrogen
Dissolved organic nitrogen sources include runoff from agricultural lands, leaching from
sediments on river banks and production in the stream from algae and other biota. Selected
samples with high ratios of organic to inorganic nitrogen were analyzed to determine possible
sources. The fluorescence emission of samples is measured over a range of frequencies a
technique termed excitation-emission-matrix (EEM) spectroscopy, the resulting EEMs (Figure
19), are compared to potential sources. A statistical approach, commonly parallel factor analysis
(PARAFAC) can be used to help distinguish components. Since the critical samples were
obtained in the last week of this project, PARAFAC modeling has not yet been done. The
tentative conclusions discussed in this section are based on visual comparison of EEMs.
The first conclusion is that the character of the dissolved organic material remained constant
throughout the study, including both high and low flows ( Figure 19). Inspection of the
Figure 19. Three samples of dissolved organic matter from the Rocky River taken on three
different days, and one sample of poultry waste.
Figure shows that the EEM from all samples from the Rocky River are very similar; in contrast,
the sample from poultry waste is very different. The strong emissions between 300 and 375 nm
from the poultry waste is characteristic; swine, horses and presumably other manure sources
typically show this same characteristic. None of the samples we analyzed showed strong
emission in this range, thus our study found no evidence of animal operations of any kind in the
dissolved organic matter spectra.
The pattern typically found in the river samples (Figure 19) is similar to that found in samples
from streams throughout the region and is characteristic of humic fractions leached from
sediments along the river channel. Since we had only one round of sampling at high flow (July
22), and have not done statistical analyses of the data, these conclusions are tentative
CONCLUSIONS
Analyses of samples taken during times of low flow showed that the concentration of nitrogen in
the Rocky River and its tributaries above Siler City was always low (less than 2 mg/L). In
contrast, the concentration of nitrogen, specifically as nitrate, in Loves Creek, below the Siler
City Waste Water Treatment Plant, was always high (average over 10 mg/L) and this resulted in
an elevated nitrogen concentration in the Rocky River below the confluence of Loves Creek with
the Rocky. The concentration of nitrogen in the Rocky River decreased downstream from
Loves Creek, and all downstream tributaries had low concentrations of nitrogen, indicating there
were no other significant sources of nitrogen. Analyses from Loves Creek above and below the
waste water treatment plant indicated the concentration above the plant was always less than 2
mg/L, thus the plant was the primary source. Organic nitrogen was low in both the upper Rocky
and Lower Rocky River samples, thus inorganic nitrogen, as nitrate, is the major contaminant
during low flow.
Analyses of samples from August 22, 2014, when the discharge was much higher than during the
other sampling events, led to very different conclusions. The concentration of inorganic
nitrogen is lower than during low flow events (Figure 17) while the concentration of organic
nitrogen is increased (Figure 18). The source of organic nitrogen is apparently widespread as
elevated concentrations are seen in many tributaries (Figures 14 and 15). No single dominant
source of organic nitrogen was found.
Tables:
Site
Number
Site
5/23/14
5/30/14
Old 421
1
1.58
1.37
Staley Snow Camp (Upper Gauge)
7
1.54
1.52
Ben Smith Rd (N Prng)
Staley Snow Camp (N. Prng)
5
8
1.65
1.61
1.88
1.55
Staley Store Rd (Grnbr. Crk)
3
1.21
0.93
Mud Lick Crk. (R.C. Overman Rd)
12
1.48
1.18
Table 1.1: Total Nitrogen (mg/L)-upper Rocky River, Chatham County, NC
Table 1.1 shows the results of analyses from the Upper Rocky River
for total nitrogen on two different weeks. Note that the values
agree within a few tenths of a mg/L for all sites.
Site
Site
Number
5/23/14
5/30/14
6/06/14
6/13/14
6/27/14
1.23
1.12
1.12
0.9
0.99
2.66
3.08
2.77
1.81
1.82
1.25
1.21
1.39
0.69
0.82
0.73
0.64
Siler City Snow Camp Rd (Rocky
River)
14
Carolina Hill Rd @Reeves Chapel Ch.
21
HWY 902 (Rocky River)
24
1.44
Pittsboro Goldston Rd (Rocky River)
27
1.36
Chatham Church Rd (Rocky River)
31
1.15
White Pines Reserve (Rocky River)
33
1.36
0.64
Table 1.2 : Total Nitrogen (mg/L)-lower Rocky River, Chatham County, NC
Table 1.2 Shows total nitrogen in the Lower Rocky River, the sites are listed from
top to bottom moving downstream from Siler City. Note that 1: concentrations at
each location stayed constant within 1 mg/L, 2: concentrations above Loves Creek
(measured from the Siler City Snow Camp Rd. Bridge) never exceeded 1.23 mg/L and
3: concentrations always decreased downstream below Loves Creek.
Site
Siler City Snow Camp Rd (Rocky
Site
Number
14
5/30/14
5/30/14
6/06/14
6/13/14
6/27/14
0.90
0.78
0.76
0.75
0.63
River)
Carolina Hill Rd (Reeves Rocky River)
21
HWY 902 (Rocky River)
24
0.54
Pittsboro Goldston Rd (Rocky River)
27
0.71
Chatham Church Rd (Rocky River)
31
0.63
White Pines Reserve (Rocky River)
33
0.33
0.56
0.81
0.46
0.42
0.37
0.4
0.38
0.55
0.43
0.56
0.48
0.47
0.46
Table 2.3: Organic Nitrogen (mg/L)-lower Rocky River, Chatham County, NC
Table 2.3 shows that dissolved organic nitrogen was low in every sample, never reaching
1 mg/L. These data show that the major source of nitrogen in the river is inorganic nitrogen.
Site
number
Site
5/23/14
5/30/14
6/6/14
6/13/14
6/27/14
Nick Creek at Jessie Bridges Rd
15
0.69
0.63
Nick Creek at Smith Hudson Rd
16
1.66
1.62
Unnamed at Loves Creek Church Rd
Loves Creek at S. Chat. Ave near
Chestnut St.(above the WWTP)
Loves Creek at S. Chat Av near E
College St., (above the WWTP)
17
4.05
1.04
Loves Creek at S 2nd St (Above WWTP)
18
1.16
1.46
1.54
2.06
1.44
Loves Creek at Progress Blvd (WWTP)
19
11.6
13.2
12.4
9.19
13
Varnell Creek at Stagecoach Rd.
20
1.11
0.96
Meadow Creek at Rives Chapel Rd.
22
Tick Creek at Jim Moody Rd.
23
1.15
0.97
Landrum Creek at Hwy 902
25
1.23
1.14
Harland Creek at Hwy 902
26
0.58
Unnamed Creek at Holly Ridge Rd.
28
0.34
0.38
Unnamed Creek at Pete Roberson Rd.
29
0.24
0.32
Bear Creek at Woody Dam Rd.
30
0.78
0.74
Unnamed Johnny Shaw Rd.
32
0.26
0.39
4.95
0.85
1.48
2.29
1.41
1.77
1.03
Table 3.1: Total Nitrogen (mg/L)-Lower Rocky River tributaries, Chatham County, NC
Site
Site
number
5/23/14
5/30/14
6/6/14
6/13/14
Jessie Bridges Rd (Nick Creek)
15
0.28
0.27
Smith Hudson Rd (Nick Creek)
16
1.43
1.33
Loves Creek Church Rd
S. Chat Av (Chestnut St., abv
WWTP)
S. Chat Av (E College St., abv
WWTP)
17
0.37
0.54
S
2nd
St (Above WWTP)
0.5
6/27/14
0.67
1.16
18
0.79
1.21
1.22
1.86
1.32
Progress Blvd (WWTP)
19
9.23
11.6
1.77
1.01
10.6
Stagecoach Rd. (Varnell Creek)
20
Rives Chapel Rd (Meadow Creek)
22
Jim Moody Rd (Tick Creek)
23
0.96
0.64
Landrum Creek (Hwy 902)
25
1.05
0.93
Harland Creek (Hwy 902)
26
0.37
Holly Ridge Rd
28
0.14
0.13
Pete Roberson Rd
29
0.06
0.07
Bear Creek (Woody Dam Rd)
30
0.2
0.18
Johnny Shaw Rd
32
0
0.07
0.74
0.48
7.32
11.4
0.63
1.27
Table 3.2: Inorganic Nitrogen (mg/L)-Lower Rocky River tributaries, Chatham County, NC
Site
Site
number
5/23/14
5/30/14
6/6/14
6/13/14
6/27/14
Jessie Bridges Rd (Nick Creek)
15
0.41
0.36
Smith Hudson Rd (Nick Creek)
16
0.23
0.29
Loves Creek Church Rd
S. Chat Av (Chestnut St., abv
WWTP)
S. Chat Av (E College St., abv
WWTP)
17
3.68
0.5
S 2nd St (Above WWTP)
18
0.37
0.25
0.32
0.2
.12
Progress Blvd (WWTP)
19
2.37
1.6
1.8
1.87
1.6
Stagecoach Rd. (Varnell Creek)
20
0.37
0.33
Rives Chapel Rd (Meadow Creek)
22
Jim Moody Rd (Tick Creek)
23
0.19
0.33
Landrum Creek (Hwy 902)
25
0.18
0.21
Harland Creek (Hwy 902)
26
0.21
Holly Ridge Rd
28
0.2
0.25
Pete Roberson Rd
29
0.18
0.25
Bear Creek (Woody Dam Rd)
30
0.58
0.56
Johnny Shaw Rd
32
0.26
0.32
4.45
0.18
0.32
0.52
0.4
0.55
0.5
Table 3.3: Organic Nitrogen (mg/L)-Lower Rocky River tributaries, Chatham County, NC
Trip Blank
5/30/14
Total Nitrogen
6/13/14
6/27/14
0.13
0.06
0.27
0.07
0
0
0
0
0.13
0.06
0.27
0.07
Inorganic Nitrogen
Organic Nitrogen
6/6/14
Table 4.1: Trip blanks
Distilled
Total Nitrogen
Inorganic Nitrogen
Organic Nitrogen
5/23/14
5/30/14
6/6/14
6/13/14
6/27/14
0.56
0.07
0
0.16
0
0
0
0
0
0
0.56
0.07
0
0.16
0
Table 4.2: Distilled water blanks
Note that the water used for the 5/23/2014 blank was from a gallon of distilled water from a local
store; subsequent blanks used laboratory grade distilled water from our labs.