2004 RESULTS OF SOIL TESTING FOR CADMIUM ON THE

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2004 RESULTS OF SOIL TESTING FOR CADMIUM ON THE Powered By Docstoc
					       2004 RESULTS OF SOIL TESTING FOR
   CADMIUM ON THE GRACE TRACT, THE SUFFOLK
     SCARP, AND LOCATIONS SOUTH OF NC 33
     OF THE PCS PHOSPHATE COMPANY, INC.




                         Prepared for:
                 PCS Phosphate Company, Inc.
                Environmental Affairs Department
                     Aurora, North Carolina




                         Prepared by:
                       CZR Incorporated
                   Wilmington, North Carolina



                       8 OCTOBER 2004




PCS Phosphate DEIS 2006 Appendix E CZR Incorporated 2004 Report
Memorandum

TO:          Jeff Furness, PCS Phosphate

FROM:        Mark Grippo

DATE:        8 October 2004

RE:          Results of soil testing for cadmium on the Grace Tract, the Suffolk Scarp,
             and locations South of NC 33

CC:          Sam Cooper
             CP# 1745.66

1.0     INTRODUCTION

       In February 2004, CZR Incorporated (CZR) sampled the soils of the NCPC Tract
for cadmium (Cd), the results of which were presented in a CZR memorandum dated 26
March 2004. In July 2004, CZR was contracted by PCS Phosphate to collect additional
soil samples on the Grace Tract, the Suffolk Scarp and at various additional locations
south of NC 33 (South of NC 33) in order to examine existing Cd levels in soil series
common to the area. This report summarizes the results of this investigation.


2.0     METHODS

        Soil samples were collected from 45 sites representing fifteen soil series from
three general locations: the Grace Tract, the Suffolk Scarp, and at various additional
locations South of NC 33. Sampling locations were determined using soil series as
identified and mapped on the Beaufort County soil survey maps (Kirby 1995). South of
NC 33, a total of 27 soil samples from six hydric soil series and three non-hydric soils
series were sampled. Hydric soils (USDA 1991) samples included Roanoke (RK), Cape
Fear (CF), Muckalee (ML), Currituck (CM), Portsmouth (PL), and Tomotley (TM). The
non-hydric soils were Augusta (AG), Altavista (AV), and Wahee (WF). These were the
same soil series sampled on the NCPC Tract in February 2004 (CZR 2004). Soil series
sampled on the Suffolk Scarp include two hydric soils, Leon (Lo) and Torhunta (Tr), as
well as Seabrook (Sb), a non-hydric soil. Soil series sampled in the Grace Tract were
Croatan (CT), Dare (Da), and Paxville (Pa) all of which are hydric soils. Sample
locations are depicted in Figures 1 and 2. Sampling locations in relation to Natural
Resource Conservation Service (NRCS) soil series polygons are presented in Figures 3
and 4.




         PCS Phosphate DEIS 2006 Appendix E CZR Incorporated 2004 Report
        Samples were collected from three different locations for each of the fifteen soil
types. Each sample consisted of three sub-samples taken from a 10-foot diameter
circle using a stainless steel auger. Each sub-sample included soil from the surface to
a depth of 3 feet and excluded surface litter and roots. Portions of the three sub-
samples were then thoroughly hand mixed in a plastic bowl. After mixing, a minimum of
one pound of the sample was placed in a plastic bag for laboratory analysis.

       Analysis of Cd in the soil samples was conducted by Southern Testing and
Research Laboratories, Inc. Soil samples were oven dried and then digested using
EPA method 3050B (United States Environmental Protection Agency 1996) and Cd
levels were determined using inductively coupled plasma spectrometry (ICPS) as
described in EPA method 200.7 (United States Environmental Protection Agency 2001).
The ICPS detection limit was 0.1 mg/kg.

        One goal was to compare soil samples collected from the NCPC Tract in
February 2004 to the same soil series collected South of NC 33. Also of interest was
determining variables influencing soil Cd levels. Therefore, soil series were classified
into three categories based on soil texture, as described in the field, and mean Cd
levels were compared for each texture category. The categories used included clay,
sandy clay, sandy (predominately sand but also mixed with clay and loam), and muck.
The texture category of the soil samples was determined based on the amount of a
particular texture within the three-foot soil sample profile. For example, if most of the
three foot soil profile was textured as clay, then sample was placed in the clay texture
category. Statistical comparisons of texture categories were made using a one-way
Analysis of Variance (ANOVA) on log transformed data. If the ANOVA revealed a
significant category effect, a Tukey pair-wise comparison test was used.

       Potential effects of vegetation type were also investigated by classifying sites by
biotic community and comparing mean Cd levels for each of eight community types:
brackish marsh, mixed hardwood forest, pine forest, herbaceous, bottomland hardwood,
shrub scrub, hardwood forest, and agriculture. Statistical comparisons of biotic
communities were made using t-tests and only on those categories containing three or
more samples.

       Soils data can be presented on a wet or dry weight basis. Cadmium level
reported on a wet weight basis includes the weight of water present in the sample, while
dry weight standardizes the sample Cd levels based on the weight of solids. Soil series
sampled in this study have a range of particle sizes, densities, and water content.
Therefore, the percent moisture was calculated for each sample and data are presented
on both a wet and dry weight basis. Metal levels in soil are generally reported by dry
weight; therefore all statistical analysis was performed on dry weight data.


3.0   RESULTS AND DISCUSSION

     Complete soil and site descriptions for each of the 45 samples can be found in
Appendix A. Laboratory results for each of the 45 samples can be found in Appendix B.

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        PCS Phosphate DEIS 2006 Appendix E CZR Incorporated 2004 Report
        There was some soil texture variability within soil samples from the same soil
series. Variability was likely related to the nature of NRCS soil maps. County soil maps
are derived from field sampling and aerial photo interpretation and while accurate
enough for large scale land management, soils on the ground may not match the soil
map at fine spatial scales, due to natural variability, soil inclusions, mapping inaccuracy,
and disturbance. A particular soil series can rarely, if ever, be mapped without including
soils of a different taxonomic class (Kirby 1995).

3.1    South of NC 33

      Most samples were between 1.5 and 3.0 mg/kg dry weight (1.0 and 2.5 mg/kg
wet weight; Table 1), however eight samples were greater than 3.0 mg/kg dry weight.
One sample, AG2 was particularly high (11.5 mg/kg). Muckalee loam and Portsmouth
loam had comparatively low mean Cd levels. Currituck muck had the lowest Cd level
on a wet weight basis, but the dry weight value was much higher (Table 1). The highest
mean Cd levels were in Augusta fine sandy loam and Roanoke fine sandy loam.

       The ANOVA did not reveal a significant differences between texture categories
(p=0.142). Mean Cd levels were highest in the most clayey soils suggesting that clay
content was an important factor in the spatial distribution of soil Cd (Figure 5; Table 2).
Metal concentrations in soil are often found to increase with clay content, as clay has
strong adsorptive properties. Mucky soils had the lowest mean Cd levels, although
mucks from brackish marsh were always higher than mucks from other biotic
communities. Soil Cd is usually found to be positively correlated to percent organic
matter in soil (Chen et al. 1998).

       On a dry weight basis, bottomland hardwood and mixed forest communities had
the lowest Cd levels of all biotic community types. Disturbed herbaceous had the
highest mean Cd level, due to the elevated Cd found in AG2 (Figure 6; Table 2). The T-
tests revealed a significant difference between brackish marsh and hardwood forest
(p=0.043), and hardwood forest and mixed forest (p=0.019). However, any significant
differences in Cd levels from different biotic communities were most likely related to
differences in soils rather than vegetation. For example, samples from sandy soils in
hardwood systems (TM 2, PL 1, and PL 3) were lower than soils taken from hardwood
forests with clay or sandy clay soils (RK 2, AG 1, AG 3, and CF 2). Overall, the limited
sample size does not allow any definitive statements on the effect of biotic community
type on soil Cd.

        Roanoke fine sandy loam and Tomotley fine sandy loam comprise most of the
study area South of NC 33 and both of these soil series are clay or sandy clay soils.
Therefore, most areas South of NC 33 are likely to have Cd levels similar to those found
in this study for these series (1.58 mg/kg to 4.20 mg/kg dry weight).

       For comparison, Cd level, texture category, and biotic community for the soil
samples collected South of NC 33 and from the NCPC Tract (February 2004) are
presented in Table 3. Mean Cd levels found for each soil series sampled at both
locations can be found in Table 1. The data suggest that, 1) Cd levels are higher South
of NC 33, as most samples from the NCPC Tract were between 0.5 and 1.3 mg/ kg dry
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        PCS Phosphate DEIS 2006 Appendix E CZR Incorporated 2004 Report
    Table 1. Cd level (mg/kg dry weight) in each soil sample taken South of NC 33 and the mean cadmium level (mg/kg) for each soil series sampled
    South of NC 33 (July 2004) and the corresponding soil series for samples taken on the NCPC Tract (February 2004). Cd levels (mg/kg) based on
    wet weight are presented in parenthesis.

    Soil Series (ID)a                                 Sample number
                                                                                             Mean ± SD
       Description                                                                                                   Mean ± SD for NCPC
                                            1                2              3              south of NC 33
           Family (texture)
    Tomotley (TM)
      fine sandy loam                  3.25 (2.70)     1.87 (0.627)     1.58 (1.34)    2.23 ± 0.89 (1.56 ± 1.05)    1.34 ± 0.70 (1.09 ± 0.52)
          fine loamy
    Roanoke (RK)
      fine sandy loam                  2.36 (2.00)      4.20 (3.40)     2.43 (2.06)    3.00 ± 1.04 (2.49 ± 0.79)   0.894 ± 0.44 (0.724 ± 0.36)
          clayey
    Cape Fear (CF)
      fine sandy loam                  5.12 (4.16)      2.28 (1.90)    0.994 (0.834)   2.80 ± 2.11 (2.30 ± 1.70)   1.01 ± 0.32 (0.781 ± 0.25)
          clayey
    Portsmouth (PL)
8




      loam                             1.97 (1.58)     1.36 (0.583)     1.71 (1.40)    1.68 ± 0.31 (1.19 ± 0.53)   0.866 ± 0.30 (0.709 ± 0.25)
          fine-loamy over sandy
    Muckalee (ML)
      loam                             1.60 (1.31)     0.674 (0.460)   1.73 (0.978)    1.33 ± 0.58 (0.92 ± 0.43)    2.29 ± 2.56 (1.44 ± 1.89)
          coarse-loamy
    Currituck (CM)
      muck                             2.86 (0.484)    2.18 (0.301)    3.20 (0.797)    2.75 ± 0.52 (0.53 ± 0.25)   1.18 ± 0.42 (0.320 ± 0.19)
           sandy
    Augusta (AG)
      fine sandy loam                  3.81 (3.27)      11.5 (9.18)     4.53 (3.64)    6.61 ± 4.25 (5.36 ± 3.31)   0.578 ± 0.55 (0.467 ± 0.44)
          fine-loamy
    Altavista (AV)
       fine sandy loam                 2.90 (2.47)      2.18 (1.97)     2.11 (1.77)    2.40 ± 0.44 (2.07 ± 0.36)   0.867 ± 0.50 (0.708 ± 0.41)
           fine-loamy
    Wahee (WF)
      fine sandy loam                  2.04 (1.69)      4.37 (3.65)     1.50 (1.26)    2.64 ± 1.53 (2.20 ± 1.27)   0.599 ± 0.16 (0.487 ± 0.13)
          clayey
    a
        Soil series, description, and family based on Kirby, 1995.
Table 2. Soil sample Cd content (mg/kg dry weight), texture category, and biotic community categorization used for
statistical comparisons of samples taken South of NC 33. Cd level (mg/kg) based on wet weight is presented in
parenthesis.

                                                                   Sample number
      Soil Series (ID)a                     1                          2                                3

    Tomotley (TM)
      Texture category                  Sandy                       Sandy                            Sandy
      Biotic community          Disturbed herbaceous      Hardwood forest (cut in 2004)    Mixed pine-hardwood forest
      Cadmium (mg/kg)                 3.25 (2.70)                1.87 (0.627)                      1.58 (1.34)

    Roanoke (RK)
      Texture category                    Sandy                       Clay                         Sandy clay
      Biotic community                  Pine forest              Hardwood forest           Mixed pine hardwood forest
      Cadmium (mg/kg)                   2.36 (2.00)                4.20 (3.40)                     2.43 (2.06)

    Cape Fear (CF)
      Texture category                     Clay                    Sandy clay                     Sandy clay
      Biotic community                  Pine forest              Hardwood forest                Agricultural field
      Cadmium (mg/kg)                   5.12 (4.16)                2.28 (1.90)                   0.994 (0.834)

    Portsmouth (PL)
       Texture category               Sandy                Mucky (sandy component)                  Sandy
       Biotic community           Hardwood forest                Shrub-scrub                    Hardwood forest
      Cadmium (mg/kg)               1.97 (1.58)                  1.36 (0.583)                     1.71 (1.40)

    Muckalee (ML)
      Texture category                 Sandy                        Mucky                             Mucky
      Biotic community       Bottomland hardwood forest   Bottomland hardwood forest      Brackish marsh/forest ecotone
      Cadmium (mg/kg)                1.60 (1.31)                0.674 (0.460)                      1.73 (0.978)

    Currituck (CM)
      Texture category                 Mucky                         Mucky                           Mucky
      Biotic community             Brackish marsh                Brackish marsh                  Brackish marsh
      Cadmium (mg/kg)               2.86 (0.484)                  2.18 (0.301)                    3.20 (0.797)

    Augusta (AG)
      Texture category              Sandy clay                         Sandy                         Clay
      Biotic community            Hardwood forest              Disturbed herbaceous             Hardwood forest
      Cadmium (mg/kg)               3.81 (3.27)                      11.5 (9.18)                  4.53 (3.64)

    Altavista (AV)
       Texture category                    Clay                       Sandy                       Sandy clay
       Biotic community                 Shrub scrub              Agricultural field             Agricultural field
       Cadmium (mg/kg)                  2.90 (2.47)                2.18 (1.97)                    2.11 (1.77)

    Wahee (WF)
      Texture category               Sandy clay                    Sandy clay                        Sandy
      Biotic community          Disturbed herbaceous             Agricultural field             Agricultural field
      Cadmium (mg/kg)                 2.04 (1.69)                  4.37 (3.65)                    1.50 (1.26)

a
    Soil series based on Kirby, 1995.




                                                          10
Table 3. Soil sample Cd content (mg/kg dry weight), texture category, and biotic community categorization used for
statistical comparisons of soil samples collected on the NCPC Tract in February 2004. Cd level (mg/kg) based on wet
weight is presented in parenthesis.

                                                                       Sample number
        Soil Series (ID)a                     1                              2                             3

    Tomotley (TM)
      Texture category                       Clay                            Clay                       Sandy
      Biotic community                    Pine forest             Mixed pine hardwood forest          Pine forest
      Cadmium (mg/kg)                     1.28 (1.06)                     2.07 (1.62)                0.682 (0.578)

    Roanoke (RK)
      Texture category                   Sandy clay                       Sandy clay                   Sandy clay
      Biotic community                   Pine forest              Mixed pine hardwood forest   Mixed pine hardwood forest
      Cadmium (mg/kg)                   0.751 (0.611)                     1.39 (1.13)                0.541 (0.431)

    Cape Fear (CF)
      Texture category                   Sandy clay                          Clay                         Clay
      Biotic community                  Herbaceous                       Shrub scrub           Mixed pine hardwood forest
      Cadmium (mg/kg)                   0.661 (0.508)                    1.10 (0.840)                 1.28 (0.996)

    Portsmouth (PL)
       Texture category                 Sandy clay                       Sandy clay                    Sandy clay
       Biotic community         Mixed pine hardwood forest             Agricultural field      Mixed pine hardwood forest
      Cadmium (mg/kg)                 0.922 (0.757)                     0.545 (0.439)                 1.13 (0.930)

    Muckalee (ML)
      Texture category                    Sandy                             Muck                          Clay
      Biotic community          Bottomland hardwood forest             Brackish marsh          Bottomland hardwood forest
      Cadmium (mg/kg)                 0.774 (0.542)                     0.855 (0.165)                  5.25 (3.61)

    Currituck (CM)
      Texture category                       Muck                          Muck                         Muck
      Biotic community                  Brackish marsh                 Brackish marsh               Brackish marsh
      Cadmium (mg/kg)                    0.806 (<0.10)                  1.09 (0.408)                 1.63 (0.452)

    Augusta (AG)
      Texture category                   Sandy clay                     Sandy                         Sandy clay
      Biotic community                   Herbaceous           Bottomland hardwood forest              Shrub scrub
      Cadmium (mg/kg)                    1.21 (0.981)               0.284 (0.219)                    0.201 (0.201)

    Altavista (AV)
       Texture category                 Sandy clay                         Sandy                      Sandy clay
       Biotic community         Mixed pine hardwood forest               Pine forest                  Pine forest
       Cadmium (mg/kg)                 1.03 (0.858)                      1.26 (1.02)                 0.311 (0.247)

    Wahee (WF)
      Texture category                    Sandy                             Clay                      Sandy clay
      Biotic community          Bottomland hardwood forest               Shrub scrub                  Pine forest
      Cadmium (mg/kg)                 0.436 (0.354)                     0.604 (0.498)                0.758 (0.609)

a
    Soil series based on Kirby, 1995.




                                                             12
weight, while most samples taken South of NC 33 were between 1.5 and 3.0 mg/kg dry
weight (Figure 5), 2) the direct relationship between soil clay content and Cd level was
true for both locations, and 3) biotic communities did not seem to influence soil Cd level
at either location (Figure 6).

Cadmium levels in samples collected South of NC 33 were substantially higher than
those from NCPC. However, no sample from NCPC or South of NC 33 exceeded 85.0
mg/kg, the EPA standard for the surface application of sewage sludge (United States
Environmental Protection Agency 1999). The reason for the disparity between the two
study areas is unknown.

3.2   Suffolk Scarp

      Samples taken from Leon and Torhunta soil series along Suffolk Scarp were
generally below detectable limits although samples from the Seabrook soil series were
somewhat higher (Tables 4 and 5). The soil texture for all samples was sandy or
sandy loam. The low organic matter content of the sandy soils, as well as differences
in hydrology and clay content may account for the lower Cd levels along the scarp
compared to other samples taken South of NC 33. Because most samples were below
detectable limits, no biotic community comparisons were made.

3.3   Grace Tract

        With the exception of Pa 3, Cd levels in all soil samples from the Grace Tract
were below detectable limits (<0.1 mg/kg; Table 6). Pa 3 was a sandy clay soil, not a
mucky soil like the other Grace Tract samples. The presence of clay in Pa 3 likely
accounts for the comparatively higher Cd level (Table 7). Despite the fact that soils with
high organic matter content are known to sequester heavy metals such as Cd, the
mucky organic soils of the grace Tract were found to have very low Cd levels compared
to mucky soils from NCPC Tract and the study area South of NC 33. The disparity may
be related to differences in trace metal inputs and dynamics in pocosins like the Grace
Tract compared to the floodplain and brackish marsh wetlands from which the other
muck samples were taken. For example, the floodplain mucks receive water from
several sources, including brackish tidal creeks, while pocosins receive water from
primarily from rainfall. The distinctive soil chemistry of these systems also may account
for differences in Cd levels.


4.0   SUMMARY

       Cadmium levels in 70 percent of the soil samples collected South of NC 33 were
between 1.5 and 3.0 mg/kg dry weight, and based on the relative proportion of soil
series (primarily clayey soils) within study area South of NC 33, most areas are likely to
have Cd levels within the range of 1.58 to 4.20 mg/kg dry weight. The Cd levels found
South of NC 33 are higher than levels reported in other studies. In a North Carolina
study, a mean Cd level of 0.1 mg/kg dry weight was found for fields receiving
agricultural, municipal, or industrial wastes (Tucker et al. 2003). Cadmium levels
ranging from below detection to 0.33 mg/kg were found in a study of Florida soils (Chen
                                           13
        PCS Phosphate DEIS 2006 Appendix E CZR Incorporated 2004 Report
Table 4. Cd level (mg/kg dry weight) in each soil sample and mean Cd level (mg/kg dry weight) for each
soil series sampled along the Suffolk Scarp. Cd levels (mg/kg) based on wet weight are presented in
parenthesis.


Soil Series (ID)a                            Sample number
   Description                                                                           Mean ±SD
                                   1                2                 3
       Family (texture)

Torhunta (Tr)
   Sandy loam               <0.14 (<0.10)     <0.11 (<0.10)      0.14 (0.115)    <0.13 ± 0.12 (0.11± 0.01)
      Coarse loamy

Leon (Lo)
   Sand                     <0.11 (<0.10)     <0.11 (<0.10)      <0.11 (<0.10)   <0.11± 0.00 (<0.10 ± 0.00)
       Sandy

Seabrook (Sb)
  Loamy sand                0.259 (0.246)     0.279 (0.263)      0.448 (0.401)   0.329 ± 0.104 (0.30 ± 0.09)
      Mixed

a
    Soil series, description, and family based on Kirby, 1995.




                                                        14
Table 5. Suffolk scarp soil sample Cd level (mg/kg dry weight), texture category, and biotic community
categorization. Cd levels (mg/kg) based on wet weight are presented in parenthesis.


                                                         Sample number
    Soil Series (ID)a                1                         2                          3

 Torhunta (Tr)
    Texture category            Mucky sand                   Sand                   Loamy sand
    Biotic community          Hardwood forest         Mixed pine-hardwood       Mixed pine-hardwood
    Cadmium (mg/kg)            <0.14 (<0.10)             <0.11 (<0.10 )            0.140 (0.115)

 Leon (Lo)
    Texture category              Sand                       Sand                      Sand
    Biotic community    Mixed pine-hardwood forest      Hardwood forest      Mixed pine-hardwood forest
   Cadmium (mg/kg)            <0.11 (<0.10)              <0.11 (<0.10)             <0.11 (<0.10)

 Seabrook (Sb)
   Texture category                Sand                      Sand                       Sand
   Biotic community           Hardwood forest           Sand ridge forest            Pine forest
   Cadmium (mg/kg)             0.259 (0.246)             0.279 (0.263)              0.448 (0.401)




                                                 15
Table 6. Cd level (mg/kg dry weight) in each soil sample and mean Cd level (mg/kg dry weight) for each
soil series sampled in the Grace Tract. Cd levels (mg/kg) based on wet weight are presented in
parenthesis.


Soil Series (ID)a                                Sample number
   Description                                                                            Mean ±SD
                                       1               2               3
       Family (texture)

Dare (Da)
  Muck                           <0.44 (<0.10)    <0.25 (<0.10)   <0.29 (<0.10)   <0.33 ± 0.10 (<0.10 ± 0.00)
      Dysic

Paxville (Pa)
  Mucky fine sandy loam          <0.13 (<0.10)    <0.14 (<0.10)    0.45 (0.36)    <0.24 ± 0.18 (0.18 ± 0.15)
        Fine loamy

Croatan (CT)
   Muck                          <0.14 (<0.10)    <0.18 (<0.10)   <0.17 (<0.10)   <0.16 ± 0.02 (<0.10 ± 0.00)
      Loamy

a
    Soil series, description, and family based on Kirby, 1995.




                                                       16
Table 7. Grace Tract soil sample Cd level (mg/kg dry weight), texture category, and biotic community
categorization. Cd levels (mg/kg) based on wet weight are presented in parenthesis.

                                                       Sample number
                                     1                            2                    3
   Soil Series (ID)a

 Dare (Da)
   Texture category                Muck                         Muck                 Muck
   Biotic community               Pocosin                      Pocosin              Pocosin
   Cadmium (mg/kg)              <0.44 (<0.10)                <0.25 (<0.10)        <0.29 (<0.10)

 Paxville (Pa)
   Texture category                Muck                         Muck            Sandy clay/clay
   Biotic community               Pocosin                      Pocosin             Pocosin
   Cadmium (mg/kg)              <0.13 (<0.10)                <0.14 (<0.10)        0.452 (0.357)

 Croatan (CT)
    Texture category               Muck                        Muck            Muck/sandy muck
    Biotic community   Shrub-scrub/ freshwater marsh       Hardwood forest     Pocosin-bay forest
    Cadmium (mg/kg)             <0.14 (<0.10)                <0.18 (<0.10)        <0.17 (<0.10)




                                                 17
et al. 1998) and a range of 0.1 to 1.0 mg/kg was cited in a study of the eastern U.S.
(Tucker et al. 2003). Although biotic community type did not appear to influence Cd
levels, clay content was found to be important, with the highest Cd levels occurring in
clayey soils.

      Most samples taken from the sandy soils along Suffolk Scarp were below
detectable limits, although samples from the Seabrook soil series were somewhat
higher. Differences in hydrology, and the comparatively low organic matter content
and clay content may account for the lower Cd levels along the scarp compared to
other samples South of NC 33.

       Cadmium levels in all but one soil sample from the Grace Tract were below
detectable limits. Mucky soils form the Grace Tract had lower Cd levels than mucks
taken from other biotic community types, which may be a result of the unique hydrology
and soil chemistry of pocosins.


References

Chen, M., L.Q Ma, and W. Harris. 1998. Background concentrations of trace metals in
      Florida surface soils: Comparison of four EPA digestion methods and baseline
      concentrations of 15 metals. Annual Progress Report. University of Florida,
      Gainsville.

CZR Incorporated. 2004. DRAFT Memorandum of Results of NCPC Soil/Cd Sampling.

Kirby, R.M. 1995. Soil Survey of Beaufort County, North Carolina. Natural Resources
       Conservation Service.

Tucker, M.R., D.H. Hardy and C.E. Stokes. 2003. Heavy Metal in North Carolina Soils:
      Occurrence and Significance. North Carolina Department of Agriculture and
      Consumer Services.

United States Environmental Protection Agency. 1996 Method 3050B: Acid digestion
      of sediments, sludges, and soils. United States Environmental Protection
      Agency.

United States Environmental Protection Agency. 2001. Method 200.7: Trace elements
      in water, solids, and biosolids by inductively coupled Plasma-Atomic
      Spectrometry. Revision 5.0. United States Environmental Protection Agency.

United States Environmental Protection Agency. 1999. Standards for the use or
      disposal of sewage sludge as amended 8/04/99. 40 CFR Part 503.

United States Department of Agriculture. 1991. Hydric Soils of the United States.
      Natural Resources Conservation Service.



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        PCS Phosphate DEIS 2006 Appendix E CZR Incorporated 2004 Report