CONTENTS
                                                                                                                                                       Page

Key results......................................................................................................1
Introduction......................................................................................................3
Purpose and scope........................................................................................3
Radioactivity: Principles and health effects.................................................3
Acknowledgments..........................................................................................5
Hydrogeologic setting....................................................................................6
Potomac Group..............................................................................................6
Patuxent Formation........................................................................................6
Patapsco Formation......................................................................................8
Magothy Formation........................................................................................8
Aquia Formation.............................................................................................8
Methods of investigation................................................................................8
Well-numbering system..................................................................................8
Well selection..................................................................................................9
Sample collection and analysis.....................................................................9
Data analysis...................................................................................................10
Quality assurance............................................................................................11
Radium and radioactivity in ground water.....................................................11
Distribution of radionuclides in ground water in selected aquifers
of the upper Chesapeake Bay area .............................................................11
Radium, gross alpha-particle activity and gross beta-particle
activity in Anne Arundel County......................................................................11
Magothy Formation.........................................................................................11
Patapsco Formation.......................................................................................11
Patuxent Formation.........................................................................................12
Gross alpha-particle activity and gross beta-particle activity
in Prince Georges, Baltimore, Harford, Cecil, Kent, and
Queen Annes Counties...................................................................................16
Magothy Formation..........................................................................................16
Potomac Group................................................................................................16
Relation between short-term and long-term measurements
of gross alpha-particle activity and gross beta-particle activity .................16
Factors associated with radionuclides in ground water  ............................29
Water quality....................................................................................................29
pH......................................................................................................................29
Specific conductance.................................................................................... 35
Major ions.........................................................................................................35
Geochemical transects...................................................................................40
Mechanisms of radium mobilization to ground water..................................43
Potential sources of uranium and thorium in the aquifer materials............43
Movement of radium from the aquifer materials into ground water............44
Processes that may limit radium concentrations in ground water..............44
Depth to the screened interval....................................................................... 45
Elevated radium concentrations in Anne Arundel County
relative to the rest of the study area...............................................................47
Radionuclide concentrations in high-chloride wells in
the Aquia Formation....................................................................................... 49
Summary.......................................................................................................... 53
Recommendations for future study................................................................55
Glossary............................................................................................................56
References........................................................................................................58
Appendixes...................................................................................................... 63
A.  Well construction and well location data................................................. 63
B.  Chemical constituents, minimum reporting levels,
sample treatment, and analytical methods................................................... 77
C.  Water-quality data......................................................................................81

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                                                                  ILLUSTRATIONS
Figure                                                                                                      Page

1. Uranium-238 and thorium-232 radioactive decay series....................4
2. Map showing the distribution of radium-226 plus
radium-228 in ground water from the  Magothy Formation
in Anne Arundel County.................................................................................13.
3. Map showing the distribution of short-term gross
alpha-particle activity in ground water from the
Magothy Formation in Anne Arundel County..............................................14
4. Map showing the distribution of short-term gross
beta-particle activity in ground water from
the Magothy Formation in Anne Arundel County..................................... 15
5.  Map showing the distribution of radium-226
plus radium-228 in ground water from the
Patapsco Formation in Anne Arundel County...........................................18
6. Map showing the distribution of short-term
gross alpha-particle activity in ground water
from the Patapsco Formation in Anne Arundel County............................19
7. Map showing the distribution of short-term
gross beta-particle activity in ground water
from the Patapsco Formation in Anne Arundel County........................... 20
8.  Map showing the distribution of radium-226
plus radium-228 in ground water from
the Patuxent Formation in Anne Arundel County..................................... 21
9.  Map showing the distribution of short-term
gross alpha-particle activity in ground water
from the Patuxent Formation in Anne Arundel County.... ........................22
10.  Map showing the distribution of short-term
gross beta-particle activity in ground water
  from the Patuxent Formation in Anne Arundel County......................... 23
11.  Map showing the distribution of short-term
gross alpha-particle activity in ground water
from the Magothy Formation in the upper Chesapeake Bay area .......24
12.  Map showing the distribution of short-term
gross beta-particle activity in ground water
from the Magothy Formation in the upper Chesapeake Bay area........25
13.  Map showing the distribution of short-term gross
alpha-particle activity in ground water from the Potomac
Group in the upper Chesapeake Bay area..............................................26
14.  Map showing the distribution of short-term gross
beta-particle activity in ground water from the Potomac
Group in the upper Chesapeake Bay area..............................................27
15.  Histogram showing the distribution of the ratio of
long-term to short-term gross alpha-particle and
beta-particle activity.................................................................................. 28
16.  Bar graph showing the concentrations of radium-224,
radium-226, and radium-228 in wells in Anne Arundel County............ 29
17.  Relations between pH and (a) short-term gross
alpha-particle activity, and (b) short-term gross beta-particle activity...30
18.  Relation between pH and radium-226 plus radium-228................ 32
19.  Relations between specific conductance and
(a) short-term gross alpha-particle activity, and
(b) short-term gross beta-particle activity................................................36
20.  Relation between specific conductance and
radium-226 plus radium-228 ....................................................................37
21.  Relation between pH and specific conductance
with respect to short-term gross alpha-particle activity......................... 40
22.   Relation between short-term gross alpha-particle
activity and chloride concentrations........................................................ 41
23.  Relation between sodium and chloride
concentrations with respect to radium-226
plus radium-228 concentrations............................................................... 41
24. Transect showing the relation between radium-226
plus radium-228 and chlorideconcentrations on the
Mountain Road peninsula in Anne Arundel County................................ 42
25.  Map showing the distribution of radium-226 plus
radium-228 in relation to specific conductance and
pH in ground water from the Magothy Formation
in Anne Arundel County............................................................................ 46
26.  Relations between depth to the middle of the
screened interval and (a) short-term gross alpha-particle
activity, and (b) short-term gross beta-particle activity......................... 48
27.  Relations between depth to the middle of the
screened interval and radium-226 plus radium-228............................. 49
28.  Relation between radionuclide concentrations
and depth to the middle of the screened interval
for adjacent and nearby wells....................................................................50

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                                                                   TABLES
Table                                                                                                           Page

1. Concentrations of uranium and thorium in
selected rocks, sediments, and minerals.................................................... 5
2. Generalized description of geologic formations
in Anne Arundel County................................................................................. 7
3. Spearman correlation coefficients for radionuclides..............................12
4.  Summary of radium-226, radium-228, and
radium-226 plus radium-228 concentrations
in Anne Arundel County by geologic formation............................................16
5.   Summary of short-term and long-term gross
alpha-particle and gross beta-particle activity
by county and geologic formation..................................................................17
6.   Spearman correlation coefficients for inorganic
constituents, depth to the screened interval, and radionuclides.................31
7.   Statistical summary of short-term gross
alpha-particle activity, short-term gross beta-particle
activity, and radium-226 plus radium-228 concentrations,
grouped by pH quartiles................................................................................. 33
8.   Chemical reactions that may affect the pH of
ground water in the study area....................................................................... 33
9.   Spearman correlation coefficients for inorganic constituents.............. 34
10. Statistical summary of short-term gross alpha-particle
activity, short-term gross beta-particle activity, and
radium-226 plus radium-228 concentrations, grouped
by specific conductance quartiles..................................................................38
11. Comparison of water-quality data and depth of
the screened interval from two wells located
in the West View Shores subdivision in Cecil County.................................39
12.  Statistical summary of short-term gross
alpha-particle activity, short-term gross beta-particle
activity, and radium-226 plus radium-228 concentrations,
grouped by quartiles corresponding to depth to the
middle of the screened interval.................................................................... 52
13.  Comparison of radionuclide concentrations
between wells in the Aquia Formation and wells
with similar specific conductance and pH values
in the Patapsco and Magothy Formations...................................................53

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                                                                           PLATES
 Plate                                                                                                              Page

1. Locations of wells in Anne Arundel County that
were sampled in this study and in the pilot study
of carcinogens in Anne Arundel County well water...................................Pocket
2. Locations of wells in the upper Chesapeake Bay
area that were sampled in this study and in the pilot
study of carcinogens in Anne Arundel County well water..........................Pocket
3. Geochemical transect A-A'......................................................................Pocket
4. Geochemical transect B-B'......................................................................Pocket
5. Geochemical transect C-C'......................................................................Pocket

updated 2/26/01