MARCH 3 1849

U S. . DEPARTMENT OF THE INTERIOR
The Distribution of Bromide in

Water in the Floridan Aquifer System,

Duval County, Northeastern Florida

By E.R. German and G.F. Taylor

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 94-4154

Prepared in cooperation with the

City of Jacksonville, Florida

Tallahassee, Florida

1995
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Gordon P. Eaton, Director

Any use of trade, product, or firm names in this publication is for descriptive purposes only

and does not imply endorsement by the U.S. Geological Survey.

For additional information Copies of this report can be

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey, WRD Earth Science Information Center

Suite 3015 Open-File Reports Section

227 North Bronough Street Box 25286, MS 517

Tallahassee, FL 32301 Denver Federal Center

Denver, CO 80225
Contents III

CONTENTS

Abstract.............................................................................................................................................................................. 1

Introduction ....................................................................................................................................................................... 1

Purpose and Scope....................................................................................................................................................... 2

Background.................................................................................................................................................................. 2

Methods of Investigation ............................................................................................................................................. 3

Hydrogeology.................................................................................................................................................................... 3

Bromide Distribution......................................................................................................................................................... 5

Comparison of Recent and Historical Bromide Data .................................................................................................. 5

The Frequency of Bromide Occurrence....................................................................................................................... 5

Relation of Bromide Concentration to Aquifer, Well Depth, and Chemical Characteristics ...................................... 6

Areal Distribution of Bromide in Ground Water ......................................................................................................... 15

Summary and Conclusions................................................................................................................................................ 15

Selected References........................................................................................................................................................... 16

Appendix ........................................................................................................................................................................... 19

FIGURES

1. Map showing location of the study area .................................................................................................................... 2

 2. Diagram showing generalized geology and hydrogeology of Duval County, Florida .............................................. 4

3. Map showing location of wells that were sampled in 1992 for dissolved bromide concentrations .......................... 6

4-10. Graphs showing:

4. Summary of bromide concentration in water from wells tapping the Floridan aquifer system,

1979-80 and 1992, Duval County, Florida......................................................................................................... 7

5. Summary of bromide concentration in water from wells tapping the Upper Floridan aquifer,

both Upper and Lower Floridan aquifers, and the Lower Floridan aquifer, Duval County, Florida ................. 8

6. Relation of concentrations of bromide to calcium, magnesium, sodium, and potassium in water from 86 wells

tapping the Floridan aquifer system, Duval County, Florida ............................................................................. 10

7. Relation of concentrations of bromide to alkalinity, chloride and sulfate in water, and depth of well from

86 wells tapping the Floridan aquifer system, Duval County, Florida............................................................... 11

8. Major-ion composition of water samples from wells tapping the Floridan aquifer system with detectabledissolved bromide concentrations, Duval County, Florida ................................................................................ 12

9. Major-ion composition of water samples from wells tapping the Floridan aquifer system with no detectable

dissolved bromide concentrations, Duval County, Florida ............................................................................... 13

10. Measured and model simulated bromide concentration..................................................................................... 14

11. Map showing areal distribution of bromide concentration in water in the Floridan aquifer system,

July–August 1992 ...................................................................................................................................................... 15

TABLES

1. Results of the Spearman correlation analysis of the relation of dissolved-bromide concentration to other chemical

characteristics and to well properties ...................................................................................................................... 9
IV Contents

CONVERSION FACTORS, ABBREVIATED WATER-QUALITY UNITS, AND ACRONYMS

Multiply By To obtain

 Length

foot (ft) 0.3048 meter

 Abbreviated water-quality units

BrO3

-

 = bromate ion

HOBr = hypobromous acid

HOCl = hypochlorous acidr

 mg/L = milligrams per liter

 O3 = ozone

 OBr-

 = hypobromite ion

Acronyms

DBPs = disinfection by-products

MCL = maximum contaminant level

THM = trihalomethanes

USGS = U.S. Geological Survey

Symbols

 < = less than

 > = more than
Introduction 1

triangular area near the community of Sunbeam,

Florida, and along the St. Johns River throughout

Duval County.

INTRODUCTION

The city of Jacksonville, in Duval County,

Florida, is a rapidly-growing area with an increasing

need for potable water (fig. 1). Although water of good

quality for public supply generally is available in the

county, there is a potential for organic by-products to

be produced in the finished water, resulting from the

treatment of raw water. Known as DBPs (Disinfection

By-Products), they result from chemical treatment of

raw water containing low concentrations of naturally

occurring organic compounds.

These by-products are of concern because many

DBPs are known carcinogens, and others are suspected carcinogens. DBPs include trihalomethanes

(THMs) and other products which commonly result

from the treatment process in which raw water is

disinfected with chlorine or ozone. Presently, waterquality standards are in effect only for total THM

content. A maximum contaminant level (MCL) of

0.1 mg/L has been set by the Florida Department of

Environmental Protection for total THM content in

drinking water (Florida Dept. of State, 1993). The

THMs included in this standard are bromodichloromethane, dibromochloromethane, tribromomethane

(bromoform), and trichloromethane (chloroform).

As mandated by the 1986 Safe Drinking Water

Act amendments, the U.S. Environmental Protection

Agency currently is developing more strict standards

for DBPs. In addition to lowering the present THM

standard, the new regulations may include specific

DBP compounds, including brominated species,

making control of brominated DBPs an important

aspect of water treatment.

The Distribution of Bromide in Water in the Floridan

Aquifer System, Duval County, Northeastern Florida

By E.R. German and G.F. Taylor

ABSTRACT

Although Duval County, Florida, has ample

ground-water resources for public supply, the

potential exists for a problem with excessive

disinfectant by-products. These disinfectant byproducts result from the treatment of raw water

containing low concentrations of bromide and

naturally occurring organic compounds. Because

of this potential problem, the relation of bromide

concentrations to aquifer tapped, well location

and depth, and chemical characteristics of water

in the Floridan aquifer system underlying Duval

County were studied to determine if these relations could be applied to delineate water with

low-bromide concentrations for future supplies.

In 1992, water samples from 106 wells that

tap the Floridan aquifer system were analyzed for

bromide and major dissolved constituents. A

comparison of bromide concentrations from the

1992 sampling with data from earlier studies

(1979-80) indicates that higher bromide concentrations were detected during the earlier studies.

The difference between the old and new data

is probably because of a change in analytical

methodology in the analysis of samples.

Bromide concentrations exceeded the

detection limit (0.10 milligrams per liter) in water

from 28 of the 106 wells (26 percent) sampled in

1992. The maximum concentration was

0.56 milligrams per liter. There were no relations

between bromide and major dissolved constituents, well depth, or aquifer tapped that would be

useful for determining bromide concentrations.

Areal patterns of bromide occurrence are not

clearly defined, but areas with relatively high

bromide concentrations tend to be located in a
2 The Distribution of Bromide in Water in the Floridan Aquifer System, Duval County, Northeastern Florida

Because of the possibility of the formation of

undesirable DBPs and the additional costs of removing them during water treatment, a knowledge of

the distribution of bromide in waters of the Floridan

aquifer system is desirable for resource management.

Locations of future supply wells, for example, could

then be selected to obtain water with minimum

bromide concentrations. The distribution and concentrations of bromide in Duval County have not been

documented, though historical data on bromide concentration are available as a result of past studies.

However, the historical data are of limited usefulness

because of possible bias in the method used to quantitatively determine bromide prior to 1984.

In 1992, the U.S. Geological Survey (USGS), in

cooperation with the city of Jacksonville, sampled

selected wells in Duval County for dissolved bromide,

chloride, and other major constituents in an investigation to delineate the distribution of bromide in water in

the Floridan aquifer system. The relation of bromide

concentration to the aquifer tapped, well location and

depth, and various chemical characteristics of water

was studied to determine if these relations could be

used to locate areas of relatively low-bromide concentrations.

Purpose and Scope

The purpose of this report is to describe the

distribution of bromide in water in the Floridan aquifer

system in Duval County, Fla. (fig. 1), and to present

the results of an investigation to determine relations

between bromide concentration and selected variables.

The description includes an evaluation of historical

data to assess the reliability of the older data, because

the historical bromide concentrations were determined

using a different analytical method than the method

used in 1992. Bromide concentrations are summarized

by aquifer, and the areal distribution of bromide concentration is presented. The relation of bromide concentration to well depth and other more commonly

determined water-quality characteristics are evaluated

to determine if these relations could be used for

estimating bromide concentration in water at locations

that have some water-quality data, but no bromide

data.

Water samples were collected from 106 wells

tapping the Floridan aquifer system in Duval County

during June-August of 1992. Wells were selected for

sampling that would provide a wide and relatively

uniform areal coverage and that would be representative of sampling a range of mineralization commonly

encountered in potable supply wells. Bromide and

chloride concentrations were determined in water

samples from all wells; concentrations of major dissolved constituents were determined in samples from

86 of the wells. All references to bromide and major

ions, except alkalinity, in the following sections refer

to the dissolved concentrations.

Background

Formation of brominated DBPs during routine

drinking water treatment is the result of reactions of

naturally occurring bromide ions in the water with

chlorine or ozone. In the case of chlorination, the

bromide ion (Br-

) is oxidized by hypochlorous acid

(HOCl) to hypobromous acid (HOBr), which then

may react with naturally occurring organic compounds

to form bromoform and other brominated compounds.

The reactions are as follows:

Chlorination of water:

Cl2 + H2O = HOCl + H+ + ClFormation of hypobromous acid:

HOCl + Br-

 = HOBr + ClFormation of DBPs:

HOBr + organic compounds = brominated DBPs

HOCl + organic compounds = chlorinated DBPs

Figure 1. Location of the study area.

0 100 MILES

0 100 KILOMETERS

31°

30°

29°

28°

27°

26°

25°

87° 86° 85° 84° 83° 82° 81° 80°

ATLANTIC OCEAN

GULF OF MEXICO

GEORGIA

ALABAMA

JACKSONVILLE

DUVAL

COUNTY

LOCATION OF

STUDY AREA
Hydrogeology 3

The use of ozone (O3) for treating drinking

water is becoming more prevalent as public utilities

seek to minimize DBP formation with alternatives to

chlorination. However, application of ozone is not

without potential for formation of undesirable DBPs if

the water contains trace levels of bromide. Ozone can

oxidize bromide ions to hypobromous acid, leading to

the formation of bromoform and other brominated

compounds, as in chlorination. In addition, ozone can

further react with the hypobromite ion (OBr-

), formed

by ionization of hypobromous acid, to yield the

bromate ion (BrO3

-

). The bromate ion is a possible

carcinogen (Kurokawa and others, 1986). The reactions are as follows:

Formation of hypobromous acid:

O3 + Br-

 + H2O = O2 + HOBr + OHFormation of bromate ion:

HOBr = H+ + OBrOBr-

 + O3 = 202 + BrO3.

Bromide occurs naturally in low concentrations

in water in the Floridan aquifer system, probably originating from seawater. The concentration of bromide

in seawater is about 67 mg/L, and the concentration of

chloride is about 19,000 mg/L (Hem, 1986), resulting

in a mass ratio of about 0.0035. Various geochemical

processes could result in the variation of bromide to

chloride (and other ion) ratios in water in the Floridan

aquifer system.

Methods of Investigation

Prior to sampling, all wells were purged by

removing at least three casing volumes of water. If

specific conductance, pH, or temperature of the purged

water were still changing after three casing volumes

had been removed, the well was further pumped (or

allowed to discharge if free flowing) until these waterquality characteristics had stabilized or until

five casing volumes of water had been removed.

Sample bottles then were filled from the pump discharge. The points of sample withdrawal were as close

to the wellhead as possible, and all samples were taken

on the pump side of any pressure tanks or treatment

points.

Samples for dissolved constituents were filtered

through a 0.45-micron membrane filter and treated

according to methods described in Fishman and

Friedman (1985). Samples for the determination of

specific conductance and alkalinity were not filtered.

All samples were analyzed in the USGS laboratory in

Ocala, Fla.

HYDROGEOLOGY

Two aquifer systems are present in the study

area. They are, in the order in which they would be

penetrated by a well, the surficial aquifer system and

the Floridan aquifer system. Separating the two aquifer systems are the clays, silts, and sands of the intermediate confining unit, which includes most of the

Hawthorn Formation. The intermediate confining unit

contains beds of lower permeability that confine the

water in the Floridan aquifer system under artesian

pressure. The Floridan aquifer system has three major

water-bearing zones separated by less-permeable

semiconfining units (Brown, 1984). All the geologic

units in the study area yield some water to wells, but

their water-bearing characteristics differ considerably. The major hydrogeologic units underlying the

area, their stratigraphic equivalent, and their hydrologic properties are shown in figure 2.

The Floridan aquifer system, the principal

source of ground water in northeastern Florida, underlies all of Florida and parts of Alabama, Georgia,

and South Carolina. Most reports that describe the

hydrogeology of northeastern Florida use the terms

“Floridan aquifer” (Parker and others, 1955) or “the

principal artesian aquifer” (Stringfield, 1966) to

describe the water-bearing rocks herein referred to as

the Floridan aquifer system. Miller (1986, p. B45)

defined the Floridan aquifer system as a vertically continuous sequence of carbonate rocks of generally high

permeability that are mostly of Tertiary age; the rocks

are hydraulically connected in varying degrees, and

their permeability generally is one or more orders

of magnitude greater than that of rocks bounding the

system above and below.

The Floridan aquifer system ranges from about

1,600 to 1,900 ft in thickness in the study area. The

system is divided into two aquifers of relatively high

permeability, referred to as the Upper Floridan and the

Lower Floridan aquifers. In the study area, the Lower

Floridan aquifer is further divided into two waterbearing zones. These aquifers are separated by a less

permeable unit that restricts the vertical movement of

water.
4 The Distribution of Bromide in Water in the Floridan Aquifer System, Duval County, Northeastern Florida

Series Formation

Approximate

thickness

(feet)

Lithology Hydrogeologic unit Hydrologic properties

Holocene

to Upper

Miocene

Undifferentiated

surficial deposits

20-

120

Discontinuous sand,

clay, shell beds, and

limestone

Surficial aquifer

system

Sand, shell, limestone, and

coquina deposits provide local

water supplies.

Miocene

Hawthorn

Formation

100-

500

Interbedded

phosphatic sand,

clay, limestone, and

dolomite

Sand, shell, and carbonate

deposits provide local

limited water supplies.

Low permeability clays serve

as the principal confining

beds for the Floridan

aquifer system below.

Intermediate

confining unit

Eocene

Upper

 Ocala

 Limestone

100-

350

Massive fossiliferous

chalky to granular

marine limestone

Floridan aquifer system

Upper Floridan

aquifer

Principal source of ground

water. High permeability overall.

Water from some wells shows

increasing salinity.

Avon Park

Formation

700-

1,100

Alternating beds of

massive granular and

chalky limestones,

and dense dolomites

Middle

Middle semiconfining

unit

Low permeability limestone

and dolomite.

Lower Floridan

 aquifer

Upper zone

Principal source of ground water.

Water from some wells shows

increasing salinity.

Lower

Oldsmar

Formation 300-500

Semiconfining

unit

Low permeability limestone

and dolomite.

Fernandina

permeable zone

High permeability salinity

increases with depth.

Paleocene Ceder Keys

Formation

about

500

Uppermost appearance

of evaporites; dense

limestones

Sub-Floridan

confining unit

Low permeability; contains

highly saline water.

The Upper Floridan aquifer in the study area

corresponds to the Ocala Limestone and, in some

areas, also includes the upper part of the Avon Park

Formation. The top of the aquifer generally lies at

greater depths in the northern part of the study area;

the altitude at the top of the aquifer surface ranges

from about 250 ft below sea level to more than 600 ft

below sea level in several areas in central Duval

County (Spechler, 1994).

The middle semiconfining unit separates the

Upper and Lower Floridan aquifers and comprises

beds of dense, relatively less-permeable limestone and

dolomite of variable thickness and permeability. This

unit generally is present in the upper part of the Avon

Park Formation, and ranges in thickness from about

100 to 200 ft (Miller, 1986, p. B57).

Brown (1984, p. 15) recognized two major

water-bearing zones within the Lower Floridan aquifer: the middle water-bearing zone and the lower

water-bearing zone, referred to in this report as the

upper zone of the Lower Floridan and the Fernandina

permeable zone, respectively (fig. 2). These zones are

separated by another less permeable semiconfining

unit.

In most of the study area, the upper zone of the

Lower Floridan aquifer consists of approximately the

lower two-thirds of the Avon Park Formation, which is

composed of alternating beds of limestone and dolomite. Permeability in this zone is mostly related to

secondary porosity developed along bedding planes,

joints, and fractures. The unit is about 500 ft thick in

the Jacksonville area and the top is about 950 to

1,400 ft below land surface (Krause and Randolph,

1989, p. 22). About half of the water pumped by large

municipal and industrial wells in the Jacksonville area

is from the upper zone of the Lower Floridan aquifer

(Krause and Randolph, 1989, p. 22).

The Fernandina permeable zone is a highpermeability unit that lies at the base of the Floridan

aquifer system in parts of southeastern Georgia and

northeastern Florida (Miller, 1986, B70). Little is

known about the extent or thickness of the Fernandina

Figure 2. Generalized geology and hydrogeology of Duval County, Florida (from Spechler, 1994).
Bromide Distribution 5

permeable zone. Data from the few wells that have

penetrated the zone in the study area indicate that the

zone extends over the northern half of St. Johns and all

of Duval and Nassau Counties. The thickness of the

zone is estimated to be about 100 ft in the Jacksonville

area.

BROMIDE DISTRIBUTION

Bromide concentrations and other water-quality

data collected in June-August 1992 from the 106 wells

in Duval County (fig. 3) are listed in the appendix.

Well data also are listed in the appendix. In following

sections of the report these data are summarized in

three ways. Exploratory data analysis is used to

describe the distribution of concentrations by aquifer.

Correlation analysis and data plots are used to indicate

the relation of bromide to other characteristics. Mapscale plots of bromide concentrations are used to

depict areal patterns.

Comparison of Recent and Historical Bromide

Data

Historical data (1979-80) on the concentration of

dissolved bromide apparently are not comparable with

recent data (1992) because of a change in 1984 in analytical methodology. The historical data have a tendency

toward higher bromide concentrations, as indicated by a

summary of bromide concentrations in water from

162 wells tapping the Floridan aquifer system in Duval

County sampled in 1979-80 (fig. 4). The median of the

historical bromide concentrations is 0.10 mg/L, whereas

the median of the recent sampling of 106 wells in Duval

County is <0.10 mg/L. The maximum concentration of

the historical data was 2.3 mg/L, whereas the maximum

of the recent data is 0.56 mg/L.

More specific evidence of the non-comparability of historical and recent bromide data is furnished

by data for 35 wells that were sampled in 1979-80 and

again in 1992 (fig. 4). Bromide concentrations were

less than the detection limit in only 2 of the wells sampled in 1979-80 but were less than the detection limit

in 21 of the 35 wells sampled in 1992. Of the 35 wells

sampled twice, 27 had higher bromide concentrations

in the earlier samples. The median concentration of

the 1979-80 sampling was 0.20 mg/L, but <0.10 mg/L

for the 1992 sampling.

It is not likely that bromide concentrations were

lower in 1992 than prior to 1981, because there is no

reason to expect such a regional change. Further, other

water-quality characteristics were nearly the same for

both periods. For example, the median chloride concentration of water from 34 wells sampled both

periods for chloride was 20 mg/L prior to 1981 and

was 19 mg/L in 1992.

The reason for the differences in the bromide

concentrations reported for the two periods probably

is differences in the laboratory methods for sample

analysis. Bromide concentrations in the water samples

collected in 1979-80 were determined by the USGS

laboratory in Atlanta, using the catalytic oxidation

method (Skougstad and others, 1979, p. 329-330).

This method is based on the catalytic effect of bromide

on the oxidation of a known amount of iodide by

potassium permanganate. The bromide concentrations

in water samples collected in 1992 and presented in

this report were determined by the USGS laboratory in

Ocala, using a modification of the phenol-red method

(American Public Health Association, 1992). In this

method, bromide ions present in the water sample are

oxidized to bromine, which then hydrolyzes to hypobromite. The hypobromite ion reacts with phenyl red

to form a characteristically colored complex; the concentration then can be accurately determined with

spectrophotometry. Determination of the reason for

differences in concentrations reported by the two analytical methods is beyond the scope of this study. Further discussions of the distribution of bromide in this

report are based only on the data collected in 1992.

The Frequency of Bromide Occurrence

In 1992, bromide concentration exceeded the

detection limit (0.10 mg/L) in water from 28 of the

106 wells sampled (26 percent). The maximum concentration of bromide was 0.56 mg/L, and the median

concentration was <0.10 (fig. 4).

A summary of the bromide concentrations by

aquifer supplying water to the well indicates that

75 percent of the wells tapping only the Upper Floridan aquifer had bromide concentrations in water of

about 0.13 mg/L or less, and more than 75 percent of

the wells tapping both the Upper and Lower Floridan

aquifers had concentrations in water less than

0.10 mg/L (fig. 5). The overall distribution of data

indicates no difference in bromide concentration in

water from wells tapping the Upper Floridan aquifer

and water from wells tapping both the Upper and

Lower Floridan aquifers. Six wells tap only the Lower

Floridan aquifer, which is an insufficient number to

assess aquifer-related differences in concentration.
6 The Distribution of Bromide in Water in the Floridan Aquifer System, Duval County, Northeastern Florida

Figure 3. Location of wells that were sampled in 1992 for bromide concentrations, Duval County, Florida.

(Map number is used to identify wells in the appendix.)

Relation of Bromide Concentration to Aquifer,

Well Depth, and Chemical Characteristics

The single-variable relation of bromide concentration to well and casing depth, and to other chemical

characteristics was investigated by applying the Spearman correlation analysis and by using graphical analysis. In the Spearman correlation analysis, data values

(concentrations, well properties) are replaced with

their ranks, with 1 representing the lowest concentration or value, and the total number of data values representing the highest concentration or value. The use

of ranks, rather than raw data, makes the correlation

procedure nonparametric, or unaffected by the distribution of the data.

Coefficients of determination and p-values

for these coefficients were computed from the

Spearman correlation analysis, and are given in table 1.

The coefficients of determination indicate the fraction

of the variation in rank of the bromide concentration

(the dependent variable) that is explained by the variation in rank of the other chemical characteristics or

well properties (independent variables). The p-value is

a probability representing the significance of the analysis, and is used to infer whether or not to reject the

null hypothesis (no relation between bromide and the

independent variable). In this report, the null hypothesis is rejected if the p-value is 0.05 or less, indicating

that relations between bromide and the independent

variable are considered to be real (statistically significant), rather than just due to chance.

The Spearman correlation analysis was done in

two ways. First, all wells were used, even if bromide

concentrations were undetectable. A mean rank was

computed and used for all wells with undetectable

bromide concentrations. The analysis then was

repeated using only wells with detectable concentrations of bromide.

82° 00′ 45′ 30′

30° 30′

30° 05′

15′

81° 15′

10 MILES

10 KILOMETERS

0 

0 

2 

2 

4 

4 

6 

6 

8 

8 

Baldwin

Atlantic

Beach

Neptune

Beach

Jacksonville

Beach

Sunbeam

CLAY COUNTY

DUVAL COUNTY

DUVAL COUNTY

ST. JOHNS COUNTY

DUVAL COUNTY

NASSAU COUNTY

A T L A N T I C O C E A N

95

95

10

295

295

10

Jacksonville

90

St.

Johns

River

St. Johns

River

Na ssau

River

A1A

84

106

105

100

59

49

29

21

15 17

8 7

6

9

10

13,14

11

19

27

24

23

26

4

2

1

5 3

12

18

25

39 38 35

41

43

48

56

60

71

78

90

94

98

76

92 91 89

86

85

87,

88

83

82

80

73

74

79

103

104

98

65

57

42

47

54 53

63 62

40

28

32 33

44

45 46

30,31

55

66

75 77

81

93

95 99

102

101

51

64 67

68 61

58

70 72

37 36

34

22

69

52 

50

50

16

20
Bromide Distribution 7

Detection Limit

0.1 milligrams

per liter

Detection Limit

0.1 milligrams

per liter

.

Maximum

90th percentile

75th percentile

Median

1979-80 1992

25th percentile

0

0.5

1.0

1.5

2.0

2.5

ALL WELLS

(162 wells)

106 wells

(35 wells)

WELLS THAT WERE SAMPLED IN BOTH 1979-80 AND IN 1992

0

0.2

0.4

0.6

0.8

1.0

Below detection : 2 21

Below detection: 80 78

1979-80 1992

DISSOLVED BROMIDE CONCENTRATION, IN MILLIGRAMS PER LITER

Maximum

90th percentile

75th percentile

Median

0.1

0.1

Figure 4. Summary of bromide concentration in water from wells tapping the Floridan aquifer

system, 1979-80 and 1992, Duval County, Florida.
8 The Distribution of Bromide in Water in the Floridan Aquifer System, Duval County, Northeastern Florida

<0.10

0.20

0.40

0.60

Upper (62) Both (33) Lower (6)

UNIT OF THE FLORIDAN AQUIFER SYSTEM

DISSOLVED BROMIDE CONCENTRATION, IN MILLIGRAMS PER LITER

4 wells

Maximum

90th percentile

75th percentile

below detection

limit

43 wells

below detection

limit

24 wells

below detection

limit

Well 301604081361501

Well 301639081330802

0.10

TAPPED BY WELLS AND NUMBER OF WELLS SAMPLED

Detection Limit

0.10 milligrams

per liter

Figure 5. Summary of bromide concentration in water from wells tapping the Upper

Floridan aquifer, both Upper and Lower Floridan aquifers, and the Lower Floridan aquifer, Duval

County, Florida.
Bromide Distribution 9

Table 1. Results of the Spearman correlation analysis of the relation of

dissolved-bromide concentration to other chemical characteristics and to

well properties

[The coefficients of determination indicate the fraction of the variation in rank of bromide

concentration that is explained by variation in rank of the other chemical characteristics or

well properties. The p-value is a probability representing the significance of the analysis.

A p-value of 0.05 or less indicates a statistically significant relation. <, less than]

Chemical

characteristic or

well property

All samples Only samples with

detectable bromide

Coefficient of

determination p-value Coefficient ofdetermination p-value

Calcium 0.04 0.03 0.23 <0.01

Magnesium .02 .14 .18 .01

Sodium <.01 .69 .16 .02

Potassium .21 <.01 .15 .03

Alkalinity, total .08 <.01 .04 .27

Sulfate .03 .11 .04 .31

Chloride .01 .22 .19 .01

Well depth -.01 .28 .01 .54

Casing depth -.01 .66 .03 .43

The correlation analysis using all samples,

including those in which bromide was not detectable,

indicates only relatively weak relations of bromide

concentration to any of the independent variables.

Bromide concentrations are significantly related

(p-value <0.05) only to concentrations of calcium,

potassium, and alkalinity. Of these, the relation

between bromide and potassium explains most variation in bromide concentration, with a coefficient of

determination of 0.21.

Excluding all samples with undetectable bromide concentration, the relation of bromide concentrations to the independent variables is still relatively

weak. However, there are more statistically significant

relations in this data set than in the data set that

includes the wells with undetectable bromide. The

relation of bromide concentration to calcium concentration accounts for the most variation in bromide concentration, with a coefficient of determination of 0.23.

Scatter-plots of bromide with concentrations of

major cations (fig. 6), anions, and well depth (fig. 7)

show the lack of a strong relation between bromide

and the other characteristics. The plots indicate that

waters containing high concentrations of sodium

(>50 mg/L) or chloride (>100 mg/L) generally have

bromide concentrations that are lower than would be

expected if the waters were simple dilutions of seawater with rainwater (indicated by seawater dilution

curve). Also, bromide concentrations are always

lower in relation to the potassium content than would

be expected based on dilutions of seawater. This indicates that the waters of the Floridan aquifer system are

not always simple mixtures of seawater and freshwater

that are in contact with limestone, but may contain

sodium, potassium, and chloride from other sources.

Alternatively, sodium, potassium, and chloride from

seawater are preferentially concentrated in the solid

phase relative to bromide during precipitation of halite

from seawater. Subsequent dissolution of the halite

may result in waters with a lower ratio of bromide to

chloride than is present in seawater. Regardless of the

exact processes involved, the end result is that the

relation of bromide to other dissolved constituents in

the Floridan aquifer system is so variable that little

relation is evident at the low concentrations of bromide in the aquifer system underlying the study area.

The major-ion diagrams of water samples containing detectable concentrations of bromide (fig. 8)

indicate that waters where sodium plus potassium

make up about 20 percent or more of the cations

present, and chloride makes up about 30 percent or

more of the anions present tend to have higher bromide concentrations (>0.25 mg/L). However, other

waters with no detectable bromide concentrations may

also have similar sodium plus potassium and chloride

compositions (fig. 9). Therefore, a water type with

relative high concentration of sodium plus potassium

and chloride will not necessarily have detectable concentrations of bromide.

Multiple-regression analysis was used to determine if bromide concentrations were a function of the

concentrations of two or more other constituents. The

theory and use of multiple regression is discussed in

many books on statistical analysis, for example,

Draper and Smith (1981). Much more of the variation

in bromide concentration was explained by application
10 The Distribution of Bromide in Water in the Floridan Aquifer System, Duval County, Northeastern Florida

0

1.0

0.2

0.4

0.6

0.8

0 50 100 150 200 0

1.0

0.2

0.4

0.6

0.8

0 2 4 6

0

0.8

0.2

0.4

0.6

00 50 100 150 200 0

0.8

0.2

0.4

0.6

1010 20 30 40 50 60

DISSOLVED BROMIDE CONCENTRATION, IN MILLIGRAMS PER LITER

Seawater dilution

Seawater dilution

[For clarity, bromide concentrations less than the detection limit

(0.10 milligrams per liter) are plotted at 0.]

DISSOLVED CALCIUM

CONCENTRATION, IN

MILLIGRAMS PER LITER

DISSOLVED MAGNESIUM

CONCENTRATION, IN

MILLIGRAMS PER LITER

DISSOLVED SODIUM

CONCENTRATION, IN

MILLIGRAMS PER LITER

DISSOLVED POTASSIUM

CONCENTRATION, IN

MILLIGRAMS PER LITER

Figure 6. Relation of concentrations of bromide to calcium, magnesium, sodium, and potassium in water from 86 wells

tapping the Floridan aquifer system, Duval County, Florida.
Bromide Distribution 11

0

0.8

0.2

0.4

0.6

0 100 200 300

0

0.8

0.2

0.4

0.6

0 1,000 2,000

0

0.8

0.2

0.4

0.6

80 100 120 140 160 180 200

0

0.8

0.2

0.4

0.6

0 100 200 300 400

DISSOLVED BROMIDE CONCENTRATION, IN MILLIGRAMS PER LITER

DEPTH OF WELL, IN FEET

-

Seawater dilution

[For clarity, bromide concentrations less than the detection limit

(0.10 milligrams per liter) are plotted at 0.]

TOTAL ALKALINITY, IN

MILLIGRAMS PER LITER AS CaCO3

DISSOLVED CHLORIDE, IN

MILLIGRAMS PER LITER

DISSOLVED SULFATE, IN

MILLIGRAMS PER LITER

Figure 7. Relation of concentrations of bromide to alkalinity, chloride, sulfate, and depth of well in water from 86 wells

tapping the Floridan aquifer system, Duval County, Florida.
12 The Distribution of Bromide in Water in the Floridan Aquifer System, Duval County, Northeastern Florida

of a multivariable regression model than application

of the single-variable correlation analysis. Using only

samples with detectable bromide concentrations, modeling results indicated that including all of the major

constituents as independent variables explained

75 percent of the variation in bromide concentration

with a standard error of estimate of 0.068 mg/L. A plot

of measured and simulated bromide concentrations

indicates an acceptable fit between model simulated

and measured bromide-concentration data, but concentrations above 0.4 mg/L were overestimated in

model simulation (fig. 10).

Although the multivariable model fits the samples with detectable bromide concentrations moderately well, it is not applicable to water with nondetectable concentrations of bromide (fig. 10). Bromide concentrations as high as 0.34 mg/L were simulated for samples with no detectable concentrations.

BROMIDE CONCENTRATION BETWEEN 

0.10 AND 0.25 MILLIGRAMS PER LITER

BROMIDE CONCENTRATION EXCEEDS

0.25 MILLIGRAMS PER LITER

EXPLANATION

CATIONS ANIONS PERCENT OF TOTAL EQUIVALENTS

Figure 8. Major-ion composition of water samples from wells tapping the Floridan aquifer system with detectable dissolvedbromide concentrations, Duval County, Florida.
Bromide Distribution 13

However, the agreement between simulated and

measured bromide concentrations was good for simulated bromide concentrations exceeding 0.34 mg/L,

though there is possibly a bias towards higher simulated concentrations. Thus, the model may be useful

for simulating high concentrations (>0.34 mg/L) of

bromide.

Logistic regression is a statistical technique

for relating binary responses for a variable (such as

detection or nondetection of bromide) to values of

independent variables, such as water-quality characteristics. The technique is discussed in many books

on statistical analysis, for example, Hosmer and

Lemeshow (1989). The logistic models evaluated for

bromide give the probability of finding detectable

concentration of bromide (>0.1 mg/L) as a function of

concentrations of other constituents, using data for

all wells sampled in 1992. In evaluating the logistic

models, a simulated probability of 0.5 or higher was

accepted as positive for detectable bromide.

CATIONS ANIONS PERCENT OF TOTAL EQUIVALENTS

Figure 9. Major-ion composition of water samples from wells tapping the Floridan aquifer system with no detectable

dissolved-bromide concentrations, Duval County, Florida.
14 The Distribution of Bromide in Water in the Floridan Aquifer System, Duval County, Northeastern Florida

Determining the wells with detectable concentrations of bromide by simulation with logistic models

was not successful. A single-variable model with

potassium concentration as the independent variable

simulated detectable bromide concentrations in water

from only 31 percent of the wells with measured

detectable concentrations of bromide. Including all

cations and anions as independent variables (calcium,

magnesium, sodium, potassium, alkalinity, chloride,

and sulfate) in the logistic model improved the simulation accuracy somewhat, however detectable bromide

concentration was simulated in water from only

41 percent of the wells with measured detectable

bromide concentration.

Figure 10. Measured and model simulated bromide concentration.

(The model was developed using only samples with detectable concentrations of bromide,

though all samples are plotted. For clarity, measured bromide concentrations less than the

detection limit (0.10 milligrams per liter) are plotted at 0.)

0

0.7

0.1

0.2

0.3

0.4

0.5

0.6

SIMULATED DISSOLVED BROMIDE CONCENTRATION, IN MILLIGRAMS PER LITER

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

MEASURED DISSOLVED BROMIDE CONCENTRATION, IN MILLIGRAMS PER LITER

Simulated dissolved bromide concentration = 0.016397 + (0.008168 x calcium)

+ (0.014575 x magnesium) + (0.001855 x sodium) + (0.079669 x potassium)

- (0.003099 x alkalinity) - (0.003666 x sulfate) - (0.001981 x chloride),

where all concentrations are in milligrams per liter

Line of exact agreement between simulated

and measured bromide concentration

Number of samples: 31

Coefficient of determination: 0.75

Standard error of estimate: 0.068 milligrams per liter
Summary and Conclusions 15

Areal Distribution of Bromide in

Ground Water

Though the areal pattern of bromide concentrations in water in the Floridan aquifer system is not

clearly defined, there are some indications of geographic areas with relatively high-bromide concentrations (fig. 11). A triangular area in which bromide

concentrations generally were greater than 0.25 mg/L

is located near the central part of the study area near

Sunbeam. The area contains 13 wells, 8 of which

yielded water containing more than 0.25 mg/L bromide, and 3 others which had detectable concentrations of bromide. Bromide concentrations were less

than 0.1 mg/L in water from only two wells in the triangular area. Many of the wells along the St. Johns

River also yielded water with detectable concentrations of bromide. Reasons for these areal patterns of

bromide concentration are not obvious--they may be

related to faulting associated with the river channel or

other features which could allow intrusion of higherbromide water to the sampled wells.

SUMMARY AND CONCLUSIONS

Water of good quality for public supply generally is available in Duval County, northeastern Florida.

However, the potential exists for a problem with the

formation of excessive disinfectant by-products in finished water, resulting from the treatment of raw water

containing low concentrations of naturally occurring

organic compounds. Brominated disinfectant byproducts, which may form in water containing trace

quantities of bromide, are of particular significance

because the brominated species may be assigned maximum contaminant levels that are even lower than

those currently set for chloroform. In 1992, the USGS,

Figure 11. Areal distribution of bromide concentration in water in the Floridan aquifer system, July–August 1992,

Duval County, Florida.

DISSOLVED BROMIDE

CONCENTRATION

(Milligrams per liter)

Br less than 0.1

Br greater than or equal to 0.25

Br greater than or equal to 0.1,

and less than 0.25

EXPLANATION

AREA WITH HIGH BROMIDE

CONCENTRATION

82° 00′ 45′ 30′

30° 30′

30° 15′

81° 15′

10 MILES

10 KILOMETERS

0 

0 

2 

2 

4 

4 

6 

6 

8 

8 

Baldwin

Atlantic

Beach

Neptune

Beach

Jacksonville

Beach

Sunbeam

CLAY COUNTY

DUVAL COUNTY

DUVAL COUNTY

ST. JOHNS COUNTY

DUVAL COUNTY

NASSAU COUNTY

A T L A N T I C O C E A N

95

95

10

295

295

10

Jacksonville

90

St.

Johns

River

St. Johns

River

Na ssau

River

A1A
16 The Distribution of Bromide in Water in the Floridan Aquifer System, Duval County, Northeastern Florida

in cooperation with the city of Jacksonville, sampled

selected wells in Duval County in an investigation to

delineate the distribution of bromide in water in the

Floridan aquifer system.

Two aquifer system are present in the study

area. They are, in the order in which they would be

penetrated by a well, the surficial aquifer system and

the Floridan aquifer system. Separating the two aquifers are the clays, silts, and sands of the intermediate

confining unit, which includes most of the Hawthorn

Formation. The Floridan aquifer system, which consists mostly of highly permeable carbonate rock, is the

principal source of ground water in Duval County.

A total of 106 wells tapping the Floridan aquifer

system were sampled and the concentrations of bromide and major dissolved characteristics were determined. A comparison of bromide concentrations from

the 1992 sampling and from earlier studies in 1979-80

indicated that the earlier data had higher concentrations of bromide. The difference in the earlier and later

data likely is because of a change in analytical methodology, but the reason for the differences is

unknown.

In 1992, bromide concentrations exceeded the

detection limit (0.10 milligrams per liter) in water

from 28 of the 106 wells (26 percent) with the maximum concentration of 0.56 milligrams per liter. No

indication is evident of a difference in bromide concentrations between wells open only to the Upper

Floridan aquifer and those open to both the Upper and

Lower Floridan aquifers.

Bromide concentration is related only weakly

to well depth and concentrations of other constituents.

There were no single-variable relations between

bromide and major dissolved constituents, well depth,

or aquifer that would be useful for predicting bromide

concentrations. Much more of the variation in bromide

concentration was simulated with a multivariate

regression model than with the single-variable models,

and may be useful for simulating relatively high concentrations of bromide (>0.34 milligrams per liter).

The areal distribution of bromide in waters of

the Floridan aquifer system is not clearly defined, but

higher than common concentrations were observed

along the St. Johns River and in a triangular area near

the community of Sunbeam.

SELECTED REFERENCES

American Public Health Association, 1992, Standard

methods for the examination of water and wastewater

(18th ed.): Washington, D.C., p. 4-11.

Brown, D.P., 1984, Impact of development on availability

and quality of ground water in eastern Nassau County,

Florida, and southeastern Camden County, Georgia:

U.S. Geological Survey Water-Investigations Report

83-4190, 113 p.

Draper, N.R., and Smith, Harry, 1981, Applied regression

analysis (2d ed.): New York, John Wiley, 709 p.

Fishman, M.J., and Friedman, L.C., eds., 1985, Methods for

determination of inorganic substances in water and

fluvial sediments: U.S. Geological Survey Techniques

of Water-Resources Investigations, book 5, chap. A1,

Open-File Report 85-495, 709 p.

Florida Department of State, 1993, Rules of the Department

of Environmental Protection, public drinking water

systems: Tallahassee, Fla., chap. 17-550, in Florida

Administrative Code.

Hem, J.D., 1986, Study and interpretation of the chemical

characteristics of natural water: U.S. Geological

Survey Water-Supply Paper 1473, 363 p.

Hosmer, D.W., Jr., and Lemeshow, S., 1989, Applied logistic regression: Journal of the National Cancer Institute,

v. 77, no. 4, p. 977-982.

Krause, R.E., and Randolph, R.B., 1989, Hydrology of the

Floridan aquifer system in southeast Georgia and

adjacent parts of Florida and South Carolina: U.S.

Geological Survey Professional Paper 1403-D, 65 p.,

18 pls.

Kurokawa, Y., Aoki, F., Matsushima, Y., Takamura, N.,

Imazawa, T., and Hayashi, Y., 1986, Dose-response

studies in the carcinogenicity of potassium bromate in

F334 rats after long-term oral administration: Journal

of the National Cancer Institute, v. 77, no. 4,

p. 977-982.

Miller, J.A., 1986, Hydrogeologic framework of the Floridan aquifer system in Florida and in parts of Georgia,

Alabama, and South Carolina: U.S. Geological Survey

Professional Paper 1403-B, 91 p., 28 pls.

Parker, G.G., Ferguson, G.E., Love, S.K., and others, 1955,

Water resources of southeastern Florida: U.S. Geological Survey Water-Supply Paper 1255, 965 p.

Skougstad, M.W., Fishman, M.J., Friedman, L.C., and

others, 1979, Methods for determination of inorganic

substances in water and fluvial sediments: Techniques

of Water-Resources Investigations of the United States

Geological Survey, book 5, chap. A1, 626 p.

Spechler, R.M., 1994, Saltwater intrusion and quality of

water in the Floridan aquifer system, northeastern

Florida: U.S. Geological Survey Water-Resources

Investigations Report 92-4174, 76 p., 1 pl.

Stringfield, V.T., 1966, Artesian water in Tertiary limestone

in the Southeastern States: U.S. Geological Survey

Professional Paper 517, 226 p.
APPENDIX

Appendix 19

Appendix--Chemical characteristics of water from wells in Duval County, Florida that were sampled in July–August 1992[Well locations are shown in figure 3. All dissolved constituent concentrations are in milligrams per liter, except as indicated. Specific conductance is in microsiemenis in milligrams per liter as calcium carbonate. Aquifer: U, Upper Floridan aquifer; L, Lower Floridan aquifer; B, both Upper and Lower Floridan aquifers. Depths are less than]

Well identifier

Well

number

Specific

conductance Calcium Magnesium Sodium Potassium Alkalinity Chloride Sulfate Bromide 

300622081284701 1 662 -- -- -- -- -- 19.0 -- 0.00 300756081335001 2 703 64 36.0 16.0 3.5 118 17.0 210.0 0.11 300812081390801 3 364 33 20.0 7.8 3.1 102 7.8 64.0 0.27 300820081354001 4 580 -- -- -- -- -- 18.0 -- 0.00 300824081305401 5 610 73 33.0 15.0 3.0 145 18.7 180.0 0.00 301032081380401 6 418 35 20.0 10.0 2.5 117 10.0 77.0 0.16 301144081413801 7 366 34 17.0 7.9 2.6 112 7.8 57.0 0.14 301152081423001 8 348 34 17.0 7.8 1.8 110 7.4 51.0 0.00 301157081374301 9 712 -- -- -- -- -- 23.0 -- 0.00 301255081371001 10 527 48 27.0 12.0 2.4 121 12.0 130.0 0.12 301305081321901 11 797 80 35.0 16.0 3.1 129 35.0 210.0 0.00 301333081324101 12 719 73 30.0 13.0 2.7 137 17.0 200.0 0.16 301335081355001 13 1,390 140 52.0 46.0 3.5 129 160.0 280.0 0.56 301337081354801 14 718 83 36.0 16.0 3.1 128 35.0 -- 0.26 301339081433401 15 334 34 15.0 6.3 2.2 105 6.9 50.0 0.15 301339081531203 16 296 31 13.0 6.2 1.6 104 5.9 33.0 0.00 301347081421801 17 378 38 17.0 7.3 2.5 111 7.6 -- 0.12 301409081330401 18 649 58 31.0 13.0 2.9 129 18.0 160.0 0.00 301415081284801 19 608 84 33.0 13.0 2.3 145 17.0 180.0 0.19 301450081485001 20 470 51 16.0 11.0 1.6 184 8.1 1.2 0.00 301537081441901 21 373 -- -- -- -- -- 7.0 -- 0.00 301551081415701 22 360 32 19.0 8.9 2.4 104 27.0 -- 0.16 301552081234301 23 637 61 34.0 16.0 1.9 133 17.0 160.0 0.00 301604081234601 24 697 62 35.0 13.0 2.2 123 12.0 190.0 0.00 301604081361501 25 883 -- -- -- -- -- 86.0 -- 0.37 301607081301001 26 620 71 28.0 12.0 1.7 142 15.0 160.0 0.00 301620081234201 27 630 58 36.0 14.0 2.0 129 12.0 180.0 0.00 301639081330802 28 917 84 38.0 28.0 2.8 139 98.0 170.0 0.26 301648081431801 29 475 -- -- -- -- -- 9.7 -- 0.00 301657081233301 30 955 81 35.0 53.0 2.2 149 120.0 140.0 0.00 301704081233401 31 1,275 97 42.0 86.0 2.4 147 220.0 150.0 0.00 301715081300001 32 611 59 31.0 19.0 2.5 139 14.0 150.0 0.00 301716081234301 33 716 67 32.0 25.0 2.0 148 48.0 140.0 0.00 301725081305002 34 684 72 29.0 18.0 1.9 141 43.0 140.0 0.00 301740081361001 35 1,255 -- -- -- -- -- 220.0 -- 0.44 
20 The Distribution of Bromide in Water in the Floridan Aquifer System, Duval County, Northeastern Florida 301743081303501 36 817 82 33.0 40.0 2.2 141 103.0 150.0 0.00 

301743081304701 37 785 83 33.0 27.0 2.5 141 73.0 160.0 0.10 301743081362301 38 1,308 110 42.0 85.0 3.2 140 230.0 160.0 0.39 301744081363301 39 986 -- -- -- -- -- 130.0 -- 0.00 301752081360501 40 672 -- -- -- -- -- 27.0 -- 0.11 301801081384302 41 641 -- -- -- -- -- 14.0 -- 0.00 301817081374901 42 600 70 26.0 11.0 1.8 138 14.0 140.0 0.16 301839081392101 43 583 63 24.0 11.0 2.5 136 13.0 -- 0.30 301846081240201 44 633 62 30.0 16.0 1.7 143 26.0 140.0 0.13 301852081234201 45 399 56 28.0 13.0 2.4 101 13.0 170.0 0.00 301852081240301 46 627 64 34.0 12.0 1.9 130 14.0 170.0 0.00 301900081342801 47 299 15 12.0 24.0 1.5 39 59.0 -- 0.00 301902081394601 48 590 68 26.0 10.0 2.6 125 11.2 150.0 0.28 301907081420901 49 587 66 26.0 10.0 2.3 131 12.0 140.0 0.00 301913081534601 50 360 34 17.0 11.0 2.3 139 12.0 28.0 0.25 301955081280601 51 629 64 24.0 14.0 2.7 143 15.0 160.0 0.00 301955081485701 52 468 42 22.0 11.0 3.0 132 12.0 77.0 0.28 301957081342301 53 798 -- -- -- -- -- 86.0 -- 0.00 302007081353201 54 836 92 34.0 30.0 2.2 145 98.0 120.0 0.00 302008081242101 55 630 61 35.0 11.0 1.8 120 11.0 180.0 0.00 302015081384501 56 518 55 21.0 12.0 1.9 151 16.0 86.0 0.00 302022081393501 57 639 -- -- -- -- -- 12.0 -- 0.00 302032081321001 58 757 73 28.0 31.0 1.9 143 78.0 110.0 0.00 302037081455301 59 305 96 18.0 23.0 3.2 196 20.8 140.0 0.15 302112081384701 60 380 30 19.0 12.0 1.9 121 15.0 47.0 0.00 302113081322301 61 632 67 25.0 18.0 1.8 129 47.0 120.0 0.18 302120081361801 62 541 63 23.0 13.0 1.7 149 21.0 87.0 0.17 302120081363001 63 549 64 23.0 14.0 1.7 151 22.0 91.0 0.00 302122081274001 64 573 66 23.0 13.0 1.8 149 16.0 120.0 0.00 302130081411802 65 563 -- -- -- -- -- 13.0 -- 0.00 302137081240001 66 624 70 26.0 13.0 2.2 142 15.0 150.0 0.00 302138081292301 67 664 66 27.0 16.0 2.4 146 27.8 130.0 0.00 302142081330701 68 602 69 25.0 13.0 1.7 144 15.0 140.0 0.00 302227081435001 69 613 -- -- -- -- -- 11.0 -- 0.00 302232081292901 70 1,041 -- -- -- -- -- 170.0 -- 0.29 

Appendix--Chemical characteristics of water from wells in Duval County, Florida that were sampled in July–August 1992—Continued

[Well locations are shown in figure 3. All dissolved constituent concentrations are in milligrams per liter, except as indicated. Specific conductance is in microsiemens is in milligrams per liter as calcium carbonate. Aquifer: U, Upper Floridan aquifer; L, Lower Floridan aquifer; B, both Upper and Lower Floridan aquifers. Depths are less than]

Well identifier

Well

number

Specific

conductance Calcium Magnesium Sodium Potassium Alkalinity Chloride Sulfate Bromide 
Appendix 21

302236081401501 71 497 -- -- -- -- -- 13.0 -- 0.00 302300081295101 72 551 63 23.0 13.0 1.6 148 16.0 110.0 0.00 302317081330401 73 561 57 23.0 16.0 2.2 151 26.5 90.0 0.00 302323081324801 74 520 55 22.0 14.0 1.9 151 16.7 86.0 0.00 302339081254702 75 580 -- -- -- -- -- 14.0 -- 0.00 302344081340101 76 525 57 23.0 14.0 2.0 152 19.0 85.0 0.00 302345081261301 77 532 54 24.0 14.0 2.2 154 17.7 88.0 0.00 302351081390201 78 564 62 23.0 12.0 2.1 143 14.0 120.0 0.00 302357081311101 79 536 56 24.0 14.0 2.0 152 21.0 83.0 0.00 302405081314301 80 530 54 23.0 14.0 2.0 154 21.0 83.0 0.00 302422081244401 81 568 56 22.0 20.0 2.3 154 32.6 82.0 0.00 302426081312801 82 948 76 33.0 55.0 2.4 151 129.0 130.0 0.00 302428081313101 83 528 54 24.0 13.0 2.0 153 19.0 84.0 0.30 302428081493401 84 462 46 25.0 16.0 2.5 190 14.6 50.0 0.00 302502081321001 85 520 52 23.0 14.0 2.3 159 19.0 77.0 0.00 302502081330701 86 546 64 25.0 16.0 1.9 161 25.0 80.0 0.00 302503081332001 87 524 60 23.0 13.0 1.9 157 20.0 82.0 0.00 302505081331001 88 552 64 26.0 15.0 1.8 155 26.0 86.0 0.00 302511081331201 89 466 45 21.0 14.0 1.8 148 20.0 58.0 0.00 302514081393701 90 516 54 22.0 14.0 1.8 160 19.0 76.0 0.00 302519081331501 91 533 52 22.0 15.0 1.8 162 23.0 77.0 0.00 302536081331301 92 699 69 29.0 28.0 1.8 152 67.0 100.0 0.00 302538081253101 93 1,642 100 51.0 130.0 4.0 153 310.0 180.0 0.34 302538081392501 94 532 -- -- -- -- -- 20.0 -- 0.00 302557081253101 95 1,718 -- -- -- -- -- 340.0 -- 0.51 302608081354901 96 678 73 30.0 23.0 1.7 161 55.0 100.0 0.00 302608081354903 97 525 59 25.0 15.0 1.6 161 18.0 75.0 0.00 302616081413901 98 562 51 22.0 13.0 1.8 164 18.0 65.0 0.00 302618081261001 99 483 46 17.0 14.0 2.0 152 18.7 63.0 0.00 302647081460201 100 565 59 27.0 16.0 1.9 160 23.0 98.0 0.00 302724081244801 101 500 -- -- -- -- -- 20.0 -- 0.00 302738081290001 102 550 55 25.0 15.0 1.9 154 22.0 -- 0.00 302805081341701 103 545 56 25.0 16.0 1.6 166 21.0 85.0 0.00 302919081314601 104 553 50 24.0 15.0 1.8 152 21.0 92.0 0.00 303216081433301 105 598 60 29.0 15.0 1.9 149 24.0 120.0 0.11 

Appendix--Chemical characteristics of water from wells in Duval County, Florida that were sampled in July–August 1992—Continued

[Well locations are shown in figure 3. All dissolved constituent concentrations are in milligrams per liter, except as indicated. Specific conductance is in microsiemenis in milligrams per liter as calcium carbonate. Aquifer: U, Upper Floridan aquifer; L, Lower Floridan aquifer; B, both Upper and Lower Floridan aquifers. Depths are less than]

Well identifier

Well

number

Specific

conductance Calcium Magnesium Sodium Potassium Alkalinity Chloride Sulfate Bromide 
22 The Distribution of Bromide in Water in the Floridan Aquifer System, Duval County, Northeastern Florida 303458081364001 106 586 58 29.0 16.0 1.7 153 22.0 110.0 0.00 

SUMMARY: Number of wells 106 86 86 86 86 86 106 80 106 

Median 580 61 25 14 2.0 144 19 115 <0.10 Maximum 1,718 140 52 130 4.0 196 340 280 .56 Minimum 185 15 12 6.2 1.5 39 5.9 1.2 <.10 

Appendix--Chemical characteristics of water from wells in Duval County, Florida that were sampled in July–August 1992—Continued [Well locations are shown in figure 3. All dissolved constituent concentrations are in milligrams per liter, except as indicated. Specific conductance is in microsiemens 

is in milligrams per liter as calcium carbonate. Aquifer: U, Upper Floridan aquifer; L, Lower Floridan aquifer; B, both Upper and Lower Floridan aquifers. Depths are less than] Well identifier Well num- ber Specific conduct- ance Calcium Magnesium Sodium Potassium Alkalinity Chloride Sulfate Bromide