do you know where your drinking water comes from? an overview of hydrogeology and health jean m....
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Do you know where your drinking water comes from?
Do you know where your drinking water comes from?
An overview of hydrogeology and health
Jean M. BahrUniversity of Wisconsin -
Madison
An overview of hydrogeology and health
Jean M. BahrUniversity of Wisconsin -
Madison
Sometimes the sources are obvious
Sometimes the storage systems are obvious, but the sources are not
Reservoirs of fresh water on Earth
Reservoir % Fresh % Unfrozen Atmosphere 0.04 0.2Ice 73.9 ---Lakes + Streams 0.36 1.4Ground water 25.7 98.4
Residence time – 11 days
1000 to >10,000 yrs weeks to decades
decades to 1000s of yrs
The hydrologic cycle
Water used in the US in 2000 for public domestic supply
(serves 85% of population)
Two main sources: ground water and surface water
Figures from USGS Circular 1268http://pubs.usgs.gov/circ/2004/circ1268/
63% 37%
Self supply for remaining 15% of population(almost entirely ground water)
Figure from USGS Circular 1268
Northfield Minnesota is supplied by 4 wells with depths ranging from 365 to 410 feet – so YOU are drinking ground water
http://www.ci.northfield.mn.us/cityhall/departments/publicworks/water
Some Ground Water BasicsSome Ground Water Basics
Common misconceptions
about ground water
Ground water is primarily water held in “pores”
Micropores in sandstones and carbonates Virtually no pores in granite
Macropores in limestone, basalt, crystalline rocks
Major types of geologic materials and associated porosity
Unconsolidated sediment
Carbonaterocks
(e.g. limestone)
Volcanicrocks (basalt)
Fractured igneousand metamorphic rocks
Sandstone and carbonate
Extent and thickness of the Jordan Sandstone
Zones of Subsurface Water
Soil water in the Unsaturated Zone (air and water in pores)Ground water below the “water table” (in the Saturated Zone)
Some Water Quality BasicsSome Water Quality Basics
Health-based standards for drinking water quality
Non-enforceable “Secondary Standards” based on cosmetic and
aesthetic effects
Another important property
pH: a measure of hydrogen ions in solution,commonly referred to as “acidity”
Acidic
Basic
Neutral
Comparison of drinking water and other standards
Human Drinking WaterTDS < 500 ppmpH 6-5-8.5Chloride < 250 ppmSulfate < 250 ppmIron < 0.3 ppm
Dairy CowsTDS < 4000 ppmpH 6-5-8.5Chloride < 1600 ppm
TroutTDS – wide rangepH 6-5-8.0Hardness 10-400Oxygen >5 ppmTemp. optimum 50-60oF
TDS – measure of “salinity” (but not only sodium and chloride)
“fresh” <2000 ppm
35,000 ppm< 10 ppm
“brackish” 2000-20,000 ppm
“hypersaline brine” >100,00 ppm
What do we find dissolved in ground water?
Precipitation chemistry controlled by interaction with the atmosphere
Resulting water composition • Dissolved nitrogen• Dissolved oxygen• Dissolved carbon dioxide
• carbonic acid• pH around 5
Earth’s atmosphere
pH of infiltrating water is further altered in the unsaturated zone
Microbial degradation of organic carbon consumes dissolved oxygen and produces CO2
Water entering the saturated zone has low pH, enhancing mineral dissolution, and may be “reducing” (low dissolved oxygen), which can enhance solubility of trace metals
Continued chemical evolution along ground water flow paths
Ground water composition reflects abundance of elements in geologic materials mineral solubility
Saline ground water in coastal areas or in deep basin “brines”
Examples of naturally occurring constituents with health effectsExamples of naturally occurring constituents with health effects
• Fluoride• Arsenic • Radium and radon• Water “hardness”• Naturally occurring organics
• Fluoride• Arsenic • Radium and radon• Water “hardness”• Naturally occurring organics
Effects of fluoride deficiency and excess
Combined effects of poor nutrition and excess F
Understanding of the fluorine cycle aids in anticipating F concentrations in ground water
Areas of high F in Arizona and California associated with extensional basins
Arsenic poisoning in Bangladesh
Source: MPCA Ground Water Monitoring and Assessment Program
Arsenic in Minnesota and Wisconsin Wells
Source: Wisconsin Dept. of Nat. Resources
Arsenic in Wisconsin’s Fox Valley
Arsenic bearing sulfide minerals at the top of the St. Peter Sandstone
O2
O2
Ground water use lowers water table and exposes sulfide minerals to oxygen
Pumping in the Fox Valley and near Green Bay has lowered the water table and
introduced oxygen to the aquifer
The City of Green Bay now uses Lake Michigan water delivered by a pipeline
ASRWater
ASRWater
SurficialAquifer
ConfiningUnit
ASR Storage
Zone
LowerConfining Unit
Storage Recovery
Proposal to use ASR (aquifer storage recovery) as an alternative to surface reservoirs
Green Bay Well 10
medium
shallow
deep
Monitoring intervals
Borehole flowmeter logging to identify possible preferential flow zones
0
50
100
150
200
250
300
0 4 8 12 16 20 24
Weeks of Storage
Ars
en
ic (
ug
/L)
Deep
Medium
Shallow
Arsenic concentrations during storage phase of Green Bay pilot test
0
50
100
150
200
250
300
0 50 100 150 200 250 300
Percent Recovery
Ars
en
ic (
ug
/L)
ASR Well
Medium
Shallow
Deep
Arsenic concentrations during recovery phase of Green pilot test
Lower, but still problematic, concentrations of arsenic found in ground water from glacial deposits and shallow bedrock of SE Wisconsin
Health effects of chronic exposure to low concentrations are not well established
Tara Root
Core hole at Woods Schoolnear Lake Geneva WICore hole at Woods Schoolnear Lake Geneva WI
Measurable, but not dramatically high, concentrations of arsenic through most of the core below upper sand and gravel
Sampling, field and laboratory analyses from private wells
Arsenic released from iron oxides where oxygen is depleted – below the Foxhollow Till
Products of uranium decay
From USGS Circular 1156
Radon and radium in WI ground water associated with trace concentrations of uranium in the St. Peter Sandstone
Calcium + magnesium concentrations:“hardness”
Hard water “stops heart attacks”Drinking hard water may protect against heart disease, researchers have claimed.
Researchers from the Geographical Survey of Finland looked at 19,000 men who had suffered heart attacks. They found for every unit increase in water hardness, there was a 1% decrease in the risk of having a further attack. Writing in the Journal of Epidemiology and Community Health, the researchers said the findings explained regional variations in heart attack rates.
Correlation between natural organics in drinking water and Balkan endemic
nephropathy (kidney disease)
High nitrate concentrations also occur in ground water of the affected area
Lignite mine in affected areaBEN Areas
Anthropogenic contaminants from “point” and “non-point” sources
Anthropogenic contaminants from “point” and “non-point” sources
Non-point human, animal and agricultural sources of nitrate
Point sources generate a contaminant “plume”
Eau ClaireWell Field
TCE plume, 1992
Large plumes from small sources
Some contaminants are “retarded” by interactions with aquifer solids
Retarded transport of contaminants that adsorb to aquifer solids
A “conservative”
contaminant
Slower migration of plumes, but also slower removal by pumping
Non-aqueous phase liquid (NAPL) contaminants move separately from
ground water
LNAPL e.g. gasoline
DNAPLe.g. chlorinated solvents
Emerging contaminants – Pharmaceuticals and personal care products
Compounds detected in ground water samples collected by the USGS from selected
sites in Minnesota, 2000-2002
Modified from Canter and Knox, 1985
Fate of emerging contaminants from on-site waste disposal systemsJeff Wilcox
Sampling from conventional and advanced septic systems
Source: Univ. of Minnesota Extension
MoundDistribution Systems
Source: Converse and Tyler, 1987
Aerobic Treatment Units
Compounds detected in 15 septic systems
Compound (Frequency) Max Conc. (ng/L)
Caffeine (15) 134,000
Paraxanthine (13) 79,000
Acetaminophen (10) 1,000,000
Fluoxetine (2) 280
-estradiol (1) 190
Chlorpropamide (1) 140
Estrogenic activity (e-screen) detected in 14 samples
Laboratory experiments to investigate contaminant transport
Multiple breakthrough curves
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0Time (days)
C/C
o
Bromide Carbamazepine Caffeine Fluoxetine
1. Chlorpropamide
2. Carisoprodol
3. Warfarin
4. Carbamazepine
5. Paraxanthine
6. Estriol
7. Estrone
8. Ethynyl estradiol
9. Acetaminophen
10. Caffeine
11. B-estradiol
Fenofibrate
Fluoxetine
Relative mobility
Decreasing mobility
Increasingmobility
Eau ClaireWell Field
TCE plume, 1992
The challenge of estimating health riskThe challenge of estimating health risk
Risk analysis using RISC4 Software
Maximum concentrations in 1985 when added to
the Superfund List
Maximum Concentrations in 1985
Child Adult
8 x 10- 5
Of the contaminants of interest, only TCE has a quantified carcinogenic risk
Source of health risk data
Risks for Concentrations in EC2, 1991
Cancer
1 x 10- 5
Injestion Skin Shower Inhalation
Calculated life-time carcinogenic risks for 1991 concentrations in drinking water are on the order of 6 x 10-6 for adults (assuming 9 years of exposure).How many excess cancers would be expected in Eau Claire if all residents drank water for 9 years with concentrations of contaminants found in monitoring well EC2 in 1991?Eau Claire population in 2000 census was 61,704
61,704 x 6 x 10-6 = 0.4Less than one case of excess cancer - would not be expected to show up in epidemiologic studies!
Difficulty in detecting health effects in populations
Some future (global) challengesSome future (global) challenges
• Other emerging contaminant issues– antibiotic resistant microbes– synergistic or antagonistic effects of multiple
contaminants• Increasing demand for water by increasing
population with potential health effects from– wastewater treatment and re-use– desalination– shifts from ground water to surface water or
from one aquifer source to another– artificial recharge and aquifer storage recovery
• Sea level rise and saltwater intrusion
• Other emerging contaminant issues– antibiotic resistant microbes– synergistic or antagonistic effects of multiple
contaminants• Increasing demand for water by increasing
population with potential health effects from– wastewater treatment and re-use– desalination– shifts from ground water to surface water or
from one aquifer source to another– artificial recharge and aquifer storage recovery
• Sea level rise and saltwater intrusion