Air, Water and Land Pollution
Chapter 2:
Basics of Environmental Sampling and
Analysis
Copyright © 2010 by DBS
Contents
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Essential Analytical and Organic Chemistry
Essential Environmental Statistics
Essential Hydrology and Geology
Essential Knowledge of Environmental Regulations
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Concentration Units
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Chemicals in Liquid Samples
mass analyte/total volume of sample
mass/volume (m/v) unit:
mg/L, μg/L, ng/L etc.
For freshwater or liquids with density = 1.0 g/mL
1 mg/L = 1 ppm, 1 μg/L = 1 ppb, 1 ng/L = 1 ppt
ppm = 1000 ppb = 1,000,000 ppt
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
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ppm, ppb, etc. (assumes pollutant has same density as water, ρ = 1.00 g mL-1)
e.g. show that 1 mg/L = 1 ppm
 1 g pollutant
1 mg pollutant /L of H 2O
 1000 mg
  1 L H 2O  1 g pollutant
 =
 
 1 part per million
6
  1000 g H 2O  10 g H 2O
1 mg/L = 1 ppm
1 μg/L = 1 ppb
1 ng/L = ppt
Conversions:
1 pph (%) * 10,000 = ppm
1 ppm * 1,000 = 1 ppb
1 ppb * 1,000 = 1 ppt
[1 ppm = 1000 ppb]
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Concentration Units
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Chemicals in solid samples
mass analyte/total mass of sample
mass/mass (m/m) unit:
mg/kg, μg/g etc.
1 mg/kg = 1 ppm, 1 μg/kg = 1 ppb, 1 ng/kg = 1 ppt
Mass should be specified as either wet or dry
mg/kg (dry) = mg/kg (wet)/(1 - % moisture)
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Concentration Units
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Chemicals in gaseous samples
mass analyte/total volume of sample
volume analyte/total volume of sample
NOT equivalent!
1 mg/m3 ≠ 1 ppmv,
1 μg/m3 ≠ 1 ppbv,
1 ng/m3 ≠ 1 pptv
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
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Not independent of temperature or pressure, volume of air will change, mass of
pollutant won’t change
e.g. air containing 1 μg m-3 SO2 at 0 °C will contain less than 1 μg m-3 SO2 if heated
to 25 °C
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
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Conversion (at standard temperature of 25 ºC and 1 atm.) from m/v to v/v:
concentration (mg m-3) = concentration (ppm) x MW
24.5
Note: At 273 K (0 ºC) the molar volume is 22.4, at 293 K (20 ºC) molar volume is 24.0
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Similarly:
concentration (µg m-3) = concentration (ppb) x MW
24.5
concentration (ng m-3) = concentration (ppt) x MW
24.5
Question
Maximum contaminant level (MCL) according to the US EPA for 2,3,7,8-TCDD
(dioxin) in drinking water is 0.00000003 mg/L. Convert this concentration to ppt and
molarity (M). What is the equivalent number of dioxin molecules per liter of water?
The molecular weight of dioxin is 322 g/mol
Convert to ppt:
0.00000003 mg/L = 3 x 10-8 mg/L = 3 x 10-8 ppm
Since 1 ppm = 106 ppt
3 x 10-8 ppm x 106 ppt/ppm = 0.03 ppt
Convert to molarity:
0.00000003 mg/L x 1 g/1000mg x 1 mol/322 g = 9.32 x 10-14 mol/L
= 9.32 x 10-14 M
Question
Maximum contaminant level (MCL) according to the US EPA for 2,3,7,8-TCDD
(dioxin) in drinking water is 0.00000003 mg/L. Convert this concentration to ppt and
molarity (M). What is the equivalent number of dioxin molecules per liter of water?
The molecular weight of dioxin is 322 g/mol
Convert to number of molecules:
= 9.32 x 10-14 mol/L x 6.022 x 1023 molecules/mol = 5.61 x 1010 molecules / L
56.1 billion dioxin molecules per liter
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Common Organic Pollutants and Their Properties
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7 million known chemicals
~ 100,000 present in the environment
Few hundred considered environmental pollutants
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Common Organic Pollutants and Their Properties
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’priority’ chemicals – selection based on quantity, persistence, bioacculmulation,
transport potential, toxicity etc.
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Example 1: ‘the dirty dozen’ – 12 persistent organic pollutants (POPs) consisting of 9
pesticides and 2 by-products
Aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, hexachlorobenzene,
mirex, toxaphene, PCBs, dioxins and furans
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Example 2: ‘the priority pollutant metals’
Ag, As, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, Tl, Zn
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Common Organic Pollutants and Their Properties
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US EPA lists 127 priority pollutants in water
(see appendix B)
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Grown from 5 in 1940
Find graph showing no. of pollutants
added to list every year (if exists!)
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Common Organic Pollutants and Their Properties
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US EPA lists 127 priority pollutants (112 organic and 15 inorganic) in water
001 Acenaphthene
002 Acrolein
003 Acrylonitrile
004 Benzene
005 Benzidine
006 Carbon tetrachloride (tetrachloromethane)
007 Chlorobenzene
008 1,2,4-trichlorobenzene
009 Hexachlorobenzene
010 1,2-dichloroethane
011 1,1,1-trichloreothane
012 Hexachloroethane
013 1,1-dichloroethane
014 1,1,2-trichloroethane
015 1,1,2,2-tetrachloroethane
016 Chloroethane
018 Bis(2-chloroethyl) ether
019 2-chloroethyl vinyl ether (mixed)
020 2-chloronaphthalene
021 2,4, 6-trichlorophenol
022 Parachlorometa cresol
023 Chloroform (trichloromethane)
024 2-chlorophenol
025 1,2-dichlorobenzene
026 1,3-dichlorobenzene
027 1,4-dichlorobenzene
028 3,3-dichlorobenzidine
029 1,1-dichloroethylene
030 1,2-trans-dichloroethylene
031 2,4-dichlorophenol
032 1,2-dichloropropane
033 1,2-dichloropropylene (1,3-dichloropropene)
034 2,4-dimethylphenol
035 2,4-dinitrotoluene
036 2,6-dinitrotoluene
037 1,2-diphenylhydrazine
038 Ethylbenzene
039 Fluoranthene
040 4-chlorophenyl phenyl ether
041 4-bromophenyl phenyl ether
042 Bis(2-chloroisopropyl) ether
043 Bis(2-chloroethoxy) methane
044 Methylene chloride (dichloromethane)
045 Methyl chloride (dichloromethane)
046 Methyl bromide (bromomethane)
047 Bromoform (tribromomethane)
048 Dichlorobromomethane
049 REMOVED
050 REMOVED
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Chlorodibromomethane
Hexachlorobutadiene
Hexachloromyclopentadiene
Isophorone
Naphthalene
Nitrobenzene
2-nitrophenol
4-nitrophenol
2,4-dinitrophenol
4,6-dinitro-o-cresol
N-nitrosodimethylamine
N-nitrosodiphenylamine
N-nitrosodi-n-propylamin
Pentachlorophenol
Phenol
Bis(2-ethylhexyl) phthalate
Butyl benzyl phthalate
Di-N-Butyl Phthalate
Di-n-octyl phthalate
Diethyl Phthalate
Dimethyl phthalate
1,2-benzanthracene (benzo(a) anthracene
Benzo(a)pyrene (3,4-benzo-pyrene)
3,4-Benzofluoranthene (benzo(b) fluoranthene)
11,12-benzofluoranthene (benzo(b) fluoranthene)
Chrysene
Acenaphthylene
Anthracene
1,12-benzoperylene (benzo(ghi) perylene)
Fluorene
Phenanthrene
1,2,5,6-dibenzanthracene (dibenzo(,h) anthracene)
Indeno (,1,2,3-cd) pyrene (2,3-o-pheynylene pyrene)
Pyrene
Tetrachloroethylene
Toluene
Trichloroethylene
Vinyl chloride (chloroethylene)
Aldrin
Dieldrin
Chlordane (technical mixture and metabolites)
4,4-DDT
4,4-DDE (p,p-DDX)
4,4-DDD (p,p-TDE)
Alpha-endosulfan
Beta-endosulfan
Endosulfan sulfate
Endrin
Endrin aldehyde
Heptachlor
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Heptachlor epoxide (BHC-hexachlorocyclohexane)
Alpha-BHC
Beta-BHC
Gamma-BHC (lindane)
Delta-BHC (PCB-polychlorinated biphenyls)
PCB–1242 (Arochlor 1242)
PCB–1254 (Arochlor 1254)
PCB–1221 (Arochlor 1221)
PCB–1232 (Arochlor 1232)
PCB–1248 (Arochlor 1248)
PCB–1260 (Arochlor 1260)
PCB–1016 (Arochlor 1016)
Toxaphene
Antimony
Arsenic
Asbestos
Beryllium
Cadmium
Chromium
Copper
Cyanide, Total
Lead
Mercury
Nickel
Selenium
Thallium
Silver
Zinc
2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD)
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
As of Jan 2010
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Common Organic Pollutants and Their Properties
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Important pollutants can be divided into nine categories:
1.
2.
3.
4.
Element: Metals (Cu, Zn, Pb, Cd, Ni, Hg, Cr) and metalloids (As, Se)
Inorganic compounds: CN, CO, NOx, asbestos
Organo-metallic and metalloid compounds: tetraethyl lead and tributyl tin
Hydrocarbons: saturated and unsaturated aliphatic and aromatic HC’s including
BTEX compounds (benzene. Toluene, ethylbenzene and xylene) and polycyclic
aromatic HC’s (PAHs)
Oxygenated compounds: Alcohol, aldehyde, ether, organic acid, ester, ketone, and
phenol
Nitrogen compounds: amine, amide, nitroaromatic HCs, and nitrosamines
Halogenated HCs: aliphatic and aromatic halogenated HCs, polychlorinated
biphenyls (PCBs), and dioxins
Organosulfur compounds: thiols, thiophenes, mercaptans, and many pesticides
Phosphorus compounds: many pesticides
5.
6.
7.
8.
9.
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Analytical Precision, Accuracy, and Recovery
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Accuracy is the degree of agreement of a measured value with the true or expected
value
% Recovery = Analytical value x 100 / True value
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True value (conc.) is rarely known, typically determined by spiking a sample with a
known standard
% Recovery on spike = Spiked sample value – Sample value x 100 %
Spiked value
% recovery should be close to 100 %
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Analytical Precision, Accuracy, and Recovery
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Precision is the degree of mutual agreement among repeated measurements
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Precision measures the variation amongst measurements
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Expressed as standard deviation (s)
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Also relative standard deviation (RSD)
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Detection Limit and Quantitation Limit
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Method detection limit (MDL) – minimum concentration that can be measured and
reported with 99 % confidence that the analyte concentration is greater than zero
Analyte-free matrix (reagent water or lab-grade sand) is spiked with the target analyte
at 3-5 x the estimated MDL, sample is measured 7 times
MDL = s x t
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Where t is obtained from “Student’s t value table” corresponding to t0.98 and degree of
freedom df = n - 1, where n = no. measurements (see appendix C2)
(e.g. n = 7, t = 3.143)
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MDLs are specific to a given matrix, method, instrument, and analytical technique, is
not the lowest concentration that can be accurately measured
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EPA uses practical quantitation limit (PQL) as lowest concentration measured
(2-10 x MDL)
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Standard Calibration Curve
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Calibration curve, or standard curve is a plot of instrument response vs. concentration
y = ax + b
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Where y = instrument response, x = concentration of chemical, a = calibration
sensitivity
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Essential for all quantitative analysis using spectrometric and chromatographic
methods
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Use Excel!
Basics of Environmental Sampling and Analysis
Essential Analytical and Organic Chemistry
Standard Calibration Curve
Basics of Environmental Sampling and Analysis
Essential Environmental Statistics
Measurements of Central Tendency and Dispersion
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Characterized of a sample from a population based on (i) center and (ii) dispersion
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Center is measured by the mean, median and the mode
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Mean (Arimetic and Geometric):
Basics of Environmental Sampling and Analysis
Essential Environmental Statistics
Measurements of Central Tendency and Dispersion
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Median is the middle value:
X(n+1) if n is odd
2
(e.g. 1, 2, 4, 5, 7…n = 5, middle position is 6/2 = 3, 3rd position is 4)
(xn/2 + xn/2+1)/2 if n is even
(e.g. 1, 2, 4, 5, 7, 8…n = 6, n/2 = 6/2 = 3rd position, n/2 + 1 is 4th position, average of
these two numbers (4+5)/2 is 4.5)
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Mode is the value that occurs most frequently, e.g. 1, 1, 2, 2,2, 9,10,11, 11 the mode
is 2
Basics of Environmental Sampling and Analysis
Essential Environmental Statistics
Measurements of Central Tendency and Dispersion
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Data variation or dispersion is a characteristic of how spread out data points are
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Described by variance, standard deviation, and range
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Range is the difference between maximum and minimum values
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Population variance is defined as:
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Sample variance (s2) is calculated:
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Where N = total population size, n = sample size, µ = population mean
Basics of Environmental Sampling and Analysis
Essential Environmental Statistics
Measurements of Central Tendency and Dispersion
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Variance is important because variances are added to find the overall variance for a
process
Basics of Environmental Sampling and Analysis
Essential Environmental Statistics
Understanding Probability Distributions
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Normal Distribution – symmetrical and bell-shaped distribution of data
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Environmental data are usually skewed and must be transformed using logarithms
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Defined by the mean (μ) and SD (σ) – must be standardized as follows:
Basics of Environmental Sampling and Analysis
Essential Environmental Statistics
Student’s t Distribution
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Identical to normal distribution when n is large
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Describes distribution of the mean (x-bar) rather than x
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Where s / √n is the standard error of the mean
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Often used to calculate the confidence interval (CI)
Basics of Environmental Sampling and Analysis
Essential Environmental Statistics
Student’s t Distribution
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Also known as ‘sample size’ equation:
n ≥ (zs/E)2
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Where E = error, z = z-value, n = number of samples
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For 95 % confidence level and n = ∞, z = 1.96
Basics of Environmental Sampling and Analysis
Essential Environmental Statistics
Detection of Outliers
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Outliers are observations that appear to be inconsistent with the results
Possible causes
– Mistakes (sampling, analytical, instrument, key-punch, transcribing errors)
– Inherent spatial/temporal variation (malfunctioning pollutant control devices,
spills, hot spots etc.)
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Possible remedies
– Replace (do-over)
– Remove (using statistical test – z-test, Grubbs’ test, Dixon’s test)
– Retain
Basics of Environmental Sampling and Analysis
Essential Environmental Statistics
Analysis of Censored Data
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e.g. following data were collected: 2.5, < 1.0, 1.9, 2.6 μg/L
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What is mean and SD?
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Does the water meet the regulatory standard of 2.0 μg/L?
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A value of <1.0 is called ‘censored data’
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Impossible to compute a mean and SD
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Solution? Deletion, altering to a value of 0 are two ways which are not recommended
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EPA recommends replacement with detection limit (DL)
Basics of Environmental Sampling and Analysis
Essential Environmental Statistics
Analysis of Spatial and Time Series Data
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Temporal – concentration vs. time
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Spatial – concentration vs. x and y
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Averaging temporal or spatial data to obtain a mean and SD is not a statistically
sound approach – not random
Basics of Environmental Sampling and Analysis
Essential Hydrology and Geology
Stream Water Flow and Measurement
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Stream flow (cfs) is important, Q = V x A
Where V = velocity of stream, A = cross sectional area of stream
Since flow varies across the stream multiple measurements must be made to
determine the average flow
Q = (W1 x D1 x V1) + (W2 x D2 x V2) + (W3 x D3 x V3) + … (Wn x Dn x Vn)
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Where W = width, D = depth
Basics of Environmental Sampling and Analysis
Essential Hydrology and Geology
Groundwater Flow in Aquifers
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Flow is very slow
Must be determined using wells (not visible)
Aquifer is typically soil or rock with a high porosity
Grain size dictates where and how fast water will flow
Basics of Environmental Sampling and Analysis
Essential Hydrology and Geology
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Textural Classes
– Particle size distribution:
gravel (> 5 mm)
sand (0.075-5 mm)
silt
(0.075-0.002 mm)
clay (<0.002 mm)
Basics of Environmental Sampling and Analysis
Essential Hydrology and Geology
Groundwater Flow in Aquifers
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Most groundwater within 300 ft of surface, may be as deep as 2000 ft
Basics of Environmental Sampling and Analysis
Essential Hydrology and Geology
Groundwater Flow in Aquifers
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Saturated zone – water is held in soil pores
Porosity determines the groundwater storage capacity - the ratio of void space to total
volume
Permeability (hydraulic conductivity) is a measure of the aquifers ability to transmit
water = change in head (water level) per unit distance
Large permeability = less resistance to flow
Basics of Environmental Sampling and Analysis
Essential Hydrology and Geology
Groundwater Wells
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Used for:
– Supply - Domestic,
agricultural or industrial
– Recovery – pumping
contaminated water from
waste sites
– Injection – e.g. natural gas
recovery
– Monitoring – water quality
Basics of Environmental Sampling and Analysis
Essential Hydrology and Geology
Groundwater Wells
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Casing – steel or PVC
Well screen – screens coarse
particles, allows water to enter
Filter pack – screens fine
materials
Annular seal – cemented to
surface to prevent
infiltration/leakage
Basics of Environmental Sampling and Analysis
Essential Hydrology and Geology
Groundwater Wells
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Type depends on confined or
unconfined aquifer
Basics of Environmental Sampling and Analysis
Essential Knowledge of Environmental Regulations
References
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Fiefield, F.W. and Haines, P.J. (2000) Environmental Analytical Chemistry, 2nd
Edition. Blackwell Science, Malden, MA.
Helsel, D.R. (1990) Less than obvious: Statistical treatment of data below the
detection limit. Environmental Science and Technology, Vol. 24, No. 12, pp.
1766-1774.
Keith, L.H. and Telliard, W.A. (1979) Priority pollutants I – a perspective view.
Environmental Science and Technology, Vol. 13, No. 4, pp. 416-423.
Weiner, E. (2000) Applications of Environmental Aquatic Chemistry. Taylor
and Francis.