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Air, Water and Land Pollution Chapter 2: Basics of Environmental Sampling and Analysis Copyright © 2010 by DBS.

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Presentation on theme: "Air, Water and Land Pollution Chapter 2: Basics of Environmental Sampling and Analysis Copyright © 2010 by DBS."— Presentation transcript:

1 Air, Water and Land Pollution Chapter 2: Basics of Environmental Sampling and Analysis Copyright © 2010 by DBS

2 Contents Essential Analytical and Organic Chemistry Essential Environmental Statistics Essential Hydrology and Geology Essential Knowledge of Environmental Regulations

3 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry Concentration Units 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

4 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry 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 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 ppm = 1000 ppb] 1 ppb * 1,000 = 1 ppt

5 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry Concentration Units 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)

6 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry Concentration Units Chemicals in gaseous samples mass analyte/total volume of sample volume analyte/total volume of sample NOT equivalent! 1 mg/m 3 ≠ 1 ppm v,1 μg/m 3 ≠ 1 ppb v, 1 ng/m 3 ≠ 1 ppt v

7 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry 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 SO 2 at 0 °C will contain less than 1 μg m -3 SO 2 if heated to 25 °C

8 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry 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 Similarly: concentration (µg m -3 ) = concentration (ppb) x MW 24.5 concentration (ng m -3 ) = concentration (ppt) x MW 24.5

9 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry Conversion (at normal temperature of 20 ºC and 1 atm.) from w/v to v/v: concentration (ppmv) = concentration (mg m -3 ) x 24.0 Molar mass Note: At STP of 273 K (0 C) the molar volume is 22.4 Similarly: concentration (ppbv) = concentration (μg m -3 ) x 24.0 Molar mass concentration (pptv) = concentration (ng m -3 ) x 24.0 Molar mass

10 Question Maximum contaminant level (MCL) according to the US EPA for 2,3,7,8-TCDD (dioxin) in drinking water is 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: mg/L = 3 x mg/L = 3 x ppm Since 1 ppm = 10 6 ppt 3 x ppm x 10 6 ppt/ppm = 0.03 ppt Convert to molarity: mg/L x 1 g/1000mg x 1 mol/322 g = 9.32 x mol/L = 9.32 x M

11 Question Maximum contaminant level (MCL) according to the US EPA for 2,3,7,8-TCDD (dioxin) in drinking water is 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 mol/L x x molecules/mol = 5.61 x molecules / L 56.1 billion dioxin molecules per liter

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13 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry Common Organic Pollutants and Their Properties 7 million known chemicals ~ 100,000 present in the environment Few hundred considered environmental pollutants

14 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry Common Organic Pollutants and Their Properties ’priority’ chemicals – selection based on quantity, persistence, bioacculmulation, transport potential, toxicity etc. 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 Example 2: ‘the priority pollutant metals’ Ag, As, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, Tl, Zn

15 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry Common Organic Pollutants and Their Properties US EPA lists 127 priority pollutants in water (see appendix B) Grown from 5 in 1940 Find graph showing no. of pollutants added to list every year (if exists!)

16 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry Common Organic Pollutants and Their Properties US EPA lists 127 priority pollutants (112 organic and 15 inorganic) in water

17 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry 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 chloroethyl vinyl ether (mixed) chloronaphthalene 021 2,4, 6-trichlorophenol 022 Parachlorometa cresol 023 Chloroform (trichloromethane) 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 chlorophenyl phenyl ether 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 051 Chlorodibromomethane 052 Hexachlorobutadiene 053 Hexachloromyclopentadiene 054 Isophorone 055 Naphthalene 056 Nitrobenzene nitrophenol nitrophenol 059 2,4-dinitrophenol 060 4,6-dinitro-o-cresol 061 N-nitrosodimethylamine 062 N-nitrosodiphenylamine 063 N-nitrosodi-n-propylamin 064 Pentachlorophenol 065 Phenol 066 Bis(2-ethylhexyl) phthalate 067 Butyl benzyl phthalate 068 Di-N-Butyl Phthalate 069 Di-n-octyl phthalate 070 Diethyl Phthalate 071 Dimethyl phthalate 072 1,2-benzanthracene (benzo(a) anthracene 073 Benzo(a)pyrene (3,4-benzo-pyrene) 074 3,4-Benzofluoranthene (benzo(b) fluoranthene) ,12-benzofluoranthene (benzo(b) fluoranthene) 076 Chrysene 077 Acenaphthylene 078 Anthracene 079 1,12-benzoperylene (benzo(ghi) perylene) 080 Fluorene 081 Phenanthrene 082 1,2,5,6-dibenzanthracene (dibenzo(,h) anthracene) 083 Indeno (,1,2,3-cd) pyrene (2,3-o-pheynylene pyrene) 084 Pyrene 085 Tetrachloroethylene 086 Toluene 087 Trichloroethylene 088 Vinyl chloride (chloroethylene) 089 Aldrin 090 Dieldrin 091 Chlordane (technical mixture and metabolites) 092 4,4-DDT 093 4,4-DDE (p,p-DDX) 094 4,4-DDD (p,p-TDE) 095 Alpha-endosulfan 096 Beta-endosulfan 097 Endosulfan sulfate 098 Endrin 099 Endrin aldehyde 100 Heptachlor 101 Heptachlor epoxide (BHC-hexachlorocyclohexane) 102 Alpha-BHC 103 Beta-BHC 104 Gamma-BHC (lindane) 105 Delta-BHC (PCB-polychlorinated biphenyls) 106 PCB–1242 (Arochlor 1242) 107 PCB–1254 (Arochlor 1254) 108 PCB–1221 (Arochlor 1221) 109 PCB–1232 (Arochlor 1232) 110 PCB–1248 (Arochlor 1248) 111 PCB–1260 (Arochlor 1260) 112 PCB–1016 (Arochlor 1016) 113 Toxaphene 114 Antimony 115 Arsenic 116 Asbestos 117 Beryllium 118 Cadmium 119 Chromium 120 Copper 121 Cyanide, Total 122 Lead 123 Mercury 124 Nickel 125 Selenium 127 Thallium 126 Silver 128 Zinc 129 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) As of Jan 2010

18 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry Common Organic Pollutants and Their Properties Important pollutants can be divided into nine categories: 1. Element: Metals (Cu, Zn, Pb, Cd, Ni, Hg, Cr) and metalloids (As, Se) 2. Inorganic compounds: CN, CO, NOx, asbestos 3. Organo-metallic and metalloid compounds: tetraethyl lead and tributyl tin 4. Hydrocarbons: saturated and unsaturated aliphatic and aromatic HC’s including BTEX compounds (benzene. Toluene, ethylbenzene and xylene) and polycyclic aromatic HC’s (PAHs) 5. Oxygenated compounds: Alcohol, aldehyde, ether, organic acid, ester, ketone, and phenol 6. Nitrogen compounds: amine, amide, nitroaromatic HCs, and nitrosamines 7. Halogenated HCs: aliphatic and aromatic halogenated HCs, polychlorinated biphenyls (PCBs), and dioxins 8. Organosulfur compounds: thiols, thiophenes, mercaptans, and many pesticides 9. Phosphorus compounds: many pesticides

19 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry

20 Analytical Precision, Accuracy, and Recovery Accuracy is the degree of agreement of a measured value with the true or expected value % Recovery = Analytical value x 100 / True value 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 %

21 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry Analytical Precision, Accuracy, and Recovery Precision is the degree of mutual agreement among repeated measurements Precision measures the variation amongst measurements Expressed as standard deviation (s) Also relative standard deviation (RSD)

22 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry Detection Limit and Quantitation Limit 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 Where t is obtained from “Student’s t value table” corresponding to t 0.98 and degree of freedom df = n - 1, where n = no. measurements (see appendix C2) (e.g. n = 7, t = 3.143) MDLs are specific to a given matrix, method, instrument, and analytical technique, is not the lowest concentration that can be accurately measured EPA uses practical quantitation limit (PQL) as lowest concentration measured (2-10 x MDL)

23 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry Standard Calibration Curve Calibration curve, or standard curve is a plot of instrument response vs. concentration y = ax + b Where y = instrument response, x = concentration of chemical, a = calibration sensitivity Essential for all quantitative analysis using spectrometric and chromatographic methods Use Excel!

24 Basics of Environmental Sampling and Analysis Essential Analytical and Organic Chemistry Standard Calibration Curve

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26 Basics of Environmental Sampling and Analysis Essential Environmental Statistics Measurements of Central Tendency and Dispersion Characterized of a sample from a population based on (i) center and (ii) dispersion Center is measured by the mean, median and the mode Mean (Arimetic and Geometric):

27 Basics of Environmental Sampling and Analysis Essential Environmental Statistics Measurements of Central Tendency and Dispersion 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, 3 rd position is 4) (x n/2 + x n/2+1 )/2 if n is even (e.g. 1, 2, 4, 5, 7, 8…n = 6, n/2 = 6/2 = 3 rd position, n/2 + 1 is 4 th position, average of these two numbers (4+5)/2 is 4.5) Mode is the value that occurs most frequently, e.g. 1, 1, 2, 2,2, 9,10,11, 11 the mode is 2

28 Basics of Environmental Sampling and Analysis Essential Environmental Statistics Measurements of Central Tendency and Dispersion Data variation or dispersion is a characteristic of how spread out data points are Described by variance, standard deviation, and range Range is the difference between maximum and minimum values Population variance is defined as: Sample variance (s 2 ) is calculated: Where N = total population size, n = sample size, µ = population mean

29 Basics of Environmental Sampling and Analysis Essential Environmental Statistics Measurements of Central Tendency and Dispersion Variance is important because variances are added to find the overall variance for a process

30 Basics of Environmental Sampling and Analysis Essential Environmental Statistics Understanding Probability Distributions Normal Distribution – symmetrical and bell-shaped distribution of data Environmental data are usually skewed and must be transformed using logarithms Defined by the mean (μ) and SD (σ) – must be standardized as follows:

31 Basics of Environmental Sampling and Analysis Essential Environmental Statistics Understanding Probability Distributions The background concentration of Zn in soils of Houston is normally distributed with a mean of 66 mg/kg and a SD of 5 mg/kg (a) what percentage of the soil samples will have concentration < 72 mg/kg? For x = 72, z = ( )/5 = 1.2 For x = 61, z = (61- 66)/5 = -1 (a) P(x<72) = P(z<1.2) = P(-∞

32 Basics of Environmental Sampling and Analysis Essential Environmental Statistics Understanding Probability Distributions The background concentration of Zn in soils of Houston is normally distributed with a mean of 66 mg/kg and a SD of 5 mg/kg (b) what percentage will have a concentration > 72 mg/kg? (c) what percentage will have a concentration between 61 and 72 mg/kg? For x = 72, z = ( )/5 = 1.2 For x = 61, z = (61- 66)/5 = -1 (b) P(x>72) = P(z>1.2) = 1 - P(z<1.2) = 1 – = (11.51 %) (c) P(61

33 Basics of Environmental Sampling and Analysis Essential Environmental Statistics Student’s t Distribution Identical to normal distribution when n is large Describes distribution of the mean (x-bar) rather than x Where s / √n is the standard error of the mean Often used to calculate the confidence interval (CI)

34 Basics of Environmental Sampling and Analysis Essential Environmental Statistics Student’s t Distribution Also known as ‘sample size’ equation: n ≥ (zs/E) 2 Where E = error, z = z-value, n = number of samples For 95 % confidence level and n = ∞, z = 1.96

35 Basics of Environmental Sampling and Analysis Essential Environmental Statistics Type I and II Errors: False Positive and False Negative Not covered

36 Basics of Environmental Sampling and Analysis Essential Environmental Statistics Detection of Outliers 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.) Possible remedies –Replace (do-over) –Remove (using statistical test – z-test, Grubbs’ test, Dixon’s test) –Retain

37 Basics of Environmental Sampling and Analysis Essential Environmental Statistics Analysis of Censored Data e.g. following data were collected: 2.5, < 1.0, 1.9, 2.6 μg/L What is mean and SD? Does the water meet the regulatory standard of 2.0 μg/L? A value of <1.0 is called ‘censored data’ Impossible to compute a mean and SD Solution? Deletion, altering to a value of 0 are two ways which are not recommended EPA recommends replacement with detection limit (DL)

38 Basics of Environmental Sampling and Analysis Essential Environmental Statistics Analysis of Spatial and Time Series Data Temporal – concentration vs. time Spatial – concentration vs. x and y Averaging temporal or spatial data to obtain a mean and SD is not a statistically sound approach – not random

39 Basics of Environmental Sampling and Analysis Essential Environmental Statistics

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41 Basics of Environmental Sampling and Analysis Essential Hydrology and Geology Stream Water Flow and Measurement 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 = (W 1 x D 1 x V 1 ) + (W 2 x D 2 x V 2 ) + (W 3 x D 3 x V 3 ) + … (W n x D n x V n ) Where W = width, D = depth

42 Basics of Environmental Sampling and Analysis Essential Hydrology and Geology Groundwater Flow in Aquifers 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

43 Basics of Environmental Sampling and Analysis Essential Hydrology and Geology Textural Classes –Particle size distribution: gravel (> 5 mm) sand ( mm) silt ( mm) clay (<0.002 mm)

44 Basics of Environmental Sampling and Analysis Essential Hydrology and Geology Groundwater Flow in Aquifers Most groundwater within 300 ft of surface, may be as deep as 2000 ft

45 Basics of Environmental Sampling and Analysis Essential Hydrology and Geology Groundwater Flow in Aquifers 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

46 Basics of Environmental Sampling and Analysis Essential Hydrology and Geology Groundwater Wells Used for: –Supply - Domestic, agricultural or industrial –Recovery – pumping contaminated water from waste sites –Injection – e.g. natural gas recovery –Monitoring – water quality

47 Basics of Environmental Sampling and Analysis Essential Hydrology and Geology Groundwater Wells 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

48 Basics of Environmental Sampling and Analysis Essential Hydrology and Geology Groundwater Wells Type depends on confined or unconfined aquifer

49 Basics of Environmental Sampling and Analysis Essential Knowledge of Environmental Regulations

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51 References Fiefield, F.W. and Haines, P.J. (2000) Environmental Analytical Chemistry, 2 nd 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 Keith, L.H. and Telliard, W.A. (1979) Priority pollutants I – a perspective view. Environmental Science and Technology, Vol. 13, No. 4, pp Weiner, E. (2000) Applications of Environmental Aquatic Chemistry. Taylor and Francis.

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