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EVT: Sampling and Analysis > Midterm > Flashcards

Midterm Flashcards

1
Q

Which sampling method has least amount of bias

A

Random

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2
Q

Selection of appropriate sampling points requires consideration of what variables?

A

Spatial and Temporal

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3
Q

What are 3 main sampling approaches?

A

Random, systematic random, and judgemental

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4
Q

Random Sampling

A

Every sample of population has an equal chance of being selected. Tradeoff: very expensive yet unbiased.

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5
Q

Systematic Random Sampling

A

Divide population into homogeneous groups (decrease variance), then divide this into cells using a cartesian grid. Tradeoff: slightly larger bias. Used in: land-based sites, drill wells and biological sampling.

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6
Q

Semi-variogram

A

Tool used to determine the number of samples required for a program to be considered statistically random. Theory: Increasing distance between samples increases randomness (decreases correlation).

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7
Q

Key factors to consider when deciding a sampling strategy are…

A

Type of pollutant, sampling device and end use of data.

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8
Q

DQO Steps

A
  1. State problem
  2. Identify decision
  3. Identify inputs to decision
  4. Define study boundaries
  5. Develop a decision rule
  6. Specify limits on decision errors
  7. Optimize design for obtaining data
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9
Q

Major activities of DQO (2)

A

Identify:

  1. Question that needs to be answered
  2. Amount of uncertainty tolerated
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10
Q

Types of Sampling Programs (3)

A

Intuitive, statistical, and protocol

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11
Q

Intuitive Sampling Program

A

Based on judgement of experts.

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12
Q

Statistical Sampling Program

A

Independent of judgement.

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13
Q

Protocol Sampling Program

A

Follow legally mandated plans.

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14
Q

Grab Samples

A

Discrete. Useful in looking at a specific time and locations, particularly for analytes at maximum concentrations. Assumes no change over distance.

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15
Q

Types of Control Site (2)

A

Area and local

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16
Q

Area Control Site

A

In same area as sampling site, not adjacent to it.

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17
Q

Local Control Site

A

Adjacent to sampling site, immediately up-gradient. Preferable because closer to sampling site, so more likely of being identical (except for analyte).

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18
Q

Which type of sample would best represent a heterogeneous sample?

A

Composite

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19
Q

Three examples of field measurements are…

A

pH, conductivity, and DO

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20
Q

What 3 areas should be included in a SOP of a sampling plan?

A

Preservation, labelling and sample collection.

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21
Q

What QC sample is used to measure the precision of a sampling technique?

A

Duplicate Sample

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22
Q

What type of QC sample is used to detect an error caused by presence of contamination by improperly cleaned sampling equipment?

A

Sampling Equipment Blank

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23
Q

Three types of error in sampling and analysis process?

A

Design phase, implementation and lab analysis.

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24
Q

Design Phase (Definition)

A

Identification of where and how to collect samples.

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25
Q

Implementation (Definition)

A

Sampling technique, storage and transfer of samples.

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26
Q

Lab Analysis (in relation to error)

A

Best controlled source of error.

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27
Q

What are 4 compartments in soil where individual pollutants may be found?

A

Air, water, soil, and free product.

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28
Q

Different types of sampling plans (2)?

A

Exploratory/surveillance and monitoring/assessment.

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29
Q

Name three of the different natural physical and chemical mechanisms that influence the migration of pollutants.

A

Climate, respiration, time, surface area, and composition.

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30
Q

Air Cycle

A

plants -> O2 -> humans -> CO2 -> plants

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31
Q

Water Cycle

A

Purification system: sun heats the ocean -> water evaporates and collects in clouds -> clouds release water as rain during precipitation

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32
Q

Soil Cycle

A

Organic matter -> organisms break down

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33
Q

What are the three partitioning mechanisms?

A

Volatilization, dissolution, and sorption.

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34
Q

Horizontal Stratification

A

Migration of pollutant from the source of contamination.

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35
Q

Vertical Stratification

A

Dependant on nature of pollutant (ex., density).

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36
Q

Sources of Interference

A

Sample collection, transport and storage, preservation, and analysis.

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37
Q

What questions should be asked before sampling?

A

Is the area homogenous or heterogeneous? Is there horizontal or vertical stratification?

38
Q

NAPL

A

Non-Aqueous Phase Liquids

39
Q

How do LNAPLs act in groundwater?

A

Spill travels through soil -> to groundwater -> floats on water table surface.

40
Q

How do DNAPLS act in groundwater?

A

Spill sinks to bedrock -> collect in bottom in pools

41
Q

Biomagnification

A

Increase of pollutant concentration as you move up the food chain. Pollutant exceeds the concentration expected at equilibrium between an organism and its environment.

42
Q

List partitioning mechanisms in increasing volatility.

A

Sorption < Dissolution < Volatilization

43
Q

Why preserve samples?

A

Chemical compounds can become unstable with changes in/exposure to: time, light, air, and temperature.

44
Q

List three methods of sample preservation.

A

Chemical addition, temperature control, and using the correct container.

45
Q

Problem vs. Preservation Technique: Volatilization (3)

A

Minimize headspace and agitation, keep sample cool and don’t use vacuum filtration.

46
Q

Problem vs. Preservation Technique: Adsorption (2)

A

Choose correct sample bottles (add acid if necessary) or do field tests and preserve quickly.

47
Q

Problem vs. Preservation Technique: Diffusion (2)

A

Proper container (want inertness, line with teflon coating) and minimize headspace.

48
Q

Diffusion

A

Migration of chemicals from higher to lower concentrations.

49
Q

Problem vs. Preservation Technique: Precipitation (1 + how)

A

Use acid, add immediately after sampling or else extreme loss of analyte will occur.

50
Q

Problem vs. Preservation Technique: Biodegradation

A

Store at reduced temperature or extreme pH

51
Q

Biodegradation

A

Analytes can degrade over time due to interaction with biological components in sample.

52
Q

Holding Time

A

Length of time a sample can be stored after collection and preservation without significantly altering analytical results.

53
Q

Matrix

A

Surrounding substance within which something else originated/develops/is contained.

54
Q

Interferences

A

Cause error in measurement.

55
Q

Types of Interferences

A

Additive, subtractive, and multiplicative.

56
Q

Additive Interference

A

Generate a signal that adds to the analyte signal.

57
Q

Subtractive Interference

A

Generate a signal the takes away from analyte signal (reacts with reagents which prevents reaction with analyte).

58
Q

Multiplicative Interference

A

Add to analyte signal without generating a signal of its own. This changes slope.

59
Q

Volatilization

A

A dissolved substance is vaporized.

60
Q

Sources of Interference (4)

A

Matrix, analyte, other compounds, and reagent.

61
Q

How to mitigate interferences? (What + examples)

A

Quality Control: Accuracy and precision, quality control charting, spikes, audits, and EMS).

62
Q

Bioconcentration

A

Intake and retention by respiration from water in aquatic systems, or from air in terrestrial systems.

63
Q

Bioaccumulation

A

Build up of toxins in an organism from environment and diet.

64
Q

Ways an organism can uptake pollutants (3).

A

Uptake is by all possible means, including contact, respiration, and ingestion.

65
Q

Finish this sentence: Preservation begins in the…

A

Field and continues in the lab.

66
Q

Field Preservation Techniques (3)

A

Chemical addition, temperature, and correct container.

67
Q

Lab Preservation Techniques (3)

A

Holding time, refrigeration, and exposure + sectioning.

68
Q

Goal of preservation?

A

Minimize physical and chemical changes to the sample before analysis.

69
Q

Sections of a Sampling Plan. (14)

A
  1. Project scope and objective.
  2. Type of plan.
  3. Site ID and map.
  4. Sample source.
  5. Number and type of samples.
  6. Frequency of sampling.
  7. Sampling approach.
  8. Collection method.
  9. Analytical parameters and lab methods.
  10. Field measurements
  11. Field QC
  12. Sampler
  13. Post sampling activities
  14. Documentation
70
Q

DQO

A

Data Quality Objectives. Objectives that outline the overall uncertainty that can be tolerated in a project.

DQOs are balanced against cost of sampling and analysis, there is an inverse relationship between cost and uncertainty.

71
Q

Sampling Plan Components: Project Scope and Objective

A

What is included and excluded, qualitative vs quantitative.

72
Q

Sampling Plan Components: Type of Plan

A

Surveillance/exploratory or monitoring/assessment.

73
Q

Sampling Plan Components: Number and Type of Samples

A

Test/control, grab/composite/discrete, duplicate/split, and local/area

74
Q

Control Sample

A

Determine background levels, in terms of composition and concentration. Collected first.

75
Q

Composite Sample

A

Multiple grabs, same location but at different times or different locations at same time. Variation is lost, less information.

76
Q

Sampling Plan Components: Analytical Parameters

A

Primary or secondary analytes, lab methods (sensitivity, sample mass).

77
Q

QA

A

Quality Assurance. A system of monitoring, evaluating, and documenting that lends proof of analysis.

78
Q

QA Examples

A

Education and evaluation of employees, result reporting.

79
Q

Quality Management

A

Made up of QA, QC, and Qassess

80
Q

Quality Management Examples

A

Maintain Quality System Manual (QSM), planning and implementation of QA/QC program.

81
Q

QC

A

Quality Control. The day-to-day monitoring of accuracy and precision at the lab level.

82
Q

QC Examples

A

SOPs, blanks, calibrations, spikes, QC charting

83
Q

Qassess

A

Quality Assessment. Evaluate QA and QC to see how well they are operating.

84
Q

Qassess Examples

A

External and internal programs, accreditation, audits, Certification Reference Materials (CRMs), blinds, round robins.

85
Q

Accuracy

A

Proximity to the true value. Determined by comparing value against a QC sample of known value.

86
Q

Precision

A

How close results are to each other. Determined by comparing duplicate results.

87
Q

Bias

A

Judgemental analysis, influencing results. Seen as trending from true value.

88
Q

What are the two types of error.

A

Systemic and indeterminant (random).

89
Q

Systemic Error

A

Inaccuracies are in the same direction, affecting data average.

90
Q

Indeterminant/Random Error

A

Statistical fluctuations that add variability, but don’t affect average.

91
Q

Spikes

A

Used to evaluate changes in analyte response from sampling to result. Created by adding a known amount of analyte to a matrix then analyzing.

EVT: Sampling and Analysis (1 decks)

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