Sampling & Sample Preparation (13) Flashcards
Why do we sample? (2)
• It’s because it’s not economically feasible to analyse large amounts of material.
• To possibly get a good representation of the whole material.
Sample?
= a fraction of the whole material for analysis.
Monitoring points? (4)
● Waste streams & air emissions.
● Quality of the receiving water & air quality.
● Efects of solid waste disposal on land, groundwater & surface water.
● Soil for nutrients or pesticides.
Sampling plan components? (5)
• Sampling duration.
• Sampling locations.
• Sampling frequency.
• Sampling parameters.
• Sampling procedures.
Sampling duration types? (2)
• Regulatory studies.
• Pilot studies.
Regulatory studies?
= sampling is ongoing & stipulated by water laws.
Why do Regulatory studies occur? (2)
• To show continued compliance with criteria.
• To monitor the ongoing influence of discharges on the receiving environment.
Pilot studies?
= sampling that is a once off targeted approach & occurs only when there’s a pollution incident that needs investigation.
When do pilot studies occur? (2)
• When the variability of a wastewater stream or receiving environment is uncertain.
• When there’s a pollution incident that needs investigation.
Pro of regulatory studies?
Helps detect trends.
Sampling locations criteria? (3)
• Sample in areas where a representative sample can be collected.
• Areas that are.safe to access.
• Areas where water is well mixed.
Why sample from areas with well mixed water?
To ensure a homogenous sample is collected and easily identifiable for later sampling.
Why should you establish permanent sampling locations?
To ensure that representative samples can be compared over time.
What is sampling frequency determined by? (2)
• By the variability of discharge.
• By the objectives of the plan.
What do the sampling parameters depend on? (2)
• On the contaminants present.
• On the requirements of the revelant authority.
Types of sampling procedures? (2)
• Grab samples.
• Composite samples.
Grab samples?
= samples that provide a “snapshot” of the water quality at a particular time & location.
When are grab samples used?
When you need to determine water/wastewater constituents at a particular time.
Grab samples requirement & why?
High sampling frequency to show the nature of effluent over time.
Composite samples?
= a single mixed obtained from the mixing of multiple grab samples.
Why are Composite samples preferred over grab samples?
It’s because they are more representative of what is happening in the water during the day & offer an “average” view of the effluent.
When can composite samples be used? (4)
• When the average water quality characteristics are needed over a given period of time.
• When the distribution of analytes within the stream is random.
• When the variability within the stream is low.
• When the determination of the loads of analytes is required.
What do we mean when we say integrity of samples?
= when samples need to be representative of the body from which it was taken.
What happens if the integrity of the sample is altered?
Information gained from analysis could be misleading, resulting in polluting of the resource.
Processes that can affect integrity? (3)
• Contamination.
• Physical & Chemical changes.
• Biological processes.
Contamination of a sample?
= occurs when foreign substances are introduced into it through sampling equipment not being sterilized before use.
Result of sample contamination?
The sample may have characteristics that are not representative of the in situ conditions.
Physical & Chemica changes in a sample?
= any process that changes the physical/chemical nature of a sample.
