1.1 Water sampling methods
As you'll see later, a number of field tests simply involve dipping a probe directly into the water body being tested and taking a reading, but others require a sample to be removed for testing.
Correct sampling technique in accordance with standard procedures is essential to ensure fit-for-purpose data for the customer; all information pertaining to the sampling procedure must be logged.
Briefly explain what you understand by 'fit for purpose'.
As analytical scientists you are providing a service to your client. You must match the service you provide (in this case the data you obtain in the field) to the requirements of the client.
Let's take a step back. Even before removing a sample, there are observations that should be made about a water body, whether it's a stream, a lake or even an ocean. These qualitative observations should include what the water looks like, its colour or clarity, which will get you thinking about any pre-treatment measures that may be needed.
When you've taken a sample, because the concentration of certain chemical species (or microbes) at a particular site may change with time, it's not just where the sample was taken from that should be logged, but also when.
Note that apparatus is also available for continuous measurement by electrochemical methods of many parameters, such as dissolved oxygen, electrical conductivity and pH. A probe is located at a strategic point (such as the inlet of a water treatment plant) and linked to a data logger, a portable microprocessor controlled device which stores acquired data in its memory for later collection and interpretation. You will look at this further in Section 6.