Water Chemistry Sample Collection
Why are we taking water chemistry samples?
Agencies and professionals collect water samples when they are interested on the presence of nutrients, metals or other chemicals in the water (i.e. nitrate, phosphate, ammonia, dissolved nutrients, metals - zinc, copper, lead, iron). These tests may be used to track the presence of contaminants, understand the biology and chemistry of water, or determine amounts and concentrations. Water samples are collected in a standardized way to reduce the risk of contamination. Metals and nutrients require preservative to suspend their activity and sometimes require filtration to capture the dissolved forms.
State guidelines on proper sample collection and processing ensure consistency between sample collections by different monitors. Tests for water chemistry vary widely between projects. When collecting samples, it is important to be familiar with the project specific procedures which may be found in the Sample Analysis Plan (SAP). The SAP will include detailed information about the sample locations, parameters to test for, special requirements and holding time required to return the samples to the lab.
The samples should be representative of the stream by collecting in the thalweg (deepest flow or main flow) and collected following Utah DWQ Standard Operating Procedure. Also, PDF quick instructions here.
Sample Collection Instructions:
Ensure you have all the equipment necessary; check the SAP or with the project coordinator for project specific requirements. You will be provided with a kit in advance that will include sample bottles and data sheets.
Label all sample bottles with date, time, site and initials. Label when you arrive at your site. Read each bottle and note any that have acid preservation or are filter bottles.
- Bottles with acid preservation: do not rinse and use caution not to overfill.
- Bottles for filtration: Do not fill these with native water. A transfer bottle will be used to collect water for these samples.
When using a transfer bottle (for filtered samples), rinse three times with native water between each site.
Collection by wading, when safe:
- Wade out to collect the sample in the thalweg (deepest flow or main flow of the stream). If the thalweg is too deep, find another area where the water is flowing and appears to be well mixed.
- Wait until disturbed sediment has moved down stream before collecting a sample.
- Do not rinse the bottles unless you know they do not contain preservative. Bottles containing preservative are labeled as such. If using a transfer bottle, triple rinse it with stream water.
- Remove first sample bottle cap. Avoid touching the inside of bottle cap, container or lip.
- Reach forward with the bottle opening facing upstream and quickly plunge the bottle below the surface avoiding any surface scum, floating debris or the bottom of the stream.
- Be careful not to overfill the bottle unless otherwise directed by the lab (for volatile organic compound analysis). For bottles with prefilled with preservative, overfilling would cause a loss of preservative, so leave some headspace in the bottle and immediately replace the cap.
- Repeat with all sample bottles and return to shore.
Collection from bank edge, when water is too deep or fast to wade safely:
- Use a dip sampler from bank to reach into the main flow.
- If flow is too strong, sample may be collected by hand directly from the bank in a flowing, well-mixed area.
- Follow the same instructions as wading.
Filtering, done as needed. If you are not filtering skip to post collection handling.
- Gently invert the sample you collected for filtering to mix thoroughly and place intake tubing in the sample container.
- Flush the filter holder and tubing with 500mLof sample water to rinse using either the GeoPump or hand pump.
- Unscrew the filter holder to access the filter stage, being careful not to touch the inside.
- Using clean forceps, load the filter holder with an unused membrane filter (0.45 µm), being careful not to touch the filter.
- You may use a glass-fiber pre-filter if there is visible turbidity in the sample. The pre-filter should be “upstream”of the membrane filter.
- Screw the filter holders back together.
- Remove caps from sample bottles, turn on the pump and hold the filter holder over the sample bottle without touching it to the bottle and the filter stream fills the bottles.
- Continuously swirl the raw water sample during filtration to ensure homogeneity.
- If the filter clogs before filling the bottle, stop the pump, remove and replace used filter with a new one.
- Be sure not to overfill the preserved sample bottles and leave some headspace. Overfilling prepreserved bottles will cause a loss of preservative.
- Stop the pump and replace the bottle cap.
- Remove and discard used filter and rinse apparatus with 500mL DI water.
- Keep all samples on ice in a cooler out of the light until delivered to the lab. Make sure to deliver the samples within the holding time. If unsure what that is, refer to the SOP, SAP or check with the project coordinator.
- At the end of the day, clean the sampling equipment by soaking the filter holders and GeoPump tubing in a solution of Liqui-nox overnight followed by light scrubbing and rinse with DI water in the morning.
- Label bottles, and note filtered and preserved bottles
- Collect sample from thalweg, standing downstream
- Collect from bank if water is too deep or dangerous
- Filter immediately following sampling
- Do not mix caps
- Store samples on wet ice
Find the approved Utah DWQ SOP for "Collection of Water Chemistry Sample" here.