Groundwater sampling
Groundwater quality monitoring usually collects instantaneous water samples.
For well water where the water level needs to be measured, the groundwater level should be measured first before sampling.
3. Water samples collected from Wells must be carried out after thorough pumping. The volume of water pumped must not be less than twice the volume of water in the well. The sampling depth should be 0.5 meters below the groundwater surface to ensure that the water sample can represent the quality of the groundwater.
4. For closed production Wells, samples can be taken from the water release valve of the pump room's outlet pipe during water pumping. Before sampling, all the water in the pumping pipe should be drained completely.
5. For self-gushing spring water, samples can be taken at the center of the water flow at the gushing outlet. When collecting water from the fountain, the water that has been stagnant in the suction pipe should be drawn out. After the fresh water is replaced, sampling should be conducted again.
Before sampling, except for the monitoring items of five-day biochemical oxygen demand, organic matter and bacteria, the sampler and water sample container should be rinsed 2 to 3 times with sampling water.
7. For the determination of dissolved oxygen, five-day biochemical oxygen demand and volatile and semi-volatile organic pollutants, water samples must be filled to the brimeter of the container without leaving any gaps at the top during sampling. However, for samples prepared for freezing preservation, the container must not be filled to the bridle; otherwise, after freezing, the container may crack due to the expansion of the water sample's volume. The water samples for determining dissolved oxygen should be fixed on site after collection. After the bottle stoppers are closed, they need to be sealed with water.
8. Water samples for the determination of five-day biochemical oxygen demand, sulfides, petroleum, heavy metals, bacteria, radioactivity and other items should be collected separately. Drain all the stored water.
9. After collecting water samples, immediately add the preservative as required, tightly seal the water sample container, and attach the label. The label design can be based on the specific conditions of each station, but generally should include the monitoring well number, sampling date and time, monitoring items, and sampler, etc.
Before the sampling is completed, the sampling plan, sampling records and water samples should be checked. If there are any errors or missed samples, re-sampling or supplementary sampling should be carried out immediately.