Q: Is well purging mandatory for field sampling?
A: Yes. HJ 1019—2019 requires purging the well until water quality parameters stabilize or a specified volume of water is removed; additionally, disturbances such as air-lifting or aeration within the well must be avoided.
Q: Should bailers be phased out?
A: No. Standards still retain the bailer as an option for shallow-water-table or small-diameter monitoring wells—it is inexpensive, lightweight, and depth-unrestricted. However, it is sensitive to operator technique and prone to significant VOC loss; caution is advised when using it for projects where VOCs are the primary target.
Q: Why are sampling flow rate requirements stricter than those for purging?
A: Purging rates range from 100 to 500 mL/min, whereas sampling rates generally should not exceed 100 mL/min (with a maximum of 500 mL/min) per HJ 1019—2019. The sampling phase directly determines sample quality; changes in dissolved oxygen or VOC loss caused by disturbance cannot be rectified once the sample reaches the laboratory.
Q: Can it replace a low-flow bladder pump?
A: They are not equivalent. Bladder pumps utilize a power source for continuous pumping to achieve low-disturbance sampling. In contrast, the AML917 is a manual, static, discrete-depth sampler that fills via hydrostatic pressure and is retrieved after a single sampling event. Their operational methods, continuity, and applicable scenarios differ.
Q: When is well purging considered complete?
A: According to HJ 1019—2019, purging can conclude when at least three of the following parameters—pH (±0.1), temperature (±0.5°C), electrical conductivity (±10%), and turbidity (≤10 NTU)—remain stable across three consecutive measurements.
Q: How is sampling depth accuracy ensured?
A: The steel cable features integrated depth markings, allowing for positioning based on the target stratum reading prior to deployment. For stratified sampling and sampling from thin aquifers, this level of precision is more critical than portability.
