A field method for the detection of elemental mercury in sink traps

Identification and detection of mercury is critical in the protection of safety, health and the environment and has been an issue in many research laboratory facilities. Mercury can affect laboratory demolition and renovation activities, contaminate industrial wastewater and be spilled or released requiring cleanup. A quick and accurate field method for detecting the presence and distribution of mercury that has accumulated in laboratory sink traps and piping over many years, defined as “legacy” mercury, is presented. This method uses the detection of mercury vapors above sinks as an indicator of the amount of elemental mercury in solution within sink or plumbing traps (P-traps). An Ohio Lumex RA-915 Light Mercury Analyzer with a detection limit of 0.2 ug/m3 was used to detect mercury vapor in existing laboratories. Vapor extraction from the headspace was facilitated by using an in-line air filter to seal the trap and to protect the instrument from gross contamination while the sample was being taken. When sink drain design excluded the direct application of an in-line air filter, the sampling assembly was modified to include an inverted funnel. The head space directly above a sink trap was drawn into the Lumex RA-915 Light for real time measurements of mercury vapor. Each sample event takes about 2 minutes to complete. At each sink where mercury vapor was detected, trap contents were removed and analyzed for total mercury and/or dissolved mercury to determine if any correlation between vapor concentrations in the headspace and mercury concentration in water could be established. A standardized procedure and checklist was developed to maximize sampling consistency and reliability. Results from the total mercury analysis of sink trap contents confirmed Lumex RA-915 Light sample results. The quantity of mercury in a sink trap is positively correlated with the amount of mercury vapor measured. Once identified, mercury-containing sink traps can be selectively cleaned or removed.