Impact of collection container material and holding times on sample integrity for mercury and methylmercury in water

Abstract

Mercury (Hg) and methylmercury (MeHg) concentrations in streamwater can vary on short timescales (hourly or less) during storm flow and on a diel cycle; the frequency and timing of sampling required to accurately characterize these dynamics may be difficult to accomplish manually. Automated sampling can assist in sample collection; however use has been limited for Hg and MeHg analysis due to stability concerns during extended storage times. We examined the viability of using automated samplers with disposable low-density polyethylene (LDPE) sample bags to collect streamwater with high levels of Hg (>45 ng L ). Specifically, we investigated the effect of holding times ranging from hours to days on streamwater collected during baseflow and storm flow. Unfiltered and filtered Hg and MeHg concentrations decreased with increases in time before sample processing; holding times of 24 hours or less resulted in concentration changes (mean 11 ± 7% different) similar to variability in duplicates collected manually during analogous field conditions (mean 7 ± 10% different). Comparisons of samples collected with manual and automated techniques (holding times < 24 h) throughout a year for a wide range of stream conditions were also found to be similar to differences observed between duplicate grab samples. These results demonstrate automated sampling into LDPE bags can be effectively used to collect streamwater for Hg and MeHg analysis, and encourage the testing of these materials and methods for implementation in other aqueous systems where high-frequency sampling is warranted.

Seasonal and flow‐driven dynamics of particulate and dissolved mercury and methylmercury in a stream impacted by an industrial mercury source

“…The automated sampler was retrofitted with a strainer and sample tubing made from Teflon and Isco ProPak TM disposable sample bags made of low-density polyethylene (LDPE). An evaluation of the LDPE bags to store East Fork Poplar Creek water for filtered and unfiltered Hg and MeHg analysis determined that differences between samples collected into PET bottles and filtered and preserved immediately and samples collected into the LDPE bags and filtered and preserved within 24 h (mean 11 AE 7% different) were similar to duplicate grab samples collected with PET bottles and preserved immediately (mean 7 AE 10% different) [45]. Concurrent grab and automated samples taken throughout the study during storm and baseflow periods verified the laboratory findings and are discussed in Riscassi et al [45].…”

Diel mercury concentration variations in a mercury-impacted stream

“…Two were conducted in summer (Su2013 ¼ 28-29 August 2013; Su2015 ¼ 17-18 September 2015) and one in We previously demonstrated that this autosampling method does not compromise sample integrity for our creek water. 20 Grab samples were collected by wading into the middle of the stream, triple rinsing the bottle with creek water, then lling and sealing the bottle for transport to the lab.…”

Increasing temperature and flow management alter mercury dynamics in East Fork Poplar Creek

“…A separate sample for TSS was collected in a 2 L HDPE bottle. Samples were either processed immediately in the field or held on ice until returned to the lab for processing (max holding time of 8 h; (Riscassi et al, 2014)). Concurrent with water sampling, ambient water conditions were measured (temperature, specific conductance, pH, dissolved oxygen; Table S1).…”