A Guide to Trace and Ultra-Trace Mercury Testing in Water

Transcription

1 A Guide to Trace and Ultra-Trace Mercury Testing in Water Blair Easton General Manager ALS Environmental Calgary 1

2 Presentation Overview Mercury Sources Mercury Cycle Anthropogenic Mercury Sources in Alberta Relative Mercury Concentrations Regulatory Limits Sampling Considerations Dissolved Mercury Sampling Field & Transport Blanks Mercury Analysis 2

3 Mercury Sources 3

4 Mercury Cycle 4

5 Anthropogenic Mercury Sources - Alberta Mercury is of particular concern in the northern rivers of Alberta. Where Coal Power Generation Plants are a source of Anthropogenic Mercury. 5

6 Anthropogenic Mercury Sources - Alberta Both bitumen and oil sands tailing ponds are known to contain traces of mercury. 6

7 Relative Levels of Mercury Concentration Typically Trace (low level) Mercury = results between 5-50 ng/l (ppt). Typically Ultra-Trace Mercury = results between ng/l One part per trillion (1 ppt) is a proportion equivalent to a drop of water diluted into 400 Olympic-size swimming pools. 1ppt = ppb = ppm 7

8 Mercury Regulatory Limits The lowest AB Tier I Ground Water Remediation Guideline = 5 ng/l (i.e. the Aquatic Life guideline). AB Regional Aquatics Monitoring Program (RAMP) has the lowest reported result for Total Mercury at 0.2 ng/l and the average result is ~3 ng/l. 8

9 Sampling Considerations The potential for contaminating ambient water samples with the mercury and interfering substances cannot be overemphasized. 9

10 Contamination Sources Sources of contamination can include: Metallic sampling equipment In-appropriate & Un-tested Sample containers Sampling gloves (e.g. powdered gloves) 10

11 Contamination Sources Atmospheric inputs such as dust and dirt from: Automobile exhaust Roads, bridges, wires and poles Cigarette smoke And, the Sampler e.g. older dental work 11

12 Historic Mercury Sampling Containers Until recently, the most common container type and preservative used for routine or low level mercury analysis of waters was: The High Density Polyethylene (HDPE) plastic container with nitric acid (U.S. EPA Method 245.1, 1972). 12

13 New Trace Level Mercury Sampling Requirements Pre-cleaned Borosilicate glass container with Teflon lined cap with 1:1 Hydrochloric acid (HCl). EPA Method (2005) 13

14 Ultra-Trace Level Mercury Sampling Requirements Pre-cleaned borosilicate glass or Teflon container with 1:1 Hydrochloric acid (HCl). EPA Method 1631 E (2002). The EPA further recommends the use of the "clean hands/dirty hands" technique during field sampling. Some labs recommend no preservation with (1:1) hydrochloric acid as it acts as a strong magnet for contamination. 14

15 Clean Hands Dirty Hands Procedure EPA 1631 E recommends to follow the US EPA clean hands / dirty hands (EPA 1669) sampling protocols when conducting ultra-trace mercury analyses. EPA Method 1669: Sampling Ambient Water for Determination of Trace Metals at EPA Water Quality Criteria Levels (Sampling Method). 15

16 Dissolved Mercury Sampling Filtration for dissolved Hg should be conducted within one hour of sample collection using a suitable in-line filter or 0.45 μm syringe filter. 16

17 Field & Transport Blanks Field Blank A sample prepared in the field using analyte free water and incorporate all aspects of sampling operations. Transportation Blank A sample in which the analytes of interest are absent is prepared by the laboratory and shipped with sample containers. It travels to the sampling site and returns with the collected samples. Transport Blank 17

18 Mercury Analysis Mercury Instruments Some instruments use enclosed samplers to prevent sample contamination. Mercury Analysis Labs Dedicated rooms for ultratrace mercury analysis prevent cross contamination from routine level samples. Open Air Sampler Enclosed Sampler 18

19 Questions 19