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Mercury Data in Ramford County

Sampling Protocols

Mercury Sampling in Air

The model used for mercury sampling in air in Ramford County utilizes a method called Trace Elements Analysis Model (TEAM). This model predicts the amount of elements including mercury in both wet or dry depositions. The results are based upon collected meteorological and emission data collected across the county including both wet and dry deposition contributions. The predicted range for total deposition rates are determined from the data collected using the TEAM and are reported in (µg/m²/yr)

Mercury Sampling in Water

To determine levels of mercury in drinking water, samples were collected from private wells across the county and packaged in mercury-free, sulfur-free glass containers. These samples were put on ice and shipped in sealed containers to state-certified labs for testing and analysis.

Mercury Sampling in Soil

To determine levels of mercury in the soil, cores were collected at various sites in Ramford County using either hand coring, gravity coring, or piston coring techniques. Co-located cores at each site provided sufficient sediment for chemical and physical testing. Cores were extruded and aliquoted - 2 cm slices from the top of the core and 4 cm slices from the remainder of the core; the aliquotes were placed into appropriate containers and submitted to contracted laboratories for analysis to determine the amount of mercury deposited in the soil at each site.

Mercury Sampling in Fish and other Fauna

Samples were collected by gill netting, otter trawls, electrofishing, hook and line, fish traps, and crab pots. Some samples were obtained from commercial and recreational fisherman. After collection, samples were sealed in plastic bags and stored in ice chests that had been cleaned, flushed with pesticide grade hexanes, and rinsed with distilled water.

Before processing , all samples were identified to species, weighed, and measured. Blue crabs were measured across the shell (point to point). Samples were stored frozen until processing. The samples excised from edible finfish consisted of a scaled fillet with skin intact for all species except American eels and bullheads, for which samples consisted of a skinless fillet. These standard fillets were either used as an individual sample from a single fish or combined with other individuals of the same species and size to form a composite sample usually consisting of five fish, although some composites consisted of fewer fish. Where possible, the portion taken from each fish consisted of 100 grams, yielding a five fish composite of 500 grams. For individual fillets greater than 100 grams the portion was taken by cutting from the anterior portion of the fillet and proceeding posterior until 100 grams was reached. For extremely large fish, three cross section of the fillet were taken; one from behind the pectoral fins, one from halfway between the first slice and the vent, and one from behind the vent to yield the 100 gram portion. The samples were thoroughly homogenized, packaged in mercury-free aluminum foil, labeled, and stored frozen in prolypropylene bags until requested for analysis.

Analytical Methods

The most advanced standard technique for mercury analysis in all media to date is the Cold-vapor Atomic Absorption Spectrometry Protocol. This system was used to determine mercury levels in small samples from each medium- air, water, soil, and organic. Using this method, mercury can be detected to levels as low is 0.1µg/L.

Special Note on Mercury in Water Analysis

The maximum level acceptable level of mercury in drinking water is 2µg/L. The Cold-vapor Atomic Absorption Spectrometry Protocol technique can accurately record levels up to 20 times smaller than that. More elaborate processes have been developed to detect mercury in pristine groundwater to determine background levels of mercury. Studies have shown that background mercury levels in pure groundwater lie between 0.001 and 0.040 µg/L.