Mercury in Soils and Sediments: Still River Basin and Long Island Sound Rachel Bronsther and Patrick Welsh

Mercury (Hg) Hg comes in elemental and various organic compounds and complexes (e.g. HgS, HgCl2, MeHg) Exposure to organic Hg, in particular methylmercury, has potential adverse effects in humans. Exposure can be from ingestion or inhalation. The nervous system is harmed by the organic compound. Elemental Hg can become methylated by the environment.

Low Dose Effects In children: Neurotoxicity (e.g. problems with fine motor skills, visual-spatial abilities, verbal memory) In adults (long term, lose dose exposure): weakness, tiredness, headaches, lack of appetite, digestion problems, weight loss, trembling of hands, numbness of extremities, tingling of lips and tongue, etc.

Fish Consumption EPA has determined that the primary form of human exposure to methylmercury is through fish consumption. Population at the greatest risk – children who eat or whose mothers consume a large amount of fish EPA has determined that a RfD of 0.1 ug MeHg/day is acceptable.

Mercury in Soils No decisive data seems to exist on what levels in soil are “safe”. In CT, up to 20 ppm of Hg in residential areas is acceptable. (Compared to MA, where legal residential levels are set at 10 ppm.) No way to determine what percentage of Hg found in soil is in its organic form without testing, as relative abundances vary.

Mercury Levels Normal modern soil background levels for mercury in the northeast are around 200 to 300 parts per billion –Mostly due to atmospheric deposition Sediment samples from the Housatonic River were higher than ‘normal’. Sources were traced to the Still River –A north flowing tributary.

Still River Flows through Danbury and Brookfield and into the Housatonic River in New Milford. It is 22 miles long and has a drainage area of 85 square miles. Its mean flow of 377 ft 3 /sec.

Extreme levels Along the Still River levels of mercury in sediment were found to be 5-10 ppm with extremes up to100 ppm –500 times higher than background Where is the source?

Danbury, CT Former hat-making capital of the world -- 20,000 hats/year were produced in 1800; 1 million hats/year by Mercury was used in the felting process. Located in the Still River Basin.

Mercury in Hat Making Mercury nitrate was used in the felting process Workers in the Danbury factories often suffered mercury poisoning –Called “mad hatters” –The origin of the phrase mad as a hatter The symptoms of the disease were called the ‘Danbury shakes’ –symptoms of chronic mercury exposure on the nervous system include increased excitability, mental instability, tendency to weep, fine tremors of the hands and feet, and personality changes

Long Island Sound

LIS Cores Cores from the LIS were tested for mercury in order to see the migration of mercury from the Danbury source area –North through Still River into Housatonic and then emptied into LIS Results showed increased levels of mercury –Levels were relatively low ( ppb) compared to that of the Still River

Sample Collection Surface Samples Cores –Cores are generally sliced every 2cm up to 40 cm in depth –After 40 cm, the core is sliced every 5 cm –The outsides of the core slices are cut off to prevent cross contamination resulting from smearing the outside Cubes are formed in this way Dried on Styrofoam plates Crushed and homogenized in plastic bottles

DMA (Direct Mercury Analyzer) 80 1.Sediments are placed in open crucibles where they are weighed (Crucibles are non-reactive heat-resistant nickel containers) 2.Pneumatic arm places the crucibles in the quartz combustion furnace Sediments are dried at 300° C for 10 seconds 3.Thermally decomposed at 850° C for 180 seconds, which volatizes Hg, water, carbon dioxide, and organic matter 4.Flowing oxygen carries this gas to a furnace where it is oxidized and halogens, sulfides, and nitrogen oxides are trapped. 5.The remains go to an amalgamator in a third furnace. 1.The amalgamator is made of gold particles that forms a metal alloy with Hg. 2.Non-amalgamated products are carried out taking another 60 seconds 3.Amalgamator is heated intensely for 12 seconds and releases Hg vapor to absorbance cells

DMA cont. 1.Two cells (or cuvettes) are aligned with a small collection flask between them where a mercury lamp positioned at the end of the cells emits a single wavelength that is absorbed by Hg 0 2.Atomic absorption is measured by the spectrophotometer, which is directly related to the concentration 3.Surface area of the absorbance peak is transmitted to the computer, which calculates the ppb Hg is a function of the enter in weight

A new calibration was required at the beginning of the summer, as the machine had experienced some drift. We calibrated, and recalibrated and recalibrated….finally, we got Calibration “Gold”. First we tried liquid standards, which did not work. We ultimately calibrated using NIST and NRCC dry standards. Calibration

Standards We’ve been using 5 standards, 3 of which are distributed by NIST and 2 from the NRC. The standards include homogenized soil ranging in Hg levels from 90 ppb to 3040 ppb.

Still River Basin GPS locations:

SRs

SR, con’t. Last Friday we took additional Still River samples (SR3), and by the end of the summer we plan to have both SR2 and SR3 values on the GPS map of the Basin.

WLIS75 C1 core

Estimating Age of Sample Age = 2001 – (depth (cm)/.44) Because rough accumulation rate is 1cm = 2.2 years And, the inverse of 2.2 is 1/.44

Around , some sort of dumping took place that caused an unnatural increase of Hg (up to 3 ppm) in this area of LIS. This was also a period of major floods…. Flood deposit??? ?

Conclusion: The old hat factories of Danbury, CT serve as a source of Hg. The source can be traced down through the Still River (very high concentrations; around 5-10 ppm) through the Housatonic (still high) into the Western LIS ( ppb).