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 ConsumptionEPA has determined that the primary form of human exposure to methylmercury is through fish consumption.

Population at the greatest risk – children who eat orwhose 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 levelsin soil are “safe”.

In CT, up to 20 ppm of Hg in residential areasis acceptable.

(Compared to MA, where legal residential levels are set at 10 ppm.)

No way to determine what percentage of Hg found insoil is in its organic form without testing, as relativeabundances 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 RiverFlows 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 ft3/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 1836. 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 (400-800 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 seconds3. 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 Hg0

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

StandardsWe’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

SR2 sample avg ppb 13 3953.8714 1967.64515 4493.4216 3267.56517 857.19518 3709.919 130517.920 4623.7121 7433.6922 3800.6723 1936.0724 2463.45525 5516.6126 4774.427 4796.0428 5295.37529 1970.41530 2158.7731 6990.00532 12482.7433 5449.6334 6015.1135 3615.64536 54.3537 8972.15538 4518.47

SR1 sample av ppbSR1-176 1637.935SR1-178 2405.095SR1-180 2991.135SR1-181 1817.59SR1-182 2198.647SR1-183 2017.157SR1-185 1777.69SR1-185 5888.093SR1-186 1524.23SR1-187 2136.52SR1-188 1586.398SR1-190 4173.405SR1-190 7040.653SR1-191 2929.038SR1-193 7483.218SR1-194 8104.16SR1-195 1662.988SR1-196 1652.15SR1-197 1079.44SR1-198 4995.47SR1-199 2971.268SR1-200 1568.358SR1-201 1706.583SR1-203 1812.993SR1-204 5952.048SR1-205 2795.603SR1-206 6308.21SR1-207 6789.597SR1-209 1613.27SR1-211 77122.32

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

ppb vs. depth of WLIS 75C1 core

0

500

1000

1500

2000

2500

3000

3500

0 20 40 60 80 100 120 140 160 180 200

depth (cm)

ppb

Hg

% H20 vs depth of WLIS75C1 core

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 20 40 60 80 100 120 140 160 180 200

depth (cm)

% w

ater

calculated dry density vs. depth of WLIS75 C1 core

00.20.4

0.60.8

11.2

1.41.6

0 20 40 60 80 100 120 140 160 180 200

depth (cm)

dry

dens

ity (g

/cm

^3)

Hg deposition vs. Depth of WLISC175

0

100

200

300

400

500

600

700

0 20 40 60 80 100 120 140 160 180 200depth (cm)

Hg

de

po

sit

ion

PW (Rachel and Pat) and PW (Bess) vs. depth of WLIS75C1 core

0

10

20

30

40

50

60

70

80

0 20 40 60 80 100 120 140 160 180 200

depth (cm)

Per

cen

t W

ater

(%

)

% water(Rachel)Bess % water

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 1950-1970, 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???

depth (cm) Age of sample (yr)1 1999

2.5 19953.5 19934.5 19915.5 19896.5 19867.5 19848.9 19819.5 1979

14.5 196819.5 195724.5 194529.5 1934

?

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 (400-800 ppb).