Scientific Process

1. Observation of phenomenon

2. Pose a question

3. Tentative explanation of phenomenon

(hypothesis is a testable explanation; >1 multiple hypotheses)

4. Design experiment (controls, dependent and independent variables)

Major Features

Observation: uses senses/tools

Hypothesis: testable explanation

Theory: supported with extensive data

Law: general statement explaining observation, holds true for all tests

Scientific Process

5. Collect data (qualitative and quantitative)

6. Analyze data (interpretation-does it make sense)

7. Report findings (is hypothesis correct?)

8. Peer reviewed/Challenge

9. Publish results (communication is essential)

Assumptions/Advantages

*Assumes natural phenomena can be explained through careful observation and experimentation

*Theories and Laws are NEVER proven correct*As our observations improve, theories and laws

may no longer be valid. The scientific method incorporates new information.

* Nonjudgmental-not good or bad

Amalgamation Mining in South America Basic Statistics

•Hg Released in Amazonia– 100-200 tons/year during past

20-70 yrs. (Pfeiffer et al, 1993; Malm, 1998)

– 2000-3000 tons total during current gold rush (Malm, 1998)

• Number of Gold Miners in South America– 543,000 - 1,039,000 (Veiga,

1997)

• In Brazil– 200,000 - 400,000 (Malm,

1998)– 650,000 in 1993 (Jernelov &

Ramel, 1994)– 1,600,000 – Peak mining

(Pfeiffer and Lacerda, 1988)

Evidence for Significant Environmental Impacts of Amalgamation Mining

• Physically watch Hg being released to the water and atmosphere; 65 % to 83 % atmospheric;– Hg in soils exhibited an Hg gradient, with the highest values

adjacent to gold refining shops

• In comparison to other environments, high Hg values in fish, water, sediments, and soils– High Hg values measured at sites 100-150 km downstream of

mining operations– Sediment cores in floodplains and floodplain lakes suggested

increases concentrations of Hg recent years

• Elevated levels of Hg in human hair and urine

0 100km

Porto Velho

Manaus

Rio SolimoesRio Amazonas

Humaita

Manicore

Borba

Rio

Aripuana

RioJamari

M1

M8

Amalgamation Mining

Rio

Madeira

M6

RioNegros

MF4

South America

Regional Geochemical Trends along the Madeira River, Brazil

(Investigators)

• Paul J. Lechler, Nevada Bureau of Mines and Geology

• Drude de Lacerda, University of Fluminense, Nitero, Brazil

• Jerry R. Miller, Western Carolina University

• W. Berry Lyons, The Ohio State University

• John J. Warwick, University of Florida

• Jean-Claude Bonzongo, University of Florida

0 100km

Porto Velho

Manaus

Rio SolimoesRio Amazonas

Humaita

Manicore

Borba

Rio

Aripuana

RioJamari

M1

M8

Amalgamation Mining

Rio

Madeira

M6

RioNegros

MF4

South America

0 100km

Porto Velho

Manaus

Rio SolimoesRio Amazonas

Humaita

Manicore

Borba

Rio

Aripuana

RioJamari

M1

M8

Amalgamation Mining

Rio

Madeira

M6

RioNegros

MF4

South America

Primary Sources of Hg in Tropical Regions of South America

• Hg Amalgamation Mining– Modern (~100-120 tons/yr in Brazil in 1980s & 90s)

– Historic Stocks (196,000 tons from 1545 to 1900 in South and Central America)

• Release of Hg during biomass burning.• Naturally high concentrations of Hg in soils and

alluvial deposits – Hg sequestered in Lateritic soils is released during

erosion of deforested terrain.

After Roulet et al. 1995, 1998, 1999; Malm, 1998; Nriagu, 1994

Venezula

AtlanticOcean

Suriname

EssequiboRiver

Puruni River

MazaruniRiver

0100 100

Miles

Sample Site

Issano

Omai

GeorgeTownBartica

PataroRiver

KanawarukRiver

Guyana

Guyana

Hg Concentrations in Fish of the Potaro River

• 57 % of carnivorous fish exceeded the WHO consumption level of 0.5 ppm.– Mean concentration for some species exceeded 1 ppm.

– Highest Hg concentration was 3.771 ppm.

• 0 % of non-carnivorous fish exceeded the WHO consumption level of 0.5 ppm.

Data from: An Orientation Survey conducted by GGMC in cooperation withGEPA, UG, Fisheries and Oceans Canada & CANMET

Venezula

AtlanticOcean

Suriname

EssequiboRiver

Puruni River

MazaruniRiver

0100 100

Miles

Sample Site

Issano

Omai

GeorgeTownBartica

PataroRiver

KanawarukRiver

Guyana

Guyana

Venezula

AtlanticOcean

Suriname

EssequiboRiver

Puruni River

MazaruniRiver

0100 100

Miles

Sample Site

Issano

Omai

GeorgeTownBartica

PataroRiver

KanawarukRiver

Guyana

Guyana

Downstream Trends in Hg concentration(Mazaruni River - Channel Samples)

0.000

0.200

0.400

0.600

0.800

0 100 200 300 400

Distance Upstream from Bartica (km)

Hg

(u

g/g

)

CuyuniTakutu

KurupuraIssano

Puruni R.

Flow Direction

Downstream Trends in Hg Concentration(Essequibo River)

0.000

0.050

0.100

0.150

0.200

0.250

0 20 40 60 80 100 120 140 160

Distance Upstream from Bartica (km)

Hg

(u

g/g

)

Channel Floodplain

Omai

Potaro Kanawaruk

Flow Direction

Depositional Unit Comparsion Mazaruni River

0.077 0.0860.0560.049

0.121

0

0.04

0.08

0.12

0.16

Hg

(p

pm

)

Histogram of Sample ConcentrationsChannel & Sand Bar Samples

4

0

41 1

9

15

0

5

10

15

20

0-40 40-80 80-120 120-160 160-200 200-250 >250

Hg Range (ppb)

Nu

mb

er o

f S

amp

les

Evidence for Measurable Anthropogenic Hg

• Hg Levels exceeding “Background” data in channel bed, recent floodplain, and mud flat deposits;

• Decreases in Hg concentration with depth (time) in 3 of the 4 cores collected;

• Increases in Hg downstream of tributaries with significant mining activity.

Anthropogenic Sources of Hg in the River Systems

Mining Inputs

River Water, Sediments,Biota

Indirect• Hydraulic Mining

• Deforestation

•Release of Elemental• Hg to River Waters

• Amalgam “Burning”

Direct

Other Sources

Atmospheric

•Biomass Burning

Deforestation & Soil Erosion

•Logging

•Agriculture

•Road Construction