Mercury Contamination Mercury Contamination in Brazilin Brazil

Ozan KurtulusLouisa Meredith

Jeremy Trewin

IntroductionIntroduction• Hazardous environmental contaminant

•In Japan, 2252 people have been affected and 1043 have died due to Minamata Disease caused by mercury pollution

• Compound that can be found naturally in the environment

• Mercury poisoning also occurs from exposure to a soluble forms of mercury known as methylmercury

• Inorganic mercury is transformed into soluble methylmercury (MeHg+)

• dangerous concentration of methylmercury can be ascribed to human activity.

ImplicationsImplications• Methylmercury works its way up the food chain

• through bioaccumulation in the environment

•Larger, predatory species of fish are a greater danger for consumption due to their high concentrations of methylmercury

• Fish is the main diet in Amazonial communities

• About 90% of the mercury in fish is methylated

Brazil – Artisanal Gold MiningBrazil – Artisanal Gold Mining• The modern gold rush in Latin America started in the 1980’s

• 400 ton of gold produced per year

• 30 to 50 ton per year from Brazil – 80% from Amazon region

• An estimated 200,000 to 400,000 miners in the Amazon region

• Mercury contaminants often caused by artisanal miners using poor mining practices, usually due to a lack of economic alternatives

• Mercury is used in order to separate gold from the extracted ores

•Often illegally dumped into nearby water streams

Brazil - LoggingBrazil - Logging

• Mercury is released from cutting and burning of trees along river banks

•Relatively newly found contributor of mercury contamination

• through an investigation carried by Brazilian and Canadian researchers

100 to 200 tonnes of mercury released per year

Mercury Decontamination MethodsMercury Decontamination MethodsSolidification

• Physically binds or encloses contaminants within a stabilized mass

• Chemically reduces the hazard potential of a waste

•Amalgamation is typically used to immobilize elemental mercury

• dissolving the mercury in another metal to form a semisolid alloy known as an amalgam

• Does not reduce the total mercury content of the waste• it reduces the leachability of mercury• product that still may require disposal in a landfill.

Mercury Decontamination MethodsMercury Decontamination Methods• Water-based process

• Physical particle size separation

• Aqueous-based chemical separation•contaminants tend to bind to the finer soil particles rather than the larger particles

• Not cost-effective for small quantities

• Performed at the site of the contamination

Soil Washing

Thermal Treatment• Physical methods to remove mercury from the contaminated medium

•Heat is supplied under reduced pressure to the contaminated soil or waste, volatilizing mercury

•The off-gas is treated by condensation to generate liquid elemental mercury

•The treated medium may be used as fill material or disposed

Mercury Decontamination MethodsMercury Decontamination Methods

• Uses chemicals to transform dissolved contaminants into an insoluble solid

• Solid is then removed from the liquid phase by clarification or filtration

•Used to treat mercury-contaminated groundwater and wastewater

• Can reduce mercury concentrations to less than 2 μg/L

Precipitation

Adsorption

•Contaminants concentrate at the surface of a sorbent reducing their concentration

• Adsorbent packed into a column

• Contaminants are adsorbed as contaminated water is passed through the column.

Mercury Decontamination MethodsMercury Decontamination MethodsMembrane Filtration

• Separates contaminants from water by passing it through a semi-permeable barrier or membrane

• Membrane allows some of the constituents to pass through while blocking others

Mercury Decontamination MethodsMercury Decontamination Methods

• Widely used to isolate contaminated sediment

• In Situ Capping (ISC) is placed on site

• Ex Situ Capping (ESC), contaminated sediment is dredged and relocated to another site

• One or more isolating layers are placed over the sediment

• Composed of sand or finer materials•absorbs the mercury preventing it leaching into overlying water

• Advantages: Low cost, low adverse environmental effects

• Disadvantages: Not a treatable process, can be damaged

Capping

Mercury Decontamination MethodsMercury Decontamination Methods

• Useful for heavily polluted areas

• Used in the process of gold mining

• Can cause damage to the environment through sediment re-suspension

• Tested to prove a significant reduction in mercury

• Must be well planned and implemented to avoid damage

• Only a temporary solution•usually very costly and has issues with method of disposal

Dredging

Mercury Decontamination MethodsMercury Decontamination Methods

• Use of Mercury-resisting bacteria

• Enhances natural biological-chemical transformations that render pollutants harmless

• Reduces toxic mercury to volatile elemental mercury

• Existing passive adsorption and immobilization treatments•produce a large volume of mercury-loaded biomass, disposal of which is problematic

• Microorganisms such as mer operon does not produce such results.

• Potentially low costs

• Promising new technology

Bioremediation

SummarySummary• Current on-going problem

• No major remediation project planned

• Caused by local, illegal industry

• Large area therefore difficult to assess and control mercury pollution

• Large funds required

• Densely polluted areas : combination of dredging and capping

•For permanent remediation, investment in bioremediation is required