Slide 1

LAB 8 MERCURY IN FOREST SOILS RELATIONSHIP BETWEEN HG AND ORGANIC MATTER

Slide 2

LAB 8 MERCURY IN FOREST SOILS Methylmercury [CH 3 Hg] = most toxic (immune systems, nerves) monomethylmercury [CH 3 Hg] dimethylmercury [(CH 3 ) 2 Hg] Elemental mercury [Hg] = less toxic - Mercury can be in solid form (silver), but can also be in liquid and gaseous form. - Mercury found naturally in small quantities in nature. - Natural conversions = Some bacteria process sulfate (S04) and convert Hg to CH 3 Hg - Used to mine gold - Burning coal releases mercury into the atmosphere

Slide 3

HG IN NATURE Hg cycle from atmosphere to the foliage, sediment, then bacteria that converts it and it goes into the animal cycle. bioaccumulation

Slide 4

HG AND PROTEINS

Slide 5

HG AND SULPHUR

Slide 6

DMA-80 MERCURY ANALYZER

Slide 7

DMA-80 MERCURY ANALYZER SCHEMATIC Thermal Decomposition Amalgamation Catalytic Conversion Atomic Absorption Spectrophotometry

Slide 8

THERMAL DECOMPOSITION -Sample dried in an oxygen stream in a quartz tube -The temperature at which a substance will chemically decompose -The heat breaks down chemical bonds -Typically 850 C

Slide 9

CATALYTIC CONVERSION -Combustion products are then carried down through the catalyst furnace to further decompose. -Typically 600 C Captures poisons (i.e. sulphur/halogens) Provides oxygen to assist combustion Traps partially oxidized residuals

Slide 10

AMALGAMTION -Mercury comes from the catalyst in vapour form is trapped in a gold amalgamator -Hg binds to the gold plate and is then desorbed or released towards the AAS after other combustion by-products are flushed away -Amalgamation furnace is heat and Hg is released. Typically 900 C

Slide 11

ATOMIC ABSORPTION SPECTROPHOTOMETRY -Atomic absorption used to determine the mercury content. -Low pressure mercury lamp (254 nm) -Uses optical radiation (light) to quantify Absorbance Profile

Slide 12

TIMELINE

Slide 13

LOI AND CARBON LOI (loss of ignition) is an indirect measure of organic matter. Samples are burned in a muffle furnace for 6 hours at 600 C, then weighed after burning to see the difference in weight. This shows how much OM (and other elements) have been burned off. Mineral soil remains behind. - Depending on ignition temperature LOI can cause loss of salts, structural water, and inorganic carbons which effect results. Close relationship between LOI and C% (MFs data from central and northwestern NB)

Slide 14

LOI AND CARBON

Slide 15

ORGANIC MATTER AND HG - DOM (dissolved organic matter) has a strong affinity to Hg. - Methylmercury is often found in aquatic environments and binds to metals strongly, affecting solubility, mobility, and toxicity. LAB: - Use LOI (loss of ignition) and C % to see any relationships with the sites across Fredericton. - Colour? Would areas of high colour and therefor high OM show relationship? 2014 Lab Results

Slide 16

MERCURY IN FREDERICTON? LAB: -Compare the Hg measurements across all Fredericton sites -Analyze (Think & Research) the data for any relationships with LOI/C% and past quality data. -Show basic information in appendices (if necessary) and show graphs/tables of relationship results. -Discuss the trends found over the years and back it up with any literature (academic references only). -Enjoy your last lab!

Slide 17

REFERENCES Milestone, 2014. Principles of Operation. Retrieved from: http://www.milestonesci.com/direct-mercury-analyzer/dma80-principles.html