Studies of mercury pollution in a lake due to a thermometerfactory situated in a tourist resort: Kodaikkanal, India RAVI KUMAR 2009JE0618
• Introduction• Sources of mercury• Forms of mercury and method to detect• Fick’s Law and its role• Aquatic Mercury Cycle• Geochemical characteristics• Kodaikkanal mercury pollution• Conclusion
INTRODUCTION• Non-essential element with no biochemical or nutritional function to bio organisms.• Mercury is persistent.• All forms of mercury are extremely toxic.• Methylated mercury – bioaccumulation and biomagnification.
SOURCES OF MERCURY•Natural Sources- volcanoes, geologicdeposits of mercury, and volatilization fromthe ocean.•Anthropogenic Sources- Alkali and metalprocessing, incineration of coal, medical andother waste, and mining of gold andmercury.
FORMS OF MERCURY AND METHOD TO DETECT• FORMS – Hg, Hg(II), MeHg.• METHOD- Mercury was analysed by cold vapour atomic absorption spectrometry (CV-AAS) using a mercury analyser.
FICK’S LAW• The diffusion first Fick law allows the estimation of the diffusive fluxes (J) across water–sediment interface, by constructing a linear gradient of the solute concentration (C) in pore water at the 0–0.5cm layer (Z):Where DAB=Diffusion Constant.
Table– Quantities of reactive and non-reactive mercury (nmolm2 (12 h)1 and mmolm2 (12 h)1,respectively) present in the Largo do Laranjo water column and estimation of the pore waterscontribution to the enrichment of the water column (%) Zone A Zone B Zone C Zone DMercury present in water columnReactive Hg (nmolm2 (12 h1)) 394 396 318 150Non-reactive Hg (mmolm2 (12 h1)) 2.99 3.35 2.18 2.34Contribution of pore waters to enrichment of water columnReactive Hg (%) 0.016–0.17 0.006–0.12 0–0.012 0.027–0.030Non-reactive Hg (%) 0.064–0.50 0.010–0.054 0.007–0.033 0.005–0.056
KODAIKKANAL MERCURY POLLUTION• Mercury contamination originating from a thermometer making factory.• Present study determined total mercury and methyl mercury in water, sediment and fish samples and compared the values with those from two other lakes, Berijam and Kukkal.
• Ambient levels of mercury in air of 1.32 mg/m3 were found immediately outside the factory premises.• Outside the premises of the factory, the mercury levels in the lichen and moss were 7.9 mg/kg and 8.3 mg/kg respectively.• Mercury vapour once released into the air is known to travel long distances leading to widespread contamination.
• Kodai sediment showed 276-350 mg/kg HgT with about 6% methyl mercury. Berijam and Kukkal sediments showed HgT of 189-226 mg/kg and 85-91 mg/kg and lower methylation at 3-4% and 2%, respectively.• HgT in fish from Kodai lake ranged from 120 to 290 mg/kg.
• Analysis of water, sediment and fish samples from Kodai Lake from the tourist resort of Kodaikkanal, India, showed elevated levels of mercury even 4 years after the stoppage of mercury emissions from the thermometer factory that operated for 18 years and was closed down subsequently in 2001.• This shows that mercury is retained