Sue Natali, postdoctoral associate in botany at the University of Florida, launched her research to find out whether an increase in CO_2 would in turn have any effect on pollution from mercury and other metals and found out that mercury will stick around longer in a CO_2-enriched world but it also will remain bound to the soil for a longer period.rnGlobal mercury emissions today range from 4400 to 7500 t/a, according to the Environmental Protection Agency. Natural sources such as volcanoes account for about half, with coal-fired power plants, smelters and incinerators contributing the remainder. When mercury is belched into the air, it returns to earth via rain, with bacteria and other natural processes converting it to methylmercury in lakes, rivers and oceans. Methylmercury builds up through the food chain, with the flesh of the biggest, most sought-after predator fish - tuna, swordfish, king mackerel, etc. - containing the highest concentrations.rnScientists have long recognized mercury levels in soil spike under trees, averaging four times the concentration in open areas. That's because trees effectively scavenge the poison from the atmosphere. Leaves and stems collect rainwater, and with it mercury; trees drop mercury-laden leaves on the ground, and trees take in the metal through their stomata, or breathing pores on leaves. It has also shown repeatedly that increased atmospheric CO_2 leads to increased plant and tree growth.
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