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A low pH of the rainwater and subsequent increased acidity in the environment can trigger off or aggravate the effects of certain harmful pollutants.
(i) Mercury:
♤ Methyl mercury and related short chain alkyl mercurial compounds are most dangerous to humans, as they accumulate in edible fish tissue.
♤ Although acid deposition may not increase the production of methyl mercury, it may increase the partitioning of methyl mercury into the water column.
♤ The use of lime has helped in reducing the mercury levels in fish.
(ii) Aluminium:
♤ Acidified waters are known to leach substantial amounts of aluminium from watersheds.
♤ Even at relatively low levels, aluminium has been implicated in dialysis dementia, a disorder of the central nervous system, which may be toxic to individuals with impaired kidney function.
(iii) Cadmium:
♤ Cadmium can enter the drinking water supply through corrosion of galvanized pipe or from the copper- zinc through corrosion of galvanized piper or from the copper-zinc solder used in the distribution systems.
♤ A decrease in water pH from 6.5 to 4.5 can result in a fivefold increase in cadmium and could cause renal tubular damage.
(iv) Lead:
♤ Foetuses and infants are highly susceptible to drinking water lead contamination.
♤ High blood lead levels in children (>30 mug/Ml) are believed to induce biochemical and neurophysiological dysfunction.
♤ However, lower than normal blood levels of lead can cause mental deficiencies and behavioural problems.
(v) Asbestos:
Asbestos in natural rock can be released by acidic waters.
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Tree ferns like Cyathaea and Alsophila have erect rhizomes with generally unbranched trunks, topped by a crown of graceful, feathery fronds that form a rosette at the apex.