Air pollution is now much lower

Air pollution is now much lower than a couple of decades or so ago. The policy of using cleaner fuels (low Sulphur) has had a real benefit and the acid rain episodes are no less frequent and less severe. However one still feels that recovery would be faster if waters were limed. This is probably a correct assumption but effective liming is unfortunately very difficult and expensive and any benefits dubious. The normal water flow in a river is unlikely to be acid and liming will have no effect as lime only dissolves in acid water. The problem water is associated with rain run off washing acidity that has been deposited on vegetation or in snow melt. To combat this acidity it requires a rapid injection of very fine lime and dosing in proportion to the flow rate. Some river have point sources of acid leaching from disused mines and their spoil heaps and in theory treating these would be cost effective Problems arise if there is ochre (rust) present as this will coat any limestone applied. If the river sources from limestone it will have collected enough lime at source to neutralise and acidity . Liming small lakes and ponds with powdered limestone is more cost effective and the benefits are more apparent. However the lime will only dissolve if the water is at least slightly acid and that means doing it in the early winter and possibly repeating it in early spring. Liming lakes helps fish survive over the winter and brings them back into condition earlier in spring. As mentioned earlier there is now less acid rain and it would be worthwhile to monitor the water pH as it may be cheaper to top up the stocking. Ceri Evans (Vice Chairman Conservation Committee.)