RECLAMATION AND RESTORATION - The Soil - page 210

Northern marsh-orchid Dactylorhiza purpurella
Viper's bugloss Echium vulgare
Marsh helleborine Epipactis palustris
Fragrant orchid Gymnadenia conopsea
Bee orchid Ophrys apifera
Green-winged orchid Orchis morio
Common broomrape Orobanche minor
Round-leaved wintergreen Pyrola rotundifolia
Two types of industrial wastes, blast furnace slag and Leblanc wastes, have pro-
duced extreme alkaline conditions. Slag from blast furnaces was produced in large
quantities by heating iron ores with lime; for every 10 tons of iron produced there
were 5-8 tons of alkaline slag which had to be disposed of. Likewise, in the manu-
facture of sodium carbonate in the nineteenth century by the now obsolete Leblanc
process, a slurry of calcium oxide and hydroxide wastes was produced which was run
into beds several acres in extent. These beds formed a feature of the landscape in parts
of south Lancashire and Cheshire.
Both of these materials in the fresh state have pH levels as high as 12.5, and
can scarcely be considered as soils at all. In contrast with the pyritic colliery spoils,
however, leaching of these wastes effects a significant change within a relatively short
period of time - in this case by reducing their alkalinity. Lichens and mosses are
among the first colonists as the superficial layers of these wastes become leached, and
thereafter a range of other species with deeper rooting habits gradually become estab-
lished. After about 40 years, the pH in the top 25 cm of the profile is reduced to 8.0 or
less, and after 80 years this degree of leaching extends down to about 55 cm as shown
in Table 12 . Disturbing a site, therefore, can put the clock back dramatically. Beds
that are now 100 years old support some very interesting communities of lime-lov-
ing plants including, in some places, vast colonies of 3-4 species of orchids ( Table 14
and Plate 13 ) . The oldest, undisturbed sites are becoming colonized by willows and
hawthorn which indicate that a substantial nitrogen capital has accumulated, but little
is known about the soil fauna and microflora of these artificial soils.
These few examples illustrate several points in the natural development of soil
ecosystems on a range of materials disembowelled from the earth or spewed out of
the furnaces and vats of industry. The obstacles which have to be overcome for the de-
velopment of a living soil can be divided into physical and chemical factors. Hostile