Argillic Horizon

Plate 4.2 Field photographs contrasting three soil profiles. (a) An alfisol (luvisol) with an argillic horizon. Clay material has been washed downward from the E to the B master horizon. Subordinate categories are indicated by lower case letters: the 'b' indicates an eluvation of clay from the E horizon, hence 'Eb'; the 't' indicates a clay-rich or argillic horizon in master horizon B, hence Bt. (b) A spodosol (podzol), where subordinate 'h' indicates illuval accumulation of organic matter, subordinate 'a' indicates highly decomposed organic matter, and subordinate 's' indicates illuvial accumulation of Fe and Al oxides. (c) A mollisol where subordinate 'g' indicates evidence of gleying (see Fig. 4.25). Notice the presence of groundwater in the bottom of the soil pit. Soil master horizons are typically centimetres to tens of centimetres thick (see also Fig. 4.21).

Plate 5.1 Excavations for copper at Parys Mountain, Anglesey, UK. The spoil heaps provide a huge surface area for sulphide oxidation. The lake waters in the pit bottom have pH below 3. Photograph courtesy of J. Andrews.

Plate 5.2 Crusts of iron oxide (goethite) coating stream bed. Drainage from Parys Mountain, copper mine Anglesey, UK. Photograph courtesy of J. Andrews.

Plate 6.1 Black smoker, East Pacific Rise. From Des Oceans aux Continents. BSGF 1984, (7), XXVI, no 3. Société Géologique de France, Paris. Reproduced with thanks.

Plate 6.2 Global composite image of optical depth (tau units) in the Earth's atmosphere for June-August 1989-1991. Optical depth data provides a measure of aerosol concentration. Reproduced from Husar RB, Prospero JM and Stowe LL (1997) Journal of Geophysical Research 102, 16889-16909, copyright by the American Geophysical Union.

Earth Gravity Map

Plate 6.3 A global view of the Earth's biosphere from multiple satellite images compiled by NASA. Individual images focus on small areas of the Earth concentrating on the light spectrum dominated by green chlorophyll. This image, based on chlorophyll content, provides an estimate of plant standing stock rather than productivity (as in Box 6.6), although the two parameters are closely related. This colour image also demonstrates that there are many small-scale ocean features, such as eddies, which would complicate the simplified map in Box 6.6. The image also highlights the importance of tropical forests as areas of high plant biomass. Estimates of phytoplankton pigment concentrations (mgm-3) shown according to colour code.

Fig. 4.36 Mechanisms of phytoremediation: (A) phytoaccumulation; (B) phytodegradation: (C) rhizo-enhanced degradation; (D) phytovolatilization.

disperses and dilutes it. Phytovolatilization has also been applied to land contaminated with mercury (see Section 5.6.1).

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