Ecoscript 49

William M. Stigliani. Changes in Valued "Capacities" of Soils and Sediments

This paper discusses the buffering, oxygen-donating, and sorp-
tion capacities of soils and sediments as an inter-connected
system for regulating the retention and release of chemical
pollutants. In this context, the author discusses the chemical
conditions under which sediments may serve as a source or a
sink for toxic materials, and conditions under which soils may
retain or release them. It is demonstrated that nonlinear,
timedelayed ecological transformations in soils and sediments
often can be understood in terms of the interlinked system.
The author discusses some possible future long-term environ-
mental problems that might beset Europe, and some implications
for a monitoring strategy for foreseeing such problems.

Because the release of adsorbed toxic chemicals from heavily
polluted sediments and soils can occur suddenly owing to chan-
ges in oxygen status (i.e. redox potential) or acidity, strat-
egies for preventing the long-term release of such materials
should not only consider current conditions of pH and redox
potential, but also, how those conditions might change in the


Abstract 7

1. Introduction 7

2. The Soil's Capacity for buffering against acidic
inputs 9
2.1. Historical perspective 9
2.2. Potential vulnerabilities in the future 12

3. The soil's capacity to adsorb phosphorus and toxic
materials 14
3.1. Phosphorus 14
3.2. Toxic materials in agricultural soils 19
3.3. Potential vulnerabilities in the future 21

4. Oxygen donating capacities of soils and sediments 23
4.1. Anoxia in coastal waters 24
4.2. The impact of dredging sediments in coastal areas 26
4.2.1. Magnitude of the problem 26
4.2.2. Changes in redox potential as a major source of
release of toxic materials from dredging spoils 28
4.3. Potential vulnerabilities in the future 31
4.3.1. Estuaries and coastal marine areas 31
4.3.2. Inland freshwater systems 33
4.4. Wetlands as sinks for sulfates, nitrates and toxic
metals 34
4.4.1. Sulfates 34
4.4.2. Nitrates 34
4.4.3. Toxic metals 35

5. Overview: development/environment interactions and
the potential for surprises 36
5.1. Introduction 36
5.2. Primary interactions: Table VI 37
5.3. Secondary interactions: Table VII 39
5.4. Combined primary and secondary interactions:
Table VIII 41
5.5. The potential impact of climatic change 42

6. Implications for environmental changes in the
future, including surprises 44
6.1. The continued acidification of soils, even in an
era of reduced acidic emissions 44
6.2. The saturation of soil by phosphate, and subsequent
leaching of phosphate into ground and surface
waters, leading to a new wave of eutrophication of
european waters 44
6.3. A continuation of anoxic condition in coastal
waters, resulting in episodic fish-kills and
emissions of hydrogen sulfide 45
6.4. The "bleeding" of toxic metal from contaminated
estuarine sediments in an era of vastly improved
water quality 45
6.5. The release of toxic metals from agricultural soils
upon the cessation of liming 46
6.6. Environmental changes occurring as a result of
changes in soils' redox conditions due to drying
up of wetlands, or the moisturization of dry lands 46

7. Implications for a monitoring strategy 48
7.1. Indicators: inputs and capacities of reservoirs 48
7.2. Lessons from the most vulnerable areas 50
7.3. The bottom-up approach 51

8. Conclusion 53

Acknowledgement 53

References 54