Geoenvironment Impact Mitigation and Management - Sustainable Practices in Geoenvironmental Engineering - page 399

(nitrogen oxides), SO 2 (sulfur dioxide), CO (carbon monoxide), Pb and other metals such
as Al, As, Cu, Fe, La, Mg, Mn, Na, Sb, V, and Zn (Lin et al., 1997) as airborne particulates,
and VOCs (volatile organic chemicals) and PAHs (polycyclic aromatic hydrocarbons) such
as benzene, toluene, and xylene, and particulate matter PM 10 and PM 2.5 . Particulate mat-
ter PM 2.5 —i.e., particulate matter less than 2.5 μm in size—will in all likelihood remain
suspended in the ambient air; PM 10 (particulate matter less than 10 μm but greater than
2.5 μm) will be deposited eventually or with the aid or precipitation. Although acid rain is
one of the outcomes of precipitation through this type of atmosphere, deposition of the air-
borne contaminants has not received the attention that is deserved. Airborne particulate
matter is a great concern to public health in the ambient air because of their effect of these
particulates on the hearts and lungs of those who are exposed to these.
The impacts to the health and quality of biotic receptors and the land environment presented
by atmospheric- and land-based non-point sources of contamination cannot be readily miti-
gated by limited point-directed technological solutions. We recognize that the broad-based
nature of the affected regions—i.e., land surfaces and water bodies—make containment and
management of the spread of contaminants prohibitively dificult and costly. In consequence,
the use of the natural in-place soil as a tool for mitigation of the impact of such contaminant
sources is a solution that needs to be exploited. To do so, we need to develop a better apprecia-
tion of the assimilative properties of soils and also of the various geochemical and biological
aids that will increase or enhance the assimilative capability of the soils. This has been the
focus of this chapter. Contaminated land detracts considerably not only from one's ability to
provide the necessary food supply, but also compromises the receiving waters and sources of
water supply for humans. In summary form, the main issues addressed include
• Impacts from contaminants in the ground need to be mitigated and managed as a
beginning step toward protection of the resources in the environment and also as
a irst step toward achievement of a sustainable geoenvironment.
• Using the properties of the natural soil-water system as the primary agent for
such purposes allows one to address contamination sources that encompass the
range from point source to both land- and atmospheric-based non-point sources.
• Enhancing the natural attenuation properties of the subsoil to make it more
effective as a control tool allows the subsoil to remain in place as a mitigation-
management tool. This is the essence of a semipassive remediation-treatment of
contaminated sites.
• The physical, mechanical, chemical, and biological properties of soil made it a
good resource material for management of contaminants and waste products.
These properties are responsible for the assimilative capacity of soils and the natu-
ral attenuation capability of the soil.
• Mitigation and management of contaminants in the subsoil should seek to reduce
and eliminate the presence of contaminants in the soil. Engineering the natural atten-
uation capability of soils, through enhancements of the attenuation capability with
geochemical, biological and nutrient aids will provide greater management options.
• Reduction in the concentration and toxicity of contaminants is the ultimate goal.
Achievement of this goal can be obtained using various strategies involving tech-
nology and the properties of the soil. The various options discussed are by no
means the complete spectrum of capabilities. More innovative schemes are being
developed to address the problems of contamination of the land environment.