Soils contain dynamic biological systems that play a vital role in the functioning of ecosystems. Soils and sediments are one of the three environmental media (soil, water and air) and are non-renewable resources that occupy a central role in the economic structure of all civilization throughout history. The essential ecosystem services that soils provide include the regulation of biogeochemical cycles, water purification, retention and delivery of nutrients to plants, regulation of the hydrological cycle including mitigation of floods and droughts, and determination of the fate and behavior of pollutants in the environment [7]. Many of these processes, including the formation of soil structure itself, are functions of biological processes that are mediated by diverse populations of eubacteria, archaea, fungi, yeast, microalgae, protozoa, nematodes, and other microscopic invertebrate animals. The numbers of organisms and their collective contribution to the mass of the soil is highly variable within and between soils (Table 1.1) [12].
Table 1.1 Relative numbers and approximate biomass of the soil microbiota in a fertile mollisol [13].
Numbers Biomass
Organisms per m2 per g wet kg/ha
Bacteria 1013-1014 108-109 300-3000
Actinomycetes 1012-1013 107-108 300-3000
Fungi 1010-1011 105-106 500-5000
Microalgae 1010-1011 103-106 10-1500
Protozoa 109-1010 103-105 5-200
Nematodes 109-1010 101-102 1-100
Earthworms 3-300 10-1000
Other
invertebrate fauna 109-1010 1-200
invertebrate fauna 109-1010 1-200
The extensive use of synthetic organic chemical and petroleum products in the past decades has lead to their environmental ubiquity. The presence of certain chemicals in the environment has led to a variety of human health problems including cancers, disruption of the endocrine and immune systems, and reproductive diseases [14, 15]. Moreover, the degradation of natural systems through the accumulation of pollutants extends beyond the locality of synthetic compounds utilization. Therefore, no environment, however remote, is free from the burden of environmental contamination. Soil is perhaps one of the most significant pools of persistent organic pollutants (POPs), as physical and chemical properties of soil can contribute to the persistence of certain chemicals in soil matrices. However, unlike other environmental phases, a unique opportunity to degrade POPs exists while they are bound to soil. This is largely due to the presence of microbial communities with the enzymatic capability to degrade pollutants [16-18]. This dissertation explores a potential method of managing for ecosystem resilience: applied microbial ecological systems for biological treatment of organic pollutants in soils.
12. Stockdale, E.A. and P.C. Brookes, Detection and quantification of the soil microbial biomass - impacts on the management of agricultural soils. Journal Of Agricultural Science, 2006. 144: p. 285-302.
13. Metting, F.B., Soil Microbial Ecology: applications in agricultural and environmental management, ed. M.F.B. Jr. 1993, New York: Marcel Dekker Inc.
14. Jorgenson, J.L., Aldrin and Dieldrin: A review of research on their production, environmental deposition and fate, bioaccumulation, toxicology and epidemiology in the United States. Environmental Health Perspectives, 2001. 109: p. 113-139.
15. Vasseur, P. and C. Cossu-Leguille, Linking molecular interactions to consequent effects of persistent organic pollutants (POPs) upon populations. Chemosphere, 2006. 62(7): p. 1033-1042.
16. Singer, A.C., et al., Impact of the plant rhizosphere and augmentation on remediation of polychlorinated biphenyl contaminated soil. Environmental Toxicology and Chemistry, 2003. 22(9): p. 1998-2004.
17. Heitkamp, M.a., W. Franklin, and C.E. Cerniglia, Microbial-metabolism of polycyclic aromatic-hydrocarbons - isolation and characterization of a pyrene-degrading bacterium. Applied and Environmental Microbiology, 1988. 54(10): p. 2549-2555.
