Soil condition microorganisms

The production and release of organic molecules by the root systems of plants have been extensively studied under a wide range of soil conditions (nutrient and water availability, pre.sence of pollutants, etc.,. see Chaps. 2 and 3). Furthermore it has been clearly demonstrated that soil microorganisms are able to produce molecules that can affect the physiology and architecture of roots (3) evidence has been also provided that molecular signals between plants and microorganisms are exchanged (see Chap. 7). 

Lee, J.K. Degradation of the herbicide, alachlor, by soil microorganisms. III. Degradation under an upland soil condition, J. 

The remediation site must be capable of supporting drilling operations where vapor extraction wells are required. Microorganisms used for bioremediation are not effective in toxic soil conditions. Also, because the rate of bioremediation is much slower than vapor extraction, the system must operate for a period of time after volatile contaminants have been removed by vapor... 

Potatoes harvested luider wet soil conditions should be dried immediately. Drying involves removal of water present on the outside of the potato or in the soil on the potatoes in order to eliminate conducive conditions for the multiplication of microorganisms and to prevent the spread of rot and other storage diseases (Sijbring, 1987). The ventilation fan should run continuously during this phase while the average potato pile temperature is allowed to settle... 

One of the major obstacles in bioremediation of soils contaminated with synthetic organic compounds is the failure of laboratory remediation schemes to simulate the impact of field soil conditions on both the contaminant and the microorganism (Rao et al., 1993)- The purpose of this chapter is to introduce those topics which must be considered in order to develop an effective bioremediation strategy for soils contaminated with organic pollutants. My emphasis is on providing a comprehensive overview of the complexity of the soil system as it relates to bioremediation. 

Most soil microorganisms are inhibited by cold and freezing conditions. Low, but not freezing, temperature will slow bacterial activity. For biodeterioration to be inhibited over longer timescales, soil conditions need to be well below freezing. In the 1980s the frozen bodies of three seamen who had been buried in the Canadian arctic were exhumed. The bodies exhibited extensive soft-tissue preservation, and the textile remains were in excellent condition (Beattie 1992 Beattie and Geiger 1987). 

Sheets (5), in reviewing the disappearance of substituted urea herbicides from soil, found that inactivation occurs under soil conditions favorable for the growth of microorganisms but takes place slowly or not at all in dry or autoclaved soil. Burschel and Freed (6), reviewing work relating to 2,4-D and amitrole as well as monuron, state that the data indicate that ultimate breakdown is caused by microbiological attack. 

Figure 2 presents a schematic of one scenario in which nonionic surfactant may assist biomineralization. In this situation micellar nonionic surfactant has solubilized HOC from soil. As microorganisms deplete aqueous-phase HOC via mineralization, the micelle releases HOC to solution. HOC exit rates from micelles may be significantly faster than HOC desorption rates from soil, and this condition thereby potentially enhances the availability of HOC to the microorganism. Other researchers (25, 28) suggested that surfactants may make HOCs more available for microbial attack in soil by decreasing the interfacial tension between the compound and water. 

Hydrazines can also dissolve in water or bind to soil. The extent to which these processes occur depends on soil and water conditions. Hydrazines can move with water through soil as it flows underground. This is particularly true in sandy soils. In water and soil, some microorganisms (tiny plants or animals) can break down hydrazines to form less toxic compounds. Most of the hydrazines in soil and water are gone within a few weeks. 

Kimura M, Toyota K, Iwatsuki M, Sawada H (1994) Effects of soil conditions on biodegradation of plastics and responsible microorganisms. In Doi Y, Fukuda K (eds) Biodegradable Plastics and Polymers. Elsevier, pp 92-108... 

Spring-tails (Colembola) follow the Acarina in order of occurrence. The soil species are several mm long, and they occur under various soil conditions. They eat microorganisms, dead plants, residues and excreta of animals some species are predators. The spring-tails are considered to be important co-producers of humus. 

Under most soil conditions it is the aerobic microflora that is responsible for the formation of aggregating substances, but Harris et al. (1963) showed that the anaerobic microorganisms also possess this ability. This is shown in Fig. 16.1, taken from their publication. In this experiment the stability of artificial sucrose-amended soil aggregates was determined under both aerobic and anaerobic conditions. Under aerobic conditions aggregate stability increased rapidly for 4 days to 80% and then fell nearly as rapidly to zero stability after 12 days. Under anaerobic conditions aggregate stability increased... 

Nitrification in wetlands is restricted to aerobic zones of soil and water column or under drained soils conditions, where ammonium is oxidized to nitrate. Nitrification reaction supports denitrification by supplying heterotrophs with nitrate as their electron acceptor. In a broader sense, nitrification is defined as the conversion of organic or inorganic compounds from reduced state to a more oxidized state. Three groups of microorganisms are capable of oxidizing ammonium under aerobic conditions ... 

Pipelines are exposed to aggressive soil environments, varying climate conditions, microorganisms, and stray currents that initiate corrosion processes. Research carried out in the last several decades indicated cathodic protection is the most promising protection method for pipelines [1,2]. Basic information on cathodic protection is well documented in several textbooks and handbooks [3-9]. 

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