Microbial activity, measured as CO 2 –C evolution, was constant over the period of incubation. The cumulative CO 2 –C evolution ranged between 23 and 32 mg g −1 OM (Fig. 1a).However, there was no significant effect of the substrate nor of the 15 N application rate on cumulative CO 2 –C evolution. Soil microbial biomass C decreased during the time of incubation (P < 0.001) and was ...
Ahamed Ashiq, Meththika Vithanage, in Agrochemicals Detection, Treatment and Remediation, 2020. 23.3.2 Microorganism community and activity. Soil microbial activity, soil bacteria-to-fungi ratio, and soil enzymatic activities change to a significant extent in biochar-amended soils, and this shapes the whole microbial community entities of soil.With several techniques utilized to test the ...
A minute life form; a microorganism, especially a bacterium that causes disease. Not in technical use.
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Microbial activity continues for many years even after the geochemical phase gets under way so long as pressure and temperature are not excessive. Microbial activity can be of fungal, aerobic, or anaerobic type. The first two need oxygen and cause complete plant decay.
The use of sealed microcosms allows for the measurement of microbial activity within the sample as determined by the flux of CO 2 and/or O 2 within the headspace atmosphere. Headspace gas samples can be withdrawn using a gastight syringe, and the CO 2 or O 2 concentrations can be determined using gas chromatography. An alternative method is to trap the CO 2 produced in a basic solution using a trap such as that shown in Figure 11.10. One problem that can arise during long-term incubation periods is the depletion of oxygen within the headspace of sealed, airtight flasks. To address this problem, flow-through incubation systems have been devised to allow headspace gases to be replenished, while still allowing quantification of microbial respiration. In this case, CO 2 -free air is used as the flow-through gas, and any CO 2 in the air exiting the flask is a direct result of microbial activity. The CO 2 in the effluent air can be trapped in alkali and quantified or fed directly into a CO 2 detection device, such as an infrared detector ( Brooks and Paul, 1987 ). A second problem in some alkaline soils is that CO 2 evolution may be underestimated, because the equilibrium shown in Eq. 11.2 is dependent on pH. In soils with a pH above 6.5, a significant portion of the CO 2 produced by mineralization will be retained in the soil in the bicarbonate ( HCO 3 −) form. Flow-through systems, which provide continuous replenishment of the atmosphere within the incubation flasks, reduce the retention of CO 2 in the soil by maintaining a low concentration of CO 2 in the atmosphere of the microcosm.
Microbial respiration is a measure of microbial activity that integrates the effects of microbial biomass accumulation over time, community composition, and environmental factors such as temperature and nutrient availability. Microbial respiration tends to vary with the quality of organic matter (e.g., leaf species; Fig. 27.5 ). While microbial respiration is commonly expressed as the production of CO 2, it is measured more readily as the consumption of dissolved oxygen in either the laboratory or field using a dissolved oxygen probe ( Niyogi et al., 2001; Carlisle and Clements, 2005; Griffiths and Tiegs, 2016 ). The following is a protocol used to quantify respiration (as oxygen consumption) by aquatic microbial communities that are growing on submerged leaf litter.
Microbial activity has the potential to change the physical and (geo)chemical conditions of an environment . In a geological repository for nuclear waste, this could have an impact on radionuclide mobility. Intermediate-level radioactive waste that requires geological disposal typically contains a variety of organic compounds, which are prone to degradation. The organic compounds themselves can be prone to microbial degradation. More importantly, chemical and radiolytical degradation processes will result in short-chain organic degradation products and the formation of hydrogen. These can in turn be used as electron donors to stimulate microbial activity with electron acceptors present in the pore waters of host formations or in the waste. This chapter gives an overview of chemical, radiolytical, and microbial degradation processes of cellulose, PVC, ion exchange resins, and bitumen, important organics present in European radioactive waste inventories.
Microbial activity is closely linked with gas hydrate occurrences in ocean sediments. An optimum temperature range promotes microbial activity and an extreme upper temperature range reduces the activity, so the sediment thermal gradient influences microbial activity throughout the hydrate zone and even beyond.
Microbial activities represent the instability factor that is the most difficult to control at the stage of RM preparation, in particular for food and environmental RMs. During treatment, it is, therefore, of paramount importance to eliminate or control the microbial activity either by killing the microorganisms or by stopping their activity for a given period.
Bacterial activity, coupled with geological processes, altered the chemical environment of Earth’s surface so that it was conducive for the evolution of multicellular life forms . The evolution of oxygenic photosynthesis in cyanobacteria was undoubtedly the single most important step, since the origin of oxygenic photosynthesis gave rise to an O 2 -containing atmosphere without which multicellular organisms cannot survive. Many key processes of the biosphere are still carried out exclusively by bacteria and the major biogeochemical cycling of elements would likely proceed much as they do today – even if eukaryotes had never evolved.
Microbial activity continues for many years even after the geochemical phase gets under way so long as pressure and temperature are not excessive. Microbial activity can be of fungal, aerobic, or anaerobic type. The first two need oxygen and cause complete plant decay.
The use of sealed microcosms allows for the measurement of microbial activity within the sample as determined by the flux of CO 2 and/or O 2 within the headspace atmosphere. Headspace gas samples can be withdrawn using a gastight syringe, and the CO 2 or O 2 concentrations can be determined using gas chromatography. An alternative method is to trap the CO 2 produced in a basic solution using a trap such as that shown in Figure 11.10. One problem that can arise during long-term incubation periods is the depletion of oxygen within the headspace of sealed, airtight flasks. To address this problem, flow-through incubation systems have been devised to allow headspace gases to be replenished, while still allowing quantification of microbial respiration. In this case, CO 2 -free air is used as the flow-through gas, and any CO 2 in the air exiting the flask is a direct result of microbial activity. The CO 2 in the effluent air can be trapped in alkali and quantified or fed directly into a CO 2 detection device, such as an infrared detector ( Brooks and Paul, 1987 ). A second problem in some alkaline soils is that CO 2 evolution may be underestimated, because the equilibrium shown in Eq. 11.2 is dependent on pH. In soils with a pH above 6.5, a significant portion of the CO 2 produced by mineralization will be retained in the soil in the bicarbonate ( HCO 3 −) form. Flow-through systems, which provide continuous replenishment of the atmosphere within the incubation flasks, reduce the retention of CO 2 in the soil by maintaining a low concentration of CO 2 in the atmosphere of the microcosm.
Microbial respiration is a measure of microbial activity that integrates the effects of microbial biomass accumulation over time, community composition, and environmental factors such as temperature and nutrient availability. Microbial respiration tends to vary with the quality of organic matter (e.g., leaf species; Fig. 27.5 ). While microbial respiration is commonly expressed as the production of CO 2, it is measured more readily as the consumption of dissolved oxygen in either the laboratory or field using a dissolved oxygen probe ( Niyogi et al., 2001; Carlisle and Clements, 2005; Griffiths and Tiegs, 2016 ). The following is a protocol used to quantify respiration (as oxygen consumption) by aquatic microbial communities that are growing on submerged leaf litter.
Microbial activity has the potential to change the physical and (geo)chemical conditions of an environment . In a geological repository for nuclear waste, this could have an impact on radionuclide mobility. Intermediate-level radioactive waste that requires geological disposal typically contains a variety of organic compounds, which are prone to degradation. The organic compounds themselves can be prone to microbial degradation. More importantly, chemical and radiolytical degradation processes will result in short-chain organic degradation products and the formation of hydrogen. These can in turn be used as electron donors to stimulate microbial activity with electron acceptors present in the pore waters of host formations or in the waste. This chapter gives an overview of chemical, radiolytical, and microbial degradation processes of cellulose, PVC, ion exchange resins, and bitumen, important organics present in European radioactive waste inventories.
Microbial activity is closely linked with gas hydrate occurrences in ocean sediments. An optimum temperature range promotes microbial activity and an extreme upper temperature range reduces the activity, so the sediment thermal gradient influences microbial activity throughout the hydrate zone and even beyond.
Microbial activities represent the instability factor that is the most difficult to control at the stage of RM preparation, in particular for food and environmental RMs. During treatment, it is, therefore, of paramount importance to eliminate or control the microbial activity either by killing the microorganisms or by stopping their activity for a given period.
Bacterial activity, coupled with geological processes, altered the chemical environment of Earth’s surface so that it was conducive for the evolution of multicellular life forms . The evolution of oxygenic photosynthesis in cyanobacteria was undoubtedly the single most important step, since the origin of oxygenic photosynthesis gave rise to an O 2 -containing atmosphere without which multicellular organisms cannot survive. Many key processes of the biosphere are still carried out exclusively by bacteria and the major biogeochemical cycling of elements would likely proceed much as they do today – even if eukaryotes had never evolved.