Measure Of Microbial Activity Research Articles

Stability and maturity of thickened wastewater sludge treated in pilot-scale sludge treatment wetlands

Thickened wastewater activated sludge was treated in 13 pilot-scale sludge treatment wetlands of various configurations that operated continuously for three years in North Greece. Sludge was loaded for approximately 2.5 years, and the beds were left to rest for the remaining period. Three different sludge loading rates were used that represented three different population equivalents. Residual sludge stability and maturity were monitored for the last year. Sludge was regularly sampled and microbial respiration activity indices were measured via a static respiration assay. The phytotoxicity of sludge was quantified via a seed germination bioassay. Measurements of total solids, organic matter, total coliforms, pH and electrical conductivity were also made. According to microbial respiration activity measurements, the sludge end-product was classified as stable. The germination index of the final product exceeded 100% in most wetland units, while final pH values were approximately 6.5. The presence of plants positively affected the stability and maturity of the residual sludge end-product. Passive aeration did not significantly affect the quality of the residual sludge, while the addition of chromium at high concentrations hindered the sludge decomposition process. Conclusively, sludge treatment wetlands can be successfully used, not only to dewater, but also to stabilize and mature wastewater sludge after approximately a four-month resting phase.

Improved measurement of microbial activity in deep‐sea sediments at in situ pressure and methane concentration

A robust and convenient method was developed to evaluate rates of microbial activity in gas‐charged deepsea sediments at in situ hydrostatic pressure, temperature, and gas concentration. The method used a hydrostatic chamber to maintain high pressures of 50 bar and greater, and a modified Hungate tube and plunger to contain samples. This technique can be easily applied to quantifying rates of microbial processes sensitive to dissolved gas concentration (e.g., sulfate reduction, anaerobic methane oxidation, and methanogenesis) in high pressure, gas‐rich environments. Here, the method was used to determine rates of microbial activity in cold seep sediments from the Gulf of Mexico and the California coast. We measured rates of sulfate reduction (SR), anaerobic oxidation of methane (AOM), and methanogenesis (MOG) using radiotracer techniques. We compared in situ pressure and elevated methane concentration assays to traditional ex situ incubations at 1 bar using recovered (degassed) sediment. Methane concentrations were elevated in ex situ incubations to assess a substrate level effect. Upon the application of pressure, rates of AOM, SR, and MOG increased. AOM and MOG rates were more sensitive to methane addition than SR. Our results show that measuring rates of deep‐sea microbial activity at in situ pressure and gas concentrations is essential to quantify carbon flow in these environments accurately.

Effects of Temperature and Site Characteristics on Phosphorus Dynamics in Four Restored Wetlands: Implications for Wetland Hydrologic Management and Restoration

Restoring historic lake-fringe wetlands is considered a favorable means of reducing lake phosphorus levels; however, it is unclear how various strategies for managing wetland connectivity influence phosphorus release. We investigated the relationships between temperature and soil characteristics of restored wetlands to identify management strategies that minimize external phosphorus loading to Upper Klamath and Agency Lakes. We flooded soil cores at various temperatures and analyzed them for several forms of phosphorus and other physical properties. We compared measures of microbial activity and physical characteristics of phosphorus fractions within the wetland soils to forms of phosphorus in water relevant to phosphorus-loading in the lakes. Greater release rates of total phosphorus occurred in summer temperature treatments for all study wetlands (average 31.81 to 240.61 mg/m2 /d), while release rates of soluble reactive phosphorus (average −15.9 to 62.19 mg/m2 /d) varied with temperature and soil characteristics. Wetlands with mineral soils and direct hydrologic connectivity to the lakes released the lowest concentrations of total phosphorus, while soluble reactive phosphorus release varied across management strategies and soil types. These differences can be explained by the dominant phosphorus processes associated with the hydrology and biogeochemistry of the individual sites, and temperature and potential for microbial activity at the timing of inundation. Our results provide evidence that directly connected wetlands may release less phosphorus than indirectly or mechanically connected wetlands, due to early timing of inundation and longer duration of inundation.

Submersible microbial fuel cell sensor for monitoring microbial activity and BOD in groundwater: Focusing on impact of anodic biofilm on sensor applicability

A sensor, based on a submersible microbial fuel cell (SUMFC), was developed for in situ monitoring of microbial activity and biochemical oxygen demand (BOD) in groundwater. Presence or absence of a biofilm on the anode was a decisive factor for the applicability of the sensor. Fresh anode was required for application of the sensor for microbial activity measurement, while biofilm-colonized anode was needed for utilizing the sensor for BOD content measurement. The current density of SUMFC sensor equipped with a biofilm-colonized anode showed linear relationship with BOD content, to up to 250 mg/L (∼233 ± 1 mA/m(2)), with a response time of <0.67 h. This sensor could, however, not measure microbial activity, as indicated by the indifferent current produced at varying active microorganisms concentration, which was expressed as microbial adenosine-triphosphate (ATP) concentration. On the contrary, the current density (0.6 ± 0.1 to 12.4 ± 0.1 mA/m(2)) of the SUMFC sensor equipped with a fresh anode showed linear relationship, with active microorganism concentrations from 0 to 6.52 nmol-ATP/L, while no correlation between the current and BOD was observed. It was found that temperature, pH, conductivity, and inorganic solid content were significantly affecting the sensitivity of the sensor. Lastly, the sensor was tested with real contaminated groundwater, where the microbial activity and BOD content could be detected in <3.1 h. The microbial activity and BOD concentration measured by SUMFC sensor fitted well with the one measured by the standard methods, with deviations ranging from 15% to 22% and 6% to 16%, respectively. The SUMFC sensor provides a new way for in situ and quantitative monitoring contaminants content and biological activity during bioremediation process in variety of anoxic aquifers.

Kinetics of model high molecular weight organic compounds biodegradation in soil aquifer treatment

Soil Aquifer Treatment (SAT) is a process where treated wastewater is purified during transport through unsaturated and saturated zones. Easily biodegradable compounds are rapidly removed in the unsaturated zone and the residual organic carbon is comprised of primarily high molecular weight compounds. This research focuses on flow in the saturated zone where flow conditions are predictable and high molecular weight compounds are degraded. Flow through the saturated zone was investigated with 4 reactors packed with 2 different particle sizes and operated at 4 different flow rates. The objective was to evaluate the kinetics of transformation for high molecular weight organics during SAT. Dextran was used as a model compound to eliminate the complexity associated with studying a mixture of high molecular weight organics. The hydrolysis products of dextran are easily degradable sugars. Batch experiments with media taken from the reactors were used to determine the distribution of microbial activity in the reactors. Zero-order kinetics were observed for the removal of dextran in batch experiments which is consistent with hydrolysis of high molecular weight organics where extracellular enzymes limit the substrate utilization rate. Biomass and microbial activity measurements demonstrated that the biomass was independent of position in the reactors. A Monod based substrate/biomass growth kinetic model predicted the performance of dextran removal in the reactors. The rate limiting step appears to be hydrolysis and the overall rate was not affected by surface area even though greater biomass accumulation occurred as the surface area decreased.

Recovery of Phenanthrene-Degrading Bacteria after Simulated in Situ Persulfate Oxidation in Contaminated Soil

A continuous-flow column study was conducted to investigate the long-term effects of persulfate oxidation on the abundance and activity of the indigenous microbial community and phenanthrene-degrading bacteria in contaminated soil from a former manufactured gas plant (MGP) site. Approximately six pore volumes of a 20 g/L persulfate solution were introduced into the column, followed by simulated groundwater for 500 days. Soil samples were collected from the surface of the soil bed and along the column length immediately before and after persulfate injection and up to 500 days following injection. Exposure to persulfate led to a 2- to 3-log reduction in total bacterial 16S rRNA genes, severe inhibition of (14)C-acetate mineralization (as a measure of general microbial activity), and a decrease in community diversity. However, relatively rapid recovery of both bacterial gene abundance and activity was observed within 30 days after persulfate exposure. Mineralization of (14)C-phenanthrene was also inhibited but did not recover until 100 days postoxidation. Known phenanthrene-degrading bacterial groups decreased to below detection limits throughout the column, with recovery times from 100 to 500 days after persulfate injection. These findings suggest that coupling biological processes with persulfate oxidation is possible, although recovery of specific contaminant degraders may occur much later than the general microbial community recovers. Furthermore, the use of total bacterial quantity or nonspecific measures of activity as a surrogate for the recovery of contaminant degraders may be inappropriate for evaluating the compatibility of chemical treatment with subsequent bioremediation.

Detection and quantification of microbial activity in the subsurface

The subsurface harbors a large fraction of Earth’s living biomass, forming complex microbial ecosystems. Without a profound knowledge of the ongoing biologically mediated processes and their reaction to anthropogenic changes it is difficult to assess the long-term stability and feasibility of any type of geotechnical utilization, as these influence subsurface ecosystems. Despite recent advances in many areas of subsurface microbiology, the direct quantification of turnover processes is still in its infancy, mainly due to the extremely low cell abundances. We provide an overview of the currently available techniques for the quantification of microbial turnover processes and discuss their specific strengths and limitations. Most techniques employed so far have focused on specific processes, e.g. sulfate reduction or methanogenesis. Recent studies show that processes that were previously thought to exclude each other can occur simultaneously, albeit at very low rates. Without the identification of the respective processes it is impossible to quantify total microbial activity. Even in cases where all simultaneously occurring processes can be identified, the typically very low rates prevent quantification. In many cases a simple measure of total microbial activity would be a better and more robust measure than assays for several specific processes. Enzyme or molecular assays provide a more general approach as they target key metabolic compounds. Depending on the compound targeted a broader spectrum of microbial processes can be quantified. The two most promising compounds are ATP and hydrogenase, as both are ubiquitous in microbes. Technical constraints limit the applicability of currently available ATP-assays for subsurface samples. A recently developed hydrogenase radiotracer assay has the potential to become a key tool for the quantification of subsurface microbial activity.

The effects of substrate composition, quantity, and diversity on microbial activity

Variation in organic matter inputs caused by differences in plant community composition has been shown to affect microbial activity, although the mechanisms controlling these effects are not entirely understood. In this study we determine the effects of variation in substrate composition, quantity, and diversity on soil extracellular enzyme activity and respiration in laboratory microcosms. Microbial respiration responded predictably to substrate composition and quantity and was maximized by the addition of labile substrates and greater substrate quantity. However, there was no effect of substrate diversity on respiration. Substrate composition significantly affected enzyme activity. Phosphatase activity was maximized with addition of C and N together, supporting the common notion that addition of limiting resources increases investment in enzymes to acquire other limiting nutrients. Chitinase activity was maximized with the addition of chitin, suggesting that some enzymes may be stimulated by the addition of the substrate they degrade. In contrast, activities of glucosidase and peptidase were maximized by the addition of the products of these enzymes, glucose and alanine, respectively, for reasons that are unclear. Substrate diversity and quantity also stimulated enzyme activity for three and four of the six enzymes assayed, respectively. We found evidence of complementary (i.e., non-additive) effects of additions of different substrates on activity for three of the six enzymes assayed; for the remaining enzymes, effects of adding a greater diversity of substrates appeared to arise from the substrate-specific effects of those substrates included in the high-diversity treatment. Finally, in a comparison of measures of microbial respiration and enzyme activity, we found that labile C and nutrient-acquiring enzymes, not those involved in the degradation of recalcitrant compounds, were the best predictors of respiration rates. These results suggest that while composition, quantity, and diversity of inputs to microbial communities all affect microbial enzyme activity, the mechanisms controlling these relationships are unique for each particular enzyme.

Can Stability and Maturity Be Evaluated in Finished Composts from Different Sources?

A combination of physical, chemical, spectroscopic and biochemical parameters, along with different plant assays, was used to assess the maturity and stability of nine finished composts obtained from several raw materials (biodegradable fraction of municipal solid waste, green waste, sewage sludge, manure, and grape marc), and by different procedures (aerobic and anaerobic processing, industrial-scale and laboratory scale). Measures of total, alkali-soluble and water-soluble organic matter, N forms, colour, absorbance, respiration, dehydrogenase activity, and phytotoxicity were performed. The selection of a single parameter for stability and maturity evaluation for all the composts was not possible. A significant positive correlation (P<0.01) was found between microbial respiration and dehydrogenase activity. Also, significant correlations were found between dehydrogenase activity and water-soluble C (P<0.05) and water-soluble N (P<0.05), which are presumably the main forms of energy used by microorganisms. Nevertheless, common maturity/stability indicators, such as the C/N ratio in the solid and the aqueous phase, were not related either to microbial activity or phytotoxicity. In fact, the results of the plant growth tests were not correlated to any other parameter. A principal component analysis was performed to differentiate those parameters giving the maximum information about the status of each compost. A combination of a measure of humification and a measure of microbial activity or water-soluble organic carbon could be used to explain the differences in the stability of the composts, whereas for maturity evaluation plant tests are necessary.

Is cotton-strip tensile strength a surrogate for microbial activity in groundwater?

The cotton strip assay uses the loss of tensile strength of cotton strips as a measure of microbial cellulolytic activity. Its suitability for measuring general microbial activity in groundwater was tested by examining the relationship of tensile strength, abundance of cellulolytic organisms and general microbial activity on cotton strips deployed in bores. The hypothesis was that the strength of cotton strips would decline with increasing abundance and activity of cellulolytic organisms, and as cellulolysis makes resources available to other microbial groups, cotton strength loss should also be related to increased overall microbial activity. The correlation between the abundance of cellulolytic organisms and cotton strength was not significant. Two main factors influenced this relationship: (i) effectiveness of the media in detecting cellulolytic moulds and (ii) inter-community interactions. After accounting for the presence of moulds through partial correlation, the relationship between tensile strength and abundance of cellulolytic organisms was stronger and significant. Both cotton strength and abundance of cellulolytic organisms correlated significantly with general microbial activity. These results support the use of the cotton strip assay, and cotton tensile strength as a surrogate for microbial activity in groundwater.

Use of microbial activity measurements for monitoring RBC biofilms

Fixed biomass technologies, such as rotating biological contactors or biodiscs, have been applied for wastewater depuration both in large and medium-small-sized agglomerations. Biofilm's composition and microorganism activity are essential parameters for the successful operation and control of these systems. Biofilm's thickness and total dry weight have been widely used for biofilm's characterization but, actually, are not sufficient to describe biofilm activity. In fact, biofilm's activity is not proportional to the quantity of fixed biomass, but increases with the thickness of biofilm up to a determined level called the "active thickness". Above this level, the diffusion of nutrients through the film becomes a limiting factor. A stable, thin, and active biofilm thus offers numerous advantages in water and wastewater treatment. Different parameters have been used to evaluate biofilm's activity. The specific oxygen uptake rate, INT-dehydrogenase activity, and the ratio active/total cells have been applied for that purpose. These methods are not only simple and rapid but also sensitive, precise, and representative. The results obtained confirm the potential of the microbial activity measurements studied for an accurate biofilm's characterization and biomass activity estimation in fundamental research and for the practical operation and control of fixed biomass depuration systems.

Organic Fertilizers for Greenhouse Tomatoes: Productivity and Substrate Microbiology

Organic fertilizer regimens consisting of combinations of composts (yard waste, swine manure, or spent mushroom substrate) and liquid fertilizers (fish- or plant-based) were evaluated against conventional hydroponic fertilizers in two experiments with greenhouse tomatoes grown in peat-based substrate. Crop yield and fruit quality were evaluated and several assays of substrate microbial activity and community profiles (fluorescein diacetate analysis and EcoLog, values, nematode counts) were conducted. Crops grown in 20% to 40% compost (yard waste or yard waste plus swine manure) plus a continuously applied liquid source of organic potassium (K), calcium (Ca), magnesium (Mg), and sulphate (SO4) could not be sustained more than 1 month before nutrient deficiencies became visible. Supplementation with a nitrogen (N)- and phosphorus (P)-containing plant-based liquid fertilizer at the point when plant deficiencies became apparent subsequently produced yields ≈80% that of the hydroponic control. In a second experiment, the proportion of mushroom or yard waste compost was increased to 50% of the mix, and liquid delivery of K, Ca, Mg and SO4 plus either plant-based or fish-based N- and P-containing liquid feeds was started at the date of transplanting. In this case, organic yields equal to that of the hydroponic control (8.5 kg/plant) were observed in some treatments. The most productive organic treatment was the mushroom compost supplemented with a low concentration of the plant-based liquid fertilizer. In general, organic tomatoes had a lower postharvest decay index (better shelf life) than did the hydroponic controls, possibly as an indirect consequence of overall reduced yield in those treatments. High concentrations of both organic liquid feeds resulted in lower yields as a result of treatment-induced fusarium crown and root rot. In contrast to some previous studies, those treatments showing fusarium crown and root rot also had the highest gross microbial activity. Measures of gross microbial activity and numbers of microbivorous nematodes were higher (average of 37% and 6.7 times, respectively) in compost/organic feed treatments than in the hydroponic control. Community physiological profiles of the bacterial populations, on the other hand, did not differ between organic and hydroponic treatments. Nematode populations were significantly correlated with gross microbial activity in the organic treatments.

Microbial oxygen uptake in sludge as influenced by compost physical parameters

The wide range of optimal values reported for the physical parameters of compost mixtures suggest that their interactive relationships should be investigated. The objective of this study was to examine the microbial O(2) uptake rate (OUR) in 16 sludge waste recipes, offering a range of moisture content (MC), waste/bulking agent (W/BA) ratio and BA particle size levels determined using a central composite experimental design. The 3 kg samples were maintained at a constant temperature and aeration rate for 28 days, during which a respirometer recorded O(2) uptake to provide a measure of microbial activity and biodegradability. The cumulative O(2) consumption after 14 and 28 days was found to be significantly influenced by MC, W/BA ratio, BA particle size and the interaction between MC and W/BA ratio (p<0.05). Using multivariate regression analysis, the experimental data was used to generate a model with good predictive ability for cumulative O(2) consumption after 28 days as a function of the significant physical variables (R(2)=0.84). The prediction of O(2) uptake by the model depended highly on the interaction between MC and W/BA ratio. A MC outside of the traditional 50-60% (wet basis) range still resulted in a high level of microbial O(2) uptake as long as the W/BA ratio was adjusted to maintain a suitable O(2) exchange in the sample. The evolution of OUR in the samples was also investigated, uncovering strong associations between short and long-term respirometric indices, such as peak OUR and cumulative O(2) consumption (p<0.005). Combining peak OUR data with cumulative O(2) consumption after 14 days allowed for accurate predictions of cumulative O(2) after 28 days of aeration (R(2)=0.96), implying that future studies need only run trials up to 14 days to evaluate the overall O(2) consumption or biodegradability of similar sludge mixtures.

Microbial growth efficiencies across a soil moisture gradient assessed using 13C-acetic acid vapor and 15N-ammonia gas

One integrative measurement of microbial activity in soils is the efficiency by which microbes convert assimilated carbon (C) into biomass C. This efficiency, called the microbial growth efficiency ( Y), is a key physiological characteristic that regulates soil carbon sequestration, nutrient immobilization, and greenhouse gas emissions. Changes in rainfall patterns and soil water content as the result of global climate change have the potential to influence microbial activity and lead to changes in Y and thus, nutrient cycling at the ecosystem level. Unfortunately, little information is available on how environmental variables such as soil moisture influence Y. We have developed a new method for injecting 13C-labeled carbon as acetic acid vapor into soil that will allow measurement of microbial growth efficiency (as Y C) without increasing soil moisture content. We compare Y determined with this new approach with an alternate method where injected 15N-labeled ammonia gas is used to quantify microbial N immobilization, and microbial growth efficiency is calculated based on microbial C:N and respiration rate (as Y N). We also include injections of a solution containing labeled ammonium and acetate in our experiment to compare the results of our vapor methods with more commonly employed liquid-based methods. The 13C-acetic acid vapor, which was supplied to soils with soil moisture content ranging from 0.05 to 0.21 g H 2O g −1 soil, was readily assimilated and respired by microbes. Between 0.10 and 0.21 g H 2O g −1 soil (−0.60 to −0.04 MPa), values of Y C averaged 0.46, and were significantly lower than values of Y N, with average values of 0.58. Over this range, soil moisture content had no significant effect on either Y C or Y N. However, at the lowest soil moisture content (0.05 g H 2O g −1 soil; <−6.0 MPa), Y C and Y N diverged substantially, suggesting that in very dry soils, constraints on microbial growth cause differential uptake of C and N resources.

Volatile Organic Metabolites as Indicators of Soil Microbial Activity and Community Composition Shifts

The dynamics of soil microorganisms have important implications for the response of subsurface soil ecosystems to perturbations. Traditional indicators such as functional, community, activity, and carbon and nutrient pathway methods have been used to characterize soil microbial processes and ecological function; however, many of these indicators lack the ability to measure changes over large (e.g., landscape) spatiotemporal scales in soil environments. This research introduces the analysis of soil volatile organic compound (VOC) metabolites as nondestructive indicators of subsurface microbial activity and community composition as a function of varying environmental factors. Results of method validation using laboratory microcosms are presented, where VOC metabolites as characterized by gas chromatography and mass spectrometry (GC–MS) were related to CO2 evolution as a measure of microbial activity and to community‐level physiological profiles (CLPPs) and fatty acid methyl ester (FAME) community structure techniques. Results included the identification of 72 VOC metabolites produced from the soils, where significant (ρ &lt; 0.05) differences in the estimated amounts and types of compounds produced were observed between treatments. Temporal measurements indicated similarity between VOC production and CO2 evolution, where increased amounts over time were detected. Principal component analysis (PCA) and hierarchical cluster analysis showed that the VOC results clustered similarly to FAME and CLPP results. Our results suggest there is promise for the use of naturally produced VOCs as potential indicators of soil microbial ecosystems over large spatiotemporal dynamics and environmental perturbations.

Determination of dehydrogenase activity in sediment of shallow lakes and its ecological significance

以武汉市浅水湖泊(月湖)为实验对象确定了沉积物脱氢酶活性(DHA)测定的最佳条件:以经甲醛灭菌的沉积物为对照,以氯化三苯基四氮唑为电子受体(0.4%),沉积物用量为0.5g,pH值为7.5,培养时间为3h.据上述条件测定的DHA比未优化条件下的相应值高3-5倍,且表现出与沉积物有机质含量更为显著的正相关关系.武汉东湖3个子湖共23个采样点沉积物样品的测试结果进一步证实了上述方法的可行性,同时初步揭示了湖泊沉积物脱氢酶反映微生物活性与有机质状态的生态学意义.;The samples were taken from the shallow urban lakes(Lake Yuehu) in Wuhan city to optimize the determination of dehydrogenase activity (DHA) in sediment, which gave the following suitable conditions: the sediment sterilized by formaldehyde was used as the control, the concentration of electron acceptor (2,3,5-triphenyl-2H-tetrazolium chloride) was 0.4%, the sediment amount used was 0.5g, pH value was 7.5 and the reaction time was 3h. Under these conditions, the DHA assayed was 3-5 times higher, and its positive relation to the content of organic matter in sediment was more significant, compared to those determined by the unmodified method. The data based on the 23 sites from 3 basins of Lake Donghu demonstrated the feasibility of the method. In the same time, the ecological significance of DHA was further shown in terms of the measurements of microbial activities and organic matter status in lake sediment

Applicability of the gas-permeable membrane to in situ soil gas sampling for the measurement of microbial activity in soil

Applicability of the gas-permeable membrane to in situ soil gas sampling for the measurement of microbial activity in soil

River flow controls ecological processes and invertebrate assemblages in subsurface flowpaths of an ephemeral river reach

We present the first measurements of solutes, invertebrates, and microbial activity in the semi-perched hyporheic, parafluvial, and riparian flowpaths of an ephemeral river channel. Dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) concentrations decreased as water from an adjacent river mainstem moved through the flowpaths. DOC, DON, and DOP processing rates decreased with increasing mainstem flow and increased with parafluvial zone length. These patterns suggest that the surface water zones of perched river systems are organic nutrient sources to subsurface flowpaths and that parafluvial zones of these systems are strong sinks for organic matter. No longitudinal changes were detected in NO3–concentrations, and relationships between NO3–processing and hydrological variables were not significant. NO3–concentrations were uniformly high, and microbial activity and DOC and dissolved reactive phosphorus (DRP) concentrations were low, suggesting that biological NO3–removal was carbon- or phosphorus-limited. Invertebrate assemblages also varied between subsurface zones: density and taxon richness in the hyporheic and parafluvial zones were higher than in the riparian zone, and evenness was higher in the riparian zone than in the hyporheic or parafluvial zones. Distinct invertebrate assemblages in riparian zones may reflect greater hydrologic stability compared with hyporheic and parafluvial zones.

토양 미생물 활성과 다양성에 미치는 고추 품종과 퇴비의 단기적 효과

A field experiment was conducted to investigate the influence of cultivars and compost on soil microbial activities and diversities in a red pepper-grown field. Compost was applied with 0, 30, and 60M/T in April and then red pepper seedlings of Yong-go 4 and Koeun were transplanted in May 2007. Soil samples were collected in early August 2007. Measurement of microbial activities was based on a dehydrogenase assay and a fluorescein diacetate hydrolysis. Soil microbial community was characterized with Biolog and phospholipid fatty acid(PLFA). Red pepper cultivars did not differentiate the selected soil chemical and microbial properties. Soil pH and soil microbial community changed by amending the soil with 30 and 60 M/T of compost, and the soil organic matter and potassium content, and soil microbial activities increased in soils amended with 60 M/T of compost. Red pepper cultivar induced a little different soil chemical properties and microbial activity in soils amended with 60 M/T of compost even though significant differences were not found in those properties. In conclusion the effects of compost on soil chemical and microbial properties were much higher than red pepper cultivars in short-term period but the effects of red pepper cultivars should be investigated in long-term field test.

Degradation rates of aged petroleum hydrocarbons are likely to be mass transfer dependent in the field

Evidence for on site biodegradation may be difficult to provide at heterogeneous sites without additional experiments in controlled laboratory conditions. In this study, microbial activities measured as CO2 and CH4 production were compared in situ, in intact soil cores and in bottle microcosms containing sieved soils. In addition, biodegradation rates were determined by measuring the decrease in petroleum hydrocarbon concentrations at 7 degrees C in aerobic and anaerobic conditions. Elevated concentrations of CO2 and CH4 in the soil gas phase indicated that both the aerobic and anaerobic microbial activity potentials were high at the contaminated site. Aerobic and anaerobic microbial degradation rates in laboratory experiments of petroleum hydrocarbons were highest in soils from the most contaminated point and degradation in the aerobic and anaerobic microcosms was linear throughout the incubation, indicating mass-transfer-dependent degradation. Different results for microbial activity measurements were obtained in laboratory studies depending on pretreatment and size of the sample, even when the environmental conditions were mimicked. These differences may be related to differences in the gas exchange rates as well as in changes in the bioavailability of the contaminant in different analyses. When predicting by modeling the behavior of an aged contaminant it is relevant to adapt the models in use to correspond to conditions relevant at the contaminated sites. The variables used in the models should be based on data from the site and on experiments performed using the original aged contaminant without any additions.