Per Rosenberg

Combustion char morphology related to combustion temperature and coal petrography

Abstract The morphology of chars sampled from various laboratory-scale reactors operating at temperatures from 800 to > 1400°C, together with chars collected directly in the flame zone in a full-scale pulverized fuel combustion experiment, was examined. A coal and coal blend dominated by vitrinite-rich microlithotypes together with four coals dominated by inertinite-rich microlithotypes were used to produce the combustion chars. Char samples produced at temperatures above ∼1300°C have a morphotype composition very similar to the composition of the full-scale char samples, whereas the morphotype compositions of those produced at ∼1150°C or lower are significantly different. Correlation between coal petrography and char morphology and determination of char reactivity should thus be attempted only using chars produced at temperatures comparable with those for the intended use of the coal. A clear distinction between the high-temperature char samples (burnout 50–60 wt% daf) emerges which is related mainly to the parent coal petrography and probably secondarily to the rank. Vitrite, clarite and vitrinertite V may be correlated with the porous tenuisphere and crassisphere morphotypes, whereas inertite, durite, vitrinertite I, duroclarite and clarodurite may be correlated with the crassinetwork-mixed-network-mixed morphotype group.

Bacterial diversity and community structure of a sub‐surface aquifer exposed to realistic low herbicide concentrations

An increasing number of herbicides are found in our groundwater environments. This underlines the need for examining the effects of herbicide exposure on the indigenous groundwater microbial communities, as microbial degradation is the major process responsible for the complete removal of most contaminants. We examined the effect of in situ exposure to realistic low concentrations of herbicides on the microbial diversity and community structure of sub-surface sediments from a shallow aquifer near Vejen (Denmark). Three different community analyses were performed: colony morphology typing, sole-carbon source utilisation in Biolog EcoPlates, and denaturing gradient gel electrophoresis. Cluster analysis demonstrated that the microbial communities of those aquifer sediments that acclimated to the herbicide exposure also had similar community structure. This observation was concurrent for all three community analyses. In contrast, no significant effect was found on the bacterial diversity, except for the culturable fraction where a significantly increased richness and Shannon index was found in the herbicide acclimated sediments. The results of this study show that in situ exposure of sub-surface aquifers to realistic low concentrations of herbicides may alter the overall structure of a natural bacterial community, although significant effects on the genetic diversity and carbon substrate usage cannot be detected. The observed impact was probably due to indirect effects. In future investigations, the inclusion of methods that specifically detect relevant microbial sub-populations and functional genes is therefore recommended.

Organic Geochemistry in Relation to the Depositional Environments of Middle Jurassic Coal Seams, Danish Central Graben, and Implications for Hydrocarbon Generative Potential

Middle Jurassic strata from the Harald gas field in the Danish Central Graben include five coal seams. The precursor mires were situated in coastal plain environments, and peat formation occurred during water table rise related to relative sea level rise. In a sequence stratigraphic framework, the seams are situated at the transition zone between the lowstand and transgressive systems tracts or in the transgressive systems tract close to a level that can be correlated with the maximum flooding surface. Influence from relative sea level rise on peat accumulation is reflected in the petrographic and organic geochemical composition of the seams. The coals that represent peat accumulation during rapid relative sea level rise are characterized by a higher average hydrogen inde , extractability, hydrocarbon yield, and thermally extracted and generated bitumen content (S1+S2) compared to the coals that represent peat formation during the initial stages of relative sea level rise (slow rate of water table rise). In the latter coals, Pr/Ph ratios are higher, and the content of C29 steranes is higher and the content of C27 is lower. With regard to thermal maturity, the coals are in the oil window and may possess the potential to generate and release liquid hydrocarbons. This is supported by the composition of oil samples derived from sandstones in the Harald field. Multivariate data analysis shows a positive correlation between S1+S2, which is taken to indicate the generative potential of the coals, nd in particular the macerals telinite, telocollinite, and cutinite, the microlithotypes vitrite and clarite, and total organic carbon. Such a petrographic composition is favored in precursor mires characterized by continuously waterlogged, anoxic conditions. These conditions are best met in mires situated on the lower coastal plain during rapid relative sea level rise. The knowledge obtained from multivariate modeling of the data, and sedimentological and sequence stratigraphic interpretations of the coal-bearing strata, may thus make it possible to locate the coals with the highest generative potential.

Variation of MCPA, metribuzine, methyltriazine-amine and glyphosate degradation, sorption, mineralization and leaching in different soil horizons

Pesticide mineralization and sorption were determined in 75 soil samples from 15 individually drilled holes through the vadose zone along a 28km long transect of the Danish outwash plain. Mineralization of the phenoxyacetic acid herbicide MCPA was high both in topsoils and in most subsoils, while metribuzine and methyltriazine-amine was always low. Organic matter and soil pH was shown to be responsible for sorption of MCPA and metribuzine in the topsoils. The sorption of methyltriazine-amine in topsoil was positively correlated with clay and negatively correlated with the pH of the soil. Sorption of glyphosate was tested also high in the subsoils. One-dimensional MACRO modeling of the concentration of MCPA, metribuzine and methyltriazine-amine at 2m depth calculated that the average concentration of MCPA and methyltriazine-amine in the groundwater was below the administrative limit of 0.1mug/l in all tested profiles while metribuzine always exceeded the 0.1mug/l threshold value.

Spatial Variation in 2-Methyl-4-chlorophenoxyacetic Acid Mineralization and Sorption in a Sandy Soil at Field Level

The phenoxyacetic acid herbicide MCPA (2-methyl-4-chlorophenoxyacetic acid) is frequently detected in groundwater beneath Danish agricultural fields. We investigated spatial variation in microbial MCPA mineralization potential in a flat agricultural field of fine sandy soil (USDA classification: Humic Dystrudept) located on the Yoldia plains of Northern Jutland, Denmark. Samples for determination of MCPA mineralization and sorption were collected from the Ap and Bs horizons at 51 sampling sites located in a 200 x 220 m grid. Spatial variation in sorption was low in both horizons (distribution coefficient, 0.36-4.16 L kg(-1)). Sorption correlated strongly with soil organic carbon content in both horizons (CV, 93 and 83%, respectively) and negatively with soil pH. [Ring-(14)C]-MCPA mineralized readily in the Ap horizon, with 49 to 62% of the (14)C-MCPA being converted to (14)CO(2) during the 67-d incubation period. With the subsoil, mineralization of (14)C-MCPA varied considerably between samples (0.5-72.8%). At neither depth was there correlation between (14)C-MCPA mineralization and sorption, soil pH, organic carbon content, clay content, number of colony-forming units (CFU), pseudomonad CFU, or any of the four microbial activity parameters measured. The presence of microbial genes encoding for the TfdA enzyme was quantified using real-time polymerase chain reaction. No correlation was found between MCPA mineralization potential and the natural background number of tfdA genes present in the soil samples. The degradation kinetics suggests that the high (14)C-MCPA mineralization rate detected in soil samples was linked to growth of the MCPA-degrading soil microbial community.

Evaluation of the chemical properties of coals and their maceral group constituents in relation to combustion reactivity using multi-variate analyses

Abstract The factors affecting the combustion rates of coals have been investigated using multivariate analysis. Coals from Australia, Colombia, Germany, UK and USA and their separated maceral group constituents were subjected to detailed optical and chemical characterisation followed by the measurement of combustion reactivity at low temperatures (up to 1323 K) using TGA, and at high temperatures (1300–1900 K) in an entrained flow reactor. The derived activation energies and pre-exponential factors were used in conjunction with eighty-six detailed chemical and petrographic parameters as the basis for statistical analysis. This demonstrated that the parameters which significantly influence the combustion rate could be used to divide the coals and maceral groups into two classes. One class containing predominantly the northern hemisphere coals with their corresponding maceral groups and the other containing the Australian and Colombian coals with their maceral groups. No significant relationships were found between the reactivity of the coals and the maceral groups within the coal, or between the same maceral group for all the coals. However the chemical composition of the organic matter content was found to be an important parameter in determining coal reactivity and such information could be used to supplement classical petrographical classification and proximate and ultimate analyses in order to predict the reactivity of a given coal. The effect of ash on the burning rate of the individual maceral components was also investigated and the implications for burnout in practical combustion systems discussed.

Impact of Basic Soil Parameters on Pesticide Disappearance Investigated by Multivariate Partial Least Square Regression and Statistics

Dissipation time is a key parameter when studying and modeling the environmental fate of pesticides. This study was conducted to characterize the variability of pesticide disappearance in soil and to identify possible controlling parameters related to intrinsic soil properties and microbiology. Multivariate data analysis was used to study spatial variability in three horizons from 24 sandy soil profiles. The time for 50% disappearance (DT(50)) was characterized for two herbicides, metribuzin (MBZ) and MCPA, and methyltriazine amine (MTA; transformation product of metsulfuron-methyl, tribenuron-methyl, thifensulfuron-methyl, and chlorsulfuron). Normal and log-normal distributions were compared for DT(50) and soil properties and descriptive statistics were calculated. Conformity with log-transformed distributions was observed and assuming normality of the DT(50) data would cause 5 to 35% overestimation. Mean DT(50) were: MCPA 9.5, MBZ 168, and MTA 127. Significant effect of soil depth on DT(50) was shown for MCPA and MBZ, with low values in deeper horizons. Simple linear correlation for combinations of MCPA, MTA, pH, and total organic carbon (TOC) was observed. Using partial least squares regression (PLS) 71 to 85% of the total DT(50) variance was explained. A specific predictor variable could not be identified as the controlling components differed within horizons and compounds. For MCPA the overall important predictor variables were microbiology and TOC, whereas for MTA and MBZ it was inorganic variables (Al, Fe, cation exchange capacity, base saturation percent, and pH) and microbiology. The study indicates that PLS generated input data can improve pesticide fate modeling and reduce the uncertainty in dissipation estimation.