Biofiltration for mitigation of methane emission from animal husbandry

Removal of methane from exhaust air of animal houses and manure storage has a large potential for the reduction of greenhouse gas emissions from animal husbandry. The aim of this study was to design a biofilter for methane removal at a full-scale livestock production facility. Air from the headspace of a covered 6 m3 liquid manure storage (air flow: 0.75-8.5 m3 m(-3) h(-1); CH4: 500-5500 mg m(-3)) was treated in an experimental biofilter (160 L). The filterbed, a mixture of compost and perlite in a 40:60 (v/v) ratio, was inoculated with activated sludge that had shown a good methane oxidation rate as compared to pure cultures in preceding laboratory tests. Methane removal up to 85% could be achieved in the experimental biofilter. The methane removal (g m(-3) h(-1)) appeared to be proportional to the concentration (g m(-3)) with k = 2.5 h(-1). Relatively low methane concentrations and high air flows, as reported for the exhaust air of animal houses, would require very large biofilter sizes. Extrapolation of the results showed that treatment of air from a 1000 m3 liquid manure storage with a methane concentration of 22 g m(-3) would require a 20 m3 biofilter for a desired emission reduction of 50%. The costs for such a biofilter are USD 26 per t of CO2 equiv reduction.     

A chemometric approach for brain tumor classification using magnetic resonance imaging and spectroscopy

A new classification approach was developed to improve the noninvasive diagnosis of brain tumors. Within this approach, information is extracted from magnetic resonance imaging and spectroscopy data, from which the relative location and distribution of selected tumor classes in feature space can be calculated. This relative location and distribution is used to select the best information extraction procedure, to identify overlapping tumor classes, and to calculate probabilities of class membership. These probabilities are very important, since they provide information about the reliability of classification and might provide information about the heterogeneity of the tissue. Classification boundaries were calculated by setting thresholds for each investigated tumor class, which enabled the classification of new objects. Results on histopathologically determined tumors are excellent, demonstrated by spatial maps showing a high probability for the correctly identified tumor class and, moreover, low probabilities for other tumor classes.     

Profiling of liquid crystal displays with Raman spectroscopy: preprocessing of spectra

Raman spectroscopy is applied for characterizing paintable displays. Few other options than Raman spectroscopy exist for doing so because of the liquid nature of functional materials. The challenge is to develop a method that can be used for estimating the composition of a single display cell on the basis of the collected three-dimensional Raman spectra. A classical least squares (CLS) model is used to model the measured spectra. It is shown that spectral preprocessing is a necessary and critical step for obtaining a good CLS model and reliable compositional profiles. Different kinds of preprocessing are explained. For each data set the type and amount of preprocessing may be different. This is shown using two data sets measured on essentially the same type of display cell, but under different experimental conditions. For model validation three criteria are introduced: mean sum of squares of residuals, percentage of unexplained information (PUN), and average residual curve. It is shown that the decision about the best combination of preprocessing techniques cannot be based only on overall error indicators (such as PUN). In addition, local residual analysis must be done and the feasibility of the extracted profiles should be taken into account.     

Measuring and modeling adsorption of PAHs to carbon nanotubes over a six order of magnitude wide concentration range

Understanding the interactions between organic contaminants and carbon nanomaterials is essential for evaluating the materials' potential environmental impact and their application as sorbent. Although a great deal of work has been published in the past years, data are still limited in terms of compounds, concentrations, and conditions investigated. We applied a passive sampling method employing polyoxymethylene (POM-SPE) to gain a better understanding of the interactions between polycyclic aromatic hydrocarbons (PAHs) and multiwalled carbon nanotubes (CNTs) over a 6 orders of magnitude wide concentration range. In the low-concentration range (pg-ng L(-1)), sorption of phenanthrene and pyrene was linear on a nonlogarithmic scale. Here, sorption could thus be described using a single sorption coefficient. Isotherm fits over the entire concentration range showed that (i) monolayer sorption models described the data very well, and (ii) the CNTs sorption capacity was directly related to their surface area. Sorption coefficients for 13 PAHs (11 of which have not been reported to date) were also measured at environmentally relevant low concentrations. No competition seemed to occur in the low-concentration range and sorption affinity was directly related to the solubility of the subcooled liquid of the compounds.     

Intra- and interspecies variation in bioconcentration potential of polychlorinated biphenyls: are all lipids equal?

The variation among bioconcentration factors (BCFs) available in the literature is commonly ascribed to experimental parameters and metabolic capacity. Though bioconcentration is generally considered to be governed by partitioning processes and therefore to depend on the composition of the partition phases, the effect of lipid composition on BCFs measured for hydrophobic organic chemicals has largely escaped attention. The reason may be that the effect cannot easily be studied separately in a conventional BCF test setup and that any subtle effects will often be obscured by the variation normally observed when working with living organisms. In the present study, this variation was circumvented by substituting biota with biological homogenates, which allowed measuring chemical partitioning in a fashion that has proved successful for many other environmental matrixes (e.g., sediments, soils, carbonaceous materials). The appropriateness of using a homogenate as a representation of the organism from which it was derived was demonstrated by a good agreement between homogenate-water partition coefficients (or necroconcentration factors; NCFs) and actual BCFs for PCBs and aquatic worms. Subsequent experiments focused on the intra- and interspecies differences in lipid-normalized NCFs. Intraspecies variation was studied for aquatic worms and sticklebacks, which were acclimatized at different temperatures (5-24 °C), whereas interspecies variation was investigated by determining NCFs for eight different aquatic species. Although temperature-induced intraspecies differences were subtle (<0.16 log units), interspecies differences among lipid-normalized NCFs were as high as 0.9 log units, with homogenates of "simple" organisms showing a lower sorption capacity than those of the more "complex" species. These results suggest that the variation observed in the literature BCFs may partly be caused by differences in lipid composition and contest the usefulness of the common practice of applying generic BCFs in risk assessment of chemicals.     

Measuring picogram per liter concentrations of freely dissolved parent and alkyl PAHs (PAH-34), using passive sampling with polyoxymethylene

Passive sampling with nondepletive sorbents is receiving increasing interest because of its potential to measure freely dissolved concentrations of hydrophobic organic compounds (HOCs) at very low concentrations, as well as its potential for both laboratory use and field deployment. However, consistent approaches have yet to be developed for the majority of HOCs of environmental and regulatory interest. In the present study, a passive sampling method was developed which allows the freely dissolved concentrations of 18 parent and 16 groups of alkyl polycyclic aromatic hydrocarbons (PAHs) on the U.S. Environmental Protection Agency (USEPA)'s "PAH-34" target compound list to be measured. Commercially available 76-μm-thick polyoxymethylene (POM) was placed in sediment/water slurries and exposed for up to 126 days, with 28 days found to be sufficient to obtain equilibrium among the sediment, water, and POM phases for the target 2- to 6-ring PAHs. The POM/water partition coefficients (K(POM)) necessary to calculate freely dissolved concentrations for parent PAHs were determined in two separate laboratories (one using pure standards, and the other using coal tar/petroleum-contaminated sediments) and agreed very well. Since the so-called "16" alkyl PAHs on the PAH-34 list actually include several hundreds of isomers for which no standards exist, sediments impacted by coal tar, or spiked with a coal tar/petroleum nonaqueous phase liquid (NAPL) were also used to measure K(POM) values for each alkyl PAH cluster. The log K(POM) values ranged from ca. 3.0 to 6.2 for 2- to 6-ring parent PAHs, and correlated well with SPARC octanol/water coefficients (K(OW)) (correlation coefficient of r(2) = 0.986). However, log K(POM) values for alkyl PAHs deviated increasingly from SPARC log K(OW) values with increasing degree of alkylation. A simple empirical model that incorporates the number of carbon atoms in a PAH gave a better fit to the experimental log K(POM) values, and was used to estimate log K(POM) for alkyl PAHs that could not be directly measured. Detection limits (as freely dissolved concentrations) ranged from ca. 1 part per trillion (ng/L) for the 2-ring PAH naphthalene, down to <1 pg/L (part per quadrillion) for the 5- and 6-ring PAHs. Sorption isotherms were linear (r(2) > 0.99) over at least 4 orders of magnitude.     

Modeling maximum adsorption capacities of soot and soot-like materials for PAHs and PCBs

Recent studies have shown that not partitioning but adsorption is the main mechanism for sorption of hydrophobic organic compounds to soot and soot-like materials. For compounds that adsorb by van derWaals forces only, variation in soot-water distribution coefficients will result from differences in these forces for adsorption, as well as the maximum number of accessible sites. This maximum number of accessible sites may a priori be expected to vary due to differences in both sorbent characteristics and sorbate dimensions. In this modeling study, variation in maximum adsorption capacities is explained from sorbent and sorbate properties. Maximum adsorption capacities were calculated using (a) literature values for soot-water distribution coefficients for polycyclic aromatic hydrocarbons and polychlorobiphenyls on 10 different soot and soot-like materials and (b) Langmuir affinities for adsorption at a carbonaceous surface estimated using a recently reported method. The variation in maximum adsorption capacities could be explained by the variation in sorbent specific surface area, sorbent organic carbon content, and the sorbent-sorbate contact area. Furthermore, increasing sorbate thickness was related to a decrease in maximum adsorption capacities, which points to adsorption in micropores. Maximum adsorption capacities decreased by 1-2 orders of magnitude as the contact area increased by 50%. This points to adsorption sites being hardly larger than sorbates.     

The study on the impact of glycated pea proteins on human intestinal bacteria

The traditionally perceived function of nutrition includes supplying the consumer with the appropriate quantity and quality of substrates. As nutritional substrates, proteins are prone to spontaneously occurring non-enzymatic glycosylation (glycation) which can alter their molecular structure, making them highly bioactive. Glycated food proteins are able to modify the bacterial intestinal ecosystem, which is of great importance for the optimal usage of nutrients and maintenance of both intestinal homeostasis and balanced health status of the consumer. This study aimed to determine the impact of glycated pea proteins on the intestinal bacteria from a healthy human. The analyses were conducted with the use of experimental batch-type simulator models imitating human intestinal conditions. The glycated pea proteins affected the growth of gut commensal bacteria, particularly lactobacilli and bifidobacteria, whose levels increased significantly. There was a corresponding shift in the bacterial metabolites with increased levels of the short chain fatty acids (SCFAs); acetate, propionate lactate and butyrate. Intestinal bacteria were able to utilize these pea proteins thus indicating that the energy encrypted in glycated pea proteins, partially inaccessible for gastric enzymes, may be salvaged by gut microbiota. Such changes in microbial composition may beneficially impact the intestinal environment and exert a health-promoting effect in humans.     

Blood plasma sample preparation method for the assessment of thyroid hormone-disrupting potency in effect-directed analysis

A sample preparation method combining solid-phase extraction (SPE) and liquid-liquid extraction (LLE) was developed to be used in Effect-Directed Analysis (EDA) of blood plasma. Until now such a method was not available. It can be used for extraction of a broad range of thyroid hormone (TH)-disruptors from plasma with high recoveries. Validation of the method using spiked cow plasma showed good recoveries for hydroxylated polybrominated diphenyl ethers (OH-PBDEs; 93.8 ± 19.5%), hydroxylated polychlorinated biphenyls (OH-PCBs; 93.8 ± 15.5%), other halogenated phenols (OHPs; 107 ± 8.1%), and for short-chain (<8 C-atoms) perfluoroalkyl substances (PFASs; 85.2 ± 24.6%). In the same extracts, the potency of the compound classes spiked to the cow plasma to competitively bind to transthyretin (TTR) was recovered by 84.9 ± 8.8%. Furthermore, the SPE-LLE method efficiently removed endogenous THs from the extracts, thereby eliminating their possible contribution to the binding assay response. The SPE-LLE method was applied to polar bear plasma samples to investigate its applicability in future EDA studies focusing on TH-disrupting compounds in this top predator species that is exposed to relatively high levels of bioaccumulating pollutants. A first screening revealed TTR-binding potency in the polar bear plasma extracts, which could be explained for 60-85% by the presence of OH-PCBs.