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Due to their mobility and toxicity, crude oil volatile organic compounds (VOCs) are representative components for oil pipeline contaminated sites detection. Therefore, contaminated location risk assessment, with airborne light detection and ranging (LIDAR) survey, in particular, requires ground-based determinative methods for oil VOCs, the interaction between oil VOCs and soil, and information on how they diffuse from underground into atmosphere. First, we developed a method for determination of crude oil VOC binary mixtures (take n-pentane and n-hexane as examples), taking synergistic effects of VOC mixtures on polydimethylsiloxane (PDMS) solid-phase microextraction (SPME) fibers into consideration. Using this method, we further aim to extract VOCs from small volumes, for example, from soil pores, using a custom-made sampling device for nondestructive SPME fiber intrusion, and to study VOC transport through heterogeneous porous media. Second, specific surface Brunauer–Emmett–Teller (BET) analysis was conducted and used for estimation of VOC isotherm parameters in soil. Finally, two models were fitted for VOC emission prediction, and the results were compared to the experimental emission results. It was found that free diffusion mode worked well, and an empirical correction factor seems to be needed for the other model to adapt to our condition for single and binary systems.
Background: The 3D printing is relevant as a manufacturing technology of functional models for forensic, pharmaceutical and bioanalytical applications such as drug delivery systems, sample preparation and point-of-care tests.
Objective: Melting behavior and autofluorescence of materials are decisive for optimal printing and applicability of the product which are influenced by varying unknown additives.
Methods: We have produced devices for bioanalytical applications from commercially available thermoplastic polymers using a melt-layer process. We characterized them by differential scanning calorimetry, fluorescence spectroscopy and functional assays (DNA capture assay, model for cell adhesion, bacterial adhesion and biofilm formation test).
Results: From 14 tested colored, transparent and black materials we found only deep black acrylonitrile-butadiene-styrene (ABS) and some black polylactic acid (PLA) useable for fluorescence-based assays, with low autofluorescence only in the short-wave range of 300-400 nm. PLA was suitable for standard bioanalytical purposes due to a glass transition temperature of approximately 60°C, resistance to common laboratory chemicals and easy print processing. For temperature-critical methods, such as hybridization reactions up to 90°C, ABS was better suited.
Conclusions: Autofluorescence was not a disadvantage per se but can also be used as a reference signal in assays. The rapid development of individual protocols for sample processing and analysis required the availability of a material with consistent quality over time. For fluorescence-based assays, the use of commercial standard materials did not seem to meet this requirement.
In hot and wet conditions in summer, the biological soil crusts (BSCs) decreased soil temperature by up to 11.8 °C, 7.5 °C, 5.4 °C, and 3.2 °C at surface, 5 cm, 15 cm, and 30 cm, respectively; while in cold and dry conditions in winter the BSCs increased soil temperature by up to 1.2 °C, 1.2 °C, and 1.1 °C at 5 cm, 15 cm, and 30 cm, respectively. The daily mean soil temperatures of the BSCs in a whole year were averagely increased by 0.57 ± 0.04 °C, 0.31 ± 0.04 °C, and 0.22 ± 0.04 °C at 5 cm, 15 cm, and 30 cm, respectively. The effects of the BSCs on soil temperature were positively correlated with air temperature and soil moisture, and decreased with soil depth from surface to deep soil. We concluded that BSCs relieved the extreme hot and cold soil micro-environments in desert ecosystem to some extent. Therefore their effects on soil temperature are positive for improving water and nutrient availability and biological community structure, thus decreasing susceptibility to desertification. These results would be helpful for understanding the ecological and hydrological functions of BSCs in semiarid environment.
The influence of biological soil crusts in natural ecosystems on structures and processes is well investigated. However, in South-Brandenburg (Germany), it is possible to study the development of biological soil crusts (BSC) during initial ecosystem genesis on two artificial water catchments with well-known ages and under differing starting conditions. The two experimental sites are located in the recultivation area of the lignite open-cast mining district of southern Brandenburg with a distance of approximately 1 km between them. Two different topographies were constructed at the experimental sites: the experimental plot at the catchment Neuer Lugteich was shaped like a dune, whereas the artificial water catchment Hühnerwasser was modelled as an inclined slope. The catchment Neuer Lugteich is four years older than Hühnerwasser. The original substrate at Neuer Lugteich is more sandy and carbonate-free compared to the original substrate dumped at Hühnerwasser. At both sites geomorphological differentiation and crust development were compared and the importance of substrate-dependent water availability and crust type clarified. Once settled, the crusts influenced the water regime of the soils by delaying infiltration through enhanced water repellency, and by limiting water infiltration. Chlorophyll analysis revealed that all crusts were at early stages of development. At Neuer Lugteich, the establishment of the biological soil crusts was closely associated with the vegetation succession, whereas no clear succession of the crusts could be observed at Hühnerwasser. The mosaic-like pattern of the biological soils crusts is associated with the distribution of fine-grained material here.zeige weniger