Seasonal distribution and modeling of diesel particulate matter in the Southeast US.

The fine and ultra fine size of diesel particulate mater (DPM) are of great health concern and significantly contribute to the overall cancer risk. In addition, diesel particles may contribute a warming effect on the planet's climate. The composition of these particles is composed principally of elemental carbon (EC) with adsorbed organic compounds, sulfate, nitrate, ammonia, metals, and other trace elements. The purpose of this study was to depict the seasonality and modeling of particulate matter in the Southeastern US produced by the diesel fueled sources (DFSs). The modeling results came from four one-month cases including March, June, September, and December to represent different seasons in 2003 by linking Models-3/CMAQ and SMOKE. The 1999 National Emissions Inventory Version 3 (NEI99) was used in this analysis for point, area, and non-road sources, whereas the National Mobile Inventory Model (NMIM) was used to create the on-road emissions. Three urban areas, Atlanta, Birmingham, and Nashville were selected to analyze the DPM emissions and concentrations. Even though the model performance was not very strong, it could be considered satisfactory to conduct seasonal distribution analysis for DPM. Important hourly DPM seasonality was observed in each city, of which higher values occurred at the morning traffic rush hours. The EC contributions of primary DPM were similar for all three sites (approximately 74%). The results showed that there is no significant daily seasonality of DPM contribution to PM(2.5) for any of these three cities in 2003. The annual DPM contribution to total PM(2.5) for Atlanta, Nashville, and Birmingham were 3.7%, 2.5%, and 2.2%, respectively.

Modeling and source apportionment of diesel particulate matter.

The fine and ultra fine sizes of diesel particulate matter (DPM) are of greatest health concern. The composition of these primary and secondary fine and ultra fine particles is principally elemental carbon (EC) with adsorbed organic compounds, sulfate, nitrate, ammonia, metals, and other trace elements. The purpose of this study was to use an advanced air quality modeling technique to predict and analyze the emissions and the primary and secondary aerosols concentrations that come from diesel-fueled sources (DFS). The National Emissions Inventory for 1999 and a severe southeast ozone episode that occurred between August and September 1999 were used as reference. Five urban areas and one rural area in the Southeastern US were selected to compare the main results. For urban emissions, results showed that DFS contributed (77.9%+/-8.0) of EC, (16.8%+/-8.2) of organic aerosols, (14.3%+/-6.2) of nitrate, and (8.3%+/-6.6) of sulfate during the selected episodes. For the rural site, these contributions were lower. The highest DFS contribution on EC emissions was allocated in Memphis, due mainly to diesel non-road sources (60.9%). For ambient concentrations, DFS contributed (69.5%+/-6.5) of EC and (10.8%+/-2.4) of primary anthropogenic organic aerosols, where the highest DFS contributions on EC were allocated in Nashville and Memphis on that episode. The DFS contributed (8.3%+/-1.2) of the total ambient PM(2.5) at the analyzed sites. The maximum primary DPM concentration occurred in Atlanta (1.44 microg/m(3)), which was 3.8 times higher than that from the rural site. Non-linearity issues were encountered and recommendations were made for further research. The results indicated significant geographic variability in the EC contribution from DFS, and the main DPM sources in the Southeastern U.S. were the non-road DFS. The results of this work will be helpful in addressing policy issues targeted at designing control strategies on DFS in the Southeastern U.S.

Determination of lysergide in urine by high-performance liquid chromatography combined with electrospray ionisation mass spectrometry.

A quantitative method which avoids derivatisation is described for the determination of lysergide (LSD) levels in urine. Sample preparation included addition of methysergide as an internal standard followed by solid-phase extraction. LSD was analysed on a system consisting of a C18 stationary phase and a mobile phase of 0.1 M acetate buffer pH 8.0-acetonitrile-triethylamine (75:25:0.25, v/v). LSD was detected by electrospray ionisation mass spectrometry with selected ion monitoring. The quantification limit was 0.5 ng/ml and the method was linear up to 10 ng/ml of LSD in urine.

Reduction of hexavalent uranium from organic complexes by sulfate- and iron-reducing bacteria.

The influence of organic-hexavalent-uranium [U(VI)] complexation on U(VI) reduction by a sulfate-reducing bacterium (Desulfovibrio desulfuricans) and an iron-reducing bacterium (Shewanella alga) was evaluated. Four aliphatic ligands (acetate, malonate, oxalate, and citrate) and an aromatic ligand (tiron [4,5-dihydroxy-1,3-benzene disulfonic acid]) were used to study complexed-uranium bioavailability. The trends in uranium reduction varied with the nature and the amount of U(VI)-organic complex formed and the type of bacteria present. D. desulfuricans rapidly reduced uranium from a monodentate aliphatic (acetate) complex. However, reduction from multidentate aliphatic complexes (malonate, oxalate, and citrate) was slower. A decrease in the amount of organic-U(VI) complex in solution significantly increased the rate of reduction. S. alga reduced uranium more rapidly from multidentate aliphatic complexes than from monodentate aliphatic complexes. The rate of reduction decreased with a decrease in the amount of multidentate complexes present. Uranium from an aromatic (tiron) complex was readily available for reduction by D. desulfuricans, while an insignificant level of U(VI) from the tiron complex was reduced by S. alga. These results indicate that selection of bacteria for rapid uranium reduction will depend on the organic composition of waste streams.

The analysis of lysergide (LSD): the development of novel enzyme immunoassay and immunoaffinity extraction procedures together with an HPLC-MS confirmation procedure.

A forensic procedure for the screening and confirmation of the presence of lysergide (lysergic acid diethylamide, LSD) in urine is described together with the evaluation of a novel enzyme immunoassay (EIA) and immunoaffinity extraction procedure. Following initial screening using either an established radioimmunoassay (RIA) or a novel EIA procedure, a quantitative estimate is established using a conventional high performance liquid chromatography-fluorescence (HPLC) technique following solid phase extraction. Final confirmation and quantitation, without derivatization, is established using HPLC in combination with electrospray ionization (ESI) mass spectrometry using methysergide as an internal standard. The detection limit of LSD in urine is 0.5 ng/mL. A blind trial confirmed the validity of the results. The choice of internal standard is discussed. Consideration is given to the photosensitivity of LSD solutions. A study of potential interferants in the HPLC-MS confirmation of LSD is presented and shows that for the wide range of compounds studied, there are none that would interfere with this confirmation technique. A comparison is shown between solid phase and immunoaffinity extraction/clean up procedures, and between RIA and EIA screening procedures.

Comparison of the short- and long-lasting effects of perforant path kindling on radial maze learning.

The present experiment compared the long-lasting with the short-lasting effects of kindling the perforant path input to the hippocampal formation on the acquisition of two radial maze tasks. Animals in the long-term group were fully kindled (i.e., Stage 5 motor seizures were evoked) prior to a stimulation-free training period. Animals in the short-term group were kindled 30-45 min prior to each learning trial. A third group of animals served as controls and were never kindled. On both 8-arm and 4/8-arm radical maze tasks, learning impairments were apparent only in the short-term group. Thus, the impaired learning is more likely related to the short-term aftereffects of an afterdischarge than to any long-term alterations in the neuronal status of the brain caused by kindling.

Effect of MK-801 on the induction and subsequent decay of long-term potentiation in the unanesthetized rabbit hippocampal dentate gyrus.

Several investigations have shown that the N-methyl-D-aspartate (NMDA) antagonist MK-801 interferes both with learning and a candidate neural mechanism for learning, the long-term potentiation (LTP) phenomenon. The low doses of MK-801 reported to block learning, however, may not be sufficient to block LTP. The present experiments examined the effects of 4 doses (0.05, 0.10, 0.50 and 1.00 mg/kg) of MK-801 on LTP of the perforant path-granule cell population excitatory postsynaptic potential (EPSP) and spike in unanesthetized rabbits. MK-801 did not significantly affect the threshold intensity for LTP of the population EPSP but the 3 highest doses did increase the threshold for LTP of the population spike. The 3 highest doses also reduced the peak magnitude and the duration of LTP of the spike to less than 24 h. The 0.05 m/kg dose did not affect the threshold or peak magnitude of spike LTP, but did decrease the decay time constant to 10.4 days, compared to 20.8 days in control rabbits. Only the 1.00 mg/kg dose reduced the magnitude of LTP of the EPSP. It was not possible to determine if MK-801 altered the longer-lasting component of LTP of the EPSP as it never persisted for longer than 24 h. These studies demonstrate that MK-801 disrupts LTP at doses also known to interfere with learning.

Development of a differential volume reactor system for soil biodegradation studies.

A bench scale experimental system was developed for the analysis of polycyclic aromatic hydrocarbon (PAH) degradation by mixed microbial cultures in PAH contaminated Manufactured Gas Plant (MGP) soils and on sand. The reactor system was chosen in order to provide a fundamental protocol capable for evaluating the performance of specific mixed microbial cultures on specific soil systems by elucidating the important system variables and their interactions. The reactor design and peripherals are described. A plug flow differential volume reactor (DVR) was used in order to remove performance effects related to reactor type, as opposed to system structure. This reactor system could be well represented mathematically. Methods were developed for on-line quantitative determination of PAH liquid phase concentrations. The mathematical models and experimental data are presented for the biodegradation of naphthalene on artificial and MGP soils.