Characterization of biomass pyrolysis vapors with molecular beam, single photon ionization time-of-flight mass spectrometry

A single photon ionization, molecular beam sampling, reflectron time-of-flight mass spectrometer (SPI/MBTOFMS) has been developed and used to study pyrolysis products from a selection of biomass materials. Spectra are characterized by high resolution and decreased fragmentation compared to electron-impact ionization mass spectra from related molecular beam mass spectrometer systems equipped with quadrupole mass analyzers.     

Reactive transport modeling of processes controlling the distribution and natural attenuation of phenolic compounds in a deep sandstone aquifer

Reactive solute transport modeling was utilized to evaluate the potential for natural attenuation of a contaminant plume containing phenolic compounds at a chemical producer in the West Midlands, UK. The reactive transport simulations consider microbially mediated biodegradation of the phenolic compounds (phenols, cresols, and xylenols) by multiple electron acceptors. Inorganic reactions including hydrolysis, aqueous complexation, dissolution of primary minerals, formation of secondary mineral phases, and ion exchange are considered. One-dimensional (1D) and three-dimensional (3D) simulations were conducted. Mass balance calculations indicate that biodegradation in the saturated zone has degraded approximately 1-5% of the organic contaminant plume over a time period of 47 years. Simulations indicate that denitrification is the most significant degradation process, accounting for approximately 50% of the organic contaminant removal, followed by sulfate reduction and fermentation reactions, each contributing 15-20%. Aerobic respiration accounts for less than 10% of the observed contaminant removal in the saturated zone. Although concentrations of Fe(III) and Mn(IV) mineral phases are high in the aquifer sediment, reductive dissolution is limited, producing only 5% of the observed mass loss. Mass balance calculations suggest that no more than 20-25% of the observed total inorganic carbon (TIC) was generated from biodegradation reactions in the saturated zone. Simulations indicate that aerobic biodegradation in the unsaturated zone, before the contaminant entered the aquifer, may have produced the majority of the TIC observed in the plume. Because long-term degradation is limited to processes within the saturated zone, use of observed TIC concentrations to predict the future natural attenuation may overestimate contaminant degradation by a factor of 4-5.     

MTBE oxidation byproducts from the treatment of surface waters by ozonation and UV-ozonation

In recent years, there has been considerable concern over the release of methyl tert-butyl ether (MTBE), a gasoline additive, into the aquifers used as potable water sources. MTBE readily dissolves in water and has entered the environment via gasoline spills and leaking storage tanks. In this paper, we investigate ozonation and UV-ozonation for treatment of MTBE in contaminated drinking water sources. We report the test protocol and results of using solid-phase microextraction (SPME) to determine the level of MTBE and its oxidation byproducts in samples drawn from laboratory-scale ozone and UV-ozone reactors being evaluated at a US EPA research facility. Analysis of a prepared MTBE standard indicated a detection limit on the order of 0.1 microgl(-1) with a repeatability of +/-0.4%. Results show that the overall rate of removal of MTBE via UV-ozonation in a relatively turbid surface water (15 ntu) is twice that of ozonation alone. In addition, GC-MS analysis of decomposition products showed that tert-butyl formate (TBF), methyl acetate, butene, acetone, and acetaldehyde were produced by both processes. TBF and butene reach similar maximum yields from the two processes, but are more efficiently degraded by UV-ozonation treatment. This indicates that these treatment processes also degrade these byproducts. In contrast, the remaining byproducts (methyl acetate, acetone, and acetaldehyde) are formed at similar levels during treatment, but are not degraded once formed. These byproducts may be resistant to hydrogen abstraction by hydroxyl radical.     

Assessing the impact of ambient ozone on growth and productivity of two cultivars of wheat in India using three rates of application of ethylenediurea (EDU)

Three rates of ethylenediurea were used to assess the impact of ambient ozone on growth and productivity of wheat (Triticum aestivum L) cultivars "Malviya 533" (M 533) and "Malviya 234" (M 234) at a suburban site near Varanasi, India, beginning in December. Wheat plants were treated with EDU at 0, 150, 300 and 450 ppm as soil drenches at 10-day intervals. EDU treatment affected plant growth, with effects varying with cultivar, age, and EDU concentration. Seed yield was improved for M 533 at 150 ppm EDU, while yield improved for M 234 at 300 and 450 ppm EDU. M 533 appears to be more resistant to ozone than M 234. Overall results confirmed that EDU is very useful in assessing the effect of ambient ozone in India.     

Prediction of Pb speciation in concentrated and dilute nutrient solutions

Despite the presence of numerous studies in the literature examining the phytotoxicity of Pb, there is a lack of precise quantitative data on limiting concentrations of Pb for plant growth. Using the PhreeqcI chemical equilibrium model, simulations were conducted to examine the speciation of Pb in concentrated and dilute nutrient solutions. Due to the higher P concentration of Hoagland's solution (1000microM), precipitation of chloropyromorphite (Pb5(PO4)3Cl) was predicted to occur at lower pH values, and at lower Pb concentrations, than for a dilute nutrient solution (2microM P). Although nutrient solutions prepared in the glasshouse were supersaturated (and Pb concentrations were substantially higher than predicted by modeling), they confirmed the importance of the P concentration in influencing the precipitation of Pb. Given the low solubility of Pb-phosphates, nutrient solutions with low P concentrations should be utilized, and plant growth should be related to measured Pb concentrations rather than to the quantity of Pb initially added.     

Climatic sensitivity of temperate forests

Climatic change and associated global changes are of major interest to foresters, both in terms of forest ecology and of future forest production. Predicting the likely effects of global change on forests is extremely difficult due to the critical lack of information on regional changes in meteorological factors relevant to forests. However, existing models of forest production and forest distribution fail to take adequate account of what is already known. Climate and carbon dioxide concentrations have shown substantial changes over the last 100 years. Although the rate of change is likely to increase, recent proposed and implemented control strategies, together with better climatic models, are tending to suggest that the rate of change will be less than initially thought. This means that past changes may provide an increasingly useful source of information. In particular, information on the impact on forests of both long-term climate change and short-term climatic events is rapidly increasing. Such information should be built into future forest response models.     

The dynamics of dissolved nitrogen in a blanket peat dominated catchment

Precipitation, soil solution and drainage water were collected from a blanket peat catchment at Moor House National Nature Reserve in the Northern Pennine Uplands, UK, an area of moderately high N deposition. Two tributaries of the main stream were also sampled. Between 1993 and 1995 samples were analysed for NH4+ and NO3- and for part of the period for organic N. Inputs of N in precipitation exceeded outputs in stream water. Organic N represented a small proportion of N inputs while inputs of inorganic N averaged 10.2 kg ha(-1) a(-1). Soil solution from 10 cm depth in the peat was dominated by organic N whereas at 50 cm NH4+ slightly exceeded organic N. NO3- was rarely detected at either depth except during a period of exceptionally warm and dry weather in 1995. Output fluxes in stream water of organic N (5.7 to 6.5 kg ha(-1) a(-1)) were much greater than those of inorganic N (0.6 to 2.2 kg ha(-1) a(-1)). Inorganic N in streams was predominantly NO3- except in the smallest stream which had the largest concentrations of NH4+. This suggests that N transformations, particularly nitrification, may be taking place in the mineral soils adjacent to the streams or within the stream channel of the larger catchment.     

Estimation of atmospheric trace metal emissions in Vilnius City, Lithuania, using vertical concentration gradient and road tunnel measurement data

A new approach for the estimation of trace metal emissions in Vilnius city was implemented, using vertical concentration profiles in the urban boundary layer and road tunnel measurement data. Heavy metal concentrations were examined in fine and coarse particle fractions using a virtual impactor (cut-off size diameter 2.5 μm). Negative vertical concentration gradients were obtained for all metals (Ba, Pb, V, Sb, Zn) and both fractions. It was estimated that the vertical concentration gradient was formed due to emissions from an area of about 12 km². Road tunnel measurements indicated that trace metal concentrations on fine particles were lower than those on coarse particles, which suggested that re-emitted road dust was highly enriched in trace metal due to historic emissions within the tunnel. Emission rates of different pollutants in the road tunnel were calculated using pollutant concentration differences at the tunnel entrance and exit and traffic flow data. Heavy metal emission rates from the area of Vilnius city were estimated using the vertical gradient of heavy metal concentrations and the coefficient of turbulent mixing, as derived from meteorological measurement data. The emission values calculated by the two different methods coincided reasonably well, which indicated that the main source of airborne trace metals in Vilnius city is traffic. The potential of the vertical concentration gradient method for the direct estimation of urban heavy metal emissions was demonstrated.