Effects of Nighttime Chemistry upon the Transport of Ozone and Ozone Precursors

It has been recognized for several years that ozone in rural areas can exceed the National Ambient Air Quality Standard (NAAQS) for photochemical oxidant whirh was 0.08 ppm for one hour, not to be exceeded more than once per year. During the summer of 1973, the NAAQS was exceeded from 15 to 37% of the time at four rural monitoring sites in Maryland, Pennsylvania, Ohio, and West Virginia.¹ This is a greater violation rate than is found in many urban areas. Dimitriades and Altshuller² have enumerated four possible sources for this rural ozone: (a) transport from urban areas, (b) local photochemical generation from urban ozone precursors, (c) local photochemical generation from precursors of rural origin which may be man-made or natural, and (d) injection of stratospheric ozone into the rural area. This paper considers the chemistry pertinent to the first two of these possible sources of rural ozone, namely the long distance (overnight) transport of ozone and ozone precursors.     

Use of Energy Scenarios in Addressing the CO2 Question

A reference scenario for CO₂ emissions was developed using a model of world energy supply and demand. In the reference scenario, world GNP and world energy demand increase at average rates of 2.1 percent per year and 1.5 percent per year, respectively during the period 1975-2100. The corresponding annual CO₂ emissions rise to a maximum of 16 gigatons of carbon around 2050 and then decline as a result of a transition to nonfossil fuel energy systems. A modified scenario for high CO₂ emissions was obtained by assuming an abundant supply of low cost coal, thus eliminating the transition. A low case was developed in which the low cost of alternative energy (i.e., solar, nuclear) induces an earlier shift away from fossil fuels.

Annual emissions of the three scenarios were used as input to a global carbon cycle model and the CO₂ buildup in the atmosphere during the period 1980-2100 was determined by the model. All three scenarios showed continuous rises in atmospheric CO₂ concentration. The reference scenario reached 775 ppm by 2100. The high CO₂ case resulted in concentrations of over 1040 ppm, and for the low case the 2100 concentration was just under 700 ppm. If the climate theory is correct, even 700 ppm is sufficient to give significant climate warming, but by experiencing the change gradually over a century, adaptation may not be painful. An early transition to nonfossil fuel supplies makes the problem less severe but does not eliminate it.     

KAPPA-G,A Non-Gaussian Plume Dispersion Model: Description and Evaluation Against Tracer Measurements

This paper presents a mixed methodology for the simulation of atmospheric disperson phenomena in which vertical diffusion is computed using an analytical solution of the K-theory equation, while horizontal diffusion is simulated by the Gaussian formula. This new formulation, while maintaining a simple analytical form for the concentration field, incorporates the effects of power-law vertical profiles of both wind speed and eddy diffusivity. The performance of this approach, which has been implemented into a full computer package (KAPPA-G), is evaluated by comparison with data from SF₆ tracer experiments.     

Temporal and geographical genetic variation in the amphipod Melita plumulosa (Crustacea: Melitidae): Link of a localized change in haplotype frequencies to a chemical spill

Anthropogenic effects such as contamination affect the genetic structure of populations. This study examined the temporal and geographical patterns of genetic diversity among populations of the benthic crustacean amphipod Melita plumulosa in the Parramatta River (Sydney, Australia), following an industrial chemical spill. The spill of an acrylate/methacrylate co-polymer in naphtha solvent occurred in July 2006. M. plumulosa were sampled temporally between December 2006 and November 2009 and spatially in November 2009. Genetic variation was examined at the mitochondrial cytochrome c oxidase subunit I locus. Notably, nucleotide diversity was low and Tajima’s D was significantly negative amongst amphipods collected immediately downstream from the spill for 10 months. We hypothesize that the spill had a significant localized effect on the genetic diversity of M. plumulosa. Alternate explanations include an alternate and unknown toxicant or a localized sampling bias. Future proposed studies will dissect these alternatives.     

Impact of different plants on the gas profile of a landfill cover

Methane is an important greenhouse gas emitted from landfill sites and old waste dumps. Biological methane oxidation in landfill covers can help to reduce methane emissions. To determine the influence of different plant covers on this oxidation in a compost layer, we conducted a lysimeter study. We compared the effect of four different plant covers (grass, alfalfa + grass, miscanthus and black poplar) and of bare soil on the concentration of methane, carbon dioxide and oxygen in lysimeters filled with compost. Plants were essential for a sustainable reduction in methane concentrations, whereas in bare soil, methane oxidation declined already after 6 weeks. Enhanced microbial activity - expected in lysimeters with plants that were exposed to landfill gas - was supported by the increased temperature of the gas in the substrate and the higher methane oxidation potential. At the end of the first experimental year and from mid-April of the second experimental year, the methane concentration was most strongly reduced in the lysimeters containing alfalfa + grass, followed by poplar, miscanthus and grass. The observed differences probably reflect the different root morphology of the investigated plants, which influences oxygen transport to deeper compost layers and regulates the water content.     

Vermicomposting of source-separated human faeces by Eisenia fetida: effect of stocking density on feed consumption rate, growth characteristics and vermicompost production

The main objective of the present study was to determine the optimum stocking density for feed consumption rate, biomass growth and reproduction of earthworm Eisenia fetida as well as determining and characterising vermicompost quantity and product, respectively, during vermicomposting of source-separated human faeces. For this, a number of experiments spanning up to 3 months were conducted using soil and vermicompost as support materials. Stocking density in the range of 0.25-5.00 kg/m² was employed in different tests. The results showed that 0.40-0.45 kg-feed/kg-worm/day was the maximum feed consumption rate by E. fetida in human faeces. The optimum stocking densities were 3.00 kg/m² for bioconversion of human faeces to vermicompost, and 0.50 kg/m² for earthworm biomass growth and reproduction.     

Effect of fresh green waste and green waste compost on mineral nitrogen, nitrous oxide and carbon dioxide from a Vertisol

Incorporation of organic waste amendments to a horticultural soil, prior to expected risk periods, could immobilise mineral N, ultimately reducing nitrogen (N) losses as nitrous oxide (N₂O) and leaching. Two organic waste amendments were selected, a fresh green waste (FGW) and green waste compost (GWC) as they had suitable biochemical attributes to initiate N immobilisation into the microbial biomass and organic N forms. These characteristics include a high C:N ratio (FGW 44:1, GWC 35:1), low total N (<1%), and high lignin content (>14%). Both products were applied at 3 t C/ha to a high N (plus N fertiliser) or low N (no fertiliser addition) Vertisol soil in PVC columns. Cumulative N₂O production over the 28 day incubation from the control soil was 1.5 mg/N₂O/m², and 11 mg/N₂O/m² from the control + N. The N₂O emission decreased with GWC addition (P < 0.05) for the high N soil, reducing cumulative N₂O emissions by 38% by the conclusion of the incubation. Analysis of mineral N concentrations at 7, 14 and 28 days identified that both FGW and GWC induced microbial immobilisation of N in the first 7 days of incubation regardless of whether the soil environment was initially high or low in N; with the FGW immobilising up to 30% of available N. It is likely that the reduced mineral N due to N immobilisation led to a reduced substrate for N₂O production during the first week of the trial, when soil N₂O emissions peaked. An additional finding was that FGW + N did not decrease cumulative N₂O emissions compared to the control + N, potentially due to the fact that it stimulated microbial respiration resulting in anaerobic micro sites in the soil and ultimately N₂O production via denitrification. Therefore, both materials could be used as post harvest amendments in horticulture to minimise N loss through nitrate-N leaching in the risk periods between crop rotations. The mature GWC has potential to reduce N₂O, an important greenhouse gas.