Simulation as an analytical tool continues to gain popularity in industry, government, and academics. For agricultural economists, the popularity is driven by an increased interest in risk management tools and decision aids on the part of farmers, agribusinesses, and policy makers. Much of the recent interest in risk analysis in agriculture comes from changes in the farm program that ushered in an era of increased uncertainty. With increased planting flexibility and an abundance of insurance and marketing alternatives farmers face the daunting task of sorting out many options in managing the increased risk they face. Like farmers, decision makers throughout the food and fiber industry are seeking ways to understand and manage the increasingly uncertain environment in which they operate. The unique abilities of simulation as a tool in evaluating and presenting risky alternatives together with an expected increase in commodity price risk, as projected by Ray, et al., will likely accelerate the interest in simulation for years to come.

Abstract.A correct description of fine (diameter <1 µm) and ultrafine (<0.1 µm) aerosol particles in urban areas is of interest for particle exposure assessment but also basic atmospheric research. We examined the spatio-temporal variability of atmospheric aerosol particles (size range 3-800 nm) using concurrent number size distribution measurements at a maximum of eight observation sites in and around Leipzig, a city in Central Europe. Two main experiments were conducted with different time span and number of observation sites (2 years at 3 sites; 1 month at 8 sites). A general observation was that the particle number size distribution varied in time and space in a complex fashion as a result of interaction between local and far-range sources, and the meteorological conditions. To identify statistically independent factors in the urban aerosol, different runs of principal component (PC) analysis were conducted encompassing aerosol, gas phase, and meteorological parameters from the multiple sites. Several of the resulting PCs, outstanding with respect to their temporal persistence and spatial coverage, could be associated with aerosol particle modes: a first accumulation mode ("droplet mode", 300-800 nm), considered to be the result of liquid phase processes and far-range transport; a second accumulation mode (centered around diameters 90-250 nm), considered to result from primary emissions as well as aging through condensation and coagulation; an Aitken mode (30-200 nm) linked to urban traffic emissions in addition to an urban and a rural Aitken mode; a nucleation mode (5-20 nm) linked to urban traffic emissions; nucleation modes Correspondence to: W. Birmili (birmili@tropos.de) (3-20 nm) linked to photochemically induced particle formation; an aged nucleation mode (10-50 nm). Additional PCs represented only local sources at a single site, or infrequent phenomena. In summary, the analysis of size distributions of high time and size resolution yielded a surprising wealth of statistical aerosol components occurring in the urban atmosphere over one single city. A paradigm on the behaviour of sub-µm urban aerosol particles is proposed, with recommendations how to efficiently monitor individual sub-fractions across an entire city.

The feasibility of integrating ethanol production into an existing sugar mill was analyzed by a stochastic spreadsheet model. As the price of corn continues to rise, ethanol producers will eventually need to look at other feedstock alternatives. Sugarcane has been proven to work well in the production of ethanol in Brazil. The results indicated existing U.S. sugar mills could economically switch to ethanol production. As imports into the United States threaten to undermine the U.S. sugar program, sugarcane producers have a viable alternative. At the very least, the alternative exists to diversify their income streams with ethanol production.

Abstract. A biennial dataset of ambient particle number size distributions (diameter range 4–800 nm) collected in urban air in Leipzig, Germany, was analysed with respect to the influence of traffic emissions. Size distributions were sampled continuously in 2005 and 2006 inside a street canyon trafficked by ca. 10 000 motor vehicles per day, and at a background reference site distant at 1.5 km. Auto-correlation analysis showed that the impact of fresh traffic emissions could be seen most intensely below particle sizes of 60 nm. The traffic-induced concentration increment at roadside was estimated by subtracting the urban background values from the street canyon measurement. To describe the variable dispersion conditions inside the street canyon, micro-meteorological dilution factors were calculated using the Operational Street Pollution Model (OSPM), driven by above-roof wind speed and wind direction observations. The roadside increment concentrations, dilution factor, and real-time traffic counts were used to calculate vehicle emission factors (aerosol source rates) that are representative of the prevailing driving conditions, i.e. stop-and-go traffic including episodes of fluent traffic flow at speeds up to 40 km h−1. The size spectrum of traffic-derived particles was essentially bimodal – with mode diameters around 12 and 100 nm, while statistical analysis suggested that the emitted number concentration varied with time of day, wind direction, particle size and fleet properties. Significantly, the particle number emissions depended on ambient temperature, ranging between 4.8 (±1.8) and 7.8 (±2.9).1014 p. veh−1 km−1 in summer and winter, respectively. A separation of vehicle types according to vehicle length suggested that lorry-like vehicles emit about 80 times more particle number than passenger car-like vehicles. Using nitrogen oxide (NOx) measurements, specific total particle number emissions of 338 p. (pg NOx)−1 were inferred. The calculated traffic emission factors, considering particle number and size, are anticipated to provide useful input for future air quality and particle exposure modelling in densely populated urban areas.