Effect of fuel and lube oil sulfur on the performance of a diesel exhaust gas continuously regenerating trap.

The continuously regenerating trap (CRT) is a diesel exhaust emission control that removes nearly all diesel particulate matter on a mass basis, but under some circumstances oxidation of sulfur leads to the formation of nanoparticles. The objective of the four year study was to determine CRT performance under controlled, real-world, on-road conditions, and to develop quantitative relationships between fuel and lubrication oil sulfur concentration and particle number exhaust emissions. It was shown that nanoparticle emissions are minimized by the use of ultralow sulfur fuels and specially formulated low sulfur lubrication oil. Nanoparticle emissions increased with higher exhaust temperatures. Fuel and lubrication oil sulfur increased the particle concentration by, on average, 36 x 10(6) and 0.14 x 10(6) part/cm3 for each 1 ppm increase in sulfur. On the other hand there was a decrease in nanoparticle emissions by the CRT as the system aged.

An observational case study of ozone and precursors inflow to South East England during an anticyclone.

Summertime photochemical air pollution episodes within the United Kingdom have been proposed via modelling studies to be strongly influenced by regional scale inflow of air from the continental European boundary layer. We present a vertically resolved case study using measurements made from the NERC/Met Office BAe 146 research aircraft on 18th August 2005 over the South East of England and the North Sea during a weak anticyclone centred over Northern Europe. The vertical distribution of ozone, CO, NO(x), peroxyacetyl nitrate (PAN) and a wide range of both nonmethane hydrocarbons (NMHC) and oxygenated volatile organic compounds (OVOCs) were determined between 500 ft (approximately 152 m) and 7000 ft (approximately 2134 m) over the East Anglia coastline and 50 km inland. In excess of 80 ppbV ozone was observed within inflowing boundary layer air over the North Sea coast in a broad N-S sloping feature around 60 km wide. The inflowing feature of European origin was also observed further inland within the boundary layer albeit with lower, more variable, ozone mixing ratios. The increased variability in ozone over land was a product of titration by fresh surface emissions of NO via rapid upward transport in thermals, a hypothesis supported by the observed vertical wind speed component. Fast boundary layer mixing over land was further illustrated by a uniform distribution in reactive alkenes. A comparison between aircraft and surface O(3) UK AUN (Automatic Urban Network) measurements showed good agreement with the inland site, Sibton, but marked differences with the coastal monitoring site at Weybourne, potentially due to gradients established by ocean deposition in stably stratified marine air.

Local road traffic activity and the prevalence, severity, and persistence of wheeze in school children: combined cross sectional and longitudinal study.

OBJECTIVES: To investigate the relation between local road traffic activity and the occurrence, severity, and persistence of wheeze in children. METHODS: Data on wheeze and asthma were collected in a cross sectional questionnaire survey of 22,968 primary school children (age 4-11) and 27,826 secondary school children (age 11-16) in the Nottingham area. Direct measures of road traffic flow were made in the locality of each school and combined with Local Authority traffic data for major roads to estimate local traffic activity in vehicle metres/day/km2. Assessment of the effects of potential confounders was performed in nested case-control groups of 6576 primary and 5936 secondary children. Data on frequency of wheeze were collected for the cases to study disease severity. Longitudinal data on a historical cohort of 883 children who reported wheeze when aged 4-11 in 1988 were used to study the persistence of wheeze into adolescence. RESULTS: Unadjusted prevalence of wheeze in the past year within schools varied widely but was not associated with traffic activity in the school locality (weighted regression coefficient beta = -0.01, p = 0.93 for primary schools, beta = -0.18, p = 0.26 for secondary schools). The risk of wheeze in individual primary school children was not associated with traffic activity analysed as a continuous variable, although there was some suggestion of a weak, non-linear plateau effect. Similar effects were found for diagnosed asthma and recent cough. There was no evidence of any relation between traffic activity and risk of wheeze in secondary school children. There were positive but non-significant dose related effects of traffic activity on wheeze severity in primary and secondary children and on persistence of wheeze in the longitudinal cohort. CONCLUSIONS: Traffic activity in the school locality is not a major determinant of wheeze in children.