Enhanced diesel emissions at low ambient temperature: hazardous materials in fine particles.

The emission of fine particles (PM2.5) from diesel trucks is enhanced by low ambient temperatures, which is a fact that has attracted considerable attention. Carbonaceous matter and polycyclic aromatic hydrocarbons (PAHs) are the dominant hazardous materials in PM2.5. These materials induce severe adverse effects on air quality and human health and contribute to climate change. The emissions from heavy- and light-duty diesel trucks were tested at an ambient temperature of - 20 to - 13 â„ƒ and 18-24 â„ƒ. This is the first study to quantify the enhanced carbonaceous matter and PAH emissions from diesel trucks at very low ambient temperatures based on an on-road emission test system. Features affecting diesel emissions, including driving speed, vehicle type, and engine certification level, were considered. The emissions of organic carbon, elemental carbon, and PAHs significantly increased from - 20 to - 13 â„ƒ. The empirical results revealed that intensive abatement of diesel emissions at low ambient temperatures could benefit human health and have a positive influence on climate change. Considering the widespread applications worldwide, an investigation into diesel emissions of carbonaceous matter and PAHs in fine particles at low ambient temperatures is urgently required.

Organic constituents on the surfaces of aerosol particles from Southern Finland, Amazonia, and California studied by vibrational sum frequency generation.

This article summarizes and compares the analysis of the surfaces of natural aerosol particles from three different forest environments by vibrational sum frequency generation. The experiments were carried out directly on filter and impactor substrates, without the need for sample preconcentration, manipulation, or destruction. We discuss the important first steps leading to secondary organic aerosol (SOA) particle nucleation and growth from terpene oxidation by showing that, as viewed by coherent vibrational spectroscopy, the chemical composition of the surface region of aerosol particles having sizes of 1 µm and lower appears to be close to size-invariant. We also discuss the concept of molecular chirality as a chemical marker that could be useful for quantifying how chemical constituents in the SOA gas phase and the SOA particle phase are related in time. Finally, we describe how the combination of multiple disciplines, such as aerosol science, advanced vibrational spectroscopy, meteorology, and chemistry can be highly informative when studying particles collected during atmospheric chemistry field campaigns, such as those carried out during HUMPPA-COPEC-2010, AMAZE-08, or BEARPEX-2009, and when they are compared to results from synthetic model systems such as particles from the Harvard Environmental Chamber (HEC). Discussions regarding the future of SOA chemical analysis approaches are given in the context of providing a path toward detailed spectroscopic assignments of SOA particle precursors and constituents and to fast-forward, in terms of mechanistic studies, through the SOA particle formation process.

Boty-like retrotransposons in the filamentous fungus Botrytis cinerea contain the additional antisense gene brtn.

Long-terminal repeat (LTR) retrotransposons typically contain gag, pol, or gag-pol, and in some case env genes. In this work, we used data mining of the Botrytis cinerea genomic sequence and a molecular approach to identify Boty-like LTR retrotransposons in B. cinerea containing an antisense gene (brtn) between pol and the 3'-LTR. Reverse transcriptase PCR (RT-PCR) revealed that some brtn-like genes could be expressed, at least in B. cinerea T4. We conducted BLAST comparisons and conserved-domain analysis, but the function of putative BRTN is presently unknown. Boty-like LTR retrotransposons in Sclerotinia sclerotiorum, called ScscLRET and containing brtn homologs at positions similar to brtn, were detected by homology searches and data mining of the S. sclerotiorum 1980 genomic sequence. Thus, this study demonstrated that some fungal LTR retrotransposons contain additional antisense genes.

Emissions of EC, OC, and PAHs from cottonseed oil biodiesel in a heavy-duty diesel engine.

Biodiesel fuels, made from renewable resources, have emerged as viable alternatives to conventional diesel fuel, but their impact on emissions is not fully understood. This study examines elemental carbon (EC), organic carbon (OC), and polycyclic aromatic hydrocarbons (PAHs) emissions from cottonseed oil biodiesel (CSO-B100). Relative to normal diesel fuel, CSO-B100 reduced EC emissions by 64% (±16%). The bulk of EC emitted from CSO-B100 was in the fine particle mode (<1.4 µm), which is similar to normal diesel. OC was found in all size ranges, whereas emissions of OC(1.4-2.5) were proportionately higher in OC(2.5) from CSO-B100 than from diesel. The CSO-B100 emission factors derived from this study are significantly lower, even without aftertreatment, than the China-4 emission standards established in Beijing and Euro-IV diesel engine standards. The toxic equivalency factors (TEFs) for CSO-B100 was half the TEFs of diesel, which suggests that PAHs emitted from CSO-B100 may be less toxic.