In 2011, the European Commission introduced a limit for nonvolatile particle number (PN) emissions >23 nm from light-duty (LD) vehicles and the stated intent is to implement similar legislation for on-road heavy-duty (HD) engines at the next legislative stage. This paper reviews the recent literature regarding the operation-dependent emission of PN from LD vehicles and HD engines, and the measurement procedure used for regulatory purposes. The repeatability of the PN method is of the order of 5% and higher scatter of the results can easily be explained by the effect of the vehicles or the aftertreatment devices on the PN emissions (e.g., the fill state of the diesel particulate filters). Reproducibility remains an issue since it may exceed 30%. These high-variability levels are mainly associated with calibration uncertainties of the PN instruments. Correlation measurements between the full-flow dilution tunnels (constant-volume samplers, CVS) and the proportional partial-flow dilution systems (PFDS) showed agreement within 15% for the PN method down to 1 × 10 11 p/kWh. At lower concentrations, the PN background of the CVS and/or the PFDS can result in larger inconsistencies. The filter-based particulate matter (PM) mass and the PN emissions correlate well down to 1-2 mg/km for LD vehicles and to 2-3 mg/kWh for HD applications. The correlation improves when only elemental carbon mass is considered: it is relatively good down to 0.1-0.3 mg/km or mg/kWh. ACRONYMS AND ABBREVIATIONS ACEA Association des Constructeurs Européens d'Auto mobiles (European Automobile Manufacturers' Association) AM Accumulation mode APC AVL particle counter

Reducing ambient concentrations of nitrogen dioxide (NO2) remains a key challenge across many European urban areas, particularly close to roads. This challenge mostly relates to the lack of reduction in emissions of oxides of nitrogen (NOx) from diesel road vehicles relative to the reductions expected through increasingly stringent vehicle emissions legislation. However, a key component of near-road concentrations of NO2 derives from directly emitted (primary) NO2 from diesel vehicles. It is well-established that the proportion of NO2 (i.e. the NO2/NOx ratio) in vehicle exhaust has increased over the past decade as a result of vehicle after-treatment technologies that oxidise carbon monoxide and hydrocarbons and generate NO2 to aid the emissions control of diesel particulate. In this work we bring together an analysis of ambient NOx and NO2 measurements with comprehensive vehicle emission remote sensing data obtained in London to better understand recent trends in the NO2/NOx ratio from road vehicles. We show that there is evidence that NO2 concentrations have decreased since around 2010 despite less evidence of a reduction in total NOx. The decrease is shown to be driven by relatively large reductions in the amount of NO2 directly emitted by vehicles; from around 25 vol% in 2010 to 15 vol% in 2014 in inner London, for example. The analysis of NOx and NO2 vehicle emission remote sensing data shows that these reductions have been mostly driven by reduced NO2/NOx emission ratios from heavy duty vehicles and buses rather than light duty vehicles. However, there is also evidence from the analysis of Euro 4 and 5 diesel passenger cars that as vehicles age the NO2/NOx ratio decreases. For example the NO2/NOx ratio decreased from 29.5 ± 2.0% in Euro 5 diesel cars up to one year old to 22.7 ± 2.5% for four-year old vehicles. At some roadside locations the reductions in primary NO2 have had a large effect on reducing both the annual mean and number of hourly exceedances of the European Limit Values of NO2.

Loss of natural forests by forest clearcutting has been identified as a critical conservation challenge worldwide. This study addressed forest fragmentation and loss in the context of the establishment of a functional green infrastructure as a spatiotemporally connected landscape-scale network of habitats enhancing biodiversity, favorable conservation status, and ecosystem services. Through retrospective analysis of satellite images, we assessed a 50- to 60-year spatiotemporal clearcutting impact trajectory on natural and near-natural boreal forests across a sizable and representative region from the Gulf of Bothnia to the Scandinavian Mountain Range in northern Fennoscandia. This period broadly covers the whole forest clearcutting period; thus, our approach and results can be applied to comprehensive impact assessment of industrial forest management. The entire study region covers close to 46,000 km of forest-dominated landscape in a late phase of transition from a natural or near-natural to a land-use modified state. We found a substantial loss of intact forest, in particular of large, contiguous areas, a spatial polarization of remaining forest on regional scale where the inland has been more severely affected than the mountain and coastal zones, and a pronounced impact on interior forest core areas. Salient results were a decrease in area of the largest intact forest patch from 225,853 to 68,714 ha in the mountain zone and from 257,715 to 38,668 ha in the foothills zone, a decrease from 75% to 38% intact forest in the inland zones, a decrease in largest patch core area (assessed by considering 100-m patch edge disturbance) from 6114 to 351 ha in the coastal zone, and a geographic imbalance in protected forest with an evident predominance in the mountain zone. These results demonstrate profound disturbance of configuration of the natural forest landscape and disrupted connectivity, which challenges the establishment of functional green infrastructure. Our approach supports the identification of forests for expanded protection and conservation-oriented forest landscape restoration.

A Euro 4 Light-Duty Diesel vehicle equipped with a diesel particulate filter (DPF) was circulated to 9 labs where repetitions of the current regulatory New European Drive Cycle (NEDC) were conducted. Regulated gaseous and improved (with cyclone, filter temperature 47 ± 5• C, constant filter face velocity, high precision balance at all labs) particulate mass (PM) measurements were also conducted. A reference particle number (PN) measurement system measuring non-volatile particles was circulated along with the test vehicle. Labs also tested their own PN systems built to comply with the reference system's performance specifications. The mean PN emissions level of the vehicle was below 1 × 10 11 particles/km. The intra-lab variability (repeatability) was ∼40% and the inter-lab variation was ∼25%. The study showed that the new PN method had similar variability to other gaseous pollutants such as carbon monoxide and hydrocarbons and better than the PM (intra-lab variability ∼55% and inter-lab ∼35%). Even with the improved PM method the emissions of the vehicle were similar to the background level (∼0.4 mg/km) and the method was subject to volatile artifact. The PN method showed greater sensitivity than the PM method as it could distinguish the DPF fill state or different preconditioning states of the vehicle. However, the PN emission level of the vehicle estimated by the reference system were on average 15% higher than any given lab's own system, indicating that the procedures and calibration designed for the standardization of performance should be precisely defined and followed. This work has been conducted in the framework of the PMP project (run under the auspices of the UNECE-GRPE). The authors would like to thank all the laboratories and companies that participated. In addition, Matter Engineering AG for providing the dilution system of the reference system, TSI Incorporated for providing the particle number counter of the reference system, and Dekati Ltd and Horiba for providing particle number systems at the labs that did not have their own. AECC receive thanks for providing the reference vehicle, Concawe for providing the fuel and the lubricant for the reference vehicle and AEA Technology Environment for the calibrations of the reference system. The authors would also like to thank Dr. Nikolaos Stilianakis for his insights on the statistical issues.Address correspondence to Jon Andersson, Ricardo UK, Chemistry Department, Shoreham Technical Centre, BN43 5FG, Shoreham-bySea, U.K. E-mail: Jon.Andersson@ricardo.com INTRODUCTIONThe established method to measure particle emissions for type approval tests is gravimetric analysis of filter samples, taken from a full exhaust flow dilution tunnel. However, for low-emission vehicles, which are already present in the market, concerns have been raised about the suitability of the method. For example Chase et al. (2004) showed that a major part of the collected mass consists of volatiles (volatile artifact). Tests at various laboratories have shown high variability for th...

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Euro 6, the next stage of European emissions regulations for light-duty vehicles, becomes mandatory from 1 September 2014 for the Type Approval of new passenger cars and the smaller light commercial vehicles (categories M and N1 Class 1), and 1 year later for all other commercial vehicles not exceeding 3.5 tonnes maximum mass (categories N1 Class II and N1 Class III). One year after these dates, Euro 6 becomes mandatory for all new registrations. A number of papers and reports have raised concerns over the emissions performance-especially diesel NOx emissions-of current and future light duty-vehicles in real, and in particular

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The particle measurement programme (PMP) used a particle measurement system (reference system (RS)) to quantify the particle number emissions of several vehicles. The RS was circulated around several laboratories to represent an internal standard. During the exercise dilution factors, losses and volatile removal efficiencies of the RS were regularly checked. In parallel with the RS, some labs employed their own particle measurement systems (lab systems (LS)) to determine the emissions of the same test vehicles. Comparisons between results from the RS and the LS showed that several different instruments were capable of measuring particle number emissions to within ±15% across an emission range of four orders of magnitude. Real-time emission patterns also correlated well in most cases. However, larger differences were observed when dilution factors and losses were not accurately determined and subjected to correction. Equivalence between measurement systems can be achieved once calibration and validation procedures are standardized for both manufacturers and users.