Sources,distribution, and acidity of sulfate–ammonium aerosol in the Arctic in winter–spring

We use GEOS-Chem chemical transport model simulations of sulfate–ammonium aerosol data from the NASA ARCTAS and NOAA ARCPAC aircraft campaigns in the North American Arctic in April 2008, together with longer-term data from surface sites, to better understand aerosol sources in the Arctic in winter–spring and the implications for aerosol acidity. Arctic pollution is dominated by transport from mid-latitudes, and we test the relevant ammonia and sulfur dioxide emission inventories in the model by comparison with wet deposition flux data over the source continents. We find that a complicated mix of natural and anthropogenic sources with different vertical signatures is responsible for sulfate concentrations in the Arctic. East Asian pollution influence is weak in winter but becomes important in spring through transport in the free troposphere. European influence is important at all altitudes but never dominant. West Asia (non-Arctic Russia and Kazakhstan) is the largest contributor to Arctic sulfate in surface air in winter, reflecting a southward extension of the Arctic front over that region. Ammonium in Arctic spring mostly originates from anthropogenic sources in East Asia and Europe, with added contribution from boreal fires, resulting in a more neutralized aerosol in the free troposphere than at the surface. The ARCTAS and ARCPAC data indicate a median aerosol neutralization fraction [NH₄⁺]/(2[SO₄^2?] + [NO₃^?]) of 0.5 mol mol^?1 below 2 km and 0.7 mol mol^?1 above. We find that East Asian and European aerosol transported to the Arctic is mostly neutralized, whereas West Asian and North American aerosol is highly acidic. Growth of sulfur emissions in West Asia may be responsible for the observed increase in aerosol acidity at Barrow over the past decade. As global sulfur emissions decline over the next decades, increasing aerosol neutralization in the Arctic is expected, potentially accelerating Arctic warming through indirect radiative forcing and feedbacks.     

Characterization of On-Road Vehicle NO Emissions by a TILDAS Remote Sensor

ABSTRACT

A tunable infrared laser differential absorption spectrometer (TILDAS) was used to remotely sense the nitric oxide (NO) emissions from 1,473 on-road vehicles. The real-world measurement precision of this instrument in the limit of low NO concentration is 5 ppm of the vehicle exhaust, which corresponds to a 3o detection limit of 15 ppm. Our analysis of the distribution of negative concentration measurements produced during this experiment supports this claim, showing that the instrumental noise for this set of measurements was at most 8 ppm in the limit of low NO concentration. The high sensitivity of this instrument allowed us to measure the NO emissions of even the cleanest vehicles. The measured vehicle fleet NO emissions closely fit a gamma distribution with 10% of the fleet contributing about 50% of the total fleet emissions. Newer vehicles had lower NO emissions than older ones, but high NO emitters were found in every vehicle age cohort. On a vehicle-by-vehicle basis, NO emissions correlated very weakly with vehicle velocity, acceleration, power per unit mass, carbon monoxide (CO) emissions, and hydrocarbon (HC) emissions. High NO emitting vehicles could not be identified by remote sensing of CO or HC emissions and vice versa. When we compared the NO emissions for 117 vehicles measured more than one time, about half of the high NO emitters were found to be very consistent, while the other half varied significantly.     

Exploring barriers to home gardening in Ohio households

Scholars have noted that race and ethnicity, socio-economic status (SES) as well as other socio-demographic factors may limit participation in local food systems based on the historic and structured patterns of inequalities that remain in communities promoting alternative agriculture and food (agrifood) activities. However, few empirical studies have examined the barriers which prevent people from participating in local food system activities. This paper uses survey data from the 2008 Ohio Survey of Food, Agriculture and Environmental Issues to consider whether barriers such as interest, time, financial resources, geography and space impact the participation of households in home gardening. Results from logistic regression show that SES, the availability of space and housing type are important factors which limit or enable household participation in home gardening. This paper contributes to our understanding of the barriers that prevent households from participating in home gardening, a form of food system localisation that, while a potentially powerful way to transform the agrifood system, has been underexamined in its own right.     

Estimating biodiversity impacts without field surveys: A case study in northern Borneo

In many regions of the world, biodiversity surveys are not routinely conducted prior to activities that lead to land conversion, such as development projects. Here we use top-down methods based on global range maps and bottom-up methods based on macroecological scaling laws to illuminate the otherwise hidden biodiversity impacts of three large hydroelectric dams in the state of Sarawak in northern Borneo. Our retrospective impact assessment finds that the three reservoirs inundate habitat for 331 species of birds (3 million individuals) and 164 species of mammals (110 million individuals). A minimum of 2100 species of trees (900 million individuals) and 17 700 species of arthropods (34 billion individuals) are estimated to be affected by the dams. No extinctions of bird, mammal, or tree species are expected due to habitat loss following reservoir inundation, while 4–7 arthropod species extinctions are predicted. These assessment methods are applicable to any data-limited system undergoing land-use change.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-015-0683-3) contains supplementary material, which is available to authorized users.     

Can California coastal managers plan for sea-level rise in a cost-effective way?

This paper examines five representative sites on the California coast to illustrate a cost-effective methodology using tools and data that local decision makers can apply to analyse the economics of sea level rise (SLR) adaptation. We estimate the costs/benefits of selected responses (e.g. no action, nourishment, seawalls) to future flooding and erosion risks exacerbated by SLR. We estimate the economic value of changes to public/private property, recreational and habitat value, and beach related spending/tax revenues. Our findings indicate that the costs of SLR are significant but uneven across communities, and there is no single best strategy for adaptation. For example, Los Angeles's Venice Beach could lose $450 million in tourism revenue by 2100 with a 1.4 m SLR scenario while San Francisco's Ocean Beach would lose $80 million, but the impacts to structures could total nearly $560 million at Ocean Beach compared to $50 million at Venice Beach.     

Greener governments: partisan ideologies,executive institutions,and environmental policies

Why do some governments have more environmentally friendly policies than others? Part of the answer involves governing parties’ ideological positions on environmentalism and the constraints imposed by executive institutions. Here, this party-based explanation is elaborated and tested with uniquely comparable indicators of national environmental policies for governments in 27 countries in the European Union (EU). The findings show that governments with parties that emphasized environmental protection in their manifestos are more likely to propose pro-environment policies during EU-level negotiations. However, the effect of ideology is mediated by the centralization of the national executive branch. In centralized national executives, the environmental positions of prime ministers’ parties affect policies, while in decentralized national executives, the positions of environment ministers’ parties are relevant. The findings have implications for understanding the impact of parties’ environmental positions on government policies, as well as for policy making in coalitions more generally.     

Suppression of nucleation mode particles by biomass burning in an urban environment: a case study

Measurements of concentrations and size distributions of particles 4.7 to 160 nm were taken using an SMPS during the bonfire and firework celebrations on Bonfire Night in Leeds, UK, 2006. These celebrations provided an opportunity to study size distributions in a unique atmospheric pollution situation during and following a significant emission event due to open biomass burning. A log-normal fitting program was used to determine the characteristics of the modal groups present within hourly averaged size distributions. Results from the modal fitting showed that on bonfire night the smallest nucleation mode, which was present before and after the bonfire event and on comparison weekends, was not detected within the size distribution. In addition, there was a significant shift in the modal diameters of the remaining modes during the peak of the pollution event. Using the concept of a coagulation sink, the atmospheric lifetimes of smaller particles were significantly reduced during the pollution event, and thus were used to explain the disappearance of the smallest nucleation mode as well as changes in particle count mean diameters. The significance for particle mixing state is discussed.     

Factors affecting heavy-duty diesel vehicle emissions

Societal and governmental pressures to reduce diesel exhaust emissions are reflected in the existing and projected future heavy-duty certification standards of these emissions. Various factors affect the amount of emissions produced by a heterogeneous charge diesel engine in any given situation, but these are poorly quantified in the existing literature. The parameters that most heavily affect the emissions from compression ignition engine-powered vehicles include vehicle class and weight, driving cycle, vehicle vocation, fuel type, engine exhaust aftertreatment, vehicle age, and the terrain traveled. In addition, engine control effects (such as injection timing strategies) on measured emissions can be significant. Knowing the effect of each aspect of engine and vehicle operation on the emissions from diesel engines is useful in determining methods for reducing these emissions and in assessing the need for improvement in inventory models. The effects of each of these aspects have been quantified in this paper to provide an estimate of the impact each one has on the emissions of diesel engines.