Ground‐based measurements of NOx and total reactive oxidized nitrogen (NOy) at Sable Island, Nova Scotia, during the NARE 1993 summer intensive

Measurements of NO, NO2, and total reactive oxidized nitrogen (NOy) were added to ongoing measurements of aerosols, CO, and O3 at Sable Island (43°55′N, 60°01′W), Nova Scotia, during the North Atlantic Regional Experiment (NARE) 1993 summer intensive. Ambient levels of NOx and NOy were found to be highly variable, and elevated levels can be attributed to the transport of polluted continental air or presumably to relatively fresh emissions from sources upwind (e.g., ship traffic). The median values for NOx and NOy are 98 and 266 parts per trillion by volume (pptv), respectively. A multiday pollution episode occurred during which elevated NOx and NOy were observed with enhanced levels of O3, CO, and condensation nuclei. Air masses of recent tropical marine origin characterized by low and constant levels of O3 and CO were sampled after Hurricane Emily. The correlation between ozone and CO is reasonably good, although the relation is driven by the single pollution episode observed during the study. The correlation of O3 with NOy and with NOy‐NOx is complicated by the presumed NOy removal processes in the marine boundary layer. Examination of the radiosonde data and comparisons of the surface data with those obtained on the overflying aircraft provide clear indications of vertical stratification above the site

Photochemical production and loss rates of ozone at Sable Island, Nova Scotia during the North Atlantic Regional Experiment (NARE) 1993 summer intensive

Three weeks of summertime surface‐based chemical and meteorological observations at Sable Island, Nova Scotia during the North Atlantic Regional Experiment (NARE) 1993 summer intensive are used to study instantaneous photochemical production and loss rates of ozone by means of a numerical photochemical model. Results are most sensitive to the averaging scheme of data used to constrain the model and the ambient variability of the measurements. Model simulations driven by a time series of 5 min averaged data, most representative of the chemistry at the site, yield an average net photochemical ozone production of 3.6 ppbv/d. Estimates of net ozone production designed to filter out local sources, by using 1000–1400 LT median values of observations to drive the model and by excluding short‐lived hydrocarbons, give values ranging from 1 to 4 ppbv/d. These positive values of net ozone production within the marine boundary layer over Sable Island demonstrate the impact of polluted continental plumes on the background photochemistry of the region during the intensive. The dominant ambient variables controlling photochemical production and loss rates of ozone at the site during the measurement campaign appear to be levels of nitrogen oxides, ozone, nonmethane hydrocarbons, and solar intensity determined by cloud cover. The model partitioning of nitrogen oxides agrees for the most part with measurements, lending credence to calculated photochemical production and loss rates of ozone as well as inferred levels of peroxy radicals not measured at the site. Discrepancies, however, often occur during episodes of intermittent cloud cover, fog, and rain, suggesting the influence of cloud processes on air masses reaching the site

Survival-extinction phase transition in a bit-string population with mutation

A bit-string model for the evolution of a population of haploid organisms, subject to competition, reproduction with mutation and selection is studied, using mean field theory and Monte Carlo simulations. We show that, depending on environmental flexibility and genetic variability, the model exhibits a phase transtion between extinction and survival. The mean-field theory describes the infinite-size limit, while simulations are used to study quasi-stationary properties.Comment: 11 pages, 5 figure

Determination of urban volatile organic compound emission ratios and comparison with an emissions database

During the NEAQS-ITCT2k4 campaign in New England, anthropogenic VOCs and CO were measured downwind from New York City and Boston. The emission ratios of VOCs relative to CO and acetylene were calculated using a method in which the ratio of a VOC with acetylene is plotted versus the photochemical age. The intercept at the photochemical age of zero gives the emission ratio. The so determined emission ratios were compared to other measurement sets, including data from the same location in 2002, canister samples collected inside New York City and Boston, aircraft measurements from Los Angeles in 2002, and the average urban composition of 39 U.S. cities. All the measurements generally agree within a factor of two. The measured emission ratios also agree for most compounds within a factor of two with vehicle exhaust data indicating that a major source of VOCs in urban areas is automobiles. A comparison with an anthropogenic emission database shows less agreement. Especially large discrepancies were found for the C2-C4 alkanes and most oxygenated species. As an example, the database overestimated toluene by almost a factor of three, which caused an air quality forecast model (WRF-CHEM) using this database to overpredict the toluene mixing ratio by a factor of 2.5 as well. On the other hand, the overall reactivity of the measured species and the reactivity of the same compounds in the emission database were found to agree within 30%. Copyright 2007 by the American Geophysical Union

Nighttime removal of NOx in the summer marine boundary layer

The nitrate radical, NO3, and dinitrogen pentoxide, N2O5, are two important components of nitrogen oxides that occur predominantly at night in the lower troposphere. Because a large fraction of NO2 reacts to form NO3 and N2O5 during the course of a night, their fate is an important determining factor to the overall fate of NOx (=NO and NO2). As a comprehensive test of nocturnal nitrogen oxide chemistry, concentrations of O3, NO, NO2, NO3, N2O5, HNO3 and a host of other relevant compounds, aerosol abundance and composition, and meteorological conditions were measured in the marine boundary layer from the NOAA research vessel Ronald H. Brown off the East Coast of the United States as part of the New England Air Quality Study (NEAQS) during the summer of 2002. The results confirm the prominent role of NO3 and N2O5 in converting NOx to HNO3 at night with an efficiency on par with daytime photochemical conversion. The findings demonstrate the large role of nighttime chemistry in determining the NOx budget and consequent production of ozone. INDEX TERMS: 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry. Citation: Brown, S. S., et al. (2004), Nighttime removal of NOx in the summer marine boundary layer, Geophys. Res. Lett., 31, L07108, doi:10.1029/2004GL01941

Americans on International Trade Policy

A policymaking simulation is an online process that puts citizens in the shoes of elected officials by simulating the process they go through in making policy decisions. Each simulation introduces a broader policy topic and then presents a series of modules that address a specific policy option that is currently under consideration in the current discourse. For each module, respondents: 1) receive a short briefing on a policy issue and the option or options for addressing it; 2) evaluate arguments for and against the policy options; and 3) finally, make their recommendation for what their elected officials should do.Promoting the Growth of Trade Through an International Rules-Based System: Respondents were introduced to the international system for promoting international trade—two-thirds said they were familiar with it. Evaluating arguments for and against continuing to seek to further the growth of international trade through international agreements, in most cases large majorities from both parties found both pro and con arguments convincing, with Democrats responding more to the pro arguments and Republicans responding more to the con arguments. Nonetheless, in the end an overwhelming bipartisan majority approved of United States, together with other countries, promoting international trade through a set of agreed-on rules that seek to lower barriers to trade and to ensure trade is done fairly. The World Trade Organization: A very large majority approved of the US continuing to be part of the World Trade Organization, though for Republicans this was only a modest majority, while Democrats approved overwhelmingly. MITIGATING THE NEGATIVE EFFECTS OF TRADE: Increasing Unemployment Benefits: As a means of addressing some of the negative effects of trade, a bipartisan majority favored increasing unemployment benefits, with a majority favoring increasing the amount from 39% to 50% of previous earnings. However, a bipartisan majority did not support increasing the maximum period of unemployment benefits beyond the current average of 26 weeks. Worker Retraining and Education: Presented several proposals for job training and education under consideration in Congress, very large bipartisan majorities favored proposals to increase spending on training for jobs in cybersecurity and the energy industry, and a proposal to provide employers a tax credit for apprenticeship programs. Trade Adjustment Assistance: A majority of six in ten favored expanding the Trade Adjustment Assistance program to more people who get laid off from their job directly because of an increase in trade, however six in ten Republicans were opposed. Just four in ten, but a modest majority of Democrats, favored extending such assistance to all people who get laid off from their job. Labor and Environment Standards in Trade Agreements: Overwhelming bipartisan majorities favored including in new international trade agreements the requirement that countries abide by both the labor and environmental standards they have committed to, that they do not lower their standards to attract business or to get a competitive edge, and that there is an effective system for enforcing these requirements. Impact of Mitigating Negative Effects on Attitudes About Trade: Respondents who disapproved of promoting greater trade through international agreements, while also favoring steps to mitigate the negative effects, were asked how they would feel about the promoting trade if the mitigating steps they favored were adopted. About half said that they would then favor promoting greater trade through international agreements. THE USE OF TARIFFS: Steel Tariffs: Voters divided sharply along party lines on the US administration invoking the national security exemption and imposing tariffs of 25% on steel imports and 10% on aluminum imports, with a large majority of Republicans approving and a large majority of Democrats disapproving. Overall, a very slight majority approved. Tariffs on China: Voters divided along party lines on whether the US should have imposed tariffs on China without first getting a WTO ruling. Going forward, a modest majority opposed imposing additional tariffs on China to get them to change their trade practices, but instead favored working through the WTO to get a ruling against China. Views on both issues are highly polarized along partisan lines with large majorities of Democrats favoring working through the WTO and large majorities of Republicans favoring imposing tariffs. North American Trade: NAFTA and the USMCA: Asked about the original North American Free Trade Agreement (NAFTA) agreement, a very large majority, including a majority of Republicans, expressed approval. Told about the proposed U.S.-Mexico-Canada Agreement (USMCA) agreement, a slight majority favored it, with large majority of Republicans in support and a modest majority of Democrats opposed. If Congress does not approve the USMCA deal, a large majority favors staying in NAFTA. Those who favored the new USMCA agreement and approved the steel and aluminum tariffs were asked whether they would be willing to lift the new steel and aluminum tariffs on imports from Canada and Mexico if it appears necessary to get an agreement on USMCA; most said they would

Organic aerosol formation downwind from the Deepwater Horizon oil spill.

A large fraction of atmospheric aerosols are derived from organic compounds with various volatilities. A National Oceanic and Atmospheric Administration (NOAA) WP-3D research aircraft made airborne measurements of the gaseous and aerosol composition of air over the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico that occurred from April to August 2010. A narrow plume of hydrocarbons was observed downwind of DWH that is attributed to the evaporation of fresh oil on the sea surface. A much wider plume with high concentrations of organic aerosol (>25 micrograms per cubic meter) was attributed to the formation of secondary organic aerosol (SOA) from unmeasured, less volatile hydrocarbons that were emitted from a wider area around DWH. These observations provide direct and compelling evidence for the importance of formation of SOA from less volatile hydrocarbons

Chemical composition observed over the mid-Atlantic and the detection of pollution signatures far from source regions

The atmospheric composition of the central North Atlantic region has been sampled using the FAAM BAe146 instrumented aircraft during the Intercontinental Transport of Ozone and Precursors (ITOP) campaign, part of the wider International Consortium for Atmospheric Research on Transport and Transformation (ICARTT). This paper presents an overview of the ITOP campaign. Between late July and early August 2004, twelve flights comprising 72 hours of measurement were made in a region from approximately 20 to 40°W and 33 to 47°N centered on Faial Island, Azores, ranging in altitude from 50 to 9000 m. The vertical profiles of O3 and CO are consistent with previous observations made in this region during 1997 and our knowledge of the seasonal cycles within the region. A cluster analysis technique is used to partition the data set into air mass types with distinct chemical signatures. Six clusters provide a suitable balance between cluster generality and specificity. The clusters are labeled as biomass burning, low level outflow, upper level outflow, moist lower troposphere, marine and upper troposphere. During this summer, boreal forest fire emissions from Alaska and northern Canada were found to provide a major perturbation of tropospheric composition in CO, PAN, organic compounds and aerosol. Anthropogenic influenced air from the continental boundary layer of the USA was clearly observed running above the marine boundary layer right across the mid-Atlantic, retaining high pollution levels in VOCs and sulfate aerosol. Upper level outflow events were found to have far lower sulfate aerosol, resulting from washout on ascent, but much higher PAN associated with the colder temperatures. Lagrangian links with flights of other aircraft over the USA and Europe show that such signatures are maintained many days downwind of emission regions. Some other features of the data set are highlighted, including the strong perturbations to many VOCs and OVOCs in this remote region