Seasonal and Spatial Patterns of Mercury Wet Deposition in the United States: Constraints on the Contribution from North American Anthropogenic Sources

Observed wet deposition fluxes of mercury in the United States show a maximum in the Southeast, and a consistent seasonal variation (maximum in summer, minimum in winter) that increases in amplitude from north to south. We simulate these patterns successfully with a global 3-D chemical transport model (GEOS-Chem) including our best estimates of sources and processes. We attribute the high wet deposition over the Southeast in summer to scavenging of upper-altitude Hg(II) by deep convection. Seasonal variation at higher latitudes is attributed to a combination of enhanced summertime oxidation of Hg(0) and inefficient scavenging of Hg(II) by snow. Scavenging of Hg(II) from above the boundary layer contributes over half of wet deposition to the US in the model. Even within the boundary layer, we find that most of Hg(II) originates from the global mercury pool. Wet deposition in the model accounts for only 30% of total mercury deposition in the US, the remainder being from dry deposition, including 42% from Hg(0) uptake. North American anthropogenic emissions contribute 20% of total mercury deposition in the US (up to 50% in the industrial Midwest and Northeast).Earth and Planetary SciencesEngineering and Applied Science

Genetically Induced Cholinergic Hyper-Innervation Enhances Taste Learning

Acute inhibition of acetylcholine (ACh) has been shown to impair many forms of simple learning, and notably conditioned taste aversion (CTA). The most adhered-to theory that has emerged as a result of this work – that ACh increases a taste’s perceived novelty, and thereby its associability – would be further strengthened by evidence showing that enhanced cholinergic function improves learning above normal levels. Experimental testing of this corollary hypothesis has been limited, however, by side-effects of pharmacological ACh agonism and by the absence of a model that achieves long-term increases in cholinergic signaling. Here, we present this further test of the ACh hypothesis, making use of mice lacking the p75 pan-neurotrophin receptor gene, which show a resultant over-abundance of cholinergic neurons in sub-regions of the basal forebrain (BF). We first demonstrate that the p75−/− abnormality directly affects portions of the CTA circuit, locating mouse gustatory cortex (GC) using a functional assay and then using immunohistochemisty to demonstrate cholinergic hyper-innervation of GC in the mutant mice – hyper-innervation that is unaccompanied by changes in cell numbers or compensatory changes in muscarinic receptor densities. We then demonstrate that both p75−/− and wild-type (WT) mice learn robust CTAs, which extinguish more slowly in the mutants. Further testing to distinguish effects on learning from alterations in memory retention demonstrate that p75−/− mice do in fact learn stronger CTAs than WT mice. These data provide novel evidence for the hypothesis linking ACh and taste learning

Origins of Neural Progenitor Cell-Derived Axons Projecting Caudally after Spinal Cord Injury.

Neural progenitor cells (NPCs) transplanted into sites of spinal cord injury (SCI) extend large numbers of axons into the caudal host spinal cord. We determined the precise locations of neurons in the graft that extend axons into the caudal host spinal cord using AAV9-Cre-initiated retrograde tracing into floxed-TdTomato-expressing NPC grafts. 7,640 ± 630 grafted neurons extended axons to a single caudal host spinal cord site located 2 mm beyond the lesion, 5 weeks post injury. While caudally projecting axons arose from neurons located in all regions of the graft, the majority of caudally projecting graft neurons (53%) were located within the caudal one-third of the graft. Numerous host corticospinal axons formed monosynaptic projections onto caudally projecting graft neurons; however, we find that the majority of host axonal neuronal projections formed by neural progenitor cell interneuronal "relays" across sites of SCI are likely polysynaptic in nature

Social Barriers to Implementing Continuous Improvement Initiatives

Organizations report challenges in implementing continuous improvement or operational excellence initiatives as they strive for sustainability, yet few have considered the impact that social barriers have in creating resistance to implementation. Through a qualitative grounded theory method, this study highlights several contributions. First, social barriers are stronger than other challenges to implementing operational excellence. Second, these barriers include interpersonal (e.g., communication challenges, unwillingness to change, and workplace relationships) and organizational (e.g., employee treatment, cultural values, and formal organizational characteristics) issues. This article thus links sustainability to operational excellence and suggests that the greatest barriers to becoming more sustainable are likely social in nature. The study then concludes, in addition to these contributions, with a consideration of limitations and directions for future research

EU Peatlands: Current Carbon Stocks and Trace Gas Fluxes

Peatlands in Europe has formed a significant sink for atmospheric CO2 since the last glacial maximum. Currently they are estimated to hold ca. 42 Gt carbon in the form of peat and are therefore a considerable component in the European carbon budget. Due to the generally wet soil conditions in peatlands they are also significant emitters of the strong greenhouse gas (GHG) methane (CH4) and in some cases also of nitrous oxide (N2O). The EU funded CarboEurope-GHG Concerted Action attempts to develop a reliable and complete greenhouse gas budget for Europe and this report aims to provide a review and synthesis of the available information about GHG exchanges in European peatlands and their underlying processes. A best estimate for all the European countries shows that some are currently sinks for atmospheric CO2 while others are sources. In contrast, for CH4 and N2O, only the sources are relevant. Whilst some countries are CO2 sinks, all countries are net GHG emitters from peatlands. The results presented, however, carry large uncertainties, which cannot be adequately quantified yet. One outstanding uncertainty is the distribution of land use types, particular in Russia, the largest European peat nation. The synthesis of GHG exchange, nevertheless, indicates some interesting features. Russia hosts an estimated 41% of European peatlands and contributes most to all GHG exchanges (CO2: 25%, CH4: 52%, N2O: 26%, Total: 37%). Germany is the second-largest emitter (12% of European total) although it contains only 3.2% of European peatlands. The reason is the use of most of the peatland area for intensive cropland and grassland. The largest CO2 emitters are countries with large agricultural peatland areas (Russia, Germany, Belarus, Poland), the largest N2O emitters are those with large agricultural fen areas (Russia, Germany, Finland). In contrast, the largest CH4 emitters are concentrated in regions with large areas of intact mires, namely Russia and Scandinavia. High average emission densities above 3.5 t C-equiv. ha-1 are found in the Southeast Mediterranean, Germany and the Netherlands where agricultural use of peatlands is intense. Low average emission densities below 0.3 t C-equiv. ha-1 occur where mires and peatland forests dominate, e.g. Finland and the UK. This report concludes by pointing at key gaps in our knowledge about peatland carbon stocks and GHG exchanges which include insufficient basic information on areal distribution of peatlands, measurements of peat depth and also a lack of flux datasets providing full annual budgets of GHG exchanges

Global Health and Economic Impacts of Future Ozone Pollution

Abstract and PDF report are also available on the MIT Joint Program on the Science and Policy of Global Change website (http://globalchange.mit.edu/).We assess the human health and economic impacts of projected 2000-2050 changes in ozone pollution using the MIT Emissions Prediction and Policy Analysis-Health Effects (EPPA-HE) model, in combination with results from the GEOS-Chem global tropospheric chemistry model that simulated climate and chemistry effects of IPCC SRES emissions. We use EPPA to assess the human health damages (including acute mortality and morbidity outcomes) caused by ozone pollution and quantify their economic impacts in sixteen world regions. We compare the costs of ozone pollution under scenarios with 2000 and 2050 ozone precursor and greenhouse gas emissions (SRES A1B scenario). We estimate that health costs due to global ozone pollution above pre-industrial levels by 2050 will be $580 billion (year 2000$) and that acute mortalities will exceed 2 million. We find that previous methodologies underestimate costs of air pollution by more than a third because they do not take into account the long-term, compounding effects of health costs. The economic effects of emissions changes far exceed the influence of climate alone.United States Department of Energy, Office of Science (BER) grants DE-FG02-94ER61937 and DE-FG02-93ER61677, the United States Environmental Protection Agency grant EPA-XA-83344601-0, and the industrial and foundation sponsors of the MIT Joint Program on the Science and Policy of Global Change

Global 3-D Land-Ocean-Atmosphere Model for Mercury: Present-Day Versus Preindustrial Cycles and Anthropogenic Enrichment Factors for Deposition

We develop a mechanistic representation of land-atmosphere cycling in a global 3-D ocean-atmosphere model of mercury (GEOS-Chem). The resulting land-ocean-atmosphere model is used to construct preindustrial and present biogeochemical cycles of mercury, to examine the legacy of past anthropogenic emissions, to map anthropogenic enrichment factors for deposition, and to attribute mercury deposition in the United States. Land emission in the model includes prompt recycling of recently deposited mercury (600 Mg a−1 for present day), soil volatilization (550 Mg a−1), and evapotranspiration (550 Mg a−1). The spatial distribution of soil concentrations is derived from local steady state between land emission and deposition in the preindustrial simulation, augmented for the present day by a 15% increase in the soil reservoir distributed following the pattern of anthropogenic deposition. Mercury deposition and hence emission are predicted to be highest in the subtropics. Our atmospheric lifetime of mercury against deposition (0.50 year) is shorter than past estimates because of our accounting of Hg(0) dry deposition, but recycling from surface reservoirs results in an effective lifetime of 1.6 years against transfer to long-lived reservoirs in the soil and deep ocean. Present-day anthropogenic enrichment of mercury deposition exceeds a factor of 5 in continental source regions. We estimate that 68% of the deposition over the United States is anthropogenic, including 20% from North American emissions (20% primary and <1% recycled through surface reservoirs), 31% from emissions outside North America (22% primary and 9% recycled), and 16% from the legacy of anthropogenic mercury accumulated in soils and the deep ocean.Earth and Planetary SciencesEngineering and Applied Science

Trade in the balance: reconciling trade and climate policy: report of the Working Group on Trade, Investment, and Climate Policy

This repository item contains a report published by the Working Group on Trade, Investment, and Climate Policy at The Frederick S. Pardee Center for the Study of the Longer-Range Future at Boston University, and the Global Economic Governance Initiative at Boston University.This report outlines the general tensions between the trade and investment regime and climate policy, and outlines a framework toward making trade and investment rules more climate friendly. Members of the working group have contributed short pieces addressing a range of issues related to the intersection of trade and climate policy. The first two are by natural scientists. Anthony Janetos discusses the need to address the effects of international trade on efforts to limit the increase in global annual temperature to no more than 2oC over preindustrial levels. James J. Corbett examines the failure of the Trans Pacific Partnership (TPP) and the Transatlantic Trade and Investment Partnership (TTIP) to adequately address the environmental implications of shipping and maritime transport. The next two pieces are by economists who examine economic aspects of the trade-climate linkage. Irene Monasterolo and Marco Raberto discuss the potential impacts of including fossil fuel subsidies reduction under the TTIP. Frank Ackerman explores the economic costs of efforts to promote convergence of regulatory standards between the United States and the European Union under the TTIP. The following two contributions are by legal scholars. Brooke Güven and Lise Johnson explore the potential for international investment treaties to redirect investment flows to support climate change mitigation and adaptation, particularly with regard to China and India. Matt Porterfield provides an overview of the ways in which both existing and proposed trade and investment agreements could have either “climate positive” or “climate negative” effects on mitigation policies. The final article is by Tao Hu, a former WTO trade and environment expert advisor for China and currently at the World Wildlife Fund, arguing that the definition of environmental goods and services’ under the WTO negotiations needs to be expanded to better incorporate climate change