Analysis of PM2.5 and PM10 in the atmosphere of Mexico City during 2000-2002

During the last 10 years, high atmospheric concentrations of airborne particles recorded in the Mexico City metropolitan area have caused concern because of their potential harmful effects on human health. Four monitoring campaigns have been carried out in the Mexico City metropolitan area during 2000-2002 at three sites: (1) Xalostoc, located in an industrial region; (2) La Merced, located in a commercial area; and (3) Pedregal, located in a residential area. Results of gravimetric and chemical analyses of 330 samples of particulate matter (PM) with an aerodynamic diameter less than 2.5 microm (PM2.5) and PM with an aerodynamic diameter less than 10 microm (PM10) indicate that (1) PM2.5/PM10 average ratios were 0.42, 0.46, and 0.52 for Xalostoc, La Merced, and Pedregal, respectively; (2) the highest PM2.5 and PM10 concentrations were found at the industrial site; (3) PM2.5 and PM10 concentrations were lower at nighttime; (4) PM2.5 and PM10 spatial averages concentrations were 35 and 76 microg/m3, respectively; and (5) when the PM2.5 standard was exceeded, nitrate, sulfate, ammonium, organic carbon, and elemental carbon concentrations were high. Twenty-four hour averaged PM2.5 concentrations in Mexico City and Sao Paulo were similar to those recorded in the 1980s in Los Angeles. PM10 concentrations were comparable in Sao Paulo and Mexico City but 3-fold lower than those found in Santiago.     

发展中的亚洲推动全球经济继续增长

2005年,世界经济增长4．9％，略低于2004年的5．3％。全球经济增长的领头羊是年增长10．2％的中国和年增长8．5％的印度。世界经济最近的迅猛增长是近半个世纪经济增长的延续。1950年，世界所有货物和服务的毛总产值（按购买力平价外汇率计算）为7万亿美元，而2005年则上升到61万亿美元。在这一期间，人年均收入从2923美元增加到9440美元。预计2006和2007年增长约为5％。     

Characterization of airborne particles at a high-btu coal-gasification pilot plant

Airborne particles in fugitive emissions have been measured at a slagging fixed-bed coal-gasification pilot plant using lignite. Sampling was conducted during shutdown operations and opening of the gasifier following an aborted startup. Aerosol collected with a Sierra high-volume impactor was subjected to analysis by gas chromatography, mass spectrometry, and scanning electron microscopy; aerosol collected with an Andersen low-volume impactor was subjected to flameless atomic absorption analysis. The data show that the bulk of the trace organic material is associated with small particles: these data are similar to data on ambient air reported in the literature. Particle morphologies resemble those of fly ash from coal combustion, including smooth spheres, vesicular spheres, and crystalline material. Trace element size distributions are bimodal and resemble data for ambient air. Pb-containing particles are generally submicron, while particles containing Al, Fe, and other crustal species are mostly of supermicron size. Aluminum-based aerosol enrichment factors calculated from the lignite composition show that the composition of the aerosol resembles that of the coal, with the exception of modest enrichments of Mg, Na, As, and Pb in the submicron size range. Aerosol enrichment factors based on the earth's crustal composition are somewhat greater than those based on coal composition for several elements, suggesting potential errors in using crustal enrichment data to investigate chemical fractionation during aerosol formation.     

Restoring habitat corridors in fragmented landscapes using optimization and percolation models

Landscape fragmentation and habitat loss are significant threats to the conservation of biological diversity. Creating and restoring corridors between isolated habitat patches can help mitigate or reverse the impacts of fragmentation. It is important that restoration and protection efforts be undertaken in the most efficient and effective way possible because conservation budgets are often severely limited. We address the question of where restoration should take place to efficiently reconnect habitat with a landscape-spanning corridor. Building upon findings in percolation theory, we develop a shortest-path optimization methodology for assessing the minimum amount of restoration needed to establish such corridors. This methodology is applied to large numbers of simulated fragmented landscapes to generate mean and variance statistics for the amount of restoration needed. The results provide new information about the expected level of resources needed to realize different corridor configurations under different degrees of fragmentation and different characterizations of habitat connectivity (“neighbor rules”). These results are expected to be of interest to conservation planners and managers in the allocation of conservation resources to restoration projects.     

Integrated Environmental Assessment of the Mid-Atlantic Region with Analytical Network Process

A decision analysis method for integrating environmental indicators was developed. This was a combination of Principal Component Analysis (PCA) and the Analytic Network Process (ANP). Being able to take into account the interdependency among variables, the method was capable of ranking ecosystems in terms of environmental conditions and suggesting cumulative impacts across a large region. Using data on land cover, population, roads, streams, air pollution, and topography of the Mid-Atlantic Region of the United States, we were able to point out areas which were in relatively poor condition and/or vulnerable to future deterioration regarding various environmental aspects. The method offered an easy and comprehensive way to combine the strengths of conventional multivariate statistics (PCA) and decision-making science tool (ANP) for integrated environmental assessment.     

An Overview of Data Integration Methods for Regional Assessment

The U.S. Environmental Protections Agency's (U.S. EPA) Regional Vulnerability Assessment(ReVA) program has focused much of its research over the last five years on developing and evaluating integration methods for spatial data. An initial strategic priority was to use existing data from monitoring programs, model results, and other spatial data. Because most of these data were not collected with an intention of integrating into a regional assessment of conditions and vulnerabilities, issues exist that may preclude the use of some methods or require some sort of data preparation. Additionally, to support multi-criteria decision-making, methods need to be able to address a series of assessment questions that provide insights into where environmental risks are a priority. This paper provides an overview of twelve spatial integration methods that can be applied towards regional assessment, along with preliminary results as to how sensitive each method is to data issues that will likely be encountered with the use of existing data.     

How Hydrologic Connectivity Regulates Water Quality in River Corridors

Downstream flow in rivers is repeatedly delayed by hydrologic exchange with off‐channel storage zones where biogeochemical processing occurs. We present a dimensionless metric that quantifies river connectivity as the balance between downstream flow and the exchange of water with the bed, banks, and floodplains. The degree of connectivity directly influences downstream water quality — too little connectivity limits the amount of river water exchanged and leads to biogeochemically inactive water storage, while too much connectivity limits the contact time with sediments for reactions to proceed. Using a metric of reaction significance based on river connectivity, we provide evidence that intermediate levels of connectivity, rather than the highest or lowest levels, are the most efficient in removing nitrogen from Northeastern United States’ rivers. Intermediate connectivity balances the frequency, residence time, and contact volume with reactive sediments, which can maximize the reactive processing of dissolved contaminants and the protection of downstream water quality. Our simulations suggest denitrification dominantly occurs in riverbed hyporheic zones of streams and small rivers, whereas vertical turbulent mixing in contact with sediments dominates in mid‐size to large rivers. The metrics of connectivity and reaction significance presented here can facilitate scientifically based prioritizations of river management strategies to protect the values and functions of river corridors.     

Spatial Convergence in Major Dissolved Ion Concentrations and Implications of Headwater Mining for Downstream Water Quality

Spatial patterns in major dissolved solute concentrations were examined to better understand impact of surface coal mining in headwaters on downstream water chemistry. Sixty sites were sampled seasonally from 2012 to 2014 in an eastern Kentucky watershed. Watershed areas (WA) ranged from 1.6 to 400.5 km² and were mostly forested (58%–95%), but some drained as much as 31% surface mining. Measures of total dissolved solutes and most component ions were positively correlated with mining. Analytes showed strong convergent spatial patterns with high variability in headwaters (<15 km² WA) that stabilized downstream (WA > 75 km²), indicating hydrologic mixing primarily controls downstream values. Mean headwater solute concentrations were a good predictor of downstream values, with % differences ranging from 0.55% (Na⁺) to 28.78% (Mg²⁺). In a mined scenario where all headwaters had impacts, downstream solute concentrations roughly doubled. Alternatively, if mining impacts to headwaters were minimized, downstream solute concentrations better approximated the 300 μS/cm conductivity criterion deemed protective of aquatic life. Temporal variability also had convergent spatial patterns and mined streams were less variable due to unnaturally stable hydrology. The highly conserved nature of dissolved solutes from mining activities and lack of viable treatment options suggest forested, unmined watersheds would provide dilution that would be protective of downstream aquatic life.     

Conceptualising Reuse in African Households: Perspectives from Chembe,Malawi

African households are often models of sustainability, practicing daily behaviours, which, if even not directly associated by the individual with Western conceptualisations of ‘recycling’ or ‘reuse’, have dramatically positive impacts on the amounts of household waste generated. However, rarely has the African household been given the same consideration, and there is a poor understanding within the discipline how poor individuals, and Africans in particular, understand and conceptualise ‘waste’ as both a problem and a resource. Drawing on Kennedy and Appadurai’s theoretical perspectives, the purpose of this article is to critically examine and contextualise household solid waste reuse practices in Chembe, Malawi, a rapidly densifying village and a constituent part of one of the nation’s premier resort destinations. Drawing on extensive ethnographic fieldwork with residents and stakeholders, findings suggest that, within Chembe, reuse practices, and the motivations that drive them, are both widespread and diverse, with a multitude of ‘waste’ items living multiple ‘lives’ before being ultimately discarded as ‘trash’. These behaviours are facilitated by the fact that many desirable waste items are widely available locally within Chembe, and although some of these reuse practices may be widespread within Malawi, others have been uniquely fostered by Chembe’s position as an affluent tourism destination with abundant and easily accessible waste streams. This investigation is particularly important within the context of rural Africa, and the Global South more broadly. Moreover, it should critically inform circular economy, zero waste, and broader waste management studies discourse, where African households have been habitually treated as problems needing solutions, rather than potential sources of innovation and learning.

     

The missing link? Implications of internal,external, and relational attribution combinations for leader–member exchange,relationship work,self‐work,and conflict

Attributions are causal explanations made by individuals in response to important, novel, and/or unexpected events. Numerous attribution theories have examined how people use information to make attributions and how attributions impact an individual's subsequent emotions and outcomes. However, this research has only recently considered the implications of dyadic‐level attributions (i.e., relational attributions), particularly in the context of leader–follower relationships in organizations. Therefore, the purpose of this theoretical paper is threefold. First, we integrate research on attributional biases into the research on relational attributions. Second, we integrate and extend attribution theory to consider the implications of convergent and divergent internal, external‐person, external‐situational, and relational attributions for leader–member exchange (LMX) quality, relationship work, self‐work, and conflict. Third, we make the implicit ranking of attribution combinations and the resultant levels of relationship work explicit. In doing so, we contribute to attribution theory and research by proposing how attribution combinations produce positive and negative outcomes that are both intrapersonal and interpersonal. Further, we contribute to the LMX literature by explicating how leader–follower attribution combinations influence relationship quality.