Estimating national landfill methane emissions: an application of the 2006 Intergovernmental Panel on Climate Change Waste Model in Panama

This paper estimates national methane emissions from solid waste disposal sites in Panama over the time period 1990-2020 using both the 2006 Intergovernmental Panel on Climate Change (IPCC) Waste Model spreadsheet and the default emissions estimate approach presented in the 1996 IPCC Good Practice Guidelines. The IPCC Waste Model has the ability to calculate emissions from a variety of solid waste disposal site types, taking into account country- or region-specific waste composition and climate information, and can be used with a limited amount of data. Countries with detailed data can also run the model with country-specific values. The paper discusses methane emissions from solid waste disposal; explains the differences between the two methodologies in terms of data needs, assumptions, and results; describes solid waste disposal circumstances in Panama; and presents the results of this analysis. It also demonstrates the Waste Model's ability to incorporate landfill gas recovery data and to make projections. The former default method methane emissions estimates are 25 Gg in 1994, and range from 23.1 Gg in 1990 to a projected 37.5 Gg in 2020. The Waste Model estimates are 26.7 Gg in 1994, ranging from 24.6 Gg in 1990 to 41.6 Gg in 2020. Emissions estimates for Panama produced by the new model were, on average, 8% higher than estimates produced by the former default methodology. The increased estimate can be attributed to the inclusion of all solid waste disposal in Panama (as opposed to only disposal in managed landfills), but the increase was offset somewhat by the different default factors and regional waste values between the 1996 and 2006 IPCC guidelines, and the use of the first-order decay model with a time delay for waste degradation in the IPCC Waste Model.     

Are native naiads more tolerant to pollution than exotic freshwater bivalve species? An hypothesis tested using physiological responses of three species transplanted to mercury contaminated sites in the Ebro River (NE, Spain)

In the lower Ebro River exist the paradoxical convergence of relatively well preserved river dynamics with the historical presence of a chloralkali plant with a long history of mercury discharges and the recent invasion of foreign bivalves species. Here we performed a comparative study on two alien bivalves, the Zebra mussel and the Asian clam (Dreissena polymorpha and Corbicula fluminea), and one protected species of naiads (Psilunio littoralis), which is the most common species of the freshwater mussel assemblages in this river. Individuals of the three species were transplanted to three sites that included a clean unpolluted upstream site, a contaminated location next to the mercury source and a downstream one. The study focused on digestive gland antioxidant and oxidative stress responses such as antioxidant enzymes, glutathione S transferase, glutathione levels, metallothionein proteins, DNA strand breaks and lipid peroxidation levels. Results evidenced interspecies differences on accumulation levels of mercury, antioxidant defensive systems and oxidative tissue damage. The naiad species, despite of accumulating more mercury showed the greatest antioxidant defensive potential, which was characterized by having high constitutive activities of glutathione S transferase and inducible activities and levels of key antioxidant enzymes and glutathione. Exposed individuals of C. fluminea had moderate levels of metal accumulation, the highest activities of antioxidant enzymes but also high levels of lipid peroxidation. D. polymorpha mussels showed the lowest levels of mercury but the lowest antioxidant responses and consequently the highest levels of oxidative injuries in the DNA and of mortality. Our results support the hypothesis that naiad species might be more tolerant to pollution than exotic species.     

Analysis of C1, C2, and C10 through C33 particle-phase and semi-volatile organic compound emissions from heavy-duty diesel engines

To meet increasingly stringent regulations for diesel engines, technologies such as combustion strategies, aftertreatment components, and fuel composition have continually evolved. The emissions reduction achieved by individual aftertreatment components using the same engine and fuel has been assessed and published previously (Liu et al., 2008a, Liu et al., 2008b, Liu et al., 2008c). The present study instead adopted a systems approach to evaluate the net effect of the corresponding technologies for model-year 2004 and 2007 engines. The 2004 engine was equipped with an exhaust gas recirculation (EGR) system, while the 2007 engine had an EGR system, a crankcase emissions coalescer, and a diesel particulate filter. The test engines were operated under the transient federal test procedure and samples were collected with a source dilution sampling system designed to stimulate atmospheric cooling and dilution conditions. The samples were analyzed for elemental carbon, organic carbon, and C₁, C₂, and C₁₀ through C₃₃ particle-phase and semi-volatile organic compounds. Of the more than 150 organic species analyzed, the largest portion of the emissions from the 2004 engine consisted of formaldehyde, acetaldehyde, and naphthalene and its derivatives, which were significantly reduced by the 2007 engine and emissions technology. The systems approach in this study simulates the operation of real-world diesel engines, and may provide insight into the future development of integrated engine technology. The results supply updated information for assessing the impact of diesel engine emissions on the chemical processes, radiative properties, and toxic components of the atmosphere.     

Spatial variability of atrazine and metolachlor dissipation on dryland no-tillage crop fields in Colorado

An area of interest in precision farming is variable-rate application of herbicides to optimize herbicide use efficiency and minimize negative off-site and non-target effects. Site-specific weed management based on field scale management zones derived from soil characteristics known to affect soil-applied herbicide efficacy could alleviate challenges posed by post-emergence precision weed management. Two commonly used soil-applied herbicides in dryland corn (Zea mays L.) production are atrazine and metolachlor. Accelerated dissipation of atrazine has been discovered recently in irrigated corn fields in eastern Colorado. The objectives of this study were (i) to compare the rates of dissipation of atrazine and metolachlor across different soil zones from three dryland no-tillage fields under laboratory incubation conditions and (ii) to determine if rapid dissipation of atrazine and/or metolachlor occurred in dryland soils. Herbicide dissipation was evaluated at time points between 0 and 35 d after soil treatment using a toluene extraction procedure with GC/MS analysis. Differential rates of atrazine and metolachlor dissipation occurred between two soil zones on two of three fields evaluated. Accelerated atrazine dissipation occurred in soil from all fields of this study, with half-lives ranging from 1.8 to 3.2 d in the laboratory. The rapid atrazine dissipation rates were likely attributed to the history of atrazine use on all fields investigated in this study. Metolachlor dissipation was not considered accelerated and exhibited half-lives ranging from 9.0 to 10.7 d in the laboratory.     

Passive ammonia monitoring in the United States: comparing three different sampling devices

The need for ambient gaseous ammonia (NH(3)) measurements has increased in the last decade as reactive NH(3) concentrations and deposition fluxes show little change even with tightening standards on nitrogen oxides (NO(x)) emissions. Currently, there are several networks developing methods for adding NH(3) measurements in the U.S. Gaseous NH(3) measurements will provide scientists and policymakers data which can be used to estimate ecosystem inputs, validate air quality models including trends and regional variability, and evaluate changes to the environment based on additional emission reduction requirements and estimates of critical nitrogen load exceedances. The passive samplers described in this paper were deployed in duplicate or triplicate and collocated with annular denuders or continuous instruments to determine their accuracy. The samplers assessed included the Adapted Low-Cost Passive High Absorption (ALPHA), Radiello(?), and Ogawa passive samplers. The median relative percent differences (MRPD) between the reference method and passive samplers for the ALPHA, Radiello(?) and Ogawa were -2.4%, -37% and -44%, respectively. The precision between duplicate samplers for the ALPHA and Ogawa samplers, was 7% and 6%, respectively. Triplicate Radiello(?) precision was assessed using the coefficient of variation (CV). The CV for the Radiello(?) samplers was 10%. This article discusses the statistical results from these studies.     

Fate of Lu(III) sorbed on 2-line ferrihydrite at pH 5.7 and aged for 12 years at room temperature. II: insights from STEM-EDXS and DFT calculations

Environmental Science and Pollution Research - Transformation products of two-line ferrihydrite associated with Lu(III) were studied after 12 years of aging using aberration-corrected...     

Dueling Land Ethics: Uncovering Agricultural Stakeholder Mental Models to Better Understand Recent Land Use Conversion

The aim of this paper is to investigate how alternative land ethics of agricultural stakeholders may help explain recent land use changes. The paper first explores the historical development of the land ethic concept in the United States and how those ethics have impacted land use policy and use of private lands. Secondly, primary data gathered from semi-structured interviews of farmers, ranchers, and influential stakeholders are then analyzed using stakeholder analysis methods to identify major factors considered in land use decisions, priorities of factors of each group, and to define relevant mental models describing each group’s view of the land ethic concept. Results show that these stakeholder groups prioritize land use factors qualitatively differently and possess strikingly different land ethics. It is concluded that shifts in stakeholder land ethics have contributed to recent land use changes. Lastly, we discuss how current agricultural policy sends mixed signals about preferred land use and the potential ramifications based on the different land ethics we’ve described.     

Integument and defence in larva and prepupa of a sawfly living on a semi-aquatic plant

The larvae of the sawfly Rhadinoceraea micans live and feed on a semi-aquatic plant, Iris pseudacorus, and their integument is strongly hydrophobic. The hydrophobicity is part of a chemical defence strategy, easy bleeding, also known from congeners. The prepupae burrow into the soil where they form a cocoon in which they pupate, thus implying different micro-environmental conditions. The cuticle structure and wetting defensive effectiveness of R. micans were compared between larvae and prepupae. The two stages were similarly well defended against attacking ants by the bleeding of a deterrent hemolymph, whereas they were dissimilar in the cuticle surface that presented sculptures and wax crystals at the larval stage only. The integument of prepupae was less structured, and hydrophilic. Larvae of R. micans exhibit, among sawflies, an exceptional cuticle structuring and we assume that they occupy this particular niche of a semi-aquatic environment to avoid encounters with ground-dwelling predators whereas prepupae may benefit from the chemical defence acquired at larval stage.     

Using different multivariate approaches to assess water quality of qanats in arid zones of Southern Central Mexico

Environmental Science and Pollution Research - Qanats in the aquifer of the Tehuacán Valley (Mexico) represent an ancient way of using groundwater that is still practiced today. They are used...