Development and Application of Urban High Temporal-Spatial Resolution Vehicle Emission Inventory Model and Decision Support System

This paper reports on the development and application of an urban high temporal-spatial resolution vehicle emission inventory model and decision support system based on the current situation in China and actual vehicle emission control requirements. The system incorporates a user-friendly modular architecture that integrates a vehicle emission model and a decision support platform and includes scenario analysis and visualisation capabilities. A bottom-up approach based on localised emission factors and actual on-road driving condition has been adopted to develop the system. As a case study of application and evaluation, an emission reduction effect analysis of the supposed low-emission zone (LEZ) policy in Beijing (2012) was conducted. According to the simulated results in the forms of tables, histograms and grid maps, the establishment of this LEZ had a definite effect on the emission reduction of various types of air pollutants, especially carbon monoxide and hydrocarbon. In the system, the simulation methodology for identifying environmental benefits brought by the LEZ policy could be used to assess other similar environmental policies. Through flexible modification of configuration values or input data variables, the efficacy of separate or joint policies could be quantifiably evaluated and graphically displayed.     

Evaluation of wireless sensor networks (WSNs) for remote wetland monitoring: design and initial results

Here, we describe and evaluate two low-power wireless sensor networks (WSNs) designed to remotely monitor wetland hydrochemical dynamics over time scales ranging from minutes to decades. Each WSN (one student-built and one commercial) has multiple nodes to monitor water level, precipitation, evapotranspiration, temperature, and major solutes at user-defined time intervals. Both WSNs can be configured to report data in near real time via the internet. Based on deployments in two isolated wetlands, we report highly resolved water budgets, transient reversals of flow path, rates of transpiration from peatlands and the dynamics of chromophoric-dissolved organic matter and bulk ionic solutes (specific conductivity)—all on daily or subdaily time scales. Initial results indicate that direct precipitation and evapotranspiration dominate the hydrologic budget of both study wetlands, despite their relatively flat geomorphology and proximity to elevated uplands. Rates of transpiration from peatland sites were typically greater than evaporation from open waters but were more challenging to integrate spatially. Due to the high specific yield of peat, the hydrologic gradient between peatland and open water varied with precipitation events and intervening periods of dry out. The resultant flow path reversals implied that the flux of solutes across the riparian boundary varied over daily time scales. We conclude that WSNs can be deployed in remote wetland-dominated ecosystems at relatively low cost to assess the hydrochemical impacts of weather, climate, and other perturbations.     

Displacement in urban areas: new challenges, new partnerships

Rapid urbanisation is a key characteristic of the modern world, interacting with and reinforcing other global mega trends, including armed conflict, climate change, crime, environmental degradation, financial and economic instability, food shortages, underemployment, volatile commodity prices, and weak governance. Displaced people also are affected by and engaged in the process of urbanisation. Increasingly, refugees, returnees, and internally displaced persons (IDPs) are to be found not in camps or among host communities in rural areas, but in the towns and cities of developing and middle-income countries. The arrival and long-term settlement of displaced populations in urban areas needs to be better anticipated, understood, and planned for, with a particular emphasis on the establishment of new partnerships. Humanitarian actors can no longer liaise only with national governments; they must also develop urgently closer working relationships with mayors and municipal authorities, service providers, urban police forces, and, most importantly, the representatives of both displaced and resident communities. This requires linking up with those development actors that have established such partnerships already.     

Emission Inventory Case Studies—Policy Aspects

The Clean Air Act (and proposed Clean Air Act Amendments in H.R. 5252) are addressed relative to quantification of emission data. Six case studies performed for the National Commission on Air Quality (NCAQ) are reviewed. The models used to quantify the amount of emissions needed to meet air quality standards for O₃, particulates, and SO₂ are reviewed for each case study city. Technical and resource limitations in meeting the Act’s emission inventory requirements for nonattainment plans.and PSD permitting are outlined.     

The Effectiveness of Aeration Recirculation in Controlling VOC Emissions from Publicly Owned Treatment Works

Abstract

The effects of aeration recirculation on oxygen transfer and the fate of five volatile organic compounds (VOCs) commonly found in publicly owned treatment works (POTWs) influent are studied using various modeling approaches. The five compounds are benzene, chloroform, methylene chloride, toluene, and trichloroethylene. The models predict that the overall oxygen transfer efficiency can be increased by 96.7% at 50% aeration recirculation with only a 9.6% drop in oxygen transfer rate. The emission reductions and biodegradation improvements are compound specific; for the compounds investigated here, about 40% emission reductions and 16% biodegradation increases can be achieved at 50% aeration recirculation. The temperature effect on the VOC fate mechanisms is also investigated. Overall, the model predictions reveal that up to 50% aeration recirculation is effective in controlling VOC emissions.     

Rotary drum soil blending for source zone remediation: Various application scenarios

Mechanical blending of contaminated soil with amendments has recently reemerged as an important treatment technology. From its original application using large‐diameter augers in the early 1990s to the current use of rotary drum blenders, soil blending is being used as an alternative to other remediation technologies like amendment injection and soil vapor and groundwater extraction. Shallow (approximately 10 m below ground surface [bgs] or less) soil blending also offers an alternative to excavation and disposal. Soil blending has been used to remediate a site with various contaminants including, but not limited to, chlorinated solvents, petroleum, and metals. The types of soils susceptible to soil blending vary from sands and gravels to silts and clays to fractured rock and combinations of all of these. The types of amendments blended include oxidants, reducing agents, biological enhancements, and stabilizing amendments. Soil blending systems deliver the power to the mixing head to adequately mix the soil and amendment to enhance remediation effectiveness. Since long‐term contamination is often a result of heterogeneously distributed residual contaminant in localized source zones that are difficult to access, the typical aim of soil blending is to homogenize the soil while effectively distributing amendment to these zones made accessible by blending. By effectively homogenizing the soil, however, soil blending will increase the void ratio and disrupt the shear strength and bearing capacity of the soil so an important component of a soil blending technology is proper recovery of these geotechnical parameters. This can be achieved by using well‐known soil improvement techniques such as amending all or a portion of the blended area with Portland cement or lime. Several case studies of soil blending treatments of different contaminants and amendments in various soil types are provided.     

Integrating Large Wood Jams into Hydraulic Models: Evaluating a Porous Plate Modeling Method

Large wood (LW) jams are key riverine habitat features that affect hydraulic processes and aquatic habitat. The hydraulic influence of LW jams is poorly understood due to the complexity of fluid dynamics around irregular, porous structures. Here we validated a method for two‐dimensional hydraulic modeling of porous LW jams using the open‐source modeling software Delft3D‐FLOW. We sampled 19 LW jams at three reaches across the Columbia River Basin in the United States. We used computer‐generated porous plates to represent LW jams in the modeling software and calibrated our modeling method by comparing model outputs to measured depths and velocities at validation points. We found that modeling outputs are error‐prone when LW jams are not represented. By representing LW jams as porous plates we reduced average velocity root mean square error (RMSE) values (i.e., improved model accuracy) by 42.8% and reduced average depth RMSE values by 5.2%. These differences impacted habitat suitability index modeling. We found a 15.1% increase in weighted useable area for juvenile steelhead at one test site when LW jams were simulated vs. when they were ignored. We investigated patterns in average RMSE improvements with varying jam size, bankfull obstruction, porosity, and structure type, and river complexity. We also identified research gaps related to field estimation of LW jam porosity and porous structure modeling methods.     

Life cycle assessment of a pulverized coal power plant with post-combustion capture, transport and storage of CO2

In this study the methodology of life cycle assessment has been used to assess the environmental impacts of three pulverized coal fired electricity supply chains with and without carbon capture and storage (CCS) on a cradle to grave basis. The chain with CCS comprises post-combustion CO₂ capture with monoethanolamine, compression, transport by pipeline and storage in a geological reservoir. The two reference chains represent sub-critical and state-of-the-art ultra supercritical pulverized coal fired electricity generation. For the three chains we have constructed a detailed greenhouse gas (GHG) balance, and disclosed environmental trade-offs and co-benefits due to CO₂ capture, transport and storage. Results show that, due to CCS, the GHG emissions per kWh are reduced substantially to 243 g/kWh. This is a reduction of 78 and 71% compared to the sub-critical and state-of-the-art power plant, respectively. The removal of CO₂ is partially offset by increased GHG emissions in up- and downstream processes, to a small extent (0.7 g/kWh) caused by the CCS infrastructure. An environmental co-benefit is expected following from the deeper reduction of hydrogen fluoride and hydrogen chloride emissions. Most notable environmental trade-offs are the increase in human toxicity, ozone layer depletion and fresh water ecotoxicity potential for which the CCS chain is outperformed by both other chains. The state-of-the-art power plant without CCS also shows a better score for the eutrophication, acidification and photochemical oxidation potential despite the deeper reduction of SO_x and NO_x in the CCS power plant. These reductions are offset by increased emissions in the life cycle due to the energy penalty and a factor five increase in NH₃ emissions.     

CO2 transportation for carbon capture and storage: Sublimation of carbon dioxide from a dry ice bank

Climate change is being caused by greenhouse gases such as carbon dioxide (CO₂). Carbon capture and storage (CCS) is of interest to the scientific community as one way of achieving significant global reductions of atmospheric CO₂ emissions in the medium term. CO₂ would be captured from large stationary sources such as power plants and transported via pipelines under high pressure conditions to underground storage. If a downward leakage from a surface transportation system module occurs, the CO₂ would undergo a large temperature reduction and form a bank of “dry ice” on the ground surface; the sublimation of the gas from this bank represents an area source term for subsequent atmospheric dispersion, with an emission rate dependent on the energy balance at the bank surface. Gaseous CO₂ is denser than air and tends to remain close to the surface; it is an asphyxiant, a cerebral vasodilator and at high concentrations causes rapid circulatory insufficiency leading to coma and death. Hence a subliming bank of dry ice represents safety hazard. A model is presented for evaluating the energy balance and sublimation rate at the surface of a solid frozen CO₂ bank under different environmental conditions. The results suggest that subliming gas behaves as a proper dense gas (i.e. it remains close to the ground surface) only for low ambient wind speeds.     

Effect of soil ageing on in vivo arsenic bioavailability in two dissimilar soils

Arsenic (As) bioavailability in spiked soils aged for up to 12 months was assessed using in vitro and in vivo methodologies. Ageing (natural attenuation) of spiked soils resulted in a decline in in vivo As bioavailability (swine assay) of over 75% in soil A (Red Ferrosol) but had no significant effect on in vivo As bioavailability even after 12 months of ageing in soil B (Brown Chromosol). Sequential fractionation, however, indicated that there was repartitioning of As within the soil fractions extracted during the time course investigated. In soil A, the As fraction associated with the more weakly bound soil fractions decreased while the residual fraction increased from 12% to 35%. In contrast, little repartitioning of As was observed in soil B indicating that natural attenuation may be only applicable for As in soils containing specific mineralogical properties.