Study of individual reactions of the sour compression process for the purification of oxyfuel-derived CO2

Following the feasibility study of sour compression process as a novel purification method of producing NO_x-free, SO₂-free oxyfuel-derived CO₂ using actual fluegas, in this paper, we present the study of the individual reactions taking place in the process in a controlled environment. We have previously showed that an increase of NO/NO₂ concentration in the inlet stream is beneficial for SO₂ removal as NO₂ promotes SO₂ oxidation and the further removal as liquid acid. In this study we show that the reaction SO₂ + NO₂ → SO₃ + NO does not take place significantly in the absence of liquid water at a range of conditions relevant to the sour compression process. When liquid water is present, SO₂ is oxidised by NO₂ regenerating NO with the rate of conversion of SO₂ being dependent on the acid concentration in the liquid. The formation of small liquid droplets where very low levels of pH (?0) can be reached is shown to be of great importance to the SO₂ + NO₂ conversion process.     

Kin conflict over caste determination in social Hymenoptera

We argue that caste determination, the process whereby females in the social Hymenoptera develop into either queens or workers, is subject to kin-selected conflict. Potential conflict arises because developing females are more closely related to their would-be offspring than to those of other females. Therefore, they may favour becoming queens contrary to the interests of other developing females and of existing queens and workers. We suggest two contexts leading to potential caste conflict. The first occurs when queens are reared in a reproductive phase following an ergonomic phase of worker production, while the second occurs when queens and workers are reared simultaneously. The first context assumes that workers' per capita contribution to colony survival and productivity falls with rising colony size. A critical feature influencing whether potential conflict is realized is the extent to which developing females can determine their own caste (“self-determination”). Self-determination is facilitated when female larvae control their own food intake and when queen-worker size dimorphism is low. We know of no strong evidence for actual conflict over caste fate arising in the first context. However, stingless bees and polygynous ants with excess queen-potential larvae that are either forced to develop as workers or are culled as adults demonstrate actual caste conflict in the second context. Caste conflict does not preclude caste regulation for “the good of the colony”, but such regulation is contingent on either the absence of potential conflict or on developing females losing control of their caste fate. Received: 22 March 1999 / Received in revised form: 15 June 1999 / Accepted: 19 June 1999     

Halogenated persistent organic pollutants in deep water fish from waters to the west of Scotland

Halogenated persistent organic pollutants [polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs)] along with total lipid, were measured in the liver and muscle of three species of deep water fish (black scabbard, black dogfish (liver only) and roundnose grenadier) collected from the Rockall fishing area, to the west of Scotland, between 2006 and 2008. Both contaminant groups were detected in the muscle and liver, with concentrations of PCBs being higher than PBDEs. There were no significant differences in the PCB or PBDE concentrations between the three species, or different sampling locations in the Rockall fishing area. PCB concentrations (ΣICES (International Council for the Exploration of the Sea)7 PCBs) greater than 500 μg kg⁻¹ lipid weight were found in 26 of the 106 liver samples. PCB concentrations were compared to OSPAR assessment criteria, concentrations were above background but below Environmental Assessment Criteria. Estimated Toxic Equivalent (TEQ) concentrations, calculated using published models, in the fish muscle and liver indicated that consumption of deep water fish is unlikely to represent a risk to human health. The high squalene content in some of the black dogfish liver necessitated an additional clean-up step, involving gel permeation chromatography, when analyzing for PBDEs. Concentrations of PBDEs were low with many congeners being below detection limits, particularly in the muscle. There are currently no assessment criteria available for PBDEs. Furthermore, there is only very limited data on PBDEs in deep water fish. However, the concentrations observed in this study were similar to the concentrations recently reported in Mediterranean deep water fish.     

Value of biochars from Miscanthus x giganteus cultivated on contaminated soils to decrease the availability of metals in multicontaminated aqueous solutions

The objective of this study was to evaluate the sorption efficiency of eight biochars, made from Miscanthus x giganteus cultivated on contaminated agricultural soil, in aqueous solutions contaminated with metals alone or mixed with polycyclic aromatic hydrocarbons. These biochars were produced in different pyrolysis conditions (temperature, 400/600 °C; heating rate, 5/10 °C min⁻¹; duration, 45/90 min) and compared with an uncontaminated commercialized biochar made of wood. The physicochemical characterization of the Miscanthus biochars confirmed the impact of the pyrolysis on the biochar parameters with substantial differences between the biochars in terms of pH, cation exchange capacity, and specific surface area. The sorption experiment showed higher sorption efficiency of Cd, Pb, and Zn for the Miscanthus biochars produced at 600 °C compared with the biochars produced at 400 °C when the aqueous solutions were mono- or multicontaminated. Furthermore, the desorption study showed that the sorption process was largely irreversible. Therefore, the high sorption capacity of Miscanthus biochars and the low sorption reversibility confirmed that these biochars are a suitable sorbent for metals.

     

Climate-Smart Design for Ecosystem Management: A Test Application for Coral Reefs

Environmental Management - The interactive and cumulative impacts of climate change on natural resources such as coral reefs present numerous challenges for conservation planning and management....     

Notes From The National Air Quality Conference

The National Air Quality Conference, which was held during January 14-16 in San Francisco, promised to “provide decision-makers in government, business, and labor with information on the possible economic and employment impacts of the federal Clean Air Act along with strategies for change.” The meeting appeared to be important from the standpoint of who was speaking, who was attending, and who was reacting. JAPCA asked Francis J. O’Donnell, editor of Air/Water Pollution Report, to provide this special report.     

Development and Demonstration of an Explicit Lumped-Parameter Biofilter Model and Design Equation Incorporating Monod Kinetics

Abstract

Biofiltration is an economical air pollution control (APC) technology, particularly suitable for the treatment of air-streams having high flow rates and low concentrations of volatile organic compounds (VOCs). This technology utilizes enzymatic catalysis at ambient conditions to mineralize such pollutants to CO₂, H₂O, and salts. A pilot-scale study conducted for more than 4 years investigated the development of a new biofiltration technology employing trickle bed air biofilters (TBABs). Following the completion of this experimental study, additional data analysis was performed to develop a simple lumped-parameter biofilter model, assuming first-order kinetics. This model related the observed biofilter performance to the principle independent physical, thermodynamic, and biochemical parameters. The initial model has subsequently been expanded to incorporate Monod kinetics. In this paper, the development and use of the final explicit lumped-parameter biofilter model and design equation, incorporating Monod kinetics, are presented. To facilitate the application of this model, practical procedures are also presented for the determination of VOC solubility, VOC biokinetic Monod parameters, and the maximum practical biofilter inlet VOC concentration.     

Physical and chemical properties of feedlot pen surfaces located on moderately coarse- and moderately fine-textured soils in southern Alberta

Southern Alberta has the highest density of feedlot cattle in Canada, and there is a concern that leaching of water and contaminants may be greater for feedlots located on coarser-textured than finer-textured soils. Our objective was to determine if infiltration and leaching were greater for a 4-yr-old feedlot located on a moderately coarse-textured (MC) soil compared with two feedlots located on moderately fine-textured (MF) soils (5- and 52-yr-old pens). Various soil physical properties of feedlot pen surfaces were measured, including field-saturated hydraulic conductivity (K(fs)) and near-saturated hydraulic conductivity at -0.9 and -3.9 cm water potential. Selected chemical properties of feedlot soil layers were measured, as well as the chloride content of the soil profile (0-100 cm). Mean K(fs), K(-0.9), and K(-3.9) values were not significantly (P > 0.10) greater at the MC site than the two MF sites, indicating no evidence of greater infiltration on coarser-textured soils. In addition, mean K(fs), K(-0.9), and K(-3.9) values of soils within feedlot pens at all three sites were significantly (P < or = 0.10) reduced by 46 to 78% compared with soil outside the pens. Depth of chloride accumulation was greatest at the 52-yr-old feedlot on MF soil (60-70 cm), followed by 4-yr-old feedlot on MC soil (40-50 cm) and 5-yr-old feedlot on MF soil (30-40 cm). Visual inspection determined that the black interface layer formed within 2 mo of cattle stocking at all three sites.     

The influence of institutions and organizations on urban waste collection systems: an analysis of waste collection system in Accra, Ghana (1985-2000)

Urban waste collection system is a pivotal component of all waste management schemes around the world. Therefore, the efficient performance and the success of these schemes in urban pollution control rest on the ability of the collection systems to fully adapt to the prevailing cultural and social contexts within which they operate. Conceptually, institutions being the rules guiding the conduct of public service provision and routine social interactions, waste collection systems embedded in institutions can only realize their potentials if they fully evolve continuously to reflect evolving social and technical matrices underlying the cultures, organizations, institutions and social conditions they are designed to address. This paper is a product of an analysis of waste collection performance in Ghana under two different institutional and/or organizational regimes; from an initial entirely public sector dependence to a current mix of public-private sector participation drawing on actual planning data from 1985 to 2000. The analysis found that the overall performance of waste collection services in Ghana increased under the coupled system, with efficiency (in terms of total waste clearance and coverage of service provision) increasing rapidly with increased private-sector controls and levels of involvement, e.g. for solid waste, collection rate and disposal improved from 51% in 1998 to about 91% in the year 2000. However, such an increase in performance could not be sustained beyond 10 years of public-private partnerships. This analysis argues that the sustainability of improved waste collection efficiency is a function of the franchise and lease arrangements between private sector group on the one hand and public sector group (local authorities) on the other hand. The analysis therefore concludes that if such franchise and lease arrangements are not conceived out of an initial transparent process, such a provision could undermine the overall sustainability of private sector initiatives in collection services delivery in the long term, as in the case of the Accra example.     

Occurrence and distribution of polycyclic aromatic hydrocarbons in surface microlayer and subsurface seawater of Lagos Lagoon,Nigeria

Polycyclic aromatic hydrocarbons (PAHs) in surface microlayer (SML) and subsurface water (SSW) of Lagos Lagoon were investigated using gas chromatography-electron capture detector (GC-ECD) technique to ascertain their occurrence and spatial distribution, origin, enrichment, and carcinogenicity. Total PAH (ΣPAH) concentrations ranged from 9.10 to 16.20 μg L^?1 in the SML and 8.90 to 13.30 μg L^?1 in the SSW. ΣPAH concentrations were relatively higher in the SML than the underlying SSW samples. The enrichment factors (EFs) of ΣPAHs ranged from 0.76 to 1.74 while the EFs of the individual PAHs varied from 0.50 to 2.09. In general, the EFs values calculated in this study were consistent or slightly less than the EFs reported for similar coastal seawater ecosystems. A correlation between the EFs of fluoranthene and pyrene indicated a positive significant value (R?=?0.9828, p?<?0.0001, n?=?6). Source analyses using the phenanthrene/anthracene and fluoranthene/pyrene ratios indicated the dominance of petrogenic-derived PAHs. Furthermore, enhanced concentrations of BaP (strong carcinogenicity) in SML and SSW samples, which resulted in higher EFs, could pose serious ecological and human health risks.