Evaluation of respiration in compost landfill biocovers intended for methane oxidation

A low-cost alternative approach to reduce landfill gas (LFG) emissions is to integrate compost into the landfill cover design in order to establish a biocover that is optimized for biological oxidation of methane (CH₄). A laboratory and field investigation was performed to quantify respiration in an experimental compost biocover in terms of oxygen (O₂) consumption and carbon dioxide (CO₂) production and emission rates. O₂ consumption and CO₂ production rates were measured in batch and column experiments containing compost sampled from a landfill biowindow at Fakse landfill in Denmark. Column gas concentration profiles were compared to field measurements. Column studies simulating compost respiration in the biowindow showed average CO₂ production and O₂ consumption rates of 107 ± 14 g m⁻² d⁻¹ and 63 ± 12 g m⁻² d⁻¹, respectively. Gas profiles from the columns showed elevated CO₂ concentrations throughout the compost layer, and CO₂ concentrations exceeded 20% at a depth of 40 cm below the surface of the biowindow. Overall, the results showed that respiration of compost material placed in biowindows might generate significant CO₂ emissions. In landfill compost covers, methanotrophs carrying out CH₄ oxidation will compete for O₂ with other aerobic microorganisms. If the compost is not mature, a significant portion of the O₂ diffusing into the compost layer will be consumed by non-methanotrophs, thereby limiting CH₄ oxidation. The results of this study however also suggest that the consumption of O₂ in the compost due to aerobic respiration might increase over time as a result of the accumulation of biomass in the compost after prolonged exposure to CH₄.     

TiO2/β-SiC foam-structured photoreactor for continuous wastewater treatment

Introduction

This study of photocatalytic degradation of wastewater was carried out in alveolar cell ??-SiC foam-structured photocatalytic reactors working in a recirculation mode. The immobilization of TiO2 on ??-SiC foams was efficiently obtained through a sol?Cgel technique in acidic conditions.

Discussion

In order to optimize degradation yields obtained by the foam-structured prototype reactor for the photocatalytic water treatment, the operating conditions of the photoreactor have been investigated and the efficiency of the process was evaluated by measuring the photocatalytic degradation of Diuron (3-(3,4-dichlorophenyl)-1,1-dimethyl-urea)) under UV irradiation. Kinetic studies were carried out by investigating the influence of different parameters controlling the reaction (TiO2 loading and ??-SiC foam cell size). The ageing of TiO2/??-SiC foam photocatalytic materials and the mineralization (TOC, Cl?, NO3? and NH4+) of Diuron were investigated.     

Predicting community sensitivity to ozone, using Ellenberg Indicator values

This paper develops a regression-based model for predicting changes in biomass of individual species exposed to ozone (RS(p)), based on their Ellenberg Indicator values. The equation (RS(p)=1.805-0.118Light-0.135 square root Salinity) underpredicts observed sensitivity but has the advantage of widespread applicability to almost 3000 European species. The model was applied to grassland communities to develop two further predictive tools. The first tool, percentage change in biomass (ORI%) was tested on data from a field-based ozone exposure experiment and predicted a 27% decrease in biomass over 5 years compared with an observed decrease of 23%. The second tool, an index of community sensitivity to ozone (CORI), was applied to 48 grassland communities and suggests that community sensitivity to ozone is primarily species-driven. A repeat-sampling routine showed that nine species were the minimum requirement to estimate CORI within 5%.     

Philopatry, male presence and grooming reciprocation among female primates: a comparative perspective

Competition for food and a safe location in a group are considered to be the main determinants of variation in social relationships among female primates. The effect of the presence of males is usually overlooked, however. Here we put forward two hypotheses connecting the (relative) number of males in a group, a statistic measuring the strength of positive relationships among females (the degree of reciprocity of grooming) and female residence. Under the first hypothesis, we assumed that philopatric females suffer especially from competition for males. Because females of these species are restrained to their native group and thus do not move to groups where better conditions (i.e. more males) prevail, a higher socionomic sex ratio would imply reduced competition and this should be reflected in better relationships among females (i.e. in a higher degree of reciprocation). The second hypothesis is based on the contention of Wrangham (1987) that groups with more males are better able to defend large food sources: in these groups female relationships would suffer less from within-group competition for food. We therefore also expected a positive correlation between the absolute number of males and grooming reciprocation. To test the hypotheses, matrices of grooming interactions were collected by going through the primatological literature. For ten female-resident and four female-transfer primate species, the degree of grooming reciprocation was quantified using a specially adapted matrix statistic. The results favoured the first (competition for males) hypothesis. The degree of grooming reciprocation among females was positively correlated with socionomic sex ratio, but neither with group size nor with the absolute number of males. Correlations between the degree of reciprocity and sex ratio were confirmed at three levels: within the same group at different points in time, between groups of the same species, and between species. In addition, the degree of reciprocation increased with sex ratio more strongly in typical single/variable male than in multi-male species. This we interpreted as a direct consequence of the lower social availability of males for females in multi-male groups than single-male groups. In turn, this effect may be due to males competing for females in multi-male groups. Received: 28 May 1997 / Accepted after revision: 9 November 1997     

Needs-based sewerage prioritization: alternative to conventional cost-benefit analysis

This paper presents an empirical approach to select and prioritize sewerage projects within set budgetary limitations. The methodology includes a model which quantifies benefits of a sewerage project as an index or dimensionless number. The index considers need and urgency of sewerage and other project goals. Benefit is defined as the difference in anticipated impact between the current condition (without the project) and the expected condition with the project. Anticipated benefits primarily include reduction in environmental pollution, reduction of human diseases and morbidity, and other tangible and intangible improvement. This approach is a powerful decision tool for sewerage prioritization and an effective alternative to conventional cost-benefit analysis. Unlike conventional analysis, this approach makes no attempt to convert project benefits and other impacts into a monetary measure. This work recognizes that the decision to provide sewerage based solely on net benefits is not practical. Instead, benefit-cost ratios (B/C) are calculated utilizing cost-effectiveness approach. Using these ratios, 16 unserviced areas of Ensenada, Mexico are ranked. The prioritization rankings produced by this method must be further scrutinized and carefully reviewed for logic, accuracy of input data, and practicality of implementation. A similar framework may also be useful for prioritizing other public works projects.     

A dual channel gas chromatograph for atmospheric analysis of volatile organic compounds including oxygenated and monoterpene compounds

A dual channel gas chromatograph with flame ionisation detectors has been used extensively for analysis of volatile organic compounds in the atmosphere and forms the basis of two monitoring instruments contributing VOC data to the World Meteorological Organisation - Global Atmosphere Watch network. Recent modifications to the methodology have broadened the scope of the instrument; to incorporate measurements of selected monoterpenes, and achieve improved accuracy in the measurement of oxygenated volatile organic compounds. Analysis of selected monoterpenes has been achieved without any significant loss of resolution of the non-methane hydrocarbons or oxygenated compounds. Quantification of 64 different VOCs of varying functionalities are reported with detection limits in the range 1-5 parts per trillion. Here we present a summary of the instrumental and calibration details for the methodology, which continues to be used on many field projects, along with a discussion of the associated measurement uncertainties.     

Does External Funding Help Adaptation? Evidence from Community-Based Water Management in the Colombian Andes

Despite debate regarding whether, and in what form, communities need external support for adaptation to environmental change, few studies have examined how external funding impacts adaptation decisions in rural resource-dependent communities. In this article, we use quantitative and qualitative methods to assess how different funding sources influence the initiative to adapt to water scarcity in the Colombian Andes. We compare efforts to adapt to water scarcity in 111 rural Andean communities with varied dependence on external funding for water management activities. Findings suggest that despite efforts to use their own internal resources, communities often need external support to finance adaptation strategies. However, not all external financial support positively impacts a community’s abilities to adapt. Results show the importance of community-driven requests for external support. In cases where external support was unsolicited, the results show a decline, or “crowding-out,” in community efforts to adapt. In contrast, in cases where communities initiated the request for external support to fund their own projects, findings show that external intervention is more likely to enhance or “crowds-in” community-driven adaptation.