Development of numerical model for predicting heat generation and temperatures in MSW landfills

A numerical modeling approach has been developed for predicting temperatures in municipal solid waste landfills. Model formulation and details of boundary conditions are described. Model performance was evaluated using field data from a landfill in Michigan, USA. The numerical approach was based on finite element analysis incorporating transient conductive heat transfer. Heat generation functions representing decomposition of wastes were empirically developed and incorporated to the formulation. Thermal properties of materials were determined using experimental testing, field observations, and data reported in literature. The boundary conditions consisted of seasonal temperature cycles at the ground surface and constant temperatures at the far-field boundary. Heat generation functions were developed sequentially using varying degrees of conceptual complexity in modeling. First a step-function was developed to represent initial (aerobic) and residual (anaerobic) conditions. Second, an exponential growth-decay function was established. Third, the function was scaled for temperature dependency. Finally, an energy-expended function was developed to simulate heat generation with waste age as a function of temperature. Results are presented and compared to field data for the temperature-dependent growth-decay functions. The formulations developed can be used for prediction of temperatures within various components of landfill systems (liner, waste mass, cover, and surrounding subgrade), determination of frost depths, and determination of heat gain due to decomposition of wastes.     

Clustering species using a model of population dynamics and aggregation theory

The high species diversity of some ecosystems like tropical rainforests goes in pair with the scarcity of data for most species. This hinders the development of models that require enough data for fitting. The solution commonly adopted by modellers consists in grouping species to form more sizeable data sets. Classical methods for grouping species such as hierarchical cluster analysis do not take account of the variability of the species characteristics used for clustering. In this study a clustering method based on aggregation theory is presented. It takes account of the variability of species characteristics by searching for the grouping that minimizes the quadratic error (square bias plus variance) of some model’s prediction. This method allows one to check whether the gain in variance brought by data pooling compensate for the bias that it introduces. This method was applied to a data set on 94 tree species in a tropical rainforest in French Guiana, using a Usher matrix model to predict species dynamics. An optimal trade-off between bias and variance was found when grouping species. Grouping species appeared to decrease the quadratic error, except when the number of groups was very small. This clustering method yielded species groups similar to those of the hierarchical cluster analysis using Ward’s method when variance was small, that is when the number of groups was small.     

Spatial distribution of lindane in topsoil of Northern France

Lindane is a persistent organochlorine insecticide and the use of this insecticide in agriculture was banned in France in 1998. In this study we investigated the concentrations of lindane in topsoil in Northern France and used robust geostatistics to map the geographical distribution of lindane. The study was based on a 16 km × 16 km grid covering an area of ca 25 000 km². Lindane was found in all soils, even those from non-agricultural-application areas. Very low ratios of α-/γ-HCH and δ-/γ-HCH suggested that a long time had passed since technical HCH was used in the studied area, or that emission sources of lindane were still present. A strong gradient in lindane concentration was observed, with the highest lindane concentrations in an area located in the northern region. Results suggested that some of the lindane observed in the high concentration area may have come from volatilization of old lindane applied to intensively cultivated areas, which was then transported by prevailing winds coming from the south-west and deposited in a densely inhabited depression.     

Growing season methane budget of an Inner Mongolian steppe

We present a methane (CH₄) budget for the area of the Baiyinxile Livestock Farm, which comprises approximately 1/3 of the Xilin river catchment in central Inner Mongolia, P.R. China. The budget calculations comprise the contributions of natural sources and sinks as well as sources related to the main land-use in this region (non-nomadic pastoralism) during the growing season (May–September). We identified as important CH₄ sources floodplains (mean 1.55 ± 0.97 mg CH₄–C m^?2 h^?1) and domestic ruminants, which are mainly sheep in this area. Within the floodplain significant differences between investigated positions were detected, whereby only positions close-by the river or bayous emitted large amounts of CH₄ (mean up to 6.21 ± 1.83 mg CH₄–C m^?2 h^?1). Further CH₄ sources were sheepfolds (0.08–0.91 mg CH₄–C m^?2 h^?1) and pasture faeces (1.34 ± 0.22 mg CH₄–C g^?1 faeces dry weight), but they did not play a significant role for the CH₄ budget. In contrast, dung heaps were not a net source of CH₄ (0.0 ± 0.2 for an old and 0.0 ± 0.3 μg CH₄–C kg^?1 h^?1 for a new dung heap). Trace gas measurements along two landscape transects (volcano, hill slope) revealed expectedly a mean CH₄ uptake (volcano: 76.5 ± 4.3; hill: 28.3 ± 5.3 μg CH₄–C m^?2 h^?1), which is typical for the aerobic soils in this and other steppe ecosystems. The observed fluxes were rarely influenced by topography.The CH₄ emissions from the floodplain and the sheep were not compensated by the CH₄ oxidation of aerobic steppe soils and thus, this managed semi-arid grassland did not serve as a terrestrial sink, but as a source for this globally important greenhouse gas. The source strength amounted to 1.5–3.6 kg CH₄–C ha^?1 during the growing season, corresponding to 3.5–8.7 kg C ha^?1 yr^?1.     

Stress and recovery assessment during simulated microgravity: Effects of exercise during a long-term head-down tilt bed rest in women

The aim of this study was to determine the effects of a 60-day head-down tilt long-term bed rest (HDT) on stress and recovery in sixteen healthy female volunteers. Participants were randomly assigned to either an exercise group (Exe) that followed a training program combining resistive and aerobic exercises, or to a no-exercise control group (Ctl). Psychological states were assessed using the Rest-Q, a validated questionnaire based on stress–recovery responses. A longitudinal analysis revealed significant changes in the general and specific-stress scales for all participants throughout the experiment with a critical stage from supine to standing posture leading to a significant decrease in physical recovery. During HDT, Exe reported higher scores on stress subscales, as well as lower recovery scores compared to the Ctl. During the post-HDT ambulatory recovery period, the exercisers still reported higher scores than the non-exercisers on the Lack of energy stress-related scale, along with lower scores in general well-being and personal accomplishment. The present findings show that simulated weightlessness such as HDT may induce psychological stress and lead to subsequent alterations in perceived recovery. Exercise did not reduce HDT impaired effects on stress and recovery states. Several suggestions, including psychological preparation, are proposed to support the beneficial effects of exercise on psychological factors.     

Relationship between occupational social class and exposure to organochlorine pesticides during pregnancy

Background

Little evidence is available on the influence of socioeconomic factors on exposure to persistent organic pollutants, especially during vulnerable periods such as pregnancy and early life.

Objective

To investigate the relationship of maternal social class with placental concentrations of organochlorine pesticides (OCPs) and their combined estrogenic activity measured with a biomarker of exposure.

Methods

Exposure to 16 OCPs (DDTs, endosulfans, and seven other compounds) and the total effective xenoestrogenic burden (TEXB) were analyzed in placentas from a mother-child cohort. OCP concentrations were quantified by gas chromatography and mass spectrometry, and TEXB was assessed with the E-Screen bioassay. Social class was classified according to maternal occupation. Multivariate regression analysis was conducted to examine variations in pesticide exposure and TEXB as a function of maternal social class in 257 subjects.

Results

Placental p,p′-DDT concentrations were higher in social classes III and IV than in classes I-II (the most affluent); concentrations of the sum of DDTs were higher in class IV; and exposure to the sum of endosulfans was greater in class III. HCB concentrations were higher among women in class IV than in classes I-II and among manual (classes III-V) than non-manual workers. However, the trend across social classes was only statistically significant for HCB. Social class significantly explained 10% of the variability in concentrations of the sum of endosulfans.

Conclusion

There is a need to explore whether more disadvantaged populations suffer higher levels of exposure to pesticides or other environmental chemicals and how different social processes contribute to this exposure.     

Characterization and dispersion modeling of odors from a piggery facility

Piggeries are known for their nuisance odors, creating problems for workers and nearby residents. Chemical substances that contribute to these odors include sulfurous organic compounds, hydrogen sulfide, phenols and indoles, ammonia, volatile amines, and volatile fatty acids. In this work, daily mean concentrations of ammonia (NH3) and hydrogen sulfide (H2S) were measured by hand-held devices. Measurements were taken in several places within the facility (farrowing to finishing rooms). Hydrogen sulfide concentration was found to be 40 to 50 times higher than the human odor threshold value in the nursery and fattening room, resulting in strong nuisance odors. Ammonia concentrations ranged from 2 to 18 mL m(-3) and also contributed to the total odor nuisance. Emission data from various chambers of the pig farm were used with the dispersion model AERMOD to determine the odor nuisance caused due to the presence of H2S and NH3 to receptors at various distances from the facility. Because just a few seconds of exposure can cause an odor nuisance, a "peak-to-mean" ratio was used to predict the maximum odor concentrations. Several scenarios were examined using the modified AERMOD program, taking into account the complex terrain around the pig farm.     

Measurement of mass exchange processes and coefficients in a simplified open-channel lateral cavity connected to a main stream

Lateral cavities are major storage zones in riverine environments for which the mass exchanges with the main stream strongly impact the characteristics of the habitat in these dead zones. An experimental work is presented here with a controlled main stream and a connected open-channel lateral cavity to assess the processes responsible for these exchanges and to quantify the exchange capacities. In a first step, the measurements of passive scalar transport allow us to identify the physical processes involved in the exchange of mass from the main stream and its spreading within the cavity. In a second step, the quantitative mass exchange coefficient, representative of the exchange capacity, is measured for 28 flow and cavity configurations. The sensibility analysis to the governing parameters proposed by the dimensional analysis then reveals that changing the geometric aspect ratio of the cavity does not affect the exchange coefficient while increasing the normalized water depth or decreasing the Reynolds number of the main stream tend to increase this coefficient. Indeed, these parameters modify both the growth rate of the mixing layer width at the interface and the amplitude of the alternating transverse velocity across the interface, thus affecting the exchange capacities from the main stream to the cavity.     

The sweet smell of… courtship: Effects of pleasant ambient fragrance on women's receptivity to a man's courtship request

Studies have shown that pleasant scents favor positive social relationships. However, the effect of pleasant ambient odor on romantic relationships has never been tested. In a field experiment, 18–25 year old women walking alone in a shopping mall were approached by an attractive 20 year old male-confederate who solicited them for their phone number. The women were solicited as they were walking in areas with pleasant ambient odors (e.g., pastries) or with no odor. It was found that women agreed more often to the confederate's courtship solicitation in the pleasant smelling areas. Positive mood induced by ambient odors may explain such results.     

Using organic-certified rather than synthetic pesticides may not be safer for biological control agents: selectivity and side effects of 14 pesticides on the predator Orius laevigatus

The generalist predator Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) is a key natural enemy of various arthropods in agricultural and natural ecosystems. Releases of this predator are frequently carried out, and it is included in the Integrated Pest Management (IPM) programs of several crops. The accurate assessment of the compatibility of various pesticides with predator activity is key for the success of this strategy. We assessed acute and sublethal toxicity of 14 pesticides on O. laevigatus adults under laboratory conditions. Pesticides commonly used in either conventional or organic farming were selected for the study, including six biopesticides, three synthetic insecticides, two sulfur compounds and three adjuvants. To assess the pesticides’ residual persistence, the predator was exposed for 3 d to pesticide residues on tomato sprouts that had been treated 1 h, 7 d or 14 d prior to the assay. The percentage of mortality and the sublethal effects on predator reproductive capacity were summarized in a reduction coefficient (E_x) and the pesticides were classified according to the IOBC (International Organization for Biological Control) toxicity categories. The results showed that the pesticides greatly differed in their toxicity, both in terms of lethal and sub lethal effects, as well as in their persistence. In particular, abamectin was the most noxious and persistent, and was classified as harmful up to 14 d after the treatment, causing almost 100% mortality. Spinosad, emamectin, metaflumizone were moderately harmful until 7 d after the treatment, while the other pesticides were slightly harmful or harmless. The results, based on the combination of assessment of acute mortality, predator reproductive capacity pesticides residual and pesticides residual persistence, stress the need of using complementary bioassays (e.g. assessment of lethal and sublethal effects) to carefully select the pesticides to be used in IPM programs and appropriately time the pesticides application (as function of natural enemies present in crops) and potential releases of natural enemies like O. laevigatus.