Substrate Temperature Constrains Recruitment and Trail Following Behavior in Ants

In many ant species, foragers use pheromones to communicate the location of resources to nestmates. Mass-recruiting species deposit long-lasting anonymous chemical trails, while group-recruiting species use temporary chemical trails. We studied how high temperature influenced the foraging behavior of a mass-recruiting species (Tapinoma nigerrimum) and a group-recruiting species (Aphaenogaster senilis) through pheromone decay. First, under controlled laboratory conditions, we examined the effect of temperature on the trail pheromone of both species. A substrate, simulating soil, marked with gaster extract was heated for 10 min. at 25°, 35°, 45°, or 55 °C and offered to workers in a choice test. Heating gaster extract reduced the trail following behavior of the mass-recruiters significantly more than that of the group-recruiters. Second, analyses of the chemicals present on the substrate indicated that most T. nigerrimum gaster secretions vanished at 25 °C, and only iridodials persisted up to 55 °C. By contrast, A. senilis secretions were less volatile and resisted better to elevated temperatures to some extent. However, at 55 °C, the only chemicals that persisted were nonadecene and nonadecane. Overall, our results suggest that the foraging behavior of the group-recruiting species A. senilis is less affected by pheromone evaporation than that of the mass-recruiting species T. nigerrimum. This group-recruiting species might, thus, be particularly adapted to environments with fluctuating temperatures.     

An investigation into the inputs controlling predictions from a diffuse phosphorus loss model for the UK; the Phosphorus Indicators Tool (PIT)

A simple catchment scale model simulating diffuse phosphorus (P) loss from agricultural land to water, the Phosphorus Indicators Tool (PIT), has been developed. Previous research has shown that this model worked well in simulating the average annual P lost from two catchments: Windermere and Windrush, but it was not known which drivers in the model had the greatest control on predicted P delivery to water from agricultural land. In order to simulate the P export from each catchment source via each hydrological pathway specified individually, 108 coefficients are used in the model code. A univariate sensitivity analysis was conducted to evaluate which coefficient exerted the greatest control on the model output. Results from the univariate analysis suggest that the model is sensitive to a number of coefficients, but importantly, not all of the coefficients that were varied in the sensitivity analysis, altered the model output. The PIT model has been calibrated by optimizing results from the univariate analysis against observed data in the Windermere catchment. The simulated results from model calibration fit the observed data well, at the 95% level. This paper describes the methodology developed for the univariate analysis and evaluates the model calibration procedure against observed data from the Windermere catchment.     

Evaluation of oxygen injection as a means of controlling sulfide production in a sewer system

Oxygen injection is often used to control biogenic production of hydrogen sulfide in sewers. Experiments were carried out on a laboratory system mimicking a rising main to investigate the impact of oxygen injection on anaerobic sewer biofilm activities. Oxygen injection (15-25 mg O₂/L per pump event) to the inlet of the system decreased the overall sulfide discharge levels by 65%. Oxygen was an effective chemical and biological oxidant of sulfide but did not cause a cessation in sulfide production, which continued in the deeper layers of the biofilm irrespective of the oxygen concentration in the bulk. Sulfide accumulation resumed instantaneously on depletion of the oxygen. Oxygen did not exhibit any toxic effect on sulfate reducing bacteria (SRB) in the biofilm. It further stimulated SRB growth and increased SRB activity in downstream biofilms due to increased availability of sulfate at these locations as the result of oxic conditions upstream. The oxygen uptake rate of the system increased with repeated exposure to oxygen, with concomitant consumption of organic carbon in the wastewater. These results suggest that optimization of oxygen injection is necessary for maximum effectiveness in controlling sulfide concentrations in sewers.     

Deacidification of Soybean Oil Using Membrane Processing and Subcritical Carbon Dioxide

Vegetable oils have been deacidified using supercritical carbon dioxide and membrane processing. However, the pressures required are substantially greater than those used in industry. Therefore, the feasibility of using subcritical carbon dioxide (at much lower pressures) and membrane processing to separate free fatty acids (FFA) from triacylglycerols (TAGs) was examined. First, FFA/TAG solubility tests were completed (10–25 °C and 68–136 atm). The oil samples were separated using a FilmTec NF90 or a FilmTec BW30 membrane in a dead-end type cell. Within the range examined, the greatest solubility for oleic acid was at 25 °C and 136 atm. For soybean oil TAGs, the greatest solubility was at 20 °C and 136 atm. However, for the separation of the two components, 20 °C and 68 atm was best among the condition combinations examined. The solubility of oleic acid ranged from 0.294 to 0.455 mg/mL in subcritical carbon dioxide, while the solubility of triacylglycerols ranged from 0.066 to 0.139 mg/mL. The FilmTec BW30 membrane provided significantly better separation of FFAs from TAGs than did the NF90 membrane. Both membranes were selective for oleic acid, although the BW30 had greater selectivity for oleic acid (β _{oleic acid} = 2.12, β _TAGs = 0.24) than the NF90 membrane (β _{oleic acid} = 1.26, β _TAGs = 0.81).     

A kinetic model for ammonia selective catalytic reduction over Cu-ZSM-5

Kinetic modeling, in combination with flow reactor experiments, was used in this study for simulating NH₃ selective catalytic reduction (SCR) of NO_x over Cu-ZSM-5. First the mass-transfer in the wash-coat was examined experimentally, by using two monoliths: one with 11 wt.% wash-coat and the other sample with 23 wt.% wash-coat. When the ratio between the total flow rate and the wash-coat amount was kept constant similar results for NO_x conversion and NH₃ slip were obtained, indicating no significant mass-transfer limitations in the wash-coat layer. A broad range of experimental conditions was used when developing the model: ammonia temperature programmed desorption (TPD), NH₃ oxidation, NO oxidation, and NH₃ SCR experiments with different NO-to-NO₂ ratios. 5% water was used in all experiments, since water affects the amount of ammonia stored and also the activity of the catalyst. The kinetic model contains seven reaction steps including these for: ammonia adsorption and desorption, NH₃ oxidation, NO oxidation, standard SCR (NO + O₂ + NH₃), rapid SCR (NO + NO₂ + NH₃), NO₂ SCR (NO₂ + NH₃) and N₂O formation. The model describes all experiments well. The kinetic parameters and 95% linearized confidence regions are given in the paper. The model was validated with six experiments not included in the kinetic parameter estimation. The ammonia concentration was varied from 200 up to 800 ppm using NO only as a NO_x source in the first experiment and 50% NO and 50% NO₂ in the second experiment. The model was also validated with transient experiments at 175 and 350 °C where the NO and NH₃ concentrations were varied stepwise with a duration of 2 min for each step. In addition, two short transient experiments were simulated where the NO₂ and NO levels as well as NO₂-to-NO_x ratio were varied. The model could describe all validation experiments very well.     

High-resolution measurement of pore saturation and colloid removal efficiency in quartz sand using fluorescence imaging

Colloid deposition in unsaturated, nonuniform porous media is poorly explained by current models and difficult to measure using breakthrough curves and retained mass profiles. We present new methods which enable time-lapse fluorescence imaging to quantify variations in pore saturation, theta, and colloid deposition in 2D, nonuniform unsaturated flow fields. Calibration experiments revealed direct proportionality between fluorescence F and theta in 20/30 mesh quartz sand. Analysis of breakthrough data in fluorescence images allows quantification of the mean mobile concentration, mean deposition rate, and hence the colloid removal efficiency eta directly from data at the pixel-scale throughoutthe flow field. We imaged carboxylate-modified latex microspheres from a point source in saturated flow and unsaturated flow across a capillary fringe at 10(-3), 10(-2), and 10(-1) M NaCl. Total numbers of colloids deposited and values of eta increased with ionic strength. We modeled the observed variations in eta with theta to estimate the partitioning of colloid deposition between air-water and solid-water interfaces. In the broad saturation range 0.2 < theta < 1, our results suggest that only at the lowest ionic strength, where deposition at solid-water interfaces was strongly unfavorable, did colloid deposition associated with air-water interfaces significantly influence the total colloid removal.     

Texture and distribution of pectic substances of mango as affected by infusion of pectinmethylesterase and calcium

Fresh cut mangos were infused with pectinesterase (PME) and calcium chloride, and the effect on textural properties, distribution of pectic substance and degree of esterification was determined. Temperature gradient infusion with PME and/or calcium chloride increased gumminess and chewiness, but had no impact on hardness and adhesiveness. The distribution of pectic substances, as protopectin or alkaline soluble pectin, was approximately twice that of water‐ or chelator‐soluble pectin. The degree of esterification of water‐ and chelator‐soluble pectic substances was near 50–60%, and less than 10%, respectively. Heat‐sensitive PME inhibitor in mango was detected. The initial hardness of Kent mango was variable, and differences in distribution of pectic substances were observed. Texture of Kent mango is most likely moderated by changes in the solubility of insoluble pectin or by non‐pectin components in the cell wall. Copyright © 2004 Society of Chemical Industry     

Prevalence of Salmonella in grade A whole shell eggs in the island of Ireland

Following the emergence of Salmonella Enteritidis as a widespread contaminant of eggs and the role of eggs in the transmission of human salmonellosis, control measures were introduced to curb the spread of infection. Two approaches to Salmonella control are currently used by egg producers in Ireland, because Northern Ireland producers, like those in the rest of the United Kingdom, widely adopted a vaccination regime, whereas the Republic of Ireland does not permit vaccination but introduced controls based on routine monitoring for specific Salmonella serovars and subsequent culling of infected flocks. To compare the efficacy of these two approaches and determine the prevalence of salmonellae in eggs produced for retail sale in the island of Ireland, a major survey of approximately 30,000 grade A eggs was undertaken. Egg shells and contents were analyzed separately for salmonellae by procedures based on International Organization for Standardization methodology. The survey yielded only two positive samples, with Salmonella Infantis and Salmonella Montevideo isolated from shells; no egg contents yielded salmonellae. There was no statistically significant difference in the prevalence of salmonellae between eggs produced in Northern Ireland and those from the Republic of Ireland; hence, both regimes appeared to be equally effective in controlling salmonellae. The prevalence was also significantly lower than that found in a recent major United Kingdom survey. Hence, shell eggs produced in the island of Ireland are unlikely to be a source of human salmonellosis.     

Quantum dot transport in soil, plants, and insects

Environmental risk assessment of nanomaterials requires information not only on their toxicity to non-target organisms, but also on their potential exposure pathways. Here we report on the transport and fate of quantum dots (QDs) in the total environment: from soils, through their uptake into plants, to their passage through insects following ingestion. Our QDs are nanoparticles with an average particle size of 6.5 nm. Breakthrough curves obtained with CdTe/mercaptopropionic acid QDs applied to columns of top soil from a New Zealand organic apple orchard, a Hastings silt loam, showed there to be preferential flow through the soil's macropores. Yet the effluent recovery of QDs was just 60%, even after several pore volumes, indicating that about 40% of the influent QDs were filtered and retained by the soil column via some unknown exchange/adsorption/sequestration mechanism. Glycine-, mercaptosuccinic acid-, cysteine-, and amine-conjugated CdSe/ZnS QDs were visibly transported to a limited extent in the vasculature of ryegrass (Lolium perenne), onion (Allium cepa) and chrysanthemum (Chrysanthemum sp.) plants when cut stems were placed in aqueous QD solutions. However, they were not seen to be taken up at all by rooted whole plants of ryegrass, onion, or Arabidopsis thaliana placed in these solutions. Leafroller (Lepidoptera: Tortricidae) larvae fed with these QDs for two or four days, showed fluorescence along the entire gut, in their frass (larval feces), and, at a lower intensity, in their haemolymph. Fluorescent QDs were also observed and elevated cadmium levels detected inside the bodies of adult moths that had been fed QDs as larvae. These results suggest that exposure scenarios for QDs in the total environment could be quite complex and variable in each environmental domain.     

Effect of particle size on arsenic bioaccessibility in gold mine tailings of Nova Scotia

Tailings samples from the Goldenville and Montague abandoned gold mines in Nova Scotia, Canada were subjected to bioaccessibility tests to examine the effects of the choice of particle size fraction on the bioaccessibility of arsenic. The proportion of finer grains (< 150 μm) in this sample set varied from 6.0 to 66 wt.%. Samples were sieved to < 250, < 150, and < 45 μm particle size fractions. The arsenic bioaccessibility ranged from less than 1.0 to 48%, but no systematic variation was observed (p > 0.13) precluding the association of greater percent arsenic bioaccessibility with a specific particle size fraction, method or site. On the other hand, the highest bioaccessible arsenic concentrations (up to 5200 mg kg^− 1) were consistently observed in samples sieved to the < 45 μm particle size, for both the physiologically based extraction test and a glycine-buffered bioaccessibility method (in 89 and 87% of samples tested, respectively). This was due to higher total arsenic concentrations in the same particle size fraction. Grain maps obtained by X-ray absorption spectroscopy indicate that samples with the highest percent arsenic bioaccessibility contain amorphous pentavalent arsenic distributed throughout the sample as well as grains coated with pentavalent arsenic. Arsenic bioaccessibilities lower than 10% were found in samples with encapsulated arsenopyrite and some grains composed primarily of pentavalent arsenic. The < 45 μm particle size fraction appears to yield conservative (protective) estimates of the bioaccessible dose of arsenic, but wide variations exist in particle size distribution and arsenic bioaccessibility between samples. As well, sieving to < 45 μm may exclude potentially relevant particles by restricting the study to an average particle size that is smaller than the average size of particles found on human hands, and may unduly influence the resulting bioaccessibility measurements.