Increase of the purification efficiency of biofilters by the use of a complementary ionisation step

The biofilter and the ionisation system are two oxidative treatment techniques for purification of waste gas streams with low concentrations of volatile organic compounds. In this paper, the authors present the investigations of an ionisation technique aimed at increasing the efficiency of the reduction of the odorant concentration in waste gas streams from biological waste treatment plants. The objective is to enable advanced odour emission reduction and to adjust the existing biofilters to stricter requirements. In a first step, the odorous substances which are major contributors to the overall odorant concentration are identified on basis of various emission data sets with the help of a method of life cycle impact assessment. Thereby limonene, alpha-pinene, ethyl butyrate and dimethyl disulphide were identified as crucial indicators. In a second step, experimental investigations using limonene as a model compound were conducted to gain an understanding of the ionisation process itself and at last for the evaluation of the system.     

Clearance of PCDD/Fs via the gastrointestinal tract in occupationally exposed persons.

A digestive tract mass balance was performed on six men with high body burdens of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Intake via food was measured by analyzing duplicate portions of the food consumed by the volunteers and excretion via feces was determined by quantitative collection and analysis of the feces. Blood samples were taken to determine the current body burden. The results showed that the quantity of non-metabolized chemical excreted in the feces clearly exceeded the uptake via food for all of the 2,3,7,8-substituted PCDDs and some of the PCDFs, indicating a significant clearance across the gastrointestinal tract. The concentrations of these PCDD/F congeners in blood and feces were highly correlated (r > 0.8), demonstrating that the fecal PCDD/F content was determined by the body burden. The half lives in the test persons due to fecal clearance of non-metabolized chemical were estimated from the excretion rate and the current body burden and ranged between 10 years (Cl8DD) and 33 years (2,3,4,7,8-Cl5DF). These were compared with the overall contaminant half-lives due to all clearance processes which were calculated from the body burden and the decrease in blood concentrations measured over several years. The fecal clearance of non-metabolized PCDD/F contributed on average between 37% (2,3,7,8-Cl4DD) and 90% (Cl8DD) to the total elimination. This indicates that the gastrointestinal pathway plays a decisive role in the clearance of most 2,3,7,8-subsituted PCDD/F congeners.     

Fertiliser management effects on dissolved inorganic nitrogen in runoff from Australian sugarcane farms

Dissolved inorganic nitrogen (DIN) movement from Australian sugarcane farms is believed to be a major cause of crown-of-thorns starfish outbreaks which have reduced the Great Barrier Reef coral cover by ~21% (1985–2012). We develop a daily model of DIN concentration in runoff based on >200 field monitored runoff events. Runoff DIN concentrations were related to nitrogen fertiliser application rates and decreased after application with time and cumulative rainfall. Runoff after liquid fertiliser applications had higher initial DIN concentrations, though these concentrations diminished more rapidly in comparison to granular fertiliser applications. The model was validated using an independent field dataset and provided reasonable estimates of runoff DIN concentrations based on a number of modelling efficiency score results. The runoff DIN concentration model was combined with a water balance cropping model to investigate temporal aspects of sugarcane fertiliser management. Nitrogen fertiliser application in December (start of wet season) had the highest risk of DIN movement, and this was further exacerbated in years with a climate forecast for ‘wet’ seasonal conditions. The potential utility of a climate forecasting system to predict forthcoming wet months and hence DIN loss risk is demonstrated. Earlier fertiliser application or reducing fertiliser application rates in seasons with a wet climate forecast may markedly reduce runoff DIN loads; however, it is recommended that these findings be tested at a broader scale.     

Latitudinal differences in host-specificity of marine Monogenea and digenea

Data from 15 surveys of marine trematodes (average of 91 trematode species and more than 80 fish species per survey) and from 12 surveys of marine Monogenea (average of 52 Monogenea species and more than 49 fish species per survey) show that the degree of host specificity of marine digenetic trematodes increases from cold to warm seas; Monogenea do not show such a trend, and the trend is probably reversed in the Pacific Ocean. The difference between the two groups is explained in terms of r ^- and k ^- strategy. Monogenea tend to follow a k ^- strategy (great complexity of adult, few offspring), which results in a high degree of host- and sitespecificity to facilitate mating in low-density populations. Only one or a few related host species can be infected, and as more related host species are present in the warm Pacific, host-specificity there is reduced. Digenea tend to follow an r^- strategy (simple strucure of adult, many offspring), part of which is to infect many ecologically suitable hosts. Host-specificity in cold-temperate seas is reduced because of the less patchy and ecologically less restricted distribution of hosts.     

Bees’ subtle colour preferences: how bees respond to small changes in pigment concentration

Variability in flower colour of animal-pollinated plants is common and caused, inter alia, by inter-individual differences in pigment concentrations. If and how pollinators, especially bees, respond to these small differences in pigment concentration is not known, but it is likely that flower colour variability impacts the choice behaviour of all flower visitors that exhibit innate and learned colour preferences. In behavioural experiments, we simulated varying pigment concentrations and studied its impact on the colour choices of bumblebees and honeybees. Individual bees were trained to artificial flowers having a specific concentration of a pigment, i.e. Acridine Orange or Aniline Blue, and then given the simultaneous choice between three test colours including the training colour, one colour of lower and one colour of higher pigment concentration. For each pigment, two set-ups were provided, covering the range of low to middle and the range of middle to high pigment concentrations. Despite the small bee-subjective perceptual contrasts between the tested stimuli and regardless of training towards medium concentrations, bees preferred neither the training stimuli nor the stimuli offering the highest pigment concentration but more often chose those stimuli offering the highest spectral purity and the highest chromatic contrast against the background. Overall, this study suggests that bees choose an intermediate pigment concentration due to its optimal conspicuousness. It is concluded that the spontaneous preferences of bees for flower colours of high spectral purity might exert selective pressure on the evolution of floral colours and of flower pigmentation.