Influence of kinetic sorption and diffusion on pesticide movement through aggregated soils

Laboratory studies were carried out to investigate solute leaching at different times from application in relation to temperature and initial soil moisture. Aggregates of a heavy clay soil were treated with a non-interactive solute (bromide) and the herbicides chlorotoluron, isoproturon and triasulfuron. The soil was incubated at 90% field capacity and either 5 or 15 degrees C. The influence of application to initially dry and initially wet aggregates on the behaviour of isoproturon was also investigated. At intervals, samples were either leached in small columns, centrifuged to characterise the fraction of chemical available in pore water under natural moisture conditions or extracted with organic solvents to assess total residues in soil. Bromide concentrations in leachate and in pore water extracted by centrifugation were constant with time. In contrast, availability for leaching and concentration in pore water of the herbicides decreased with increasing time from application in soil incubated at 15 degrees C. The effect of residence time was much smaller at 5 than at 15 degrees C. At the higher temperature, pesticide concentrations in leachate and pore water declined faster than would be expected from degradation alone, probably due to slow diffusion of the pesticides into soil aggregates where they are less available for leaching and/or slow sorption-desorption. The faster decline in availability for leaching at 15 than at 5 degrees C was attributed to faster degradation of the readily available fraction. There was no significant influence of initial soil moisture on either the leaching behaviour of isoproturon or its availability in soil water.     

Emissions of organophosphate and brominated flame retardants from selected consumer products and building materials

The emissions of selected flame retardants were measured in 1- and 0.02-m³ emission test chambers and 0.001-m³ emission test cells. Four product groups were of interest: insulating materials, assembly foam, upholstery/mattresses, and electronics equipment. The experiments were performed under constant environmental conditions (23°C, 50% RH) using a fixed sample surface area and controlled air flow rates. Tris (2-chloro-isopropyl)phosphate (TCPP) was observed to be one of the most commonly emitted organophosphate flame retardants in polyurethane foam applications. Depending on the sample type, area-specific emission rates (SER_a) of TCPP varied between 20 ng m⁻² h⁻¹ and 140 μg m⁻² h⁻¹.The emissions from electronic devices were measured at 60°C to simulate operating conditions. Under these conditions, unit specific emission rates (SER_u) of organophosphates were determined to be 10–85 ng unit⁻¹ h⁻¹. Increasing the temperature increased the emission of several flame retardants by up to a factor of 500. The results presented in this paper indicate that emissions of several brominated and organophosphate flame retardants are measurable. Polybrominated diphenylethers exhibited an SER_a of between 0.2 and 6.6 ng m⁻² h⁻¹ and an SER_u of between 0.6 and 14.2 ng unit⁻¹ h⁻¹. Because of sink effects, i.e., sorption to chamber components, the emission test chambers and cells used in this study have limited utility for substances low vapour pressures, especially the highly brominated compounds; hexabromocyclododecane had an SER_a of between 0.1 and 29 ng m⁻² h⁻¹ and decabromodiphenylether was not detectable at all.     

Genetic diagnosis by chorionic villus sampling before 8 gestational weeks: Efficiency,reliability, and risks on 317 completed pregnancies

Transabdominal chorionic villus sampling (TA-CVS) was attempted in 328 high-risk pregnancies at 6–7 weeks of gestation. Sampling was feasible in 97.7 per cent of cases; chorionic tissue specimens of more than 10 mg were obtained in 94.4 per cent ofcases at the first needle insertion and in 100 per cent after a second attempt. Fetal karyotyping succeeded in 99.4 per cent of cases, while no diagnostic failures were reported in enzymatic and DNA analyses. Fetal loss rate in the first 4 weeks after CVS was significantly higher than in the later CVS series (7.2 vs. 2.5 per cent), but 50 per cent of losses were observed within 2 weeks in cases of inviable aneuploidies. A high incidence of severe limb abnormalities (1.6 per cent) was detected in pregnancies intended to continue, confirming the aetiological role of early CVS. Unclear visualization of the placental limits and poor control of the needle path are thought to be the main reasons for the vascular disruption of the chorionic plate, and thereby hypoxic embryo tissue damage. A better selection of cases, together with high-resolution vaginal ultrasound visualization, and analytical techniques requiring a minimal amount of tissue should avoid any teratogenic effect of early CVS.     

Introducing urine-enriched biochar-based fertilizer for vegetable production: acceptability and results from rural Bangladesh

Improved agricultural practices that increase yields and preserve soils are critical to addressing food insecurity and undernutrition among smallholder farmer families. Urine-enriched biochar has been shown to be an accessible and effective fertilization option in various subtropical countries; however, it is new to Bangladesh. To better understand attitudes and experiences preparing and using urine-enriched biochar fertilizer, mixed-methods research was undertaken among smallholder farmers in northeastern Bangladesh in 2016/2017. In-depth interviews were conducted with 25 respondents who had compared the production of crops grown with biochar-based fertilizer to usual practice. In addition, in areas where trainings on biochar-based fertilization had been offered, 845 farmers were asked about their experience through a quantitative survey. Interview results indicated that cow urine-enriched biochar was favored over human urine because cow urine was perceived as clean and socially acceptable, whereas human urine was considered impure and disgusting. Respondents praised biochar-based fertilizer because it increased yields, cost little, was convenient to prepare with readily available natural materials, produced tastier crops, and allowed families to share their larger yields which in turn enhanced social and financial capital. Comparative field trials indicated a 60% yield benefit in both cabbage and kohlrabi crops. Challenges included uneven access to ingredients, with some respondents having difficulty procuring cow urine and biomass feedstock. The low social, health, and financial risk of adoption and the perceived benefits motivated farmers to produce and apply biochar-based fertilizer in their gardens, demonstrating strong potential for scale-up of this technology in Bangladesh.

     

Fight or flight? A geographic mosaic in host reaction and potency of a chemical weapon in the social parasite <Emphasis Type="Italic">Harpagoxenus sublaevis</Emphasis>

Ant social parasites use chemical warfare to facilitate host colony takeover, which is a critical but recurring step in their life cycle. Many slave-making ants use the secretion of the Dufour gland to manipulate host behaviour during parasitic nest foundation and slave raids. Harpagoxenus sublaevis applies this chemical weapon onto defending Leptothorax host workers, which elicits deadly fights amongst them. Host species are expected to evolve counter-adaptations against this behavioural manipulation and in this study we investigated the geographic structure of this co-evolving trait. We compared the effectiveness of the parasitic gland secretion from different H. sublaevis populations in host colonies from various sites and analysed the occurrence of local adaptation. The two host species L. muscorum and L. acervorum generally showed different responses to the parasites’ chemical weapon: L. acervorum attacked nestmates treated with Dufour gland secretion, while L. muscorum workers fled. Flight, instead of intraspecific fights, is an adaptive host reaction as it results in fewer host fatalities during raids. Beside interspecific host differences, we found a geographic mosaic of host resistance: parasites from a German population strongly manipulated the behaviour of both sympatric Leptothorax populations. Russian or Italian hosts instead did not react with intracolonial aggression, but fled when confronted with the gland secretion of their sympatric parasite. Not only variation in host resistance explains differences in the effectiveness of the parasitic gland secretion but also interpopulational differences in its chemical composition, which were revealed by gas chromatography and mass spectrometry.     

Evidence for declining levels of heavy-metals in the Severn Estuary and Bristol Channel, U.K. and their spatial distribution in sediments

Levels of heavy-metals (Cd, Cu, Cr, Ni, Pb and Zn) in suspended particulate and in surface and subsurface sediments were determined at seven locations in the Severn Estuary and Bristol Channel. Sediment metal concentrations were highest at sites close to industrial centres but levels have decreased significantly over the last 30 years so that they are now close to, or meet, environmental quality guidelines. The greatest metal concentrations in deposited sediments were usually associated with the finest particulates at locations with muddy sediments, but this was not always true at sites with predominantly sandy sediments. The metals bound to suspended particulates at all sites were remarkably consistent, presumably reflecting the mixing capacity of this macro-tidal estuary. The re-exposure of older, more contaminated sediments could explain the observed differences between deposited and suspended material. Sediment redistribution due to strong seasonal currents might also explain the differences between winter and summer samples.