Mineral aerosols from western India: Temporal variability of coarse and fine atmospheric dust and elemental characteristics

Size-segregated aerosol samples (PM_2.5 and PM₁₀) were collected during Jan–Dec-2007 from a high-altitude site located in a semi-arid region (Mt. Abu, 24.6 °N, 72.7 °E, 1680 m asl) in order to asses the temporal variability in the abundance of atmospheric mineral dust and its elemental composition over western India. The mass concentrations of fine (PM_2.5) and coarse (PM_10–2.5) mode aerosols varied from 1.6 to 46.1 and 2.3 to 102 μg m^?3 respectively over the annual seasonal cycle; with dominant and uniform contribution of mineral dust (60–80%) in the coarse mode relative to large temporal variability (11–75%) observed in the fine mode. The coarse mass fraction shows a characteristic increase with the wind speed during summer months (Mar to Jun); whereas fine aerosol mass and its elemental composition exhibit conspicuous temporal pattern associated with north-easterlies during wintertime (Oct–Feb). The Fe/Al weight ratio in PM_2.5 ranges from 0.5 to 1.0 during winter months. The relative enrichment of Fe in fine mode, compared to the crustal ratio of 0.44, is attributed to the down-wind advective transport of combustion products derived from large-scale biomass burning, industrial and automobile emission sources located in the Indo-Gangetic Plain (northern India). In contrast, Ca/Al and Mg/Al weight ratios show relative enrichment of Ca and Mg in the coarse mode; indicating their dominant contribution from carbonate minerals. This has implication to efficient neutralization of atmospheric acidic species (SO₄^2? and NO₃^?) by mineral dust over western India.     

Experimental simulation of airbag deployment for pipeline closing

Small scale tests were carried out at ISL's shock tube facility STA (100 mm inner diameter) to study the problem of closing a pipeline by means of an airbag in case of explosions or gas leakages. Experiments were carried out to simulate the flow in a pipeline at velocities and gas pressures as present in pipeline flows. In this study the gas used was nitrogen at static pressures of 0.2 up to 5 MPa and at flow velocities of 25 m/s up to 170 m/s. A special Nylon airbag, deployed from the tube wall into the pipe, was used to simulate the airbag inflation in a real pipeline. For this purpose a special gas filling system consisting of a gas generator with a reservoir volume of up to 500 cm³ which permits air pressures up to 17 MPa to be generated inside the airbag was developed at ISL. With a fast pyrotechnically opened valve the reservoir gas was released for airbag filling. The airbag inflation was triggered in such a way that it opened in nearly 3 ms into the pipe flow generated by the shock tube and continued for about 10 ms. For this application a special measuring chamber was designed and constructed with 20 measuring ports. Through two window ports, located one in front of the other, the airbag inflation could be visualized with up to 50 successive flash sparks illuminating a fast rotating film inside a drum camera. Pressure measurements using commercially available PCB pressure gauges at 9 measuring ports placed along the inner tube surface gave some hints on the behaviour of the wall pressure during airbag deployment. As a result from the experiments performed it is to conclude, that, with the Nylon airbag samples available, the pipe flow cannot be blocked by the inflating airbag. The flow forces acting on the airbag during deployment are in the shock tube experiments of the order of about 1000 N, which are not balanced by the airbags' neck, fixing it to the shock tube wall. This outcome suggests that a mechanical support is required to fix the airbag in its place during inflation.     

Changes in earth’s dipole

The dipole moment of Earth’s magnetic field has decreased by nearly over the past 150 years and by about 30% over the past 2,000 years according to archeomagnetic measurements. Here, we explore the causes and the implications of this rapid change. Maps of the geomagnetic field on the core–mantle boundary derived from ground-based and satellite measurements reveal that most of the present episode of dipole moment decrease originates in the southern hemisphere. Weakening and equatorward advection of normal polarity magnetic field by the core flow, combined with proliferation and growth of regions where the magnetic polarity is reversed, are reducing the dipole moment on the core–mantle boundary. Growth of these reversed flux regions has occurred over the past century or longer and is associated with the expansion of the South Atlantic Anomaly, a low-intensity region in the geomagnetic field that presents a radiation hazard at satellite altitudes. We address the speculation that the present episode of dipole moment decrease is a precursor to the next geomagnetic polarity reversal. The paleomagnetic record contains a broad spectrum of dipole moment fluctuations with polarity reversals typically occurring during dipole moment lows. However, the dipole moment is stronger today than its long time average, indicating that polarity reversal is not likely unless the current episode of moment decrease continues for a thousand years or more.     

An empirical method for the conversion of spectral UV irradiance measurements to actinic flux data

Routinely monitored radiation parameters, including those at UV wavelengths, most commonly refer to irradiance, that is the radiation incident on a flat horizontal plate. However, in the study of atmospheric chemistry, where UV radiation is a prime photochemical driver, the target molecules are approximately spherical and the actinic flux (radiation on the surface of a sphere) is a better measure of the effective radiation. Unfortunately actinic flux measurements (also known as scalar irradiance) are uncommon research measurements. The ability to convert irradiance data to actinic flux data within a reasonable degree of uncertainty would provide an actinic flux database mapped from existing irradiance databases, thus vastly increasing knowledge of actinic flux variability and climatology. Synchronised spectral UV irradiance and actinic flux measurements have been made during the ADMIRA project, and used to develop an empirical method for converting irradiance to actinic flux. With some prior knowledge of the sky conditions during the irradiance measurements the actinic flux can be estimated to within a few percent. If no knowledge of the sky conditions is available then the empirical method still returns actinic fluxes within 10% of those measured at the site for which the conversion was developed.     

Social impacts of earthquakes caused by gas extraction in the Province of Groningen,The Netherlands

Gas extraction from the Groningen gasfield in the northern Netherlands has led to localised earthquakes which are projected to become more severe. The social impacts experienced by local residents include: damage to property; declining house prices; concerns about the chance of dykes breaking; feelings of anxiety and insecurity; health issues; and anger. These social and emotional impacts are exacerbated by the increasing distrust Groningen people have towards the national government and the gas company, NAM, a partnership between Shell and ExxonMobil. The earthquakes have reopened discussions about the distribution of benefits from gas production and the extent to which benefits are retained locally. Mitigation of the impacts is attempted, but the lack of trust decreases the effectiveness of the mitigation measures. The extent of this experience of previously-unforeseen, unanticipated impacts suggests that a new social and environmental impact assessment needs to be undertaken, and a new Social Impact Management Plan (SIMP) and Impacts and Benefits Agreement (IBA) developed, so that the project can regain its legitimacy and social licence to operate. In addition to conventional gas, this paper has wider relevance for unconventional gas developments, for example shale gas extraction by hydraulic fracturing methods (fracking).     

An Avoidable Tragedy at the Sea Cliff (Rincon) Oil Field

Three men were killed and four others were injured during a well drill operation on Hobson Well C-10A in the Sea Cliff Oil Field (also known as Rincon Oil Field), in Ventura County, California, United States, on August 10, 1994, as a result of errors made by the work supervisors at the site. The oil field was under management by Vintage Petroleum, Ltd., which was sued for negligence by the families of the deceased and injured. The coroner's autopsy examination concluded that the cause of the deaths was due to the inhalation of the toxic gas carbon monoxide (CO). This gas was assumed to have been released from the firing of high-energy guns (HEGs) using carbon-rich explosive pentaerythritol tetranitrate (PETN) in an oxygen-depleted environment, during a fracking operation by Schlumberger Corporation on Well C-10A. The author of this article was appointed as an expert witness by Schlumberger to evaluate if the coroner's conclusion was correct. A series of chemical analytical analyses were conducted on the vapor phase of samples, in addition to dissolved components in water from Well C-10A and two adjacent wells. Stable isotope analyses were also conducted on hydrogen (H₂), methane (CH₄), nitrogen (N₂), CO, and water (H₂O) 3 weeks after the accident, as well as on four additional occasions from September to December 1994. Control test analyses were performed on the products from HEG firings, using the same explosives as those used in the perforation of Well C-10A in control chambers at a Schlumberger facility in Houston, Texas. The conclusion reached was that the dominant products of PETN detonations are H₂, CH₄, CO, and N₂. However, the isotope ratios (D/H and ¹³C/¹²C) of methane in the control experiments were different in Well C-10A, following the detonation on August 10, 1994, than those resulting from controlled PETN explosions. The conclusion reached in this study was that the fracking of the well at a depth of around 2,150 ft had increased the permeability of the sediment layers in the Padres Zone at that depth to allow the rapid release of a large quantity of natural gas, primarily CH₄, which supersaturated the water in the well. This event caused the formation of a large bubble, which ballooned out of the well to the surface, displacing air in the location where the men were working, and thus causing asphyxiation, which resulted in the death of the three men. The judge accepted this interpretation.     

The Botanist Effect Revisited: Plant Species Richness, County Area, and Human Population Size in the United States

Abstract:  The "botanist effect" is thought to be the reason for higher plant species richness in areas where botanists are disproportionately present as an artefactual consequence of a more thorough sampling. We examined whether this was the case for U.S. counties. We collated the number of species of vascular plants, human population size, and the area of U.S. counties. Controlling for spatial autocorrelation and county area, plant species richness increased with human population size and density in counties with and without universities and/or botanical gardens, with no significant differences in the relation between the two subsets. This is consistent with previous findings and further evidence of a broad-scale positive correlation between species richness and human population presence, which has important consequences for the experience of nature by inhabitants of densely populated regions. Combined with the many reports of a negative correlation between the two variables at a local scale, the positive relation between plant species richness in U.S. counties and human population presence stresses the need for the conservation of seminatural areas in urbanized ecosystems and for the containment of urban and suburban sprawl.     

Algal “gardening” behavior by nereid polychaetes: Effects on soft-bottom community structure

Nereid polychaetes (Nereis vexillosa and Platynereis bicanaliculata) attach pieces of drift algae to their tube surfaces. The presence of permanent algal cover increases the predictability of the food supply for at least the herbivores (including the nereids) and the deposit feeders, and modulates the temperature and salinity stresses of the marine intertidal soft-bottom environment. However, it may affect the access of organisms to the oxygenated water layers above the sediment surface. This is true for polychaetes that live head downwards in vertical tubes. It is suggested that the attachment behavior of the nereid polychaetes increases the ability of the plant to colonize habitats both temporally and spatially.